K -shell ionization by low-velocity ions

$K$-shell x-ray---production measurements are reported for protons, deuterons, and alpha particles incident on thin foils of copper, niobium, silver, and antimony. In the velocity range of the experiments, which correspond to 100-600 keV/u, the energy of ionization was as large as 10% of the bombarding energy. The inferred dependence of the excitation process on the projectile mass, atomic number, and energy is compared with theoretical estimates of a low-velocity ionization threshold, the binding effect, and the Coulomb-deflection effect. Precision of measurement is not great enough to discern unambiguously the threshold effect but the binding and Coulomb-deflection effects are clearly distinguished.