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Dalagnol LVS, Moreira GM, Souza Barbosa A, Bettega MHF. Low-Energy Electron and Positron Scattering by para-Difluorobenzene. J Phys Chem A 2023; 127:6486-6494. [PMID: 37526615 DOI: 10.1021/acs.jpca.3c03802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
The Schwinger multichannel method is employed in calculations of the elastic integral and differential cross sections for collisions of low-energy electrons and positrons with para-difluorobenzene (1,4-C6H4F2). The present calculations involving electron scattering have been performed using both static-exchange and static-exchange plus polarization levels of approximation. Our results indicate the presence of three resonances of π*-character in the low-energy region and a fourth resonance, of σ*-character, at higher energy levels. With respect to the positron scattering, the calculations were conducted using the static plus polarization approximation at three different polarization levels. The present calculated electron and positron cross sections show a reasonable agreement with the total cross sections measured by Makochekanwa et al. (J. Phys. B, 2004, 37, 1841). It is also important to highlight that our computed integral cross section for electron scattering indicates the presence of a Ramsauer-Townsend minimum, while the integral cross section for positron scattering indicates the presence of a virtual state.
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Affiliation(s)
- Luiz V S Dalagnol
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Giseli M Moreira
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Alessandra Souza Barbosa
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Márcio H F Bettega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
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2
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Rawlins CM, Hofierka J, Cunningham B, Patterson CH, Green DG. Many-Body Theory Calculations of Positron Scattering and Annihilation in H_{2}, N_{2}, and CH_{4}. PHYSICAL REVIEW LETTERS 2023; 130:263001. [PMID: 37450820 DOI: 10.1103/physrevlett.130.263001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/22/2023] [Indexed: 07/18/2023]
Abstract
The recently developed ab initio many-body theory of positron molecule binding [22J. Hofierka et al., Many-body theory of positron binding to polyatomic molecules, Nature (London) 606, 688 (2022)NATUAS0028-083610.1038/s41586-022-04703-3] is combined with the shifted pseudostates method [A. R. Swann and G. F. Gribakin, Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis, Phys. Rev. A 101, 022702 (2020)PLRAAN2469-992610.1103/PhysRevA.101.022702] to calculate positron scattering and annihilation rates on small molecules, namely H_{2}, N_{2}, and CH_{4}. The important effects of positron-molecule correlations are delineated. The method provides uniformly good results for annihilation rates on all the targets, from the simplest (H_{2}, for which only a sole previous calculation agrees with experiment), to larger targets, where high-quality calculations have not been available.
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Affiliation(s)
- C M Rawlins
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
| | - J Hofierka
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
| | - B Cunningham
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
| | - C H Patterson
- School of Physics, Trinity College Dublin, Dublin 2, Ireland
| | - D G Green
- Centre for Light-Matter Interactions, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
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3
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Seidel EP, Arretche F. Rearrangement Collisions in the Schwinger Variational Principle: A Long-Standing Problem in Positron Scattering Physics. J Phys Chem Lett 2023; 14:2263-2267. [PMID: 36825778 DOI: 10.1021/acs.jpclett.3c00129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
In this letter, we propose a functional on the basis of the Schwinger variational principle that accounts for the particle rearrangement by solving a projected Lippmann-Schwinger equation system. The method is tested in the static-coupled approximation for positron-H, where excellent agreements with benchmark results are found for the elastic, positronium (Ps) formation and annihilation cross sections. The effect of virtual Ps formation is evidenced through the analysis of the annihilation map. A significant increase in the electron-positron density in the vicinity of the atom is obtained.
