SOLVATION OF EXCITED MOLECULES OF POLAR C OMPOUNDS BY POLAR-SOLVENT AND KINETICS OF FLUORESCENCE-SPECTRA

We have investigated kinetics of instantaneous fluorescence of phthali mides and 2-acetilanthracene in isobutyl and propyl alcohols at delay times from 2,5 to 70 ns that is 3-4 times the average lifetime in the excited state. It has been found that side by side with usual long-wav e shift of the fluorescence band at a later stage of relaxation a reve rse shift of the band to the opposite region is observed. The shift of the spectrum is accompanied by considerable broadening of the band (p hthalimides) and disturbance of the McCoy and Ross relations for vibra tional bands intensities active in the oscillation spectrum (2-acetyla nthracene). The change of the direction of the band shift indicates th at the Debye model cannot be used for describing the process of excite d molecules solvation by solvent. The reverse shift is accounted for b y different mobility of solvent molecules in coordination layers of th e solvent shell.