DESTRUCTION OF THE VIBRATIONAL STRUCTURE OF THE BAND OF INSTANTANEOUSFLUORESCENCE-SPECTRA OF POLAR SOLUTIONS WITH INCREASING DELAY-TIME

The evolution of the instantaneous flurorescence spectra of polar comp ounds in alcohols has been studied at delay times t greater than the a verage lifetime in the excited state by a factor of 5, 6, or more. As t is increased, one observes a destruction of the vibrational structur e, a coalescence of the less intense vibrational bands, and a compress ion of the spectrum. This compression then gives way to an expansion, and the structure is partially restored. It is suggested that the effe cts observed stem from nonadiabatic random perturbations of an excited molecule which result from an abrupt reorientation of the molecules o f the medium and their polar fragments (OH groups) and from a reorient ation of the fragments of the compounds themselves. Such perturbations modulate the phase and amplitude of the radiation and also alter the frequency, leading to a spectral ''borrowing'' and a redistribution of intensity in the electronic-vibrational emission spectrum.