ESR studies of nitrogen atoms stabilized in aggregates of krypton–nitrogen nanoclusters immersed in superfluid helium
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Impurity-helium condensates (IHCs) containing nitrogen and krypton atoms immersed in superfluid 4He have been studied via CW electron spin resonance (ESR). The IHCs are gel-like aggregates of nanoclusters composed of impurity species. It was found that the addition of krypton atoms to the nitrogen-helium gas mixture used for preparation of IHCs increases the efficiency of stabilization of nitrogen atoms. We have achieved high average (5 · 1019 cm-3) and local (2 · 1021 cm-3) concentrations of nitrogen atoms in krypton-nitrogen-helium condensates. The analysis of ESR lines shows that in krypton-nitrogen nanoclusters three different sites exist for stabilization of nitrogen atoms. Nitrogen atoms are stabilized in the krypton core of nanoclusters, in the nitrogen molecular layer that covers the Kr core, and on the surface of the nanoclusters. High concentrations of nitrogen atoms achieved in IHCs provide an important step in the search for magnetic ordering effects at low temperatures. © 2012 American Institute of Physics.
author list (cited authors)
Mao, S., Boltnev, R. E., Khmelenko, V. V., & Lee, D. M.