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3. Statistical Complexity Analysis of Sleep Stages.

Author

Duarte, Cristina D., Pacheco, Marianela, Iaconis, Francisco R., Rosso, Osvaldo A., Gasaneo, Gustavo, and Delrieux, Claudio A.

Subjects
SLEEP stages, CLASSIFICATION algorithms, SLEEP apnea syndromes, SLEEP disorders, NEURODEGENERATION
Abstract

Studying sleep stages is crucial for understanding sleep architecture, which can help identify various health conditions, including insomnia, sleep apnea, and neurodegenerative diseases, allowing for better diagnosis and treatment interventions. In this paper, we explore the effectiveness of generalized weighted permutation entropy (GWPE) in distinguishing between different sleep stages from EEG signals. Using classification algorithms, we evaluate feature sets derived from both standard permutation entropy (PE) and GWPE to determine which set performs better in classifying sleep stages, demonstrating that GWPE significantly enhances sleep stage differentiation, particularly in identifying the transition between N1 and REM sleep. The results highlight the potential of GWPE as a valuable tool for understanding sleep neurophysiology and improving the diagnosis of sleep disorders. [ABSTRACT FROM AUTHOR]

Published
2025
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4. Inertial movements of the iris as the origin of post-saccadic oscillations

Author

Bouzat, Sebastián, Freije, María Luján, Frapiccini, Ana Laura, and Gasaneo, Gustavo

Subjects
Physics - Biological Physics
Abstract

The use of eye-tracking techniques is becoming rapidly extended because of its relevance for acquiring information about cognition and behavior. Recent studies indicate that a correct characterization of the motion of the pupil inside the eyeball is needed, because this motion influences the eye-tracking results. In this work we face this problem and we develop a model that reproduces several findings of recent experiments on saccadic movements. In particular, the dependence of the amplitude and period of the post saccadic oscillations on the saccade size, as well as that of the peak velocity. Our results suggest that post saccadic oscillations could obey mainly to inertial phenomena experimented by the inner part of the iris when the eyeball rotates., Comment: 4 pages, 3 figures

Published
2017
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13. Neuroeducación y funciones ejecutivas. Evaluación y estrategias educativas frente a la regulación emocional en el aula

Author

Betegón Blanca, Elena, Irurtia Muñiz, María Jesús, Gasaneo, Gustavo, Betegón Blanca, Elena, Irurtia Muñiz, María Jesús, and Gasaneo, Gustavo

Abstract

Como se puede comprobar en cualquier etapa de la vida, el ser humano tiene la capacidad innata de adaptarse a las características del entorno para lograr sus necesidades. Sin embargo, debido a la exigencia de una adaptación rápida a los nuevos cambios en el desarrollo y a las demandas culturales de estos últimos años, se ha observado un aumento de distintas alteraciones psicopatológicas, especialmente los Trastornos de Ansiedad (TA) y aquellos relacionados con el estado de ánimo, que afectan directamente al bienestar y funcionamiento de los individuos. Numerosas investigaciones han avalado el auge de este tipo de patologías entre el alumnado, siendo un factor clave la disponibilidad de instrumentos psicométricos que midan la regulación emocional teniendo en cuenta los procesos cognitivos de alto nivel implicados, las denominadas Funciones Ejecutivas (FE). No obstante, a pesar de que la medición psicológica se ha convertido en una de las herramientas más utilizadas actualmente en múltiples ámbitos, muchas de estas pruebas están desfasadas y descontextualizadas debido a la evolución social y las consecuencias que ello conlleva. Todo ello hace reflexionar sobre si los nuevos tiempos requieren de una nueva figura docente o, simplemente, una adaptación de los mismos a nuevas estrategias de enseñanza. Por este motivo es imprescindible la actualización de la formación docente, siendo la Neurociencia aplicada a la educación o Neuroeducación una posible respuesta a estas demandas. Este área de estudio consiste en aprovechar los conocimientos sobre el funcionamiento cerebral para la mejora de la práctica educativa a través de dos vías cerebrales: los procesos atencionales y la influencia del medio. Para poder dar respuesta a lo anteriormente expuesto, inicialmente se plantea que a través de una metodología adaptable, configurada por breves estímulos neuroeducativos en el medio escolar, se pueden mejorar las funciones ejecutivas del alumnado y provocar una disminución de la an, Departamento de Psicología, Doctorado en Investigación Transdisciplinar en Educación

