PHOTOIONIZATION OF NA(NH3)N AND NA(H2O)N CLUSTERS - A STEP TOWARDS THE LIQUID-PHASE

Ionization potentials (IP's) for Na(H2O)n and Na(NH3)n are reported for the first time up to n = 20. As expected, for Na(NH3)n the IP decreases more or less monotonically with decreasing (n + 1)-1/3 to a limit consistent with the bulk value of 1.45 eV. In contrast, for Na(H2O)n we find the IP as a function of (n + 1)-1/3 to be constant at 3.17 eV for n greater-than-or-equal-to 4, close to the bulk value. For comparison we solve a one-electron Schrodinger equation in a dielectrically screened Coulomb potential. While agreement with the experiment is reasonable for small n, this one-center model fails for larger clusters, thus giving some first indication for the existence of two-center localized states in these microclusters.