Electron temperature determination in LTE and non-LTE plasmas

A method is presented for calculating electron temperatures (T_e) in dense plasmas, which does not assume equivalence with the excited level distribution temperatures (T_ex). The method involves the upper-level Saha ionization equation at the ionization limit, the limiting weighted population density (N_I/g_I) obtained from measured population densities and the experimentally obtained electron density. Electron temperatures calculated for 0.1-bar hydrogen and 1-atm helium and argon arcs are found to be up to twice as large as excited level distribution temperatures. For subatmospheric argon arcs, the calculated T_e are equivalent to the excitation temperature of the middle levels, but are two to three times smaller than the quoted T_ex for the highest levels. Reasons are discussed for the apparent invisibility of true electron temperatures and for differences between them and the excitation temperatures.     

类氖等电子系列离子基态的双电子复合速率系数研究

使用全相对论组态相互作用方法, 能级-能级细致计算了0.1 E_I ≤ kT_e≤ 10 E_I (E_I是类钠离子基态的第一电离能) 温度范围内类氖离子基态双电子复合(DR)速率系数, 双激发自电离能级考虑了(2s2p)⁷3ln'l', (2s2p)⁷4l4l' 以及(2s2p)⁷4l5l'组态. 对于(2s2p)⁷3ln'l'双激发自电离组态, 轨道角量子数l' >8 的(2s2p)⁷3ln'l'双激发自电离态对双电子复合速率系数的贡献可以忽略不计; (2s2p)⁷3ln'l'双激发自电离组态的高里德堡态对双电子复合速率系数的贡献满足 n'^-3组态-组态外推法, 并且核电荷数越大, 趋于n'^-3标度的n'值越小; 对细致能级计算得到的类氖离子基态的总DR速率系数进行了拟合, 得到类氖离子基态的总DR速率系数随核电荷数 Z和电子温度变化的经验公式, 该拟合公式与细致计算结果的偏差在2%以内, 能较准确的计算任意核电荷数Z的类氖离子在0.1E_I ≤ kT_e ≤ 10E_I电子温度范围的DR速率系数. Burgess-Merts(BM)近似公式不适用于估算低温(kT_e<0.3 E_I)类氖离子的DR速率系数, 在高温(kT_e>2E_I)时, 类氖离子的DR速率系数可以用BM近似公式表示.     

Behavior of mixtures of iodine with anthracene,phenazine and thianthrene

The binary systems I₂-phenazine (I₂P), I₂-anthracene and I₂-thianthrene have been investigated over a wide range of concentrations (0.1 < x_I2 < 1) and over temperatures ranging from 0 to 60°C. EMF measurements were performed in the three systems employing galvanic cells with a silver-ion-conducting solid electrolyte in order to determine the possible compounds and their formation Gibbs energies. Only one compound of stoichiometry I₂P is present in the system I₂phenazine and its formation Gibbs energy can be expressed as follows: Δ_FG⁰(I₂P) = ?20830 + 19.7 T(J mol^?1), 273–333 K. Neither the anthracene nor the thianthrene form compounds or solid solutions in the studied ranges of concentrations and temperatures.     

Annihilation of positrons in aluminium oxide and phase transformations in this compound

Measurements have been made of the angular correlation N(θ) of positron annihilation quanta, the triquanta annihilation intensity I_3γ by the peak-to-peak method, and the average lifetimes of positrons in A1₂O₃. The measured quantities depend on the temperature at which the Al₂O₃ was obtained. It is assumed that there are two conversion centers of ortho -Ps. One is molecular oxygen adsorbed on the oxide surface and the other is the O^? ion which exists in A1₂O₃ obtained at lower temperatures, both on the surface and in the interior of the grains. The temperature ranges have been determined within which the changes in properties of the oxide with respect to the annihilation of positrons, occur slowly as well as those within which the changes occur rapidly. Among these properties are the vanishing of the postulated O^? ions with rise in temperature a probable diffusion of aluminium ions, and the vanishing of vacancies in the lattice structure (I_Ps). From the measurements of the rate characteristics the complete annihilation intensity I_xxx was calculated within the range from 0.34 to 96ns, and also annihilation intensity from para states of positronium I_p.     

Mean-square displacements of metal and boron atoms in crystal lattices of rare-earth hexaborides

The intensities of the I₄₁₀ and I₄₁₁ reflections of nine rare-earth hexaborides MB₆ (M=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) are experimentally studied in the temperature range 4.2–300 K. The mean-square displacements of metal and boron atoms are calculated from the temperature dependences of the intensities I₄₁₀(T) and I₄₁₁(T). The characteristic temperatures of the metal (θ_M) and boron (θ_B) sublattices of rare-earth hexaborides are determined in the Debye approximation. It is found that the characteristic temperatures decrease with an increase in the atomic number of the metal.     

