High temperature reactions between molybdenum and metal halides

Good colour rendering properties, high intensity and efficacy are of vital importance for high-end lighting applications. These requirements can be achieved by high intensity discharge lamps doped with different metal halide additives (metal halide lamps). To improve their reliability, it is very important to understand the different failure processes of the lamps. In this paper, the corrosion reactions between different metal halides and the molybdenum electrical feed-through electrode are discussed. The reactions were studied in the feed-through of real lamps and on model samples too. X-ray photoelectron spectroscopy (XPS) was used to establish the chemical states. In case of the model samples we have also used atomic absorption spectroscopy (AAS) to measure the reaction product amounts. Based on the measurement results we were able to determine the most corrosive metal halide components and to understand the mechanism of the reactions.     

几种照明光源的发光特性比较与分析

本文采用GO-R5000全空间分布光度计测量获得若干种照明光源的配光曲线及三维光强分布图,主要包括白炽灯、节能灯、荧光灯、高压钠灯和发光二极管。通过比较分析了各者的峰值光强、光通量和光效等光学参数的差异,研究结果可为新型照明光源的设计与研发提供实验参考依据。     

Temporal characteristics of emission of working mixtures of a HgBr/HgCl excimer lamp

Results of a study of temporal characteristics of the emission of gas-discharge plasma of atmospheric pressure in multicomponent mixtures (mercury dibromide and dichloride with helium and additions of molecular nitrogen and xenon) of working media of HgBr/HgCl excimer lamps are presented. Gas-discharge plasma was produced and components of the working mixture were excited by high-frequency barrier and surface discharges occurring simultaneously. The repetition rate of the pumping pulse and its duration are 1000 Hz and ～100 ns, respectively. It is found that the amplitude and the length of emission pulses and their trailing edge are modified in HgBr₂: HgCl₂: Xe: He and HgBr₂: HgCl₂: N₂: He mixtures when xenon and molecular nitrogen are added, as compared to a HgBr₂: HgCl₂: He mixture. Regularities observed in temporal characteristics of gas-discharge plasma emission are discussed.     

Pulsed alkali pump light sources for Nd:YAG lasers

Pulsed arc discharges in alkali metal vapours are investigated for use as pump light sources for Nd:YAG lasers. Alkali lamps have a very high radiation efficiency and emit strong lines near the laser pump bands. These absorption bands are fitted by the emission spectrum of sodium and potassium lamps by changing the vapour pressure and input power. The spectral radiation distributions of the lamps are measured by a spectrograph with a gated OMA system. Ray tracing calculations for a laser cavity are used to evaluate the efficiency of the alkali radiation emission for Nd:YAG pumping. The results show that the excitation efficiency of the alkali lamps is twice as high as that of usually used rare gas lamps. For sodium resonance lines the side-on spectral radiance is calculated by a radiation transport model to estimate the pressure and the temperature profile. The results indicate that the alkali vapour lamps could be used as pump light sources with high efficiencies and low heat loading of the laser cavity.     

Acceleration of re-ignition of high pressure mercury discharge lamps using photo-pre-ionization

High Intensity Discharge (HID) lamps are difficult to re-ignite rapidly because of the high pressure of metal vapor at high temperatures. We have succeeded in reducing the re-ignition time of high-pressure mercury lamps by using a pre-ionization step where an excess of electrons are generated by UV laser irradiation into the lamp. The effect of changing the laser focal point of the UV laser in the lamp and the position of an auxiliary electrode were also investigated. The time interval for re-ignition was reduced from 230s to 100s by laser irradiation near to the cathode. The results clearly showed that the effect of accelerating the re-ignition time by the pre-ionization step was determined by the behavior of excess electrons generated during the UV laser irradiation.     

