Angular dependence of K-shell ionization in ion-atom collisions

K-shell ionization probabilities P/sub K/ in 0.6--2-MeV p+Cu, p+Mo, and p+Ag and 0.92--2.56-MeV/amu O+Cu, O+Zr, O+Ag, and O+Pb collisions were measured at scattering angles theta between 90 and 1250. Large-solid-angle, plastic-scintillator detectors were used to detect scattered particles. The measured ionization probabilities were fitted to the expression P/sub K/(theta) = A(1+Bcostheta). Factors affecting values of B in various theories of K-shell ionization are discussed. The measured B values are compared with two models: an atomic model which approximates the electronic wave functions with atomic united-atom wave functions centered on the heavier nucleus and a molecular model which uses atomic wave functions of varying charge and center, optimized by minimizing the electronic energies. The present data agree best with the atomic model for proton collisions and the molecular model for oxygen collisions