Roman Boltnev

Roman Boltnev
Joint Institute for High Temperatures

PhD

About

69
Publications
10,641
Reads
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727
Citations
Citations since 2016
27 Research Items
294 Citations
20162017201820192020202120220102030405060
20162017201820192020202120220102030405060
20162017201820192020202120220102030405060
20162017201820192020202120220102030405060
Additional affiliations
September 2014 - October 2014
LABORATOIRE DE GENIE ELECTRIQUE DE GRENOBLE
Position
  • PhD Student
Description
  • Researcher. Optical spectroscopy of cryogenic plasmas
June 2014 - present
Joint Institute for High Temperatures
Position
  • Senior Researcher
February 2012 - April 2012
Texas A&M University
Position
  • ESR spectroscopy of H, D, and N atoms captured in IHCs
Education
September 1985 - June 1991
Rostov-na-Donu State University
Field of study
  • physics

Publications

Publications (69)
Article
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Complex structures, consisting of a large number of interacting subsystems, have the ability to self-organize and evolve, when the scattering of energy coming from the outside ensures the maintenance of stationary ordered structures with an entropy less than the equilibrium entropy. One of the fundamental problems here is the role of quantum phenom...
Article
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The nonlinear dust-acoustic instability in the condensed submicron fraction of dust particles in the low-pressure glow discharge at ultra-low temperatures is experimentally and theoretically investigated. The main discharge parameters are estimated on the basisof the dust-acoustic wave analysis. In particular, the temperature and density of ions, a...
Article
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Experimental results on dust-acoustic waves study in weakly-coupled cryogenic dusty plasma within the DC glow discharge are discussed. Analysis of dust particle trajectories, their velocity distributions and the pair correlation function allow us to conclude that the 3-D dusty plasma structure studied at T = 83 K was most likely a gaseous structure...
Article
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We reviewed systems formed in liquid and solid helium-4 at high concentrations (1016 cm−3 and higher) of impurity particles. A new explanation for the reversible coagulation of fine hydrogen particles into big flakes observed upon the transition of liquid helium into the superfluid phase is proposed. The importance of nanoclusters presence in heliu...
Article
Determination of the gas temperature in the afterglow plasma jet of pre-cooled helium propagating inside a dense helium vapor at 1.4 K is a difficult task. In this work we analyze the applicability of the emission spectra from oxygen atoms and nitrogen molecules for determination of the local temperature of the gas. Oxygen is always present as a tr...
Article
The phenomena observed in ultracold multimodal dusty plasma in the DC glow discharge cooled with superfluid helium are discussed. Intense sputtering of the clay insert produces a sputtered material flow ~ 100 ng/s at T ≤ 2 K. The synthesis rates for nanoclusters and filaments were estimated for the first time. The emission from the filaments stimul...
Article
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Recent studies of dusty plasma structures formed by polydispersed CeO2 particles in a dc glow discharge at a temperature T > 1.6 K were shown to be the first experiments on dusty plasma in an exotic dark glow discharge mode. The properties of cryogenic helium plasmas at T ~ 1 K are summarized and discussed.
Article
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Great enhancement of molecular nitrogen luminescence in the afterglow of nitrogen-helium gas mixtures was observed at temperatures ≤ 10 K. The effect is explained by the increased efficiency of the recombination of nitrogen atoms and energy transfer from metastable nitrogen molecules and helium atoms to nitrogen molecules in the cold dense helium v...
Article
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A new simple experimental technique has been elaborated to test applicability of impedance spectroscopy for studying processes during destruction of impurity-helium condensates. Combination of methods of optical spectroscopy, impedance spectroscopy and current spectroscopy to study the destruction processes of impurity-helium condensates has been a...
Article
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A multimodal dusty plasma formed in a positive column of the direct current glow discharge at superfluid helium temperatures has been studied for the first time. Formation of a liquid-like dusty plasma structure occurred after injection of polydisperse cerium oxide particles in the glow discharge. The coupling parameter ~10 determined for the dusty...
