Renner-Teller induced photodissociation of HCO in the first absorption band:: Determination of linewidths for the (A)over-tilde2A K=0,1 states by filter-diagonalization

We present new calculations on the Renner-Teller induced decay of the vibrational states of HCO((A) over tilde(2)A) using accurate ab initio potential energy surfaces. The dynamics calculations are performed by employing filter diagonalization and an absorbing optical potential in the exit channel. The objective of this investigation is twofold: the completion of earlier time-dependent wave packet calculations by determining resonance widths for all vibrational states for projection quantum number K=1-up to 2.75 eV above the H+CO(r(e)) dissociation threshold-and the determination of the widths for the long-lived K=0 states. In the latter case, a clear-cut J(2)(J+1)(2) dependence, where J is the total angular momentum, is observed indicating that the rate determining step is K-resonance interaction between K=0 and 2 states. The experimentally observed J-independent contribution (0.22-0.5 cm(-1)), which dominates the linewidth for small values of J, is not accounted for by our calculations. Arguments are put forward, that it is caused by spin-orbit interaction, which is not included in our treatment. (C) 2000 American Institute of Physics. [S0021-9606(00)00335-4].