Brillouin spectroscopy of induced phonons in x-cut quartz

Triplepass Brillouin spectroscopy was used to detect longitudinal bulk waves generated at a y, z-surface of x-cut quartz. A comparison with Brillouin scattering by thermal phonons shows that Brillouin scattering by induced phonons admit sound attenuation measurements in a dynamic range of almost 80 dB at room temperature. It is also shown that our experimental results agree very well with results obtained at lower frequencies by pulse-echo measurements.     

Shock-wave compression of hydrogen to pressures of 65 GPa

The results of experiments on determining the shock-wave compression of initially solid hydrogen (protium) in the pressure range from 17 to 66 GPa are reported. The data have been obtained by using spherical explosive charges. Pressure in samples is created by the impact of a steel striker accelerated to maximum velocities of 23 km/s. Gaseous protium is converted to the solid state using a special cryogenic cooling system.     

Shock-wave compression of hydrogen isotopes condensed under megabar pressures

Experiments on shock wave compression of solid hydrogen (protium) up to 66 GPa and deuterium (in the initially liquid or solid phase) up to 123 GPa using spherical devices where a steel ball (impactor) is explosion-accelerated to 23 km/s are described. The experimental data are compared with those obtained by American researchers for liquid deuterium and protium, who used conventional explosives and light-gas guns as energy sources in the experiments carried out on the Z machine at Sandia National Labs, where an impactor was accelerated by an ultrahigh magnetic field, or on the NOVA laser at the Livermore National laboratory. Our data agree well with those derived by Sandia Labs.     

冲击加载条件下融石英对水的凝固相变的诱导效应

利用轻气炮冲击加载手段和透光性在线测试技术研究了融石英对水的再冲击结冰相变过程的影响.实验结果表明,当再冲击压力为1.28 GPa时,与融石英直接接触的水会发生凝固相变,而与融石英不接触的水在约2 μs观测期间仍然保持液相,证实融石英对水的冲击凝固相变过程产生了明显的诱导作用.同时还给出了相变动力学的解释. 关键词： 冲击 水 相变     

Piezoelastic properties of retgersite determined by ultrasonic measurements

The elastic tensor of the tetragonal NiSO₄ . 6H2O (retgersite) was measured with a resonant ultrasonic plane parallel plate technique at room temperature as a function of hydrostatic pressure in the range of 0.1-50 MPa and the piezoelastic coefficients have been derived. The monotonic increase in the c_ij shows that retgersite does not undergo a phase transition in this pressure range. Density functional theory (DFT) based calculations within the linear response method were used to predict the variation of the c_ij in the range of 1-1000 MPa in the static limit. A comparison of the two data sets shows that while structural parameters and elastic stiffness coefficients are well reproduced by the DFT model, theoretical piezoelastic coefficients of compressible compounds are only in moderate agreement with the corresponding experimental values. The limitations of DFT-based calculations for the calculation of piezoelastic coefficients are discussed.     

石英拉曼峰进行压力标定的误差研究

在常温常压下进行了作为压标的石英颗粒的拉曼光谱测量和研究。研究结果发现,在25℃和常压条件下,不同的石英颗粒测得的Si—O振动模在463.59～464.65cm-1范围内变化,误差为(±0.1～±0.3)cm-1。其中不同石英颗粒拉曼峰的最大差异达1.06cm-1,远远大于其测量误差。我们认为这是由于石英破碎时使石英颗粒内产生的应力所致。因此,在进行金刚石压腔高温高压实验的压力确定时,必须以常压下实测的Si—O振动模测量值为零压参考点。另外,拉曼光谱仪的波数漂移以及环境温度的不稳定均会造成不可忽视的压力测量误差,应对此进行校正。     

Cesium profiles in silicon and in SiO2-Si double-layers as determined by SIMS measurements

Secondary ion mass spectrometry is used to determine

1. the range distributions of 10–100 keV cesium ions implanted into monocrystalline silicon and
2. the cesium profiles in SiO₂-Si double layers formed by implantation of cesium into silicon surfaces and subsequently converting the implanted layer into SiO₂ through thermal oxidation at 800°C and 1000°C.

In the first case (a) non-Gaussian distributions are observed for the implanted cesium atoms. Their projected ranges show a somewhat stronger energy dependence as predicted from LSS-theory. The values for standard deviations and third central moments are in good agreement with theory at low energies but are larger up to a factor of 1.5 at higher energies. In the second case (b) cesium ions present in the implanted silicon layer are introduced into the growing oxide layer during oxidation and pile up at both oxide interfaces.     

Anisotropy of electrical breakdown in crystalline quartz

Partial breakdown of crystalline silicon dioxide in a pulsed nonuniform electric field is considered. Breakdown channels lie in planes of silicon ions that are parallel to the c axis of the crystal (up to six equivalent directions of the channels are observed). The formation of breakdown channels is satisfactorily described in terms of cascade Auger transitions with regard to the crystallochemical symmetry of the quartz lattice.     

Shielding current density in Mg-doped YBCO-123 as determined by a.c. magnetic-susceptibility measurements

Il Nuovo Cimento D - High-resolution a.c. magnetic-susceptibility measurements have been performed on sintered samples of Mg-doped YBCO superconductors YBa2(Cu1−x Mg x )3O7−δ...     

