CaBa-铝酸盐玻璃中Cr~(4+)谱线宽度随温度的变化

测量了 1 5～ 3 0 0K温度范围内 57 5%Al1 5O 3 5%CaO 7 5%BaO玻璃中四价铬的发射光谱。这种材料中铬离子的能级处于Tanabe Sugano图上弱场范围中 ,最低的激发态是3 T2 ,发射谱是一个宽带。按照单频近似理论拟合低温下的光谱 ,得到3 T2 能级的零声子线位置Ezp=84 0 0cm-1,声子能量 ω =3 2 0cm-1,黄昆因子S =3 58。尽管单频近似能够较好地描述低温下的线形 ,发射光谱宽度随温度的变化却与单频近似理论的结果不符。讨论了这种差别的原因 ,认为可能的解释是与激发态耦合的声子能量大于与基态耦合的声子能量。     

Cr3+掺杂的Ca3Al2Ge3O12石榴石的光谱性质

在此报告钙铝锗石榴石Ca₃Al₂Ge₃O₁₂中Cr³⁺离子的光谱特性,依据不同浓度的样品在不同温度下发射光谱的实验结果,分析了不等价Cr³⁺发光中心零声子线R₁,R₂的位置变化情况。通过对Cr³⁺吸收和发射光谱的分析,估算了Cr³⁺所处格位的晶场强度参数Dq和Racah参数,同时,对低温下Cr³⁺R线边带振动光谱的精细结构的起因进行了分析和指认。在室温和低温下测得Cr³⁺的⁴T₂→⁴A₂和²E→⁴A₂能级跃迁的荧光衰减为单指数规律。     

纳米晶体ZnS：Mn2+发光寿命异常减缩机理的探讨

纳米晶体ZnS:Mn²⁺中Mn²⁺粒子⁴T₁→⁶A₁的发光寿命比晶体减缩了5个量级,这颇令人费解,因为通常解除自旋禁戒的磁作用远无如此强的效应.假定基质态的自旋不为零,且考虑了Mn²⁺的d电子和基质之间的交换库仑作用.若基质存在比Mn²⁺的⁴T₁激发态能量略高的某种激发态,则这种交换库仑作用将导致这两种激发态之间的混合,从而可解除发光能级弛豫中的自旋禁戒.这种混合随基质颗粒尺寸的减小而加强.我们并对此机制进行粗略的数值估计,给出了和实验相容的结果.     

ZnS:Ho3+的辐射跃迁和无辐射过程

本工作研究了Ho³⁺离子在宽禁带半导体ZnS中的辐射跃迁和无辐射过程。用发射谱线的积分光强和激发态寿命获得ZnS:Ho³⁺的强度参数Ω_λ,同时计算了九个激发态的辐射跃迁几率和能级寿命。另外,通过在不同温度下测定Ho³⁺离子⁵G₆,³K₈,⁵F₂,⁵F₃和⁵S₂(⁵F₄)能级的发射光强和寿命的方法,研究了这几个激发态间的无辐射过程,其中⁵G₆,³K₈,⁵F₂和⁵F₃这四个能级是处于热平衡状态,而⁵F₃与⁵S₂(⁵F₄)能级间存在五个声子((1/n)ω_Lo=351cm^-1)参与的多声子弛豫过程。 关键词：     

非晶锂离子导体B2O3-Li2O-LiCl一Al2O3中VO2+的电子自旋共振

两种非晶锂离子导体B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃-0.1V₂O₅(x=0.05和0.15)的电子自旋共振谱研究表明:(i)ESR线型是高斯型,证实V₂O₅添加量适当;(ii)超精细结构来源于VO²⁺络离子,具有四角对称性,属C_4v群。越精细耦合张量的平行分量平均值A_//=0.0175cm^-1,垂直分量A_⊥=0.0063cm^-1。由g_//(g_⊥)求出其基态²B_2g与第一激发态²E_g的能级间距△₁=2.46×10⁴ cm^-1,基态与第二激发态²B_1g的能级间距△₂=3.03×10⁴ cm^-1;(iii)变温实验证实:Al₂O₃组分较少(x=0.05)的非晶ESR强度比x=0.15的非晶高3倍至2倍,而Al₂O₃组分越多则ESR强度随温升下降越小。     

