A study of the nonlinear refractive index in amorphous Ge–As–S layers and nanocomposites with gold nanoparticles

Nonlinear refractive indices of simple and composite chalcogenide glasses with gold nanoparticles are measured by the Z-scan method using a femtosecond Ti:sapphire laser with a central wavelength of 800 nm and a pulse duration of 40 fs. It is shown that introduction of nanoparticles into thin layers of amorphous GeS₂, As₃₀Ge₂₀S₅₀, and As₃Ge₃₅S₆₂ leads to a decrease in the total nonlinear refractive index due to additional absorption of femtosecond laser radiation without efficient excitation of localized plasmons outside the resonance region. For example, the nonlinear refractive index decreases with addition of gold nanoparticles from 16.1 × 10^–12 to 13.0 × 10^–12 cm²/W for GeS₂, from 3.9 × 10^–12 to 3.2 × 10^–12 cm²/W for As₃₀Ge₂₀S₅₀, and from 5.8 × 10^–12 to 4.7 × 10^–12 cm²/W for As₃Ge₃₅S₆₂.     

A study of hand vibration on chipping and grinding operators,part III: Power levels into the hands of operators of pneumatic tools used in chipping and grinding operations

This paper presents a method for calculating power transmitted to the hands of operators who use vibrating hand tools. Results that relate to a comprehensive multidisciplined NIOSH field study of several hundred chipper and grinder workers who used pneumatic hand tools are presented. The results of this study indicated that the power in the frequency range of 6·3 Hz to 1000 Hz transmitted to the hand ranged from 1·08 × 10³ to 7·23 × 10³ J/s for the chisel and from 8·52 × 10^?1 to 1·57 × 10² J/s for the handle of chipping hammers. For pneumatic grinders the power transmitted to the hands of the tool operators was in the range of 6·58 × 10^?3 to 2·35 × 10^?3 J/s over the same frequency range.     

Self-luminescence of several fluorite-structure halides doped with curium or berkelium

The self-luminescence emission spectra of several fluorite-structure halides doped with 0.1 cation % ²⁴⁴Cm or ²⁴⁹Bk were measured in the range 14 × 10⁵ to 50 × 10⁵ m^-1 (200–700 nm) between 295 and 600 K. The hosts studied included CaF₂, SrF₂, BaF₂, and SrCl₂ (for Cm) and BaF₂ and SrCl₂ (for Bk). The room-temperature spectra of the Cm-doped samples all have relatively sharp peaks at approximately 16.5 × 10⁵ m^-1 and broad, asymmetric bands with maxima near 35 × 10⁵ m^-1 (fluorides) or 28 × 10⁵ m^-1 (SrCl₂). The sharp peaks are attributed to the Cm dopant and are stable to at least 600 K, while the broad bands appear to be associated with host anion centers and disappear on sample heating. The room-temperature spectrum of Bk-doped BaF₂ also displays an anion- related band at 35 × 10⁵ m^-1, while that of Bk-doped SrCl₂ has both an anion band at 28 × 10⁵ m^-1 and a peak at 19 × 10⁵ m^-1 (believed to be an additional host effect). The luminescence intensity of all samples decreased with room-temperature storage, but could be partially restored by annealing.     

MW-ECR PE-UMS等离子体特性及对Zr-N薄膜结构性能的影响

采用静电探针技术对微波电子回旋共振(MW-ECR) 等离子体进行了诊断,利用等离子体增强 非平衡磁控溅射(PE-UMS)法在常温下制备了Zr-N薄膜, 通过EPMA，XRD，显微硬度对膜的 结构和性能进行评价.实验结果表明，随氮气流量增加，总的等离子体密度从807×10⁹c m^-3增加到831×10⁹cm^-3然后逐渐减小为752×10 ⁹cm^-3；而N₂⁺密度则从312×10^{8< /sup>cm-3线性递增到335×109cm-3；电子温度变化 不大.对薄膜而言，随N₂+密度增大，样品中氮含量增加，而晶粒逐 渐变小，当样品中N/ Zr原子比达到14时，薄膜中出现亚稳态的Zr₃N₄相以及非晶相， 在更高氮流量下，整 个薄膜转变为非晶态.与此相应，薄膜硬度由最初的225GPa增大到2678GPa 然后逐渐减 小到1982GPa. 关键词： 氮化锆薄膜 ECR等离子体 磁控溅射 诊断}     

