Solid-gas effect in K-vacancy production in near symmetric slow heavy-ion-atom collisions.

We have measured the target thickness dependence of K-vacancy production probabilities and total cross sections for 40.6 MeV Ar ions hitting Ca and Cu targets. The probabilities were measured as a function of the scattering angle between 0.13° and 1.4° by means of a K x-ray-particle coincidence. By integrating the measured probabilities over the impact parameter a significantly lower total cross section was obtained than the directly measured value. The maximum seen in the impact parameter dependent probability varies with decreasing target thickness towards the results obtained with molecular and atomic gas targets. From these observations a multiple collision L-vacancy process prior to 2 pπ-2 pσ rational coupling is concluded. [ABSTRACT FROM AUTHOR]