CHARGE-TRANSFER DYNAMICS OF LOW-ENERGY COLLISIONS OF LI+ WITH ALKALI-COVERED CU(001)

We present measurements of branching ratios to different final states of the scattered particles for 400 eV Li+ ions incident on alkali-covered Cu(001). In particular, we have measured the charge state fractions and the relative yield of excited states in the scattered flux as a function of the adsorbate-induced work function shift. The results of a resonant charge transfer theory which includes excited states, negative ions, and level crossings are compared to the measurements. Qualitative agreement is achieved with the observed work function dependence of both the charge state fractions and the relative yield of Li(2p). In particular, the theory predicts that the peak observed in the Li(2p) yield is due to a competition between the Li(2p) state and the Li-(2s2) state.