Atomic Gold Ions Clustered with Noble Gases: Helium, Neon, Argon, Krypton, and Xenon


High-resolution mass spectra of helium droplets doped with gold and ionized by electrons reveal HenAu+ cluster ions. Additional doping with heavy noble gases results in NenAu+, ArnAu+, KrnAu+, and XenAu+ cluster ions. The high stability predicted for covalently bonded Ar2Au+, Kr2Au+, and Xe2Au+ is reflected in their relatively high abundance. Surprisingly, the abundance of Ne2Au+, which is predicted to have zero covalent bonding character and no enhanced stability, features a local maximum, too. The predicted size and structure of complete solvation shells surrounding ions with essentially nondirectional bonding depends primarily on the ratio σ* of the ion–ligand versus the ligand–ligand distance. For Au+ solvated in helium and neon, the ratio σ* is slightly below 1, favoring icosahedral packing in agreement with a maximum observed in the corresponding abundance distributions at n = 12. HenAu+ appears to adopt two additional solvation shells of Ih symmetry, containing 20 and 12 atoms, respectively. For ArnAu+, with σ* ≈ 0.67, one would expect a solvation shell of octahedral symmetry, in agreement with an enhanced ion abundance at n = 6. Another anomaly in the ion abundance at Ar9Au+ matches a local maximum in its computed dissociation energy.



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The Journal of Physical Chemistry A


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