Stark effect of polar and unpolar dye molecules in amorphous hosts, studied via persistent spectral hole burning

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 Δμ between the ground and excited electronic states. Comparison with experiment yields the Δμ values for chlorin (Δμ=0.214 D) and a substituted Zn-tetrabenzoporphin (∼(Δμ) =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.