Differential cross sections of positron–hydrogen collisions

Abstract

We make a detailed study on the angular differential cross sections of positron-hydrogen collisions by using the momentum-space coupled-channels optical (CCO) method for incident energies below the H ionization threshold. The target continuum and the positronium (Ps) formation channels are included in the coupled-channels calculations via a complex equivalent-local optical potential. The critical points, which show minima in the differential cross sections, as a function of the scattering angle and the incident energy are investigated. The resonances in the angular differential cross sections are reported for the first time in this energy range. The effects of the target continuum and the Ps formation channels on the different cross sections are discussed.

Plasma-screening effects on positronium formation

“…Positronium (Ps) formation, which is a special rearrangement process in positron-atom collision, has been found to significantly affect the scattering process for low projectile energies in a vacuum. [21][22][23][24][25][26][27][28][29][30] As the screening effect increases in Debye plasmas, the Ps-formation threshold decreases, which results in a more important Ps process at low scattering energies. Moreover, the rate of Ps plays a decisive role in the rate of annihilation and measurement of the spectrum and distribution of the annihilation radiation can provide us with fruitful information to develop our understanding regarding the physical properties of the plasma medium.…”