X-Ray Spectra from Oxygen-Ion Bombardments on Ca and V at 15 MeV

$K$ x-ray spectra of Ca and V as produced by 15-MeV ${\mathrm{O}}^{4+}$ ion bombardment are compared with 6-MeV proton-induced spectra. The $K\alpha$ and $K\beta$ lines from the ${\mathrm{O}}^{4+}$ bombardment are found to be shifted approximately 54 and 157 eV, respectively, relative to the proton-induced spectra. Hartree-Fock-Slater calculations show that the observed shifts are on the order of those expected from atoms with two or three additional innershell vacancies. We argue that it is unlikely that the known low-energy ion-atom interactions could be responsible for such inner-shell ionization configurations.