A COMPARISON OF PHOTOELECTRON-SPECTROSCOPY AND 2-PHOTON IONIZATION SPECTROSCOPY - EXCITED-STATES OF AU-2, AU-3, AND AU-4

Photoelectron spectra of Au-n(-) with n = 2-4 are reported. Due to the relatively high photon energy used in our experiment (h nu = 6.424 eV) and the energy resolution of about 50 meV, various transitions into excited states of the neutral clusters are resolved. It is demonstrated that photoelectron spectra can serve as a map of the electronic states of a cluster, while the high resolution of the resonant two-photon ionization (R2PI) method gains information about the symmetry of the states. The comparison with similar data of Ag-n(-) clusters indicates the influence of relativistic effects and the large spin-orbit splitting for Au.