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Agradecimentos: A.G.F. and M.H.F.B acknowledge support from the Brazilian Agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) under Finance Code 001 (A.G.F) and CAPES/PrInt Programme (M.H.F.B.). M.H.F.B. and M.A.P.L. acknowledge support from the Brazilian Agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). M.H.F.B. also acknowledges computational support from Professor Carlos M. de Carvalho at LFTC-DFis-UFPR and at LCPAD-UFPR. This research used the computing resources and assistance of the John David Rogers Computing Center (CCJDR) in the Institute of Physics "Gleb Wataghin," University of Campinas. This paper is also Honoring Prof. Vincent McKoy. For being very focused on ab initio calculations, he end up motivating our Brazilian community to explore several approximations that can proper describe the scattering process. Our applications of the SMC method with norm conserving pseudopotentials represent our effort of mixing ab initio calculation (electronic valence) with pseudo-potentials (electronic core). The present paper represents the first step to another mixture of strategies, the ab initio electronic excitation description with a pseudo (model) potential to represent the ionization process. During the review process of this manuscript by the Referees our dear friend and senior author of this manuscript, Professor Luiz Guimarães Ferreira (Guima), has passed away. Guima had a huge impact in our careers and in our lives Abstract: We propose a model potential for computing total ionization cross sections for atoms and molecules by electron impact. The potential is obtained by a fitting procedure using the Binary-Encounter-Bethe model cross sections as a starting point. We present total ionization cross section for hydrogen, carbon, nitrogen and oxygen atoms and for hydrogen, nitrogen, water, methane and benzene molecules. The results obtained with our model potential are compared with results obtained with the Binary-Encounter-Bethe model and with the first Born approximation, and agreement is quite good. Our results show that this potential could be used to account for the ionization channel in an electron-molecule collision calculation COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Agradecimentos: A.G.F. acknowledges support from Coordenaão de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001, and M.A.P.L. and R.F.C. acknowledge the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). This research used the computing resour- ces and assistance of the John David Rogers Computing Center (CCJDR) in the Institute of Physics "Gleb Wataghin," University of Campinas. M.J.B. acknowledges funding from the Australian Research Council through Grant # DP180101655 Abstract: Benzene is undoubtedly one of the most studied target molecules in electron scattering experiments and calculations. However, there is still a huge knowledge gap on the electronic excitation cross sections of this fundamental collision. Here, we report calculated differential and integral cross sections for elastic and electronic excitation, as well as total cross sections, for electron scattering by the benzene molecule, for impact energies in the 10-50 eV range. We have employed the Schwinger multichannel method, in two levels of approximation. By including extra diffuse functions in the second calculation, the role of higher lying Rydberg states in the multichannel coupling scheme was assessed. We found that such states have minor effects on the elastic and total cross sections. In contrast, the electronic excitation cross sections of the lower-lying bands decrease in magnitude when accounting for the higher Rydberg states, and this effect becomes more pronounced at lower impact energies. Our computed elastic cross sections are in quite good agreement with the available experimental data, whereas the comparison for the electronic excitation channels is still satisfactory. We also discuss the need for accurate excitation energies in order to properly compare theoretical and experimental electronic excitation cross sections COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Agradecimentos: M.A.P.L., M.T.d.N.V. (Grant ID No. 305672/2014-2), R.F.d.C. (Grant ID No. 313094/2017-9), J.C.R. (Grant ID No. 153377/2016-0), and M.H.F.B. (Grant ID No. 306581/2017-5) all acknowledge financial support from the Brazilian agency Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). These authors also wish to thank computational support from Centro de Computacao John David Rogers (CCJDR) at Universidade Estadual de Campinas (UNICAMP). F.K. acknowledges financial support from Fundacao de Amparoa Pesquisa do Estado de Sao Paulo (FAPESP), under Grant No. 2015/23792-5, while M.J.B. (Grant ID Nos. DP 160120787 and DP 180101655) acknowledges the Australian Research Council (ARC) for funding Abstract: We report the results of ab initio calculations for elastic scattering and also for excitation of individual electronic states of para-benzoquinone (pBQ) by the impact of low-energy electrons. The calculations for elastic scattering were performed with the Schwinger multichannel method implemented with pseudopotentials (SMCPP) in the static-exchange (SE) plus polarization (SEP) approximation for energies up to 50 eV. The assignments for the resonance spectrum obtained in this study are, in general, in good agreement with previous results available in the literature. For electronic excitation by electron impact, the SMCPP method with N energetically open electronic states (N-open), at either the static-exchange (N(open)ch-SE) or the static-exchange-plus-polarisation (N(open)ch-SEP) approximation, was employed to calculate the scattering amplitudes using a channel coupling scheme that ranges from the 1ch-SEP up to the 89ch-SE level of approximation, depending on the energy of interest. Integral cross sections (ICSs) and differential cross sections (DCSs) were obtained for incident electron energies lying between 15 eV and 50 eV. The study focuses on the influence of multichannel coupling effects for electronically inelastic processes, more specifically, on how the number of excited states included in the open-channel space impacts upon the convergence of the cross sections at intermediate and higher energies. In particular, we found that the magnitude of DCS and ICS results for electronic excitation decreases as more channels are included in the calculations. To the best of our knowledge, there are no other experimental or theoretical ICS or DCS results for excitation into individual electronic states of pBQ available in the literature between 15 and 50 eV against which we might compare the present calculations CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: This study has partially been supported by the Spanish Ministry MINECO (Project FIS-80440). F. F. S. acknowledges the Portuguese National Funding Agency FCT through Researcher Contract No. IF-FCT IF/00380/2014, and, together with P. L. V., the Research Grant No. UID/FIS/00068/2013. M. J. B. thanks the Australian Research Council for funding through grants DP160102787 and DP180101655. Finally, M. A. P. L., M. T. N. V. (Grant I. D. 305672/2014-9), R. F. C. (Grant I. D. 313094/2017-9) and M. H. F. B. all acknowledge financial support from the Brazilian agency Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). These authors also wish to thank computational support from Centro de Computacao John David Rogers (CCJDR) at Universidade Estadual de Campinas (UNICAMP). Finally, M. T. N. V. acknowledge Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) (Grant I. D. 2017/24145-9) for funding Abstract: Total electron scattering cross sections, from para-benzoquinone, for impact energies ranging between 1 to 200 eV, have been obtained by measuring the attenuation of a linear electron beam under magnetic confinement conditions. Random uncertainty limits on these values have been found to be within 5%. Systematic errors, due to the axial magnetic beam conditions in combination with the acceptance angle of the detector, have been evaluated by integrating our calculated independent atom model with the screening corrected additivity rule and interference term elastic differential cross sections over that detection acceptance angle. Our previous calculations and measurements on this molecule (Jones et al., J. Chem. Phys., 2018, 148, 124312 and J. Chem. Phys., 2018, 148, 204305), have been compiled and complemented with new elastic and inelastic scattering cross section calculations in order to obtain a comprehensive cross section data base, within the considered energy range, for modelling purposes. The self-consistency of the present data set has been evaluated by simulating the electron transport of 15 eV electrons in para-benzoquinone, and comparing those results with the observed transmitted intensity distribution CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: This study was partially supported by the Australian Research Council (ARC) through Grant No. DP160120787. It was also partially supported by the Spanish Ministry MINECO (Project No. FIS2016-80440), the COST Action (No. CM301), and the ITN-Marie Curie (No. ARGENT-608163) European Union programme. M.A.P.L., M.T.do.N.V. (Grant I.D. No. 305672/2014-2), R.F.da.C., and M.H.F.B. all thank CNPq for financial support, while F.K. (Grant I.D. No. 2015/23792-5) also thanks FAPESP for financial support. Finally, M.H.F.B. acknowledges computational support from Professor Carlos de Carvalho at LFTC-DFis-UFPR and at LCPAD-UFPR and from CENAPAD-SP Abstract: We report absolute experimental integral cross sections (ICSs) for the electron impact excitation of 6 bands (Bands 0-V) of unresolved electronic-states in para-benzoquinone, for incident electron energies between 20 and 40 eV. Absolute vibrational-excitation ICSs, for 3 composite vibrational bands (Bands I-III), are also reported in that same energy range. In addition, ICSs calculated within our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section (TCS) for electron-para-benzoquinone scattering. Where possible, those calculated IAM-SCAR+I ICSs are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, we also present results from our Schwinger multichannel method with pseudopotential (SMCPP) calculations. Here elastic ICSs and ICSs corresponding to the Bands 0-III of unresolved electronic-states are presented, with agreement between the SMCPP electronic-state ICSs and those from our measurements being in good qualitative accord. The energy range of our SMCPP computations is 16-50 eV. Using the binary-encounter-Bethe (BEB) approach, total ionization cross sections for this collision system were computed. Those total ionization cross sections were then added to our SMCPP ICS results, to derive SMCPP/BEB TCSs that are typically in very good accord with those from our IAM-SCAR+I approach CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: This work was partially supported by the Australian Research Council (ARC) through Grant No. DP160120787. It was also partially supported by the Spanish Ministry MINECO (Project No. FIS2016-80440), the COST Action (CM301), and ITN-Marie Curie (ARGENT-608163) European Union programmes. M.A.P.L., M.T.d.N.V. (Grant I.D. 305672/2014-2), R.F.d.C., and M.H.F.B. all acknowledge financial support from CNPq, while F.K.(Grant I.D. 2015/23792-5) also thank FAPESP for financial support. F.F.d.S. acknowledges the Portuguese National Funding Agency FCT-MCTES through a researcher position IF-FCT IF/00380/2014 and together with P.L.-V. the research Grant No. UID/FIS/00068/2013 Abstract: Angle resolved electron energy loss spectra (EELS) for para-benzoquinone (C6H4O2) have been recorded for incident electron energies of 20, 30, and 40 eV. Measured differential cross sections (DCSs) for electronic band features, composed of a combination of energetically unresolved electronic states, are subsequently derived from those EELS. Where possible, the obtained DCSs are compared with those calculated using the Schwinger multichannel method with pseudopotentials. These calculations were performed using a minimum orbital basis single configuration interaction framework at the static exchange plus polarisation level. Here, quite reasonable agreement between the experimental cross sections and the theoretical cross sections for the summation of unresolved states was observed CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: F.B. Nunes acknowledges support from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). S. d'A. Sanchez and M.H.F. Bettega acknowledge support from CNPq. M.H.F.B. acknowledges support from Finep (under project CT-Infra). D.F. Pastega aknowledges support from CAPES. M.A.P. Lima and M.T.doN. Varella acknowledge support from CNPq and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP). The authors also acknowledge computational support from Professor Carlos M. de Carvalho at LFTC-DFis-UFPR and at LCPAD-UFPR and from CENAPAD-SP Abstract: We employed elastic scattering calculations, performed in the static exchange approximation, to investigate the pi* ransient anion states of cytosine, guanine and the cytosine-guanine pair. Our results for the isolated monomers, also obtained in the static-exchange plus polarization approximation, are in good agreement with the available calculations and electron transmission data. Virtual orbital analysis for the lower-lying pi* anion states, with pure shape resonance character, indicates that electron attachment to the cytosine-guanine pair gives rise to resonances located on either monomer (the orbitals do not delocalize over the pair). The pi* shape resonances of the pair localized on the cytosine unit have lower energies in comparison with those of the isolated base, with the opposite trend for the guanine unit. The underlying mechanism would be the net positive charge transfer to the cytosine unit, as the guanine monomer acts as a proton donor in two out of the three hydrogen bonds formed in the pair. Even though the calculations were performed in the static-exchange approximation (due to the size of the system), the conclusions drawn were also corroborated by empirical estimates of the vertical attachment energies. The results for the cytosine-uanine pair are compared to those previously obtained for the formic acid-formamide complex, having two hydrogen bonds with opposite donor/acceptor characters and negligible charge transfer CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FINANCIADORA DE ESTUDOS E PROJETOS - FINEP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: This study has been partially supported by the Spanish Ministry MINECO (Project No. FIS2016-80440), COST (CM301 Action) and ITN-Marie Curie (No. ARGENT-608163) European Union programmes. M.A.P.L., M.T.do.N.V. (Grant No. 305672/2014-2), R.F.C., and M.H.F.B. all acknowledge financial support from CNPq, while F.K. (Grant No. 2015/23792-5) and M.T.do.N.V. (Grant No. 2014/10012-9) also thank FAPESP for financial support. Finally, M.J.B. (No. DP160102787) and R.D.W. acknowledge the Australian Research Council for funding Abstract: We report on theoretical elastic and experimental vibrational-excitation differential cross sections (DCSs) for electron scattering from para-benzoquinone (C6H4O2), in the intermediate energy range 15-50 eV. The calculations were conducted with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that also now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N-open) at the static-exchange-plus-polarisation (N(open)ch-SEP) level was used to calculate the scattering amplitudes using a channel coupling scheme that ranges from 1ch-SE up to the 89ch-SEP level of approximation. We found that in going from the 38ch-SEP to the 89ch-SEP, at all energies considered here, the elastic DCSs did not change significantly in terms of both their shapes and magnitudes. This is a good indication that our SMCPP 89ch-SEP elastic DCSs are converged with respect to the multichannel coupling effect for the investigated intermediate energies. While agreement between our IAM-SCAR+I and SMCPP 89ch-SEP computations improves as the incident electron energy increases from 15 eV, overall the level of accord is only marginal. This is particularly true at middle scattering angles, suggesting that our SCAR and interference corrections are failing somewhat for this molecule below 50 eV. We also report experimental DCS results, using a crossed-beam apparatus, for excitation of some of the unresolved ("hybrid") vibrational quanta (bands I-III) of para-benzoquinone. Those data were derived from electron energy loss spectra that were measured over a scattered electron angular range of 10 degrees-90 degrees and put on an absolute scale using our elastic SMCPP 89ch-SEP DCS results. The energy resolution of our measurements was similar to 80 meV, which is why, at least in part, the observed vibrational features were only partially resolved. To the best of our knowledge, there are no other experimental or theoretical vibrational excitation results against which we might compare the present measurements CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: G.M.A., D.T.M, M.M. and M.A.P.L acknowledge support from the Brazilian agency "Conselho Nacional de Desenvolvimento Científico e Tecnológico" (CNPq). D.Q.A., L.F.M.C, and S.I.C.G acknowledge support from the Brazilian agency "Coordenação de Aperfeiçoamento de Pessoal de Nível Superior" (CAPES), and L.F.C.F acknowledges support from the Brazilian state of São Paulo agency "Fundação de Amparo à Pesquisa do Estado de São Paulo" (FAPESP). The authors thank Amanda A. R. Lima for drawing the inspiring figure 2. The authors are grateful to Profs. Michael Brunger, Prof. Amir Caldeira and Prof. José A. Roversi for their critical reading of the manuscript and constructive comments and suggestions. The authors also thank for critical reading of this manuscript, the following group of people of the aimed public target: Paulo S. P. Lima (Mechanical Engineer), Martín E. Navarro Maldonado (Chemical Engineer), and Luis Quesada (Professor of Computer Science and Informatics) Abstract: Can you pick a complex subject in quantum mechanics and discuss it with a minimum number of equations, in a simplified form that the general scientific public could understand? This was a question presented to graduate students of the one-year Quantum Mechanics course based on the text book Modern Quantum Mechanics by J. J. Sakurai and Jim Napolitano, at the State University of Campinas (UNICAMP), Brazil. The first seven authors of this paper are graduate students (alphabetical order) that accepted to try it. The chosen subject was "delocalized quantum states", and it will be discussed using colloquial terms like quantum ghosts, spooky action, splitting beings and invisibility cloak Resumo: Pode-se escolher um topico complexo em mecanica quantica e discuti-lo com um numero minimo de equações, e de forma simplificada para que um publico com apenas conhecimento basico em fisica possa entender? Essa foi a pergunta apresentada aos alunos de pos-graduação das disciplinas de um ano de Mecanica Quantica I e II da Universidade Estadual de Campinas (UNICAMP), baseadas no livro "Quantum Mechanics" de J. J. Sakurai e Jim Napolitano. Os primeiros sete autores desse artigosão os alunos de pos-graduação (em ordem alfabetica) que aceitaram o desafio. O topico escolhido foi estados quanticos delocalizados, e sera discutido utilizando termos coloquiais como fantasmas quanticos, ações fantasmagoricas, entidades divididas e capa de invisibilidade CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: D.B.J. thanks the Australian Research Council (ARC) for financial support provided through a Discovery Early Career Research Award, while M.J.B. also thanks the ARC for their support. M.J.B. acknowledges the Brazilian agency CNPq for his "Special Visiting Professor" position at the Federal University of Juiz de Fora. G.G. acknowledges partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230) and the European Union COST Action No. CM1301 (CELINA). Finally R.F.C., M.T.doN.V, M.H.F.B, and M.A.P.L. also acknowledge support from CNPq, while M.T.doN.V. thanks FAPESP Abstract: We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20-250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron-furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: R.F.C.N. thanks CNPq (Brazil) and the Science Without Borders Programme for opportunities to study abroad. D.B.J. thanks the Australian Research Council (ARC) for financial support provided through a Discovery Early Career Research Award, while M.J.B. also thanks the ARC for their support. M.J.B. and M.C.A.L. acknowledge the Brazilian agencies CNPq and FAPEMIG. P.L.-V. acknowledges the Portuguese Foundation for Science and Technology (FCT-MEC) through Grant Nos. PTDC/FIS-ATO/1832/2012 and UIO/FIS/00068/2013. G.G. acknowledges partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230) and the European Union COST Action No. CM1301 (CELINA). Finally, R.F.d.C., M.T.d.N.V., M.H.F.B., and M.A.P.L. acknowledge support from the Brazilian agency CNPq and M.T.d.N.V. also thanks FAPESP Abstract: We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (C5H4O2). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C5H4O2. The measurements were carried out at energies in the range 20-40 eV, and for scattered-electron angles between 10 degrees and 90 degrees. The energy resolution of those experiments was typically similar to 80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6-50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIG FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: The authors acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). R.F. da C., M.T. do N.V., J.A.F. and M.A.P.L. acknowledge support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). M.A.R. acknowledges support from the Brazilian Agency Coordenação de Aperfeiçoamento de Pessoal de Nível Superior under the grant Capes/ITA 005-2014. M.J.B. acknowledges the Australian Research Council (ARC) for some financial support and also thanks CNPq for his Special Visiting Professor award at the Federal University of Juiz de Fora Abstract: Recent data obtained for electron scattering by biomass molecular fragments, indicated that low-energy resonances may have an important role in the de-lignification of biomass through a plasma pretreatment. To support these findings, we present new experimental evidence of the predicted dissociation pathways on plasma treatment of biomass. An important question is how accurate must the experimental and/or the theoretical data be in order to indicate that plasma modelings can be really useful in understanding plasma applications? In this paper, we initiate a discussion on the role of data accuracy of experimental and theoretical electron-molecule scattering cross sections in plasma modeling. First we review technological motivations for carrying out electron-molecule scattering studies. Then we point out the theoretical and experimental limitations that prevent us from obtaining more accurate cross sections. We present a few examples involving biomass molecular fragments, to illustrate theoretical inaccuracies on: resonances positions and widths, electronic excitation, superelastic cross sections from metastable states and due to multichannel effects on the momentum transfer cross sections. On the experimental side we briefly describe challenges in making absolute cross sections measurements with biomass species and radicals. And finally, through a simulation of a N-2 plasma, we illustrate the impact on the simulation due to inaccuracies on the resonance positions and widths and due to multichannel effects on the momentum transfer cross sections CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

