Correlation between redshifts and widths of the 0–0 band in the absorption spectra (1 1Bu←1 1Ag) of all-trans-β-carotene in solution

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Abstract
The wave numbers and widths of the 0–0 band in the electronic absorption spectra (1 1Bu←1 1Ag) of all‐trans‐β‐carotene in various solvents at room temperature are analyzed. These quantities are obtained with sufficient precision from the broad absorption spectra by performing simulations with the parameters obtained in our previous work. The excess redshifts for various solvents (deviations from the linear relationship between the 0–0 wave number and the Bayliss parameter obtained for alkane solvents) are found to be correlated with the 0–0 band widths. To explain this correlation quantitatively, a theoretical model is developed by introducing a low‐frequency collective solvent mode, which changes significantly the microscopic polarizability of solvent. This model is consistent with the experimental result that excess redshifts can be observed in nonpolar as well as polar solvents. It is pointed out that the small Stokes shifts observed for β‐carotene in nonpolar solvents can also be explained by this model.