Judd-Ofelt光谱分析理论

对Judd-Ofelt光谱分析理论(J-O理论)的发展和应用进行了综述。J-O理论用于分析固体中的稀土离子的吸收、发射光谱,可计算它们的跃迁几率、谱线强度、能级寿命、发射截面等。在J-O理论中考虑J混合后,可使理论和实验结果更好地吻合。采用改进的J-O理论,可较好地对Pr3+光谱进行分析。由TPM方法,可用非极化光透射光谱来分析各向异性晶体的光谱性质,并且对样品的加工无特殊定向要求。对于重叠吸收光谱带,拟合J-O参数时可以近似为一个带进行处理。利用荧光寿命也可对J-O参数进行计算。     

p-PbTe的strip-line透射光谱研究

报道p-PbTe在深低温、强磁场下,不同远红外波长和晶体取向条件下的strip-line透射光谱。观察到一种新的对透射光谱的模式耦合影响。基于对这一复杂的模式耦合问题数学处理的解决,从实验光谱的拟合计算中得到p-PbTe的能带参量,进一步应用6能带的k·p模型解释了能带参量的光谱特性。 关键词：     

基于密度泛函理论下多肽光谱性质研究

多肽类物质在生物医药等领域是一种重要的生物大分子,而紫外-可见吸收光谱和荧光光谱是研究生物分子精细结构的重要手段。采用密度泛函理论（DFT/RI）计算了生长激素释放肽（GHRP-6）和催产素（Oxytocin）两种多肽的结构模型和分子前线轨道;在含时密度泛函理论（TDDFT）的基础上,引入了TDA等近似,建立了多肽类物质的紫外-可见吸收光谱和荧光光谱的理论模型。结果表明,实验测得到GHRP-6的紫外-可见吸收光谱最大吸收波长为279 nm,计算得到的最大吸收波长为282 nm,误差为3 nm,误差百分比约为1%;Oxytocin紫外-可见吸收光谱的实验值为275 nm,计算值为269 nm,误差百分比约为2%。GHRP-6荧光光谱计算值为368 nm,实验值为360 nm,误差百分比约为2%;Oxytocin荧光光谱计算值为305 nm,实验值为312 nm,误差百分比约为2%。GHRP-6产生荧光的发射波长与色氨酸产生的荧光波长范围相近,说明GHRP-6产生荧光的主要贡献为色氨酸残基上的π→π*轨道跃迁,Oxytocin荧光峰位置与酪氨酸产生的荧光波长范围相近,Oxytocin产生荧光的主要贡献为酪氨酸残基上的π→π*轨道跃迁。根据该模型计算得到的光谱与实验结果吻合度较高,表明该模型能够准确计算多肽类物质紫外-可见吸收光谱和荧光光谱,为实验提供可靠的理论依据。     

铜绿微囊藻吸收和散射特性理论模拟

基于奇异衍射近似理论和Kramers-Kronig关系,通过实测铜绿微囊藻的吸收光谱数据和粒径分布估算出铜绿微囊藻折射率的实部和虚部,结合Mie散射理论,计算出铜绿微囊藻的吸收效率光谱、散射效率光谱。对比模拟结果与实验结果发现:该模型估算得到的散射光谱与实验的散射光谱之间误差为10.08%,吸收效率的误差为4.8%。从模拟结果与实测结果来看,均匀球形模型能够较好的重现铜绿微囊藻的吸收和散射特征。     

基于SVM的混合气体红外光谱分析关键技术研究

为了解决海量混合气体光谱数据样本无法获取、混合气体组分气体特征吸收谱线重叠、混合气体组分浓度分布的随意性等问题,将支持向量机用于混合气体红外光谱分析中.提出了光谱数据样本特征选择、数据预处理、SVM校正模型参量优化及层次式混合气体光谱分析结构等关键技术.实验分析了上述4项关键技术对分析结果的影响.实验结果显示,采用关键技术的混合气体组分浓度分析的最大绝对误差为2.93%,最大平均绝对误差为0.73%.     

