Excited State Dynamics of o-Nitrophenol Studied with UV-Pump, VUV-Probe Time Resolved Photoelectron and Photoion Spectroscopy

Time resolved photoionization measurements were performed on o-nitrophenol pumped with UV laser pulses at a central wavelength of 255 nm (4.9 eV) and probed with VUV pulses at 153 nm (8.1 eV). The photoelectron spectrum and time of flight mass spectrum for ions were recorded at each pump-probe delay. The measurements are interpreted with the aid of electronic structure calculations for both the neutral and ionic states. Evidence is found for the formation of a bicyclic intermediate followed by NO dissociation, through a process of internal conversion and intersystem crossing.