MEMORY LOSS AND AUGER PROCESSES IN A MANY-BODY THEORY OF CHARGE-TRANSFER

Charge transfer between hyperthermal alkali atoms and metallic scatter ing surfaces is an experimental and theoretical arena for many-body in teractions. To model new facets, we use a generalized time-dependent N ewns-Anderson Hamiltonian that includes electron spin, multiple atomic orbitals with image shifted levels, intra-atomic Coulomb repulsion, a nd resonant exchange. A variational electronic many-body wave function solves the dynamical problem. The wave function consists of sectors w ith zero and one particle-hole pair and goes beyond earlier work with the inclusion of amplitudes for a neutral atom plus an electron-hole p air. Higher-order sectors with more than one particle-hole pair are su ppressed by powers of 1/N; hence the wave-function ansatz is equivalen t to a 1/N expansion. The equations of motion are integrated numerical ly without further approximation. This solution shows improved loss of memory - the final charge state is independent of the initial one - i n agreement with theoretical and experimental expectations. Understand ing of this phenomenon is deepened through an analysis of entropy prod uction. By studying the independent-particle approximation, and by exa mining the role played by different sectors of the Hilbert space in en tropy production, we arrive at necessary and sufficient conditions for loss of memory to occur in the many-body solution. As further tests o f the theory, we reproduce the experimentally observed peak in the exc ited neutral Li(2p) occupancy at intermediate work functions starting from different initial conditions. Next, we include Auger processes by adding two-body interaction terms to the many-body Hamiltonian. Sever al types of Auger processes are considered, and these are shown to aff ect the final-state occupancies at low work functions because phase sp ace enlarges rapidly as the work function is lowered. Preliminary expe rimental evidence for an upturn in the Li(2p) occupancy at the lowest work functions thus may be explained by Auger transitions. Finally, we comment on the plausibility of observing a signature of the Kondo res onance in charge transfer experiments.