Espalhamento inelástico de pósitrons por moléculas diatômicas
Autor(a) principal: | |
---|---|
Data de Publicação: | 2023 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) |
Texto Completo: | http://repositorio.ufes.br/handle/10/12638 |
Resumo: | The interaction between electrons and positrons with atoms and molecules has been the subject of extensive theoretical and experimental studies in recent years, as it enables advancements in understanding the dynamic interplay between these particles and matter. When addressing collisions between electrons and positrons with atomic or molecular targets, considering various interaction channels becomes crucial. These channels encompass not only elastic collisions but also excitation channels (electronic, vibrational, rovibrational), ionization, dissociation, and, in the case of positron projectiles, channels related to Positronium formation and annihilation. These two distinct characteristics of positron scattering introduce an additional challenge in the treatment of such systems, particularly from an experimental perspective and given the context of low energies. The experimental analysis, initiated in the 1970s, continues to face challenges, with persistent discrepancies in data. These disparities primarily arise from diculties in producing and controlling incident positron beams, especially at low energies. Theoretical challenges are equally prominent. The interaction between positrons and atomic or molecular targets is described through a positron-target potential that considers three regions: a short-range repulsive region, a long-range attractive region, and an intermediate region involving target correlation and polarization eects. The latter is undoubtedly the region that poses challenges for theorists. The eect of this interaction results from the modication of molecular/atomic charge due to the approach of the projectile and becomes more pronounced as the incident projectile energy decreases. In this context, we propose a theoretical computational approach to construct a potential energy surface (PES) for the interaction between positrons and diatomic molecules. This PES is parametrically dependent on the positron-target distance and, in principle, contains information about the three regions of interest. As a starting point, we employ the Finite Nuclear Mass Correction (FNMC) methodology, which treats the positron as a light nucleus. FNMC has been used in the treatment of positronic systems, particularly in constructing positron-atom interaction potentials with results comparable to the best available experimental data. In this study, we rene the methodology by applying it to positron-molecule systems. The PES is represented by an analytically adjusted function at ab-initio FNMC points, and this potential is used to compute elastic and inelastic cross-sections. The scattering equations are solved using the Close-Coupling (CC) approximation implemented in the computational code MOLSCAT. We apply our methodology to calculate cross-sections for elastic and inelastic scattering (rotational and vibrational) for positron-H2, N2, and O2 systems and compare them with recently reported experimental and theoretical data. As a result, we demonstrate that FNMC represents an alternative model to address the positron scattering problem in homonuclear diatomic molecules, yielding relevant insights into the mechanism of positron-molecule interaction, as electronic target structure information is computed in the PES. Moreover, the potential to obtain cross-sections for elastic and inelastic scattering, considering vibrational and rotational excitation channels using the same interaction potential, becomes highly appealing and applicable to numerous systems. |
id |
UFES_47416f4f4d06cf3a443c6f3f2e69d12a |
---|---|
oai_identifier_str |
oai:repositorio.ufes.br:10/12638 |
network_acronym_str |
UFES |
network_name_str |
Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) |
repository_id_str |
2108 |
spelling |
