ZERO ELECTRON KINETIC-ENERGY SPECTROSCOPY OF AU6-

Zero electron kinetic energy (ZEKE) spectroscopy and photodetachment cross section measurements have been carried out on Au6-. The transition frequencies of ZEKE peaks and resonance peaks are nearly identical, consistent with the proposal that the excited negative ion of Au6 has a geometry quite similar to that of neutral Au6, and supporting the picture of the resonances as weakly bound "surface states." From these studies the 0-0 transition frequency between Au6- and Au6 is measured to be 16 541 +/- 17 cm-1, and the virbational frequencies for the neutral Au6 ground state, the Au6- ground state, and the (Au6-)* anion excited electronic state are 107, 73, and 107 cm-1, respectively. Lastly, we observe evidence for a previously unreported resonance transition to the excited anion which we suggest is the 0-0 transition of Au6- to (Au6-)*.