Published
2022

18. Teléfonos inteligentes: su impacto en las capacidades atencionales de niños y jóvenes

Author

Freije, María Luján, Sapognikoff, M., and Gasaneo, Gustavo

Subjects
Astronomía, ATENCIÓN, Ciencias Físicas, MEDIA-MULTITASKING, TELÉFONOS INTELIGENTES, CIENCIAS NATURALES Y EXACTAS, APRENDIZAJE
Abstract

El valor de un desarrollo tecnológico puede ser medido por su penetración y permanencia en la sociedad. Este trae beneficios, pero también conlleva desventajas. Se revisan aspectos asociados a la incorporación social de los teléfonos celulares inteligentes (TCI) junto con otros dispositivos, haciendo foco en niños y jóvenes. Se analiza su influencia en el desarrollo de capacidades atencionales; se discute el proceso de formación de redes cerebrales de atención y factores implicados, y la relación de la atención con el desempeño en el contexto áulico. Fil: Freije, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Sapognikoff, M.. Clínica Privada Bahiense; Argentina Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Published
2017

20. Contribuciones del Rastreo Ocular al Test de Percepción de Diferencias: Un Estudio en Población Universitaria.

Author

del Punta, Jessica A., Betegón, Elena, Gasaneo, Gustavo, Jesús Irurtia, María, and de Luis García, Rodrigo

Subjects
*EYE tracking, *PERCEPTION testing, *EYE movements, *COLLEGE students, *ATTENTION testing
Abstract

Most of the assessment instruments summarize a series of parameters that quantify behavior based on the sense of vision, but do not include physiological measures. The main objective of this research was to record the eye movements of participants by means of an eye tracking device (ET), during the performance of Perception of Differences Test (PDT; CARAS in Spanish) in order to delimit magnitudes such as time or processing speed per item. 44 university students belonging to the Universidad Nacional del Sur in Argentina were evaluated individually, through incidental sampling. A comparative analysis was carried out between the performance in the first 3 minutes and the end of the test, as well as an evaluation of the items grouped by blocks. The results found with the first analysis support the hypothesis that the subjects who need more information to solve the test perform more fixations instead of making longer fixations, and this strategy remains constant throughout the entire task. The second analysis showed an increase in the mean values of resolution times for each item as the resolution of the test progresses, which combined with an increase in the dispersion towards higher values of this characteristic may be an indication of attention fatigue. These findings show that the use of ET in the application of the test provides complementary information that could enhance its evaluation capabilities. [ABSTRACT FROM AUTHOR]

Published
2024
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21. Sturmian bases for two-electron systems in hyperspherical coordinates

Author

UCL - SST/IMCN/NAPS - Nanoscopic Physics, Abdouraman, A., Frapiccini, Ana Laura, Hamido, Aliou, Mota-Furtado, Francisca, O'Mahony, Patrick, Mitnik, Darío, Gasaneo, Gustavo, Piraux, Bernard, UCL - SST/IMCN/NAPS - Nanoscopic Physics, Abdouraman, A., Frapiccini, Ana Laura, Hamido, Aliou, Mota-Furtado, Francisca, O'Mahony, Patrick, Mitnik, Darío, Gasaneo, Gustavo, and Piraux, Bernard

Abstract

We give a detailed account of an ab initio spectral approach for the calculation of energy spectra of two active electron atoms in a system of hyperspherical coordinates. In this system of coordinates, the Hamiltonian has the same structure as the one of atomic hydrogen with the Coulomb potential expressed in terms of a hyperradius and the nuclear charge replaced by an angle dependent effective charge. The simplest spectral approach consists in expanding the hyperangular wave function in a basis of hyperspherical harmonics. This expansion however, is known to be very slowly converging. Instead, we introduce new hyperangular Sturmian functions. These functions do not have an analytical expression but they treat the first term of the multipole expansion of the electron-electron interaction potential, namely the radial electron correlation, exactly. The properties of these new functions are discussed in detail. For the basis functions of the hyperradius, several choices are possible. In the present case, we use Coulomb-Sturmian functions of half integer angular momentum. We show that, in the case of H-, the accuracy of the energy and the width of the resonance states obtained through a single diagonalization of the Hamiltonian, is comparable to the values given by state-of-the-art methods while using a much smaller basis set. In addition, we show that precise values of the electric-dipole oscillator strengths for transitions in helium are obtained thereby confirming the accuracy of the bound state wave functions generated with the present method.

