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Absolute total cross section (TCS) measurements for electron scattering from 1-propanol molecules are reported for impact energies from 40 to 500 eV. These measurements were obtained using a new apparatus developed at Juiz de Fora Federal University--Brazil, which is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the molecules to be studied at a given pressure. Besides these experimental measurements, we have also calculated TCS using the Independent-Atom Model with Screening Corrected Additivity Rule and Interference (IAM-SCAR+I) approach with the level of agreement between them being typically found to be very good. [ABSTRACT FROM AUTHOR]

Measurements of the grand total and total positronium formation cross sections for positron scattering from uracil have been performed for energies between 1 and 180 eV, using a trap-based beam apparatus. Angular, quasi-elastic differential cross section measurements at 1, 3, 5, 10, and 20 eV are also presented and discussed. These measurements are compared to existing experimental results and theoretical calculations, including our own calculations using a variant of the independent atom approach. [ABSTRACT FROM AUTHOR]

We report absolute differential cross sections (DCSs) for elastic electron scattering from OCS (carbonyl sulphide) and CS2 (carbon disulphide) in the impact energy range of 1.2-200 eV and for scattering angles from 10° to 150°. Above 10 eV, the angular distributions are found to agree quite well with our present calculations using two semi-phenomenological theoretical approaches. One employs the independent-atom model with the screening-corrected additivity rule (IAM-SCAR), while the other uses the continuum-multiple-scattering method in conjunction with a parameter-free exchange-polarization approximation. Since OCS is a polar molecule, further dipole-induced rotational excitation cross sections have been calculated in the framework of the first Born approximation and incoherently added to the IAM-SCAR results. In comparison with the calculated DCS for the S atom, atomic-like behavior for the angular distributions in both the OCS and CS2 scattering systems is observed. Integrated elastic cross sections are obtained by extrapolating the experimental measurements, with the aid of the theoretical calculations, for those scattering angles below 10° and above 150°. These values are then compared with the available total cross sections. [ABSTRACT FROM AUTHOR]

We report on new measurements for elastic electron scattering from pyrazine. Absolute differential cross sections (DCSs) at seven discrete energies in the range 3-50 eV, and over the scattered electron angular range 10°-129°, were determined using a crossed electron-molecular beam spectrometer in conjunction with the well-established relative flow technique. Integral elastic cross sections were subsequently derived from those DCS data at each energy. Where possible comparison between the present results and those from sophisticated Schwinger multichannel and R-matrix computations is made, with generally quite good quantitative accord being found. Finally, in order to better study some of the rich resonance structure predicted by theory, results from elastic electron excitation functions are presented. [ABSTRACT FROM AUTHOR]

We report absolute elastic differential, integral and momentum transfer cross sections for electron interactions with CCl4. The incident electron energy range is 1.5-100 eV, and the scattered electron angular range for the differential measurements varies from 15°-130°. The absolute scale of the differential cross section was set using the relative flow technique with helium as the reference species. Comparison with previous total cross sections shows good agreement. Atomic-like behaviour in this scattering system is shown here for the first time, and is further investigated by comparing the CCl4 elastic cross sections to recent results on the halomethanes and atomic chlorine at higher impact energies [H. Kato, T. Asahina, H. Masui, M. Hoshino, H. Tanaka, H. Cho, O. Ingólfsson, F. Blanco, G. Garcia, S. J. Buckman, and M. J. Brunger, J. Chem. Phys. 132, 074309 (2010)]. [ABSTRACT FROM AUTHOR]

We report absolute elastic differential, integral, and momentum transfer cross sections for electron interactions with the series of molecules CH3X (X=F, Cl, Br, I). The incident electron energy range is 50–200 eV, while the scattered electron angular range for the differential measurements is 15°–150°. In all cases the absolute scale of the differential cross sections was set using the relative flow method with helium as the reference species. Substitution effects on these cross sections, as we progress along the halomethane series CH3F, CH3Cl, CH3Br, and CH3I, are investigated as a part of this study. In addition, atomic-like behavior in these scattering systems is also considered by comparing these halomethane elastic cross sections to results from other workers for the corresponding noble gases Ne, Ar, Kr, and Xe, respectively. Finally we report results for calculations of elastic differential and integral cross sections for electrons scattering from each of the CH3X species, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements was found to be quite remarkable in each case. [ABSTRACT FROM AUTHOR]

We report experimental results for electron scattering from perfluorocyclobutane, c-C4F8, obtained from measurements in our two laboratories. A set of differential, integral, and momentum transfer cross sections is provided for elastic scattering for incident electron energies from 1.5 to 100 eV. Inelastic scattering (vibrational excitation) cross sections have been measured for incident electron energies of 1.5, 2, 5, 6, and 7 eV. In order to investigate the role of intermediate negative ions (resonances) in the scattering process we have also measured an excitation function for elastic scattering and vibrational excitation of the ground electronic state of C4F8 for incident energies between 0.6 and 20 eV. These results are compared with the limited amount of data available in the literature for scattering from this molecule. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report experimental results for electron scattering from tetrafluoroethylene, C2F4, obtained from measurements in two laboratories. An extensive set of differential, integral, and momentum transfer cross sections is provided for elastic scattering for incident electron energies from 1 to 100 eV and inelastic (vibrational excitation) scattering for incident electron energies at 3, 6, 7.5, 8, and 15 eV, and for scattering angles ranging from 10° to 130°. To highlight the role of intermediate negative ions (resonances) in the scattering process we have also measured excitation functions for elastic scattering and vibrational excitation of the ground electronic state of C2F4 for incident energies between 1.5 and 20 eV. Our results are compared with recent theoretical calculations and a limited number of other experimental results. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A new electron scattering apparatus is developed based on concepts from the positron system built by Surko et al (1988). In an electron version of the system, the electron beam is provided by a cathode and the rest of the system is correspondingly modified to a simpler system. The system was tested by measuring electron scattering from argon to verify its operation. N2O is important in the atmosphere and plasma processes, and in the intermediate energy region from 5 eV to 50 eV, there are two previous results for the electron scattering total cross-section which are in disagreement. We present here a new measurement for the total electron cross-section of N2O, helping to resolve this disagreement. [ABSTRACT FROM AUTHOR]

Excitation coefficients for the production of vibrationally exicted D2 by low energy electrons have been determined from measurements of the intensity of infrared emission from mixtures of D2 and small concentrations of CO2 or CO. The measurements were made using the electron drift tube technique and covered electric field to gas density ratios (E/n) from (5 to 80)×10-21 V m2, corresponding to mean electron energies between 0.45 and 4.5 eV. The CO2 and CO concentrations were chosen to allow efficient excitation transfer from the D2 to the carbon containing molecule, but to minimize direct excitation of the CO2 or CO. The measured infrared intensities were normalized to predicted values for N2–CO2 and N2–CO mixtures at E/n where the efficiency of vibrational excitation is known to be very close to 100%. The experimental excitation coefficients are in satisfactory agreement with predictions based on electron–D2 cross sections at mean electron energies below 1 eV, but are about 50% too high at mean energies above about 2 eV. Application of the technique to H2 did not yield useful vibrational excitation coefficients. The effective coefficients in H2–CO2 mixtures were a factor of about 3 times the predicted values. For our H2–CO mixtures the excitation of CO via excitation transfer from H2 is small compared to direct electron excitation of CO molecules. Published experiments and theories on electron–H2 and electron–D2 collisions are reviewed to obtain the cross sections used in the predictions. [ABSTRACT FROM AUTHOR]