Minimum sizes for the submersion of alkali clusters into liquid helium

Abstract

Alkali atoms do not stably embed in liquid helium-4 because the interatomic attractive potential is unable to overcome the short-range Pauli repulsion of the s electrons and the surface tension cost of the surrounding bubble. Similarly, small alkali complexes reside on the surface of helium nanodroplets instead of inside. However, as the size of the metal cluster increases, its van der Waals attraction to the helium matrix grows faster than the repulsive energies and above a certain size it should become favorable for clusters to submerge in the liquid. Based on an evaluation of the relevant energy terms, we characterize the bubble dimensions and estimate the critical submersion sizes. The latter range from N~20 for Li_N and Na_N to N>100 for Rb_N in helium-4 and from N~5 for Li_N and Na_N to N~20 for Cs_N in helium-3. These results are discussed in the context of nanodroplet pick-up experiments with alkali atoms

Replaced with revised version

References in corpus (4)

• Spectroscopy and dynamics in helium nanodroplets
• Surface location of sodium atoms attached to He-3 nanodroplets
• Surface location of alkaline-earth atom impurities on helium nanodroplets
• Evaporative attachment of slow electrons to alkali nanoclusters

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• Quantum-State-Sensitive Detection of Alkali Dimers on Helium Nanodroplets by Laser-Induced Coulomb Explosion
• Fission of Multiply Charged Cesium and Potassium Clusters in Helium Droplets - Approaching the Rayleigh Limit
• Desorption Dynamics of Rb_2 Molecules off the Surface of Helium Nanodroplets
• Probing the presence and absence of metal-fullerene electron transfer reactions in helium nanodroplets by deflection measurements