Abstract

The formation of a hot photoproduct of nickel octaethylporphyrin (NiOEP) upon ππ* excitation and its subsequent vibrational energy relaxation were monitored by picosecond time-resolved resonance Raman spectroscopy. Resonance Raman bands due to the photoproduct instantaneously appeared upon the photoexcitation. Their intensities decayed with a time constant of 330±20ps, which indicates electronic relaxation form the (d, d) excited state (B1g) to the ground state (B1g). Anti-Stokes ν4 band of the hot (d, d) excited state of NiOEP appeared immediately after the excitation and decayed with time constants of 11±2 and 330±40 ps. In contrast, the rise of anti- Stokes ν7 intensity was not instantaneous but delayed by 2.6±0.5 ps, which suggests that IVR has not been completed in a subpicosecond time regime.