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Stokes PW, Foster SP, Casey MJE, Cocks DG, González-Magaña O, de Urquijo J, García G, Brunger MJ, White RD. An improved set of electron-THFA cross sections refined through a neural network-based analysis of swarm data. J Chem Phys 2021; 154:084306. [PMID: 33639749 DOI: 10.1063/5.0043759] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We review experimental and theoretical cross sections for electron transport in α-tetrahydrofurfuryl alcohol (THFA) and, in doing so, propose a plausible complete set. To assess the accuracy and self-consistency of our proposed set, we use the pulsed-Townsend technique to measure drift velocities, longitudinal diffusion coefficients, and effective Townsend first ionization coefficients for electron swarms in admixtures of THFA in argon, across a range of density-reduced electric fields from 1 to 450 Td. These measurements are then compared to simulated values derived from our proposed set using a multi-term solution of Boltzmann's equation. We observe discrepancies between the simulation and experiment, which we attempt to address by employing a neural network model that is trained to solve the inverse swarm problem of unfolding the cross sections underpinning our experimental swarm measurements. What results from our neural network-based analysis is a refined set of electron-THFA cross sections, which we confirm is of higher consistency with our swarm measurements than that which we initially proposed. We also use our database to calculate electron transport coefficients in pure THFA across a range of reduced electric fields from 0.001 to 10 000 Td.
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Affiliation(s)
- P W Stokes
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia
| | - S P Foster
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia
| | - M J E Casey
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia
| | - D G Cocks
- Research School of Physics, Australian National University, Canberra, ACT 0200, Australia
| | - O González-Magaña
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251 Cuernavaca, Morelos, Mexico
| | - J de Urquijo
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251 Cuernavaca, Morelos, Mexico
| | - G García
- Instituto de Física Fundamental, CSIC, Serrano 113-bis, 28006 Madrid, Spain
| | - M J Brunger
- College of Science and Engineering, Flinders University, Bedford Park, Adelaide SA 5042, Australia
| | - R D White
- College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia
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2
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de Urquijo J, Casey MJE, Serkovic-Loli LN, Cocks DG, Boyle GJ, Jones DB, Brunger MJ, White RD. Assessment of the self-consistency of electron-THF cross sections using electron swarm techniques: Mixtures of THF–Ar and THF–N2. J Chem Phys 2019. [DOI: 10.1063/1.5108619] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J. de Urquijo
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251, Cuernavaca, Morelos, Mexico
| | - M. J. E. Casey
- College of Science and Engineering, James Cook University, Townsville QLD 4811, Australia
| | - L. N. Serkovic-Loli
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251, Cuernavaca, Morelos, Mexico
| | - D. G. Cocks
- College of Science and Engineering, James Cook University, Townsville QLD 4811, Australia
| | - G. J. Boyle
- College of Science and Engineering, James Cook University, Townsville QLD 4811, Australia
| | - D. B. Jones
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia
| | - M. J. Brunger
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia
| | - R. D. White
- College of Science and Engineering, James Cook University, Townsville QLD 4811, Australia
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3
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Abstract
The kinetic theory of non-relativistic positrons in an idealized positron emission tomography PET environment is developed by solving the Boltzmann equation, allowing for coherent and incoherent elastic, inelastic, ionizing and annihilating collisions through positronium formation. An analytic expression is obtained for the positronium formation rate, as a function of distance from a spherical source, in terms of the solutions of the general kinetic eigenvalue problem. Numerical estimates of the positron range - a fundamental limitation on the accuracy of PET, are given for positrons in a model of liquid water, a surrogate for human tissue. Comparisons are made with the ‘gas-phase’ assumption used in current models in which coherent scattering is suppressed. Our results show that this assumption leads to an error of the order of a factor of approximately 2, emphasizing the need to accurately account for the structure of the medium in PET simulations.
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4
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Boyle GJ, McEachran RP, Cocks DG, White RD. Electron scattering and transport in liquid argon. J Chem Phys 2015; 142:154507. [PMID: 25903897 DOI: 10.1063/1.4917258] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann's equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.
