VIBRATIONAL-ENERGY LEVELS AND VIBRONIC STRUCTURE OF ELECTRONIC-SPECTRA IN MOLECULES WITH LARGE-AMPLITUDE MOTIONS

This paper presents a software tool for determining the vibrational en ergy levels and the vibronic structure of electronic spectra in molecu les showing one, two or more large amplitude motions. The program, ROV I, uses the potential functions and the kinetic terms for each electro nic state in the construction of the hamiltonian matrix. The hamiltoni an is solved variationally in a free rotor basis to obtain the energy levels and the wavefunctions. In addition, the temperature and the tra nsition dipole moment are used for the calculation of the vibronic str ucture of the electronic spectrum. ROVI simulates the transitions as v ertical lines or by a superposition of lorentzian functions. The progr am is used to illustrate the change in the vibronic structure of the S -0-->T-1 electronic spectrum of acetaldehyde with the temperature.