where the subscripts indicate the number of molecules that participate in VSC (from Eq. ( ), it can be seen that UP 0 corresponds to the uncoupled photon mode, and LP 0 and D ðkÞ 0 are non-existent). This reaction implies that each time a molecule transforms into the product, it becomes part of the ensemble that couples to light (see Supplementary Note 2 for additional insight). Electron transfer occurs as a result of a vibronic transition between diabatic states; this feature makes it similar to Raman scattering. A study of the latter under VSC took advantage of the massive degeneracy of the dark modes to introduce a judicious basis ,