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Affiliation(s)
- G J Boyle
- College of Science, Technology & Engineering, James Cook University, Townsville 4810, Australia
| | - R P McEachran
- Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200, Australia
| | - D G Cocks
- College of Science, Technology & Engineering, James Cook University, Townsville 4810, Australia
| | - R D White
- College of Science, Technology & Engineering, James Cook University, Townsville 4810, Australia
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5
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Tattersall WJ, Cocks DG, Boyle GJ, Buckman SJ, White RD. Monte Carlo study of coherent scattering effects of low-energy charged particle transport in Percus-Yevick liquids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:043304. [PMID: 25974609 DOI: 10.1103/physreve.91.043304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Indexed: 06/04/2023]
Abstract
We generalize a simple Monte Carlo (MC) model for dilute gases to consider the transport behavior of positrons and electrons in Percus-Yevick model liquids under highly nonequilibrium conditions, accounting rigorously for coherent scattering processes. The procedure extends an existing technique [Wojcik and Tachiya, Chem. Phys. Lett. 363, 381 (2002)], using the static structure factor to account for the altered anisotropy of coherent scattering in structured material. We identify the effects of the approximation used in the original method, and we develop a modified method that does not require that approximation. We also present an enhanced MC technique that has been designed to improve the accuracy and flexibility of simulations in spatially varying electric fields. All of the results are found to be in excellent agreement with an independent multiterm Boltzmann equation solution, providing benchmarks for future transport models in liquids and structured systems.
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Affiliation(s)
- W J Tattersall
- Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia
- College of Science, Technology and Engineering, James Cook University, Townsville 4810, Australia
| | - D G Cocks
- College of Science, Technology and Engineering, James Cook University, Townsville 4810, Australia
| | - G J Boyle
- College of Science, Technology and Engineering, James Cook University, Townsville 4810, Australia
| | - S J Buckman
- Research School of Physics and Engineering, The Australian National University, Canberra, ACT 0200, Australia
- Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - R D White
- College of Science, Technology and Engineering, James Cook University, Townsville 4810, Australia
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6
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Chiari L, Duque HV, Jones DB, Thorn PA, Pettifer Z, da Silva GB, Limão-Vieira P, Duflot D, Hubin-Franskin MJ, Delwiche J, Blanco F, García G, Lopes MCA, Ratnavelu K, White RD, Brunger MJ. Differential cross sections for intermediate-energy electron scattering from α-tetrahydrofurfuryl alcohol: excitation of electronic-states. J Chem Phys 2014; 141:024301. [PMID: 25028013 DOI: 10.1063/1.4885856] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report on measurements of differential cross sections (DCSs) for electron impact excitation of a series of Rydberg electronic-states in α-tetrahydrofurfuryl alcohol (THFA). The energy range of these experiments was 20-50 eV, while the scattered electron was detected in the 10°-90° angular range. There are currently no other experimental data or theoretical computations against which we can directly compare the present measured results. Nonetheless, we are able to compare our THFA DCSs with earlier cross section measurements for Rydberg-state electronic excitation for tetrahydrofuran, a similar cyclic ether, from Do et al. [J. Chem. Phys. 134, 144302 (2011)]. In addition, "rotationally averaged" elastic DCSs, calculated using our independent atom model with screened additivity rule correction approach are also reported. Those latter results give integral cross sections consistent with the optical theorem, and supercede those from the only previous study of Milosavljević et al. [Eur. Phys. J. D 40, 107 (2006)].
