Influence of transitions between excited singlet and triplet states on the phase response of dye solutions

An investigation is made of the transitions between excited singlet and triplet states, and of the effects of stereoisomerism molecules on the light-induced change in the refractive index of a dye solution. It is shown that the contribution of the ground and excited channels to the total phase response varies within a wide range depending on the spectroscopic characteristics of the medium and the parameters of the exciting radiation. An estimate is obtained of the ratio of the contributions of the resonant and thermal nonlinearities to the total change in the refractive index.