On a new method of causing sensitized luminescence in CaF2:Ce:Mn phosphors

Cathode ray irradiation provides a new method of causing sensitized luminescence in the system CaF₂:Ce:Mn. Energy transfer efficiencies (η = I_Mn/I_total, where I_Mn and I_total are the emission intensity corresponding to the characteristic emission of the Mn²⁺ ions and the total cathodoluminescence, respectively) observed in samples with varying concentrations of Ce and Mn and at different temperatures of excitation indicate a near constancy of these values up to 100°C. This result and the result that transfer efficiencies for cathode ray excitation are greater than those for optical excitation are also explained.     

Infrared and Raman spectra and vibrational assignments of diiodomethane and its deuterated analogs

The infrared (from 4000 to 100 cm^?1) and Raman spectra of CH₂I₂ and CD₂I₂ have been recorded in the liquid and gaseous phases. Assignments have been made for all observed bands and, in the case of CH₂I₂, compared with those previously reported. Some bands appearing in the CD₂I₂ spectrum have been attributed to the presence of CHDI₂. The wavenumbers of the fundamental bands of CHDI₂ have been calculated from those of CH₂I₂ and CD₂I₂ using Brodersen and Langseth's rule, and compared with those observed in the CD₂I₂ spectrum.     

Electrical and photo-electrical properties of a chalcopyrite semiconductor AgInSe2

In this paper we report the electrical and photoelectrical properties of AgInSe₂. Nyquist plots for AgInSe₂, obtained at different temperatures, are perfect arcs of a semicircle with their centres lying below the abscissa at an angleα. Finite values ofα (the distribution parameter) clearly indicate a multirelaxation behaviour. Transient and steady state photoconductivity of AgInSe₂ has been studied at different temperatures and illumination levels. The lnI _ph vs lnF curves at different temperatures follow the empirical relation:I _ph ∝F ^γ. Values of γ are close to 0.5 at all the temperatures, suggesting a bimolecular recombination. Decay of the photocurrent, when the illumination is switched off, shows that during decay, photocurrent has two components, i.e. a fast decay in the beginning and a slow decay thereafter. Decay time constant for slow decay process decreases with increasing temperature, suggesting that recombination is a thermally activated process in the temperature range studied.     

低温下Er3+/Yb3+共掺碲酸盐玻璃的发光特性研究

研究了在8—300K温度范围中, Er³⁺/Yb³⁺共掺碲酸盐玻璃的15μm荧光光谱、上转换光谱与温度的关系. Er³⁺:⁴I_13/2→⁴I_15/2跃迁发射光谱通过高斯拟合和简单的四能级系统估计了Er³⁺离子⁴I_13/2和⁴ 关键词： 碲酸盐玻璃 上转换发光 低温 荧光特性     

Critical currents in polycrystalline thin films of high-T c superconductors

Summary It is shown that the behaviour of the temperature dependence of the critical current in polycrystalline thin films of high-T _c superconductors depends crucially on the assumption made concerning the nature of the intergranular material. The usual assumption of a superconductor-insulator-superconductor (=SIS) ?sandwich? between each grain leads to a crossover fromI _c∼(1−T/T _c) toI _c∼(1−T/T _c)^3/2, for temperatures nearT _c (whereI _c is the critical current,T the absolute temperature, andT _c the superconducting transition temperature). Instead, for a superconductor-normal metal-superconductor (=SNS) sandwich the dependenceI _c∼(1−T/T _c)² is found for all temperatures. Consideration is given to the effect of self-magnetic field on the analysis. The comparison between expressions for continuous and granular systems is extended. Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction.     

The effect of post-metal annealing on the electrical performance and stability of two-step-annealed solution-processed In2O3 thin film transistors

In this work, solution-processed indium oxide (In₂O₃) thin film transistors (TFTs) were fabricated by a two-step annealing method. The influence of post-metal annealing (PMA) temperatures on the electrical performance and stability is studied. With the increase of PMA temperatures, the on-state current and off-state current (I_on/I_off) ratio is improved and the sub-threshold swing (SS) decreased. Moreover, the stability of In₂O₃ TFTs is also improved. In all, In₂O₃ TFT with post-metal annealing temperature of 350°С exhibits the best performance (a threshold voltage of 4.75 V, a mobility of 13.8 cm²/V, an I_on/I_off ratio of 1.8 × 10⁶, and a SS of 0.76 V/decade). Meanwhile, the stability under temperature stress (TBS) and positive bias stress (PBS) also show a good improvement. It shows that the PMA treatment can effectively suppress the interface trap and bulk trap and result in an obviously improvement of the In₂O₃ TFTs performance.     