Article
A new experimental setup for studying cryogenic helium plasma and dusty plasma structures in a DC gas discharge within the temperature range of 1.6–300 K is described. For the first time, dusty plasma structures were observed and studied at temperatures below 4 К.
Conference Paper
Full-text available
The helium plasma exhibits a rich network of processes involving energy transfer even at room temperature. Many neutral and ionic states of He atoms and He2 molecules are involved in the energy circulation in helium plasmas at cryogenic temperatures. Nevertheless, optical spectra of excited helium species are almost useless for the temperature dete...
Article
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Impurity-helium condensates (IHCs) created by injection of nitrogen atoms and molecules as well as rare gas (RG) atoms (Ne, Ar, and Kr) into superfluid \(^4\)He have been studied via electron spin resonance (ESR) techniques. We investigated the influence of addition of rare gas atoms (Ne, Ar, and Kr) into the condensing \(\hbox {N}_2\)–He gas mixtu...
Article
The dusty plasma structures in a glow discharge of helium in a tube cooled by superfluid helium at a temperature of 1.6 K and higher have been studied experimentally. The bimodal dust plasma formed by clouds of polydisperse cerium dioxide particles and polymer nanoparticles has been analyzed. We have observed wave oscillations in the cloud of polym...
Article
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We observed the appearance of a broad feature at 360 nm in spectra obtained during the destruction of ensembles of molecular nitrogen nanoclusters containing stabilized nitrogen, oxygen, hydrogen and deuterium atoms. We attribute this broad feature with a maximum at 360 nm to the N4 polynitrogen molecules which are the product of the neutralization...
Article
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We have studied the luminescence of molecular nitrogen nanoclusters containing stabilized nitrogen, oxygen, hydrogen, and deuterium atoms. Optical spectra were observed during the destruction of these ensembles of nanoclusters accompanied by a rapid release of chemical energy stored in the samples. Several interesting features were observed includi...
Article
We observed the spectra within the wavelength range of 910–990 nm in theof emission of the corona discharge in supercritical helium gas at 6–11 K. This spectral range contains the molecular bands of the excimer radiative transitions (c3Sigma+ - a3Sigma+ ) between the electron-vibrational-rotational levels of the c3Sigma+ and the a3Sigma+ triplet st...
Article
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We studied optical and electron spin resonance spectra during destruction of porous structures formed by nitrogen–rare gas (RG) nanoclusters in bulk superfluid helium containing high concentrations of stabilized nitrogen atoms. Samples were created by injecting products of a radio frequency discharge of nitrogen–rare gas–helium gas mixtures into bu...
Article
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In this study argon nanoclusters (800 to∼6500 atoms) formed in supersonic gas jets are compared to the nanoclusters stabilized in superfluid helium. High-energy electron and X-ray diffraction methods are utilized. Both techniques allow investigation of isolated clusters. It is shown that the theoretical prediction of the so-called multiply twinned...
Article
We observed the spectra within the wavelength range of 910–990 nm of emission of the corona discharge in supercritical helium gas at 6–11 K. This spectral range contains the molecular bands of the He2* excimer radiative transitions between the electron-vibrational-rotational levels of the and the triplet states. We have determined the populations o...
Article
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We studied the dynamics of thermoluminescence during destruction of porous structures formed by nanoclusters of nitrogen molecules containing high concentrations of stabilized nitrogen atoms. The porous structures were formed in bulk superfluid helium by injection of the products of discharges in nitrogen–helium gas mixtures through the liquid heli...
Article
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Analysis of old and recent experiments on thermoluminescence of cryocrystals and nanoclusters of N2, Ne, Ar, and Kr containing stabilized nitrogen atoms, suggests that the so-called γ-line may correspond to the bound–bound transition 1D–3P of nitrogen anions N− formed in solids by the association of delocalized electrons and metastable nitrogen ato...
Article
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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...
Article
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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 molecul...
Article
We present the first observations of excimer XeO* molecules in molecular nitrogen films surrounding xenon cores of nanoclusters. Multishell nanoclusters form upon the fast cooling of a helium jet containing small admixtures of nitrogen and xenon by cold helium vapor (T = 1.5 K). Such nanoclusters injected into superfluid helium aggregate into porou...
