Positron impact ionization of atomic hydrogen

Abstract

Ionization cross sections for positrons impacting on atomic hydrogen have been measured for kinetic energies in the range 15-700 eV. This has been done in a crossed-beam geometry where a magnetically guided positron beam intersects a hydrogen gas jet emanating from a radio frequency discharge tube. Electron impact ionization cross sections were also measured with the same apparatus thus facilitating comparison with, and normalization to, published results. The positron-atomic hydrogen results are found to be significantly lower than those obtained by Spicher et al. (1990).

The Physics of Positron Annihilation in the Solar Atmosphere

“…He þ Ps, which were treated in x 2.2.) The cross section for impact ionization of H was measured by Jones et al (1993) from threshold to 700 eV and confirmed by Hoffman et al (1997). These results are significantly lower than those of Spicher et al (1990), which were used by Wallyn et al (1994) in their study of annihilation in the ISM.…”

Calculation of the total and total ionization cross sections for positron scattering on atomic hydrogen

“…We base this belief on the fact that the CCC method is able to obtain quantitative agreement with the total ionization cross section for electron impact of atomic hydrogen [2], and that the model to which CCC has been employed is valid whenever the Ps formation cross section is negligible [6], which has been found to be the case above 100 eV by Sperber et al [7]. We therefore conclude that in this energy range the recent measurements of Jones et al [8] are likely to be the most accurate. Agreement with the total cross-section measurements down to 30 eV indicates that the model does not immediately break down once the Ps formation cross section is no longer negligible.…”

Local Epitaxial Growth of (103) One-Axis-Oriented SrBi2Ta2O9 Thin Films Prepared at Low Deposition Temperature by Metalorganic Chemical Vapor Deposition and Their Electrical Properties

“…In figure 2, the results are illustrated using the experimental results for H (Jones et al 1993), He and Ar (Moxom et al 1996), Ne, Kr and Xe (Kara et al 1997). The uncertainties concerning the absolute magnitude of the ionization cross sections of the inert gases by positron-and electron-impact (see Van Reeth et al 2002, Sorokin et al 1998 are irrelevant to the present discussion as the data are scaled to their peak value.…”