Laser studies on the dynamics of elementary steps with translationally and vibrationally excited reactants

Abstract

The reactions D + H₂(v= 0, 1)→ HD (v= 0, 1)+ H have been studied by CARS spectroscopy in a fast-discharge flow system. In contrast to previous experiments good agreement has been obtained between experimental values and results of quasi-classical trajectory calculations using the most recent potential-energy surface of the H₃ system. Vibrational and rotational energy transfer between H₂ and HD has been studied directly using Raman excitation combinated with time-resolved CARS spectroscopy.

The reaction H + O₂→ OH + O has been studied using translationally hot H atoms at various energies. Absolute total reactive cross-sections, nascent rotational state distributions and information on the distribution of orientations of the OH angular momentum vector using polarized dissociation and analysis laser sources have been obtained.

The reaction OH + CO → CO₂+ H was studied for translationally hot reactants in both directions. Hydroxyl radicals were produced by laser photolysis of H₂O₂ at 193 nm. The initial rotational distribution of the OH radical shows a Gaussian-like distribution with a maximum at K″= 12 and with 16% of the total available energy appearing in rotation and <1% in vibration. A total reaction cross-section of 19 ± 10 Ų at E_cm= 1.32 eV of the OH radicals was measured from the absolute number of H atoms formed.