Efficiently computing bound-state spectra: A hybrid approach of the multi-configuration time-dependent Hartree and filter-diagonalization methods

We present a new approach for determining bound-state spectra of molecules or clusters. In our approach a wave packet propagation is performed, which exploits the efficiency of the multi-configuration time-dependent Hartree scheme, to produce an autocorrelation function. From this, an accurate spectrum is extracted employing the filter-diagonalization procedure. The accuracy of this hybrid method is demonstrated by applying it to the spectrum of carbon dioxide. Compared with the filter-diagonalization scheme based on a numerically exact wave packet propagation and with a matrix diagonalization using the Lanczos algorithm, our approach turns out to be more efficient. The method can easily be generalized to the treatment of resonant states. (C) 2001 American Institute of Physics.