ω chosen to be at resonance with an electronic transition is scattered inelastically, yielding a Stokes and an anti-Stokes signal E S that changes the molecular vibrational state. In contrast to non-resonance Raman where selection rules restrict the transitions to vibrational modes that change the molecular polarizability, in RR all vibrational modes that are coupled to the electronic transition yield a signal. The theory of RR cross sections (see Supplementary Information and Refs. ) is based on a two-surface molecular model, with Hamiltonian H M = H g |g⟩ ⟨g| + H e |e⟩ ⟨e|.