Rotationally Resolved Spectroscopy of S<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">F</mml:mi></mml:mrow><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>in Liquid Helium Clusters: A Molecular Probe of Cluster Temperature

Hartmann, Matthias; Miller, R. E.; Toennies, J. P.; Vilesov, A. F.

doi:10.1103/physrevlett.75.1566

Cited by 573 publications

(642 citation statements)

References 26 publications

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“…3 He atoms has been chosen so as to fill a shell of their single-particle spectrum. Figure 8 shows the same magnitudes for the cluster 4 He 70 ϩ SF 6 . We may notice in these two pictures a slight tendency of 3 (r) to penetrate more deeply into the pure host cluster.…”

Section: The Case Of Pure and Doped 4 He Droplets With Variable Nsupporting

confidence: 57%

“…An interesting property, already observed by Dalfovo,20 is that as the number of nodes of the 3 He radial wave functions increases, the corresponding probability densities ͉R nl (r)͉ 2 drift towards smaller rms radii; in particular, we find that while ͉R 1s (r)͉ 2 remains centered at distances slightly larger than the rms radius of the cluster, at least for the values of N 4 here considered, the 3s wave functions penetrate the drop if N 4 is above 200. Figure 4 is similar to the former for 4 He drops doped with SF 6 , but only the energies of s states are shown, since the energies of the lowest lying l levels rapidly become degenerate as the 4 He drop grows above a few tens of particles. In this case we appreciate that the distortion of the SP potential provided by the external field associated to the molecular impurity is important for the smallest drops, namely, for N 4 below 300.…”

Section: Systematics Of a Single 3 He Atom In Pure And Doped 4 Hmentioning

confidence: 59%

“…5-11, and references therein͒. The major outcomes of that body of work are to have established the location of the impurity in the bulk of the drop, and the fact that due to their low temperature, which is around 0.4 K for 4 He, 6 liquid drops provide useful ultracold matrices well suited for high resolution molecular spectroscopy. That temperature is even lower in the case of 3 He, some 0.15 K, 12 in good agreement with the predictions of Ref.…”

Section: Introductionmentioning

confidence: 99%

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Structure and energetics of mixed4He-3He drops

et al. 1997

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Using a finite-range density functional, we have investigated the energetics and structural features of mixed helium clusters. The possibility of doping the cluster with a molecule of sulfur hexafluoride is also considered. It is seen that the repulsion introduced by the impurity strongly modifies the properties of the smallest drops. Although only a qualitative comparison is possible, the gross features displayed by our calculations are in agreement with recent experimental findings. ͓S0163-1829͑97͒02438-7͔

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Section: The Case Of Pure and Doped 4 He Droplets With Variable Nsupporting

confidence: 57%

Section: Systematics Of a Single 3 He Atom In Pure And Doped 4 Hmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

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Structure and energetics of mixed4He-3He drops

et al. 1997

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“…SF 6 is known to reside inside helium droplets. [12,24] On the other hand alkali-metal atoms and small alkali-metal clusters sit in a dimple on the surface of a helium droplet because the repulsive interaction between the dopant and the helium is too large to allow an interior location. [25] We have shown elsewhere that once Na n clusters reach a threshold size (n !…”

