There is also a small peak at 1255cm -1 , which is not readily visible with η c = 0.00125 a.u. , but becomes more apparent when the light-matter coupling strength is increased to η c = 0.005 a.u. . It is related to the vibrational transitions, v mol 0 ↔ v mol 5 and v mol 1 ↔ v mol 4 . Besides, two peaks in the lower frequency regime merge and form a strong peak in the middle at 555cm -1 for the stronger η c = 0.005 a.u. , due to the additional broadening effect brought in by the cavity mode and the cavity bath. It is worth noting that a photon with the frequency ω c = 660cm -1 induces the vibrational transitions v mol 0 ↔ v mol 3 and v mol 1 ↔ v mol 2 , opening up a cotunneling path. However, we don't observe a conspicuous peak in Fig. (c) at the supposed frequency. This is because the tunneling rate from the left well to the right well on the states |v mol 2 ⟩ and |v mol 3 ⟩ is much slower than the reaction rate outside the cavity k 0 . As such, the rate enhancement effect is nearly negligible.