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Affiliation(s)
- L Chiari
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
| | - H V Duque
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
| | - D B Jones
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
| | - P A Thorn
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
| | - Z Pettifer
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
| | - G B da Silva
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
| | - P 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
| | - D Duflot
- Laboratoire de Physique des Lasers, Atomes et Molécules, UMR CNRS 8523, Université Lille, F-59655 Villeneuve d'Ascq Cedex, France
| | - M-J Hubin-Franskin
- Départment de Chimie, Université de Liège, Institut de Chimie-Bât. B6C, B-4000 Liège 1, Belgium
| | - J Delwiche
- Départment de Chimie, Université de Liège, Institut de Chimie-Bât. B6C, B-4000 Liège 1, Belgium
| | - F Blanco
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, Madrid E-28040, Spain
| | - G García
- Instituto de Física Fundamental, CSIC, Madrid E-28006, Spain
| | - M C A Lopes
- Departamento de Física, Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil
| | - K Ratnavelu
- Institute of Mathematical Sciences, University of Malaya, Kuala Lumpur, Malaysia
| | - R D White
- School of Engineering and Physical Sciences, James Cook University, Townsville, 4810 Queensland, Australia
| | - M J Brunger
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
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7
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de Urquijo J, Basurto E, Juárez AM, Ness KF, Robson RE, Brunger MJ, White RD. Electron drift velocities in He and water mixtures: Measurements and an assessment of the water vapour cross-section sets. J Chem Phys 2014; 141:014308. [DOI: 10.1063/1.4885357] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J. de Urquijo
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251, Cuernavaca, Mor., Mexico
| | - E. Basurto
- División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana, Av. San Pablo 180, 02200, México, D.F
| | - A. M. Juárez
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, 62251, Cuernavaca, Mor., Mexico
| | - K. F. Ness
- School of Engineering and Physical Sciences, James Cook University, Townsville 4810, Australia
| | - R. E. Robson
- School of Engineering and Physical Sciences, James Cook University, Townsville 4810, Australia
| | - M. J. Brunger
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
- Institute of Mathematical Sciences, University of Malaya, 5063 Kuala Lumpur, Malaysia
| | - R. D. White
- School of Engineering and Physical Sciences, James Cook University, Townsville 4810, Australia
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8
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Petrović ZL, Marjanović S, Dujko S, Banković A, Malović G, Buckman S, Garcia G, White R, Brunger M. On the use of Monte Carlo simulations to model transport of positrons in gases and liquids. Appl Radiat Isot 2014; 83 Pt B:148-54. [DOI: 10.1016/j.apradiso.2013.01.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 12/29/2012] [Accepted: 01/02/2013] [Indexed: 10/27/2022]
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9
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Low-energy electron and positron transport in gases and soft-condensed systems of biological relevance. Appl Radiat Isot 2014; 83 Pt B:77-85. [DOI: 10.1016/j.apradiso.2013.01.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Revised: 12/30/2012] [Accepted: 01/02/2013] [Indexed: 11/22/2022]
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10
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Jones DB, Bellm SM, Blanco F, Fuss M, García G, Limão-Vieira P, Brunger MJ. Differential cross sections for the electron impact excitation of pyrimidine. J Chem Phys 2013; 137:074304. [PMID: 22920117 DOI: 10.1063/1.4743961] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report on differential cross section (DCS) measurements for the electron-impact excitation of the electronic states of pyrimidine. The energy range of the present measurements was 15-50 eV with the angular range of the measurements being 10°-90°. All measured DCSs displayed forward-peaked angular distributions, consistent with the relatively large magnitudes for the dipole moment and dipole polarizability of pyrimidine. Excitations to triplet states were found to be particularly important in some energy loss features at the lower incident electron energies. To the best of our knowledge there are no other experimental data or theoretical computations against which we can compare the present results.
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Affiliation(s)
- D B Jones
- School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.
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11
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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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12
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Bellm SM, Builth-Williams JD, Jones DB, Chaluvadi H, Madison DH, Ning CG, Wang F, Ma XG, Lohmann B, Brunger MJ. Dynamical (e,2e) studies of tetrahydrofurfuryl alcohol. J Chem Phys 2012; 136:244301. [DOI: 10.1063/1.4729466] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
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13
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Ness KF, Robson RE, Brunger MJ, White RD. Transport coefficients and cross sections for electrons in water vapour: comparison of cross section sets using an improved Boltzmann equation solution. J Chem Phys 2012; 136:024318. [PMID: 22260590 DOI: 10.1063/1.3675921] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This paper revisits the issues surrounding computation of electron transport properties in water vapour as a function of E/n(0) (the ratio of the applied electric field to the water vapour number density) up to 1200 Td. We solve the Boltzmann equation using an improved version of the code of Ness and Robson [Phys. Rev. A 38, 1446 (1988)], facilitating the calculation of transport coefficients to a considerably higher degree of accuracy. This allows a correspondingly more discriminating test of the various electron-water vapour cross section sets proposed by a number of authors, which has become an important issue as such sets are now being applied to study electron driven processes in atmospheric phenomena [P. Thorn, L. Campbell, and M. Brunger, PMC Physics B 2, 1 (2009)] and in modeling charged particle tracks in matter [A. Munoz, F. Blanco, G. Garcia, P. A. Thorn, M. J. Brunger, J. P. Sullivan, and S. J. Buckman, Int. J. Mass Spectrom. 277, 175 (2008)].