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Affiliation(s)
- Eliton Popovicz Seidel
- Physics Department, Universidade Federal de Santa Catarina, Florianópolis, 88040-900 Santa Catarina, Brazil
| | - Felipe Arretche
- Physics Department, Universidade Federal de Santa Catarina, Florianópolis, 88040-900 Santa Catarina, Brazil
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Many-Body and Single-Body Low-Energy Elastic Positron Scattering by Beryllium Atoms: From Ab Initio to Semiempirical Approaches. ATOMS 2023. [DOI: 10.3390/atoms11010008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Positron scattering by beryllium atoms in the low-energy range (≤4.0 eV) was studied within ab initio and semiempirical frameworks. When interpreting the static dipole polarizability and the scattering length as representative quantities of the target and positron–atom correlations, the scattering observables obtained in the ab initio calculation were extrapolated by applying a semiempirical approach. Our results ratify previous ones, since no Ramsauer minimum structures or shape resonances were found in the cross sections. The presence of a (e+,Be) bound state was also identified as a function of the dipole polarizability.
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5
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Lima RO, Barbosa AS, Bettega MH, Sanchez SD, Moreira GM. Cross sections for elastic collisions of low-energy positrons with tetrachloroethylene (C 2Cl 4) molecule. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2022.111807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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6
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Barbosa AS. Low-Energy Positron Scattering by Pyridine and Aniline. J Phys Chem A 2022; 126:7924-7929. [DOI: 10.1021/acs.jpca.2c05928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alessandra Souza Barbosa
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, Curitiba, Paraná81531-980, Brazil
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7
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Lozano AI, García-Abenza A, Blanco Ramos F, Hasan M, Slaughter DS, Weber T, McEachran RP, White RD, Brunger MJ, Limão-Vieira P, García Gómez-Tejedor G. Electron and Positron Scattering Cross Sections from CO 2: A Comparative Study over a Broad Energy Range (0.1-5000 eV). J Phys Chem A 2022; 126:6032-6046. [PMID: 36069053 PMCID: PMC9483986 DOI: 10.1021/acs.jpca.2c05005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
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In this Review, we present a comparative study between
electron
and positron scattering cross sections from CO2 molecules
over a broad impact energy range (0.1–5000 eV). For electron
scattering, new total electron scattering cross sections (e-TCS) have
been measured with a high resolution magnetically confined electron
beam transmission system from 1 to 200 eV. Dissociative electron attachment
processes for electron energies from 3 to 52 eV have been analyzed
by measuring the relative O– anion production yield.
In addition, elastic, inelastic, and total scattering cross section
calculations have been carried out in the framework of the Independent
Atom Model by using the Screening Corrected Additive Rule, including
interference effects (IAM-SCARI). Based on the previous cross section
compilation from Itikawa (, 2002, 31, 749−767) and the
present measurements and calculations, an updated recommended e-TCS
data set has been used as reference values to obtain a self-consistent
integral cross section data set for the elastic and inelastic (vibrational
excitation, electronic excitation, and ionization) scattering channels.
A similar calculation has been carried out for positrons, which shows
important differences between the electron scattering behavior: e.g.,
more relevance of the target polarization at the lower energies, more
efficient excitation of the target at intermediate energies, but a
lower total scattering cross section for increasing energies, even
at 5000 eV. This result does not agree with the charge independence
of the scattering cross section predicted by the first Born approximation
(FBA). However, we have shown that the inelastic channels follow the
FBA’s predictions for energies above 500 eV while the elastic
part, due to the different signs of the scattering potential constituent
terms, remains lower for positrons even at the maximum impact energy
considered here (5000 eV). As in the case of electrons, a self-consistent
set of integral positron scattering cross sections, including elastic
and inelastic (vibrational excitation, electronic excitation, positronium
formation, and ionization) channels is provided. Again, to derive
these data, positron scattering total cross sections based on a previous
compilation from Brunger et al. (, 2017, 46, 023102) and the present calculation
have been used as reference values. Data for the main inelastic channels,
i.e. direct ionization and positronium formation, derived with this
procedure, show excellent agreement with the experimental results
available in the literature. Inconsistencies found between different
model potential calculations, both for the elastic and inelastic collision
processes, suggest that new calculations using more sophisticated
methods are required.
