WAVELENGTH DEPENDENCE OF EXTERNAL-FIELD EFFECTS ON PERSISTENT HOLE-BURNING SPECTRA - ANALYTICAL APPROXIMATION

External perturbations such as, for instance, hydrostatic pressure in general give rise to a shift and a concomitant broadening of persistent hole-burning spectra. The magnitude of both effects usually varies with the optical frequency in the inhomogeneous absorption band. Within the framework of a stochastic theory of dye-matrix interaction, an extended Gaussian approximation is used to derive general analytical expressions for the variation of both the shift and the broadening parameter. The results are compared with numerical calculations. Furthermore, the obtained expressions are generalized to take correlations between the matrix molecules into account.