K. Chandrasekhar et al., ORIENTATIONAL RELAXATION OF AMINOCOUMARINS BY TIME-RESOLVED DICHROISMWITH PICOSECOND PULSES, Spectroscopy letters, 28(2), 1995, pp. 153-165
The orientational relaxation times (tau(r)) of coumarin 102 and coumar
in 138 molecules were measured in ethanol and ethylene glycol solution
s at room temperature by transient dichroism technique on picosecond t
ime scales. The experimental data were compared with the calculated va
lues based on Stokes-Einstein-Debye (SED) hydrodynamic model. The resu
lts show that the measured values of tau(r) of both the dyes in ethano
l reasonally agree with the theoretical ones; but for ethylene glycol
solutions, relaxation times are shortened indicating the inadequacy of
the SED model for the description of the rotational motions. The resu
lts are discussed on the basis of molecular structures of the dyes and
intermolecular interactions.