Differential Electron Emission for Single and Multiple Ionization of Argon by 500 eV Positrons

Abstract

Triply differential electron emission cross sections are measured for single ionization of argon by 500 eV positrons. Data are presented for coincidences between projectiles scattered into angles of 3 degrees and electrons with emission energies less than 10 eV that are observed between 45 and 135 degrees along the beam direction. For interpretation, these are compared to cosine squared representations of the binary and recoil lobes which are convoluted over experimental parameters. Singly differential electron emission data for double and triple ionization by positrons are also presented.

CDW theoretical description of the single ionization of argon by positron and electron impact

“…The BCDW results for positron impact as well as the FBA results are compared to the recent experimental data of de Lucio et al [24,25]. Due to the large computation times, the theoretical data have not been convoluted over the reported experimental uncertainties [24]. It can be seen that for low emission energies (<1 eV) the experiment predicts the recoil peak to be more intense.…”

“…2, we present the binary to recoil peak ratio as a function of the emission energy. The BCDW results for positron impact as well as the FBA results are compared to the recent experimental data of de Lucio et al [24,25]. Due to the large computation times, the theoretical data have not been convoluted over the reported experimental uncertainties [24].…”

“…Binary to recoil peak ratio for the emission energies here considered. The experimental data corresponds to de Lucio et al [24].…”

Triply differential ionization of Ar by 500 eV positron and electron impact

“…All of these influence the shapes and magnitudes of the TDCS polar plots. Therefore a detailed model of the electric fields and apparatus geometry was used to convolute "ideal" binary and recoil distributions over these experimental conditions [26]. The results based upon a best fit are the solid curves shown in figure 3.…”

“…For a detailed description of the experimental device the reader is referred to [26] and references therein. In brief, our apparatus consists of a positron beam produced by a 22 Na radioactive source and a tungsten mesh moderator.…”