X-Ray Production Cross Section for a Thin Solid Be-Target with Light Ions

Abstract

The processes leading to K-x-ray production by slow ion atom collision can, in principle be descirbed by direct Coulomb excitation (Z1 ≪ Z2, Z1 and Z2 being the atomic number of projectile and target, respectively) and by molecular orbital (MO) interaction (Zx ≈ Z2). For details see e.g.1. The latter process usually is discussed as a three step mechanism: Vacancy production in the 2pir MO leading to a vacancy occupation number NΠ in the entrance channel (in general, N<jf is a function of the projectile velocity v: NΠ = NO + NV), vacancy transfer by rotational coupling between the 2pπ and 2pσ MO (σrot) to the K-shell of the lighter collision partner and vacancy sharing in the outgoing part of the collision resulting in a K-vacancy of the heavier collision partner. This concept has successfully been applied to a variety of collision systems2 with excellent agreement between theory and experiment especially for the Ne+ + O system. For lower Z collision partners, however, theory seems to overestimate σrot. Our measurements of the x-ray production cross section ax for thin Be foils with H+, D+, He+, Li+, Be+, B+ cover the region of both the above mentioned excitation processes, giving data for testing these models in the low energy and low Z region.