Formation of helium cluster ions HHe x + (x?14) and H3He x + (x?13) in a very low temperature drift tube

Kojima, Takao; Kobayashi, Nobuo; Kaneko, Yozaburo

doi:10.1007/bf01436742

Cited by 31 publications

(42 citation statements)

References 12 publications

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“…This already has been observed in the above-mentioned drift tube experiment [45]. Note that HeH + is a strongly bond molecule (D 0 = 1.844 eV [48]).…”

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confidence: 61%

“…A few years later, using polarised Gaussian orbitals, it has been confirmed that it is stable with a binding energy of about 100 cm −1 and it was predicted that this complex ion should be detectable below 140 K [60]. As already mentioned above, stable He n -H + x complexes have been found, first in a 4.4 K drift tube [45] and recently using He droplets [46]. But there are no spectroscopic studies at all and no state of the art calculations.…”

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confidence: 84%

“…The required low temperatures and high number densities of He have been achieved already in a selected ion drift tube, which was operated at 4.4 K and gas densities between 2.2 and 11 × 10 16 cm −3 [45]. Information on their stability and structure has been derived from the drift field dependence of the cluster size distributions (magic numbers).…”

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confidence: 99%

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Controlled synthesis and analysis of He–H⁺₃in a 3.7 K ion trap

et al. 2015

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Complexes of the triatomic hydrogen ion with helium were synthesised in a low-temperature 22-pole rf ion trap at He number densities of up to 10 16 cm −3 . Absolute ternary rate coefficients for sequentially attaching He atoms have been determined from the growth of complexes with increasing storage time. The number of helium-tagged ions is significantly reduced when increasing the nominal temperature from 4 to 25 K. Competition between attachment and dissociation via collisions leads to stationary He n -H + 3 (n up to 9) distributions. State-specific excitation of the trapped H + 3 ions via IR transitions significantly reduces the formation of complexes. Tuning the laser to v 2 = 1 transitions in the range of 2726 cm −1 leads to LIICG lines, i.e., to spectra caused by laser-induced inhibition of complex growth. In addition, almost 100 lines have been found between 2700 and 2765 cm −1 , which are attributed to laser-induced dissociation of the in situ formed He-H + 3 complex ions. These lines are not yet assigned; however, their absorption strength, statistics and predissociation lifetimes provide interesting information on both the stable complexes as well as on scattering resonances in low-energy H + 3 + He collisions. New calculations of the potential energy surface will help to analyse the dissociation spectrum. There are some indications that para-H + 3 is enriched under the conditions of the present experiment. IntroductionStudies of reactions between ions and neutrals under conditions relevant for astrochemistry are important for understanding different processes in the interstellar medium (ISM). Reactions involving helium and hydrogen significantly influence the overall evolution of our universe including the early universe chemistry and especially the 'Dark Age'. For modelling such environments, one needs reliable rate coefficients. A detailed discussion of primordial chemistry can be found in [1] and references therein. According to [2], helium became neutral at a red shift of z ∼ 2500. At those times, the density was already very low and the only way to form molecules was via radiative association. Because hydrogen was still ionised, models predict that the first molecule formed in space was HeH + . The coexistence of He and He + also lead to the formation of some He + 2 . Molecules were needed as coolants during the formation of the first galaxies. Also after these early times, helium and hydrogen play an important role. In all models of interstellar ion chemistry, the first steps are ionisation of He and H 2 by cosmic rays.

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“…This already has been observed in the above-mentioned drift tube experiment [45]. Note that HeH + is a strongly bond molecule (D 0 = 1.844 eV [48]).…”

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confidence: 61%

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confidence: 84%

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Controlled synthesis and analysis of He–H⁺₃in a 3.7 K ion trap

et al. 2015

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“…[ [57][58][59] In recent work from our laboratory, CCl 4 and SF 6 molecules were embedded in helium nanodroplets; extended cluster ion series F + He n and Cl + He were formed by electron impact ionization. [60] In the present work we apply mass spectrometry to determine the size of the first solvation shell for several ions em- …”

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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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“…However, we are aware of only two experimental reports that involve more than two helium atoms. Kojima et al25 observed He n H + ( n ≤14) by injecting H 2 + into a drift tube filled with helium at 4.4 K. Injection of H 3 + gave rise to He n H + ( n ≤14) and He n H 3 + ( n ≤13). Only a very weak signal of He n H 2 + (3≤ n ≤10) could be observed.…”

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confidence: 99%

Cationic Complexes of Hydrogen with Helium

et al. 2012

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High-resolution mass spectra of helium nanodroplets doped with hydrogen or deuterium reveal that copious amounts of helium can be bound to H+, H2+, H3+, and larger hydrogen-cluster ions. All conceivable HenHx+ stoichiometries are identified if their mass is below the limit of ≍120 u set by the resolution of the spectrometer. Anomalies in the ion yields of HenHx+ for x=1, 2, or 3, and n≤30 reveal particularly stable cluster ions. Our results for HenH1+ are consistent with conclusions drawn from previous experimental and theoretical studies which were limited to smaller cluster ions. The HenH3+ series exhibits a pronounced anomaly at n=12 which was outside the reliable range of earlier experiments. Contrary to findings reported for other diatomic dopant molecules, the monomer ion (i.e. H2+) retains helium with much greater efficiency than hydrogen-cluster ions.

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Formation of helium cluster ions HHe x + (x?14) and H3He x + (x?13) in a very low temperature drift tube

Cited by 31 publications

References 12 publications

Controlled synthesis and analysis of He–H⁺₃in a 3.7 K ion trap

Controlled synthesis and analysis of He–H⁺₃in a 3.7 K ion trap

On the Size of Ions Solvated in Helium Clusters

Cationic Complexes of Hydrogen with Helium

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Formation of helium cluster ions HHe x + (x?14) and H3He x + (x?13) in a very low temperature drift tube

Cited by 31 publications

References 12 publications

Controlled synthesis and analysis of He–H+3in a 3.7 K ion trap

Controlled synthesis and analysis of He–H+3in a 3.7 K ion trap

On the Size of Ions Solvated in Helium Clusters

Cationic Complexes of Hydrogen with Helium

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Controlled synthesis and analysis of He–H⁺₃in a 3.7 K ion trap

Controlled synthesis and analysis of He–H⁺₃in a 3.7 K ion trap