Kinetic methods for quantifying magic

Klots, Cornelius E.

doi:10.1007/bf01438406

Cited by 161 publications

(87 citation statements)

References 19 publications

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“…[44] www.chemeurj.org however, an abrupt drop in DE(n) at n s will be reflected in a similarly abrupt drop in the ion yield at n s . [66] The size dependence of evaporation energies may exhibit a variety of features, such as local singular maxima, minima, and ledges. Closure of a geometric shell at size n s is usually preceded by a more or less constant evaporation energy, followed by a substantially lower evaporation energy for cluster size n s + 1.…”

Section: Discussionmentioning

confidence: 99%

On the Size of Ions Solvated in Helium Clusters

Silva

Waldburger

Jaksch

et al. 2009

Chemistry A European J

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Helium nanodroplets are doped with SF(6), C(4)F(8), CCl(4), C(6)H(5)Br, CH(3)I, and I(2). Upon interaction with free electrons a variety of positively and negatively charged cluster ions X(+/-)He(n) are observed where X(+/-) = F(+/-), Cl(+/-), Br(+/-), I(+), I(2) (+), or CH(3)I(+). The yield of these ions versus cluster size n drops at characteristic sizes n(s) that range from n(s) = 10.2+/-0.6 for F(+) to n(s) = 22.2+/-0.2 for Br(-). n(s) values for halide anions are about 70% larger than for the corresponding cations. The steps in the ion yield suggest closure of the first solvation shell. We propose a simple classical model to estimate ionic radii from n(s). Assuming the helium density in the first solvation shell equals the helium bulk density one finds that radii of halide anions in helium are nearly twice as large as in alkali halide crystals, indicating the formation of an anion bubble due to the repulsive forces that derive from the exchange interaction. In spite of the simplicity of our model, anion radii derived from it agree within approximately 10% with values derived from the mobility of halide anions in superfluid bulk helium, and with values computed by quantum Monte Carlo methods for X(-)He(n) cluster anions.

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Section: Discussionmentioning

confidence: 99%

On the Size of Ions Solvated in Helium Clusters

Silva

Waldburger

Jaksch

et al. 2009

Chemistry A European J

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“…The relation between the size dependence of D n and A n has been explored by several authors, 71 based on the model of the evaporative ensemble. 72 Key ingredients of this model are that the initial cluster distribution is broad, dissociation is a statistical process, and each cluster ion that is observed has undergone at least one evaporation.…”

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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“…Here T is the temperature before emission, and the last term in equation (A.3) is the finite-heat-bath correction [45]. The most important parameter in equation (A.2) is the electron affinity, which is known fairly well for the fullerenes [15].…”

Section: Appendix Amentioning

confidence: 99%

Radiative cooling of fullerene anions in a storage ring

Andersen

Gottrup

Hansen

et al. 2001

The European Physical Journal D

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Abstract. Thermionic emission from hot fullerene anions, C − N , has been measured in an electrostatic storage ring for even N values from 36 to 96. The decay is quenched by radiative cooling and hence the observations give information on the intensity of thermal radiation from fullerenes. The experiments are analysed by comparison with a simulation which includes the quantisation of photon energy and the statistics of emission. Experiments with heating of the molecules with a laser beam confirm the interpretation of the observations in terms of radiative cooling and give an independent estimate of the cooling rate for C − 60 . The measured cooling rates agree in general within a factor of two with the prediction from a classical dielectric model of a thermal radiation intensity of ∼ 300 eV/s for C60 at 1 400 K, scaling approximately with the 6th power of the temperature and with the number of atoms in the molecule. PACS

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Kinetic methods for quantifying magic

Cited by 161 publications

References 19 publications

On the Size of Ions Solvated in Helium Clusters

On the Size of Ions Solvated in Helium Clusters

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

Radiative cooling of fullerene anions in a storage ring

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