Resonances in the photodetachment cross section of Au−2

This paper reports the observation of autodetaching resonances in photoelectron spectroscopy of Au−2 according to the process Au−2 +hν■(Au−2)*■Au2 +e−. They appear as sharp features superimposed upon a nearly constant signal associated with direct photodetachment process from Au−2 :Au−2 +hν■Au2+e−. By altering the cluster expansion conditions, the dimer anion temperature can be varied. This leads to changes in the linewidth and relative intensities of the resonances and allows ground state and hot band transitions to be identified. The resonances correspond to electronic transitions to a long‐lived excited state of Au−2 with a significantly lower vibrational frequency (128±2 cm−1) than that of the neutral ground state (190.9 cm−1), or even the anion ground state (149 cm−1). It decays via electronic autodetachment in a two‐electron process similar to autoionization of neutral atoms.