Knowledge Bank

An ab initio method for the study of vibrational resonances in polyatomic molecules is presented. It is based on a variational resolution of the vibrational motion within an electronic potential fitted from a grid of ab initio calculated points. An original multiconfigurational self-consistent filed approach (VMCSCF) has been developed in order to elimate the problem of basis set dependecy occuring with usual methods, like configuration interaction (VSCF-CI), when strong vibrational resonances exist. The method is expected to provide configuration mixing coefficientes directly useful to the interpretation of energy and intensity redistribution in spectra. Preliminary results on $H2O,CH2O$ and $C2H2$ are discussed.