Note that the delta-function is usually broadened with a normalized, finite-width Gaussian or Lorentzian function to account for excitonic, photonic, and/or environmental relaxation/broadening processes present in realistic experimental conditions. In principle, another term should be added to account for the photonic part of the absorption/emission, which is proportional to Âel ⊗ Bph ∼ 1el ⊗ qc = 1el ⊗ (â † + â). However, the relative magnitude of the electronic and photonic contributions in experiment is extremely reliant on the experimental setup (e.g., cavity loss, direction of the probe etc.). Other works have used different quantities to explore the cross-correlation of various observables for the spectroscopic analysis of molecular systems in cavities. In experiment, usually the photonic contribution to the absorption and emission will dominate the intensity of the spectrum in Fabry-Pérot-type cavities. however, for theoretical calculations, the excitonic absorption spectra expressed here and in other works is better-suited to understand the effects of the cavity on the electronic sub-system and gives more direct insight into the local reactivity and electronic reorganization in the molecule upon excitation.