滤波差分法测量软X射线谱

研究一种测量激光等离子体发射软X射线谱强度的新方法——滤波差分法.介绍了滤波差分 法基本原理,给出了滤波差分对的理论计算结果及实验测量结果,并用此方法获得软X射线 谱的绝对强度,最后对测量光谱强度的误差进行分析和估算. 关键词：     

掺Tm~(3+)氟锆酸盐玻璃2μm发光特性

研究了Tm3+掺杂氟锆酸盐玻璃的2μm发光特性。通过吸收光谱,运用Judd-Ofelt(J-O)理论计算了J-O强度参量tΩ(t=2,4,6)以及Tm3+离子在玻璃中的自发辐射跃迁几率、荧光分支比和辐射跃迁寿命等光谱参数。采用808 nm激光二极管(LD)抽运,获得了Tm3+离子在氟锆酸盐玻璃中的近2μm发射光谱。Tm3+离子在玻璃中的3F4→3H6跃迁峰值波长位于1.82μm处。研究表明,随着Tm3+离子浓度的增加,Tm3+离子之间发生明显的交叉弛豫过程(3H4→3F4,3F4→3H6),从而使得1.82μm处荧光强度明显增强,但当掺杂浓度进一步增加达到一定程度后,基于三能级稀土离子的浓度猝灭效应,该荧光强度明显降低。研究计算了氟锆酸盐玻璃中Tm3+…3F4→3H6跃迁对应的受激发射截面,结果表明,受激发射截面受Tm3+掺杂浓度的影响不大。     

乙二醇和丙三醇的吸收光谱和荧光光谱研究

对乙二醇和丙三醇的紫外吸收光谱和荧光光谱进行了实验研究和理论分析,发现两者的最大吸收波长均位于198 nm,且在适当的紫外波长激励下均能发射出荧光,文章中给出了相应的荧光光谱图,但荧光相对强度和激发波长间似乎没有明显变化规律,其原因有待进一步探索。从乙二醇的一阶导数荧光光谱,得知在210 nm激发下荧光相对强度随时间变化最快,在225 nm激发下的绝大多数时间内变化速率最慢。另外,文章还从量子计算出发,采用一维势阱模型,根据电子从HOMO到LUMO的跃迁,计算出了两者的吸收波长值。比较分析了计算值与实验值之间的误差,考虑到将分子直链化后其键长与实际情况有所差别,结果认为理论计算有一定的参考价值。     

空间目标表面材料光谱双向反射分布函数测量与建模

介绍了双向反射分布函数（BRDF）的绝对测量原理和方法,选用光谱分辨率为3 nm的光谱辐射度计及精度为001°的三维转角系统,搭建了BRDF自动测量平台,对空间目标表面包覆材料在400—2500 nm的光谱BRDF进行了测量.结果表明,BRDF曲线极大值所对应的散射角度一般在镜反射方向左右,其余BRDF值随散射角变化很平缓,从中间向两边逐渐变小,近似成余弦分布.测量误差为495%.应用模拟退火算法,结合BRDF五参量统计模型,获得了测量光谱范围内各波长对应的共2101组五参量值,通过对比参量计算结果和 关键词： 双向反射分布函数 绝对测量 误差分析 参量模型     

基于主成分分析的复杂光谱定量分析方法的研究

针对超短脉冲激光与气体相互作用产生的非线性荧光光谱的特点,提出了光谱分析的预处理、特征提取以及定量分析的有效方法.采用小波算法对光谱数据进行压缩和降噪处理,使光谱数据由3979点压缩降噪至664点.对处理后的光谱特征峰团的强度进行主成分分析,结果表明2个主成分即可包含98%的光谱信息.采用第一主成分对不同浓度下的谱线强度进行拟合与误差计算,有效地提取了与气体浓度有关的特征参量.实现了气体的定量分析.同已有的定量分析方法相比,定量分析的精度有较大提高,特别在所关心的低浓度情况下,定量分析的精度改善更为明显.3种气体的拟合与计算显示同以往方法相比误差由0.2694降为0.02.     

