Using this methodology, a number of considerations need to be highlighted. Firstly, while in non-cavity internal conversion there are no photonic degrees of freedom (the zero-photon state), this is not the case here. The photonic degrees of freedom are important here and cannot be neglected; in this formalism it is the vacuum fluctuation of photons rather than the promoting modes themselves that participate in the transition . Via this process, the energy which would otherwise be lost is instead partially converted into photonic energy, yielding a final electronic-photonic state.