Solvation of Na<sup>+</sup>, K<sup>+</sup>, and Their Dimers in Helium

Lan, Lukas An der; Bartl, Peter; Leidlmair, Christian; Jochum, Roland; Denifl, Stephan; Echt, Olof; Scheier, P.

doi:10.1002/chem.201103432

Cited by 54 publications

(90 citation statements)

References 64 publications

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“…Anomalies in the abundance distributions allow us to estimate the change in the corresponding relative adsorption energies. A large decrease by about 40% occurs upon completion of the ordered 1 × 1 phase for He 32 , respectively. A possible explanation of these numbers is the completion of the first adsorption layer but it is not clear why the number of atoms should depend on the charge polarity for C 70 when there is no such dependence for C 60 .…”

Section: Resultsmentioning

confidence: 99%

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Adsorption of helium on isolated C₆₀and C₇₀anions

et al. 2015

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Adsorption of helium on free, negatively charged fullerenes is studied in this work. Helium nanodroplets have been doped with fullerenes and ionised by electron attachment. For suitable experimental conditions, C − 60 and C − 70 anions are found to be complexed with a large number of helium atoms. Prominent anomalies in the ion abundances indicate the high stability of the commensurate 1 × 1 phase in which all hollow adsorption sites are occupied by one atom each. The adsorption energy for an additional helium atom is about 40% less than for atoms in the commensurate layer, similar to our previous findings for fullerene cations and in agreement with theoretical dissociation energies. Similarly, an anomaly in the adsorption energy occurs when 60 helium atoms are attached to C − 60 or 65 to C − 70 . For C 60 , the anomaly coincides with the one observed for cationic complexes but for C 70 it does not. Implications of these features are discussed in light of several theoretical studies of neutral and positively charged helium-fullerene complexes.

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Section: Resultsmentioning

confidence: 99%

“…This information is presented in Figure 3(a) and 3(b) which show relative dissociation energies of He n C 60 anions and cations, respectively. As explained below, these quantities combine experimental ion abundances with theoretically determined dissociation (or evaporation or adsorption) energies D n [11,32]. D n is defined as Figure 3.…”

Section: Resultsmentioning

confidence: 99%

Adsorption of helium on isolated C₆₀and C₇₀anions

et al. 2015

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“…[47][48][49] These ions are often referred to as snowballs because electrostrictive forces solidify the helium matrix that surrounds the ion. One may wonder if He m A n 2+ (A = sodium, potassium, cesium) dications can be detected for n 4 1.…”

Section: +mentioning

confidence: 99%

Fission of multiply charged alkali clusters in helium droplets – approaching the Rayleigh limit

Renzler

Harnisch

Daxner

et al. 2016

Phys. Chem. Chem. Phys.

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Electron ionization of helium droplets doped with sodium, potassium or cesium results in doubly and, for cesium, triply charged cluster ions. The smallest observable doubly charged clusters are Na9(2+), K11(2+), and Cs9(2+); they are a factor two to three smaller than reported previously. The size of sodium and potassium dications approaches the Rayleigh limit nRay for which the fission barrier is calculated to vanish, i.e. their fissilities are close to 1. Cesium dications are even smaller than nRay, implying that their fissilities have been significantly overestimated. Triply charged cesium clusters as small as Cs19(3+) are observed; they are a factor 2.6 smaller than previously reported. Mechanisms that may be responsible for enhanced formation of clusters with high fissilities are discussed.

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“…A special situation arises if C n is much less than the classical value, a situation probably encountered for alkali monomer and dimer ions solvated in helium, 77 and fullerene ions solvated in helium 10 or hydrogen. The computed energies for desorption of H 2 from H x C 60 + (x = 2, 3, 4, 5) amount to 50-70 meV (Table I); the corresponding vibrational temperature of the complexes may thus be estimated from the evaporative model to be 30-40 K. 78,79 At this temperature C 60 + will be in its vibrational ground state, and one obtains the simple relation…”

Section: Abundance Anomalies and Adsorption Of H 2 On Graphitic Sumentioning

confidence: 99%

Adsorption of hydrogen on neutral and charged fullerene: Experiment and theory

Kaiser

Leidlmair

Bartl

et al. 2013

The Journal of Chemical Physics

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A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu The Journal of Chemical Physics 132, 154104 (2010) Helium droplets are doped with fullerenes (either C 60 or C 70 ) and hydrogen (H 2 or D 2 ) and investigated by high-resolution mass spectrometry. In addition to pure helium and hydrogen cluster ions, hydrogen-fullerene complexes are observed upon electron ionization. The composition of the main ion series is (H 2 ) n HC m + where m = 60 or 70. Another series of even-numbered ions, (H 2 ) n C m + , is slightly weaker in stark contrast to pure hydrogen cluster ions for which the even-numbered series (H 2 ) n + is barely detectable. The ion series (H 2 ) n HC m + and (H 2 ) n C m + exhibit abrupt drops in ion abundance at n = 32 for C 60 and 37 for C 70 , indicating formation of an energetically favorable commensurate phase, with each face of the fullerene ion being covered by one adsorbate molecule. However, the first solvation layer is not complete until a total of 49 H 2 are adsorbed on C 60 + ; the corresponding value for C 70 + is 51. Surprisingly, these values do not exhibit a hydrogen-deuterium isotope effect even though the isotope effect for H 2 /D 2 adsorbates on graphite exceeds 6%. We also observe doubly charged fullerene-deuterium clusters; they, too, exhibit abrupt drops in ion abundance at n = 32 and 37 for C 60 and C 70 , respectively. The findings imply that the charge is localized on the fullerene, stabilizing the system against charge separation. Density functional calculations for C 60 -hydrogen complexes with up to five hydrogen atoms provide insight into the experimental findings and the structure of the ions. The binding energy of physisorbed H 2 is 57 meV for H 2 C 60 + and (H 2 ) 2 C 60 + , and slightly above 70 meV for H 2 HC 60 + and (H 2 ) 2 HC 60 + . The lone hydrogen in the odd-numbered complexes is covalently bound atop a carbon atom but a large barrier of 1.69 eV impedes chemisorption of the H 2 molecules. Calculations for neutral and doubly charged complexes are presented as well.

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Solvation of Na⁺, K⁺, and Their Dimers in Helium

Cited by 54 publications

References 64 publications

Adsorption of helium on isolated C₆₀and C₇₀anions

Adsorption of helium on isolated C₆₀and C₇₀anions

Fission of multiply charged alkali clusters in helium droplets – approaching the Rayleigh limit

Adsorption of hydrogen on neutral and charged fullerene: Experiment and theory

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Solvation of Na+, K+, and Their Dimers in Helium

Cited by 54 publications

References 64 publications

Adsorption of helium on isolated C60and C70anions

Adsorption of helium on isolated C60and C70anions

Fission of multiply charged alkali clusters in helium droplets – approaching the Rayleigh limit

Adsorption of hydrogen on neutral and charged fullerene: Experiment and theory

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Solvation of Na⁺, K⁺, and Their Dimers in Helium

Adsorption of helium on isolated C₆₀and C₇₀anions

Adsorption of helium on isolated C₆₀and C₇₀anions