Electronic phase separation in TmBa2Cu4O8

The NQR spectra of Cu(2) in the superconductor TmBa₂Cu₄O₈ are studied at temperatures from 300 to 4.2 K. In analyzing the spectra it is assumed that the NQR line of each isotope contains two Gaussian components — narrow (n) and broad (b). It is discovered that the NQR frequencies have a minimum at the temperature T*=150 K. The frequencies of the components of the spectrum are close at temperatures from T* to 4.2 K and differ substantially at temperatures T>T*. Both components are broadened as the temperature decreases, but this broadening occurs especially rapidly at temperatures T<T*. The relative intensity of the narrow component I _n/(I _n+I _b) equals 1/6 for T=225−160 K, increases abruptly at T=T*, and remains constant (1/3) at temperatures T from 125 to 4.2 K. Analysis of the experimental data showed that the anomalous temperature dependences of the Cu(2) NQR spectra could be due to electronic phase separation (stratification) in the CuO₂ planes at temperatures T⩽T*. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 214–219 (10 February 1996)     

Microstructures, optical and electrical properties of In-doped ZnO thin films prepared by sol-gel method

ZnO and indium-doped ZnO (I_xZO) thin films were prepared on silica-glass substrates by the sol-gel method. The thin films were crystallized at 600 °C and 700 °C for 1 h in 6.9 × 10⁻¹ Torr under pure O₂ atmosphere. The analyzed results were compared to investigate the structural characteristics and optical properties. The surface morphology of the I_xZO films was different from that of the ZnO films, and showed a thin overlay structure. In addition, the crystallization of I_xZO film was depleted at higher crystallized temperatures. From XRD analysis, the ZnO and I_xZO thin films possessed hexagonal structures. Notably, micro-In₂O₃ phases were observed in the I_xZO thin films using EDS. Both of In₂O₃ phases and the crystallization mechanism not only improved the peeling of structure, but also improved the electrical conductivity of I_xZO thin films. For the PL spectrum, the optical property of the I_xZO film was raised at a higher crystallization temperature. Although the In₂O₃ phases reduced the structural defects of I_xZO thin film, the optical effect of the residual In³⁺ was not enhanced completely at higher crystallized temperatures.     

Laser Fluorescence Method for Detection of 129I and 127I Isotopes of Molecular Iodine with the Use of Kr Laser Radiation (647.1 nm)

The absorption spectra of the ¹²⁷I₂, ¹²⁷I¹²⁹I, and ¹²⁹I₂ isotopes of molecular iodine and the spectra of fluorescence excited by radiation of a Kr laser (λ=647.1 nm) were experimentally studied and calculated. A method for simultaneous determination of the concentration of ¹²⁷I and ¹²⁹I in gas mixtures (in particular, atmospheric air) is proposed.     

Dissociation of molecular iodine in RF discharge for oxygen-iodine lasers

The dissociation of molecular iodine in 40 MHz-RF discharge was studied experimentally. This generation of atomic iodine is aimed at use in oxygen-iodine lasers. The discharge was ignited in a mixture of I₂ + buffer gas fast-flowing through the cylindrical chamber and the discharge products were injected into a supersonic flow of nitrogen. The atomic iodine number density was measured in a low-pressure cavity after mixing with nitrogen and the dissociation fraction was calculated related to the input I₂ flow rate. The dissociation fraction of 46.2% was achieved at 0.22 mmol/s of I₂ and 7 mmol/s of Ar and RF power of 500 W. Argon and helium were used as a buffer gas; discharge stability and dissociation efficiency were better with argon. At the I₂ flow rate corresponding to the operation of a 1 kW chemical oxygen-iodine laser, the dissociation fraction was about 20%. The dissociation efficiency (the fraction of absorbed energy used for the dissociation) significantly decreased with increasing in the specific energy. At a reasonable I₂ flow rate (0.32 mmol/s), the maximum achieved efficiency was 8.5% and the corresponding energy cost was 8.9 eV per dissociating of one I₂ molecule. The input energy of more than 3 kJ per 1 mmol of I₂ is needed for dissociating at least 50% of I₂. The obtained dependencies on the gas flow rates infer a good chance for scaling-up of the tested RF discharge generator for the intended application.     

