PRODUCT ENERGY PARTITIONING IN THE UNIMOLECULAR DECOMPOSITION OF VIBRATIONALLY AND ROTATIONALLY STATE-SELECTED HYDROGEN-PEROXIDE

Infrared-optical double resonance prepares HOOH molecules in single ro tational levels of the 6-nu(OH), 5-nu(OH) + nu(OOH), 5-nu(OH) + nu(OO) , and 4-nu(OH) + nu(OH), vibrational states which range from 3 to 2287 cm-1 of excess energy above the unimolecular dissociation threshold. Laser-induced fluorescence probes the nascent OH rotational state dist ributions from the decomposition of rovibrationally selected reactants . The nascent rotational state distributions reveal that both OH spin- orbit states can be populated by the decomposition of a single molecul e and hence that electronic angular momentum is not conserved througho ut the dissociation process. The product state distributions from reac tants excited to the 6-nu(OH) and 4-nu(OH) + nu(OH), vibrational level s are generally in good agreement with the predictions of phase-space theory provided electronic angular momentum is treated statistically. Reactants decomposing from single rotational states in the 5-nu(OH) nu(OOH) combination level (and to a lesser extent the 5-nu(OH) + nu(OO ) level) show product state distributions which are systematically col der than phase-space theory predictions. This observation indicates th at energy redistribution in vibrationally excited HOOH is not complete on the time scale of unimolecular decomposition.