CALCULATION OF QUANTUM RESONANCE ENERGIES AND LIFETIMES VIA QUASI-MINIMUM RESIDUAL FILTER DIAGONALIZATION

The quasi-minimum residual (QMR) method of Freund [SIAM J. Sci. Stat, Comput. 13 (1992) 425] is applied to the problem of calculating quantu m resonance energies and lifetimes via a filter diagonalization (FD) s cheme. Using the HO2 molecule as a test case, the resulting quasi-mini mum residual filter diagonalization (QMRFD) algorithm is shown to be c apable of accurately computing complex eigenvalues throughout the spec trum from a single Lanczos subspace. The algorithm is efficient, and r equires the storage of only two complex vectors in the primary DVR rep resentation. The quality of the FD results is verified by a comparison with resonance energies and linewidths obtained by fitting the spectr al density profile. (C) 1998 Elsevier Science B.V.