Magnetization,AC susceptibility and microwave absorption in Tb and Gd70Tb30

Measurements of magnetization, ac susceptibility and microwave absorption at 9.5 and 35 GHz, have been carried out with single crystals of Tb and Gd₇₀Tb₃₀. The critical temperatures for Tb were in agreement with previous published results. The Curie Temperature for Gd₇₀Tb₃₀ was measured to be (275 ± 2) K. Anisotropy constants have been derived from the microwave measurements. The value of K₂ at 0 K is estimated to 8.8 × 10⁸ erg cm^-3 (Tb) and 1.3 × 10⁸ erg cm^-3 (Gd₇₀Tb₃₀). At 77 K, the value of K₆ is estimated to be 6 × 10⁴ erg cm^-3 (Gd₇₀Tb₃₀.     

Phase portrait ofSU(5) model. II intermediate phasesSU(3)×[U(1)]2 and [SU(2)]2×[U(1)]2

The effective potential of the scalar field in theSU(5) model has extrema with symmetry:SU(5),SU(4)×U(1),SU(3)×SU(2)×U(1),SU(3)×[U(1)]², [SU(2)]²×[U(1)]². In our recent paper it was shown that theSU(4)×U(1) phase as well asSU(3)×SU(2)×U(1) phase were stable at the nonzero temperature in a vast region of parameters. In the present paper it is found that the [SU(2)]²×[U(1)]² symmetric vacuum is unstable and theSU(3)×[U(1)]² symmetric vacuum can be metastable in the certain interval of the temperature. Domains of the three phases:SU(4)×U(1),SU(3)×SU(2)×U(1),SU(3)×[U(1)]²-could co-exist in the early. Universe.     

Observation of pair absorption in calcium

Pair absorption has been observed in calcium using broad band absorption. The absorption peaks at the sum energy of the (4s4p) ¹P° and (4s3d) ¹D atomic states. A cross section of 1.3 × 10^-22 (P/A) cm² is measured corresponding to a reduced absorption coefficient of 1.3 × 10^-35 cm⁵. An error in earlier calculations predicting the reduced absorption coefficient for pair absorption in barium is noted. Simple scaling laws, our experimental results, and the assumption that the barium process is dominated by the resonant dipole-dipole interaction are used to deduce an upper limit for the calcium (4s3d) ¹D→(4s4p) ¹P° oscillator strength of 6.5 × 10^-4.     

Detective quantum efficiency,modulation transfer function and energy resolution comparison between CdTe and silicon sensors bump‐bonded to XPAD3S

XPAD3S is a single‐photon‐counting chip developed in collaboration by SOLEIL Synchrotron, the Institut Louis Néel and the Centre de Physique de Particules de Marseille. The circuit, designed in the 0.25 µm IBM technology, contains 9600 square pixels with 130 µm side giving a total size of 1 cm × 1.5 cm. The main features of each pixel are: single threshold adjustable from 4.5 keV up to 35 keV, 2 ms frame rate, 10⁷ photons s^?1 mm^?2 maximum local count rate, and a 12‐bit internal counter with overflow allowing a full 27‐bit dynamic range to be reached. The XPAD3S was hybridized using the flip‐chip technology with both a 500 µm silicon sensor and a 700 µm CdTe sensor with Schottky contacts. Imaging performances of both detectors were evaluated using X‐rays from 6 keV up to 35 keV. The detective quantum efficiency at zero line‐pairs mm^?1 for a silicon sensor follows the absorption law whereas for CdTe a strong deficit at low photon energy, produced by an inefficient entrance layer, is measured. The modulation transfer function was evaluated and it was shown that both detectors present an ideal modulation transfer function at 26 keV, limited only by the pixel size. The influence of the Cd and Te K‐edges of the CdTe sensor was measured and simulated, establishing that fluorescence photons reduce the contrast transfer at the Nyquist frequency from 60% to 40% which remains acceptable. The energy resolution was evaluated at 6% with silicon using 16 keV X‐rays, and 8% with CdTe using 35 keV X‐rays. A 7 cm × 12 cm XPAD3 imager, built with eight silicon modules (seven circuits per module) tiled together, was successfully used for X‐ray diffraction experiments. A first result recently obtained with a new 2 cm × 3 cm CdTe imager is also presented.     

