Figure 2.

Rabi dispersion relation for parahelium in a cavity. The bright polaritonic states, located at the ΔE = E_2P – E_2S resonance frequency (vertical line) of the uncoupled system, are indicated by the two horizontal lines. They are associated with a high (red) dipole transition oscillatory strength, while corresponding dark many-photon replicas and improbable 2S – iS transitions have a small oscillator strength (blue). The yellow crosses (+) indicate energies derived from the JC model based on a 2S and 2P two-level approximation and using the respective parameters for the cavity detuning frequencies and photon mode numbers.