Renner-Teller induced photodissociation of HCO in the first absorption band: Determination of linewidths for the (A)over-tilde(2)A '' K=0,1 states byfilter-diagonalization

We present new calculations on the Renner-Teller induced decay of the vibra tional states of HCO((A) over tilde(2)A") using accurate ab initio potentia l energy surfaces. The dynamics calculations are performed by employing fil ter 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 abo ve the H+CO(r(e)) dissociation threshold-and the determination of the width s 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 indicatin g 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 accou nted 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].