Total cross section measurements for positron and electron scattering on molecular hydrogen between 8 and 400 eV

Abstract

An apparatus for the measurement of positron and electron total cross sections on gases is described. The low-energy positrons are produced by moderating high-energy positrons from beta -decay sources. The authors used a 11C positron source, produced at a proton accelerator and, alternatively, a 22Na source, combined with various moderators. For electron measurements the secondary electrons originating from the moderator are used. The beam transport system consists of electrostatic lenses and a weak magnetic lens located in the middle of the gas cell. The discrimination against forward scattering is characterised by a cut-off angle of about 6 degrees . The authors' e+-H2 and e--H2 data are compared with the results of recent measurements of similar accuracy performed at University College, London, and Wayne State University (Detroit), and with other e--H2 data. The agreement is satisfactory.

Convergent-close-coupling formalism for positron scattering from molecules

“…At the very lowest energies, we expect that agreement with the experiment of Zecca et al [22] will improve when the missed scattering to forward angles is accounted for. Above the ionization threshold, there is good agreement between the CCC results and all available experiments [22][23][24][25][26][27]. Though not shown, there is also good agreement with the first-order calculations of Reid et al [11].…”

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

“…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.…”

Total (elastic and inelastic) scattering cross sections for several positron-molecule systems at 10–5000 eV:H2,H2Baluja1, Jain2 1992Phys. Rev. A5013503View full textAdd to dashboardCite

“…The experimental data are from Refs. [2] (+), [3] ( O ), and [1] (2). M V"(r)= f p(r, )~rr,~' dr,g Z, .~r -R,T he V~" is calculated in the positron-correlationpolarization (PCOP) approximation recently proposed by one of the authors [33 -35].…”