Influence of initial parent vibrational excitation in promoting two-photon absorption in HOOH and CH3OOH

Two-photon dissociation of vibrationally excited HOOH and CH3OOH is demonstrated from their 2νOH stretching overtone state using ∼205 nm light. Initial vibrational excitation appears to be a prerequisite for accessing the two-photon excited dissociative electronic state in these hydroperoxides, most likely due to the ability of vibrational excitation to improve the Franck–Condon factor. The hydroperoxide excited state accessed through the vibrationally mediated photodissociation process generates OH fragments in their A2Σ+ electronic excited state. Detection of the OH(A2Σ+) fluorescence as a function of the vibrational excitation laser allows recording of the 2νCH overtone action spectra for CH3OOH with high sensitivity.