Observation of Multiple Ordered Solvation Shells in Doped Helium Droplets: The Case of He_NCa²⁺

Abstract

In this Letter, we report the experimental detection of likely the largest ordered structure of helium atoms surrounding a monatomic impurity observed to date using a recently developed technique. The mass spectrometry investigation of He N Ca 2+ clusters, formed in multiply charged helium nanodroplets, reveals magic numbers at N = 12, 32, 44, and 74. Classical optimization and path integral Monte Carlo calculations suggest the existence of up to four shells surrounding the calcium dication which are closed with well-ordered Mozartkugellike structures: He 12 Ca 2+ with an icosahedron, the second at He 32 Ca 2+ with a dodecahedron, the third at He 44 Ca 2+ with a larger icosahedron, and finally for He 74 Ca 2+ , we find that the outermost He atoms form an icosidodecahedron which contains the other inner shells. We analyze the reasons for the formation of such ordered shells in order to guide the selection of possible candidates to exhibit a similar behavior.

Mixed Cluster Ions of Magnesium and C60

“…However, He k X 2+ ions are unambiguously formed in HNDs. In the case of Ca, multiple ordered solvation shells were observed experimentally via intensity drops of the ion yield of He k Ca 2+ at k = 12, 32, 44, and 74 . In the mass spectrum shown in Figure , He k Mg 2+ ions can be identified via the 25 Mg isotopes up to k = 12; however, these ions are formed with low abundance.…”

“…In the case of Ca, multiple ordered solvation shells were observed experimentally via intensity drops of the ion yield of He k Ca 2+ at k = 12, 32, 44, and 74. 77 In the mass spectrum shown in Figure 1, He k Mg 2+ ions can be identified via the 25 Mg isotopes up to k = 12; however, these ions are formed with low abundance. It is interesting to note that, so far, the formation of a molecular dication via ionization of neutral-doped HNDs has never been observed.…”

Size limits and fission channels of doubly charged noble gas clusters

“…20 Doubly charged heteronuclear clusters, and even dimers such as NeXe 2+ and HeCa 2+ , may be thermodynamically stable with respect to charge separation because the two charges reside on the same atom; charge transfer from the dication to the neutral ligand would be endothermic. 21–26 We will also ignore multiply charged cluster anions where electron detachment represents an additional relaxation channel. 27–29…”

Ion solvation in atomic baths: From snowballs to polarons

“…This interaction is much stronger than typical van der Waals interactions ∝R −6 . In this scenario, a single ion could bind to many atoms of the neutral bath, and depending on the nature of the bath, coordination complexes, 14,15 snowballs, [16][17][18] or polarons 9,10 appear.…”