Interaction of Li+ with Cu and Au

H.HAMOUDI; C.DABLEMONT; EVELINA A. GARCIA; E. GOLDBERG; V.A. ESAULOV

Hans Merensky Wildlife State , South Africa

Congreso; 23rd International Conference on Atomic Collisions in Solids ( ICACS-23); 2008

ICACS

Results of an experimental and theoretical study of Li+ neutralisation on Cu and Au surfaces are presented. In spite of the large workfunctions of these surfaces (4.9 eV for Cu(111), and about 5.4 eV for Au(100) and Au(111)) experiments (see also (1)) show that Li+ (ionization potential of 5.39eV) neutralizes very efficiently. This result is unexpected given the high work function of these surfaces, for which significantly smaller values are expected in a “traditional” picture of a Li+ ion departing from the surface, in which it is always assumed that close to the surface the Li level is shifted above the Fermi level because of image potential effects.  Our theoretical analysis for the Li-Cu system, actually shows that at distances less than 4 atomic units from the Cu surface the Li (2s) level is  shifted below the Fermi level due to a balance between repulsive and attractive short-range interactions (electron-electron, nuclei-electrons), as it is also observed for Li-HOPG system (2). This fact leads to efficient neutralisation and the final Li° neutral fraction is determined by survival on the outgoing path of the atom trajectory. These results will be presented and discussed.   (1) A R Canário, T Kravchuk and V A Esaulov New J. Phys. 8 (2006) 227 (2) F. Bonetto et al., (in preparation).