title: Response theory for vibrational wave functions.
abstract: A formalism for deriving and implementing response functions for vibrational wave functions is described. The formalism utilizes a recently developed second-quantization formulation of many-mode dynamics to define nonredundant parameterizations for different types of approximate vibrational wave functions. The derived response functions cover the cases of an exact state, a vibrational self-consistent field state, and a vibrational configuration interaction state. Sample calculations are presented for the linear-response function and response excitation energies for a two-mode model system and for formaldehyde employing a quartic force field. The advantages and disadvantages of the response theoretical approach for describing excitation energies using different parameterizations are discussed.
authors.affiliation: Department of Chemistry, University of Arhus, DK-8000 Arhus C, Denmark. ove@chem.au.dk
authors.forename: Ove
authors.initials: O
authors.lastname: Christiansen