SPECTATOR MODES IN RESONANCE-DRIVEN REACTIONS - 3-DIMENSIONAL QUANTUMCALCULATIONS OF HOCO RESONANCES

We have performed three-degree-of-freedom quantum calculations of HOCO resonances by using a complex potential method. The coordinates we co nsider are the OH internuclear distance, the CO internuclear distance, and the distance between the centers of mass of the OH and CO fragmen ts. The reduced dimensionality potential has been constructed by addin g the nonreactive ''spectator'' CO coordinate to the previous two-degr ee-of-freedom potential of Schatz and Dyck [G. C. Schatz and J. Dyck, Chem. Phys. Lett. 188, 11 (1992)] using a Shepard-type interpolation p rocedure. The positions and lifetimes of more than two hundred resonan ces are calculated and approximate quantum numbers are assigned. The r esults are compared with previous two-degree-of-freedom calculations w here the GO-stretch mode has not been considered. The appearance of a new group of narrow resonances with a significant CO stretch contribut ion is reported. The results are tested against the vibrational shifti ng approximation in which the spectator CO mode is treated adiabatical ly. The latter is shown to be insufficient for quantitative prediction s of resonance positions and widths, however averaged positions and wi dths are reasonably well described. The rotational shifting approximat ion is tested by performing the adiabatic rotation calculations of res onances for J=1, K=0 and J=1, K=1 cases, where J is the total angular momentum and K is the body-fixed projection quantum number of a symmet ric top. Rotational shifting is shown to work better for K=0 case than for K=1 case. (C) 1998 American Institute of Physics.