Time-resolved study of the photodissociation of Au2O−

Photodissociation of the Au2O− anion is studied using TR-PES. A new spectral feature appearing with a delay of 1 ps indicates the existence of a long-lived excited state with a geometry different from the ground state. With increasing delay the pump-probe feature shifts to higher binding energy. At 7 ± 2 ps after excitation no further shift is observed, but now fragmentation into AuO− + Au and Au− + AuO starts with a time constant of 110 ± 3 ps, accompanied by a decrease of the excited state feature. The spectra indicate that the delayed onset of fragmentation is caused by the time the system needs to reach a new minimum on the excited state potential surface. Hence, the time-resolved photoelectron spectra mirror part of the motion of the anion on the excited state potential surface.