Espalhamento inelástico de pósitrons por moléculas diatômicasPósitronEspalhamentoSuperfície de energia potencialSeção de choqueFísicaThe interaction between electrons and positrons with atoms and molecules has been the subject of extensive theoretical and experimental studies in recent years, as it enables advancements in understanding the dynamic interplay between these particles and matter. When addressing collisions between electrons and positrons with atomic or molecular targets, considering various interaction channels becomes crucial. These channels encompass not only elastic collisions but also excitation channels (electronic, vibrational, rovibrational), ionization, dissociation, and, in the case of positron projectiles, channels related to Positronium formation and annihilation. These two distinct characteristics of positron scattering introduce an additional challenge in the treatment of such systems, particularly from an experimental perspective and given the context of low energies. The experimental analysis, initiated in the 1970s, continues to face challenges, with persistent discrepancies in data. These disparities primarily arise from diculties in producing and controlling incident positron beams, especially at low energies. Theoretical challenges are equally prominent. The interaction between positrons and atomic or molecular targets is described through a positron-target potential that considers three regions: a short-range repulsive region, a long-range attractive region, and an intermediate region involving target correlation and polarization eects. The latter is undoubtedly the region that poses challenges for theorists. The eect of this interaction results from the modication of molecular/atomic charge due to the approach of the projectile and becomes more pronounced as the incident projectile energy decreases. In this context, we propose a theoretical computational approach to construct a potential energy surface (PES) for the interaction between positrons and diatomic molecules. This PES is parametrically dependent on the positron-target distance and, in principle, contains information about the three regions of interest. As a starting point, we employ the Finite Nuclear Mass Correction (FNMC) methodology, which treats the positron as a light nucleus. FNMC has been used in the treatment of positronic systems, particularly in constructing positron-atom interaction potentials with results comparable to the best available experimental data. In this study, we rene the methodology by applying it to positron-molecule systems. The PES is represented by an analytically adjusted function at ab-initio FNMC points, and this potential is used to compute elastic and inelastic cross-sections. The scattering equations are solved using the Close-Coupling (CC) approximation implemented in the computational code MOLSCAT. We apply our methodology to calculate cross-sections for elastic and inelastic scattering (rotational and vibrational) for positron-H2, N2, and O2 systems and compare them with recently reported experimental and theoretical data. As a result, we demonstrate that FNMC represents an alternative model to address the positron scattering problem in homonuclear diatomic molecules, yielding relevant insights into the mechanism of positron-molecule interaction, as electronic target structure information is computed in the PES. Moreover, the potential to obtain cross-sections for elastic and inelastic scattering, considering vibrational and rotational excitation channels using the same interaction potential, becomes highly appealing and applicable to numerous systems.A interação entre elétrons e pósitrons com átomos e moléculas é alvo de muitos estudos, teóricos e experimentais, nos últimos anos pois possibilita o avanço no entendimento da dinâmica de interação entre essas partículas e a matéria. Ao abordar colisões entre elétrons e pósitrons com alvos moleculares ou atômicos precisamos considerar os diferentes canais de interação, que incluem, além da colisão elástica, os canais de excitação (eletrônica, vibracional, rovibracional), ionização, dissociação e, quando o projétil é um pósitron, os canais de formação de Positrônio e aniquilação. Essas duas características exclusivas do espalhamento por pósitron representam uma diculdade adicional no tratamento destes sistemas, principalmente do ponto de vista experimental e considerando o limite de baixas energias. A análise experimental, iniciada nos anos 1970, ainda enfrenta desaos, com discrepâncias persistentes nos dados. Essas diferenças se devem, principalmente às diculdades observadas na produção e controle do feixe de pósitrons incidente, especialmente em baixas energias. Teoricamente, as diculdades não são menos presentes. A interação entre pósitrons e alvos moleculares ou atômicos são descritos por meio de um potencial pósitron-alvo que levam em conta três regiões: uma região repulsiva de curto alcance, uma região atrativa de longo alcance e uma região intermediária que envolve efeitos de correlação e polarização do alvo. Esta última é, sem dúvida, a região que desaa os teóricos. O efeito desta interação é resultado da modicação da carga molecular/atômica devido à aproximação do projétil e deve ser maior quanto menor for a energia do projétil incidente. Neste contexto, propomos uma abordagem teórico computacional para a