Spectral kinetics of stimulated emission from solutions and relaxation processes in dye molecules

A quantitative investigation was made of the relaxational shift of the spectra during the evolution of a stimulated emission pulse in a solution of rhodamine 6G in ethanol excited by a frequency-tunable Q switched laser. A linear relationship was established between the relaxational shift and the power of the stimulated radiation field in the resonator. The rate of shift was found to depend on the pump va and stimulated emission ν_γ frequencies. The probabilities of the vibrational (transverse) relaxation were found to be within the range W^ν ≈ 10¹⁰–10¹¹ sec^–1, depending on the values of ν_α and ν_γ. The relaxation processes under discussion were found to be controlled by the properties of the vibrational states of the molecules and the dominant effect was the relaxation of the totally symmetric high-frequency vibrations. An analysis was made of the possible influence of the solvent on the intramolecular relaxation processes.