A theory of probes in high-pressure strongly-ionized plasmas

A theory is developed for a probe in a strongly ionized high-pressure plasma. The situation discussed is typical of high-pressure plasmas, where the plasma occupying most of the near-probe layer is in a state of local ionization equilibrium with a common temperature for electrons and heavy particles. The possibility of determining the parameters of the unperturbed plasma by analyzing the probe characteristics on its ion saturation segment, transient segment, and for a floating probe potential is discussed. The calculations are carried out for the example of a strongly ionized xenon plasma at atmospheric pressure. Zh. Tekh. Fiz. 67, 16–20 (December 1997)     

Resonant Coherent Anti-Stokes Raman Scattering Applied to Vapor Phase InI

The metal halide indium iodide (InI) is used as an important additive to mercury discharge lamps. The aim of this paper is to prepare resonant coherent anti-Stokes Raman scattering (RECARS) experiments for measuring concentration and temperature profiles of InI in commercially available metal halide lamps. The spectral positions of possible RECARS lines of InI (double and triple resonances) are calculated up to rotational quantum number J = 280 and vibrational quantum number v = 10. There is evidence for triple resonances leading to strong RECARS signals at J = 174 and J = 231. Dipole transition moments are calculated, which are important input data for the determination of the RECARS spectra. A degenerate-folded BOXCARS setup with a frequency-tripled Nd:YAG laser at 355 nm pumping two dye-laser systems oscillating near 411 nm is utilized to detect RECARS signals of the rovibronic transitions between X:(1)Sigma(+) and A:(3)Pi(0)(0(+)) states of InI. The laser output is attenuated to prevent saturation of the spectra. The tunable dye-laser systems have good beam-pointing stability and a small spectral width (<0.07 cm(-1)). Measured RECARS spectra from a pure InI vapor quartz cell at p = 120 Pa and T = 880 K are compared with theoretical data and good agreement is obtained with respect to the spectral position and RECARS intensity. The scatter signals are achieved with laser-pulse energies of less than 1 μJ. A collision-constant Gamma = 0.0025 cm(-1) describes the line broadening best. The experiments are also performed at a partial InI pressure of 1.12 kPa, a partial Hg pressure of 112 kPa, and a temperature of T = 1073 K and could be interpreted with a broadening constant Gamma = 0.23 cm(-1). Temperature measurements were performed between 900 and 1200 K with an accuracy of 7%. Copyright 2000 Academic Press.     

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研究了无汞等离子体平板荧光光源的气压、气隙、气体组成、光源结构及荧光粉加工对光源发光效率的影响。通过优化,光源的发光效率显著提高。实验结果表明,在450Torr、纯氙气、气体间隙0.7mm、前板玻璃厚为2.8mm,在前板采用60%浓度荧光粉图案印刷获得约20μm厚荧光粉层时,尺寸130mm×90mm的等离子体平板光源的发光效率和亮度超过40lm•w-1、11000cd•m-2,光通量超过500lm。通过优化,获得了较高的亮度和较高的发光效率,讨论了各影响因素引起光源发光效率变化的原因。     

高功率氙灯脉冲放电过程中石英管壁热损伤机理

基于高功率激光装置对脉冲氙灯工程运行可靠性的要求,利用现有的能源模块开展了氙灯放电考核实验。实验结果表明:虽然氙灯运行在安全的能量负载水平,当能源模块单个放电回路的峰值功率超过300MW时,氙灯石英玻璃管壁存在热损伤风险。肉眼观察到管壁损伤后在反射器对侧的灯管内壁出现乳白色沉积层。经扫描电镜和X射线光电子能谱测试分析,证实热损伤形成的乳白色沉积物为二氧化硅。为探究管壁热损伤机制,采用高速摄影观测了氙灯放电等离子体沟道发展过程。图像显示放大器内金属反射器的几何形状对放电沟道的分布产生了显著影响,尤其是在侧灯箱,灯内电弧沟道会靠近反射器一侧集中分布,因此,导致等离子体对灯管的偏烧。当放电峰值功率超过石英热负载极限时,管壁表面二氧化硅材料会被烧蚀至蒸发、气化,并随后沉积在灯管较冷部位。研究结果表明放电回路的放电峰值功率过高、放大器内金属反射器均会对氙灯造成热损伤。     

Eu3+掺杂钛酸钇晶态薄膜的制备与高效红色荧光发射

采用溶胶-凝胶法制备了Eu³⁺掺杂的钛酸钇晶态发光薄膜。通过X射线衍射(XRD)对薄膜的结构和结晶过程进行了分析,利用荧光分光光度计对薄膜的发光性质开展了测试和研究。XRD结果表明,薄膜包含立方相Y_xTi_1-xO_1-0.5x晶粒,该晶粒属立方晶系,Fm3m(225)空间群,晶胞参数a=0.530nm,晶粒尺寸约为17nm。荧光光谱表明,Eu³⁺掺杂的Y_xTi_1-xO_1-0.5x薄膜显示了强的红光发射,其中Eu³⁺的⁵D₀→⁷F₂超灵敏跃迁为最强一组。紫外氙灯、准分子激光器、汞灯等是这种发光薄膜的有效激发源。     

Photosensitive bismuth ions in lead tungstate

Electron paramagnetic resonance (EPR) signals of Bi²⁺ ions have been detected in the EPR spectrum of manganese-, bismuth-, and tin-doped PbWO₄ single-crystals irradiated by xenon and mercury lamps at 100 K. The parameters of the Zeeman, hyperfine, and superhyperfine interactions and the localization of Bi²⁺ ions have been determined.     

