Vibrational Energy Relaxation in the (d, d) Excited State Of Nickel Octaethylporphyrin

The formation of a hot photoproduct of nickel octaethylporphyrin (NiOEP) upon ππ * excitation and its subsequent vibrational energy relaxation were monitored bypicosecond time-resolved resonance Raman spectroscopy. Resonance Raman bandsdue to the photoproduct instantaneously appeared upon the photoexcitation. Theirintensities decayed with a time constant of 330±20ps, which indicates electronicrelaxation form the (d, d) excited state ( B 1 g) to the ground state ( B 1 g). Anti-Stokes ν 4 band of the hot (d, d) excited state of NiOEP appeared immediately after the excitationand decayed with time constants of 11±2 and 330±40 ps. In contrast, the rise of anti-Stokes ν 7 intensity was not instantaneous but delayed by 2.6±0.5 ps, which suggests thatIVR has not been completed in a subpicosecond time regime.