INHOMOGENEOUS ROTATIONAL-DYNAMICS OF A RODLIKE PROBE IN 1-PROPANOL

The rotational correlation time of the dipolar probe p,p'-cyano thiome thyl diphenylacetylene; varies linearly with the emission Stokes' shif t in l-propanol. This effect is not seen in nonpolar (pentane, hexadec ane) or ''fast'' polar (methanol, acetonitrile) solvents. We ascribe t hese observations to dielectric friction in the different local enviro nments experienced by the probe. These inhomogeneities persist on time scales much longer than the solvation time. (C) 1995 American Institu te of Physics.