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The excited state dynamics of silver atoms embedded in helium nanodroplets were investigated by various spectroscopic techniques.

The dynamics of laser-excited sodiumatoms at the surface of heliumnanodroplets has been investigated as a function of quantum state.For all cases, excitation of the system leads to desorption of thesodium atom from the droplet surface. The mean kinetic energy of thedesorbed atoms scales linearly with excitation frequency, indicativeof an impulsive desorption process. The energy partitioning betweenthe helium and the desorbing sodium atom depends on the quantum stateand appears to be related to the size and shape of the electron orbital.The speed distributions of desorbed NaHe exciplexes point toward adirect formation process of an exciplex with no internal energy. Photoelectronspectroscopy reveals an increasing importance of helium-induced relaxationwith increasing quantum state, which is tentatively attributed tocurve crossing between different NaHeNinteraction potentials during the desorption process. [ABSTRACT FROM AUTHOR]

Examples of the behaviour of highly vibrationally excited molecules using the PUMP, DUMP and PROBE technique are presented.

The dynamics of Na atoms on the surface of helium nanodroplets following excitation via the 3p ← 3s transition has been investigated using state-specific ion-based detection of the products. Excitation of the system to the 3p (2)Π states is found to lead to the desorption of both bare Na and NaHe exciplexes. The associated speed distributions point to an impulsive desorption process for Na products and a thermally driven process for the NaHe exciplexes. In contrast, excitation of the 3p (2)Σ state leads exclusively to the impulsive desorption of Na atoms. In this case, the desorption is accompanied by a helium-induced relaxation process, as evidenced by the large fraction of detected Na (2)P1/2 atoms. The relaxation process is thought to be related to a crossing between the (2)Π1/2 and (2)Σ potential energy curves at large distance.

Helium nanodroplets are widely used as a cold, weakly interacting matrix for spectroscopy of embedded species. In this work, we excite or ionize doped He droplets using synchrotron radiation and study the effect onto the dopant atoms depending on their location inside the droplets (rare gases) or outside at the droplet surface (alkali metals). Using photoelectron-photoion coincidence imaging spectroscopy at variable photon energies (20-25 eV), we compare the rates of charge-transfer to Penning ionization of the dopants in the two cases. The surprising finding is that alkali metals, in contrast to the rare gases, are efficiently Penning ionized upon excitation of the (n = 2)-bands of the host droplets. This indicates rapid migration of the excitation to the droplet surface, followed by relaxation, and eventually energy transfer to the alkali dopants.