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Affiliation(s)
- Ana I Lozano
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain.,Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Adrián García-Abenza
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain
| | - Francisco Blanco Ramos
- Departamento de Estructura de la Materia, Física Térmica y Electrónica e IPARCOS, Universidad Complutense de Madrid, Avenida Complutense, E-28040 Madrid, Spain
| | - Mahmudul Hasan
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Daniel S Slaughter
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Thorsten Weber
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Robert P McEachran
- The Research School of Physics, Australian National University, Canberra, ACT 0200, Australia
| | - Ronald D White
- College of Science and Engineering, James Cook University, Townsville 4810, Australia
| | - Michael J Brunger
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.,Department of Actuarial Science and Applied Statistics, Faculty of Business and Management, UCSI University, Kuala Lumpur 56000, Malaysia
| | - Paulo Limão-Vieira
- Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Gustavo García Gómez-Tejedor
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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Lima RO, Moreira GM, Souza Barbosa A, Bettega MHF, Sanchez SD. Elastic Positron Collisions with 1,1-Difluoroethylene. J Phys Chem A 2021; 125:6949-6953. [PMID: 34370463 DOI: 10.1021/acs.jpca.1c04047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work reports a theoretical investigation on the elastic-positron collision with the 1,1-difluoroethylene molecule for energies up to 10 eV. We have employed the Schwinger multichannel method in the static-plus polarization level of approximation to obtain the integral and differential cross sections. In order to account for the long-range potential due to the permanent dipole moment of the target, the Born-closure procedure has been employed. Also, our present differential cross sections have been applied to estimate a correction to the total cross section measurements available in the literature.
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Affiliation(s)
- Rafael Oliveira Lima
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Giseli Maria Moreira
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Alessandra Souza Barbosa
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | | | - Sergio d'Almeida Sanchez
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
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9
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Cheong Z, Moreira GM, Bettega MHF, Blanco F, Garcia G, Brunger MJ, White RD, Sullivan JP. A comparison of experimental and theoretical low energy positron scattering from furan. J Chem Phys 2020; 153:244303. [PMID: 33380099 DOI: 10.1063/5.0027874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
This paper presents a joint experimental and theoretical study of positron scattering from furan. Experimental data were measured using the low energy positron beamline located at the Australian National University and cover an energy range from 1 eV to 30 eV. Cross sections were measured for total scattering, total elastic and inelastic scattering, positronium formation, and differential elastic scattering. Two theoretical approaches are presented: the Schwinger multichannel method and the independent atom method with screening corrected additivity rule. In addition, our data are compared to corresponding electron scattering results from the same target with a number of significant differences observed and discussed.
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Affiliation(s)
- Z Cheong
- Laser Physics Centre, Research School of Physics, Australian National University, Canberra, Australia
| | - G M Moreira
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - M H F Bettega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - F Blanco
- Departamento de Fısica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, E-28040 Madrid, Spain
| | - G Garcia
- Instituto de Fısica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 113-bis, 28006 Madrid, Spain
| | - M J Brunger
- College of Science and Engineering, Flinders University, Adelaide, SA, Australia
| | - R D White
- College of Science and Engineering, James Cook University, Townsville, Qld., Australia
| | - J P Sullivan
- Laser Physics Centre, Research School of Physics, Australian National University, Canberra, Australia
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10
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Lima RO, Moreira GM, Bettega MHF, Sanchez SD. Low-Energy-Positron Scattering by Acetone. J Phys Chem A 2020; 124:6790-6793. [PMID: 32786658 DOI: 10.1021/acs.jpca.0c05419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report calculations for the elastic collision of low-energy positrons by acetone (C3H6O). For this purpose, the Schwinger multichannel method was used in the static plus polarization approach to calculate cross sections in the energy range from 10-4 to 10 eV. Acetone is a polar molecule, and the effect of the long-range dipole interaction was taken into account through the Born-closure scheme. Our integral cross section was compared with the experimental total cross section results available in the literature, which do not agree among themselves below 2 eV. Our results agree qualitatively well with the most recent experimental data available in all energy regions. Particularly, below the positronium formation channel threshold, when the experimental data are corrected because of the angular resolution of the apparatus, the quantitative agreement is improved.
