The total dipole operator of the molecule is μ = i z i Rik rk , where Ri is the position operator of nucleus i, with charge z i , and rk is the position operator of electron k (with the unit negative charge). Further, ω c is the frequency of the mode in the cavity, â † and â are the photonic creation and annihilation operators, and qc = h/2ω c (â † + â) and pc = i hω c /2(â † -â) are the photonic coordinate and momentum operators, respectively. For a FP cavity, the coupling strength is A 0 = A 0 ê, where ê is the unit vector of the field polarization and A 0 = h/2ω c ε 0 V is the field intensity, V is the quantization volume inside the cavity, ε 0 is the permittivity. Throughout this letter, we treat A 0 (in atomic units) as a parameter. This parameter is related to the commonly used Jaynes-Cummings (JC) Hamiltonian coupling strength g c where g c = ω c A 0 µ 01 for a two-level electronic system transition dipole µ 01 . As a concrete example, if ω c = 5.0 eV, A 0 = 0.01 a.u., and µ 01 = 5.0 a.u. -which will be average parameters in this letter, then g c ≈ 0.01 a.u. with a Rabi frequency of Ω R = 2g c = 0.04 a.u. Although, it should be noted that including a many-level generalization, including DSE and highly oscillatory terms (i.e., not making the rotating wave approximation) as is done in the full PF Hamiltonian causes this direct analogy to be weak as more complex effects arise at large coupling strengths where non-linear effects are ubiquitous.