Dynamics of the H+HCl gas-phase reaction, absolute reactive cross-section for Cl(2P3/2) atom formation

The reaction of atomic hydrogen with HCl was studied in the gas phase using the laser photolysis/vacuum-UV laser-induced fluorescence (LP/VUV-LIF) 'pump-and-probe' technique. Translationally energetic H atoms with an average energy of E-cm = 1.0 eV in the (H-HCl)-center-of-mass system were generated by laser photolysis of H2S at 248 nm. Doppler profiles of nascent Cl(P-2(3/2)) atoms produced in the reactive collision of the H atoms with room temperature HCl molecules were measured under single collision conditions by VUV-LIF. For the H + HCl --> H-2 + Cl(P-2(3/2)) reaction an absolute reaction cross-section sigma(R)(1.0 eV) = (0.34 +/- 0.05) Angstrom(2) was determined by means of a photolytic calibration method using the 248 nm laser photolysis of PCl3 as reference for well-defined concentrations of Cl atoms. Small amounts of Cl in the (P-2(1/2)) excited state were observed in the H + HCl experiments. Bn upper limit of (0.02 +/- 0.01) Angstrom(2) was measured for the Cl*(P-2(1/2)) formation cross-section in the H + HCl reaction at 1.0 eV. (C) 1998 Elsevier Science B.V. All rights reserved.