  Plasmonic catalysis is a rapidly growing field of research, both from
experimental and computational perspectives. Experimental observations
demonstrate an enhanced dissociation rate for molecules in the presence of
plasmonic nanoparticles under low-intensity visible light. The hot-carrier
transfer from the nanoparticle to the molecule is often claimed as the
mechanism for dissociation. However, the charge transfer time scale is on the
order of few femtoseconds and cannot be resolved experimentally. In this
situation, ab initio non-adiabatic calculations can provide a solution. Such
simulations, however, have their own limitations related to the computational
cost. To accelerate plasmonic catalysis simulations, many researchers resort to
applying high-intensity external fields to nanoparticle-molecule systems. Here,
we show why such an approach can be problematic and emphasize the importance of
considering strong-field effects when interpreting the results of
time-dependent density functional theory simulations of plasmonic catalysis. By
studying the hydrogen molecule dissociation on the surface of a silver
nanoshell and analyzing the electron transfer at different field frequencies
and intensities, we demonstrate that the molecule dissociates due to
multiphoton absorption and subsequent ionization.
