We now turn to the issue of cavity modification of isomerization when initially there are no photons present in the cavity. In Fig. (b), the ⟨P iso ⟩ for three choices of the wavepacket center with fixed η = 0.06 are shown. In contrast to the virtual photon case shown in Fig. , quantum mechanically all three initial states exhibit suppression of isomerization. However, the initial state with q i = -0.439 au exhibits a significant suppression compared to the other two states. Nevertheless, the ⟨P iso ⟩ scaled by the respective cavity-off values shown in Fig. (b) indicates similar suppression factors for q i = -0.439 au and q i = -0.602 au cases. As discussed previously, this has to do with the fact that the uncoupled isomerization probability is much smaller for the q i = -0.602 case. A key point to note here is that the suppression in quantum ⟨P iso ⟩ occurs closer to the transition frequency ω 10 and the average photon number shown in Fig. (c) undergoes coherent ∼ 250 fs oscillations. Note that this is close to the ∼ 270 fs timescale predicted from the ∼ 123 cm -1 Rabi splitting for η = 0.06. Our computations, not shown here, indicate that the timescale of these coherent oscillations in ⟨n c ⟩(t), and hence the average system energy ⟨H S ⟩(t), are consistent with the Rabi splittings observed for other values of the cavity-system coupling strength. Interestingly, a similar timescale is observed in Fig. (low frequency component) for the q i = -0.9 au initial state.