Düsseldorf 2007 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 30: Poster: Spectroscopy in He droplets
MO 30.3: Poster
Dienstag, 20. März 2007, 16:30–18:30, Poster A
Modelling the shift and broadening of absorption lines of alkali metal atoms attached to helium nanodroplets — •Severin Müller1, Oliver Bünermann1, Frank Stienkemeier1, and Manuel Barranco2 — 1Universität Freiburg, Physikalisches Institut, D-79104 Freiburg, Germany — 2Departament E.C.M., Facultat de Física, Universitat de Barcelona, E-08028, Spain
In the context of helium nanodroplets alkali metal atoms are of special interest. Whereas most picked up atoms submerge in the liquid helium droplets, alkali metals reside in a dimple on the surface. The absorption spectra of the first electronic state of all stable alkali atoms are experimentally available. Though theory already addressed these systems, the shifts and broadenings of the spectra are still not fully understood. We applied a simple model treating the system droplet-alkali atom as a diatomic molecule to calculate the helium-induced shift and broadening of excitation lines. The helium density distribution of the alkali-helium droplet system used in these calculations are taken from data derived from density functional theory by M. Barranco et al [1]. In this way we are able to attribute the splitting of absorption lines and a shoulder of the absorption on the red side of the main line to the excitation to different vibrational modes of the alkali-helium molecular system. Furthermore, the droplet size dependence and the influence of the helium isotope on the absorption spectra of light alkali atoms can be reproduced.
[1] F. Stienkemeier, O. Bünermann, R. Mayol, F. Ancilotto, M. Barranco and M. Pi, Phys. Rev. B 70, 214509 (2004)