Published
2016

22. Ionization of atomic hydrogen by electrons: the role of the contributions of the pseudo-states in the second Born approximation

Author

Dal Cappello, C., Hmouda, B., Naja, A., and Gasaneo, Gustavo

Subjects
Born approximation, Física Atómica, Molecular y Química, Ciencias Físicas, Coulomb potential, Electron-atom collision, Second order, CIENCIAS NATURALES Y EXACTAS
Abstract

The second Born approximation is often used, particularly when we study double processes such as the ionization?excitation and the double ionization of atoms and molecules by charged particles. But when we apply this approximation, it needs the knowledge of all excited states of the target. In this study, we apply the second Born approximation by using 294 excited and pseudo-states for the ionization of atomic hydrogen by electrons. We compare the results of our model with those given by other models and to all experiments performed with an incident energy of 250 eV. We show that our new version of the second Born approximation gives better agreement than previous versions even for high values of the energy of the ejected electrons (50 eV). Fil: Dal Cappello, C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina; Centre National de la Recherche Scientifique. Unité Mixte de Recherche. Laboratoire Structure et Réactivité des Systèmes Moléculaires Complexes; Francia; Fil: Hmouda, B.. Lebanese University. Doctoral School of Sciences and Technology. Azm Center for Scientific Research; Líbano; Fil: Naja, A.. Lebanese University. Doctoral School of Sciences and Technology. Azm Center for Scientific Research; Líbano; Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina

Published
2013
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23. Correlated n1,3S states for coulomb three-body systems

Author

Ancarani, L. U., Rodriguez, Karina Viviana, and Gasaneo, Gustavo

Subjects
Astronomía, EXOTIC STATES, KATO CUSP CONDITIONS, EXOTIC SYSTEMS, Ciencias Físicas, THREE-BODY BOUND STATES, CORRELATED STATES, EXCITED STATES, CIENCIAS NATURALES Y EXACTAS
Abstract

n1,3S (n = 1 - 4) states for atomic three-body systems are studied with the Angular Correlated Configuration Interaction method. A recently proposed angularly correlated basis set is used to construct, simultaneously and with a single diagonalization, ground and excited states wave functions which: (i) satisfy exactly Kato cusp conditions at the two-body coalescence points; (ii) involve only linear parameters; (iii) show a fast convergency rate for the energy; and (iv) form an orthogonal set. The efficiency of the method is illustrated by the study a variety of three-body atomic systems [m 1- m 2- m 3z 3+] with two negatively charged light particles, with diverse masses m 1- and m 2-, and a heavy positively charged nucleus m 3z 3+. The calculated ground 11S and excited n1,3S (n = 2 - 4) state energies are compared with those given in the literature, when available. © 2011 Wiley Periodicals, Inc. Fil: Ancarani, L. U.. Université Paul Verlaine-Metz; Francia Fil: Rodriguez, Karina Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Published
2011
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24. A general method to obtain sturmian functions for continuum and bound state problems with coulomb interactions

Author

Frapiccini, Ana Laura, Randazzo, Juan Martin, Gasaneo, Gustavo, and Colavecchia, Flavio Dario

Subjects
PHASE SHIFT, Astronomía, STURMIAN FUNCTION, CRITICAL CHARGE, Ciencias Físicas, SCATTERING, CIENCIAS NATURALES Y EXACTAS
Abstract

In this article, we investigate discretization schemes to represent Sturmian functions for both positive and negative energies in the presence of a long range Coulomb potential.We explore two methods to obtain Sturmian functions for positive energy. The first one involves the expansion of the radial wave function in a L2 finite basis set, whereas the second one introduces the discretization of the radial coordinate domain of the Hamiltonian or, alternatively, the Green function. We apply them to find the bound states and scattering phase shift for N-electron atoms close to the critical charge. Both methods are able to describe bound states near threshold, as well as continuum states with very good convergence properties. Fil: Frapiccini, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Randazzo, Juan Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Física; Argentina Fil: Colavecchia, Flavio Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Published
2010
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25. Derivatives of any order of the hypergeometric function pFq(a1, ..., ap; b1, ..., bq; z) with respect to the parameters ai and bi