Complex Calculations of High-Pressure Discharge Irradiation Characteristics

A wide range of problems related to the determination of the high-pressure irradiation parameters in inert gases and vapors of metals is considered. A new method for calculating equilibrium states of the computed thermodynamic systems is described and its applications to the determination of the plasma composition are disclosed. The method for computing basic discharge characteristics including the determination of material functions of the plasma producing media along with the optical absorption factors' a temperature field in a discharge stabilized by a quartz shell with regard to irradiation energy transfer carried out by bright-line and continous spectra, spectral distributions for the radiant fluxes and discharge irradiation efficiency is presented. Results of multiple calculations to obtain said characteristics in krypton, xenon, vapors of sodium, potassium, rubidium and their mixtures with inert gases are given. Calculated data is a satisfactory agreement with the results of experiments published by various authors.     

Nonequilibrium lighting plasmas

The science of a variety of devices employing nonequilibrium lightning plasmas is reviewed. The devices include the fluorescent lamp, the low-pressure sodium lamp, the neon sign, ultraviolet lamps, glow indicators, and a variety of devices used by spectroscopists, such as the hollow cathode light source. The plasma conditions in representative commercial devices are described. Recent research on the electron gas, the role of heavy particles, spatial and temporal inhomogeneities, and new electrodeless excitation schemes is reviewed. Areas of future activity are expected to be in new applications of high-frequency electronics to commercial devices, new laser-based cidiagnostics of plasma conditions, and more sophisticated models requiring more reliable and extensive rate coefficient data     

Pulsed mercury capillary lamps for dye laser pumping: Spectral measurements

Calibrated spectral measurements of the light emitted by a pulsed high-pressure mercury capillary lamp are presented. These pulsed lamps have been used in a previous work to pump a Rhodamine 6G laser. The measurements presented here show a very high efficiency in the blue and near UV part of the spectrum, suggesting that these lamps represent a very attractive pumping source for dye lasers emitting in the blue. In particular, as an example, a computation has been made for a basic solution of 4-MU yielding a spectral efficiency of 24%.     

Wide-band exciplex halogen lamps operating on inert gas mixtures with chlorine and Freon-12 molecules

The results of analysis of the spectral characteristics of short-wave radiation sources operating on transitions in argon, krypton, and xenon monohalogenides, as well as chlorine molecules, excited by a longitudinal low-pressure glow discharge are considered. Radiation emitted by ArCl^*, KrCl^*, XeCl^*, Cl ₂ ^** , and Cl ₂ ^* molecules in a spectral range of 170–350 nm is optimized using complex working mixtures of Ar-Kr-(Xe)-Cl₂ in the lamps. The average radiation power of the lamps ranges from 1 to 10 W for an efficiency of ≤25%. Optimization of wide-band lamps on transitions in chlorine molecules and the decay products of Freon-12 molecules (CF₂Cl₂) is carried out on mixtures of helium with chlorine and Freon-12 molecules. This makes it possible to develop lamps emitting in a spectral range of 140–270 nm and containing no costly inert gases (Xe or Kr) in their working mixtures. Exciplex halogen lamps with a wide-band emission spectrum in the VUV-UV range can be used in spectrometers as radiation sources in experiments with absorption and in high-energy chemistry, ecology, and medicine.     

