Electron impact ionization of CCl4 and SF6 embedded in superfluid helium droplets

Schöbel, Harald; Dampc, Marcin; Silva, F. Ferreira da; Mauracher, Andreas; Zappa, Fábio; Denifl, Stephan; Märk, T.D.; Scheier, P.

doi:10.1016/j.ijms.2008.07.009

Cited by 16 publications

(17 citation statements)

References 36 publications

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“…[60] They are congested due to the presence of more than one isotope in natural sulfur and chlorine. Data analysis is challenging as illustrated further below in our discussion of anion spectra.…”

Section: Resultsmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

“…[60] In the present work we apply mass spectrometry to determine the size of the first solvation shell for several ions em- …”

Section: Introductionmentioning

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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“…Previous studies have shown that ion cooling can be quite slow in helium nanodroplets, [18][19][20][21][22] and so it is plausible that the hot Na n + clusters will initiate a fragmentation cascade which is punctuated by the added stability of certain cluster structures. This accounts for both the odd-even intensity alternations and clear magic number features reflected in Figure 2.…”

Section: A Magic Numbersmentioning

confidence: 99%

The submersion of sodium clusters in helium nanodroplets: Identification of the surface → interior transition

Lan

Bartl

Leidlmair

et al. 2011

The Journal of Chemical Physics

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The submersion of sodium clusters beyond a critical size in helium nanodroplets, which has recently been predicted on theoretical grounds, is demonstrated for the first time. Confirmation of a clear transition from a surface location, which occurs for alkali atoms and small clusters, to full immersion for larger clusters, is provided by identifying the threshold electron energy required to initiate Na n cluster ionization. On the basis of these measurements, a lower limit for the cluster size required for submersion, n ≥ 21, has been determined. This finding is consistent with the recent theoretical prediction.

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“…In this paper we continue our recently instigated series of studies of the interaction of electrons with molecules and clusters in helium nanodroplets. [10][11][12][13][14][15][16] Here the ion chemistry takes place in a cold environment dictated by the extremely low temperature (0.38 K) of the surrounding liquid helium. In the present study we report on the findings of both electron attachment and electron ionization measurements on helium nanodroplets doped with acetic acid molecules.…”

Section: Introductionmentioning

confidence: 99%

Electron attachment and electron ionization of acetic acid clusters embedded in helium nanodroplets

Silva

Jaksch

Martins

et al. 2009

Phys. Chem. Chem. Phys.

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The effect of incident electrons on acetic acid clusters is explored for the first time. The acetic acid clusters are formed inside liquid helium nanodroplets and both cationic and anionic products ejected into the gas phase are detected by mass spectrometry. The cation chemistry (induced by electron ionization at 100 eV) is dominated by production of protonated acetic acid (Ac) clusters, Ac n H + , although some fragmentation is also observed. In the case of anion production (at 2.8 eV electron energy) there is a clear distinction between the monomer and the clusters. For the monomer the dominant product is the dehydrogenated species, [Ac-H] À , whereas for the clusters both the parent anion, Ac n À , and the dehydrogenated species, [Ac n -H] À , have similar abundances. A particularly intriguing contrast between the monomer and cluster anions is that helium atoms are seen attached to the latter whereas no evidence of helium atom attachment is found for the monomer. This surprising observation is attributed to the formation of acyclic (head-to-tail) acetic acid clusters in helium nanodroplets, which have more favourable electronic properties for binding helium atoms. The acyclic clusters represent a local minimum on the potential energy surface and in the case of the dimer this is distinct from the cyclic isomer (the global minimum) identified in gas phase experiments.

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Electron impact ionization of CCl4 and SF6 embedded in superfluid helium droplets

Cited by 16 publications

References 36 publications

On the Size of Ions Solvated in Helium Clusters

On the Size of Ions Solvated in Helium Clusters

The submersion of sodium clusters in helium nanodroplets: Identification of the surface → interior transition

Electron attachment and electron ionization of acetic acid clusters embedded in helium nanodroplets

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