construção de uma superfície de energia potencial (SEP) para a interação pósitron-moléculas diatômicas, dependente parametricamente da distância pósitron-alvo e que, em princípio, contém informação sobre as três regiões de interesse. Como ponto de partida, usamos a metodologia Finite Nuclear Mass Correction (FNMC) que trata o pósitron como um núcleo leve. A FNMC vem sendo usada no tratamento de sistemas positrônicos, em especial, na construção de potenciais de interação pósitron-átomos com resultados comparáveis aos melhores dados experimentais disponíveis. Nesta tese, aperfeiçoamos a metodologia ao aplicá-la em sistemas pósitron-moléculas. A SEP é representada por uma função analítica ajustada nos pontos abinitio FNMC e este potencial é usado para obter as seções de choque elástica e inelástica. As equações de espalhamento são resolvidas usando a aproximação Close-Coupling (CC) implementas no código computacional MOLSCAT. Aplicamos nossa metodologia no cálculo das seções de choque de espalhamento elástico e inelástico (rotacional e vibracional) para os sistemas pósitron-H2, N2 e O2 e comparamos com os dados experimentais e teóricos reportados recentemente. Como resultado, mostramos que a FNMC representa um modelo alternativo para tratar o problema do espalhamento de pósitrons por moléculas diatômicas homonucleares com resultados relevantes na compreensão do mecanismo de interação pósitron-molécula diatômica, uma vez que toda informação acerca da estrutura eletrônica do alvo é computada na SEP. Além disso, a possibilidade de se obter as seções de choque de espalhamento elástico e inelástico, considerando canais de excitação vibracional e rotacional, usando o mesmo potencial de interação se torna extremamente atraente e aplicável a um grande número de sistemas.Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Federal do Espírito SantoBRDoutorado em FísicaCentro de Ciências ExatasUFESPrograma de Pós-Graduação em FísicaGonçalves, Sergio Vitorino de Borbahttps://orcid.org/0000000285709750http://lattes.cnpq.br/4992784379693871https://orcid.org/0000000300786149http://lattes.cnpq.br/9304290305117688Lopes, Maria Cristina AndreolliArretche, FelipeCanal Neto, Antôniohttp://lattes.cnpq.br/9283775492064031Scopel, Wanderla Luishttps://orcid.org/0000000220918121http://lattes.cnpq.br/1465127043013658Mota, Vinicius Candidohttps://orcid.org/0000000183680803http://lattes.cnpq.br/4038237972209273Calvino, Luis Argel PovedaPinheiro, Jenifer Geribola2024-05-29T20:55:34Z2024-05-29T20:55:34Z2023-09-29info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisTextapplication/pdfhttp://repositorio.ufes.br/handle/10/12638porinfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)instname:Universidade Federal do Espírito Santo (UFES)instacron:UFES2024-08-23T09:00:39Zoai:repositorio.ufes.br:10/12638Repositório InstitucionalPUBhttp://repositorio.ufes.br/oai/requestopendoar:21082024-08-23T09:00:39Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) - Universidade Federal do Espírito Santo (UFES)false |
dc.title.none.fl_str_mv |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
title |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
spellingShingle |
Espalhamento inelástico de pósitrons por moléculas diatômicas Pinheiro, Jenifer Geribola Pósitron Espalhamento Superfície de energia potencial Seção de choque Física |
title_short |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
title_full |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
title_fullStr |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
title_full_unstemmed |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
title_sort |
Espalhamento inelástico de pósitrons por moléculas diatômicas |
author |
Pinheiro, Jenifer Geribola |
author_facet |
Pinheiro, Jenifer Geribola |
author_role |
author |
dc.contributor.none.fl_str_mv |
Gonçalves, Sergio Vitorino de Borba https://orcid.org/0000000285709750 http://lattes.cnpq.br/4992784379693871 https://orcid.org/0000000300786149 http://lattes.cnpq.br/9304290305117688 Lopes, Maria Cristina Andreolli Arretche, Felipe Canal Neto, Antônio http://lattes.cnpq.br/9283775492064031 Scopel, Wanderla Luis https://orcid.org/0000000220918121 http://lattes.cnpq.br/1465127043013658 Mota, Vinicius Candido https://orcid.org/0000000183680803 http://lattes.cnpq.br/4038237972209273 Calvino, Luis Argel Poveda |
dc.contributor.author.fl_str_mv |
Pinheiro, Jenifer Geribola |
dc.subject.por.fl_str_mv |
Pósitron Espalhamento Superfície de energia potencial Seção de choque Física |
topic |
Pósitron Espalhamento Superfície de energia potencial Seção de choque Física |
description |
