Experimental and theoretical investigations of ionization potentials and structures of mixed sodium lithium clusters

We have measured the ionization potentials (IP) of Nan−mLim clusters (3⩽n⩽21 and 1⩽m⩽3) generated in a supersonic beam. The IPs of mixed clusters are close to the values obtained for pure sodium and pure lithium clusters. They display the features of a metallic system with n delocalized electrons. For clusters containing 2–6 atoms, we have performed density functional theory calculations. The IPs calculated for the lowest-energy structures are in good agreement with experiment. The geometries of the heteronuclear clusters, in particular the 2D–3D transition, are discussed in detail.