Agradecimentos: This work was supported by the Brazilian, Australian, and Spanish governmental funding agencies (CNPq, CAPES, and ARC). R.F.d.C., M.C.A.L., M.H.F.B., M.T.d.N.V., and M.A.P.L. acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). M.T.d.N.V. acknowledges support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). D.B.J. thanks the Australian Research Council (ARC) for financial support provided through a Discovery Early Career Researcher Award. M.J.B. thanks the ARC for some financial support and also thanks CNPq for his "Special Visiting Professor" award at the Federal University of Juiz de Fora. G.G. thanks the Spanish Ministerio de Economia y Competitividad under Project No. FIS2012-31230 and the European Union COST Action No. CM1301 for funding. Computational support from CCJDR-IFGW-UNICAMP, where the present SMCPP calculations were performed, is also acknowledged Abstract: We report on integral-, momentum transfer-and differential cross sections for elastic and electronically inelastic electron collisions with furfural (C5H4O2). The calculations were performed with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N-open) at either the static-exchange (N-open ch-SE) or the static-exchange-plus-polarisation (N-open ch-SEP) approximation was employed to calculate the scattering amplitudes at impact energies lying between 5 eV and 50 eV, using a channel coupling scheme that ranges from the 1ch-SEP up to the 63ch-SE level of approximation depending on the energy considered. For elastic scattering, we found very good overall agreement at higher energies among our SMCPP cross sections, our IAM-SCAR+I cross sections and the experimental data for furan (a molecule that differs from furfural only by the substitution of a hydrogen atom in furan with an aldehyde functional group). This is a good indication that our elastic cross sections are converged with respect to the multichannel coupling effect for most of the investigated intermediate energies. However, although the present application represents the most sophisticated calculation performed with the SMCPP method thus far, the inelastic cross sections, even for the low lying energy states, are still not completely converged for intermediate and higher energies. We discuss possible reasons leading to this discrepancy and point out what further steps need to be undertaken in order to improve the agreement between the calculated and measured cross sections CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: This research was supported by the Australian and Brazilian Governmental Funding Agencies (ARC, CNPq and CAPES). D.B.J. thanks the ARC for a Discovery Early Career Researcher Award. R.F.C.N. acknowledges CNPq and Flinders University for financial assistance, while M.J.B. thanks CNPq for his "Special Visiting Professor" award. E.M.O., R.F.C., M.T.N.V., and M.A.P.L. acknowledge financial support from FAPESP, while R.F.C., M.T.N.V., M.H.F.B., M.C.A.L., and M.A.P.L. acknowledge financial support from CNPq. K.L.N. also thanks CNPq for an "Attracting Young Talent" grant under the Science Without Borders program Abstract: We report differential cross section results from an experimental investigation into the electron impact excitation of a number of the low-lying composite (unresolved) vibrational modes in phenol (C6H5OH). The measurements were carried out at incident electron energies in the range 15-40 eV and for scattered-electron angles in the range 10-90 degrees. The energy resolution of those measurements was typically similar to 80 meV. Calculations, using the GAMESS code, were also undertaken with a B3LYP/aug-cc-pVDZ level model chemistry, in order to enable us to assign vibrational modes to the features observed in our energy loss spectra. To the best of our knowledge, the present cross sections are the first to be reported for vibrational excitation of the C6H5OH molecule by electron impact CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: The authors acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). R.F.da.C., M.T.do.N.V., E.M.de.O and M.A.P.L. acknowledge support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). The present SMCPP calculations were performed at IFGW-UNICAMP, LCPAD-UFPR, and LFTC-DFis-UFPR. M.H.F.B. acknowledges computational support from Professor Carlos de Carvalho. D.B.J. and M.J.B. acknowledge the Australian Research Council (ARC) for some financial support, in particular D.B.J. thanks the ARC for a Discovery Early Career Researcher Award. M.J.B. also thanks CNPq for his Special Visiting Professor award at the Federal University of Juiz de Fora. P.L.-V. acknowledges support from the Portuguese Foundation for Science and Technology, FCT-MEC though research Grant Nos. PEst-OE/FIS/UI0068/2014 and PTDC/FIS-ATO/1832/2012 Abstract: We report theoretical and experimental total cross sections for electron scattering by phenol (C6H5OH). The experimental data were obtained with an apparatus based in Madrid and the calculated cross sections with two different methodologies, the independent atom method with screening corrected additivity rule (IAM-SCAR), and the Schwinger multichannel method with pseudopotentials (SMCPP). The SMCPP method in the Nopen-channel coupling scheme, at the static-exchange-plus-polarization approximation, is employed to calculate the scattering amplitudes at impact energies ranging from 5.0 eV to 50 eV. We discuss the multichannel coupling effects in the calculated cross sections, in particular how the number of excited states included in the open-channel space impacts upon the convergence of the elastic cross sections at higher collision energies. The IAM-SCAR approach was also used to obtain the elastic differential cross sections (DCSs) and for correcting the experimental total cross sections for the so-called forward angle scattering effect. We found a very good agreement between our SMCPP theoretical differential, integral, and momentum transfer cross sections and experimental data for benzene (a molecule differing from phenol by replacing a hydrogen atom in benzene with a hydroxyl group). Although some discrepancies were found for lower energies, the agreement between the SMCPP data and the DCSs obtained with the IAM-SCAR method improves, as expected, as the impact energy increases. We also have a good agreement among the present SMCPP calculated total cross section (which includes elastic, 32 inelastic electronic excitation processes and ionization contributions, the latter estimated with the binary-encounter-Bethe model), the IAM-SCAR total cross section, and the experimental data when the latter is corrected for the forward angle scattering effect [Fuss et al., Phys. Rev. A 88, 042702 (2013)] CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: This research was supported by the Australian and Brazilian Governmental Funding Agencies (ARC, CNPq and CAPES). D.B.J. thanks the ARC for a Discovery Early Career Researcher Award. R.F.C.N. acknowledges CNPq and Flinders University for financial assistance, while H.V.D. acknowledges CAPES and Flinders. M.J.B. thanks CNPq for his "Special Visiting Professor" award. E.M.O., R.F.C., M.T.N.V., and M.A.P.L. acknowledge financial support from FAPESP, while R.F.C., M.T.N.V., M.H.F.B., M.C.A.L., and M.A.P.L. acknowledge financial support from CNPq. K.L.N. thanks CNPq for an "Attracting Young Talent Grant" under the "Science Without Borders" program. G.G. acknowledges financial support from MINECO (FIS2012-31230) and COST (MP1002, CM1301) Abstract: We report results from a joint theoretical and experimental investigation into electron scattering from the important organic species phenol (C6H5OH). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of C6H5OH. The measurements were carried out at energies in the range 15-40 eV, and for scattered-electron angles between 10 and 90. The energy resolution of those experiments was typically ~80 meV. Corresponding Schwinger multichannel method with pseudo-potentials calculations, with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were conducted at the static exchange plus polarisation (SEP)-level using a minimum orbital basis for single configuration interaction (MOBSCI) approach. Agreement between the measured and calculated DCSs was typically fair, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOBSCI CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: D.F.P. acknowledges support from Brazilian Agency Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES). R. F. da C., M. A. P. L. and M. H. F. B. acknowledge support from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). R. F. da C. and M. A. P. L. also acknowledge support from Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP). M. H. F. B. also acknowledges support from FINEP (under project CT-Infra). The authors acknowledge computational support from Professor Carlos M. de Carvalho at LFTC-DFis-UFPR and at LCPAD-UFPR, and from CENAPAD-SP Abstract: We present integral, differential and momentum transfer cross sections for elastic scattering of low-energy electrons by boron trifluoride molecules. The cross sections were obtained with the Schwinger multichannel method implemented with pseudopotentials. The calculations were performed in the static-exchange and in the static-exchange-polarization approximations for energies from 0.1 to 10 eV. Our results indicate that BF3 has a shape resonance in the B (2) symmetry located at around 3.5 eV, in agreement with the experimental measurements of 3.8 eV, 3.54 eV and of 3.6 eV reported by [M. Tronc et al., J. Phys. B 15, L253 (1982)], by [J.A. Tossell et al., Int. J. Quantum Chem. 29, 1117 (1986)] and by [C. Szmytkowski et al., J. Chem. Phys. 121, 1790 (2004)] respectively. We also report a Ramsauer-Townsend minimum at around 0.7 eV, in conformity with the observations of [S.R. Hunter et al., J. Appl. Phys. 65, 1858 (1989); Z. NikitoviA double dagger et al., Acta Phys. Polon. A 117, 748 (2010)], and [P.X. Hien et al., J. Phys. Soc. Jpn 82, 034301 (2013)]. Our elastic integral cross section is compared with calculated elastic cross sections of [J.A. Tossell et al., Int. J. Quantum Chem. 29, 1117 (1986)] and of [M. RadmiloviA double dagger-RadjenoviA double dagger et al., Publ. Astron. Obs. Belgrade 84, 57 (2008)] and with the experimental total cross section data of [C. Szmytkowski et al., J. Chem. Phys. 121, 1790 (2004)]. Although all these studies reported the presence of the shape resonance, there are some discrepancies in the magnitude and shape among the cross sections COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Aberto

