The above equation is identical to the derivative couplings derived by Kowalewski and Mukamel 23 for a JC light-matter interaction model (Eq. 9), subject to a difference in terms of the DSE term in ∆V . This is not surprising, because within the {|e0 , |g1 } subspace, the light-matter interaction Hamiltonian reduces to a JC type Hamiltonian (see Eq. 34).