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Abstract

The photoluminescence from isotropic solutions and the light absorption by photogenerated species in isotropic solutions are in general partially polarized. In the case of electric-dipole transitions, the polarization bias can be represented as the product of a sample-dependent factor and a geometrical factor G for arbitrary experimental arrangements; G depends only on the orientation of the polarizers in the excitation beam and in the luminescence beam. G = 0 is a sufficient condition for the elimination of the polarization bias. The formalism is extended to unpolarized excitation and/or detection. The condition G = 0 is independent of ground-state depletion due to polarized or unpolarized excitation. The rotation of monochromators is introduced as a new experimental parameter. All known experimental configurations are treated in a systematic way. New configurations are proposed for surface excitation and for a quantum counter. The main results apply also to transient-absorption spectroscopy.