Düsseldorf 2007 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 4: Atomic Clusters II
A 4.3: Vortrag
Montag, 19. März 2007, 14:45–15:00, 6G
Magic Numbers and Superfluid Sizes in Small Para-Hydrogen Clusters — •Peter Toennies1, Saad Khairallah2, Mikhail Sevryuk1, and David Ceperley2 — 1Max Planck Institut für Dynamik und Selbstorganisation, D-37073 Göttingen — 2Dept. Physics, University of Illinois at Urbana-Champaign, IL 61801 USA
The Path Integral Monte Carlo method is used to study the low temperature structures and superfluidity of para-hydrogen clusters with up to 40 molecules. Clusters with sizes N<26 and T ≤ 1.5 K have nearly 100% superfluid fractions. In larger clusters superfluidity is quenched at the icosahedral-derived magic numbers N=26, 29, 32, and 37 found in "classical" rare gas ion clusters, while below 1 K superfluidity is recovered for the pairs (27,28), (30,31), and (35,36) with loosely attached outer molecules. In all the clusters superfluidity is largely localized in the surface thereby explaining the apparent "supersolid" behavior discussed in the past.