HF分子电子基态和激发态的MRCI计算

应用舍Davidson修正的多参考组态相互作用（MRCI）方法,在aug-cc-pVTZ基组水平上对HF基态及最低的多个单重和三重电子激发态进行了势能扫描计算.结合群论原理及分子的离解极限,分析了电子态势能曲线的特征,得出激发态B¹S⁺对应的离解极限为H⁺+F^-（¹S）.基于势能曲线,数值求解核运动的径向Schrodinge方程,得到J=0时束缚电子态X¹S⁺,B¹S⁺,C¹P和D¹S⁺的振动能级和转动常数,继而进行数据拟合得到电子态的光谱常数,基态X¹S⁺:ω_e=4146.94 cm^-1,ω_ez_e=88.08 cm^-1,B_e=21.22 cm^-1,a=0.785 cm^-1;B¹S⁺态:ω_e=1131.37 cm^-1,ω_ex_e=17.28 cm^-1,B_e=3.96 cm^-1,a_e=0.0215 cm^-1,C¹P态:ω_e=2696.37 cm^-1,ω_ex_e=73.43 cm^-1,B_e=15.91 cm^-1,a_e=0.776 cm^-1,D¹S⁺态:ω_e=3104.22 cm^-1,ω_ex_e=118.92 cm^-1,B_e=17.25 cm^-1,a_e=0.992 cm^-1,拟合结果与实验值吻合的较好.     

调谐激光晶体Cr3+:ZnWO4光致发光特性的研究

研究了调谐激光晶体Ｃｒ³⁺：ＺｎＷＯ₄的光致发光特性。报道了它的吸收光谱、激发光谱、发射光谱及其随温度的变化、零声子跃迁和发射寿命等实验结果，并讨论了激发特性、电子－声子耦合作用、ＺｎＷＯ₄中Ｃｒ³⁺的发射寿命曲线等相关问题。 关键词：     

一维反铁磁体二水CsMnCl3中激子的振动猝灭和黄昆-Rhys因子

在一维反铁磁体CsMnCl₃·2H₂O中,用D₂O代替其中的结晶水之后,对于⁴T₁→⁶A₁激子跃迁,观察到三种明显的效应:激子线红移18cm^-1;激子讯号增强近一个数量级;激子寿命由0.58ms变为9.2ms,增加15倍。这后一种效应在文献中尚未见报道,它说明这种同位素替代使振动猝灭受到很大的减弱。利用多声子辐射和无辐射跃迁理论,讨 关键词：     

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     

TiO2∶Mo体系的光子雪崩上转换

在978nm激光二极管的激发下，Mo掺杂的TiO₂材料表现出很强的宽带上转换发光 ，该发光来源于［MoO₄］^2-基团的激发态³T₁, ³T₂能级到基态¹A₁能级的电子跃迁.通过研究发光强度与抽运功率的关系及上转换发光的上升时间曲线，发现TiO₂∶Mo体系的上转换发光中存在着雪崩机制，应用转 关键词： 上转换 光子雪崩 转移函数理论     

Diffusion of W on A W(211) plane

The diffusion of W on a (211) plane of a W field emitter has been re-examined by means of the fluctuation autocorrelation method. Diffusion along channels yielded E = 16.8 ± 0.5 kcal, D₀ = (3 ± 1) × 10⁻⁵ cm² s⁻¹. For diffusion across channels E =6.6 kcal, D₀ = 4 × 10⁻⁹cm² s⁻¹ at T < 752 K, and E = 24 kcal, D₀ = 5 × 10⁻⁴ cm² s⁻¹ at T > 752 K. The results for diffusion along channels yield E and D₀ values intermediate between recent results by Wang and Ehrlich [Surf. Sci. 206 (1988) 451] using field ion microscopy (E = 19 kcal, D₀ = 7.7 × 10⁻³ cm² s⁻¹) and Tringides and Gomer [J. Chem. Phys. 84 (1986) 4049], using the same method as the present work but a larger slit (E = 13.3 kcal, D₀ = 7 × 10⁻⁷ cm² s⁻¹). The results for cross channel diffus good agreement with those of Tringides and Gomer below 752 K, where these authors stopped. The new high temperature results suggest that the channel wall exchange mechanism postulated by Tringides and Gomer for cross channel diffusion at low T gives way to diffusion by climbing over the channel walls with higher E but also higher D₀ above 752 K. Possible reasons for the discrepancies between these three sets of results and the absence of cross channel diffusion in the work of Wang and Ehrlich are briefly discussed.     