Author

Ancarani, L.U. and Gasaneo, Gustavo

Subjects
Gauss functions, Matemáticas, CIENCIAS NATURALES Y EXACTAS, Hypergeometric Functions, Matemática Pura
Abstract

The derivatives of any order of the general hypergeometric function pFq(a1.....ap; b1.....bq;z) with respect to the parameters a; or bj are expressed, in compact form, in terms of generalizations of multivariable Kampe de Feriet functions. To achieve this, use is made of Babister's solution to nonhomogeneous differential equations for pFq(a1.....ap; b1.....bq;z). An application to Hahn polynomials, which are 3F2 functions, is given as an illustration. Fil: Ancarani, L.U.. Université Paul Verlaine-Metz; Francia Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Física; Argentina

Published
2010
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26. Derivatives of any order of the Gaussian hypergeometric function 2F1( a,b,c;z) with respect to the parameters a, b and c

Author

Ancaran, L. U. and Gasaneo, Gustavo

Subjects
Astronomía, Gauss function, Ciencias Físicas, 2F1 function, CIENCIAS NATURALES Y EXACTAS, Hypergeometric
Abstract

The derivatives to any order of the Gaussian hypergeometric function 2F1(a, b, c; z) with respect to the parameters a, b and c are expressed in terms of generalizations of multivariable Kampé de Fériet functions. Several properties are presented. In an application to the two-body Coulomb scattering problem, the usefulness of these derivatives is illustrated with the study of the charge dependence of Pollaczek-like polynomials. Fil: Ancaran, L. U.. Université Paul Verlaine-Metz; Francia Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Published
2009
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27. (e,3e) processes on two-electron atoms: Cusp conditions and scaling law

Author

Ancarani, L. U., Dal Cappello, C., Charpentier, I., Rodriguez, Karina Viviana, and Gasaneo, Gustavo

Subjects
Astronomía, purl.org/becyt/ford/1 [https], Ciencias Físicas, Cusp conditions, purl.org/becyt/ford/1.3 [https], CIENCIAS NATURALES Y EXACTAS, Electron impact
Abstract

We study the double ionization by electron impact of the ground state of heliumlike atoms and propose a scaling law for fully differential (e,3e) cross sections. Within the first Born approximation, cross sections are calculated with a three-body Coulomb (3C) double-continuum wave function and initial states represented by highly accurate wave functions, which satisfy all two-body Kato cusp conditions. We first consider the helium atom in the kinematical and geometrical conditions of the only absolute, high incident energy, experimental data available: our calculations confirm unambiguously that satisfying or not Kato cusp conditions is not a relevant feature of the ground state. Other heliumlike atoms are then considered. Under similar conditions, cross sections for H- are much larger than for helium while the reverse is true for positive ions; a comparison with the rare other theoretical calculations is performed. Finally, within our theoretical framework, we propose an approximate scaling law for (e,3e) cross sections for heliumlike positive ions, and confirm it by calculations. © 2008 The American Physical Society. Fil: Ancarani, L. U.. Université Paul Verlaine-Metz; Francia Fil: Dal Cappello, C.. Université Paul Verlaine-Metz; Francia Fil: Charpentier, I.. Centre National de la Recherche Scientifique; Francia Fil: Rodriguez, Karina Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina

Published
2008
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28. Sturmian functions in a L2 basis: critical nuclear charge for n-electron atoms

Author

Frapiccini, Ana Laura, Gasaneo, Gustavo, Colavecchia, Flavio Dario, and Mitnik, Dario Marcelo

Subjects
Ciencias Físicas, Otras Ciencias Físicas, Sturmians, CIENCIAS NATURALES Y EXACTAS
Abstract

