Liquid-vapor density profile of helium: An x-ray study

Lurio, Laurence; Rabedeau, T. A.; Pershan, Peter S.; Silvera, Isaac F.; Deutsch, Moshe; Kosowsky, S. D.; Ocko, B. M.

doi:10.1103/physrevlett.68.2628

Cited by 73 publications

(44 citation statements)

References 24 publications

(36 reference statements)

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“…It was shown in experiments that the vertical thickness within which the density changes from 90 to 10% of the bulk liquid density increases slightly with temperature from 1.4 to 2.1 K , with an average value of 9.4 Å at 1.8 K. There was also evidence of a rise of up to 3 Å between 2.1 K and the superfluid transition temperature (l point). A very close value for the vertical thickness, of (9.2 ± 1) Å at 1.13 K, was obtained in experiments where liquid-vapor density profiles of thick 4 He films were measured using x-ray reflectivity [2]. The surface tension of liquid helium can be measured by various experimental methods [3,4] and may be compared directly with the values derived from theoretical models [5,6].…”

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confidence: 58%

Neutron reflection from a liquid helium surface

Charlton

Dalgliesh

Kirichek

et al. 2008

Low Temperature Physics

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The reflection of neutrons from a helium surface has been observed for the first time. The 4 He surface is smoother in the superfluid state at 1.54 K than in the case of the normal liquid at 2.3 K. In the superfluid state we also observe a surface layer~200 Å thick which has a subtly different neutron scattering cross-section, which may be explained by an enhanced Bose-Einstein condensate fraction close to the helium surface. The application of neutron reflectometry described in this paper creates new and exciting opportunities for the surface and interfacial study of quantum fluids.

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confidence: 58%

Neutron reflection from a liquid helium surface

Charlton

Dalgliesh

Kirichek

et al. 2008

Low Temperature Physics

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“…Zero-point and thermal ripplons on the helium surface [19] contribute to the diffuse surface or interfacial profile [20,21]. The electrons also react adiabatically to ripplons.…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent energy levels of electrons on liquid helium

et al. 2017

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We present measurements of the resonant microwave absorption between the Rydberg energy levels of surface state electrons on the surface of superfluid liquid helium, in the frequency range 165 -220 GHz. The resonant frequency was temperature dependent. The experiments are in agreement with recent theoretical calculations of the renormalisation of the electron energy levels due to zero-point and thermal ripplons. The temperature-dependent contribution to the linewidth γ(T) for excitation to the first excited state at 189.6 GHz is compared with other measurements and theoretical predictions. PACS number(s): 73.50.Fq

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“…X-ray and neutron reflectivity have been extensively used to determine the density profiles at the free surfaces of many liquids [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] including water, 22,25 and also at liquid-solid [26][27][28] and liquidliquid [29][30] interfaces. These probes are sensitive to electron density and scattering length density respectively, and for a known material these are both measures of the local mass density.…”

Section: Introductionmentioning

confidence: 99%

What x rays can tell us about the interfacial profile of water near hydrophobic surfaces

et al. 2013

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The free surface of water, and the interface between water and a hydrophobic surface, both have positive interface energies. The water density near a free surface drops below the bulk density, and thus it is expected that water near a hydrophobic surface will also show a density depletion.However, efforts by multiple groups to detect and characterize the predicted 'gap' at waterhydrophobic interfaces have produced contradictory results. We have studied the interface between water and fluoroalkylsilane self-assembled monolayers using specular X-ray reflectivity, and analyzed the parameter-space landscapes of the merit functions being minimized by data fitting. This analysis yields a better understanding of confidence intervals than the customary process of reporting a unique 'best' fit. We conclude that there are unambiguous gaps at water-hydrophobic interfaces when the hydrophobic monolayer is more densely packed.

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Liquid-vapor density profile of helium: An x-ray study

Cited by 73 publications

References 24 publications

Neutron reflection from a liquid helium surface

Neutron reflection from a liquid helium surface

Temperature-dependent energy levels of electrons on liquid helium

What x rays can tell us about the interfacial profile of water near hydrophobic surfaces

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