Raman phonon anomalies in Sr(Fe1-xCox)2As2

Phonon anomalies have been reported in iron-pnictide superconductors indicating a diverse interplay between different orders in the materials.Here,we report Raman scattering measurements on Sr(Fe_1-xCo_x)₂As₂(x=0 and x=0.04)single crystals in the B;symmetry with respect to a 1 Fe unit cell.Upon cooling,we observe a larger split(13 cm;)of Eg Raman phonon modes pertaining to in-plane Fe and As displacements as the crystals undergo the tetragonal-toorthorhombic structural phase transition,although a considerable split(9 cm;)has been reported in BaFe_1-xCo_x)₂As₂.Furthermore,the splitting of E;phonon modes is strongly reduced upon doping.We perform an order-parameter analysis revealing a similar doping dependence of E;phonon splitting as reported in other compounds of the 122 family,indicating these phonon anomalies widely exist in 122 iron-based superconductors and might share the same mechanisms.     

LiAl分子基态、激发态势能曲线和振动能级

利用单双激发多参考组态相互作用方法获得了LiAl分子基态X¹∑⁺及七个激发态a³∏, A¹∏, b³∑⁺, c³∑⁺, B¹∏, C¹∑⁺, d³∏的势能曲线, 通过势能曲线得到各态的平衡核间距R_e, 进而求得绝热激发能和垂直激发能.计算结果表明:c³∑⁺ 电子态是一个不稳定的排斥态, A¹∏态是一个较弱的束缚态, 其余6个电子态均为束缚态; b³∑⁺与 c³∑⁺态之间存在预解离现象; 8个电子态分别解离到两个通道, 即Li(²S)+Al(²P⁰)与Li(²P⁰)+Al(²P⁰). 接着将势能曲线拟合到Murrel-Sorbie解析势能函数形式, 据此获得各态的光谱数据:基态X¹∑⁺的平衡键长为0.2863 nm, 谐振频率为316 cm^-1, 解离能D_e为1.03 eV, 激发态a³∏, A¹∏, b³∑⁺, c³∑⁺, B¹∏, C¹∑⁺, d³∏的垂直激发能依次为0.27, 0.83, 1.18, 1.14, 1.62, 1.81, 2.00 eV; 解离能依次为1.03, 0.82, 0.26, 排斥态, 1.54, 1.10, 0.93 eV, 相应谐振频率 ω_e为339, 237, 394, 排斥态, 429, 192, 178 cm^-1. 通过求解核运动的薛定谔方程找到了J=0时 LiAl分子7个束缚电子态的振动能级和转动惯量. 关键词： LiAl 光谱常数 势能曲线 振动能级     

Diffusion of silicon in Fe-based amorphous and crystalline alloys

The segregation rate of silicon was measured in three different Fe-based amorphous and crystallized alloys with different silicon contents: 3.5, 5 and 9 at%. Analysis of the segregation kinetics yielded the diffusion activation energies E, as well as the frequency factors D₀. A linear dependence was found between In D₀ and E. In general, the D₀ and E values were lower for the amorphous specimens than for the crystalline ones, were independent of silicon content and are explained in terms of an oversaturated concentration of structural defects. In the crystalline specimens, diffusion behaviour was influenced by silicon content near the solubility limit of silicon in iron.     