Agradecimentos: E.M. de O., M. T. do N.V. and M. A. P. L. acknowledge support from Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP). M. T. do N.V., M. H. F. B and M. A. P. L. acknowledge support from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). M. H. F. B. acknowledges support from FINEP (under project CT-Infra) and computational support from Prof. Carlos de Carvalho. The present calculations were performed at CENAPAD/SP, IFGW/UNICAMP, LFTC-DFis/UFPR, LCPAD/UFPR and CTBE/CNPEM Abstract: We report elastic integral (ICS), differential (DCS) and momentum transfer cross sections (MTCS) for low-energy electron scattering by n-pentanol alcohol in the gas phase. The Schwinger multichannel method implemented with pseudopotentials was employed in the calculations. The DCSs were computed for energies from 1 to 50 eV and the ICS and MTCS from 1 to 100 eV. Due to the significant value of the electric dipole moment, the DCSs are dominated by strong forward scattering. Despite this fact, the DCS around 10 eV displays a behavior related to a f-wave scattering pattern at intermediate angles which may be associated with shape resonances. This result is consistent with the ICS and the MTCS since they show a pronounced peak near this energy. For energies below 1 eV, the MTCS obtained in the static-exchange plus polarization approximation does not increase, as expected for polar molecules, suggesting that a Ramsauer-Townsend minimum could be present. This finding motivated us to revisit the previously studied methanol, ethanol, n-propanol and n-butanol molecules and to perform new calculations for impact energies below 1 eV (not addressed before). With the inclusion of polarization effects, the MTCS for the five alcohols suggest a Ramsauer-Townsend minimum coming from the negative to the positive scattering energies. To the best of our knowledge, there are neither experimental nor calculated cross sections for comparison with the present results FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Aberto

Agradecimentos: This research was supported by the Australian and Brazilian Governmental Funding Agencies (ARC, CNPq, and CAPES). D.B.J. thanks the ARC for a Discovery Early Career Researcher Award. G. B. S. and H. V. D. acknowledge financial support from CAPES and Flinders University during their stay in Australia. R.F.C.N. acknowledges CNPq and Flinders for assistance, while M.J.B. thanks CNPq for his "Special Visiting Professor" award. R.F.C.N. and H. V. D. thank the Science without Borders scheme for their opportunity to study in Australia. E.M.O., R. F. C., M.T.N.V., and M. A. P. L. acknowledge financial support from FAPESP. R. F. C., M.T.N.V., M. H. F. B., M. C. A. L., and M. A. P. L. acknowledge financial support from CNPq. We thank Professor Lee and Professor Homem for providing numerical tables of their calculations Abstract: We present experimental electron-energy loss spectra (EELS) that were measured at impact energies of 20 and 30 eV and at angles of 90 degrees and 10 degrees, respectively, with energy resolution similar to 70 meV. EELS for 250 eV incident electron energy over a range of angles between 3 degrees and 50 degrees have also been measured at a moderate energy resolution (similar to 0.9 eV). The latter spectra were used to derive differential cross sections and generalised oscillator strengths (GOS) for the dipole-allowed electronic transitions, through normalization to data for elastic electron scattering from benzene. Theoretical calculations were performed using time-dependent density functional theory and single-excitation configuration interaction methods. These calculations were used to assign the experimentally measured spectra. Calculated optical oscillator strengths were also compared to those derived from the GOS data. This provides the first investigation of all singlet and triplet excited electronic states of phenol up to the first ionization potential CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: The present calculations were performed at IFGW-UNICAMP, LCPAD-UFPR, and LFTC-DFis- UFPR. M.H.F.B. acknowledges computational support from Prof. Carlos de Carvalho. The authors acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). R.F.daC., M.T.doN.V., and E.M.O. acknowledge support from Sao Paulo Research Foundation Abstract: We report integral and differential cross sections for elastic and electronically inelastic (X1Ag?a3B1u) electron scattering by ethylene. The Schwinger multichannel method with pseudopotentials in the Nopen-channel-coupling scheme at the static-exchange-plus-polarization approximation is employed to calculate the scattering amplitudes at impact energies ranging from 5.7 to 50 eV. We discuss the multichannel-coupling effects in the calculated cross sections, in particular, how the number of excited states included in the open-channel space impacts the convergence of the elastic and the (X1Ag?a3B1u) excitation cross sections at higher collision energies. We found good agreement between the present calculated total cross section (which includes elastic, inelastic, and ionization contributions, the latter estimated with the binary-encounter-Bethe model) and the experimental data CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: The authors acknowledge support from the Brazilian agencies FAPESP and CNPq. This work was supported by the CNPq/NSF Cooperative Research Program and by the FAPESP Bioenergy Program (BIOEN 08/58034-0). The present calculations were performed at CENAPAD/SP, CTBE/CNPEM, IFGW/UNICAMP, LFTC-DFis-UFPR, and LCPAD-UFPR. M. H. F. B. acknowledges computational support from Professor C. de Carvalho Abstract: We report on the shape resonance spectra of phenol-water clusters, as obtained from elastic electron scattering calculations. Our results, along with virtual orbital analysis, indicate that the well-known indirect mechanism for hydrogen elimination in the gas phase is significantly impacted on by microsolvation, due to the competition between vibronic couplings on the solute and solvent molecules. This fact suggests how relevant the solvation effects could be for the electron-driven damage of biomolecules and the biomass delignification [E. M. de Oliveira et al., Phys. Rev. A 86, 020701(R) (2012)]. We also discuss microsolvation signatures in the differential cross sections that could help to identify the solvated complexes and access the composition of gaseous admixtures of these species CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: The authors acknowledge support from the Brazilian agencies FAPESP, CNPq and Fundacao Araucaria. This work was supported by the CNPq/NSF Cooperative Research Program and by the FAPESP Bioenergy Program (project 08/58034-0). The present calculations were performed at CENAPAD/SP, IFGW/UNICAMP and CTBE/CNPEM Abstract: We report elastic integral, differential and momentum transfer cross sections for low-energy electron scattering by the cellulose components beta-D-glucose and cellobiose (beta(1 -> 4) linked glucose dimer), and the hemicellulose component beta-D-xylose. For comparison with the b forms, we also obtain results for the amylose subunits alpha-D-glucose and maltose (alpha(1 -> 4) linked glucose dimer). The integral cross sections show double peaked broad structures between 8 eV and 20 eV similar to previously reported results for tetrahydrofuran and 2-deoxyribose, suggesting a general feature of molecules containing furanose and pyranose rings. These broad structures would reflect OH, CO and/or CC sigma* resonances, where inspection of low-lying virtual orbitals suggests significant contribution from sigma(OH)* anion states. Though we do not examine dissociation pathways, these anion states could play a role in dissociative electron attachment mechanisms, in case they were coupled to the long-lived pi* anions found in lignin subunits [de Oliveira et al., Phys. Rev. A, 2012, 86, 020701(R)]. Altogether, the resonance spectra of lignin, cellulose and hemicellulose components establish a physical-chemical basis for electron-induced biomass pretreatment that could be applied to biofuel production FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FA FUNDAÇÃO DE AMPARO À PESQUISA E INOVAÇÃO DO ESTADO DE SANTA CATARINA - FAPESC Fechado

