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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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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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Study of Electron and Positron Elastic Scattering from Hydrogen Sulphide Using Analytically Obtained Static Potential. ATOMS 2020. [DOI: 10.3390/atoms8040083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A detailed study of elastic scattering of electrons and positrons from a hydrogen sulphide (H2S) molecule is presented using the method of partial wave phase shift analysis with suitably chosen complex optical potentials. The important aspect of our present work is that we uniquely obtain static potential in an analytical form and use it along with exchange (only for electron), polarization and purely imaginary absorption potentials to define the complex optical potential. The static potential is evaluated by obtaining charge density from the H2S molecule using the molecular wavefunction represented through an accurate analytical form of the Gaussian orbitals. The primary aim of our study is to test our present approach, as applied to the electron and positron scattering from H2S. Therefore, the results for electron and positron impact differential, integral, momentum-transfer, absorption and total cross sections are obtained for the incident energies in the range of 10–500 eV. Comparisons of these different types of cross section results with the available measurements and other calculations show good agreement, which suggests the applicability of our present approach.
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Abstract
Positron impact scattering cross-sections for pyridine and pyrimidine are reported here. Spherical complex optical potential formalism is used to calculate the positronium formation, elastic, total, and differential cross-sections. The ionization cross-sections calculated here are obtained employing the complex scattering potential-ionization contribution method. To account for the complex molecular structure of the target, an effective potential method is employed in our formalism for the first time. The contribution from rotational excitation is also included, which shows a reasonable comparison with the experimental data. The results obtained using the modified approach are encouraging and show very good agreement with the measurements. The differential cross-section for pyridine is reported for the first time.
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Affiliation(s)
- Nidhi Sinha
- Atomic and Molecular Physics Lab, Department of Physics, Indian Institute of Technology (Indian School of Mines) Dhanbad, Dhanbad, Jharkhand 826004, India
| | - Aloka Kumar Sahoo
- Department of Physics, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India
| | - Bobby Antony
- Atomic and Molecular Physics Lab, Department of Physics, Indian Institute of Technology (Indian School of Mines) Dhanbad, Dhanbad, Jharkhand 826004, India
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Abstract
A review on the positron scattering from atoms and molecules is presented in this article. The focus on positron scattering studies is on the rise due to their presence in various fields and application of cross section data in such environments. Positron scattering is usually investigated using theoretical approaches that are similar to those for electron scattering, being its anti-particle. However, most experimental or theoretical studies are limited to the investigation of electron and positron scattering from inert gases, single electron systems and simple or symmetric molecules. Optical potential and polarized orbital approaches are the widely used methods for investigating positron scattering from atoms. Close coupling approach has also been used for scattering from atoms, but for lighter targets with low energy projectiles. The theoretical approaches have been quite successful in predicting cross sections and agree reasonably well with experimental measurements. The comparison is generally good for electrons for both elastic and inelastic scatterings cross sections, while spin polarization has been critical due to its sensitive perturbing interaction. Positron scattering cross sections show relatively less features than that of electron scattering. The features of positron impact elastic scattering have been consistent with experiment, while total cross section requires significant improvement. For scattering from molecules, utilization of both spherical complex optical potential and R-matrix methods have proved to be efficient in predicting cross sections in their respective energy ranges. The results obtained shows reasonable comparison with most of the existing data, wherever available. In the present article we illustrate these findings with a list of comprehensive references to data sources, albeit not exhaustive.
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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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