The polaritonic energy eigenfunctions for state I in the NH-CQED-CIS ansatz can be written as a linear combination of the CQED-RHF reference and products of all possible single electron excitations out of the CQED-RHF reference. The CQED-RHF reference involves the product of an electronic Slater determinant with the photon vacuum state |Φ o |0 , so single excitations can occur as electronic excitations from an occupied orbital φ i to a virtual orbital φ a , the raising of the photon number state from |0 → |1 , or both. We therefore write the NH-QED-CIS wavefunction for state I as