Agradecimentos: MTdNV and MAPL acknowledge support from CNPq and FAPESP. The calculations were performed using resources from the Laboratory of Advanced Scientific Computation (LCCA), University of Sao Paulo. Sd'AS and MHFB acknowledge support from CNPq, FINEP (under project CT-Infra) and from Fundacao Araucaria and computational support from Professor Carlos M de Carvalho at LFTC-DFis-UFPR and at LCPAD-UFPR. The authors also acknowledge computational support from CENAPAD-SP. This work was conducted under a Memorandum of Understanding between the University of Trento and the Flinders University node of the Australian Research Council (ARC) Centre of Excellence for Antimatter-Matter Studies. We therefore also acknowledge the ARC for financial support. The authors finally acknowledge Darryl Jones for his help in estimating the effect of the convolution of our calculated cross sections with our experimental beam energy distribution Abstract: We report experimental total cross sections (TCSs) and calculated elastic integral cross sections (ICSs) for positron collisions with iodomethane (methyl iodide, CH3I). The experimental TCSs were obtained with a linear transmission technique, for energies from 0.1 up to 50 eV. The present TCS data agree well with those previously reported (Kimura et al 2001 J. Chem. Phys. 115 7442) at higher energies (above 7 eV), but significant discrepancies are found at the lower energies. The present ICS computations were performed with the Schwinger multichannel method (SMC) and the Born dipole approximation in the incident energy range from 0.1 eV up to 10 eV. Iodomethane poses a great challenge to theoretical descriptions of the collisions dynamics. In addition to the neglect of inelastic channels, the main difficulty found in the SMC approach is related to numerical limitations that prevent a thorough description of correlation-polarization effects. Although our ICS calculations do not compare well with the present TCS data, the results are encouraging, as iodomethane would challenge all the presently available computational approaches CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FA FUNDAÇÃO DE AMPARO À PESQUISA E INOVAÇÃO DO ESTADO DE SANTA CATARINA - FAPESC Fechado

Agradecimentos: The experimental work was conducted under a Memorandum of Understanding between the University of Trento and the Flinders University node of the Australian Research Council (ARC) Centre of Excellence for Antimatter-Matter Studies. G.G. and F.B. would like to acknowledge the Spanish Ministerio de Economía y Productividad (Project No. FIS2009-10245) and they and M.J.B. would like to acknowledge the European Science Foundation (COST Action MP1002-Nano-IBCT) for financial support. M.H.F.B., S.d’A.S., M.T.do N.V., and M.A.P.L. would like to thank the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). M.H.F.B. acknowledges support from FINEP (under Project No. CT-Infra). S.d’A.S. also thanks the Fundação Araucária. M.T.do N.V., and M.A.P.L. acknowledge support from FAPESP. M.H.F.B. and S.d’A.S. would like to thank Professor Carlos M. de Carvalho at LFTC-DFis-UFPR and LCPAD-UFPR for computational support. The Brazilian authors also acknowledge computational support from CENAPAD-SP. Finally, the authors would like to thank Christof Janssen for bringing the issue of the thermal transpiration correction to their attention Abstract: We present cross-section results from an experimental and theoretical study on positron scattering from nitrous oxide. Total cross sections (TCSs) have been measured at incident energies between 0.1 and 70 eV with a linear-transmission-based positron spectrometer. Elastic differential and integral cross sections, as well as inelastic integral cross sections and TCSs, have been computed with two different theoretical approaches: the independent atom model with screening-corrected additivity rule (IAM-SCAR), at energies in the 1- to 1000-eV range, and the Schwinger multichannel method at energies between 0.1 and 10 eV. Note that the latter method specifically reports cross sections for the elastic channel. We find good qualitative agreement between the theories and the TCS experiment at all common energies. That level of accord is found to also become quantitative above the ionization energy of nitrous oxide. Electron-impact TCSs calculated with the IAM-SCAR approach are also presented and compared to the existing results in order to uncover any similarities or differences in the scattering processes between these two leptons and nitrous oxide CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FINANCIADORA DE ESTUDOS E PROJETOS - FINEP FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FA FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: This work was funded through a collaborative program by the U.S. National Science Foundation under Grants No. PHY 0653452 and No. PHY 0653396 and by the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under Project No. 490415/2007-5. R.F.d.C., M.H.F.B., M.C.A.L. and M.A.P.L. acknowledge additional support from CNPq and from the Brazilian agencies Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), the Paraná state agency Fundação Araucária, Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), and Financiadora de Estudos e Projetos (FINEP) under Project No. CT-Infra 1. M.H.F.B. further acknowledges computational support from Professor Carlos M. de Carvalho at DF-UFPR. Computational support from Centro de Computação John David Rogers (CCJDR) and from Centro Nacional de Processamento de Alto Desempenho em São Paulo (CENAPAD), where the calculations in Brazil were performed, is gratefully acknowledged Abstract: Experiments and ab initio calculations of the differential and integral cross sections for the electronic excitation from the ground state (1)A(1) to the B-3(2) and (3)A(1) states of gas-phase furan molecules by low-energy electron impact were performed. Experimental differential cross sections were measured at incident electron energies between 5 and 15 eV and for scattering angles from 10 degrees to 130 degrees. The calculated cross sections were obtained using the Schwinger multichannel method implemented with pseudopotentials. The influence of channel-coupling and polarization effects is investigated through the comparison between three different models of scattering calculations, each one considering a distinct channel-coupling scheme. The comparison of experimental and calculated cross sections for electronically inelastic electron scattering by C4H4O molecules is found to be mostly reasonable. The existing discrepancies in this combined theoretical and experimental study help to illustrate difficulties in readily establishing reliable electronic excitation cross sections of polyatomic molecules by low-energy electrons CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIG FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Aberto

Agradecimentos: The authors acknowledge support from the Brazilian agencies FAPESP, CNPq, and Fundação Araucária. This work was supported by the CNPq/NSF Cooperative Research Program and by the FAPESP Bioenergy Program (BIOEN 08/58034-0). The present calculations were performed at CENAPAD/SP, CTBE/CNPEM, IFGW/UNICAMP and LCPAD-UFPR. The authors thank Professor J. Amorim for helpful comments on atmospheric-pressure plasmas Abstract: We report integral cross sections for elastic electron scattering by the lignin subunits phenol, guaiacol, and p-coumaryl alcohol. Our calculations employed the Schwinger multichannel method with pseudopotentials and indicate three to four pi* shape resonances for each of these systems, suggesting that low-energy electrons could efficiently transfer energy into the lignin matrix. We also discuss dissociation mechanisms based on the calculated cross sections, available experimental data, virtual orbital analysis, and the knowledge on electron interactions with biomolecules. Our results point out a physical-chemical basis for electron-driven biomass delignification. The latter would be an essential step for efficient biofuel production from lignocellulosic materials FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR Aberto

Agradecimentos: S.d’A.S., M.H.F.B., M.T.doN.V., and M.A.P.L. acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). S.d’A.S. acknowledges further support from Fundação Araucária, while M.H.F.B. also acknowledges support from FINEP (under Project No. CT-Infra). M.T.doN.V. and M.A.P.L. acknowledge support from FAPESP. S.d'A.S. and M.H.F.B. also acknowledge computational support from Professor Carlos M. de Carvalho at DFis-UFPR and LCPAD-UFPR. The authors acknowledge additional computational support from CENAPAD–SP. This work was also supported under a Memorandum of Understanding between the University of Trento and the Flinders University node of the ARC Centre of Excellence for Antimatter-Matter Studies. L.C. thanks CAMS for some financial support during his stay in Australia Abstract: We report on measurements of total cross sections for positron scattering from the fundamental organic molecule methane (CH4). The energy range of these measurements was 0.1-50 eV, whereas the energy resolution was similar to 100 meV when our Ni moderator was used and similar to 260 meV when the W moderator was employed. To assist us in interpreting these data, Schwinger multichannel calculations were performed at both static and static plus polarization levels of approximation for elastic positron scattering from 0.001 to 10 eV. These calculations are found to be in quite good qualitative agreement with our measured data, and they clearly educe the crucial role played by the target polarization in the low energy positron-CH4 scattering dynamics CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FINANCIADORA DE ESTUDOS E PROJETOS - FINEP FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

Agradecimentos: S.d'A.S. and M.H.F.B. acknowledge support from CNPq, FINEP (under project CT-Infra) and from Fundação Araucária. M.T.doN.V. and M.A.P.L. acknowledge support from CNPq and FAPESP. S.d'A.S. and M.H.F.B acknowledge computational support from Carlos M. de Carvalho at DFis-UFPR and at LCPAD-UFPR. The authors also acknowledge computational support from CENAPAD-SP. This work was also conducted under a Memorandum of Understanding between the University of Trento and the Flinders University node of the Australian Research Council Centre for Antimatter-Matter Studies Abstract: We present experimental and theoretical cross sections for positron collisions with ethene molecules. The experimental total cross sections (TCSs) were obtained with a linear transmission technique, for energies from 0.1 eV up to 70 eV. The calculations employed the Schwinger multichannel method and were performed in the static plus polarization approximation for energies up to 10 eV. Our calculated elastic cross sections indicate a Ramsauer-Townsend minimum around 2.8 eV and a virtual state, in agreement with previous calculations by da Silva et al. [Phys. Rev. Lett. 77, 1028 (1996)]. We found reasonable agreement between the calculated elastic integral cross section and the measured total cross section below the positronium formation threshold. The present results are also in quite good agreement with available theoretical and experimental data, although for the experiments this is only true for TCSs above about 7 eV CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FINANCIADORA DE ESTUDOS E PROJETOS - FINEP FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

