The unimolecular dissociation of HCO. IV. Variational calculation of Siegert states

We present a new variational method for calculating complex resonance (Sieg ert) states in unimolecular dissociation reactions. The approach is based o n the log-derivative version of the Kohn variational principle. The basic m atrix equations can be formulated in terms of scattering-wave boundary cond itions yielding the resonance states as homogeneous solutions for singular energies. Thus, the resonance positions and widths can be calculated direct ly without employing an artificial absorbing potential. This method is appl ied to the photodissociation of HCO and DCO and the results are compared to the resonance parameters obtained from absorption-type spectra. (C) 1999 A merican Institute of Physics. [S0021-9606(99)00920-4].