Section: Methodsmentioning

confidence: 99%

Electron‐Driven Self‐Assembly of Salt Nanocrystals in Liquid Helium

Daxner¹,

Denifl²,

Scheier³

et al. 2014

Angewandte Chemie

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The self-assembly of salt nanocrystals from chemical reactions inside liquid helium is reported for the first time. Reaction is initiated by an electron impacting a helium nanodroplet containing sodium atoms and SF 6 molecules, leading to preferential production of energetically favorable structures based on the unit cell of crystalline NaF. These favorable structures are observed as magic number ions (anomalously intense peaks) in mass spectra and are seen in both cationic and anionic channels in mass spectra, for example, (NaF) n Na + and (NaF) n F À . In the case of anions the self-assembly is not directly initiated by electrons: the dominant process involves resonant electron-induced production of metastable electronically excited He À anions, which then initiate anionic chemistry by electron transfer.Neutral and ionic alkali-metal halide clusters have been widely studied, both experimentally and theoretically. Part of the motivation to study these species is to see if the threedimensional structures of the crystalline salts are retained in relatively small clusters. Such information can be derived from mass spectrometry through the observation of anomalously intense peaks (so-called magic number features). Several methods have been used to produce alkali-metal halide cluster ions in the gas phase, including sputtering, [1] laser ablation, [2] electrospray, [3] and ion-molecule reactions in a flowing afterglow. [4] The general finding, whether detecting cations or anions, is that enhanced signal intensity is seen for cluster ions (magic-number ions) of composition consistent with one or more complete unit cells. On these grounds it is reasonable to suppose that the cluster ions adopt structures based on the normal crystalline structure of the extended solid.Herein we show that it is possible to form alkali-metal halide clusters by reactions between clusters of sodium and SF 6 in liquid helium nanodroplets. The low intrinsic temperature (ca. 0.4 K) and the rapid cooling of dopants in these droplets, [5] which is assisted by the high thermal conductivity of superfluid helium, should inhibit chemical reactions. However, reaction between sodium and SF 6 can be triggered by electron impact on the droplet, leading to a rich range of cationic and anionic salt clusters. Particularly surprising is that self-assembly into structures based on the unit cell of NaF occurs even when the chemistry is initiated inside a liquid helium nanodroplet.The two reagents were added separately to the helium droplets, with sodium vapor coming from an oven containing solid sodium while the SF 6 was supplied from a gas cylinder. SF 6 was added to the first pick-up cell and sodium vapor to the second pick-up cell. The partial pressures of the dopants were set so that the most probable process was pick-up of a relatively small number of dopant atoms/molecules. However, the statistical nature of the pick-up process means that, in practice, clusters spanning a relatively wide range of sizes were generated. Reaction products derive...

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“…5,8 Infrared spectroscopy of these molecules shows sharp lines, indicating free rotation and apparent superfluidity of 4 He droplets. 9 Analysing rotational constants reveals extremely subtle interactions in liquids; for example, an increase of the effective moment of inertia has frequently been observed, which has been attributed to a normal liquid interface around the molecules within the otherwise superfluid 4 He droplets. [10][11][12] An extension of these exceptionally sensitive experiments to bulk helium would benefit from the much wider, and easier, control over pressure, temperature and thermodynamic phase than can otherwise be achieved in helium droplets beams, which have a fixed temperature of 0.4 K 9 (0.15 K in mixed 3 He 4 He droplets 12 ).…”

mentioning

confidence: 99%

Excimers in the Lowest Rotational Quantum State in Liquid Helium

Mendoza-Luna

Shiltagh

Watkins

et al. 2016

J. Phys. Chem. Lett.

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Evidence for helium excimers (He * 2 ) in the lowest allowed rotational quantum state in liquid helium is presented. He * 2 was generated by a corona discharge in the gas and normal liquid phases. Fluorescence spectra recorded in the visible region between 3.8 and 5.0 K and 0.2 and 5.6 bar showed the rotationally resolvedtransition of He * 2 . Analysis of the pressure and temperature dependence of lineshifts and line intensities showed features of solvated He * 2 superimposed on its gas phase spectrum and, in the liquid phase only, pressure-induced rotational cooling. These findings suggest that He * 2 can be used to investigate bulk helium in different phases at the nanoscale.

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Rotationally Resolved Spectroscopy of SF6in Liquid Helium Clusters: A Molecular Probe of Cluster Temperature

Cited by 573 publications

References 26 publications

Structure and energetics of mixed4He-3He drops

Structure and energetics of mixed4He-3He drops

Electron‐Driven Self‐Assembly of Salt Nanocrystals in Liquid Helium

Excimers in the Lowest Rotational Quantum State in Liquid Helium

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