Two particle Sturmian functions [M. Rotenberg, Ann. Phys., NY 19 (1962) 262; S.V. Khristenko, Theor. Math. Fiz. 22 (1975) 31 (Engl. Transl. Theor. Math. Phys. 22, 21)] for a short range potentials are obtained by expanding the solution of the Schrodinger equation in a finite ¨ L2Laguerretype basis. These functions are chosen to satisfy certain boundary conditions, such as regularity at the origin and the correct asymptotic behavior according to the energy domain: exponential decay for negative energy and outgoing (incoming or standing wave) for positive energy. The set of eigenvalues obtained is discrete for both positive and negative energies. This Sturmian basis is used to solve the Schrodinger equation for ¨ a one-particle model potential [A.V. Sergeev, S. Kais, J. Quant. Chem. 75 (1999) 533] to describe the motion of a loosely bound electron in a multielectron atom. Values of the two parameters of the potential are computed to represent the Helium isoelectronic series and the critical nuclear charge Zc is found, in good agreement with previous calculations. Fil: Frapiccini, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Colavecchia, Flavio Dario. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mitnik, Dario Marcelo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Published
2007

29. An eikonal approach for the atomic photoelectric effect on H-like atoms

Author

Otranto, Sebastián, Gasaneo, Gustavo, and Alberdi, E.D.

Subjects
purl.org/becyt/ford/1 [https], Física Atómica, Molecular y Química, PHOTOIONIZATION, Ciencias Físicas, COULOMB WAVE FUNCTIONS, purl.org/becyt/ford/1.3 [https], CIENCIAS NATURALES Y EXACTAS
Abstract

Most quantum mechanics textbooks introduce the atomic photoelectric effect expressing the final continuum state in the high energy limit as a plane wave. This approximation has shown to give clear differences between gauges though. In this work, we show that an approximation based on the asymptotic limit of the exact wave function for the final state leads to better results whether form of the interaction Hamiltonian is used as the photon energy increases. This asymptotic eikonal approximation leads to the exact result in velocity gauge for increasing photon energies, evidencing the relevance of the Coulomb potential even at large distances. Gran parte de los textos de mecánica cuántica introducen el efecto fotoeléctrico expresando la función de onda para el estado final en el límite de altas energías como una onda plana. Sin embargo, esta aproximación conduce a resultados que dependen de la norma utilizada para el calculo de la amplitud de transición. En este trabajo se muestra que una aproximación basada en el limite asintótico de la función de onda exacta para el estado final, conduce a mejores resultados independientemente de la forma del hamiltoniano de interacción utilizado a medida ´ que se incrementa la energía del fotón. Esta aproximación asintótica eikonal conduce al resultado exacto en la norma de velocidad para altas energías del fotón incidente, evidenciando la relevancia del potencial coulombiano a grandes distancias. Fil: Otranto, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Gasaneo, Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Alberdi, E.D.. Universidad Nacional del Sur. Departamento de Física; Argentina

Published
2004

30. Numerical evaluation of Appell´s F1 hypergeometric function

Author

Colavecchia, Flavio Dario, Gasaneo, Gustavo, and Miraglia, Jorge Esteban

Subjects
Física Atómica, Molecular y Química, Ciencias Físicas, hypergeometric function, CIENCIAS NATURALES Y EXACTAS
Abstract

In this work we present a numerical scheme to compute the two-variable hypergeometric function F1(α,β,β′,γ;x,y) of Appell for complex parameters α,β,β′ and γ, and real values of the variables x and y. We implement a set of analytic continuations that allow us to obtain the F1 function outside the region of convergence of the series definition. These continuations can be written in terms of the Horn's G2 function, Appell's F2 function related, and the F1 hypergeometric itself. The computation of the function inside the region of convergence is achieved by two complementary methods. The first one involves a single-index series expansion of the F1 function, while the second one makes use of a numerical integration of a third order ordinary differential equation that represents the system of partial differential equations of the F1 function. We briefly sketch the program and show some examples of the numerical computation. Fil: Colavecchia, Flavio Dario. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gasaneo, Gustavo. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Miraglia, Jorge Esteban. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Published
2001

31. Ionization dynamics of a model atom exposed to a strong laser pulse andrelativistic calculation of matrix elements for two-photon transitions in hydrogen-like ions

Author

UCL - SST/IMCN/IMCN - Institute of Condensed Matter and Nanosciences, Piraux, Bernard, Kwato Njock, Moise Godefroy, Defrance, Pierre, Philippe, Antoine, Popov Vladimirovich, Yuri, Bachau, Henri, Gasaneo, Gustavo, Tetchou Nganso, Hugues Merlain, UCL - SST/IMCN/IMCN - Institute of Condensed Matter and Nanosciences, Piraux, Bernard, Kwato Njock, Moise Godefroy, Defrance, Pierre, Philippe, Antoine, Popov Vladimirovich, Yuri, Bachau, Henri, Gasaneo, Gustavo, and Tetchou Nganso, Hugues Merlain

