不同溶剂中PAH荧光产出对激发波长的依赖

用日立F 45 0 0型荧光分光光度计就石油产品中两种主要的多环芳香族碳氢化合物 (PAH) ,即菲和萘在两种不溶剂即水和二氯甲烷中的荧光产出对激发光波长的依赖进行了研究。结果表明 ,样品溶液的荧光转换效率与激发光波长有十分密切的关系 ,而这种关系又强烈依赖于所用溶剂     

Calibration of the R ruby fluorescence lines in the pressure range [0-1 GPa] and the temperature range [250-300 K]

Abstract

The pressure range [&1 GPa] and the temperature range [250–300 K] are commonly used in many science fields like biology, agro-chemistry, pharmacology, or geology. In this paper, the calibration of the ruby R lines of fluorescence is performed in these pressure and temperature ranges, using the melting curve of pure water. The linear shifts of ruby peaks are equal to ?0.140cm^?1/K and ?0.768cm^?1/kbar with R₁, and to ?0.137cm^?1/K and ?0.779 cm^?1/kbar with R₂. The accuracy of pressure measurements can be as good as ± 10MPa if the temperature is known with ±0.5 K. Such a precision is achieved if: (1) the position of each peak is determined using an inversion method; (2) daily shifts of the spectrometer are corrected before each acquisition; (3) peak positions of each ruby are known at ambient pressure and temperature.     

Dependence of photoluminescence from a-Si nanoparticles on the annealing time and exciting wavelength

Thin films of SiO_x having thickness of 0.2 μm and oxygen content x=1.5 or 1.7 are prepared by thermal evaporation of SiO in vacuum. Then some samples are furnace annealed for various times (in the range ) at 770 and 970 K and some others are rapid thermal annealed at 970 K for 30 and 60 s. Photoluminescence (PL) measurements are carried out at room temperature using the 442 nm line of a He-Cd laser and the 488 nm of an Ar laser for excitation. The effect of the annealing conditions and wavelength of the exciting light on the shape of the PL from these films is explored. The deconvolution of the PL spectra measured with the 442 nm line from samples annealed at 770 K for reveals two distinct PL bands peaked at around 2.3 and 2.5 eV, which do not shift appreciably with increasing annealing time. In addition, at longer annealing times, a weak third band is resolved centred in the range 2.0-2.1 eV. It exists in the spectra of all samples annealed at 970 K being more prominent in the samples with x=1.5. The intensity of this band shows different dependences on the annealing time in the films with different initial composition. The results obtained are discussed in terms of radiative recombination via defect states in the SiO_x matrix (the 2.5 eV band) or at the a-Si-SiO_x interface (the 2.3 eV band). The band centred in the 2.0-2.1 eV range is related to recombination in amorphous silicon nanoparticles grown upon annealing.     

Hysteresis of ruby fluorescent line by pressure and annealing effect

Abstract

Accuracy of hydrostatic pressure measurement in a diamond-anvil cell (DAC) depends on the reproducibility of ruby RI fluorescent measurement. The larger scatter in R, fluorescent wavelength shift than the reproducibility of spectroscopic measurement was observed among appropriately mirror-finished ruby plates before setting up in DAC. The characteristics of the scatter changed after loading DAC up to pressure over hydrostatic limit. They vanished by annealing the ruby plates. These phenomena are presumably due to the appearance and disappearance of the residual stress in the ruby crystal. Such hysteresis of ruby fluorescent wavelength shift by pressure and its annealing effect are discussed.     

Dependence of the pressure pulse generated in an opticoacoustical receiver on the intensity of the exciting laser pulse

Calculations of the time form and amplitude of the acoustic signal generated in an absorbing gas that fills the cuvette of an opticoacoustical receiver in the case of a nonlinear nonsteady interaction with a single laser pulse are performed. Expressions relating the parameters of the acoustic signal with the characteristics of the laser pulse are derived, and an expression is proposed for the parameter characterizing the nonlinearity of the absorption of the given gas.     

Effect of pressure and temperature on the wavelength shift of the fluorescence line of SrB 4O 7:Sm 2+ scale

The pressure shift of ⁷D ₀?⁵F ₀ fluorescence line of SrB ₄O ₇:Sm ²⁺ has been recalibrated at high temperature and high pressure, respectively. Combined with the high pressure and high-temperature experimental data given by previous study, a quantitative analysis of the temperature effect on pressure shift of the ⁷D ₀?⁵F ₀ fluorescence line has been performed. The results show that there is an overall negligible coupling effect of temperature and pressure on the wavelength shift of the ⁷D ₀?⁵F ₀ fluorescence line below 770 K and 35 GPa. But above 770 K, the temperature effect on pressure shift could not be ignored at least in a relatively high pressure range. A proposed calibration relation is recommended to predict more accurate pressures in high pressure and high-temperature experiments with SrB ₄O ₇:Sm ²⁺ as the pressure scale.     

