With the efficient integration scheme for the electronic Schrodinger equation in place, we are now ready to analyze the high-lying excited state dynamics of the H 2 -Ag 20 scattering problem. First, we focus on the CIS excitation spectrum. At this level of theory, the spectrum of a tetrahedral Ag 20 nanoparticle has a strong peak around ≈ 3.56 eV, which originates from a collective electronic excitation in analogy to a localized surface plasmonic resonance. Since our initial geometry positions the H 2 molecule far away from Ag 20 , the initial spectrum (Fig. ) almost replicates the spectrum of an isolated Ag 20 cluster.