The non-adiabatic transition from the donor to the acceptor state can be modulated by coupling to a cavity, following the same principles using PFS discussed above. As discussed before, the diabatic coupling V DA • 0 D |0 A will be reduced, which modulates the non-adiabatic transition near the barrier at R = 0. In particular, the splitting at the avoided crossing decreases with an increase in the lightmatter coupling strength. This is illustrated in the inset in Fig. , which shows that the splitting gradually decreases with an increase in χ. Near the barrier, the lowest two polariton states approach the acceptor and donor diabatic states. In the limit of infinite light-matter coupling, the avoided crossing between the lowest two PES becomes a conical intersection as the donor and acceptor state become decoupled.