The interaction between electrons and positrons with atoms and molecules has been the subject of extensive theoretical and experimental studies in recent years, as it enables advancements in understanding the dynamic interplay between these particles and matter. When addressing collisions between electrons and positrons with atomic or molecular targets, considering various interaction channels becomes crucial. These channels encompass not only elastic collisions but also excitation channels (electronic, vibrational, rovibrational), ionization, dissociation, and, in the case of positron projectiles, channels related to Positronium formation and annihilation. These two distinct characteristics of positron scattering introduce an additional challenge in the treatment of such systems, particularly from an experimental perspective and given the context of low energies. The experimental analysis, initiated in the 1970s, continues to face challenges, with persistent discrepancies in data. These disparities primarily arise from diculties in producing and controlling incident positron beams, especially at low energies. Theoretical challenges are equally prominent. The interaction between positrons and atomic or molecular targets is described through a positron-target potential that considers three regions: a short-range repulsive region, a long-range attractive region, and an intermediate region involving target correlation and polarization eects. The latter is undoubtedly the region that poses challenges for theorists. The eect of this interaction results from the modication of molecular/atomic charge due to the approach of the projectile and becomes more pronounced as the incident projectile energy decreases. In this context, we propose a theoretical computational approach to construct a potential energy surface (PES) for the interaction between positrons and diatomic molecules. This PES is parametrically dependent on the positron-target distance and, in principle, contains information about the three regions of interest. As a starting point, we employ the Finite Nuclear Mass Correction (FNMC) methodology, which treats the positron as a light nucleus. FNMC has been used in the treatment of positronic systems, particularly in constructing positron-atom interaction potentials with results comparable to the best available experimental data. In this study, we rene the methodology by applying it to positron-molecule systems. The PES is represented by an analytically adjusted function at ab-initio FNMC points, and this potential is used to compute elastic and inelastic cross-sections. The scattering equations are solved using the Close-Coupling (CC) approximation implemented in the computational code MOLSCAT. We apply our methodology to calculate cross-sections for elastic and inelastic scattering (rotational and vibrational) for positron-H2, N2, and O2 systems and compare them with recently reported experimental and theoretical data. As a result, we demonstrate that FNMC represents an alternative model to address the positron scattering problem in homonuclear diatomic molecules, yielding relevant insights into the mechanism of positron-molecule interaction, as electronic target structure information is computed in the PES. Moreover, the potential to obtain cross-sections for elastic and inelastic scattering, considering vibrational and rotational excitation channels using the same interaction potential, becomes highly appealing and applicable to numerous systems. |
publishDate |
2023 |
dc.date.none.fl_str_mv |
2023-09-29 2024-05-29T20:55:34Z 2024-05-29T20:55:34Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://repositorio.ufes.br/handle/10/12638 |
url |
http://repositorio.ufes.br/handle/10/12638 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
Text application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Federal do Espírito Santo BR Doutorado em Física Centro de Ciências Exatas UFES Programa de Pós-Graduação em Física |
publisher.none.fl_str_mv |
Universidade Federal do Espírito Santo BR Doutorado em Física Centro de Ciências Exatas UFES Programa de Pós-Graduação em Física |
dc.source.none.fl_str_mv |
reponame:Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) instname:Universidade Federal do Espírito Santo (UFES) instacron:UFES |
instname_str |
Universidade Federal do Espírito Santo (UFES) |
instacron_str |
UFES |
institution |
UFES |
reponame_str |
Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) |
collection |
Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) |
repository.name.fl_str_mv |
Repositório Institucional da Universidade Federal do Espírito Santo (riUfes) - Universidade Federal do Espírito Santo (UFES) |
repository.mail.fl_str_mv |
|
_version_ |
1818368053597962240 |