Polarization response of an ensemble of polyatomic molecules after photoisomerization

Polarization response of photoisomerizing molecules under collisionless conditions is studied. General expressions are obtained for the fluorescence anisotropy in case of asymmetric top initial and isomer molecules, and for an arbitrary time between absorption of light and transition to an isomer state. The explicit calculations are performed for the steady-state anisotropy in several extreme cases. We show that detection of the polarized fluorescence offers one to estimate characteristic times of the reaction and to determine molecular orientation of absorption and emission dipole moments.