Gas Phase Emitter Effect of Thulium within Ceramic Metal Halide Lamps in Dependence on Frequency

The gas phase emitter effect within ceramic metal halide (CMH) lamps reduces the effective work function of the electrode material and, therewith, the electrode temperature. An investigation of the gas phase emitter effect of thulium (Tm) within CMH lamps seeded with Tm iodide (TmI3) is carried out. For this purpose, phase resolved images of the arc attachment and measurements of the electrode temperature, Tm atom and ion densities are performed in dependence on operating frequency by pyrometry and optical emission spectroscopy. Additionally, the influence of a sodium iodide (NaI) admixture is studied. The emitter effect is generated by means of a monolayer of Tm atoms on the electrode surface generated by a Tm ion current within the cathodic phase. It overlaps onto the anodic phase at higher frequencies of some hundreds of hertz. The reason is the finite life time of the monolayer, which is determined by the adsorption energy of Tm on the tungsten surface. Due to the low electric field strength in front of the anode and the mass inertia, the emitter ions and atoms remain in front of the anode. They retard the decay of the monolayer and with it the increase of the work function. Moreover, a comparison of a lamp seeded with TmI3 and sodium iodide (NaI) with a lamp seeded only with TmI3 illustrates a slight reduction of the electrode tip temperature caused by a higher Tm saturation vapour pressure and a higher Tm amount within the lamp filling. The influence of Na appears to be quite low. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ion migration in metal halide perovskite QLEDs and its inhibition

Benefiting from the excellent properties such as high photoluminescence quantum yield (PLQY), wide gamut range, and narrow emission linewidth, as well as low-temperature processability, metal halide perovskite quantum dots (QDs) have attracted wide attention from researchers. Despite tremendous progress has been made during the past several years, the commercialization of perovskite QDs-based LEDs (PeQLEDs) is still plagued by the instability. The ion migration in halide perovskites is recognized as the key factor causing the performance degradation of PeQLEDs. In this review, the elements species of ion migration, the effects of ion migration on device performance and stability, and effective strategies to hinder/mitigate ion migration in PeQLEDs are successively discussed. Finally, the forward insights on the future research are highlighted.     

电流尾部截断对氙灯工作性能影响的实验研究?

脉冲氙灯作为固体激光器的泵浦源,是激光惯性约束聚变装置中重要的光学器件。针对脉冲氙灯的电流尾部开展了截断技术研究,实现了脉冲氙灯电流尾部的截断。研究了电流尾部截断技术对脉冲氙灯放电通道、外壁温度、冲击波产生的振动和钕玻璃荧光输出的影响。研究发现氙灯电流尾部被截断后有效地减弱了等离子体对氙灯内壁的作用,导致氙灯外壁温升降低,从而提高了氙灯寿命。而电流截断产生的冲击波对氙灯并无影响,但过多的截断会降低钕玻璃荧光输出。     

Rare-earth ions in porous matrices

Initially motivated by the commercial need for cheaper and environmentally friendly luminescent materials for application in fluorescent lamps and cathode ray tubes, the search for new matrices for optically active species has penetrated a scope far beyond “classical” solid-state materials. Porous matrices with voids ranging from the nano-to the microscale have become the subject of recent investigations. Crystalline, amorphous, organomorphous, nanosized matrices and matrices, which are amorphous on the atomic level but have a translational superstructure on the microscale (zeolites, sol-gel materials, polymers, nanoparticles and photonic crystals), are addressed. The optical technologies covered in this research range from mercury free discharge lamps, plasma displays, organic and polymeric light emitting diodes, and novel laser materials to biophotonics and the new generation of white emitting AlGaN solid-state light emitting diodes (LEDs). Due to their specific properties (e.g., high quantum yields, narrow line emission), rare-earth ions are indispensable components of these approaches, be it in the nanoscaling zeolites, sol-gel matrices, or as the active component in optically functional polymers. Optical properties of hybrid materials composed of either rare-earth ions as such, their complexes, or nanoparticles in these matrices, with potential application in the fields mentioned, will form the scope of the present report.     

Optical characteristics of barrier discharge plasma based on mixtures of mercury diiodide and dibromide vapors with gases

We analyze the spectral, integrated, and durability characteristics of radiation from atmospheric-pressure gas-discharge plasma based on multicomponent mixtures (mercury diiodide and dibromide with helium and small admixtures of molecular nitrogen and xenon). We produced the gas-discharge plasma and excited the components of the working mixture by a pulsed (pulse repetition rates 500, 2000, and 4000 Hz; pulse duration ～150 ns) barrier discharge. Visible radiation was detected from excimer molecules of mercury monoiodide and monobromide, nitrogen and helium molecules, and helium and mercury atoms. Patterns were found in the variations of optical plasma characteristics with pumping pulse repetition rate and with component and quantitative mixture composition.