Outside the cavity, the initial value of anisotropy is ~0.06 for exciting the a2" modes (Fig. ), suggesting that pseudorotation dominates over IVR. However, under VSC, the opposite trend is observed: the anisotropy starts at ~-0.08 for exciting UP (Fig. ). This contrast indicates that, under VSC, IVR dominates over pseudorotation. Not surprisingly, when pumping the a2" dark modes under VSC, the anisotropy is ~0.06 (Fig. ), like the cavity-free case. To determine the rate constants of pseudorotation and IVR, a more detailed kinetic model was developed (see SI Section 2.4) .The anisotropy can be calculated based on the energy exchange dynamics simulated from the kinetic model. Fitting the measured anisotropy dynamics to the kinetic model, we determined the rate constants for pseudorotation (kps) and IVR (kIVR) to be 0.035±0.001 and 0.024±0.001 ps -1 , respectively, outside the cavity (Fig. ) and 0.022±0.005 and 0.043±0.002 ps -1 under VSC (Fig. ). The former results qualitatively agree with previous work showing that pseudorotation dominates the dynamics outside a cavity , except now we quantify the relative contribution of IVR. The quantitative results agree with the qualitative analysis above, indicating that VSC shifts the balance between pseudorotation and other energy exchange channels: outside the cavity, exciting the a2" mode yields dynamics where pseudorotation dominates over IVR, while under VSC, exciting the UP promotes IVR and suppresses pseudorotation; yet, under VSC, exciting the a2" dark modes does not change the dynamics relative to molecules outside the cavity. We note that this effect is VSC-exclusive, as weak coupling to the cavity does not lead to the modification of the dynamics (SI section 3.4); further, the acceleration of energy transfer and promotion of IVR through VSC is robust against different solvent environments (see results for 1-octanol ,SI Section 3.9).