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Affiliation(s)
- Rafael O Lima
- Departamento de Fı́sica, Universidade Federal do Paraná, Caixa Postal 19044, Curitiba, Paraná 81531-980, Brazil
| | - Giseli M Moreira
- Departamento de Fı́sica, Universidade Federal do Paraná, Caixa Postal 19044, Curitiba, Paraná 81531-980, Brazil
| | - Márcio H F Bettega
- Departamento de Fı́sica, Universidade Federal do Paraná, Caixa Postal 19044, Curitiba, Paraná 81531-980, Brazil
| | - Sergio d'A Sanchez
- Departamento de Fı́sica, Universidade Federal do Paraná, Caixa Postal 19044, Curitiba, Paraná 81531-980, Brazil
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11
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Silva MO, Moreira GM, Bettega MHF, Sanchez SD. Electron and Positron Scattering by the Formamide Molecule. J Phys Chem A 2020; 124:6009-6015. [PMID: 32515965 DOI: 10.1021/acs.jpca.0c03779] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report calculated elastic integral, differential, and momentum transfer cross sections for electron and positron collisions with the formamide (HCONH2) molecule, for impact energies up to 10 eV. We have used the Schwinger multichannel method in the static-exchange and static-exchange plus polarization approximation for collisions of electrons and the static plus polarization approximation for collisions of positrons. The Born-closure procedure was applied to account for the long-range potential due to the permanent dipole moment of formamide. We obtained the well-characterized π* shape resonance located at around 2.38 eV, which belongs to the A″ symmetry of the Cs point group. Our integral and differential cross sections for collisions of electrons were compared with the data available in the literature and showed a good qualitative agreement. To the best of our knowledge, no experimental and theoretical data are currently available for positron-formamide collision, so our present cross sections were compared with the cross sections of formic acid, which is also polar and is isoeletronic to formamide.
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Affiliation(s)
- Murilo O Silva
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Giseli M Moreira
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Márcio H F Bettega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Sergio d'A Sanchez
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
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12
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Abstract
We report elastic integral and differential cross sections for positron collisions with pyrazine (C4H4N2), for energies up to 10 eV. The cross sections were calculated with the Schwinger multichannel method in the static plus polarization approximation. Our computed elastic integral cross section indicates the presence of a Ramsauer-Townsend minimum and a bound state in the Ag scattering symmetry. In the absence of results in the literature on collisions of positrons with pyrazine, we compare the present results with results for pyrimidine and benzene molecules available in the literature.
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Affiliation(s)
- Giseli M Moreira
- Departamento de Fı́sica , Universidade Federal do Paraná , Caixa Postal 19044, 81531-980 Curitiba , Paraná , Brazil
| | - Márcio H F Bettega
- Departamento de Fı́sica , Universidade Federal do Paraná , Caixa Postal 19044, 81531-980 Curitiba , Paraná , Brazil
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13
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Barbosa AS, Bettega MHF. Elastic collisions of low-energy positrons with tetrahydrofuran. J Chem Phys 2019; 150:184305. [DOI: 10.1063/1.5093404] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alessandra Souza Barbosa
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
| | - Márcio H. F. Bettega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-980 Curitiba, Paraná, Brazil
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14
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Nunes FB, Bettega MHF, Sanchez SD. Positron and electron scattering by glycine and alanine: Shape resonances and methylation effect. J Chem Phys 2018; 145:214313. [PMID: 28799345 DOI: 10.1063/1.4968602] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
We report integral cross sections (ICSs) for both positron and electron scattering by glycine and alanine amino acids. These molecules differ only by a methyl group. We computed the scattering cross sections using the Schwinger multichannel method for both glycine and alanine in different levels of approximation for both projectiles. The alanine ICSs are greater in magnitude than the glycine ICSs for both positron and electron scattering, probably due to the larger size of the molecule. In electron scattering calculations, we found two resonances for each molecule. Glycine presents one at 1.8 eV, and another centered at around 8.5 eV, in the static-exchange plus polarization (SEP) approximation. The ICS for alanine shows one resonance at 2.5 eV and another at around 9.5 eV, also in SEP approximation. The results are in good agreement with most of the data present in the literature. The comparison of the electron scattering ICSs for both molecules indicates that the methylation of glycine destabilizes the resonances, shifting them to higher energies.
