Characteristic K X-ray production in heavy ion-atom collisions in solids

Abstract

We report on some of the factors influencing the characteristic K X-ray yields which result from heavy ( Z 1 ∼ 35) ion bombardment of similar atomic number targets ( Z 2). All targets are in the form of narrow, shallow distributions implanted into solid hosts. At the beam energies used, viz. 2 to 4 MeV, K-vacancy production is presumed to arise from a collision sequence, the first producing a projectile L-shell vacancy in a projectile-host atom encounter and the second, a projectile-target atom encounter, transferring the L-vacancy via transient MO orbitals to the K-shell of one of the heavy collision partners. Evidence for a two-step process is presented. First, Kr K X-ray excitation functions measured for Kr ++ bombardment of Si(Kr) and Be(Kr) targets are identical in shape. The different magnitudes are attributed to different efficiencies for Kr 2p-shell ionization in KrSi and KrBe collisions. Second, systematic variation of the host material for fixed ( Z 1, Z 2) demonstrates clearly the role of level matching effects between the projectile-2p and host-1s energy levels in creating projectile 2p-vacancies.