The presence of a plasmonic nanoparticle strongly affects the optical response of molecules, leading to significant effects such as surface enhanced Raman scattering, surface enhanced infrared absorption and metal enhanced fluorescence. Moreover, in recent years plasmonic metallic nanostructures have emerged as a new family of photocatalysts, enhancing rates and increasing selectivity of important chemical reactions such as H2 splitting and CO2 reduction to methane. The theoretical modelization of these phenomena is especially challenging due to the inherent multiscale nature of the system. Recently [1], the simulation of the simultaneous electronic dynamics of molecule and nanoparticle has been achieved by combining a time-dependent configuration interaction approach for the molecule, and a description of the nanoparticle as a continuous  dielectric of given shape and dielectric function. In this work we extend this approach to the description of the molecule’s electronic structure and neutral excited states at the GW-BSE level. Here we show the application of these combined methodologies to the study of Rabi oscillations of the ground and excited states population of a LiCN molecule, an ideal test system for the study of optical dipole switching. The molecule is set at increasing distances with respect to a spherical plasmonic nanoparticle probing the local field enhancement and the strength of the mutual interaction. The population and dipole dynamics of the prototypical push–pull PNA molecule in proximity of a tip-shaped nanoparticle is studied as well, looking at the different responses that are obtained when the tip scans the different positions on the molecule. Finally preliminary results on plasmon enhanced CO2 photoreduction will be discussed.

[1] S Pipolo, S Corni, The Journal of Physical Chemistry C 120 (50), 28774-28781