On charged impurity structures in liquid helium

Abstract

The thermoluminescence spectra of impurity-helium condensates (IHC) submerged in superfluid helium have been observed for the first time. Thermoluminescence of impurity-helium condensates submerged in superfluid helium is explained by neutralization reactions occurring in impurity nanoclusters. Optical spectra of excited products of neutralization reactions between nitrogen cations and thermoactivated electrons were rather different from the spectra observed at higher temperatures, when the luminescence due to nitrogen atom recombination dominates. New results on current detection during the IHC destruction are presented. Two different mechanisms of nanocluster charging are proposed to describe the phenomena observed during preparation and warmup of IHC samples in bulk superfluid helium, and destruction of IHC samples out of liquid helium.

Optical spectroscopy and current detection during warm-up and destruction of impurity–helium condensates

“…We suggest that electrons were carriers of negative charge, while the origin of positive carriers is still unclear. The ions can be formed (due to Penning ionization processes) and trapped into impurity nanoclusters growing in a gas jet [24]. Another possibility for ion formation is irradiation of impurity nanoclusters stabilized in bulk He II by VUV emission from the discharge area.…”

Quantum vortices and thermally induced luminescence of nitrogen nanoclusters immersed in liquid helium

“…[26,43] Recently, another mechanism of N atom themoluminescence in HeII was discussed. [41] The authors of Ref. [41] suggested that electrons and nitrogen ions would be captured separately in molecular nitrogen nanoclusters during the process of injection of discharge products in HeII at T=1.5 K. They proposed that increasing the temperature of the ensembles of nanoclusters immersed in HeII could initiate the release of electrons from the traps.…”

“…[41] The authors of Ref. [41] suggested that electrons and nitrogen ions would be captured separately in molecular nitrogen nanoclusters during the process of injection of discharge products in HeII at T=1.5 K. They proposed that increasing the temperature of the ensembles of nanoclusters immersed in HeII could initiate the release of electrons from the traps. After that, the electrons could tunnel through the nanoclusters resulting in electronion recombination.…”

“…After that, the electrons could tunnel through the nanoclusters resulting in electronion recombination. [41] The nitrogen molecules so excited could emit light or transfer energy to stabilized nitrogen atoms thereby initiating α-group emission. In contrast, in our experiments we did not observe any ESR signal from electrons or ions in the samples immersed in HeII.…”

“…The thermoluminescence of nitrogen atoms in samples formed by injecting products of a gas discharge into superfluid helium was studied earlier. [40,41] The thermoluminescence initially was assigned to the emission of N( 2 D)-N 2 van der Waals complexes in solid helium. It was suggested that solid helium could be formed by injection of single heavy atoms and molecules into superfluid helium.…”