ELECTRONIC SPECTROSCOPY AND QUENCHING DYNAMICS OF OH-H-2 D-2 PRE-REACTIVE COMPLEXES/

Binary complexes of OH X (II)-I-2 and H-2/D-2 have been stabilized in the entrance valley to the hydrogen abstraction reaction and identifie d in the OH A (22)Sigma(+)-X (II)-I-2 0-0 spectra region. Nearly all o f the intermolecular vibrational levels supported by the OH A (2) Sigm a(+) (v'=0)+H-2/D-2 potential. energy surface have been observed in fl uorescence depletion experiments. Rapid electronic quenching precludes the observation of OH-H-2/D-2, prepared in these levels by laser-indu ced fluorescence. A sharp onset of laser-induced fluorescence occurs a t the OH A (2) Sigma(+) (v'=0)+H-2/D-2 dissociation limit. The binding energies for OH-H-2/D-2 in the ground state correlating with OH X (II )-I-2 (v''=0)+H-2/D-2 have been determined to be 54 cm(-1) and more th an 66 cm(-1), respectively. The OH A (2) Sigma(+) (v'=0)+H-2/D-2 excit ed state is found to be at least 577 cm(-1) (H-2) and 639 cm(-1) (D-2) mom strongly bound than the ground state. The positions of observed f eatures are compared with the corresponding intermolecular levels obse rved by laser-induced fluorescence in the OH A-X 1-0 region as well as theoretical predictions of the transition energies based on ab initio potentials for the ground and excited electronic states. The OH-H-2/D -2 intermolecular levels correlating with OH A (2) Sigma(+) (v'=0)+H-2 /D-2 have lifetimes of 3.2-4.5 ps, deduced from homogeneous linewidths , due to quenching and/or chemical reaction. (C) 1996 American Institu te of Physics.