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Deep Minimum and a Vortex for Positronium Formation in Low-Energy Positron-Helium Collisions. ATOMS 2021. [DOI: 10.3390/atoms9030056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We find a zero in the positronium formation scattering amplitude and a deep minimum in the logarithm of the corresponding differential cross section for positron–helium collisions for an energy just above the positronium formation threshold. Corresponding to the zero, there is a vortex in the extended velocity field that is associated with this amplitude when one treats both the magnitude of the momentum of the incident positron and the angle of the scattered positronium as independent variables. Using the complex Kohn variational method, we determine accurately two-channel K-matrices for positron–helium collisions in the Ore gap. We fit these K-matrices using both polynomials and the Watanabe and Greene’s multichannel effective range theory taking into account explicitly the polarization potential in the Ps-He+ channel. Using the fitted K-matrices we determine the extended velocity field and show that it rotates anticlockwise around the zero in the positronium formation scattering amplitude. We find that there is a valley in the logarithm of the positronium formation differential cross section that includes the deep minimum and also a minimum in the forward direction.
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Shipman M, Armitage S, Beale J, Brawley SJ, Fayer SE, Garner AJ, Leslie DE, Van Reeth P, Laricchia G. Absolute Differential Positronium-Formation Cross Sections. PHYSICAL REVIEW LETTERS 2015; 115:033401. [PMID: 26230792 DOI: 10.1103/physrevlett.115.033401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Indexed: 06/04/2023]
Abstract
The first absolute experimental determinations of the differential cross sections for the formation of ground-state positronium are presented for He, Ar, H2, and CO2 near 0°. Results are compared with available theories. The ratio of the differential and integrated cross sections for the targets exposes the higher propensity for forward emission of positronium formed from He and H2.
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Affiliation(s)
- M Shipman
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - S Armitage
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - J Beale
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - S J Brawley
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - S E Fayer
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - A J Garner
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - D E Leslie
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - P Van Reeth
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - G Laricchia
- UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
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Charlton M, Griffith TC, Heyland GR, Lines KS, Wright GL. The energy dependence of positronium formation in gases. ACTA ACUST UNITED AC 1999. [DOI: 10.1088/0022-3700/13/24/005] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Laricchia G, Charlton M, Davies SA, Beling CD, Griffith TC. The production of collimated beams of o-Ps atoms using charge exchange in positron-gas collisions. ACTA ACUST UNITED AC 1999. [DOI: 10.1088/0022-3700/20/3/006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Igarashi A, Toshima N, Shirai T. Hyperspherical coupled-channel calculations of positronium formation in low-energy positron-helium collisions. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1996; 54:5004-5009. [PMID: 9914067 DOI: 10.1103/physreva.54.5004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Zafar N, Laricchia G, Charlton M, Garner A. Positronium-argon scattering. PHYSICAL REVIEW LETTERS 1996; 76:1595-1598. [PMID: 10060469 DOI: 10.1103/physrevlett.76.1595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Roy U, Mandal P. Positronium formation using the multichannel Schwinger variational principle. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 48:233-242. [PMID: 9909592 DOI: 10.1103/physreva.48.233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Sperber W, Becker D, Lynn KG, Raith W, Schwab A, Sinapius G, Spicher G, Weber M. Measurement of positronium formation in positron collisions with hydrogen atoms. PHYSICAL REVIEW LETTERS 1992; 68:3690-3693. [PMID: 10045772 DOI: 10.1103/physrevlett.68.3690] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Sarkar NK, Basu M, Ghosh AS. Positronium formation in the n=1 and n=2 states in e+-He scattering. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1992; 45:6887-6890. [PMID: 9907815 DOI: 10.1103/physreva.45.6887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Mandal CR, Mandal M, Mukherjee SC. Excited-state positronium formation from positron-atomic-hydrogen collisions. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1991; 44:2968-2974. [PMID: 9906296 DOI: 10.1103/physreva.44.2968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Nahar SN. Positronium formation during scattering of positrons by hydrogen atoms. PHYSICAL REVIEW. A, GENERAL PHYSICS 1989; 40:6231-6237. [PMID: 9902012 DOI: 10.1103/physreva.40.6231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Tripathi S, Sinha C, Sil NC. Positronium formation in the ground and n=2 levels in an e+-H collision. PHYSICAL REVIEW. A, GENERAL PHYSICS 1989; 39:2924-2930. [PMID: 9901585 DOI: 10.1103/physreva.39.2924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Schultz DR, Olson RE. Single-electron-removal processes in collisions of positrons and protons with helium at intermediate velocities. PHYSICAL REVIEW. A, GENERAL PHYSICS 1988; 38:1866-1876. [PMID: 9900588 DOI: 10.1103/physreva.38.1866] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Deb NC, McGuire JH, Sil NC. Positronium formation from He, Be, C, O, and Ne by the impact of high-energy positrons. PHYSICAL REVIEW. A, GENERAL PHYSICS 1987; 36:1082-1087. [PMID: 9898965 DOI: 10.1103/physreva.36.1082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Fromme D, Kruse G, Raith W, Sinapius G. Partial cross-section measurements for ionization of helium by positron impact. PHYSICAL REVIEW LETTERS 1986; 57:3031-3034. [PMID: 10033936 DOI: 10.1103/physrevlett.57.3031] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Diana LM, Coleman PG, Brooks DL, Pendleton PK, Norman AD. Positronium formation cross sections in He and H2 at intermediate energies. PHYSICAL REVIEW. A, GENERAL PHYSICS 1986; 34:2731-2737. [PMID: 9897588 DOI: 10.1103/physreva.34.2731] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Humberston J. Positronium—its Formation and Interaction with Simple Systems. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/s0065-2199(08)60333-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
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Ohsaki A, Watanabe T, Nakanishi K, Iguchi K. Classical-trajectory Monte Carlo calculation for collision processes of e++(e-p) and micro++( micro-p). PHYSICAL REVIEW. A, GENERAL PHYSICS 1985; 32:2640-2644. [PMID: 9896399 DOI: 10.1103/physreva.32.2640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Ma QC, Cheng XX, Liu ZH, Liu YY, Watanabe T. First-order Born and first-order distorted-wave Born cross sections for micro++( micro-p)-->( micro+ micro-)+p. PHYSICAL REVIEW. A, GENERAL PHYSICS 1985; 32:2645-2649. [PMID: 9896400 DOI: 10.1103/physreva.32.2645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Khan P, Mazumdar PS, Ghosh AS. Positronium formation in the n=2 level in positron scattering from hydrogen and helium atoms. PHYSICAL REVIEW. A, GENERAL PHYSICS 1985; 31:1405-1414. [PMID: 9895640 DOI: 10.1103/physreva.31.1405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Stein TS, Kauppila WE. Positron—Gas Scattering Experiments. ADVANCES IN ATOMIC AND MOLECULAR PHYSICS 1982. [DOI: 10.1016/s0065-2199(08)60239-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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