Charge transfer between alkali cluster ions and atoms in the 1 to 10 keV collisional energy range

The cross-sections for collisional charge transfer between singly charged f ree clusters M-n(+) (M = Li, Na; n = 1...50) and atomic targets A (cesium, potassium) have been measured as a function of collisional relative velocit y in laboratory energy range 1-10 keV. For each cluster size, the experimen tal values of the charge transfer cross-section sigma(nu) are fitted with a n universal parametric curve with two independent parameters sigma(m) and n u(m) the maximum cross-section and the corresponding velocity. For small si ze clusters (n less than or equal to 15), the sigma(nu) characteristic para meters show strong variations with the number of atoms in the cluster. Abru pt dips observed for n = 10 and n = 22 are attributed to electronic propert ies. Charge transfer patterns observed for various collisional systems pres ent similarities, which appear more sensitive to cluster quantum size effec ts than to collision energy defects. In their whole, the sigma(m) and nu(m) , parameters show differences in both their size evolution and their absolu te values discussed in term of projectile and target electronic structures.