Evidence for ResidualK-Shell Excitation in Chlorine Ions Penetrating Carbon

Chlorine ions at 70 and 140 MeV energy impinge upon ∼1-μg/${\mathrm{cm}}^2$ Cu targets, in one case after emerging from a carbon prefoil and in the second striking Cu on the back side of a carbon foil. The latter approach leads to an appreciable increase in the Cu $K$ x-ray yield, an effect which is explained in terms of residual Cl $K$-shell excitation and which is in accord with a simple model of competing rearrangement processes.