Boson peak measurements in neutron-irradiated quartz crystals

We have measured the low-frequency Raman scattering in neutron-irradiated quartz crystals with four different irradiation doses from 4.7×10¹⁹ n/cm² to 1×10²⁰ n/cm² and for 2 different crystallographic directions. For the used doses the range of density change of the investigated samples was 12% (the maximum change during amorphization is 14%) and the amorphous fraction varied from 35% to 100%. The same measurement was done in neutron-irradiated amorphous silica with a maximal dose 2×10²⁰ n/cm². In all cases we observed the boson peak in the Raman spectra. The position of the peak, at 67±3 cm^-1, was found to be the same for all the investigated samples independent of the dose. The shape of the peak for doses 6.8× 10¹⁹ n/cm² and higher was also found to be the same for 5 investigated samples (including irradiated vitreous silica). We found that the position of the boson peak in neutron-irradiated quartz crystals and vitreous silica corresponds to the Ioffe-Regel crossover frequency for phonons. The origin of the boson peak in neutron-irradiated quartz and vitreous silica can be attributed to local soft optic modes, which are analogous to the soft optic mode that drives the α–β transition in quartz.     

基于沉淀工艺制作四脚氧化锌纳米材料场致发射阴极的研究

采用沉淀法制备四脚氧化锌纳米材料场致发射阴极,将阴极和荧光屏封装起来抽真空并对屏施加电压,测试阴极的发射电流和荧光屏的发光亮度.利用沉淀法制备出面积为(13×15) cm²的阴极,测试结果表明,硅酸钾体积百分比在50×10^-3—83×10^-3范围,硝酸钡浓度在50×10^-4—77×10^-4 M范围,四脚氧化锌的浓度在82×10^-4—12×10^{-3关键词： 场致发射 沉淀法 显示屏亮度}     

The high pressure structures and the phase transitions of K2[Pt(CN)4]Br0.3·3H2O

The lattice constants of KCP were determined by single crystla X-ray diffraction experiments up to 3 × 10⁹Pa. The pressure dependence of the compressibilities is anomalous around 7 × 10⁸Pa and 2 × 10⁹Pa. The platinum chains are shortened abruptly at 7 × 10⁸ Pa, where the compressibility perpendicular to the platinum chain is normal. The other anomaly around 2 × 10⁹Pa was found in the compression along the direction perpendicular to the platinum chain. The crystal structure analyses showed that the pressure-induced displacement of a water molecule is coupled with the shortening of the Pt chains observed at 7 × 10⁸Pa. The other anomaly at 2 × 10⁹Pa is associated with the transformation of the molecular structure of the tetracyanoplatinate complex anions.     

约化场强对氮-氧混合气放电等离子体演化特性的影响

采用零维等离子体动力学模型,计算了不同约化场强条件下N₂/O₂放电等离子体的演化特性.结果表明,平均电子能量与约化场强有着近似的线性关系,在约化场强为100 Td时,平均电子能量约为2.6 eV、最大电子能量达35 eV;约化场强是影响电子能量函数分布的主要因素.气体放电过程结束后,振动激发态氮分子的粒子数浓度不再变化,电子激发态的氮分子、原子和氧原子的粒子数浓度达到一峰值后开始降低;放电结束后的氧原子通过复合反应生成臭氧.约化场强升高,由于低能电子减少的影响,振动激发态氮分子的粒子数浓度降低,当约化场强由50 Td增加75 Td,100 Td时,粒子数浓度由3.83×10¹¹ cm^-3降至1.98×10¹¹ cm^-3和1.77×10¹¹ cm^-3,其他粒子浓度则相应增大. 关键词： 等离子体 约化场强 粒子演化 数值模拟     