The dispersion of nickel oxide supported on boron-modified silicas,as determined by TEM and XPS measurements

The dispersion of NiO supported on boron-modified silicas has been studied by transmission electron microscopy (TEM) and XPS. The TEM experiments showed that all NiO is present in the form of crystallites; values for the dispersion were calculated on the basis of measurements of the size distributions of these crystallites. The XPS measurements were interpreted using a model which assumes large particle sizes and no re-partitioning of the supported species between internal pores and the surface when boron-modification is performed. The variations of dispersion with boron content obtained from this model agree well with the variations measured by TEM.     

Surface magnetic anisotropy in glass-coated amorphous microwires as determined from ferromagnetic resonance measurements

The ferromagnetic resonance frequency of different Co base glass-coated amorphous magnetic microwires about 3.5 μm in diameter with negative, vanishing and positive magnetostriction has been investigated from power absorption measurements in the microwave frequency range. The experimental technique employed here involves the replacement of the dielectric of a coaxial transmission line by the sample to be measured. From the evolution of the resonance frequency with DC applied magnetic field, the surface magnetic anisotropy field of the microwires has been quantitatively obtained and, as expected, found to depend on the sign and strength of the magnetostriction. Similar values for the surface anisotropy are obtained in comparison with bulk anisotropy as determined from quasi-static hysteresis loops measurements.     

Magnetic anisotropy determined by differential magnetization measurements in twisted amorphous ribbons

A new method of measurement, which enables a determination of the in-plane anisotropy in magnetic metallic glass ribbons, has been developed. It can be used for materials with the easy axis of magnetization parallel as well as perpendicular to the ribbon axis. The method is based on measurements of the stress dependence of the inhomogeneous magnetization obtained by twisting the ribbon around the ribbon axis. The required experimental equipment is very simple, and the value of the anisotropy constant comes out directly as an equivalent internal stress field.     

Free-carrier concentration in n-doped InP crystals determined by Raman scattering measurements

Raman spectra from n-InP samples covering a wide range of concentrations (˜10¹⁶ to 10¹⁹ cm^-3) have been measured. Free-carrier concentrations deduced from the analysis of the upper LO phonon-plasmon coupled modes are compared with values obtained from conventional electrical determinations. It is found that a tight 1 to 1 correlation exists between the results of the two techniques, thus confirming Raman scattering as a powerful analytical tool for the characterization of InP substrates.     

Electric field controlled g-factor in parabolic well determined by transport measurements

The Shubnikov de Haas oscillations in parabolic well are studied in the tilted magnetic field. The electric field displaces the electron wave function along Z-axis and leads to the strong variation of the average bare g-factor in such system. From the measurements of the filling factor ν_c at which the spin gap collapse occurs, we deduce the total Zeeman energy, which consists of the bare Zeeman energy and exchange-correlation term. By investigating of the variation of ν_c in tilted field we reliably extract the bare g-factor as a function of the gate voltage.     

磁驱动准等熵加载下Z切石英晶体的折射率

基于CQ4脉冲功率实验装置开展了Z-切石英晶体在磁驱动准等熵加载下的窗口折射率修正关系研究. 实验中采用激光波长1550 nm的双源光外差测速仪测量获得了LiF窗口和Z-切石英晶体窗口与不同厚度极板界面的粒子速度. 利用反积分方法由实验测得的LiF窗口与极板界面粒子速度计算得到了极板的加载磁压力历史; 以获得的磁压力为输入条件, 采用LS-DYNA计算软件正向计算得到石英晶体窗口与极板界面的真实粒子速度历史. 由实验获得的Z-切石英晶体窗口/极板界面表观粒子速度和计算得到的真实粒子速度, 获得了Z-切石英晶体弹性极限内的连续的折射率修正关系, 将其折射率修正关系的适用压力范围拓宽至14.55 GPa. 表观粒子速度与真实粒子速度关系采用线性拟合时, 折射率修正关系为n=1.087 (± 0.008)+0.4408ρ/ρ₀, 与冲击数据拟合的结果一致. 由折射率实验数据对Z-切石英晶体的极化率分析认为, 在其弹性极限压力范围内加载路径和温度对折射率的影响可以忽略.     

Configurational coordinate diagram of Ni2+ doped silver halide crystals,as determined by optical and luminescence measurements

Optical and luminescence measurements were carried out on Ni²⁺ doped silver halide crystals. The configurational coordinates of the ground and the first excited states made it possible to explain the important optical properties, such as the Stokes shift between the ground and excited states, the broadening of the bands with temperature and the thermal quenching. Determining the configurational coordinate diagram of the ground and first excited states is the first step for the design and fabrication of solid state and fiber lasers which are based on Ni²⁺ doped silver halides and which operate in the middle infrared.     

Oxygen ion diffusion in perovskite-type oxides determined by permeation and by relaxation measurements

Oxygen ion diffusion in oxides of the perovskite-type structure was determined by two methods of measurement: i) stepwise change of temperature or oxygen partial pressure of the gaseous environment of a ceramic sample, and measurement of the relaxation of electrical conductivity or oxygen content, ii) oxygen permeation through a gas dense oxide ceramic pellet from air to argon. The experimental problems and sources of errors, calculation methods of chemical diffusion coefficients and oxide ionic conductivities from these two modes of investigation are discussed. The comparison of relaxation and permeation measurements on 10 oxides of the type A_1−aA′_aM_1−bM′_bO_3−σ (A=La, Pr, Ce; A′=Sr, Ca; M=Mn, Fe; M′=Co, Ni) show advantages of the relaxation method in relation to the experimental performance and possible errors.     

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.