VARIATIONAL METHOD FOR THE CALCULATION OF THE VIBRATIONAL STRUCTURE OF THE ELECTRONIC-SPECTRA OF POLYATOMIC-MOLECULES .2.

A variational method has been developed to solve the vibrational probl em in the excited electronic state and to calculate the vibrational st ructure of the electronic spectrum of polyatomic molecules. The proper ties and structural characteristics of the variational matrix have bee n analyzed and an effective algorithm has been proposed for its approx imate diagonalization. The effectiveness of the method and the corresp onding suite of programs for the personal computer have been analyzed via the results of model calculations for a number of molecular struct ures. The method has high precision (errors of about 5% for frequencie s and 15% for relative intensities), is an order of magnitude faster t han previously used methods, and provides the possibility for the effe ctive solution of the electrono-vibrational problem for polyatomic mol ecules, including the reverse problem.