The average FLI in Fig. indicates that there is reduced chaoticity over the T = 1 ps timescale which can be due to the emergence of regular structures and partial barriers in the classical phase space at certain cavity frequencies. The key question here, based on the correspondence observed in Fig. , is whether the variations of quantum ⟨P iso ⟩ with the cavity frequency is related to such changes in the classical phase space structure. It is well known in the context of several classical-quantum correspondence studies of conservative Hamiltonian systems that depending upon the position of the initial polaritonic wavepacket, emergence of regular structures in the phase space can form barriers to the evolution of the wavepacket and thereby suppress the isomerization probability. In this section we show that the presence or absence of certain features in the phase space does have implications for the extent to which the quantum isomerization is mediated by coupling to the cavity.