Fig. (a) presents the ratio k 1 /k 1,0 as a function of the cavity frequency ω c for the first molecule of the heterodimer in a parallel dipole configuration inside the cavity. Fig. ) is for the second molecule. A stronger light-matter coupling η c = 0.005 a.u. is employed in this context. For comparison, the results of the corresponding single molecule inside the cavity are depicted as dotted lines in Fig. . In contrast to the homodimer (see Fig. ), the reaction rates of two dif-ferent molecules simultaneously coupled to the same cavity mode exhibit little change, as compared to the single molecule inside the cavity. This is because the reaction channel shown in Fig. ) is no longer feasible in a heterodimer. To understand this, we can take a cavity mode with ω c = 1200cm -1 as an example. While the absorption of a photon is coupled to the emission of a phonon in the first molecule, the simultaneous emission of a photon can't excite the second molecule due to the energy mismatch, as illustrated in Fig. ). Similarly, the vibrational transition in the second molecule v mol 1 → v mol 2 is energetically resonant with a cavity mode of the frequency ω c = 750cm -1 , which is nevertheless off-resonant with the vibrational transitions in the first molecule, as illustrated in Fig. ).