Photodissociation dynamics of phenol

The photodissociation of phenol at 193 and 248 nm was studied using multimass ion-imaging techniques and step-scan time-resolved Fourier-transform spectroscopy. The major dissociation channels at 193 nm include cleavage of the OH bond, elimination of CO, and elimination of H ₂O. Only the former two channels are observed at 248 nm. The translational energy distribution shows that H-atom elimination occurs in both the electronically excited and ground states, but elimination of CO or H ₂O occurs in the electronic ground state. Rotationally resolved emission spectra of CO (1 < v < 4) in the spectral region of 1860-2330 cm ^-1 were detected upon photolysis at 193 nm. After a correction for rotational quenching, CO (v < 4) shows a nascent rotational temperature of ∼4600 K. The observed vibrational distribution of (v = 1)/(v = 2)/(v = 3)/(v = 4) = 64.3/22.2/9.1/4.4 corresponds to a vibrational temperature of 3350 ±20 K. An average rotational energy of 6.9±0.7 kcal mol-1 and vibrational energy of 3.8 ±0.7 kcal mol"1 are observed for the CO product. The dissociation channels, translational energy distributions of the photofragment, and vibrational and rotational energies of product CO are consistent with potential energy surfaces from quantum chemical calculations and the branching ratios from an RRKM calculation.