Energy relaxation and quenching processes of doped rare-gas clusters with a shell-like geometric structure.

Energy relaxation processes of photo-excited Kr50 clusters covered with a shell of Ar atoms (up to 40)which are embedded inside large Ne7500 clusters are investigated with energy resolved fluorescence spectroscopy. In the energy range of the characteristic Ne cluster absorption (16.5–18eV) a strong energy transfer to the embedded Kr cluster is observed, which results in the desorption of electronically excited Kr* atoms. Kr* atoms move through the Ne cluster, desorb and emit visible and near-infrared light in the vacuum (5p→5s). By coating the Kr clusters with Ar atoms, the Kr lines disappear and 4p→4s transitions of Ar* become dominant. Additionally, new emission bands occur, which are assigned to transitions of perturbed atomic Kr 5p-states inside Ne clusters.Due to the interaction of electronically excited Kr* atoms with neutral Ar atoms in the surrounding shell, several excited Kr states namely 5p [1/2]0 and 5p [3/2]2 decay nonradiatively. This is in agreement with the well-known "energy-gap law." The results give experimental evidence that clusters with a multishell structure can be prepared by a sequential pick-up technique. This allows the preparation of Kr clusters embedded inside Ne clusters and coated with a shell of Ar atoms. Such clusters cannot be prepared with conventional coexpansion techniques.