Picosecond polarized fluorescence experiments on DMABN (4-(dimethyl am
ino)benzonitrile) in polar solvents and toluene are reported. From the
detected polarized fluorescence components emission anisotropy histog
rams are constructed and compared with the synthetic data simulated fo
r the energy levels scheme in DMABN. For the short-wavelength emission
of DMABN vibronic coupling between the close-lying S-1 and S-2 energy
levels occurs and leads to a vibronically mixed polarization of the S
-1 (F-B) fluorescence. Low initial values of the emission anisotropy d
ecays for the long-wavelength (F-A) emission are observed. This observ
ation can be explained by an assumption that the internal twisting of
the amino group in DMABN changes the angular orientation of DMABN and
by an assumption that the emission dipole moment in the F-A emission b
and is not parallel to the absorption dipole moment in the S-2 (L-1(a)
) absorption band. (C) 1997 Elsevier Science B.V.