Time-resolved study of the photodissociation of Au2O−

Photodissociation of the Au2O− anion following absorption of a 3.1 eV photon is studied using time-resolved photoelectron spectroscopy. A new spectral feature appearing after 1 ps indicates the existence of a long-lived excited state with a geometry different from that of the ground state. With further 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. The dissociation process is 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.