The binding of alkali atoms to the surfaces of liquid helium and hydrogen

Ancilotto, Francesco; Cheng, E.; Cole, Milton W.; Toigo, Flavio

doi:10.1007/bf01338398

Cited by 110 publications

(108 citation statements)

References 15 publications

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“…16) (e.g., the ratio among the number of p-H 2 molecules and alkali metal atoms are 10/3 and 2/1, respectively). The cause for the large equilibrium density in the Na case, as compared to that of the Rb system, is related to the decrease of the core size of the AM-H 2 interaction (i.e., σ = 4.54Å in the Rb-H 2 case), which makes the surface available to p-H 2 molecules larger (we note that the depth of the potential wells in both Na-H 2 and Rb-H 2 interactions are very similar, i.e., 30 and 28 K, respectively 25 ). Regarding the stabilization of possible pseudocommensurate solid phases, we investigated the three crystal structures shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

“…24 The interactions between Na atoms and H 2 molecules are described with a Lennard-Jones potential of the form V LJ (r) = 4 [(σ/r) 12 − (σ/r) 6 ], with parameters taken from Ref. 25, namely σ = 4.14Å and = 30 K. The kinetic energy of the Na atoms has been also neglected since this is expected to be much smaller than the typical energy scale of p-H 2 molecules (i.e., 10-100 K).…”

Section: Methods and Simulation Detailsmentioning

confidence: 99%

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Possible superfluidity of molecular hydrogen in a two-dimensional crystal phase of sodium

Cazorla

Boronat²

2013

Phys. Rev. B

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We theoretically investigate the ground-state properties of a molecular para-hydrogen (p-H 2 ) film in which crystallization is energetically frustrated by embedding sodium (Na) atoms periodically distributed in a triangular lattice. In order to fully deal with the quantum nature of p-H 2 molecules, we employ the diffusion Monte Carlo method and realistic semiempirical pairwise potentials describing the interactions between H 2 -H 2 and Na-H 2 species. In particular, we calculate the energetic, structural, and superfluid properties of two-dimensional Na-H 2 systems within a narrow density interval around equilibrium at zero temperature. In contrast to previous computational studies considering other alkali metal species such as rubidium and potassium, we find that the p-H 2 ground state is a liquid with a significantly large superfluid fraction of ρ s /ρ = 0.29(2). The appearance of p-H 2 superfluid response is due to the fact that the interactions between Na atoms and H 2 molecules are less attractive than between H 2 molecules. This induces a considerable reduction of the hydrogen density which favors the stabilization of the liquid phase.

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Section: Resultsmentioning

confidence: 97%

Section: Methods and Simulation Detailsmentioning

confidence: 99%

Possible superfluidity of molecular hydrogen in a two-dimensional crystal phase of sodium

Cazorla

Boronat²

2013

Phys. Rev. B

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“…In case of surface doping with Ca, we assume a dimple depth of 7 Å [33]. According to Ancilotto et al [34], a single K atom is located in a dimple of depth 2.3 Å. Since such a shallow dimple cannot be implemented in a fcc lattice of discrete He atoms, we neglect the dimple for K dopants.…”

Section: Simulationsmentioning

confidence: 99%

Charging dynamics of dopants in helium nanoplasmas

Heidenreich

Grüner

Schomas

et al. 2017

Journal of Modern Optics

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We present a combined experimental and theoretical study of the charging dynamics of helium nanodroplets doped with atoms of different species and irradiated by intense near-infrared (NIR) laser pulses (≤10 15 Wcm -2). In particular, we elucidate the interplay of dopant ionization inducing the ignition of a helium nanoplasma, and the charging of the dopant atoms driven by the ionized helium host. Most efficient nanoplasma ignition and charging is found when doping helium droplets with xenon atoms, in which case high charge states both of helium (He 2+ ) and of xenon (Xe 21+ ) are detected. In contrast, only low charge states of helium and dopants are measured when doping with potassium and calcium atoms. Classical molecular dynamics simulations which include focal averaging generally reproduce the experimental results and provide detailed insights into the correlated charging dynamics of guest and host clusters.

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“…Due to the large mass of Rb and Cs atoms compared to that of He, we describe them as classical particles in the dynamics while their effect on the statics is incorporated as an external field acting upon the droplet [14,53]. Accordingly, the energy of the system is written as…”

Section: B Dft For Bosonsmentioning

confidence: 99%

Picosecond solvation dynamics of alkali cations in superfluidHe4nanodroplets

et al. 2014

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The dynamics following the photoionization of neutral Rb and Cs atoms residing in a dimple at the surface of a superfluid 4 He 1000 nanodroplet has been investigated within time-dependent density functional theory, complementing a previous study on Ba. The calculations reveal that structured high density helium solvation layers form around both the Rb + and Cs + cation on a picosecond time scale, forming so-called snowballs. In contrast to the Rb + ion, Cs + is not solvated by the 4 He 1000 droplet but rather desorbs from it as a Cs + He n snowball.This outcome is partially related to the large size of Cs + cation in relation to the helium droplet as is revealed by calculations performed using a planar helium surface. The large droplet deformations induced by the solvation of the Rb + cation is found to lead to efficient nucleation of quantized vortex loops or rings.

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The binding of alkali atoms to the surfaces of liquid helium and hydrogen

Cited by 110 publications

References 15 publications

Possible superfluidity of molecular hydrogen in a two-dimensional crystal phase of sodium

Possible superfluidity of molecular hydrogen in a two-dimensional crystal phase of sodium

Charging dynamics of dopants in helium nanoplasmas

Picosecond solvation dynamics of alkali cations in superfluidHe4nanodroplets

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