Photodissociation Dynamics of o-Nitrobenzoic Acid

Photodissociation dynamics of o-nitrobenzoic acid at 295 and 355 nm was studied by probing the nascent OH photoproduct employing the single-photon laser induced fluorescence technique. At both the photolysis wavelengths, the OH fragments are found to be vibrationally cold but have different rotational state distributions. Upon photolysis at 295 nm, the relative population of OH in different rotational states does not follow Boltzmann equilibrium distribution, whereas upon photolysis at 355 nm, a perfect Boltzmann distribution is observed with a rotational temperature of 1010 ± 100 K. Between the two spin-orbit states, 2Π3/2 and 2Π1/2, the former is found to be preferentially populated and the distribution of the Π(A′) state for the Λ-doublet is dominant at both the wavelengths studied. Several possible dissociation pathways of o-nitrobenzoic acid leading to formation of the OH fragment were investigated computationally. Based on the theoretical and experimental studies, a possible mechanism of OH formation from the photodissociation of o-nitrobenzoic acid at 295 and 355 nm is proposed.