Laser-induced fluorescence study of the hydrogen atom formation dynamics in the 248 nm gas-phase photodissociation of vibrational state selected water (H₂O (|04^->))

Abstract

The vibrationally-mediated H₂O gas-phase photodissociation was studied at a photolysis wavelength of 248 nm. Single rotational states of the |03^->|2> and |04.> H₂O overtone vibrations were prepared by laser photoexcitation around 720 nm. H atoms formed in the photodissociation of the H₂O (|04^->J'_KaKc = 313) were detected by Lyman-α laser-induced fluorescence spectroscopy with sub-Doppler resolution to determine their translational energy. The present result confirms that in the dissociation process the major part (ca. 93%) of the available energy is released as relative translational energy of the nascent H + OH photofragments, in agreement with earlier complementary measurements (R. L. Vander Wal, J. L. Scott and F. F. Crim, J. Chem. Phys. 94, 1859 (1991)), where the internal excitation of the OH product radical was investigated at different photolysis wavelengths.