Polarized photochromism in solid solutions

Reversible photochromic transitions are in principle analogous to fluorescence. By this analogy reversible photochromic processes in a rigid transparent medium should display a characteristic anisotropy spectrum with respect to the polarization of the excitation and the monitoring lights. The polarized photochromism spectrum can help to elucidate the chemical structure of the phototransient and to assign the orientation of its transition dipoles. The following report presents and discusses polarization spectra of physical and chemical photochromic processes, measured by a novel steady-state method.