Adducts formed between small gold cluster cations and helium atoms are reported for the first time. These binary ions, Aun+Hem, were produced by electron ionization of helium nanodroplets doped with neutral gold clusters and were detected using mass spectrometry. For a given value of n, the distribution of ions as a function of the number of added helium atoms, m, has been recorded. Peaks with anomalously high intensities, corresponding to so-called magic number ions, are identified and interpreted in terms of the geometric structures of the underlying Aun+ ions. These features can be accounted for by planar structures for Aun+ ions with n ≤ 7, with the addition of helium having no significant effect on the structures of the underlying gold cluster ions. According to ion mobility studies and some theoretical predictions, a 3-D structure is expected for Au8+. However, the findings for Au8+ in this work are more consistent with a planar structure.

Double magic: 12 adamantane “nanodiamonds” surround, in an icosahedric arrangement, 21 water molecules that form a pentagon dodecahedral structure.

Copper nanoparticles are promising, low-cost candidates for the catalytic splitting of water and production of hydrogen gas. The present gas-phase study, based on the synthesis of copper-water complexes in ultracold helium nanodroplets followed by electron ionization, attempts to find evidence for dissociative water adsorption and H2 formation. Mass spectra show that H2O-Cu complexes containing dozens of copper and water molecules can be formed in the helium droplets. However, ions that would signal the production and escape of H2, such as (H2O)n−2(OH)2Cum + or the isobaric (H2O)n−1OCum + , could not be detected. We do observe an interesting anomaly though: While the abundance of stoichiometric (H2O)nCum + ions generally exceeds that of protonated or dehydrogenated ions, the trend is reversed for (H2O)OHCu2 + and (H2O)2OHCu2 + ; these ions are more abundant than (H2O)2Cu2 + and (H2O)3Cu2 + , respectively. Moreover, (H2O)2OHCu2 + is much more abundant than other ions in the (H2O)n−1OHCu2 + series. A byproduct of our experiment is the observation of enhanced stability of He6Cu + , He12Cu + , He24Cu + , and He2Cu2 + .

We have doped helium nanodroplets with C60 and either gold or copper. Positively or negatively charged (C60)mMn± ions (M = Au or Cu) containing up to ≈10 fullerenes and ≈20 metal atoms are formed by electron ionization. The abundance distributions extracted from high-resolution mass spectra reveal several local anomalies. The sizes of the four most stable (C60)mAun± ions identified in previous calculations for small values of m and n (m ≤ 2 and n ≤ 2, or m = 1 and n = 3) agree with local maxima in the abundance distributions. Our data suggest the existence of several other relatively stable ions including (C60)2Au3± and (C60)3Au4–. Another feature, namely the absence of bare (C60)2±, confirms the prediction that (C60)2M± dissociates by loss of C60± rather than loss of M. The experimental data also reveal the preference for loss of (charged or neutral) C60 over loss of a metal atom from some larger species such as (C60)3M3+. In contrast to these similarities between Au and Cu, the abundance distributions of (C60)3Aun– and (C60)3Cun– are markedly different. In this discussion, we emphasize the similarities and differences between anions and cations, and between gold and copper. Also noteworthy is the observation of dianions (C60)mAun2– for m = 2, 4, and 6.

Electron-induced chemistry in imidazole (IMI) clusters embedded in helium nanodroplets (with an average size of 2×10 5 He atoms) has been investigated with highresoluton time-of-flight mass spectrometry. The formation of both, negative and positive, ions was monitored as a function of the cluster size n. In both ion spectra a clear series of peaks with IMI cluster sizes up to at least 25 are observed. While the anions are formed by collisions of IMI n with He *− , the cations are formed through ionization of IMI n by He + as the measured onset for the cation formation is observed at 24.6 eV (ionization energy of He). The most abundant series of anions are dehydrogenated anions IMI n-1 (IMI−H) − , while other anion series are IMI clusters involving CN and C 2 H 4 moieties. The formation of cations is dominated by the protonated cluster ions IMI n H + , while the intensity of parent cluster cations IMI n + is also observed preferentially for the small cluster size n.The observation of series of cluster cations [IMI n CH 3 ] + suggests either CH 3 + cation to be solvated by n neutral IMI molecules, or the electron-induced chemistry has led to the formation of protonated methyl-imidazole solvated by (n−1) neutral IMI molecules.Keywords: Imidazole, imidazole clusters, helium nanodroplets, electron attachment, electron-induced processesRunning Title: Electron-induced chemistry in imidazole doped HND.