Properties of shock-compressed liquid krypton at pressures of up to 90 GPa

The following quantities of shock-compressed liquid krypton are measured behind a plane shock front at pressures up to 90 GPa: compressibility up to densities of 7 g/cm³, brightness (color) temperatures of 6000–24000 K, and electrical conductivities of 40–60000 (Ω·m)⁻¹. X-t diagram methods are used to estimate sound speeds of up to 5.5 km/s at pressures of 30–75 GPa. The optical absorption coefficients in the violet and red (30–300 cm⁻¹) are measured at pressures of 20–90 GPa from the rise in brightness of the shock front luminosity. The optical reflection coefficient of the shock front (∼13%) at a pressure of 76.1 GPa is measured for the first time. Zh. éksp. Teor. Fiz. 116, 551–562 (August 1999)     

Electrical Conductivity of Noble Gas Plasmas in the Warm Dense Matter Regime

The electrical conductivity of noble gas plasmas is investigated by using the relaxation‐time approximation in the density range 10^–5–10 g cm^–3 and temperature range 10⁴–10⁵ K. The electrical conductivity calculated shows reasonable consistency with shock wave experiments and theoretical simulations at above 2 × 10⁴ K where the Coulomb interaction dominates. A nonmetal to metal transition in helium plasma is predicted at 2.4 g cm^–3 and shown reasonable agreement with the most recent shock wave experiment (above 1.9 g cm^–3). Furthermore, the insulator‐metal transition densities of all the noble gas plasmas are predicted and compared with available results (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

液态气体冲击压缩实验技术

 利用液氮制冷技术实现低温靶及气体样品液化,并通过二级轻气炮加载进行液态气体0～60 GPa的冲击压缩实验。较详细地讨论了制冷系统与样品靶、靶室内外各环节之间可靠的低温真空连接等工程问题,样品靶的温度调节与控制,液态气体样品的灌注及液体量（或液面） 的判断依据,样品压缩后的冲击波速度测量和电导率测量等技术问题。     

Metallization of fluid hydrogen at 140 GPa (1.4Mbar) by shock compression

Abstract

The minimum electrical conductivity of a metal was produced in dense hydrogen using shock compression. Metallization occurs at 140 GPa (1.4 Mbar), 0.6 g/cm³ (ninefold compression of initial liquid-H₂ density), and 3000 K. The relatively modest temperature generated by a reverberating shock wave produced the metallic state in a warm quantum fluid at a lower pressure than expected previously for the crystallographically ordered solid at low temperatures. Future research directions are discussed. Possible scientific and technological uses of metastable solid metallic hydrogen are speculated upon in the unlikely event that the metallic fluid can be quenched to this state at ambient pressure and temperature.     

Omega phase of zirconium: Formation under shock wave compressin and stability at atmospheric pressure

Abstract

The structure of Zr after shock compression in the 8–32 GPa range at initial tempertures 290 K and 90 K has been investigated by X-ray diffraction and transmission electron microscopy. ω-phase fraction vs. peak pressure and crystallographic relationship between α- and ω-phases have been obtained. A dilatometric study of Zr samples containing ω-phase has been performed.     

聚四氟乙烯动态特性的实验研究

 在10~55 GPa的高压范围用化爆装置、采用阻抗匹配法测得了聚四氟乙烯（初始密度ρ₀=2.19 g/cm³）的冲击波速度D和波后粒子速度u之关系为：D=2.10+1.62u（mm/μs）。在0.2~3 GPa的低压范围用气炮装置、采用电磁速度计测量了材料内加、卸载过程的拉格朗日粒子速度波形，获得的冲击加载D-u关系为：D=1.24+3.72u-1.94u²（mm/μs）。实测卸载曲线和加载冲击绝热线接近一致，残余应变似乎不存在或者说很小；弹性区段很不明显，聚四氟乙烯本质上呈现出塑性性质。     

Quantum chemical study on ·Cl-initiated degradation of ethyl vinyl ether in atmosphere

ABSTRACT

A theoretical investigation on oxidation reaction of ethyl vinyl ether (EVE) and .Cl are carried out in this paper. By employing M06-2x/6-31?+?g(d,p)//6-311++g(3df,2p) method, complex reaction mechanisms are assumed on the basis of thermodynamic data. All the .Cl-addition reactions are dominant channels. The corresponding major products, such as ethyl formate, acetaldehyde and several chloro compounds, are generated from .Cl-addition to double bond of EVE. These products play an important role in the formation of secondary organic aerosol. By employing MESMER grogram, rate coefficients of the primary reactions are computed in the temperature range of 200–400?K and the pressure range of 500–2000?Torr. Combined with the kinetic data and temperature, an Arrhenius equation is fitted as k _EVE+Cl?=?1.54?×?10^?10 exp (121.9/T). Also, the rate constant at 298?K and 760?Torr is calculated to be 2.17?×?10^?10?cm³ molecule^?1?s^?1. Furthermore, the atmospheric lifetime of EVE with respect to .Cl is estimated to be 4.3–11.9?h in different regions. The short lifetime indicates that ·Cl-initiated oxidation is competitive in the degradation of EVE in some special areas. This work could confirm the experimental investigation and serve as the supplement of our previous theoretical studies.     

