UNIMOLECULAR DISSOCIATION OF HCO .2. COMPARISON OF CALCULATED RESONANCE ENERGIES AND WIDTHS WITH HIGH-RESOLUTION SPECTROSCOPIC DATA

We present a theoretical study of the unimolecular dissociation resona nces of HCO in the electronic ground state, (X) over tilde(1)A', using a new ab initio potential energy surface and a modification of the lo g-derivative version of the Kohn variational principle for the dynamic s calculations. Altogether we have analyzed about 120 resonances up to an energy of approximate to 2 eV above the H+CO threshold, correspond ing to the eleventh overtone in the CO stretching mode (v(2)=11). The agreement of the resonance energies and widths with recent stimulated emission pumping measurements of Tobiason et al. [J. Chem. Phys. 103, 1448 (1995)] is pleasing. The root-mean-square deviation from the expe rimental energies is only 17 cm(-1) over a range of about 20 000 cm(-1 ) and all trends of the resonance widths observed in the experiment ar e satisfactorily reproduced by the calculations. The assignment of the states is discussed in terms of the resonance wave functions. In addi tion, we compare the quantum mechanical state-resolved dissociation ra tes with the results of classical trajectory calculations and with the predictions of the statistical model. (C) 1996 American Institute of Physics.