Investigation on the Cs 6S1/2 to 7D electric quadrupole transition via monochromatic two-photon process at 767 nm

We experimentally demonstrate the cesium electric quadrupole transition from the 6S_1/2 ground state to the 7D_3/2,5/2 excited state through a virtual level by using a single laser at 767 nm. The excited state energy level population is characterized by varying the laser power, the temperature of the vapor, and the polarization combinations of the laser beams. The optimized experimental parameters are obtained for a high resolution transition interval identification. The magnetic dipole coupling constant A and electric quadrupole coupling constant B for the 7D_3/2,5/2 states are precisely determined by using the hyperfine levels intervals. The results, A = 7.39 (0.06) MHz, B = −0.19 (0.18) MHz for the 7D_3/2 state, and A = −1.79 (0.05) MHz, B =1.05 (0.29) MHz for the 7D_5/2 state, are in good agreement with the previous reported results. This work is beneficial for the determination of atomic structure information and parity non-conservation, which paves the way for the field of precision measurements and atomic physics.     

Study on the local structure of (CrO6) complex in garnet crystals by optical and EPR spectrum

The local lattice structure distortions for YAG and YGG systems doped with Cr³⁺ have been investigated by the d³ configuration complete energy matrices which contain the Zeeman energy besides the electron–electron interaction, the trigonal crystal field as well as the spin–orbit coupling interaction. The local lattice structure parameters R and θ of (CrO₆)⁹⁻ complex are determined for Cr³⁺ in YAG and YGG systems, respectively. The calculated results show that the local lattice structures have expansion distortions, which almost tend to the same after distortions. Meanwhile, the EPR parameter D, g factors (g_||, g) and optical spectrum of these systems have been interpreted uniformly by quantitative calculation. It is shown that the effect of the orbit reduction factor k on g factors (g_||, g) cannot be ignored.     

Boron diffusion in bcc-Fe studied by first-principles calculations

The diffusion mechanism of boron in bcc-Fe has been studied by first-principles calculations. The diffusion coefficients of the interstitial mechanism, the B–monovacancy complex mechanism, and the B–divacancy complex mechanism have been calculated. The calculated diffusion coefficient of the interstitial mechanism is D_0= 1.05 ×10~(-7)exp(-0.75 e V/k T) m~2· s~(-1), while the diffusion coefficients of the B–monovacancy and the B–divacancy complex mechanisms are D_1= 1.22 × 10~(-6)f1exp(-2.27 e V/k T) m~2· s~(-1)and D_2≈ 8.36 × 10~(-6)exp(-4.81 e V/k T) m~2· s~(-1), respectively. The results indicate that the dominant diffusion mechanism in bcc-Fe is the interstitial mechanism through an octahedral interstitial site instead of the complex mechanism. The calculated diffusion coefficient is in accordance with the reported experiment results measured in Fe–3%Si–B alloy(bcc structure). Since the non-equilibrium segregation of boron is based on the diffusion of the complexes as suggested by the theory, our calculation reasonably explains why the non-equilibrium segregation of boron is not observed in bcc-Fe in experiments.     

SeN_2自由基解析势能函数的耦合簇理论研究

利用单双迭代耦合簇理论CCSD结合相关一致四重基组cc-pVQZ对SeN2基态的平衡结构和谐振频率进行了优化计算.计算结果表明:基态SeN2自由基分子稳定态为C2v构型,基态电子组态为X1A1,平衡核间距RSe-N=0.1691 nm,RN-N=0.1970 nm,αN-Se-N=71.289?,离解能De=4.78 eV.基态简正振动频率分别为:ν1=326.9288 cm-1,ν2=808.0161 cm-1以及ν3=948.3430 cm-1.对SeN基态和N2基态采用上述相同方法进行几何构型与谐振频率的计算并进行单点能扫描,使用Murrell-Sorbie函数进行最小二乘拟合得到其势能函数和光谱常数,通过和其他理论值以及实验值做比较,显示本文的计算工作达到了很高的精度.应用多体项展式理论导出了基态SeN2的全空间解析势能函数,其势能函数等值势能图准确再现了SeN2分子的结构特征和能量变化.