Vibrational characteristics and vibrational contributions to the nonlinear optical properties of a push-pull polyene in solution

The frequency shift and IR and Raman intensity changes of the characteristic vibrational mode of a pushpull polyene in polar solvent are described theoretically by using a simple two-state model. Depending on the electronic structure of the ground state in solution, the characteristic vibrational frequency can be either red-shifted or blue-shifted as the solvent polarity increases. The IR and Raman intensities are also found to be greatly influenced by the solvation. Finally, the solvation effects on the vibrational contributions to the molecular hyperpolarizabilities are briefly discussed.