Condensation of an atomic beam on a cold (⪷2 K) surface

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.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On charged impurity structures in liquid helium

Pelmenev

Krushinskaya

Bykhalo

et al. 2016

“…The experimental technique of IHC sample preparation was first developed in 1974 [9]. A cryogenic portion of the experimental setup is shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

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

Krushinskaya

Boltnev

Bykhalo

et al. 2015

New experimental results on detection of optical spectra and ion currents during destruction of impurity-helium condensates (IHCs) have been obtained. It is shown that emission during IHC sample destruction is accompanied by current pulses, pressure peaks and temperature changes. The molecular bands of excimer molecules XeO* are assigned to molecules stabilized in films of molecular nitrogen covering the heavier cores of impurity clusters which form impurity-helium condensates.

“…The experimental approach for stabilization of atoms by injection of impurity-helium (Im-He) gas jet into superfluid helium (He II) was first developed by Gordon, Mezhov-Deglin, and Pugachev in 1974 [1]. The advantages of this approach are related to efficient pre-cooling of the gas jet prior to its immersion into He II, high degree of dispersion of impurity particles, and efficient thermal dissipation by He II.…”

Section: Introductionmentioning

confidence: 99%

“…Since its discovery, the original approach has been subject to active development, and currently semitransparent gel-like substances with He/Im ratios of 12-60 and thermal stability up to 6-8 K are routinely grown. Although their interior is filled with liquid He, these macroscopic condensates are historically called impurity-helium solids (IHS) [1][2][3][4][5][6][7][8][9]. An interesting extension to the cited series of investigations is provided by a recent work by Mezhov-Deglin and Kokotin on the helium-water condensate [10].…”

Section: Introductionmentioning

confidence: 99%

On the formation mechanism of impurity–helium solids: evidence for extensive clustering

Попов

Eloranta

Ahokas

et al. 2003

Optical emission studies on a discharged nitrogen-helium gas jet injected into superfluid helium near 1.5 K are described. The analysis of atomic (a-group) and molecular Vegard-Kaplan transitions clearly indicates that the emitting species are embedded in the nitrogen clusters. The formation of the clusters is most efficient in the crater formed on the liquid surface. The model calculations based on the classical bubble model and density functional theory suggest that under the experimental conditions only clusters consisting of more than 1000 molecules have a kinetic energy sufficient for the stable cavity formation inside liquid helium. The results obtained suggest that the formation of impurity-helium solids is a consequence of extensive clustering in the gas jet.