Measurements of total and positronium formation cross sections for positrons and electrons scattered by hydrogen atoms and molecules

Scattering of low- to intermediate-energy positrons from molecular hydrogen

“…The experimental points are a combination of different experiments for measurements of inelastic processes made at common, or nearly common, impact energies. The inelastic processes in H 2 for which experimental cross sections are available include ionization by positron impact [29,30], excitation by positron impact [31], and positronium formation [22,29]. The present results show good ageement with the experimental cross sections in the region of overlap.…”

“…The experimental measurements of the total cross sections have been made by several groups. In particular, the positron impact energies ranging from 1 to 500 eV are covered by Hoffmann et al [21], from 1.5 to 301 eV by Zhou et al [22], from 14 to 600 eV by Charlton et al [23], from 2.15 to 20.84 eV by Charlton et al [24], and from 8 to 400 eV by Deuring et al [25]. To the best of our knowledge, no other theoretical calculations of total cross sections have been able to predict the stucture in this curve over as large a range of positron energies as in the present calculations.…”

“…2 are the "maximum errors" as reported in Refs. [21,22] and not just the statistical uncertainties. Error bars for the other experimental data are not shown as the errors reported were not of comparable detail.…”

“…(5)- (8), is developed specifically for positron scattering. Raizada and Baluja [4], in addition, use the approximation that molecular hydrogen can be treated as a set of two independent atoms which clearly breaks down at [29]; the circles are for positronium formation by Zhou et al [22] plus first ionization by Ashley et al [30] plus excitation to the B 1 ⌺ state by Sullivan et al [31].…”

Application of exterior complex scaling to positron-hydrogen collisions including rearrangement

“…Measurements of the positronium formation, breakup and total cross sections of this collision include Jones et al ͓9͔ and Zhou et al ͓10,11͔, while calculations that consider both the positronium and breakup channels include the R-matrix method ͓12͔, close-coupling method ͓13,14͔, Kohn variation method ͓15͔, time-dependent close-coupling-distorted-wave hybrid method ͓16͔, and convergent close coupling ͓17,18͔.…”