Excited state positronium collisions with the noble gases

Calculations of the discrete positronium (Ps) transition Ps(2s) → Ps(2p) in collisions with the ground state noble gases helium, argon and xenon are presented at total and single differential levels. For collisions where the target atom is not excited or ionized the impulse approximation (IA) is used. For collisions where the target is excited or ionized the first Born approximation (FBA) is used. For this latter case the Hartley–Walters approximation is used to sum over all possible final atom states.