Absorption Spectra of Dyes in Solution

A theory of absorption spectra of dyes in solution is presented. The wave-number shift of the absorption maximum is calculated by using the perturbation theory, where the distribution of solvent molecules is assumed to be uniform, and the shift is represented by experimentally convenient quantities, such as the dielectric constant, the refractive index, and the absorption wave-length of the solvent. The solvent effects are, classified into several groups, and the theory can explain the various experimental facts successfully. Previous theories are criticized.