Foil-thickness dependence of projectile<i>K</i>-satellite x-ray yields in the<i>L</i>-shell nonequilibrium region

Abstract

We have studied projectile K x-ray satellite yields in collisions between 50-MeV ${\mathrm{Ar}}^{\mathit{Q}+}$ ions (Q=4,6,11,12,13) and C foils with various thicknesses (2--100 \ensuremath{\mu}g/${\mathrm{cm}}^{2}$). For foil thicknesses below about 10 \ensuremath{\mu}g/${\mathrm{cm}}^{2}$, Q dependence of the yields has been observed, reflecting the nonimmediate L-shell equilibrium. For this region, it has been shown that the mean K-hole formation cross section also varies with the target thickness and Q. The variation has been attributed to the varying chance of K-to-L excitation with the increase or decrease of L holes in solid. The projectile charge fractions after passage through the target have also been measured for the foil-thickness region 2--20 \ensuremath{\mu}g/${\mathrm{cm}}^{2}$ including the thicknesses for which charge-state equilibrium is not attained. By combining these data, the K-hole formation cross section specifying the number of L holes at the initial stage of a collision has been estimated. The results have been compared with theoretical predictions for cross sections of K-to-continuum ionization and K-to-L excitation.