Translational dynamics of photoexcited atoms in He-4 nanodroplets: the case of silver

The dynamics following the photoexcitation of Ag atoms in He-4 nanodroplets via the 5p P-2(1/2) <- 5s S-2(1/2) and 5p P-2(3/2) <- 5s S-2(1/2) transitions has been investigated in a joint experimental and theoretical effort. It has been experimentally found that upon excitation to the P-2(1/2) state, the Ag atoms are ejected with a speed distribution peaking at about 55 m s(-1). When Ag is excited to the P-2(3/2) state, a rich phenomenology is found. While a fraction of the impurities remains solvated, the impurities that are ejected from the droplets either as Ag or AgHe have speed distributions similar, but not identical, to those found for excitation to the P-2(1/2) state. The experimental findings are qualitatively analyzed within a three-dimensional, time-dependent density functional approach for the helium droplet. The dynamics of the Ag-He-4(1000) system has been followed for several tens of picoseconds, long enough to observe AgHe exciplex formation and the departure of the photoexcited Ag atom from the helium droplet.