Vs. Pavlovich et Sv. Zablotskii, DESTRUCTION OF THE VIBRATIONAL STRUCTURE OF THE BAND OF INSTANTANEOUSFLUORESCENCE-SPECTRA OF POLAR SOLUTIONS WITH INCREASING DELAY-TIME, JETP letters, 58(11), 1993, pp. 815-818
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.