Positronium collisions with rare-gas atoms

Abstract

Abstract. We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method Phys. Rev. A 90 052717] and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (break-up). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps-Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.

Calculations of positronium-atom scattering using a spherical cavity

“…The largest discrepancy in each case is for the P wave. As noted by Gribakin et al [22], the pseudopotential method likely overestimates the P-wave contribution to the scattering, so the present P-wave phase shifts for Ar, Kr, and Xe should be considered superior at this level of approximation. Figure 2 shows the effect of including the van der Waals interaction on the phase shifts.…”

“…Here, the electron-electron and electron-positron correlation effects that make up the van der Waals interaction cannot be described by means of a simple potential. Following Fabrikant and Gribakin [21] and Gribakin et al [22], we treat this problem by introducing an effective cutoff function in the van der Waals potential,…”

“…The phase shifts are negative, which indicates that in the frozen-target approximation the Ps-atom interaction is repulsive. Also shown are the phase shifts from the static-exchange calculations for He [33] and pseudopotential calculations for Ar, Kr, and Xe [21,22].…”

“…2 are static-exchange-with-van-der-Waals phase shifts of Barker and Bransden [30] for He, and pseudopotential calculations with the van der Waals interaction for Ar, Kr, and Xe [21,22]. There is reasonably good agree- for He these are the static-exchange phase shifts of Sarkar and Ghosh [33], for Ar and Kr they are the pseudopotential phase shifts of Fabrikant and Gribakin [21], and for Xe they are the pseudopotential phase shifts of Gribakin et al [22]. ment with these calculations, except for S-wave scattering on Ar and P-wave scattering on Ar and Xe.…”

“…Blackwood et al [49,50] developed a coupled-state treatment for Ps scattering from Ne, Ar, Kr, and Xe in the frozen-target approximation; for Kr and Xe the incident Ps was also frozen in its ground state. Finally, Fabrikant and Gribakin [21] and Gribakin et al [22] employed a pseudopotential method to study low-energy Ps collisions with Ar, Kr, and Xe.…”