In Fig. , we compare the rate profile, k/k 0 against ω c of the homodimer in both orientations to that of a single molecule inside the cavity. Here, k 0 is the reaction rate of a single molecule outside the cavity. The panels (a) and (b) correspond to the light-matter interaction η c = 0.00125 a.u. and η c = 0.005 a.u. , respectively. Although the rate is further increased due to the collective effect in both cases, it is only significant when the light-matter coupling is stronger. Over the entire frequency regime, this collective effect-induced rate enhancement is independent of whether the dimer is in the parallel and anti-parallel dipole configuration.