We have studied the spectrum of x-rays emitted when 130 and 200 keV kineticenergy hydrogen-like argon ions impact silicon dioxide surfaces.Specifically, we were interested in the mechanism for creationof K-shell holes in the silicon target atoms, which can befilled with the release of a 1.75 keV x-ray. Two mechanisms havebeen hypothesized for the vacancy transfer between the K-shellsof silicon and argon atoms: `direct vacancy transfer' and`projectile-decay-product-mediated vacancy transfer'. Toseparate these mechanisms, we used a target with a metalliccoating (preventing close collisions between Si and Ar butallowing x-ray transmission) and a target without such acoating. We found that x-ray photoionization is the dominantmechanism in both cases and measured an upper limit for thecontribution from the `direct mechanism' on the uncoatedsample. Furthermore, we measured the relative strengths of theKα, Kβ and Kγ lines of the argonprojectile as a function of kinetic energy and foundsatisfactory agreement with charge exchange and cascade modelcalculations.