Quantum-classical mechanics: On the problem of a two-photon resonance band shape in polymethine dyes

Transformation of the theoretical spectra of a model polymethine dye with different deviations from the Egorov resonance condition θ = 1/2 . The black curve describes an optical band corresponding to θ = 0.44, that is near the resonance band corresponding to θ = 1/2, the red curve describes an optical band corresponding to θ = 0.88, that is far beyond the resonance band (shown on different scales).