The influence of O and C doping on the ionization potentials of Li-clusters

The influence of doping of Li-clusters by electronegative O and C atoms on the ionization potentials was investigated. Experimentally, we report ioniz ation potentials for bare Li-n clusters (10 less than or equal to n less th an or equal to 70) deduced from photoionization efficiency spectra. The val ues are compared with the results for LinO and LinC clusters. Observed diff erences are largely attributed to a quantum size effect caused by the segre gated molecular part around the impurity, which changes the electron work f unction. Theoretically, the Fermi and exchange-correlation energies which e nter the work function, are calculated in the frame of the augmented plane wave (APW) method by taking explicitly into account the presence of the mol ecular core. The other contribution to the work function, the moment of the double layer at the cluster surface, is computed by solving the correspond ing Poisson's equation.