Article
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We describe a method for creating a high flux beam of cold atoms and molecules. By using this beam method, spectroscopic studies of the afterglow of oxygen-helium gas mixtures at cryogenic temperatures were performed. The cooling by helium vapor of a helium jet containing trace amounts of oxygen after passing through a radiofrequency discharge zone...
Article
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Impurity-helium condensates created by injection of hydrogen (deuterium) atoms and molecules as well as rare gas (RG) atoms (Ne and Kr) into superfluid 4 He have been studied via electron spin resonance (ESR) techniques. Measurements of the ground-state spectroscopic parameters of hydrogen and deuterium atoms show that the nanoclusters have a shell...
Article
Full-text available
We present investigations of the afterglow of oxygen-helium gas mixtures at cryogenic temperatures. The cooling of a helium jet containing trace amounts of oxygen after passing through a radio frequency discharge zone led to the observation of strong emissions from atomic oxygen. The effect results from the increasing efficiency of energy transfer...
Article
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We have studied thermo-stimulated luminenscence and electron emission of nitrogen films and nanoclusters containing free radicals of atomic nitrogen. Thermo-stimulated electron emission from N2 nanoclusters was observed for the first time. Thermo-stimulated luminescence spectra obtained during the destruction of a N2–He sample are similar to those...
Article
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Injection of an impurity-helium gas jet passed through a radiofrequency discharge into a volume of superfluid helium leads to the growth of nanoclusters of impurity species which form impurity-helium condensates (IHCs). IHCs are porous materials with very low impurity density (∼1020 cm−3). High average concentrations of stabilized free radicals can...
Article
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We present optical spectra of impurity-helium condensates during the process of their formation by injection of gas mixtures N2-Rg-He (Rg=Ne, Kr) into bulk superfluid helium after passing through a RF discharge. Atomic lines of He, Ne, Kr, N, O atoms as well as bands (1+ and 2+ systems of N2) are present in the spectral range 320-1100 nm studied in...
Article
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Macroscopic ensembles of weakly interacting argon nanoclusters are studied using x-ray diffraction in low vacuum. As the clusters grow by fusion with increasing temperature, their structure transforms from essentially face-centered cubic (fcc) to hexagonal close packed as the cluster size approaches ∼10^{5} atoms. The transformation involves interm...
Article
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Impurity–helium condensates (IHCs) containing nitrogen and krypton atoms immersed in superfluid 4 He have been studied via a CW electron spin resonance (ESR) technique. The IHCs are gel-like aggregates of na-noclusters composed of impurity species. It was found that the addition of krypton atoms to the nitrogen–helium gas mixture used for preparati...
Article
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The results of investigations of thermoluminescence dynamics during destruction of neon-helium and krypton-helium condensates containing stabilized nitrogen and oxygen atoms are presented. Spectra of the thermoluminescence of a krypton-helium condensate contained bands of N and O atoms and NO molecules. The intensities of the bands in these spectra...
Article
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Impurity–helium condensates formed by krypton nanoclusters containing atoms and molecules of hydrogen isotopes have been studied via an electron spin resonance ESR technique. Analysis of the ESR spectra has shown that most of the H and D atoms reside on the surfaces of Kr nano-clusters. Very large average concentrations have been obtained for H ato...
Article
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In an optical cryostat, the sample temperature is limited by the 300K thermal radiation transmitted through the observation windows. As discussed in this paper, the corresponding heat load should be brought much below the μW level by using suitable cold IR filters. However, there are situations where one wants to directly check the absence of IR he...
Article
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Impurity-helium condensates (IHCs) containing krypton and hydrogen atoms immersed in superfluid $^{4}\text{H}\text{e}$ have been studied via cw electron-spin-resonance (ESR) techniques. The IHCs are gel-like aggregates of nanoclusters composed of krypton and hydrogen atoms. We have found that very high average $($\sim${}{10}^{19}\text{ }{\text{cm}}...
Article
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Impurity-Helium condensates (IHCs) containing krypton and hydrogen atoms have been studied in superfluid helium-4 via CW ESR techniques. The IHCs studied in this work are gel-like aggregates of nanoclusters composed of krypton and hydrogen atoms. We have found that such samples contain very high average concentrations of hydrogen atoms (~1018cm-3)...
