Positronium breakup versus hydrogen ionization in collisions with fast charged projectiles: a comparative study

TL;DR

This study compares positronium breakup and hydrogen ionization in collisions with fast projectiles, highlighting how mass differences affect the spectra and cross sections in the weak perturbation regime.

Contribution

It provides a detailed analysis of how mass effects influence collision outcomes for positronium versus hydrogen in a specific velocity regime.

Findings

Positronium has smaller binding energy, leading to smaller momentum transfers.

Constructive interference increases breakup probability in positronium.

Hydrogen ionization is less affected by projectile-electron interactions due to the heavy nucleus.

Abstract

We perform a comparative study of the breakup of positronium and ionization of atomic hydrogen by projectile-nuclei in the weak perturbation collision regime, $Z_p e_0^2/\hbar \ll v < c $ ($v$ is the collision velocity, $Z_p$ the projectile atomic number, $e_0$ the elementary charge and $c$ the speed of light). In this regime the only principal difference between the collisions with these atomic systems lies in the masses of their positively charged constituents. We have shown that the corresponding mass effects strongly influence the spectra of the target fragments and the total cross sections. This influence manifests itself via i) the significantly smaller binding energy in positronium resulting in smaller momentum transfers necessary to break the system, ii) a strong constructive interference between the inelastic scattering of the projectile on the electron and the positron in collisions with positronium that also increases the chances for the breakup and iii) the "passive" role of the hydrogen nucleus caused by its heavy mass that prohibits hydrogen ionization to proceed via the interaction between the projectile and the nucleus.