Electronic energy of the 1 L a level of supersonic jet-cooled indole

The dependence of the fluorescence polarization degree on frequency upon excitation into the first and second electronic bands of jet-cooled indole has been studied. A structured band consisting of a number of lines rather than a single line has been recorded in the spectral range of the electronic 1A′-1La-transition. The appearance of the lines is interpreted as the result of nonadiabatic vibronic interaction between the electronic 1La-state and vibronicl states of the indole molecule 1Lb-level. The energy of the unperturbed electronic 1La-level and the orientation of dipole moments near the 1A′-1La-transition have been found.