Beyond electrostatic and polarization interactions between the chromophore and solvent molecules, charge transfer can also occur upon the chromophore excitation/de-excitation. One can imagine two mechanisms for such a charge transfer to occur: (a) The frontier orbitals of the chromophore can entangle with solvent orbitals, causing them to spread over to the solvent (similar to the spillover of chromophore orbitals to substituent groups ) and introducing partial charge transfer if the solvent involvement differs between the initial and final electronic states; and (b) An electronic transition within the chromophore (i.e. local excitation/deexcitation) gets superimposed with a chromophore→solvent or solvent→chromophore electronic transition. Clearly, these mechanisms, with one based on the mixing of one-electron fragment orbitals while the other on the superposition of many-electron electronic configurations, are not mutually exclusive. Neither mechanism, however, has been accounted for in existing continuum solvent or QM/MM models, because no orbitals are placed on the solvent molecules within these models.