Rydberg atom at the surface of liquid helium

Sergey K. Sekatskii

Giovanni P. Arrighini, Franco Biondi, Carla Guidotti

A. Hitachi

Allard P. Mosk, M. W. Reynolds, Tom W. Hijmans

We investigate deuterium atoms adsorbed on the surface of liquid helium in equilibrium with a vapor of atoms of the same species. These atoms are studied by a sensitive optical method based on spectroscopy at a wavelength of 122 nm, exciting the 1S-2P transition. We present a direct measurement of the adsorption energy of deuterium atoms on helium and show evidence for the existence of resonantly enhanced recombination of atoms residing on the surface to molecules.

W. Vassen, C.F.A. Karremans, Annemieke Kips +1 more

Allard P. Mosk, M. W. Reynolds, Tom W. Hijmans +1 more

We have optically detected hydrogen atoms adsorbed on the surface of liquid helium, a system relevant for the study of Bose degeneracy in two dimensions. The atoms are excited by $121.6$ nm light and detected both in fluorescence and in absorption. The excitation spectrum shows a resonance that is much broader than that of a free atom, and shifted to lower frequencies. From the absorption signal we determine that we have reached a surface density corresponding to one atom per square de Broglie wavelength. We also use the hydrogen fluorescence to probe the thermal resistance between the free surface and the bulk of the liquid helium.