Excitation-autoionization cross sections and rate coefficients for Ga-like ions

Detailed level-by-level calculations of cross sections and rate coefficients for electron impact direct and indirect ionization of ions belonging to the GaI isoelectronic sequence (ground 3d ¹⁰4s ²4p) have been performed. The cross sections are presented in the energy range near the threshold for the five ions Kr⁵⁺, Mo¹¹⁺, Xe²³⁺, Pr²⁸⁺ and Dy³⁵⁺. The rate coefficients are given for ions from Kr⁵⁺ to U⁶¹⁺ in the GaI sequence at seven electron temperatures (kT _e = 0.1E _I , 0.3E _I , 0.5E _I , 0.7E _I ,E _I , 2E _I and 10E _I , where E _I is the first ionization energy). The calculations include the contribution of direct ionization (DI) calculated using the Lotz formula approximation and the contributions of excitation-autoionization (EA) computed in the framework of the distorted wave (DW) approximation for the 4s-nl, 3d-nl and 3p-nl resonant inner-shell excitations. The ionization enhancement due to the EA channels is presented as a function of Z along the GaI isoelectronic sequence. The present results show the great importance of the EA processes; an ionization enhancement factor of up to 10 is predicted for instance for La²⁶⁺ (Z = 57) at electron temperature of coronal equilibrium maximum abundance.     

从X射线的衍射强度测定晶体的德拜特征温度

本文详尽地讨论了从X射线衍射强度测定均匀的且各向同性的晶体的德拜特征温度的方法。本方法指明:如将所有的计算强度对观察强度之比的自然对数In(I_calc/I_obs)对sin²θ/λ²标绘,则应该得到一条直线,这条直线的斜率为2B。在德拜的比热理论中,B可表示为(6h²T/MkΘ_D²){φ(x)+(x/4)},其中x=Θ_D/T。如使G=BMkT/6h²,则φ(x)+x/4=Gx²,既然已求得了B值,则这个方程式中的G是一个可量度的数。求解这个方程式可用图解法来进行。使y₁=Gx²,而y₂=φ(x)+x/4,则从这两个方程式的标绘可以得到两条曲线,这两条曲线的交点就是所要测定的x值,由x值可确定在测定温度时的特征温度。必须指出,由于Θ_D本身是温度的一个函数,本方法提供了一个在所需要的温度测定德拜特征温度的可能性。 关键词：     

Stimulated raman scattering of fuel droplets

The strong stimulated Raman scattering (SRS) from diesel fuel droplets has the potential of providing the relative concentration of multicomponent fuel and the absolute size of individual droplets. The morphology-dependent resonances (MDRs) of a sphere cause the droplet to act as an optical resonator which greatly lowers the SRS threshold. The number density, quality factor, and frequency shift of several MDRs are calculated as a function of the ratio of the index of refraction of the liquid and the surrounding gas, which approaches unity at the thermodynamic critical condition for the fuel spray. The SRS spectra of monodispersed droplets of toluene, pentane, Exxon-Aromatic-150, and Mobil D-2 are presented. The exponential growth region of the SRS intensity I _1S as a function of the input laser intensity I _input is investigated for the toluene carbon ring breathing mode v ₂ and the pentane C-H stretching region. The I _1S ratio of toluene and pentane is measured as a function of the ratio of the toluene and pentane concentration for monodispersed droplets. The reduced fluctuation in I _1S when I _input is changed from multimode to single-mode is displayed as a histogram of the I _1S of the v ₂ mode of toluene droplets.     

Photoluminescence observations of hydrogen incorporation and outdiffusion in ZnO thin films

ZnO thin films were deposited with the addition of H₂ to the reaction gas using the atmospheric-pressure metal organic chemical vapor deposition method. The incorporation and outdiffusion of hydrogen in ZnO films were investigated by comparing the intensity of the hydrogen-related bound-exciton peak (I₄: 3.363 eV) in the photoluminescence spectrum. The intensity of I₄ peak was found to be the strongest in the ZnO film deposited at 680 °C with H₂ present. However, for the ZnO films prepared at the same temperature 680 °C but without H₂ present and at the higher temperature of 900 °C with H₂ present, respectively, the I₄ peak was just a minor shoulder of another bound-exciton peak (I₈: 3.359 eV). The intensity of I₄ peak in the ZnO films deposited with H₂ present was found to decrease with the increasing of annealing temperature. These results suggest that it is difficult for hydrogen to incorporate into ZnO thin films grown at high temperatures even in the hydrogen-present ambient.     

Disorder and the ground state of bis(tetrathiatetracene) triodide TTT2I3

The low temperature ground state of TTT₂I₃ with varying amounts of iodide chain disorder has been studied using specific heat and infrared and far infrared reflectance and absorbance. Our results support the model of TTT₂I₃ as an organic conductor at room temperature which undergoes a metal to insulator transition near 50 K. At low temperatures we find a semiconducting gap of 80 cm^?1 independent of disorder.