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Affiliation(s)
- Fernanda B Nunes
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil
| | - Márcio H F Bettega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil
| | - Sergio d'Almeida Sanchez
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil
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Barbosa AS, Pastega DF, Bettega MHF. Low-energy positron scattering by pyrimidine. J Chem Phys 2015; 143:244316. [DOI: 10.1063/1.4938427] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Alessandra Souza Barbosa
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil
| | - Diego F. Pastega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil
| | - Márcio H. F. Bettega
- Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil
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16
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Zecca A, Trainotti E, Chiari L, Bettega MHF, Sanchez SD, Varella MTDN, Lima MAP, Brunger MJ. Positron scattering from the cyclic ethers oxirane, 1,4-dioxane, and tetrahydropyran. J Chem Phys 2012; 136:124305. [PMID: 22462855 DOI: 10.1063/1.3696378] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In this paper we report original measurements of total cross sections (TCSs) for positron scattering from the cyclic ethers oxirane (C(2)H(4)O), 1,4-dioxane (C(4)H(8)O(2)), and tetrahydropyran (C(5)H(10)O). The present experiments focus on the low energy range from ∼0.2 to 50 eV, with an energy resolution smaller than 300 meV. This study concludes our systematic investigation into TCSs for a class of organic compounds that can be thought of as sub-units or moieties to the nucleotides in living matter, and which as a consequence have become topical for scientists seeking to simulate particle tracks in matter. Note that as TCSs specify the mean free path between collisions in such simulations, they have enjoyed something of a recent renaissance in interest because of that application. For oxirane, we also report original Schwinger multichannel elastic integral cross section (ICS) calculations at the static and static plus polarisation levels, and with and without Born-closure that attempts to account for the permanent dipole moment of C(2)H(4)O. Those elastic ICSs are computed for the energy range 0.5-10 eV. To the best of our knowledge, there are no other experimental results or theoretical calculations against which we can compare the present positron TCSs. However, electron TCSs for oxirane (also known as ethylene oxide) and tetrahydropyran do currently exist in the literature and a comparison to them for each species will be presented.
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Affiliation(s)
- A Zecca
- Department of Physics, University of Trento, Povo, I-38123 Trento, Italy
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17
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Gribakin GF, Lee CMR. Positron annihilation in molecules by capture into vibrational Feshbach resonances of infrared-active modes. PHYSICAL REVIEW LETTERS 2006; 97:193201. [PMID: 17155623 DOI: 10.1103/physrevlett.97.193201] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Indexed: 05/12/2023]
Abstract
Enhanced positron annihilation on polyatomic molecules is a long-standing and complex problem. We report the results of calculations of resonant positron annihilation on methyl halides. A free parameter of our theory is the positron binding energy. A comparison with energy-resolved annihilation rates measured for CH3F, CH3Cl, and CH3Br [L. D. Barnes, Phys. Rev. A 74, 012706 (2006)10.1103/PhysRevA.74.012706] shows good agreement and yields estimates of the binding energies.
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Affiliation(s)
- G F Gribakin
- Department of Applied Mathematics and Theoretical Physics, Queen's University, Belfast BT7 1NN, Northern Ireland, United Kingdom.
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18
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Germano JS, Lima MA. Annihilation Dynamics of Positrons in Molecular Environments: Theoretical Study of Low-Energy Positron-C2 H4 Scattering. PHYSICAL REVIEW LETTERS 1996; 77:1028-1031. [PMID: 10062972 DOI: 10.1103/physrevlett.77.1028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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