A simple analytical model is presented describing the shape of a persistent spectral hole in a homogeneous electric field for random orientation of the dye molecules in the host matrix. We consider the two cases that the absorbers have either one fixed value or a distribution of values of the electric dipole moment difference Dgr;mgr; between the ground and excited electronic states. Comparison with experiment yields the Dgr;mgr; values for chlorin (Dgr;mgr;=0.214 D) and a substituted Znhyphen;tetrabenzoporphin (sim;(Dgr;mgr;) =0.174 D) in poly(vinylbutyral). In the latter case the isolated dye molecule has inversion symmetry, yet there is nevertheless a dipole moment through the interaction with the polar matrix of low local symmetry.
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