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We present theoretical studies of helium droplets and films doped with one electronically excited rubidium atom Rb* both in first and second excited states. Diffusion and path integral Monte Carlo approaches are used to investigate the energetics and the structure of clusters containing up to 14 helium atoms, and the surface of large clusters is approximated by a helium film. The stable structure of Rb*Hen in the first excited state consists of a 7 helium atom ring centered at the rubidium, surrounded by a tire-like second solvation shell. A very different structure is obtained when performing a "Monte Carlo vertical transition". In this approach, a path integral Monte Carlo equilibration is starting from the stable configuration of a rubidium atom in the electronic ground state adsorbed to the helium surface after switching to the electronically excited surface. In this case, Rb*Hen relaxes to a weakly bound meta-stable state in which Rb* sits in a shallow dimple. The interpretation of the results is consistent with experimental observations [G. Auböck et. al., Phys. Rev. Lett. 101, 035301 |
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