ADIABATIC PSEUDOSPECTRAL METHODS FOR MULTIDIMENSIONAL VIBRATIONAL POTENTIALS

We describe a new algorithm for computing eigenvalues, spectral intens ities, and selected eigenvectors of multidimensional vibrational poten tial surfaces. The method involves a synthesis of pseudospectral and s equential adiabatic reduction methods and merges the storage and compu tational advantages of the former with the improved basis set generate d by the latter. The recursive residue generation method, which utiliz es a Lanczos-based diagonalization procedure, is employed to calculate the observables. As a test case, we apply the method to computation o f the infrared and stimulated emission pumping spectra for the HCN mol ecule and demonstrate a very large (one to three orders of magnitude) reduction in computational effort (for comparable accuracy) as compare d to discrete variable representation (DVR)/adiabatic reduction or sta ndard collocation approaches. We expect that this advantage will be in creased considerably for larger (e.g., tetra-atomic) systems and will permit accurate basis set calculations on such systems to be carried o ut in a straightforward fashion.