Evidence for Superfluidity in Para-Hydrogen Clusters Inside Helium-4 Droplets at 0.15 Kelvin

Grebenev, Slava; Sartakov, Boris G.; Toennies, J. P.; Vilesov, A. F.

doi:10.1126/science.289.5484.1532

Cited by 224 publications

(226 citation statements)

References 25 publications

(9 reference statements)

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“…Rovibrational IR spectroscopy experiments with chromophores in helium droplets [1,2] have confirmed superfluid behavior for systems as small as approximately 60 4 He atoms [3] by observing the free rotation of the OCS molecule. Subsequently, a new field of research has been opened by similar experiments in small para-hydrogen clusters embedded in low temperature helium droplets.…”

Section: Introductionmentioning

confidence: 96%

“…Subsequently, a new field of research has been opened by similar experiments in small para-hydrogen clusters embedded in low temperature helium droplets. [4] Spectroscopic experiments on OCS in these hydrogen clusters show spectroscopic anomalies which have been interpreted as indicating the existence of superfluidity of para-H 2 for clusters small enough to be fluidlike rather than forming a solid shell around the chromophore. These conclusions have recently been verified by path integral calculations showing that an anistropic superfluid fraction appears at low temperatures (T < 0.3 K).…”

Section: Introductionmentioning

confidence: 99%

“…Many aspects of superfluidity have been studied experimentally, phenomenologically, and theoretically. These include its relation to Bose-Einstein condensation, the temperature dependence of the superfluid fraction in the 2-fluid model, the finite size-dependence and the influence of atomic and molecular impurities in 4 He on the superfluid fraction. The latter two issues have raised new, interesting and more basic questions.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of rotational energies and rigidity of OCS–para-H2 and OCS–4He complexes

Zillich¹,

Whaley²

2003

Chemical Physics

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We analyze the nature of the rotational energy level structure of the OCS-He and OCS-H 2 complexes with a comparison of exact calculations to several different dynamical approximations. We compare with the clamped coordinate quasiadiabatic approximation that introduces an effective potential for each asymmetric rotor level, with an effective rotation Hamiltonian constructed from ground state averages of the inverse of the inertial matrix, and investigate the usefulness of the Eckart condition to decouple rotations and vibrations of these weakly bound complexes between linear OCS and 4 He or H 2 . Comparison with exact results allows an assessment of the accuracies of the different approximate methods and indicates which approaches are suitable for larger clusters of OCS with 4 He and with H 2 . We find the OCS-H 2 complex is considerably more rigid than the OCS-He complex, suggesting that semi-rigid models are useful for analysis of larger clusters of H 2 with OCS.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of rotational energies and rigidity of OCS–para-H2 and OCS–4He complexes

Zillich¹,

Whaley²

2003

Chemical Physics

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“…At the microscopic scale, pH 2 also joins the club. These two discoveries [8,9] triggered a wave of research in the area of microscopic superfluidity. The rapid advance in this field justifies the present minireview focused on the theoretical approaches used in the relevant studies.…”

Section: Introductionmentioning

confidence: 99%

“…A couple of years subsequent to these observations, a similar superfluid phenomenon was observed, this time involving para-H 2 (pH 2 ) clusters doped with an OCS chromophore and embedded in Helium nanodroplets. [9] For OCS(pH 2 ) 14,15,16 , as T drops from 0.38 to 0.15 K, the Q-branches of their rovibrational spectra disappear, indicating null rotational inertia along the OCS axis. This suggests a superfluid fraction of 100% of the pH 2 's around the axis.…”

Section: Introductionmentioning

confidence: 99%

Potential generation and path‐integral Monte Carlo in study of microscopic superfluidity

Zeng

Roy

2014

Int J of Quantum Chemistry

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The idea of a macroscopic Andronikashvili experiment used to measure superfluid fraction of bulk liquid 4 He can be ported into the realm of spectroscopic studies to measure the superfluid fraction of microscopic systems at the nanoscale. Theoretical studies are needed to fully unravel the superfluid information contained in such a microscopic Andronikashvili experiment. Two aspects of the theoretical studies, the generation of accurate and efficient potential energy surfaces, and the methodology of path-integral Monte Carlo simulations are briefly introduced in this article.

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Fourier Transform Microwave Spectroscopy of Doped Helium Clusters

Jäger

2011

Handbook of High‐resolution Spectroscopy

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In this article, we describe investigations of rotational spectra of complexes and clusters containing helium atoms. These systems are of much interest mainly because of their very low binding energies and the associated relatively large zero‐point energies. As a result, these very weakly bonded systems undergo large amplitude internal stretching and bending motions and the semirigid rotor Hamiltonian can often not describe the spectra appropriately. Microwave spectra of clusters of the type He N ‐linear molecule are discussed. The number of helium atoms in the cluster, N , ranges from 1 up to 39 in the case of He N ‐carbonyl sulfide. It was possible to record transitions of clusters of successively increasing size and to extract spectroscopic parameters of clusters with atom‐by‐atom resolution. Probably the most significant outcome from these studies is the observation of an increase in the rotational constant, B , with increasing N . This turnaround occurs at relatively small numbers of helium atoms, e.g., N = 9 for He N ‐OCS. The corresponding decrease in moment of inertia with increasing N is attributed to a decoupling of helium density from the rotational motion of the dopant molecule. This is interpreted in terms of the occurrence of superfluid effects on the microscopic scale. Throughout the article, we emphasize the importance of our colleagues in infrared spectroscopy and theory collaborating in this research endeavor.

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Evidence for Superfluidity in Para-Hydrogen Clusters Inside Helium-4 Droplets at 0.15 Kelvin

Cited by 224 publications

References 25 publications

Comparison of rotational energies and rigidity of OCS–para-H2 and OCS–4He complexes

Comparison of rotational energies and rigidity of OCS–para-H2 and OCS–4He complexes

Potential generation and path‐integral Monte Carlo in study of microscopic superfluidity

Fourier Transform Microwave Spectroscopy of Doped Helium Clusters

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