We describe a measurement of the transmission probability of 4He atoms through a freely suspended slab of superfluid 4He at low temperatures. In our experiment the slab is realized by using an array of parallel cylindrical holes of diameter 51 microm in a glass disc of thickness 190 microm. By controlling the chemical potential, the holes can be made to fill or empty with liquid, and the surface curvature varied. We have measured the transmission of atom beams, generated by a thin-film heater and detected with a sensitive bolometer, through this structure. The results show that the dominant transmission channel is atom-R+ roton-atom with a probability p approximately 0.12 and that R+ rotons can undergo total internal reflection at the free liquid surfaces.We describe a measurement of the transmission probability of 4He atoms through a freely suspended slab of superfluid 4He at low temperatures. In our experiment the slab is realized by using an array of parallel cylindrical holes of diameter 51 microm in a glass disc of thickness 190 microm. By controlling the chemical potential, the holes can be made to fill or empty with liquid, and the surface curvature varied. We have measured the transmission of atom beams, generated by a thin-film heater and detected with a sensitive bolometer, through this structure. The results show that the dominant transmission channel is atom-R+ roton-atom with a probability p approximately 0.12 and that R+ rotons can undergo total internal reflection at the free liquid surfaces.

Physical Review LettersAug 18, 20039 citations

Helium and Other Two Electron Systems

Ingolf Volker Hertel, Claus-Peter Schulz

Graduate texts in physicsOct 24, 20141 citation

Optical Excitation of Atomic Hydrogen Bound to the Surface of Liquid Helium

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.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.

Physical Review LettersNov 16, 199822 citations

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.