Comparison of the Raman pressure shift and the Raman temperature shift of benzene and diamond with the ruby soale

Abstract

In order to serve as substitute for the pressure ruby scale at high temperature, the breathing mode of bemsens (990 cm^?1) and the first order Raman mode of diamond (1333 cm^?1) have been studied as a function of pressure and temperature in the range of 0–15 GPa and 25–400°C. The diamond and bensene Raman frequency shifts are shoft to be of valuable use as a pressure scale at high temperature. A further advantage of bensene is to remain a suitable pressure transmitting medium up to 350°C and 15 GP.     

Dependence of certain ruby laser characteristics on the distance between interferometer mirrors

The authors have made an experimental study of the time to onset of generation and pulsation frequency in a ruby laser at different pumping energies as a function of the distance between interferometer mirrors. The experimental results are compared with theoretical data.     

Dependence of photoluminescence of CdSe/ZnS on excitation wavelength

We have found that the photoluminescence (PL) intensity of CdSe/ZnS nanocrystals placed on a thin film of insulator (GaAsOx/GaAs) depends on excitation wavelength through the interference effects of the excitation light. By employing the multi-reflection/interference calculation, the insulator thickness of the underlying non-uniform patterns can be evaluated by the simple observation of CdSe/ZnS PL with a couple of excitation wavelengths. Moreover, the differences observed for the temporal evolution of CdSe/ZnS PL (blue shifts and degradation) among the excitation wavelengths suggest that the photo-induced changes of chemical composition and surface ligands are responsible for blue shifts and degradation, respectively.     

TDLAS波长调制压力测量法参数优化

使用TDLAS技术进行动态压力测量已经成为压力测量领域的研究热点。波长调制法实验装置较为复杂,需要对多个参数进行设置,选择出最优的预设参数能够取得更好的实验效果,获得更高的测量精度。目前波长调制法的实验参数设置基本凭借个人经验,使用Matlab程序仿真结合波长调制法的TDLAS测量技术,能够对实验中需要进行预设的重要参数进行了分析。通过计算4990cm-1波段和6330cm-1波段附近的多条吸收峰,发现4990.09cm-1波段处的吸收峰更适合作为波长调制法的测量波段。以4990.09cm-1处的吸收峰为研究对象,进行了波长调制法压力测量仿真建模,计算了调制度、调谐频率和调制频率对二次谐波幅值和对称性的影响并深入地分析了影响因素,总结了其变化规律。在综合考虑抗噪性能和测量精度的情况下,选择了调制度为2.5,调谐频率30Hz,调制频率5kHz为最佳实验参数。基于Matlab的仿真模型能够快速计算大量参数点,更加直观地分析出对参数的影响趋势,为实验仪器和预设参数的选择提供依据。     

Effects of high pressure on the Raman and fluorescence emission spectra of two novel 1,3,4-oxadiazole derivatives

The effects of pressure on the fluorescence emission and Raman spectra of 1,4-bis[（4-methyloxyphenyl）-1,3,4-oxadiazolyl]- 2,5-bisheptyloxyphenylene （OXD-2） and on the fluorescence emission spectra of 1,4-bis[（4-methylphenyl）- 1,3,4-oxadiazolyl]phenylene （OXD-1） are investigated using a diamond anvil cell. With the increase of pressure, the intensity of the fluorescence emission increases and reaches maxima at 13GPa for OXD-1 and at 9.6GPa for OXD-2. The effect of pressure on the peak position of the emission shows a similar trend, red shift with the increase of pressure. But at higher pressures, the intensity of emission drops down dramatically. The Raman spectra of OXD-2 indicate that there appears a structural change at ca 3GPa.     

