K vacancy production in medium-Z heavy ion collisions

During slow encounters between projectile and target atoms, the electronic atomic wave functions of the two collision partners distort and form molecular orbitals (MOs). K vacancy formation in slow heavy-ion collisions, which occur when electrons are excited out of the 2psigma and 1ssigma MOs, is considered. Experimental work using 200 MeV Kr ions is described. The main interest is the excitation of electrons from the 1ssigma MO. The 1ssigma vacancy production is only observed in very asymmetric collisions: as Kr K x rays in encounters with target atoms between H and Ar, and as target K x rays in encounters with atoms between Ce and U. Theoretical approximate calculations of 1ssigma ionization cross sections are described. (JFP