Mössbauer and infrared spectroscopy as a diagnostic tool for the characterization of ferric tannates

The line shape of the (3p???1s) X-ray transition in muonic hydrogen was measured for the first time with a high-resolution crystal spectrometer. The assumption of a statistical population of the hyperfine levels was directly confirmed by experiment, and a measured value for the hyperfine splitting is reported. An X-ray line broadening due to Doppler effect could be clearly identified and attributed to different Coulomb de-excitation transitions which precede the measured radiative transition. The results allow a decisive test of advanced cascade model calculations and establish an alternative and “model free” method to extract the strong-interaction parameters from pionic hydrogen data.     

透明光学树脂中Eu3+辐射参数的理论和实验研究

报道了一种新合成的含三元稀土配合物的透明光学树脂材料的辐射特性的研究。基于J-O参数理论,利用含稀土配合物Eu(TTA)3phen-0.31wt%的光学树脂的发射荧光光谱,计算了Eu3 在光学树脂基质中的J-O参数Ω2=10.139 4×10-20cm2,Ω4=3.810 9×10-20cm2,Ω6=9.050 7×10-20cm2。利用得到的J-O参数可以计算光学树脂中Eu3 的跃迁振子强度fcal,5D0激发态的辐射跃迁概率A(456.6 s-1)、辐射寿命τ(2 190.1μs),还计算了光学树脂中Eu3 的跃迁5D0→7FJ′(其中J′=1,2,4,6)的发射截面σ、荧光分支比β。通过分析计算得到的J-O参数可知,光学树脂中Eu3 的5D0亚稳态的寿命较长,跃迁5D0→7F2的发射截面最大,说明含稀土配合物的光学树脂具有作光放大或激光材料的潜在性。     

Efficient line-by-line calculation of absorption coefficients to high numerical accuracy

Modeling radiative transfer at high resolution is computationally expensive due to the need to evaluate spectral absorption coefficients on a line-by-line basis. A simple yet efficient method is presented here for calculating these coefficients to high numerical accuracy. For each spectral line retained in the model, this method evaluates a contribution to absorption over the entire frequency range of interest (i.e., the far wings of each line are not truncated). The accuracy achieved is independent of the size of the sampling interval. The level of accuracy may be varied continuously over many orders of magnitude, thereby permitting the user to trade accuracy for speed and rendering it easy to perform convergence studies that quantify the numerical error. The method is applicable to any analytic model of the spectral line shape.     

Coupled radiation and natural convection: Different approaches of the slw model for a non-gray gas mixture

The coupling between non-gray radiation heat transfer and convection-conduction heat transfer is studied. The spectral line weighted sum of gray gases model (slw) is used to account for non-gray radiation properties. The aim of this work is to analyze the influence of the different approaches used when calculating the parameters of the slw model. Such strategies include the use of optimized model coefficients to reduce the number of operations, and the interpolation of the distribution function instead of the use of mathematical correlations. Non-gray calculations are also compared to gray solutions using the Planck mean absorption coefficient, which can be also calculated with the slw model. The radiative transfer equation (rte) is solved by means of the discrete ordinates method (dom). A natural convection driven cavity is chosen to couple radiation and conduction-convection energy transfer. Several cases, with a significant variation of the ratio between radiation to convection heat transfer, as well as the ratio between radiation to conduction heat transfer, are discussed.     