We present a theoretical investigation on positron scattering by N2O. Elastic differential and integral cross sections at both the static and static plus correlation-polarization levels of approximation are calculated and reported in the 0.1-100 eV. Calculations were performed using two theoretical methods, namely, the Schwinger multichannel method and the method of continued fractions. Also, two different schemes were used to treat correlation-polarization effects. The comparison between our calculated results and the existing experimental data is encouraging CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Aberto

The Schwinger multichannel method is applied to study the low-energy electron-impact excitation of molecular nitrogen. The scattering amplitudes are obtained within the minimal orbital basis for single configuration interactions (MOBSCI) level of approximation, for impact energies from near threshold up to 30 eV. Through the use of the MOBSCI strategy we have performed a close-coupling calculation for up to nine states, including the ground state and all singlet and triplet states resulting from the pi(u)->pi(g) transitions. Integral and differential cross sections for the X (1)Sigma(+)(g)-> A (3)Sigma(+)(u), W (3)Delta(u), B-' (3)Sigma(-)(u), a(') (1)Sigma(-)(u), and w (1)Delta(u) electronic transitions are presented and compared with available experimental data and also with other theoretical results FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Aberto

Agradecimentos: M.A.P.L. acknowledges support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The calculations presented here were partly performed at Centro Nacional de Processamento de Alto Desempenho (CENAPAD-SP) Abstract: We report vibrational excitation (nu(i)=0 ->nu(f)=1) and total cross sections for positron scattering by H-2. The Feshbach projection operator formalism was employed to vibrationally resolve the fixed-nuclei phase shifts obtained with the Schwinger multichannel method. The near-threshold behavior of the vibrational excitation cross section is in good agreement with available experimental data [Sullivan , Phys. Rev. Lett. 86, 1494 (2001)]. Though our fixed-nuclei calculations do not indicate the existence of a e(+)-H-2 virtual state, a proper description of the T matrix threshold behavior is essential (the adiabatic approximation is inadequate). The projection operator approach has long been a powerful tool for studies of nuclear dynamics in electron-molecule collisions, and its application to positron scattering is timely since couplings to nuclear degrees of freedom are known to be very important at low impact energies CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Aberto

Agradecimentos: The authors acknowledge support from Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). One of the authors (M.H.F.B) acknowledges support from the Paraná state agency Fundação Araucária and from FINEP (under Project No. CT-Infra 1) and computational support from Professor Carlos M. de Carvalho at DF-UFPR and from CENAPAD-SP Abstract: The authors report integral, differential and momentum transfer cross sections for elastic scattering of low-energy electrons by C4H4O (furan) molecules. Their calculations employed the Schwinger multichannel method with pseudopotentials and were performed in the static-exchange and in the static-exchange plus polarization approximations. The authors found two shape resonances located around 2.1 and 4.2 eV that belong to the B-1 and A(2) symmetries of the C-2v group, respectively. The authors' results are consistent with recent measurements of vertical electron attachment energies CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Fechado

Agradecimentos: The work was supported in part by a Grant-in-Aid, the Ministry of Education, Science, Technology, Sport and Culture, Japan, the Japan Society for the Promotion of Science (JSPS), and the Japan Atomic Energy Research Institute (JAERI). One of the authors (C.M.) is also grateful to the JSPS for financial support under Grant No. P04064. Another author (H.T.) acknowledges Dr. T. Ozeki of the JAERI for his encouragement and support during this work. This work was also done under the International Atomic Energy Agency (IAEA) project for three of the authors (C.M., M.H., and H.T.). Two of the authors (M.H.F.B. and M.A.P.L.) acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). MHFB also acknowledges support from the Paraná state agency Fundação Araucária and from FINEP (under Project No. CT-Infra 1). One of the authors (M.H.F.B.) also acknowledges Professor Carlos M. de Carvalho for computational support at Departamento de Física-UFPR. These calculations were made at CENAPAD-SP and a DF-UFPR Abstract: 1,1-difluoroethylene (1,1-C2H2F2) molecules have been studied for the first time experimentally and theoretically by electron and positron impact. 0.4-1000 eV electron and 0.2-1000 eV positron impact total cross sections (TCSs) were measured using a retarding potential time-of-flight apparatus. In order to probe the resonances observed in the electron TCSs, a crossed-beam method was used to investigate vibrational excitation cross sections over the energy range of 1.3-49 eV and scattering angles 90 degrees and 120 degrees for the two loss energies 0.115 and 0.381 eV corresponding to the dominant C-H (nu(2) and nu(9)) stretching and the combined C-F (nu(3)) stretching and CH2 (nu(11)) rocking vibrations, respectively. Electron impact elastic integral cross sections are also reported for calculations carried out using the Schwinger multichannel method with pseudopotentials for the energy range from 0.5 to 50 eV in the static-exchange approximation and from 0.5 to 20 eV in the static-exchange plus polarization approximation. Resonance peaks observed centered at about 2.3, 6.5, and 16 eV in the TCSs have been shown to be mainly due to the vibrational and elastic channels, and assigned to the B-2, B-1, and A(1) symmetries, respectively. The pi* resonance peak at 1.8 eV in C2H4 is observed shifted to 2.3 eV in 1,1-C2H2F2 and to 2.5 eV in C2F4; a phenomenon attributed to the decreasing C=C bond length from C2H4 to C2F4. For positron impact a conspicuous peak is observed below the positronium formation threshold at about 1 eV, and other less pronounced ones centered at about 5 and 20 eV CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Fechado

Agradecimentos: The authors would like to acknowledge the financial support from the Brazilian agencies Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). MHFB acknowledges support from the Paraná State agency Fundação Araucária and from FINEP. The authors acknowledge computational support from CENAPAD-SP Abstract: To illustrate our recent efforts to obtain electronic excitation cross sections of molecules by electron impact, we present in this paper results for the X (1)Sigma -> a (3)Pi and A (1)Pi transitions of CO obtained with the Schwinger multichannel method. Our results are in good agreement with other theoretical calculations, although not so good when compared with experiments. We also discuss the importance of inclusion of polarization effects to obtain electronic excitation cross sections of some molecules through an example using the C2H4 molecule, which has a triplet state with a low-energy threshold. Finally, we present a very simple rule to estimate integral electronic excitation cross sections using the differential cross section (DCS) at 90 degrees, which can be useful to experimentalists using apparatus with difficulties to measure the DCS's at angles around 0 and 180 degrees. We show its efficiency for the present electronic excitation of the C2H4 molecule by electron impact FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Aberto

Agradecimentos: The authors acknowledge support from Brazilian agency Conselho Nacional de Desenvolvimento Cientíifico e Tecnológico (CNPq). MHFB also acknowledges support from the Paraná state agency Fundação Araucária and from FINEP (under project CT-Infra 1) and computational support from Professor Carlos M de Carvalho at DF-UFPR and from CENAPAD–SP Abstract: We report elastic integral, differential and momentum transfer cross sections for low-energy electron collisions with the two isomers of C4H10, butane and isobutane. We employ the Schwinger multichannel method with pseudopotentials at the static-exchange-polarization approximation, and cover energies from 1 eV to 20 eV. We investigate the influence of polarization on the isomer effect comparing the cross sections of these isomers and concluded that polarization has a small influence in that effect. We also compare our computed elastic cross sections with available total cross sections. Total ionization cross sections by electron impact are computed using the binary-encounter-Bethe (BEB) model and the results compared with available experimental data. The ionization cross sections for butane and isobutane are similar, showing that they also have a small isomer effect in the ionization process CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO ARAUCÁRIA DE APOIO AO DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO DO ESTADO DO PARANÁ - FAPPR FINANCIADORA DE ESTUDOS E PROJETOS - FINEP Fechado

Orientadores: Marco Aurelio Pinheiro Lima, Marcio Henrique Franco Bettega Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: O objetivo principal desse trabalho foi a inclusão dos efeitos de polarização nos cálculos de seção de choque de espalhamento utilizando potenciais modelo. A implementação foi feita no método multicanal de Schwinger com pseudopotencial, utilizando uma descrição do potencial de polarização através de uma combinação de funções gaussianas. Com esse potencial, visamos diminuir o custo computacional existente na inclusão do efeito de polarização em um cálculo ab-initio. Utilizamos três potenciais conhecidos na literatura, sendo o primeiro o potencial que relaciona um efeito de curto alcance (correlação), derivado de um modelo de gás de elétrons livres, com o longo alcance (polarização). O segundo potencial possui a forma mais simples, constante para raios perto da origem, e decai como um potencial de polarização. O terceiro potencial possui um fator exponencial que faz o seu valor ser próximo de zero na origem e decai como um potencial de polarização. Apresentamos um modelo de polarização descrito pelo deslocamento da densidade de carga com um parâmetro calculado de forma ab-initio. Utilizando o terceiro potencial modelo calculamos a seção de choque integral, de transferência de momento e diferencial para as moléculas de CH4, SiH4, GeH4, PbH4, SnH4, CF4 e SiF4. Os resultados obtidos foram comparados com os dados existentes na literatura e obtivemos uma boa concordância entre eles Abstract: The aim of this work is the inclusion of polarization effects in the calculations of scattering cross section by using model potentials. The implementation was made in the Schwinger multichannel method with pseudopotentials, using a description of polarization potential with gaussians functions. With this potential we entend to reduce the computational cost present in the inclusion of polarization effects through ab-initio calculation. We use three potentials that can be found in the literature. The first potential relates the short range effect (correlation) derivated from a free electron gas model, with the long range effect (polarization). The second potential has the simplest form, for radius close to zero the potential tends to a constant, and for large r it decays like a polarization potential. The third potential has a exponential factor that is zero in the origin and it decays like a polarization potential for large r. We present a polarization model described by a displacement of a eletric charge density with a ab-initio calculated parameter. Using the third model potential we calculated the integral, momentum transfer and diferential cross section for CH4, SiH4, GeH4, PbH4, SnH4, CF4and Si F4molecules. Our results had been compared with experimental data and we have good agreement Doutorado Física Atômica e Molecular Doutor em Ciências

