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We studied the electron spin resonance (ESR) spectra of nitrogen atoms stabilized in nitrogen-neon nanoclusters immersed in superfluid 4He. The nanoclusters were formed during the condensation of the products of the discharge in N2–Ne–He gas mixtures into bulk superfluid 4He at temperature 1.5 K. We studied nanoclusters formed by injection of gas mixtures with different ratios of heavy impurities in the helium N2/(Ne + N2 ) ranging from 2% to 90%. Analysis of the ESR spectra of nitrogen atoms stabilized in nitrogen-neon nanoclusters provides important information about the environment of the stabilized atoms and a shell structure of the nanoclusters was revealed. For all samples studied, preferential stabilization of N atoms on the surfaces of the nanoclusters was observed. Annealing of the collection of the nanoclusters in the temperature range 1.1–10 K resulted in substantial changes in the structure of the nanoclusters.
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Structure of Molecular Nitrogen Nanoclusters Containing Stabilized Nitrogen Atoms
Impurity-helium condensates (IHCs) formed by injecting the discharge products of gaseous mixtures of helium atoms and nitrogen molecules into bulk superfluid 4He at temperature 1.5 K, were studied by X-band electron spin resonance. IHCs consists of collections of N2 nanoclusters which form aerogel-like structure inside bulk HeII. It was found that N2 nanoclusters have a two shell structure, an outer shell which contains high concentration of stabilized N atoms and an interior shell with lower concentrations of N atoms. In this paper, we have studied the dependence of the shell structure of the N2 nanoclusters which compose the IHCs by varying the ratio of nitrogen to helium in the prepared gas mixture from 0.06 to 1%. The highest local concentration of N atoms in nanoclusters (1.2 ⋅ 1021 cm−3 ) was observed in the sample prepared from the gas mixture containing the lowest nitrogen admixture (0.06%). Additionally, the evolution of nanocluster structure was studied as the samples were drained of liquid helium (T ≤ 3.5 K) and warmed beyond the point of explosive recombination (3.5 K ≤ T ≤ 6.5 K).
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- Award ID(s):
- 2104756
- PAR ID:
- 10588108
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Journal of Low Temperature Physics
- ISSN:
- 0022-2291
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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