Article
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Impurity–helium condensates containing krypton atoms and also atoms and molecules of hydrogen isotopes have been studied via an electron spin resonance (ESR) technique. Analysis of the ESR spectra shows that most of the H and D atoms reside in molecular layers (H2 or D2) formed on the surfaces of Kr nanoclusters. The thickness of the molecular film...
Article
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We have studied superfluid helium capture in a sample of silica aerogel of 98.2% porosity in the temperature range from 1.22K up to 1.89K. The high retention of He in the aerogel sample corresponds to a similar phenomenon in impurity-helium condensates, in which very high values of the ratio of helium atoms to impurity atoms (up to 60) have been se...
Article
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Macroscopic samples (volume approximately cm(3), atomic density approximately 10(19) -10(20) cm(-3)) of noble-gas nanoclusters (size approximately 5-6 nm) were produced in superfluid helium by an impurity-helium gas injection technique. X-ray diffraction measurements show that the samples consist of weakly interacting nanoclusters with fivefold sym...
Article
Bulk quantities (volume˜cm^3, atomic density˜10^ 19-10^20 cm-3) of noble gas nanoclusters (size˜5-6 nm) were produced in superfluid helium by injection technique. X-ray diffraction measurements show that the samples consist of weakly interacting nanoclusters with five-fold symmetry axes, such as icosahedra and decahedra. These results open new oppo...
Article
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The stabilization and recombination of nitrogen atoms N(4 S) in nitrogen-helium and nitrogen–neon-helium condensates obtained by the injection of impurity particles from a gas discharge into bulk superfluid helium are investigated by the EPR method. It is established that the stabilized nitrogen atoms reside inside and on the surface of impurity cl...
Article
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We employed en electron spin resonance (ESR) technique for investigating the long term behavior of hydrogen and deuterium atoms in the HD-D2 impurity helium solids that were created by sending a gas mixture [H2]:[D2]:[He]= 1:4:100 through a radio-frequency electrical discharge into a volume of superfluid 4He at T = 1.5 K. H and D atoms were stabili...
Article
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Impurity-helium solids created by injecting deuterium atoms and molecules into superfluid 4He have been studied via x-ray-diffraction and electron-spin-resonance (ESR) techniques. X-ray-diffraction measurements show that these solids are highly porous gel-like structures consisting of D 2 clusters with the characteristic cluster size of 90±30 Å. Th...
Article
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Impurity-helium solids created at T=1.5 K by sending deuterium-helium and nitrogen-helium gas mixtures through a zone of high frequency electrical discharge into superfluid ^4He have been studied via x-ray diffraction and electron spin resonance (ESR) techniques. X-ray diffraction measurements show that these solids are highly porous gel-like struc...
Article
Full-text available
Impurity-helium solids are porous gel-like materials held together by Van der Waals forces. They consist of impurity atoms, molecules or clusters of atoms and molecules, each surrounded by very thin layers of solid helium. Impurities studied include neon, krypton, and molecular and atomic nitrogen, hydrogen and deuterium. The pore sizes and cluster...
Article
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Impurity-helium solids created by injecting deuterium atoms and molecules into superfluid 4He have been studied via electron spin resonance (ESR) and x-ray diffraction methods. We measured the g-factor, the hyperfine constant and the spin-lattice relaxation time of D atoms in D-D2-He solids. These measurements show that D atoms are mainly stabilize...
Article
Full-text available
A small permanent magnet was used to attract impurity-helium solid samples composed of hydrogen, deuterium, and nitrogen radicals. The magnetic field gradient was sufficiently strong to lift each of the impurity-helium solids while submerged in superfluid helium, but only strong enough to lift one of four samples through the liquid surface. This su...
Article
We have introduced guest particles into superfluid helium using a directed helium jet containing traces of species under study. The distinguishing peculiarity of the method consists in that the whole system is sealed from the cryostat main helium bath. This allows: (i) on the account of the absence of evaporating helium upflow to realize a complete...