Percolation in aggregates of nanoclusters immersed in superfluid helium
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Impurity-helium condensates created by injection of hydrogen (deuterium) atoms and molecules as well as rare gas (RG) atoms (Ne and Kr) into superfluid He4 have been studied via electron spin resonance (ESR) techniques. Measurements of the ground-state spectroscopic parameters of hydrogen and deuterium atoms show that the nanoclusters have a shell structure. H and D atoms reside in solid molecular layers of H2 and D2, respectively. These layers form on the surfaces of RG (Ne or Kr) nanoclusters. By monitoring the recombination of H atoms in the collection of hydrogen-neon nanoclusters, we show that nanoclusters form a gel-like porous structure which enables the H atoms to be transported through the structure via percolation. Observation of percolation in the collection of nanoclusters containing stabilized hydrogen atoms may open possibilities for a search for macroscopic collective quantum phenomena at ultralow temperatures accessible by a dilution refrigerator. 2014 American Physical Society.
author list (cited authors)
Mao, S., Meraki, A., Boltnev, R. E., Khmelenko, V. V., & Lee, D. M.