VIBRONIC STRUCTURES OF THE GROUND AND EXCITED SINGLET ELECTRONIC STATES OF DIMETHYLNAPHTHALENES COOLED IN A SUPERSONIC JET

Fluorescence excitation and dispersed fluorescence spectra of jet-cool ed naphthalene and 2,6-, 2,7-dimethylnaphthalenes have been measured. The frequencies of optical active vibrations in the ground and first e xcited singlet states have been determined. The new technique for calc ulation of planar vibration frequencies of polycyclic benzenoid hydroc arbons in the excited electronic states has been developed. The vibrat ion frequencies in the ground and first excited singlet states of thes e molecules were calculated using the developed technique and the Ohno 's model. The interpretation of vibronic spectral lines based on the c omparison of the calculated and experimental data was made. The calcul ation rms errors for the vibration frequencies in the ground electroni c states of the investigated molecules do not exceed 20 cm(-1) and are approximately 1.5 times higher for excited states without additional adjustment of parameters for individual molecules.