Abstract

Part I: Recent calculations of ionization rate based on the numerical solution of the time-dependent Schrödinger equation (TDSE) in configuration space gave results in disagreement with the ionization rate obtained under the strong field approximation(SFA), is to say, assuming that the ionization is by tunneling. Moreover, recent experimental results, which clearly show among other things, (a) the presence of resonant structures in the region of low energy spectrum of emitted electrons and (b) interference figures for the distribution of moments of electrons emitted cannot be explained in the context of the SFA. These findings reinforce the idea that the electrons, at least those of low energies, are emitted by another process than the tunnel effect. Under these conditions, the influence of the Coulomb potential compared to the electric field remains high even in the strong field limit. To analyze the role of the Coulomb potential, we developed a new mathematical model that goes beyond the SFA as well as the efficient numerical codes that allow obtaining relevant information on the role of atomic structure in the dynamics of ionization. Part II: Using Sturmian expansions of the Dirac-Coulomb Green's functions derived by R. Szmytkowski (J. Phys. B: At. Mol. Opt. Phys. 30, 825 (1997), fully relativistic treatment) and us (quasirelativistic approach), we have derived in a rigorous way the explicit expressions of the two-photon absorption, Rayleigh and Raman scattering probability amplitudes that take into account both relativistic and retardation effects. A distinctive feature of our tensor treatment is that the expressions derived are quite general and could be applied to any multipole of the two-photon bound-bound transitions. An illustration of our method is undertaken by computing the two-photon absorption transition rates from the ground state towards the excited states of L and M shells for the lighter elements to the heavier ones. A comparison is made also with, (PHYS 3) -- UCL, 2010

Published
2010

33. Ionization dynamics of a model atom exposed to a strong laser pulse andrelativistic calculation of matrix elements for two-photon transitions in hydrogen-like ions

Author

Tetchou Nganso, Hugues Merlain, UCL - SST/IMCN/IMCN - Institute of Condensed Matter and Nanosciences, Piraux, Bernard, Kwato Njock, Moise Godefroy, Defrance, Pierre, Philippe, Antoine, Popov Vladimirovich, Yuri, Bachau, Henri, and Gasaneo, Gustavo

Abstract

Part I: Recent calculations of ionization rate based on the numerical solution of the time-dependent Schrödinger equation (TDSE) in configuration space gave results in disagreement with the ionization rate obtained under the strong field approximation(SFA), is to say, assuming that the ionization is by tunneling. Moreover, recent experimental results, which clearly show among other things, (a) the presence of resonant structures in the region of low energy spectrum of emitted electrons and (b) interference figures for the distribution of moments of electrons emitted cannot be explained in the context of the SFA. These findings reinforce the idea that the electrons, at least those of low energies, are emitted by another process than the tunnel effect. Under these conditions, the influence of the Coulomb potential compared to the electric field remains high even in the strong field limit. To analyze the role of the Coulomb potential, we developed a new mathematical model that goes beyond the SFA as well as the efficient numerical codes that allow obtaining relevant information on the role of atomic structure in the dynamics of ionization. Part II: Using Sturmian expansions of the Dirac-Coulomb Green's functions derived by R. Szmytkowski (J. Phys. B: At. Mol. Opt. Phys. 30, 825 (1997), fully relativistic treatment) and us (quasirelativistic approach), we have derived in a rigorous way the explicit expressions of the two-photon absorption, Rayleigh and Raman scattering probability amplitudes that take into account both relativistic and retardation effects. A distinctive feature of our tensor treatment is that the expressions derived are quite general and could be applied to any multipole of the two-photon bound-bound transitions. An illustration of our method is undertaken by computing the two-photon absorption transition rates from the ground state towards the excited states of L and M shells for the lighter elements to the heavier ones. A comparison is made also with the quasirelativistic treatment. The numerical results obtained enable us to draw inferences as to the improvements of our method. (PHYS 3) -- UCL, 2010

Published
2010

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