Zero electron kinetic energy spectroscopy of Au−6

Zero electron kinetic energy (ZEKE) spectroscopy and photodetachment cross section measurements have been carried out on Au−6. 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 Au−6 and Au6 is measured to be 16 541±17 cm−1, and the vibrational frequencies for the neutral Au6 ground state, the Au−6 ground state, and the (Au−6)* 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 Au−6 to (Au−6)*.