Orientador: Marco Aurelio Pinheiro Lima Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: A relação entre ressonâncias de Feshbach e excitações eletrônicas é bem conhecida no caso de espalhamento de elétrons por moléculas de H2, mas ainda pouco explorada no espalhamento de pósitrons, tornando interessante, portanto, um estudo comparativo. Porém, antes de pensarmos em comparações, nos preocupamos em tentar entender se, de fato, uma ressonância de Feshbach se manifesta no espalhamento de pósitrons por moléculas de H2. Esta preocupação foi motivada devido à não observação experimental desta ressonância em investigação realizada logo após nosso grupo de pesquisa ter publicado um estudo no qual havia evidências para a existência de uma ressonância de Feshbach em colisões pósitron-H2, obtida num cálculo realizado na aproximação de núcleos fixos para a distância internuclear de equilíbrio Ro=1.4ao. Nossa estratégia foi calcular seções de choque, ainda na aproximação de núcleos fixos, para diversas distâncias internucleares em torno de Ro. Os resultados obtidos sugerem que a ausência experimental da ressonância esteja ligada à abertura de um novo canal eletrônico para R > Ro. Para esses cálculos utilizamos o Método Multicanal de Schwinger (SMC), para obtenção dos parâmetros de colisão (posição e largura da ressonância), em combinação com a aproximação do Potencial Complexo Local (também conhecido por Boomemng Model), para inclusão do acoplamento dos graus de liberdade vibracionais. A ausência da ressonância para algumas distâncias internucleares no espalhamento de pósitrons impede o cálculo de seções de choque vibracionalmente resolvidas através da aproximação local. Por outro lado, para o espalhamento de elétrons, que é um desafio como problema teórico, realizamos os cálculos e encontramos acordo razoável com os dados experimentais disponíveis Abstract: The relationship between Feshbach resonances and electronic excitation is well known in electron scattering by Hydrogen molecules, but still little exploited in the positron scattering case, making interesting, a comparative study. However, before thinking about comparisons, we have to address the question if, in fact, a Feshbach resonance manifests itself in the positron scattering by Hydrogen molecules. This issue is motivated by the fact that recent measured cross sections have not shown the same features presented by our earlier calculated Feshbach resonance in positron-Hydrogen collisions, carried out in the fixed-nuclei approach for the equilibrium internuclear distance, Ro=1.4ao. Our strategy was to calculate cross sections, still in the fixed nuclei approach, for several internuclear distances around Ro. The obtained results suggest that the experimental absence of the resonance is related to the opening of a new electronic channel for R > Ro. For these calculations we have used the Schwinger Multichannel Method (SMC) to obtain the collision parameters (position and width of the resonances) in combination with the Local Complex Potential approach (also known for Boomerang Model), for inclusion of the coupling of the vibrational degrees of freedom. The absence of the resonance for some internuclear distantes prevents the calculation of vibrationally resolved cross sections by positron impact using the local approach. On the other hand, for the electron scattering case, which is also a challange as a theoretical problem, we have carried out the calculation and have found good agreement with available experimental data Mestrado Física Atômica e Molecular Mestre em Física

Orientadores: Marco Aurelio Pinheiro Lima, Luiz Guimarães Ferreira Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Cálculos de seções de choque para o espalhamento de elétrons por moléculas têm sido limitados a alvos com poucos elétrons. Neste trabalho, mostramos, através de algumas aplicações, que a utilização de pseudopotenciais suaves (e "norm-conserving") na descrição do alvo e nos cálculos de espalhamento torna possível o estudo do espalhamento de elétrons de baixa energia por moléculas com muitos elétrons. As moléculas estudadas foram: CF4, CCl4, SiCl4, SiBr4 e SiI4, que contêm 42, 74, 82, 154, e 226 elétrons, respectivamente. Os pseudopotenciais substituem o núcleo e os elétrons de caroço de cada átomo de modo que apenas a valência é descrita por uma teoria de muitos corpos. Nossos resultados concordam qualitativamente com os dados experimentais disponíveis. Exceto para o CF4, mostramos seções de choque teóricas para essas moléculas pela primeira vez. Nossos resultados para o CF4 estão em excelente acordo com o dado teórico disponível na literatura [8], que é um cálculo com todos os elétrons. Para essa mesma molécula, nossas seções de choque diferenciais também concordam de maneira excelente com os dados experimentais [11] Abstract: Cross section calculations of low-energy e--molecule scattering have been limited to targets with few electrons. We show that the use of soft norm-conserving pseudopotentials in the target description and in the scattering calculations makes possible the study of the low-energy electron scattering by many-electron molecules. We present results for CF4, CCl4, SiCl4, SiBr4 and SiI4, with 42, 74,82, 154, and 226 electrons respectively. The pseudopotentials replace the nucleus and the core electrons of each atom so that only the valence is described in a many-body framework. Our calculated cross sections are in good qualitative agreement with experiment. Except for CF4, we show theoretical cross sections for these molecules for the first time. For the CF4 molecule our results are in excellent agreement with the theoretical data available in the literature [8] , which is an all-electron calculation, and also with the experimental results [11] Mestrado Física Mestre em Física

Orientadores: Marco Aurelio Pinheiro Lima, Luiz Guimarães Ferreira Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Pseudopotencial de Norma Conservada de Bachelet, Hamann, e Schluter (1982) foi introduzido em programa de colisão de elétron-molécula por Bettega, Ferreira e Lima (1993). Transferibilidade de pseudopotenciais não pode ser provada em geral, deve ser mostrada caso a caso. Nesta tese nós testamos o uso de pseudopotencial numa situação onde o processo apresenta uma forma ressonante. Nós específicamente estudamos a sensibilidade quanto a posição e largura da ressonância de forma 2Pg em espalhamento e - N2 utilizando o Método Multicanal de Schwinger (SMC) com e sem pseudopotencial Abstract: Norm Conserving pseudopotentials of Bachlet, Hamann and Schliiter (1982) have been introduced in electron-molecule collision computer code by Bettega, Ferreira and Uma (1993). Transferability of pseudopotentials cannot be proven in general, it must be shown case by case. In this thesis we test the use of pseudopotential in a situation where the process presents a shape resonant. We specifically study the sensibility of the position and width of the 2Pg shape resonance in e - N2 scattering using the Schwinger Multichanel Method (SMC) with and without pseudopotential Mestrado Física Mestre em Física

Orientadores: Marco Aurelio Pinheiro Lima, Fernando Jorge da Paixão Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Apresentamos neste trabalho as seções de choque de excitação eletrônica da molécula de H2 por impacto de elétrons de baixa energia obtidas pelo método multicanal de Schwinger. Os cálculos foram realizados de acordo com uma estratégia que utiliza uma base mínima de orbitais na representação dos estados eletrônicos de interesse, a qual denominamos MOB-SCI ( minimal orbital basis for single configuration interactions). Esta técnica apresenta como vantagens a representação mais elaborada do primeiro estado singleto e do primeiro estado tripleto de uma dada simetria através do uso do método de interação de configurações para excitações simples do alvo molecular e a minimização do espaço associado de pseudo-estados. Com a utilização da aproximação MOB-SCI observamos um efeito sistemático de redução na magnitude das seções de choque para as transições consideradas neste estudo. Os resultados obtidos apresentam, de maneira geral, uma boa concordância com os dados experimentais e, sem dúvida, representam um avanço em comparação aos cálculos a dois canais. Além disso, este estudo traz à tona a constatação de que os estados singleto e tripleto de uma mesma simetria espacial são fortemente acoplados e, em muitos casos, os resultados são melhores do que aqueles obtidos em estudos que levam em consideração apenas o acoplamento de estados com mesma simetria de spin. Este, de fato, representa um resultado expressivo e ainda inédito na literatura Abstract: We present in this work the low-energy electron-impact electronic excitation cross sections for H2 molecules. The calculations were performed within the so-called MOB-SCI (minimal orbital basis for single configuration interactions) level of approximation. This strategy takes advantages from the fact that as long as at least the first singlet and first triplet states from a given symmetry representation are properly described by the CIS approach, the associated pseudo-state space is minimized. Through the use of the MOB-SCI technique we observed a systematic reduction effect in the magnitude of calculated cross sections. The results show a significant improvement towards experimental data in comparison with earlier two-state close coupling calculations. Besides, the strong coupling between singlet and triplet states is an important feature for the first time accounted in the study of e--H2 electronic excitation. This preliminary study highlights the advantages of the present strategy and represents a clear invitation for further investigations Doutorado Física Doutor em Ciências

Orientador: Marco Aurelio Pinheiro Lima Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Apresentamos neste trabalho aplicações do Método Multicanal de Schwinger adaptado para espalhamento de pósitrons de baixas energias, onde se compara dois sistemas moleculares isoeletrônicos: a molécula de acetileno e a molécula de nitrogênio. Estes sistemas são de grande interesse por apresentarem comportamentos díspares com relação ao parâmetro de aniquilação, Zeff . Embora com um número de elétrons ligeiramente pequeno ( Z = 14), chegam a apresentar uma diferen. ca de um fator de 102 em suas taxas de aniquilação. Além disso, por apresentar um altovalor de Zeff , a molécula de acetileno se torna um alvo extremamente interessante de ser estudado, por permitir abordar, utilizando cálculos ab initio , a dinâmica de aniquilação necessária para explicar os altos valores experimentais de e Zeff observados em alguns sistemas moleculares (geralmente moléculas orgânicas grandes), que, em sua maioria, são inviáveis computacionalmente aos nosso cálculos. Através dos resultados de Zeff , seções de choque integrais e diferenciais, autofases, dentre outros, introduziremos a importância do estado virtual e da mobilidade eletrônica na dinâmica de aniquilação. Verificaremos a formação de um estado virtual para o alvo de acetileno, inexistente no alvo de nitrogênio, que irá comandar a aniquilação ocasionando os altos valores de Zeff Abstract: We present applications of the Schwinger Multichannel Method adapted for low energy positron scattering, comparing two isoelectronic molecular systems: acetylene and nitrogen molecules. These systems awake great interest because they present different behavior for the Zeff parameter. Although with small number of electrons ( Z = 14), they present values differing by a factor of 102 on their annihilation rates. Further, for presenting a high value of Zeff , the acetylene molecule becomes an interesting target to be studied since it allows us to approach, using ab initio calculations, the annihilation dynamics necessary to explain the high experimental values of Zeff observed for many molecular systems (usually large organic molecules), which, in most cases, are computationally not feasible for our calculations. Through results of Zeff , integral cross sections, differential cross sections, eigenphases, and others, we will introduce the importance of the virtual state and of the electronic mobility to the annihilation dynamics. We confirm the formation of a virtual state for acetylene target, non-existent for nitrogen target, which will command the annihilation, causing the high values of Zeff Doutorado Física Doutor em Ciências

Orientador: Marco Aurelio Pinheiro Lima Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Não informado Abstract: Not informed. Doutorado Física Doutor em Ciências

Orientadores: Jayr de Amorim Filho, Marco Aurélio Pinheiro de Lima Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin Resumo: Neste trabalho plasmas não térmicos gerados em pressão atmosférica e sustentados por ondas de superfície em micro-ondas, tendo o argônio como gás de alimentação, foram estudados experimentalmente e teoricamente tendo em vista aspectos pouco compreendidos de suas propriedades físicas e aplicações voltadas ao tratamento de biomassa. Medições da composição elementar e dos parâmetros físicos foram realizados por meio de técnicas de diagnóstico baseadas em espectrometria de massa e espectroscopia óptica de emissão. O sistema físico foi modelado por meio das equações de continuidade das espécies neutras e carregadas, da equação do calor e da equação de Boltzmann dos elétrons, que foram acopladas utilizando um procedimento auto-consistente. Uma vez obtido o quadro geral das propriedades do plasma, foi estabelecida a condição de operação adequada ao tratamento das amostras derivadas de biomassa. O tratamento foi realizado sobre quatro tipo de amostras: lignina, xilana, celulose e bagaço de cana-de-açúcar. Dentre as contribuições importantes deste trabalho podem ser destacadas: (i) a verificação experimental do papel dos íons moleculares do argônio no processo de contração da descarga; (ii) a determinação do perfil axial no plasma dos principais íon positivos e negativos, da densidade e temperatura eletrônicas, da temperatura do gás e da densidade do estado metaestável Ar(1s5); (iii) verificação da seletividade do tratamento a plasma, tendo sido observada uma alteração significativa dos espectros de absorção no infravermelho nos casos da lignina e da xilana, mas não no caso da celulose. Esse último resultado sugere uma rota inusitada para novas tecnologias de deslignificação e síntese de novos materiais a partir de biomassa Abstract: In this work non-thermal argon plasmas produced at atmospheric pressure and sustained by microwave surface waves were theoretically and experimentally studied in view of their non understood aspects and also the applications aimed at biomass treatment. Measurements of elemental composition and physical parameters were carried by means of plasma diagnostic techniques such as mass spectrometry and optical emission spectroscopy. Plasma modelling based on the self-consistent solution of the continuity equations of the neutral and charged species, the heat equation and the electron Boltzmann equation was developed to describe the plasma properties. Once a complete picture of the plasma behaviour was obtained, a promising condition for plasma treatment was established. Four types of biomass derived material were plasma treated: lignin, cellulose, xylan and sugarcane bagasse. Among the important contributions of this work one may highlight the following: (i) the experimental verification of the crucial role of argon molecular ions in the discharge contraction; (ii) axial profile determination of the main positive and negative ions, the electronic temperature and density, the gas temperature and the metastable state Ar(1s5) density; (iii) important modification of the infrared absorption spectra after plasma treatment in the cases of lignin and xylan, but not in the case of cellulose, suggesting a unexpected route for delignification and new materials synthesis from biomass Doutorado Física Doutor em Ciências