The investigation of the optics of shock-compressed strongly correlated plasma

Rare gas plasmas at high temperatures and pressures, produced by explosive shock fronts, are explored using laser diagnostics. The analysis of the response of a dense plasma to an electromagnetic wave of moderate-intensity proves successful for investigating properties and the validity of physical models describing the behaviour of dense and non-ideal plasmas. We present new experimental data for the reflectivity of oblique incidence of polarized electromagnetic waves on the front of shock-compressed xenon plasmas. The optical properties of strongly correlated plasma were studied in the near-infrared and green spectral regions at a plasma mass density ρ = 0.83 g/cm³ and temperature T = 32900 K. The spatial parameters of the plasma transition shock-front layer are determined by solving numerically the electromagnetic field equations.     

Letters to the editor

Abstract

Optical absorption spectra of TeO₂ crystals, irradiated at room temperature by up to 2·10¹⁸ cm^?2 10-MeV electrons and subsequently annealed to 575K, are studied. The dependence of Urbach absorption edge parameters in TeO₂ on the electron beam fluence is discussed. The irradiation-induced near-edge broad (2.5–3.5eV) absorption band is shown to be related to oxygen vacancies, annealing at 475–525K.     

Carbonization in boron-ion-implanted polymethylmethacrylate as revealed from Raman spectroscopy and electrical measurements

ABSTRACT

The results of Raman spectroscopy and electrical measurements of 40 keV boron-ion-implanted polymethylmethacrylate with ion doses from 6.25 × 10¹⁴ to 5.0 × 10¹⁶ ions/cm² are reported for the first time. The Raman spectra recorded in the 400–3800 cm^?1 range, showing the formation of new carbon–carbon bands for the as-implanted samples at higher ion doses (>10¹⁶ ions/cm²), are found to be an additional support for carbonization processes earlier revealed by slow positrons. The current–voltage dependences at 360 K testify also that the as-implanted samples examined with higher fluences (3.75 × 10¹⁶ and 5.0 × 10¹⁶ ions/cm²) have created a very thin conductive layer or conductive joints due to carbonization.     

Determination of absorption cross sections for oxygen molecules in the Schumann-Runge band region at high temperatures

We have measured the absorption cross sections of oxygen molecules in oxygen and in an oxygen-argon mixture heated by a shock wave, in the wavelength range 190–250 nm at temperatures of 1500–7000 K, for thermal equilibrium conditions behind the shock wave front. Analysis of the absorption cross sections obtained allowed us to select a data set that adequately describes the absorption characteristics of the electronic transition X³Σ _g ⁻ → B³Σ _u ⁻ for the oxygen molecule. In order to approximate the temperature dependence of these cross sections at a temperature of 1500–4500 K, we chose the function σ(λ, T) = σ₀(λ)(1 − exp (−θ/T)) exp (− n*θ/T) where θ₀ = 1.4·10⁻¹⁷, 1.4·10⁻¹⁷, 1.2·10^{− 17}, and 1.3·10⁻¹⁷ cm², n* = 3.1, 4.1, 5.6, and 7.47 for wavelengths 190, 210, 230, and 250 nm, respectively; θ = 2240 K is the characteristic temperature of the O₂ molecules. The approximation error was 19–25% and did not exceed the experimental error. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 13–17, January–February, 2006.     

Stark broadening of singly ionized strontium and calcium lines

Profiles of five calcium II and six strontium II lines have been measured in an argon plasma behind the reflected shock wave. The plasma was produced in an electromagnetically drivenT tube and calcium and strontium were present as an impurities. Electron densities were in the range 1.91–3.40·10¹⁷ cm^?3 and the electron temperatures between 10300 and 14200 °K. The half halfwidths of the measured profiles of some Ca II and Sr II multiplets show large discrepancies with theoretical predictions.     

Measurement of density, temperature, and electrical conductivity of a shock-compressed nonideal nitrogen plasma in the megabar pressure range

Kinematic and thermodynamic parameters of shock-compressed liquid nitrogen are measured behind the front of a plane shock wave using plane wave and hemispherical shock wave generators. In these experiments, high values of compression parameters (shock-compressed hydrogen density? ≈ 3.25 g/cm³ and temperature T≈ 56000 K at a pressure of P ≈ 265 GPa) are attained. The density, pressure, temperature, and electrical conductivity of the nonideal plasma of shock-compressed liquid nitrogen are measured. A nearly isochoric behavior of the nitrogen shock adiabat is observed in the pressure range P = 100–300 GPa. The thermodynamics of shock-compressed nitrogen is an alyzed using the model of the equation of state in the quasi-chemical representation (SAHA code) as well as the semiempirical wide-range equation of state developed at the Institute of Experimental Physics. Experimental results are interpreted on the basis of calculations as the fixation of the boundary of transition of shock-compressed nitrogen from the polymer phase to the state of a strongly nonideal plasma at P ≈ 100 GPa, ? ≈ 3.4 g/cm³.     

