Photochemistry in plasmonic cavities: From perturbative to strong coupling regime

We explore the spectroscopic signatures and photo-product energy redistribution in a photodissociating molecule electronically coupled to a plasmonic cavity. Using quantum dynamical simulations, we identify two types of chemical fingerprints that depend on the coupling strength between the cavity mode and the dissociating molecule. In the perturbative regime, the molecule undergoes Raman-like transitions that can be revealed from the modified kinetic energy distribution of the fragments. In the strong-coupling regime, the final vibrational energy distribution of the fragments becomes dependent on which plasmonic-excitonic (plexcitonic) branch, either upper or lower, is excited by the incoming radiation. Thus, narrowband excitation of plexcitonic states enables direct control over the vibrational energy distribution of the photo-products. Both mechanisms are highly sensitive to red-detuning of the cavity mode relative to the electronic resonance. We illustrate these effects by fully quantum simulation of the photo-fragmentation of the prototype NOCl molecule coupled to a plasmonic cavity mode using the MCTDH method.