35Cl N.M.R. relaxation in aqueous sodium perchlorate solutions

The relaxation time, T _1ρ, for ³⁵Cl in perchlorate ion in aqueous solutions is found to be 0·25 s. T _1ρ is insensitive to the presence of most first row transition metals; however, a weak complex with manganous ion is demonstrated, and the perchlorate ion-manganous exchange rate is shown to be between 3 × 10⁴ s^-1 and 3·6 × 10⁷ s^-1. In the absence of manganous ion, the relaxation is dominated by the nuclear electric quadrupole interaction; however, a dipolar contribution is observed with manganous ion present.     

Comparative Study on Three Different Systems of Chemiluminescence Flow‐Injection Determination of Leucogen

Abstract

The effects of three systems on the chemiluminescence (CL) intensity have been studied in this paper, such as leucogen–potassium permanganate–rhodamine B, leucogen–cerium (IV)–rhodamine B, and leucogen–luminol–hydrogen peroxide (called system 1, system 2, and system 3, respectively). The mechanism of these reactions is also discussed. Surfactant (CTMAB) has a remarkably sensitive effect on these systems mentioned above. Therefore, three new flow injection chemiluminescence methods for the determination of leucogen have been established. For system 1, the linear range is 8.0×10^?8 to 4.0×10^?5 g mL^?1, with limits of detection 2×10^?8 g mL^?1; the relative standard deviation is 2.5% (n=11, Cs=4.0×10^?6 g mL^?1). For system 2, the linear range is 1.0×10^?8 to 5.0×10^?6 g mL^?1, with limits of detection 3×10^?9 g mL^?1; the relative standard deviation is 5.1% (n=11, Cs=1.0×10^?6 g mL^?1). For system 3, the linear range is 4.0×10^?8 to 2.0×10^?6 g mL^?1, with limits of detection 1×10^?8 g mL^?1; the relative standard deviation is 1.3% (n=11, Cs=1.0×10^?7 g mL^?1). Compared with the three methods above, system 3 is confirmed as the best method. This method has been applied to the determination of leucogen with satisfactory results.     

On the spontaneous creation of chromomagnetic fields at high temperature

The spontaneous generation of the chromomagnetic field at high temperature is investigated in a lattice formulation of the SU(2) gluodynamics. The procedure of studying this phenomenon is developed. Monte Carlo simulations of the free energy on the lattices 2 × 8³, 2 × 16³, and 4 × 8³ at various temperatures are carried out. The creation of the field is indicated by means of the χ ² analysis of the data set accumulating (5–10) × 10⁶ Monte Carlo configurations. A comparison with the results of other approaches is done. The text was submitted by the authors in English.     

The GaP(001) surface and the adsorption of Cs

GaP(001) cleaned by argon-ion bombardment and annealed at 500°C showed the Ga-stabilized GaP(001)(4 × 2) structure. Only treatment in 10^?5 Torr PH₃ at 500°C gave the P-stabilized GaP(001)(1 × 2) structure. The AES peak ratio $\text{P}\text{Ga}$ is 2 for the (4 × 2) and 3.5 for the (1 × 2) structure. Cs adsorbs with a sticking probability of unity up to 5 × 10¹⁴ Cs atoms cm^?2 and a lower one at higher coverages. The photoemission measured with uv light of 3660 Å showed a maximum at the coverage of 5 × 10¹⁴ atoms cm^?2. Cs adsorbs amorphously at room temperature, but heat treatment gives ordered structures, which are thought to be reconstructed GaP(001) structures induced by Cs. The LEED patterns showed the GaP(001)(1 × 2) Cs structure formed at 180°C for 10 h with a Cs coverage of 5 × 10¹⁴ atoms cm^?2, the GaP(001)(1 × 4) Cs formed at 210°C for 10 hours with a Cs coverage of 2.7 × 10¹⁴ atoms cm^?2, the GaP(001)(7 × 1) and the high temperature GaP(001)(1 × 4), the latter two with very low Cs content. Desorption measurements show three stability regions: (a) between 25–150°C for coverages greater than 5 × 10¹⁴ atoms cm^?2, and an activation energy of 1.2 eV; (b) between 180–200°C with a coverage of 5 × 10¹⁴ atoms cm^?2, and an activation energy of 1.8 eV; (c) between 210–400°C with a coverage of 2.7 × 10¹⁴ atoms cm^?2, and an activation energy of 2.5 eV.     

