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Title: Measurements of total and inelastic cross sections in positron-Cs and electron-Cs collisions

Abstract

We report measurements of total, positronium (Ps) formation, and excitation cross sections for 0.1-60-eV positrons (e{sup +}'s) and total and excitation cross sections for 6-200-eV electrons (e{sup -}'s) scattered by Cs atoms. Ps formation cross sections are measured by both detecting {gamma} ray coincidences and a beam transmission technique while all other cross sections are measured using beam transmission techniques. We discuss our findings and compare them with other experimental results and theoretical calculations.

Authors:
; ; ; ; ; ;  [1]
  1. Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48202 (United States)
Publication Date:
OSTI Identifier:
20982340
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.75.032720; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOMS; BEAMS; CESIUM; COMPARATIVE EVALUATIONS; COMPUTER CALCULATIONS; CROSS SECTIONS; ELECTRON-ATOM COLLISIONS; ELECTRONS; EV RANGE; EXCITATION; GAMMA RADIATION; POSITRON-ATOM COLLISIONS; POSITRONIUM; POSITRONS; TRANSMISSION

Citation Formats

Surdutovich, E., Kauppila, W. E., Kwan, C. K., Miller, E. G., Parikh, S. P., Price, K. A., and Stein, T. S. Measurements of total and inelastic cross sections in positron-Cs and electron-Cs collisions. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.032720.
Surdutovich, E., Kauppila, W. E., Kwan, C. K., Miller, E. G., Parikh, S. P., Price, K. A., & Stein, T. S. Measurements of total and inelastic cross sections in positron-Cs and electron-Cs collisions. United States. doi:10.1103/PHYSREVA.75.032720.
Surdutovich, E., Kauppila, W. E., Kwan, C. K., Miller, E. G., Parikh, S. P., Price, K. A., and Stein, T. S. Thu . "Measurements of total and inelastic cross sections in positron-Cs and electron-Cs collisions". United States. doi:10.1103/PHYSREVA.75.032720.
@article{osti_20982340,
title = {Measurements of total and inelastic cross sections in positron-Cs and electron-Cs collisions},
author = {Surdutovich, E. and Kauppila, W. E. and Kwan, C. K. and Miller, E. G. and Parikh, S. P. and Price, K. A. and Stein, T. S.},
abstractNote = {We report measurements of total, positronium (Ps) formation, and excitation cross sections for 0.1-60-eV positrons (e{sup +}'s) and total and excitation cross sections for 6-200-eV electrons (e{sup -}'s) scattered by Cs atoms. Ps formation cross sections are measured by both detecting {gamma} ray coincidences and a beam transmission technique while all other cross sections are measured using beam transmission techniques. We discuss our findings and compare them with other experimental results and theoretical calculations.},
doi = {10.1103/PHYSREVA.75.032720},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Theoretical calculations on the total (elastic plus inelastic) cross sections sigma/sub t/ for positron (e/sup +/)-methane collisions are reported at 2--600 eV. We evaluate a complex optical potential (COP) for the e/sup +/-CH/sub 4/ system and treat it exactly in a partial-wave analysis to obtain the S matrix. The real part is composed of an accurate repulsive static potential plus a parameter-free attractive correlation polarization potential. The imaginary part of the COP, V/sub abs/(r), is derived semiempirically in order to reproduce the sharp rise in sigma/sub t/ just above the positronium-formation threshold (E/sub Ps/). This form of V/sub abs/ ismore » a function of target charge density, static plus polarization potential, local kinetic energy of the projectile, Fermi momentum, and the mean excitation energy of the system. Our final e/sup +/-CH/sub 4/ sigma/sub t/ compare very well with measurements in the E/sub Ps/-600-eV region. Below E/sub Ps/, the present results are in good accord with close-coupling calculations of Jain and Thompson and the measurements of Charlton and co-workers. We also test this absorption potential for the e/sup +/-He system and find qualitative agreement with measurements. It is also possible from this model to extract approximate values of the Ps-formation cross sections in the ore gap.« less
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  • We have combined the L = 0 and 1 partial-wave amplitudes obtained by a two-state coupled static approximation with correlation with the L > or = 2 Born amplitudes to obtain the differential cross section for positronium formation in positron--atomic-hydrogen collisions. For positron energies of 0.64 and 0.75 Ry, minima at the scattering angles of 57degree and 51degree are found. Total cross sections for positronium formation for low and intermediate impact energies are given. Measurement of the differential cross section for the process e/sup +/ + He ..-->.. Ps + He/sup +/ for the detection of possible minima is suggested.more » (AIP)« less
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