OH produced from o-nitrophenol photolysis: A combined experimental and theoretical investigation.

Photodissociation dynamics of o-nitrophenol in the gas phase at different photolysis wavelengths (361–390 nm) is investigated, and the nascent OH radical is observed by the single-photon laser-induced fluorescence technique. At all the photolysis wavelengths, the OH radicals are formed in vibrationally cold state (υ^″=0) and have similar rotational state distributions. The average rotational temperature for all the photolysis wavelengths is approximately 970±120 K, corresponding to a rotational energy of 1.9±0.2 kcal mol^-1. The spin orbit and Λ-doublet states of the OH fragments formed in the dissociation are measured to have nonstatistical distributions. To get an insight into the dissociative mechanism leading to OH formation in the photolysis of o-nitrophenol, the potential energy surfaces of the OH-forming channels are mapped by ab initio theoretical calculations. According to both experimental and theoretical results, a possible mechanism for OH formation is proposed. [ABSTRACT FROM AUTHOR]