title: Compact non-rock-salt structures in sodium fluoride cluster ions at specific sizes revealed by ion mobility mass spectrometry.
abstract: Structures of small sodium fluoride cluster cations, Na(n)F(n-1)(+), have been determined for n = 5-23 by ion mobility mass spectrometry. In the mass spectrum of Na(n)F(n-1)(+) cluster ions measured after collisions in the ion-drift cell, cuboid ions with near-regular hexahedron such as n = 14 (3 × 3 × 3), 23 (3 × 3 × 5), 38 (3 × 5 × 5), 63 (5 × 5 × 5), and 88 (5 × 5 × 7) were predominantly observed as magic numbers. By comparison of the collision cross sections obtained from the ion mobility measurements with theoretical ones, we have experimentally shown that the ions of n = 7 and 10 have stable non-rock-salt type structures in which one sodium atom is encapsulated into the sodium fluoride cuboid lattice. The collision cross sections of n = 12 and 13 are almost equal to that of the n = 14 cuboid. A similar feature was also observed in collision cross sections of n = 21 and 22, which are equal to that of the n = 23 cuboid. These features indicate that the cluster ions of n = 12, 13, 21, and 22 have near-cuboid structures with some surface defects.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University , 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
authors.forename: Keijiro
authors.initials: K
authors.lastname: Ohshimo
authors.forename: Tohru
authors.initials: T
authors.lastname: Takahashi
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Moriyama
authors.forename: Fuminori
authors.initials: F
authors.lastname: Misaizu