Similarities and differences in e±–molecule scattering: Applications of the Schwinger multichannel method

Arretche, Felipe; Costa, Romarly F. da; Sanchez, S. d’A.; Hisi, Andreia; Oliveira, Eliane M. de; Varella, Márcio T. do N.; Lima, Marco A. P.

doi:10.1016/j.nimb.2006.01.032

Cited by 19 publications

(11 citation statements)

References 39 publications

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“…In this energy region there are a broad range of reported results, both experimental and theoretical, which are in apparent disagreement with each other, with the recent results of the Trento group [8] noticeably higher than any other calculation or measurement. Figure 1 shows the state of theoretical and experimental results for the total scattering cross section for positron-H 2 scattering before the present experimental program was undertaken, including a range of theory and experiment [7,[9][10][11][12][13][14][15][16][17]. It does not incorporate our present measurements and the very recent convergent-close-coupling (CCC) theory of Zammit et al [18].…”

Section: Introductionmentioning

confidence: 98%

“…Experimental data: black circles, Zecca et al [8]; open circles, Hoffman et al [5]; open squares, Charlton et al [7]; small circles, Sullivan et al [9]; solid squares, Zhou et al [15]. Theoretical data: dash-dotted line, Gibson et al [16]; solid line, Armour et al [10]; dotted line, Reid et al [17]; long-short line, Arretche et al [11]; long-short line, Mukherjee et al [12]; dash-dot-dotted line, Danby et al [13], dashed line, Gianturco et al [14]. The vertical dashed line indicates the threshold energy for the formation of positronium at 8.643 eV.…”

Section: Introductionmentioning

confidence: 99%

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Positron scattering from molecular hydrogen

et al. 2013

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We present results for total and partial cross sections for positron scattering from H 2 . The total scattering and positronium formation cross sections are reported between 0.5 and 200 eV. Total quasielastic and inelastic scattering cross sections are reported for energies between the positronium formation threshold and 50 eV, with quasielastic differential scattering cross sections reported at 1, 3, 5, 7, and 10 eV. Our results are compared with previous work, both experimental and theoretical, with particular attention paid to the region below the positronium formation threshold, where there are apparent discrepancies in previous work. A discussion of possible reasons for discrepancies between this and previous work is presented, including a focus on known systematic effects in the experimental results.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Positron scattering from molecular hydrogen

et al. 2013

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“…Theoretical approaches to positron scattering with molecules have traditionally focused on the low-energy region, where the R matrix [7,8], Schwinger multichannel [9], and complex Kohn variational [10] methods have been applied with considerable success. Also, the single-channel complex model potential method of [11] produced some good results at low and intermediate energies.…”

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confidence: 99%

“…At energies below the Ps-formation threshold, there is very good agreement between the l max = 8 CCC results and a number of previous theoretical models. These include the R matrix with pseudostates (MRMPS) calculations of Zhang et al [7], Schwinger multichannel calculations of Arretche et al [9], and various first-order methods [20,21]. For clarity of presentation, in Fig.…”

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confidence: 99%

Convergent-close-coupling formalism for positron scattering from molecules

2013

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The ab initio convergent-close-coupling method has been extended to positron-molecule collisions within the adiabatic (fixed-nuclei) approximation. Application to molecular hydrogen at energies from 0.1 to 1000 eV has yielded convergent total ionization and grand total cross sections over most of the energy range. We find that very large calculations are required for convergence, even in the case of low-energy elastic scattering, due to the effects of positronium formation. In general, the comparison with experiment is good.

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“…On the theoretical side, few calculations of cross sections for excitation of H 2 by positron impact have been reported. For example, Lino et al [5] reported integral cross sections (ICS) for excitation of the B 1 + u state using the Schwinger multichannel (SMC) method, Arretche et al [6,7] reported the same B 1 + u state using again the SMC method, and Lino [8,9] using the SBP approach reported cross sections for the B 1 + u and C 1 Π u states. With the advance of quantum mechanical computational methods, some very accurate ab initio calculations as the close-coupling, the R-matrix method, complex Kohn and Schwinger multichannel method were performed for positron scattering and these significant efforts were published by Surko et al [4].…”

Section: Introductionmentioning

confidence: 99%

Excitations of H2 by positron impact

Lino

2023

Rev. Mex. Fís.

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In this paper, we present a theoretical study of scattering cross sections for positron impact of electronic states of hydrogen molecule (H2) using the scaling Born positron (SBP) approach. Cross sections to low-lying electronic states, B1∑+u, C1Пu, B´1 ∑+u, and D1Пu are investigated. In an earlier theoretical effort [J.L.S.Lino, Rev. Mex. Fisica 62 (2016) 596], an application of the SBP approach for the X1∑+g - > B1∑+u electronic excitation of the H2 molecule, gave cross sections with reasonable qualitative agreement with experimental data [J.P.Sullivan et. al., Phys.Rev.Lett.87,073201 (2001)]. However, recent studies for the excitation of the B1∑+u state by positron impact showed that this electronic state still demand of a refined degree of description of the quality of the cross sections (Weiss et. al., Eur. Phys. J. D (2018) 72). The purpose of this work was to reexamine the B1∑+u state and verify the quality of the numerical convergence of SBP method and extend the investigation to other states. The possibility to estimate a indirect contribution of multichannel effects ( three states considering the ground X1, B1∑+u and E,F1∑+u state) are introduced within the SBP context. For the first time, integral cross sections to these new states using the SBP approach are reported. In the absence of the experimental data and theoretical developments, comparisons are made with analogous electron scattering.

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Similarities and differences in e±–molecule scattering: Applications of the Schwinger multichannel method

Cited by 19 publications

References 39 publications

Positron scattering from molecular hydrogen

Positron scattering from molecular hydrogen

Convergent-close-coupling formalism for positron scattering from molecules

Excitations of H2 by positron impact

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