Alkali-metal electron spin density shift induced by a helium nanodroplet

Markus Koch (1) , Carlo Callegari (1, 2) , Wolfgang E. Ernst (1)

1 Institute of Experimental Physics [Graz]
2 Sincrotrone Trieste

Helium (He) nanodroplets provide a cold and virtually unperturbing environment for the study of weakly bound molecules and van der Waals aggregates. High resolution microwave spectroscopy and the detection of electron spin transitions in doped He droplets have recently become possible. Measurements of hyperfine-resolved electron spin resonance in potassium (³⁹K) and rubidium (⁸⁵Rb) atoms on the surface of He droplets show small line shifts relative to the bare atoms. These shifts were recorded for all 2I+1 components (I is the nuclear spin) of a transition at high accuracy for He droplets ranging in size from 1000 to 15000 He atoms. Evaluation of the spectra yields the influence of the He environment on the electron spin density at the alkali-metal nucleus. A semiempirical model is presented that shows good qualitative agreement with the measured droplet size dependent increase of Fermi contact interaction at the nuclei of dopant K and Rb.

Mots clés: Physical Sciences

Markus Koch, Carlo Callegari, Wolfgang E. Ernst. Alkali-metal electron spin density shift induced by a helium nanodroplet. Molecular Physics, 2010, 108 (07-09), pp.1005-1011. ⟨10.1080/00268971003623401⟩. ⟨hal-00596286⟩