VARIATIONAL METHOD FOR THE CALCULATION OF THE VIBRATIONAL STRUCTURE OF THE ELECTRONIC-SPECTRA OF POLYATOMIC-MOLECULES .1.

A method is proposed to calculate the vibrational structures of the el ectronic spectra of polyatomic molecules based on the variational solu tion of the vibrational problem in the excited state with the vibratio nal wave functions of the ground state as basis set. The electrono-vib rational problem leads to an evaluated and diagonalized variational ma trix. The elements of the variational matrix have a simple form which is easily evaluated, has a clear physical meaning and is directly inte rconnected with observed spectral effects. This allows preliminary est imation of spectral phenomena and correction of the molecular model to take account of experimental results. The use of contemporary methods of diagonalization of the variational matrix, which possesses a chara cteristic structure, facilitates a tenfold increase in the speed of th e method in comparison with traditional methods.