Spectroscopy and Photodissociation Dynamics of Highly Vibrationally Excited Molecules

Vibrationally mediated photodissociation is a technique for studying the spectroscopy and photodissociation dynamics of highly vibrationally excited molecules. One photon prepares a highly vibrationally excited molecule by excitation of a vibrational overtone transition, and a second photon of the same or different wavelength fragments the molecule by excitation to a dissociative electronic state. A third photon from a probe laser interrogates individual quantum states of the fragment by laser induced fluorescence. Applying this technique to hydrogen peroxide and nitric acid provides vibrational overtone excitation spectra in the regions of the 4υOH and 5υOH transitions in HOOH and in the region of the 4υOH transition in HONO2. The photodissociation dynamics arc modified by the participation of the highly vibrationally excited intermediate state. In both HOOH and HONO2, the OH fragment is created with more vibrational energy than in the one‐photon ultraviolet photolysis. In the dissociation of HONO2, a large fraction of the available energy appears in internal excitation of the NO2 fragment, possibly including electronic excitation.