Abstract

A molecular absorption of linearly polarized light gives origin to an ensemble of anisotropically excited molecules. As a result of reorientation (rotation) of molecules the anisotropy (absorption or luminescence) changes with time. The calculations performed classically by Blokhin et al. [1,2] and later quantum mechanically by Myers and Hochstrasser [3] and Felker and Zewail [4] showed that the relaxation of optically induced orientational anisotropy of the ensemble of free molecules in gas phase has a complex time dependence, and differs significantly from the relaxation in condensed media. An experiment with stilbene was taken by Scherer et al. [5] at temperature 2K in a molecular beam. The anisotropy decay time was about 50 ps. But the application of a picosecond technique did not make it possible to measure in detail the kinetics of decay of luminescence anisotropy in the experiment with the stilbene vapour at 463 K (Myers et al.[6]).

© 1990 Optical Society of America