Nd3+掺杂B2O3-Nb2O5-BaO-La2O3玻璃光谱性质的研究

 用高温熔融法制备了Nd³⁺(物质的量分数2％）掺杂40B₂O₃-(15-χ)Nb₂O₅-45BaO-χLa₂O₃玻璃，测量了样品的吸收光谱、发射光谱和差热分析（DTA）曲线。根据Nd3+光学跃起矩阵的特点，应用Judd-Ofelt理论，从吸收光谱获得了Nd³⁺光学跃起的强度参数。并计算了Nd³⁺离子的自发辐射跃迁几率、总自发辐射几率、荧光分支比、辐射能级寿命和受激发射截面。结果表明：该体系玻璃中，随着Nb₂O₅ 含量的增加和La₂O₃₂增大，说明材料的对称性降低；而Ω₆减小，说明Nd-O键的共价性和键强增强；受激发射截面减小。DTA实验表明，随着Nb₂O₅含量的增加，材料的热稳定性提高。     

An optimized line by line code for plume signature calculations—I: model and data

An optimized line-by-line fortran code for the calculation of aircraft infrared plume signature has been developed an implemented. In this model, the absorption coefficient is separated into two components. The first, which varies quickly with wavenumber, results from the addition of nearby individual line contributions with Voigt line-shapes. The second term, which accounts for both line-wings and collision-induced absorption processes, has a simple dependence on pressure and varies slowly with wavelength. It is pre-calculated and tabulated versus wavenumber and temperature and its treatment involves very small CPU times. For an efficient calculation of the contributions of nearby lines, where most of the computational effort lies, a number of procedures have been developed. The first is a quick evaluation of the Voigt line shape through interpolations within tabulated values. The second is the use of multiple frequency grids of increasing steps on which the various parts of the lines are projected successively starting from line center. The third optimization is a sort of the lines accounted for in the calculations which rejects those of negligible contribution. Finally, more CPU time can be saved by using a proper cut-off distance in the line wings and/or stopping the calculations in spectral regions that are optically very thick. One of the characteristics of our approach, when compared to previous ones, is that all approximations made to quicken calculations lead to errors that are controlled through precision criteria which are chosen by the user.     

Ho3+掺杂GeO2-Ga2O3-Li2O-BaO-La2O3玻璃的光谱和增益特性的计算

用高温熔融法制备了不同Ho3+浓度掺杂的65GeO2-12Ga2O3-8Li2O-10BaO-5La2O3-χHo2O3锗酸盐玻璃.从吸收光谱出发,应用Judd-Ofelt理论,获得了Ho3+离子的跃迁强度参量（Ω2,Ω4,Ω6）,并由此计算了Ho3+离子的自发辐射跃迁几率A,荧光分支比β,辐射能级寿命τ等光谱参量.根据McCumber理论,计算了Ho3+离子能级5I8→5I7（2.0 μm）跃迁的吸收截面和受激发射截面,同时也获得了相应的反映粒子数反转的增益截面光谱.钬掺杂的锗酸盐玻璃,其增益截面的最大值比所报道的氟锆铝酸盐玻璃大.结果表明,Ho3+掺杂的锗酸盐玻璃在2.0 μm附近波段的中红外激光器中将有一定的应用前景.     

无云地球大气背景辐射光谱亮度的计算模型

根据辐射的叠加性,提出了一种用于卫星遥感无云地球大气背景辐射强度计算的理论模型。在利用该模型对晴朗无云地球大气背景的光谱辐射亮度进行计算时,使用迭代法解辐射传输方程并对大气采用动态分层。模型计算的结果与法国6S软件计算结果的对比表明：该模型以及计算方法对于无云地球大气背景向上的辐射亮度计算是精确可行的。且计算结果说明在可见光波段地球大气背景的辐射是很强的,而在红外强吸收波段,地-气系统的辐射很弱,主要来自大气的后向散射。     

Approximate line shapes for hydrogen

Two independent methods are presented for calculating radiative transport within hydrogen lines. In Method 1, a simple equation is proposed for calculating the line shape. In Method 2, the line shape is assumed to be a dispersion profile and an equation is presented for calculating the half half-width. The results obtained for the line shapes and curves of growth by the two approximate methods are compared with similar results using the detailed line shapes by Vidal et al.