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Affiliation(s)
- K F Ness
- ARC Centre for Antimatter-Matter Studies, School of Engineering and Physical Sciences, James Cook University, Townsville 4810, Australia
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14
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Builth-Williams JD, Bellm SM, Jones DB, Chaluvadi H, Madison DH, Ning CG, Lohmann B, Brunger MJ. Experimental and theoretical investigation of the triple differential cross section for electron impact ionization of pyrimidine molecules. J Chem Phys 2012; 136:024304. [PMID: 22260576 DOI: 10.1063/1.3675167] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cross-section data for electron impact induced ionization of bio-molecules are important for modelling the deposition of energy within a biological medium and for gaining knowledge of electron driven processes at the molecular level. Triply differential cross sections have been measured for the electron impact ionization of the outer valence 7b(2) and 10a(1) orbitals of pyrimidine, using the (e, 2e) technique. The measurements have been performed with coplanar asymmetric kinematics, at an incident electron energy of 250 eV and ejected electron energy of 20 eV, for scattered electron angles of -5°, -10°, and -15°. The ejected electron angular range encompasses both the binary and recoil peaks in the triple differential cross section. Corresponding theoretical calculations have been performed using the molecular 3-body distorted wave model and are in reasonably good agreement with the present experiment.
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Affiliation(s)
- J D Builth-Williams
- ARC Centre of Excellence for Antimatter-Matter Studies, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia
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15
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Jones D, Bellm S, Limão-Vieira P, Brunger M. Low-energy electron scattering from pyrimidine: Similarities and differences with benzene. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.03.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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16
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Šašić O, Dujko S, Makabe T, Petrović Z. A set of cross sections and transport coefficients for electrons in HBr. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2011.08.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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17
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White RD, Robson RE. Multiterm solution of a generalized Boltzmann kinetic equation for electron and positron transport in structured and soft condensed matter. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:031125. [PMID: 22060346 DOI: 10.1103/physreve.84.031125] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 08/04/2011] [Indexed: 05/31/2023]
Abstract
In this paper, we generalize the semiclassical Boltzmann kinetic equation for dilute gases to consider highly nonequilibrium electrons and positrons in soft condensed matter, accounting rigorously for all types of interactions, including positronium formation, and allowing for both coherent and incoherent scattering processes. The limitations inherent in the seminal paper of Cohen and Lekner [M. H. Cohen and J. Lekner, Phys. Rev. 158, 305 (1967); Y. Sakai, J. Phys. D 40, R441 (2007)] are avoided by solving the kinetic equation using a "multiterm" spherical harmonic representation of the velocity distribution function, as well as formulating a necessarily nonperturbative treatment of nonconservative collisional processes such as positronium formation. Numerical calculations of transport properties are carried out for a Percus-Yevick model of a hard-sphere system, and for positrons in liquid argon. New phenomena are predicted, including structure-induced negative conductivity and anisotropic diffusion.
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Affiliation(s)
- R D White
- ARC Centre for Antimatter-Matter Studies, School of Engineering and Physical Sciences, James Cook University, Townsville 4810, Australia.
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18
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Do TPT, Leung M, Fuss M, Garcia G, Blanco F, Ratnavelu K, Brunger MJ. Excitation of electronic states in tetrahydrofuran by electron impact. J Chem Phys 2011; 134:144302. [DOI: 10.1063/1.3575454] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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