The ensuing nuclear dynamics can be described by a wavefunction of the form (19) where describes the time evolution of a nuclear state that moves on the excited potential surface of molecule j starting from . Outside the cavity this leads an evolution similar to the separation of nuclear trajectories in a post-conical-intersection evolution as nuclear states moving on different potential surfaces fall out of overlap with each other. In the presence of coupling to a cavity mode the situation is more complicated. Denoting the ground and singly excited cavity states by and respectively, the zero-order (in the molecule-cavity interaction) states and couple to form a collective polariton whose vibrational component is with a polaritonic splitting of order . If the nuclear motion proceeds according to Eq. ( ) this collective nature of the coupling is lost because each component of ( ) when combined with the cavity state, namely the state is now coupled to an excited cavity state dressed by a different vibrational state . Once the overlap between different vibrational states decays, the Rabi splitting loses its collective order and becomes of order 1, namely of the magnitude of a single molecule coupling to the radiation field.