We have studied the spectrum of x-rays emitted when 130 and 200 keV kinetic energy hydrogen-like argon ions impact silicon dioxide surfaces. Specifically, we were interested in the mechanism for creation of K-shell holes in the silicon target atoms, which can be filled with the release of a 1.75 keV x-ray. Two mechanisms have been hypothesized for the vacancy transfer between the K-shells of silicon and argon atoms: `direct vacancy transfer' and `projectile-decay-product-mediated vacancy transfer'. To separate these mechanisms, we used a target with a metallic coating (preventing close collisions between Si and Ar but allowing x-ray transmission) and a target without such a coating. We found that x-ray photoionization is the dominant mechanism in both cases and measured an upper limit for the contribution from the 'direct mechanism' on the uncoated sample. Furthermore, we measured the relative strengths of the Kα, Kβ and Kγ lines of the argon projectile as a function of kinetic energy and found satisfactory agreement with charge exchange and cascade model calculations.
Citation: Journal of Physics B-Atomic Molecular and Optical Physics
Pub Type: Journals
highly charged ions, surface interactions, vacancy transfer, x-ray spectroscopy