激光波长及脉宽对光学材料抗损伤性能的影响

 基于能带理论,利用激光与光学材料相互作用的理论模型,研究了激光辐照下材料导带自由电子数密度的变化,讨论了材料损伤阈值与激光波长、脉冲宽度、材料禁带宽度之间的关系,数值分析了激光波长和脉冲宽度对损伤阈值的影响。结果表明:当脉宽小于1 ps时,材料损伤阈值随脉宽增大而减小;当脉宽大于1 ps时,材料损伤阈值随脉宽增大而增大;激光波长为10 fs~10 ns,损伤阈值随着波长的减小而减小。     

基于半导体激光器的全光波长转换的理论研究

全光波长转换是全光网络的关键技术之一。利用多模半导体激光器的速率方程,建立了基于半导体激光器的全光波长转换器的理论模型,该模型不仅考虑了注入信号光对激光腔内载流子的消耗,而且考虑了激光腔对注入信号光的放大作用。利用该模型分析了半导体激光器工作电流、注入信号光功率以及码率各参数对波长转换特性的影响。结果对于确定基于半导体激光器的全光波长转换器件的最佳工作条件有一定的参考价值。     

High-pressure optical studies on R-line fluorescence lifetime in Al2O3:V2+

The effect of high hydrostatic pressure (up to 10.3?GPa) at room temperature on fluorescence lifetime τ for R line (²E→⁴A₂ transition) in ruby Al₂O₃:V²⁺ was studied. The performed studies show the linear increase of τ with increasing pressure. At 10.3?GPa, τ is about 1.36 times higher than at ambient pressure. The obtained trend was explained by a model which considered the effect of pressure on τ through an induced change of line position, inter-ionic distance, compressibility, and molecular polarizability. A good agreement between the calculated and experimental values for τ was obtained.     

稳定波长反馈引起的失谐对自由电子激光的影响

利用修改的一维非定态程序,基于美国杰弗逊实验室（JLab）Demo自由电子激光装置的参数,对高功率自由电子激光振荡器稳定波长的反馈系统进行了数值模拟。电子微脉冲为高斯型分布,每个纵向网格中取16个模拟宏电子,不考虑电子束的能散度。结果表明：当无反馈时,腔内光功率和波长都可以在一定范围内稳定;加入反馈后,由于电子束能量的变化所引起的等效失谐对整个系统有着重要的影响,甚至可能导致电子和光场失去相互作用,从而使得装置不能工作。提出应该在光场达到饱和以后再启动稳定波长反馈系统。模拟结果证明,该实施方案是合理有效的,可以避免其对FEL运行的严重影响。     

Study of the effect of swift heavy Ni ion irradiation on ruby single crystal by using the XANES and EXAFS techniques

We have made the XAFS measurements at the Cr–K-edge on natural Indian ruby single crystals (corundum) and its two irradiated samples with fluence 1×10¹² Ni⁶⁺ and 5×10¹² Ni⁶⁺ ions/cm². Irradiated samples show interesting changes in their physical appearance. XANES measurements show progressive decrease in Δ_oct value on increase of Ni fluence in irradiated samples. EXAFS measurements on these samples show decrease in Cr–O distance on increase of Ni fluence. Lowering of Δ_oct value is correlated with the increase of Cr–O distance.     

基于环行腔激光器四波混频型可调谐波长转换的理论研究

建立了完整的基于半导体环行腔激光器四波混频型可调谐波长转换器的宽带理论模型.模型中考虑了半导体光放大器的材料增益谱、载流子的空间分布、光场的纵向空间分布和宽带放大自发发射等关键因素，并通过数值模拟，从理论上研究了这种波长转换器的各种性能与输入信号光功率、注入电流、输出耦合器的耦合比和环行腔激光器激射光波长的关系.理论上所得结论与文献中实验结果符合得很好. 关键词： 半导体环行腔激光器 四波混频 波长转换 放大自发发射     

基于单波长外腔共振和频技术产生波长可调谐589 nm激光及钠原子饱和荧光谱的测量

本文基于新型单波长外腔共振和频技术实现了转换效率高、波长可调谐589 nm激光的输出, 其中基频光波长分别为1583 nm和938 nm, 和频晶体为周期极化铌酸锂. 在1583 nm激光频率被锁定到外部环形腔腔模后, 通过对938 nm激光的频率扫描实现了输出功率4.96 mW, 调谐范围7 GHz的589 nm激光输出, 并采用声光调制器的伺服反馈技术有效提高了输出功率的稳定性. 最后采用该光源对钠原子在348—413 K (75—140 ℃)时D₂线的饱和荧光谱进行了测量. 观察到了多普勒背景下钠D₂a, D₂b以及Crossover的亚多普勒结构, 其均可为589 nm频率的锁定提供参考信号. 关键词： 单波长外腔共振 和频 589 nm 钠原子饱和荧光谱