Structure of Molecular Nitrogen Nanoclusters Containing Stabilized Nitrogen Atoms

Abstract Impurity-helium condensates (IHCs) formed by injecting the discharge products of gaseous mixtures of helium atoms and nitrogen molecules into bulk superfluid \(⁴\) He at temperature 1.5 K, were studied by X-band electron spin resonance (ESR). IHCs consists of collections of N \(_2\) 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 \(·\) 10 \(²¹\) 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).