Ultrafast refractive index change induced by photoisomerization of an azobenzene derivative: contribution of solvation dynamics of solvent molecules

The refractive index change induced by the photoisomerization of trans-4-am inoazobenzene in alcohol solutions was investigated by using the ultrafast transient lens (UTL) method. We observed a decrease of the refractive index of the solution, which consisted of three decay components with time const ants of 0.3, 0.7 and 2 ps. The amplitude of the 0.3 ps-decay component of t he UTL signal was rather larger in ethanol than in heptanol, while such sol vent-dependence was not detected in the transient absorption measurements. We considered that the difference of the UTL signal in two solutions origin ated from solvation dynamics of solvent molecules. (C) 2001 Published by El sevier Science B.V.