Orientadores: Márcio Texeira do Nascimento Varella, Marco Aurélio Pinheiro Lima Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: O Método Multicanal de Schwinger (SMC) foi utilizado para estudar o espalhamento de elétrons e pósitrons de baixa energia por moléculas de pirrol (C4H4NH) e propanol (C3H7OH), para o primeiro caso, e acetileno (C2H2) e monóxido de carbono (CO), para o último caso. Seções de choque elásticas integrais e diferenciais foram calculadas para todos os sistemas, exceto para colisões pósitron-acetileno. Neste caso, utilizando o SMC combinado com o Formalismo dos Operadores de Projeção de Feshbach, seções de choque vibracionalmente resolvidas e o parâmetro de aniquilação (Zeff) foram calculados para a transição 0--> 1. No que se refere ao espalhamento de elétrons, as seções de choque integrais (ICS) calculadas para moléculas de pirrol indicam a formação de ressonâncias * (não dissociativas) e ? * (dissociativas), as quais podem dar origem a mecanismos de dissociação indireta e direta. Sendo assim, o pirrol é um protótipo adequado para o entendimento dos detalhes acerca de danos causados no DNA por elétrons de baixa energia. Já as ICS's obtidas para moléculas de propanol estão em bom acordo com os resultados teóricos e experimentais disponíveis na literatura. Para colisões de pósitrons, os resultados obtidos para moléculas de acetileno, para a transição O --> 1 num modelo de onda s, apontam para a formação de um estado virtual o qual torna-se um estado ligado quando as ligações C-C e C- H são deformadas ao longo dos modos normais de estiramento simétrico inativos no infravermelho. Embora pouco representativos, tais modos estão em assina,turas claras no parâmetro de aniquilação. As seções de choque possuem bom acordo com resultados extraídos da literatura. Por outro lado, os modos normais C-H de estiramento assimétrico e bendin,q ativos no infravermelho, por simetria, não contribuem para a seção de choque e parâmetro de aniquilação para a transição O --> 1 num modelo de onda s. Para colisões pósitron-CO, bom acordo foi encontrado entre a seção de choque integral calculada e dados teóricos e experimentais disponíveis na literatura Abstract: The Schwinger Multichannel Method (SMC) was employed to study scattering of low-energy electrons and positrons by pyrrole (C4H4NH) and propanol (C3H7OH) molecules, for the former, and acetylene (C2H2) and carbon inonoxide (CO), for the latter. Elastic differential and integral cross sections were calculated for alI systems, except for positron-acetylene collisions. In this case, using the SMC combined with the Feshbach Projection Operator approach, vibrationally resolved cross sections and annihilation parameter were obtained for the O --> 1 transition. For electron scattering, the integral cross sections lecules indicate ¶* (non dissociative) and O+* (dissociative) resonances, which can give rise to indirect and direct dissociation mechanisms. In view of this, pyrrole molecules are a suitable prototype for detailed studies of dissociative electron attachment to DNA. For electron-propanol collisions, reasonable agreement was obtained between present and calculated and measured results available in the literature. For positron scattering, the results obtained for acetylene molecules, for the O --> 1 transition and an s-wave model, pointed out a virtual state pole that becomes a bound state as either bond C-C or C-H are stretched along the infrared inactive symmetric modes. Although not significant, these modes have clear assignments in the annihilation parameter. Present cross sections agree very well with calculated results of the literature. On the other hand, the C- H asymmetric and bending infrared active modes, due to the parity of vibrational modes, cannot contribute for cross sections and annihilation parameter for the O --> 1 transition in an s-wave modelo For positron-CO collisions, good agreement was found between present ICS and the measured and calculated results available in the literature Doutorado Física Atômica e Molecular Doutora em Ciências

Orientador: Marco Aurelio Pinheiro Lima Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Nesta tese investigamos a modelagem teórica de colisões pósitron-molécula no regime de baixas energias utilizando o método Schwinger multicanal. Nosso objetivo inicial foi sofisticar o procedimento de cálculo do parâmetro de aniquilação¸ Zeff . Esta quantidade é diretamente proporcional a taxa de aniquilação de pósitrons com elétrons da nuvem molecular. Infelizmente o método subestima Zeff com relação aos dados experimentais. Uma investigação mais detalhada sugere que esta deficiência está ligada a uma descrição pobre do cúspide elétron-pósitron na função de onda de espalhamento. Para tanto, inserimos um potencial complexo tipo delta de Dirac na Hamiltoniana de espalhamento com o objetivo de melhorar o cálculo de aniquilação direta e possivelmente adaptá-lo para descrever o canal de formação do positrônio real. Aplicação a sistemas modelo como átomo de He e molécula de H2 mostraram que esta técnica alternativa produz resultados similares ao cálculo perturbativo usual. Neste sentido a discrepância entre o parâmetro de aniquilação teórico obtido via método Schwinger multicanal e os dados experimentais continua em aberto. Recentemente o grupo da Universidade de San Diego, na Califórnia, desenvolveu um aparato experimental para medir seções de choque de excitação eletrônica de átomos e moléculas por impacto de pósitrons. O método Schwinger multicanal é o único que tem atacado sistematicamente este problema para moléculas na literatura. Neste trabalho, damos continuidade a este programa de pesquisa calculando seções de choque de excitação eletrônica para as moléculas de H2 e CO com variados níveis de aproximação. Nossos resultados indicam que as seções de choque integrais são insensíveis ao nível de acoplamento multicanal utilizado na modelagem da colisão e que efeitos de polarização podem ser particularmente importantes para energias imediatamente acima dos limiares de excitação eletrônica. Finalmente, e este sem dúvida é o maior resultado desta tese, aprendemos a tratar as bases variacionais usadas no cálculo de espalhamento. A evidência de que tal nível de maturidade foi atingido é a convergência das seções de choque com relação aos métodos de cálculo dos elementos de matriz da função de Green, anteriormente obtida somente por ajuste (popularmente conhecido como "chute") do conjunto de primitivas Gaussianas utilizado no cálculo de espalhamento Abstract: In this thesis we investigate the theoretical modelling of positron-molecule collisions in low energy regime using the Schwinger multichannel method. Our initial objective was to sophisticate the procedure of calculation of the annihilation parameter Zeff. This quantity is directly proportional to the annihilation rate of positrons with molecular cloud electrons. Unhapilly the method underestimates Zeff compared to the experimental data. A more detailed investigation suggests that this deficiency is connected with a poor description of the electronpositron cusp of the scattering wave function. To this end, we inserted a complex potential of Dirac delta type in the scattering Hamiltonian with the major objective of improving the direct annihilation calculation and possibly to adaptate it to describe the real positronium formation channel. Aplication to model systems like He atom and H2 molecule showed that this alternative technique produce similar results compared to the usual perturbative calculation. In this sense, the discrepancy between the theoretical annihilation parameter generated by Schwinger multichannel method and the experimental data remains as an open problem. Recently the research group of San Diego University, in California, developed an experimental apparatus to measure electronic excitation cross sections for atoms and molecules by positron impact. The Schwinger multichannel method is the only that has sistematicaly attacked the problem for molecules in the literature. In this work, we continue this research program calculating electronic excitation cross sections for H2 and CO molecules with varied degrees of approximation. Our results indicate that integral cross sections are insensible to the level of multichannel coupling used in the collision model and that polarization effects can be particularly relevant for energies immediately above electronic excitation thresholds. Finally, and this doubtless is the greater result of this thesis, we learnt to treat the variational basis used in the scattering calculation. The evidence that such level of maturity was reached is the convergence of the cross sections by the methods of computation of the Green¿s function matrix elements, obtained before only by "guessing" of the set of primitive Gaussians employed in the scattering calculation Doutorado Física Atômica e Molecular Doutor em Ciências

Orientador: Marco Aurélio Pinheiro Lima Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin Resumo: Nesta dissertação apresentamos seções de choque diferenciais (DCSs) para a excitação eletrônica para os estados de mais baixa energia dos tautômeros trans e gauche da molécula de etanol, assim como seções de choque totais para a faixa de energia de 15-50 eV. Os cálculos foram realizados utilizando o Método Multicanal de Schwinger (SMC) implementado com pseudopotenciais. Levamos em conta 11, 41, 183, 317 e 431 canais abertos para o tautômero trans e, para o gauche, os três primeiros acoplamentos multicanais citados, devido à limitação computacional associada ao grupo pontual C1 desse tautômero. Até o momento, os nossos cálculos foram os mais sofisticados com respeito ao número de canais abertos já realizados com o método SMC. Encontramos, no geral, um bom acordo em relação aos resultados experimentais disponíveis na literatura para ângulos intermediários e em energias de impacto maiores (a partir de 15 eV). Entretanto, mesmo utilizando o procedimento Born-closure para melhorar a descrição de interações de longo alcance de dipolo (deficiente devido ao uso de funções quadraticamente integráveis), não obtivemos uma boa descrição dos ângulos pequenos nas DCSs calculadas com o SMC para estados com transições permitidas por dipolo. Esses resultados indicaram que o pobre acordo em baixos ângulos está associado à má descrição das menores ondas parciais. Com respeito às DCSs em menores energias de impacto, no geral, superestimamos os resultados experimentais. A falta de mais canais abertos pode estar associada com as discrepâncias remanescentes em relação ao experimento, mas aqui argumentamos que outros fatores também devem estar envolvidos. Visando uma descrição melhorada dos estados excitados do alvo, propomos um procedimento simples para selecionar pares de orbitais buraco e partícula, preservando a descrição de excitações simples da implementação atual do SMC. Uma avaliação quantitativa do processo de colisão deve ainda considerar a contribuição individual de cada tautômero, os quais apresentaram DCSs bastante distintas em alguns casos. Nossas energias de excitação calculadas suportam que a segunda banda de absorção do etanol compreende três estados singletos, em vez de dois ou quatro, que foram sugeridos em trabalhos anteriores Abstract: In this dissertation we present differential cross sections (DCSs) for the electronic excitation of the lower-lying states of the trans and gauche tautomers of the ethanol molecule, as well as total cross sections for the energy range of 15-50 eV. The calculations were performed using the Schwinger Multichannel method (SMC) implemented with pseudopotentials. We took into account 11, 41, 183, 317 and 431 open channels for the trans tautomer and the first three levels of multichannel coupling mentioned for the gauche, due to the computational limitation associated with the C1 point group of this tautomer. So far, our calculations using the SMC method are the most sophisticated in terms of the number of open channels. In general, we found a good agreement with the experimental results available in the literature for intermediate angles and higher impact energies (above 15 eV). However, even when using the Born-closure procedure to improve the long range dipole interaction (deficient due to the use of quadratically integrable functions), we did not obtain a good description of the forward scattering in the DCSs calculated with the SMC method for dipole allowed transitions. These results indicated that the unsatisfactory agreement on smaller scattering angles is associated with a poor description of the lower partial waves. In general, with regard to the DCSs at lower impact energies, we overestimated the experimental data. Missing open channels are usually evoked to explain the remaining discrepancies to experiment, but here we argue that other factors should also be involved. Aiming at an improved description of the target states, we have proposed a simple procedure for selecting the pairs of hole and particle orbitals, while keeping the single excitation prescription of the current SMC implementation. A quantitative assessment of the collision process should further consider the individual contribution of each tautomer, which presented quite distinct DCSs in some cases. Our computed excitation energies also support that the second absorption band of ethanol is comprised of three singlet states of each tautomer, rather than the previously suggested two or four states Mestrado Física Mestre em Física CNPQ 135900/2018-2

