The electronic dipole matrix at each R is diagonal in this diabatic representation. This is because the diabatic states |I⟩ and |C⟩, also referred to as the Mulliken-Hush diabatic states, are by definition the eigenstates of the electronic transition dipole operator (see discussion around Eq.10). Fig. presents the matrix elements of μ in both the diabatic (solid lines) and the adiabatic (dashed lines) representations. As expected, the permanent dipole for the ionic state |I⟩ (corresponding to Li + F -) µ I (R ) linearly increases, while the permanent dipole for the |C⟩ state (corresponding to covalently bonded Li-F ) µ C (R ) remains nearly zero with increasing interatomic separation R . The adiabatic states switch their characters around R ≈ 13.5 a.u., as a result, the adiabatic permanent dipole switches in that region, and µ eg (R ) peaks at R ≈ 13.5 a.u. Fig. shows the polaritonic potential energy surfaces for a cavity frequency ω c = 1.5 eV and light-matter coupling strength A 0 = 0.127 a.u. The coloring indicates the average photon number of the polaritonic state. Given an initial excitation from |G(R ), 0⟩ → |E(R ), 0⟩ (vertical black arrow) at the ground state minimum (outside the cavity's influence), the time-dependent average photon number was calculated (see Ref. for more details) and shown in Fig. . Thus, through nuclear motion and light-matter coupling, excited photons can be generated.