IONIZATION-POTENTIALS OF TANTALUM CLUSTERS WITH 3 TO 64 ATOMS

The threshold ionization potentials for Ta3-64 and Ta11O have been obtained from their photoionization efficiency spectra. The results show substantial variation in the ionization potentials as a function of n (number of atoms per cluster) for n < 20. The ionization potentials for two isomers of Ta12 have also been measured. A comparison of the results to the spherical drop model has shown poor agreement. This is thought to result from the failure of the spherical drop model to include the developing geometrical and electronic structure of the clusters with increasing size. Bond dissociation energies for Ta2-4 have also been estimated.