Magnetically stabilized electron-hole liquid in indium antimonide

Luminescence spectra of sufficiently pure n-type indium antimonide crystals (N _D−N _A=(1–22)·10¹⁴ cm⁻³) in a magnetic field of up to 56 kOe, at temperatures of 1.8–2 K, and high optical pumping densities (more than 100 W/cm²) have been studied. More evidence of the existence of electron-hole liquid stabilized by magnetic field has been obtained, and its basic thermodynamic parameters as functions of magnetic field have been measured. When the magnetic field increases from 23 to 55.2 kOe, the liquid density increases from 3.2·10¹⁵ to 6.7·10¹⁵ cm⁻³, the binding energy per electron-hole pair rises from 3.0 to 5.2 meV, and the binding energy with respect to the ground exciton level (work function of an exciton in the liquid) rises from 0.43 to 1.2 meV. Zh. éksp. Teor. Fiz. 111, 737–758 (February 1997)     

Spin lattice relaxation of F+ centers in neutron irradiated cao crystals

Abstract

We have measured the electron spin-lattice relaxation rates of F⁺ centers in CaO crystals at different F⁺ centers concentrations (from 5.8·10¹⁵ to 1.4·10¹⁷ cm^?3) in magnetic fields from 10^?3 to 4.8 T and temperatures from 0.4 to 4.2 K. At temperatures above 1 K the relaxation rate is nearly proportional to the F⁺ centers concentration. Spin diffusion to fast relaxing centers is essential in determining the F⁺ centers spin polarization decay.     

Bestimmung von Temperatur und Dichte eines Gleitfunkens aus der Bremsstrahlung im Infrarot

The absolute intensity of a vacuum sliding spark (length 2–10 cm, half cycle 0,8 μsec) has been measured in the spectral region between 0,4 and 3μ. From the long wavelength radiation emitted from an optically thick layer, one gets the temperature, from the short wavelength radiation emitted from an optically thin layer, one obtains the density. Using polyethylene as an insulator we reached a temperature of 4·10⁵ °K at electron densities of 8·10¹⁸ cm^?3 and current densities of 1.2·10⁶ A/cm². The temporal development of temperature and density has been determined. The maximum intensity at λ=0.43 μ was found to be 5·10⁴ (7·10¹⁰ W/cm³ ster) as large as that of the positive crater of a properly driven carbon arc. At λ=3 μ this same parameter turned out to be 300 times as large (5·10⁷ W/cm³ ster).     

A high power radiation source in the vacuum ultraviolet

A sliding spark over solid xenon has been developed with the object to serve as a vacuum-ultraviolet light source for the photoionization of gases, especially hydrogen and inert gases. An intensity of 1·10¹² Watt/cm³ sr at 800 Å has been observed, lasting about 5 μsec. The emitting area was approximately 1.6 cm². This light source has been used to irradiate a test gas of xenon at 0.4 m Torr. An electron density of 2·10¹² cm^?3 was detected at a distance of 80 cm with an 8 mm microwave interferometer.     

Laser driven shock wave studies in gold coated Plexiglas targets

Abstract

Laser-driven shock wave propagation in a transparent material such as Plexiglas coated with a thin overlayer of gold is studied using the technique of high speed optical shadowgraphy. A Nd: glass laser was focussed to produce intensities in the range of 10′²-10′⁴W/cm² on the target, within an irradiation spot diameter of 160 pm, optical shadowgrams were recorded bya second harmonic (0.53 pm wavelength) pulse. Shock pressures and scaling of pressure with laser intensity was studied. Shock pressures in gold-coated Plexiglas target was observed to be considerably higher compared to those in uncoated targets. This enhancement of shock pressure has been explained on the basis of contribution of an X-ray driven ablative heat wave in the gold plasma. Shock pressure values show a close agreement with those obtained from a one-dimensional Langrangian hydrodynamic simulation. Shadowgrams of shock fronts produced by non-uniform spatial laser beam irradiation profiles have shown complete smoothing when a gold layer is used on a Plexiglas target.     

Dynamics of high-temperature plasma formation during laser irradiation of three-dimensionally structured,low-density matter

Results are presented from an experimental investigation of the properties of the plasma produced by the action of a radiation pulse at the second harmonic of a Nd laser, with average intensity ~5·10¹⁴ W/cm² in the focal spot, on flat targets consisting of porous polypropylene (CH)_x with an average density of 0.02 g/cm³ (close to the critical plasma density) and with ~50 μm pores. The properties of the laser plasma obtained with porous and continuous targets are substantially different. The main differences are volume absorption of the laser radiation in the porous material and much larger spatial scales of energy transfer. The experimentally measured longitudinal ablation velocity in the porous material was equal to (1.5–3)·10⁷ cm/s, which corresponds to a mass velocity of (3–6)·10⁵ g/cm²· s, and the transverse (with respect to the direction of the laser beam) propagation velocity of the thermal wave was equal to ~(1–2) ·10⁷ cm/s. The spatial dimensions of the plasma plume were ~20–30μm. The plasma was localized in a 200–400μm region inside the target. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 462–467 (10 October 1996)