Orientador: Marco Aurelio Pinheiro Lima Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin" Resumo: Neste trabalho realizamos cálculos comparativos para seções de choque de excitações vibracionais integrais e diferenciais para o espalhamento de pósitrons e elétrons de baixa energia contra a molécula de Hidrogênio (H2). Para estes cálculos utilizamos o Método Multicanal de Schwinger (SMC) [1] para a colisão de pósitrons [2] e colisão de elétrons [3]. Usando um conjunto de amplitudes de espalhamento oriundas do SMC, calculadas segundo uma quadratura específica (Hermite [4]) de pontos correspondendo à distâncias internucleares, obtivemos as seções de choque vibracionalmente resolvidas segundo a Aproximação Adiabática [5]. Para poder comparar o processo de espalhamento de elétrons com o de pósitrons, as amplitudes de espalhamento foram calculadas com o mesmo conjunto de base representando o alvo molecular e a função de espalhamento da partícula. Para a função de onda vibracional utilizamos as autofunções de um oscilador harmônico simples (com freqiiência experimental) para ambos os casos de espalhamento de elétron e pósitron Abstract: Here we report a comparative calculation of both integral and differential vibrational excitation cross sections of low energy positron and electron scattering against Hydrogen molecules (H2). For these calculations we have used the Schwinger Multichannel (SMC) Method [1] for positron collision [2] and electron collision [3]. Using a set of SMC scattering amplitudes, calculated at specific quadrature points (Hermite [4]) of internuclear distances, we have obtained vibrational resolved cross sections in the Adiabatic Aproximation [5]. In order to compare the electron scattering process with the positron one, the scattering amplitudes were calculated with the same basis set for representing the molecular target and scattering particle wave functions. For the vibrational wave functions we have used the eigenfunctions of a simple harmonic oscillator (with the experimental frequency) for both cases, the electron and positron scattering Mestrado Física Atômica e Molecular Mestre em Física

Orientadores: Marco Aurelio Pinheiro Lima, Antonio Jose Roque da Silva Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Apresentamos um novo e mais e .ciente modo de tratar efeitos de polarização no espalhamento de elétrons de baixa energia por moléculas utilizando o método multicanal de Schwinger (smc ). Nós propomos expandir a função de onda de espalhamneto num conjunto de funções de N +1 elétrons que descrevem o espalhamento de uma forma eficiente, que permiti-nos usar um pequeno número de funções para descrever efeitos de polarização. Como primeiro teste, nós aplicamos o novo método ao espalhamento de elétrons pela molécula de H2. Nós calculamos a seção de choque integral e diferencial,e obtemos resultados excelentes com uma redução de até 98%no número de con .gurações quando comparado ao método tradicional usado no SMC . Isto é uma redução substancial no tamanho de todas as matrizes envolvidas no método SMC e, como conseqüência, representa uma técnica promissora para tratar sistemas moleculares mais complexos Abstract: We present a new and more efficient way of treating polarization effects in the scattering of low-energy electrons by molecules within the Schwinger multichannel method (SMC).We propose to expand the scattering wave function in a set of functions of N +1 electrons that describe the scattering in an e .ective way,which allows the use of a small number of functions to describe the polarization effects. As a first test, we apply the new method to the scattering of electrons by the H2 molecule.We calculate elastic integral and differential cross-sections,and we obtain excellent results with a reduction in the number of con .gurations of up to 98% when compared to the traditional method used in the SMC. This a substantial size reduction of all matrices involved in SMC Method and,as a consequence, it represents a promising technique for treating more complex molecular systems Doutorado Física Doutor em Ciências

Orientadores: Luiz Guimarães Ferreira, Marco Aurelio P. Lima Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Pseudopotenciais tem sido recentemente usados no cálculo de seção de choque no espalhamento de elétrons por molécula. As vantagens do pseudopotencial são dupla: eles substituem os elétrons do caroço e as funções de ondas são suaves. Então, não só eles simplificam os cálculos, reduzindo o número de elétrons, mas também permitem expansões menores às funcões de ondas. Para moléculas feitas com átomos pesados, os pseudopotenciais permitem cálculos que não são possivéis através de métodos de todos os elétrons. Uma outra vantagem no uso de pseudopotenciais é que eles incluem efeitos de correlação eletrônica caroço-valência e também podem incluir correções relativisticas. Entre os pseudopotenciais, reconhecemos que a classe norm-conserving é a melhor, porque eles são gerados de maneira que as pseudofunções de onda se igualam a função real. Desta forma, assegura a igualdade da derivada em relação a energia da derivada em relação a r do logaritmo da função de onda. Há muitas propostas para geração de pseudopotenciais norm-conserving. Em Física do Estado Sólido, nós usualmente usamos bases em ondas planas, assim nós estamos interessados em pseudopotenciais cuja transformada de Fourier caia rapidamente com o número de onda( pseudopotenciais ultrasoft ). Em cálculos moleculares as bases Gaussianas são preferidas e o tamanho das expansões em funções de onda praticamente não depende da suavidade do pseudopotencial, contanto que seja de norma conservada. Neste caso nós só nos preocupamos com a precisão dos cálculos. Nós calculamos seções de choque diferencial e total usando o método de multical de Schwinger com pseudopotenciais para as molécula de HBr (com resultados igual ao do método de Kohn), Si2H6, PbH4, CH4, SiH4, and SnH4 testando os pseudopotenciais da referência [2], [6] a [8]. O pseudopotencial [2] foi gerado a partir de cálculos moleculares, enquanto os outros foram gerados dentro da Fisica do Estado Sólido. O pseudopotencial da referência [7] é considerado soft. Então nossos calculos mediram uma grande amostra de pseudopotenciais de norma conservada. Nossos códigos de computador requerem que os pseudopotenciais sejam finitos no núcleo. No caso do pseudopotencial da referência [2] tivemos que cortar sua divergência. Nenhum pseudopotencial pode ser considerado claramente como o melhor. Em algumas energias de impacto é possivel notar diferença, especialmente na região de alto ângulo. Nesta região, o elétron penetra mais profundamente na molécula, percebendo a diferença entre os pseudopotenciais Abstract: Pseudopotentials have been recently used with the calculation of electron-molecule cross sections by different methods. The advantages of the pseudopotentials are double: they avoid the core electrons and render the wavefunctions much slowly varying. Therefore, not only they simplify the calculations by reducing the number of electrons but they also allow much shorter expansions for the wavefunctions. For molecules made of heavier atoms, the pseudopotentials allow calculations that are not possible by all-electron methods. There are other side benefits in the pseudopotentials: to a large extent they include the effects of core-valence electronic correlation and may also include relativistic corrections. Among the pseudopotentials, we now recognize that the class of norm-conserving em pseudopotentials is the best because they are generated in such a way that the norms of the pseudo wavefunctions equal those of the true wavefunctions. Of course, this equality assures the equality of the energy derivatives of the logarithm derivatives. There are many proposals for generation of norm-conserving pseudopotentials. In Solid State Physics, we usually use bases of plane waves so we are interested in pseudopotentials whose Fourier transforms decay fast with wavenumber ( ultrasoft pseudopotentials ). In molecular calculations the Gaussian bases are preferred and the size of the wavefunction expansions practically has no dependence on the "softness" of the pseudopotential, as long as it is norm-conserving. In this case we are concerned only with the precision of the calculation. We calculated cross sections of electron-molecule scattering using the pseudopotential Schwinger Multichannel Method for the molecules HBr ( with results equal to those of a complex Kohn calculation40 ), Si2H6, PbH4, CH4, SiH4, and SnH4 testing the pseudopotentials of refs. [2], [6] to [8]. The pseudopotential of ref. [2] was generated aiming at molecular calculations, while the other were generated within Solid State Physics. The pseudopotential of ref. [7] may be considered ultrasoft. Therefore our calculations span a large sample of norm-conservíng pseudopotentials. Our computer code requires that the pseudo-potential remains finite at the nucleus. In the case of the pseudopotential of ref. [2] we had to cut its divergence. No pseudopotential can be clearly pointed out as the best. For some special impact energies it is possible to notice differences, specially in the back scattering region. In the back scattering regime, the electron penetrates more deeply into the atoms where it enhances the differences between the many pseudopotentials Doutorado Física Doutor em Ciências

Orientadores: Marco Aurelio Pinheiro Lima, Luiz Guimarães Ferreira Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin Resumo: Este estudo mostra aplicações do método multicanal de Schwinger com pseudopotenciais ao espalhamento de elétrons por diversas moléculas em quatro diferentes níveis de aproximação: ( i ) aproximação estático-troca, ( ii ) excitações eletrônicas na aproximação de dois canais, ( iii ) espalhamento elástico incluindo efeitos de polarização e ( iv ) acoplamento multicanal com efeitos de polarização. Os resultados concordam com os dados experimentais disponíveis na literatura, respeitando-se a faixa de energia de impacto onde cada aproximação é válida. A utilização de pseudopotenciais na descrição dos elétrons de caroço do alvo molecular em cálculos de espalhamento de elétrons se mostrou muito eficiente em todas as aproximações estudadas, confirmando os indicativos de estudos anteriores. O método nos fornece uma ferramenta confiável e poderosa na descrição de alvos moleculares com muitos elétrons. Além disso, são discutidos alguns detalhes sobre a validade do método multicanal de Schwinger em cada uma das aproximações utilizadas Abstract: This study shows applications of the Schwinger multichannel method with pseudopotentials at four different levels of approximation: ( i ) static-exchange approximation, ( ii ) two-channel electronic excitations, ( iii ) elastic scattering including polarization effects and ( iv ) multichannel coupling with polarization effects. The theoretical results agree with available experimental data, considering the electron impact energy where each approximation is designed to be valid. The use of pseudopotentials to describe the core of molecular targets in electron scattering calculations was shown to be very efficient in all studied approximations, and confirm the hints of earlier studies. The method is a reliable and powerful framework to describe many-electron molecules. Also, some details on the validity of the Schwinger multichannel method in each approximation are discussed Doutorado Física Doutor em Ciências