Interaction of CdSe/ZnS core-shell semiconductor nanocrystals in solid thin films

The optical properties of CdSe/ZnS semiconductor nanocrystals with the core-shell structure are studied upon visible-laser excitation in a wide range of flux densities. It is demonstrated that the dimensional quantization effect is preserved in the films with a limiting high concentration of nanocrystals. A strong bathochromic shift of the absorption and luminescence peaks relative to the peak positions in the corresponding spectra of nanocrystals in films with a relatively low concentration of nanocrystals and solutions is caused by a high concentration of nanocrystals and the dipole moment related to the asymmetry of the nanoparticles. The shift is varied from 35 to 50 nm depending on the film thickness. The luminescence spectra of the films remain unchanged upon an increase in the laser intensity to 1 × 10⁶ W/cm². The laser action on the nanoparticle films is studied at intensities (5 × 10⁶?1 × 10⁹ W/cm²) higher than the damage threshold.     

The lowest metal-to-bipyridine charge-transfer excited state of [Cr(2,2′-bipyridine)(CO)4]

The DV-Xα molecular-orbital calculations have been carried out on [Crbpy(CO)₄](bpy,2,2′-bipyridine) and its electron attachment and detachment products. The one-electron attachment of [Crbpy(CO)₄] yields a complex of bipyridine anion radical, while the one-electron detachment results in ionization of the central metal atom. The lowest excited state of [Crbpy(CO)₄] is the metal-to-ligand charge-transfer (MLCT) excited state which consists of the bipyridine anion radical and the central metal ionized. The transition-state calculation predicts the lowest MLCT excited states at around 23～30×10³ cm^?1 and the lowest bipyridine (π,π^*) excitations at 36×10³ cm^?1 and 42～45×10³ cm^?1. The calculation also concludes that the MLCT excitation induces a counter migration of the other electrons not directly involved in the charge-transfer excitation. The configuration-interaction calculations predict the lowest MLCT excited singlet states at around 21～35×10³ cm^?1 and the lowest bipyridine (π, π^*) excited singlet states at 42～62×10³ cm^?1, while the emissive lowest MLCT triplet state is at 17×10³ cm^?1. The transition moments evaluated with the transition-state wavefunctions can reproduce qualitatively the observed absorption spectral profile. The intensity of the MLCT transitions is obtained from the allowed (π, π^*) transitions of coordinated bipyridine but is not due to the intrinsic transition moments of MLCT excitations.     

Development of an Optode for Detection of Trace Amounts of Hg2+ in Different Real Samples Based on Immobilization of Novel Tetradentate Schiff Bases Bearing Two Thiol Groups in PVC Membrane

A very sensitive and reversible optical chemical sensor based on a novel tetradentate Schiff base namely N.N^/bis(2-aminothiophenol)benzene-1,2-dicarboxaldehyde (ATBD) immobilized within a plasticized PVC film for Hg²⁺ determination is described. At optimum conditions (i.e. pH 6.0), the proposed sensor displayed a linear response to Hg²⁺ over 1.0?×?10^?10 ? 1.0?×?10^?2 mol L^?1 with a limit of detection of 7.23?×?10^?11 mol L^?1 (0.0145 μgL^?1). Moreover, the results revealed that, under batch condition, the sensor is fully reversible within a response time?~?35 s. In addition to its high stability and reproducibility, the sensor showed good selectivity towards Hg²⁺ ion with respect to common metal cations. The sensor was successfully applied for determination of Hg²⁺ ion in some real samples, including hair, urine and well water samples. The results were in good correlation with the data obtained using cold vapor atomic absorption spectrometry.