Cu1-xHxZr2(PO4)3中Cu2+的EPR谱和局域结构研究

本文采用Cu²⁺斜方对称电子顺磁共振（EPR）参量的高阶微扰公式计算了晶体Cu_1-xH_xZr₂（PO₄）₃中Cu²⁺的EPR参量（g因子和超精细结构常数A因子）．计算结果表明,晶体Cu_1-xH_xZr₂（PO₄）₃中[CuO₆]^10-基团的Cu-O键长分别为R_||≈0.241 nm,R_⊥≈0.215 nm,平面键角τ≈80.1°;由于对称性降低,中心金属离子基态²A_1g（θ）和²A_1g（ε）有一定程度混合,混合系数α≈0.995．所得EPR谱图的理论计算值与实验数据符合得很好．     

An investigation of local structures and EPR spectra for Cu2+ and VO2+ in biochar

Electron paramagnetic resonance (EPR) technology had been adopted to analyze the structures and properties of Cu²⁺ and VO²⁺ in Biochar (BG1 and BG2), but the local structural properties have not been clarified up to now. In present work, three possible structures (orthorhombically, rhombically and tetragonally elongated octahedra) are proposed for Cu²⁺ in BG1 and BG2 samples, and the former seems most reasonable in view of the best agreement between the theoretical EPR parameters based on the perturbation formulae and the experimental data. As for the VO²⁺ center, unlike the previous assignment of the tetragonally elongated [VO₅]⁶⁻ cluster based on the simple formulae of EPR parameters, presently proposed tetragonally compressed [VO₆]⁸⁻ cluster and the high order perturbation formulae of the EPR parameters yields good agreement with the observed values. This point is also supported by the d-d optical absorption ²B_1g →²B_2g for tetragonally compressed octahedral 3 d¹ systems.     

Spectroscopic Study of Cu(II) Ion Doped in Bis-Glycine Sodium Nitrate

Single-crystal Electron Paramagnetic Resonance (EPR) and optical absorption studies were performed at room temperature on Cu(II)-ion–doped bis-glycine sodium nitrate, a semiorganic nonlinear optical material (NLO). Spin-Hamiltonian parameters, obtained from single-crystal EPR spectra, recorded in three mutually orthogonal planes, revealed the presence of two magnetically inequivalent Cu(II) sites. Molecular orbital parameters were also evaluated. The optical absorption spectrum at room temperature exhibits the lowering of octahedral symmetry to an axially elongated tetragonal of Cu(II) ion in NLO.     

掺铜PTO晶体顺磁共振谱及局域结构的理论研究

基于晶体场理论,本文采用重叠模型和3d⁹电子组态在畸变四角晶场中的g因子和超精细结构常数A的三阶微扰计算公式以及钛酸铅PbTiO₃ (PTO): Cu²⁺晶体的局域结构与EPR谱之间的定量关系,合理解释了PTO: Cu²⁺晶体的EPR谱及局域晶体结构,所得结果与实验观测相符合.      

Optical absorption near infrared and EPR studies of mottramite

Mottramite mineral from Tsumeb Corporation Mine, Tsumeb, Otavi, Namibia, is investigated in this present work. The mineral contains vanadium and copper contents of 22.73% and 16.84% by weight, respectively, as V₂O₅ and CuO. An electron paramagnetic resonance (EPR) study confirmed the presence of Cu(II) with g = 2.2. The optical absorption spectrum of mottramite indicates that Cu(II) is present in a rhombic environment. Near infrared results are due to water fundamentals.     

ZnO:V3+晶体光谱和电子顺磁共振谱的理论研究

采用强场耦合图像,建立了3d2电子组态在三角对称中的45×45能量矩阵,通过对角化完全能量矩阵的方法,计算出了ZnO:V3 晶体的45条光谱能级和5个电子顺磁共振谱参量(零场分裂D,g因子g//,g⊥和超精细结构常数A//,A⊥),计算结果与实验数值能很好地符合.计算中还发现V3 杂质中心的局部结构与基质晶体的结构不一致,即V3 在ZnO中并不占据准确的Zn2 位置,而是沿c3轴方向位移一段距离△Z≈0.003 nm.作者对上述这些结果的合理性进行了讨论.     

晶体PZCST:VO2+的EPR谱及光吸收谱的理论研究

采用双旋-轨耦合参量模型和3d¹电子组态在四角对称下的能级公式,计算了KZnClSO₄·3H₂O(PZCST): VO²⁺的EPR谱和光吸收谱,所得EPR谱和光吸收谱的理论结果与实验发现符合得很好. 研究发现,该晶体沿C₄轴局域对称结构呈压缩的四角畸变,其大小为0.47 nm;大的κ值表明VO²⁺的未配对电子的自旋极化对超精细结构常数有着较大的贡献.     

Defect Structure and EPR Parameters of the Cu2+Center in MNB Ternary Glasses

The electron paramagnetic resonance (EPR) parameters (g factors g _//, g _⊥ and hyperfine structure constants A _//, A _⊥) for 15MgO-15Na₂O-69B₂O₃ (MNB):Cu²⁺ ternary glasses were calculated based on the high-order perturbation formulae of 3d⁹ ion in a tetragonal symmetry. From the calculations, the defect structures of MNB:Cu²⁺ ternary glasses were obtained and a negative sign for A _// and A_⊥ for the Cu²⁺ center is suggested in the discussion.     

A Computer Program to Help Resolution of Complex and Poorly Resolved Cu2+ and VO2+ Ions Doped Single Crystals Electron Paramagnetic Resonance Spectra

Complex and poorly resolved Cu²⁺ and VO²⁺ doped single-crystal electron paramagnetic resonance (EPR) spectra are some of the serious problems that exist in this area. In order to help the resolution of this sort of spectra, and for easily resolvable spectra as well, a versatile computer program known as EPR RESolution, or EPRES, is presented. All detectable line positions in the single-crystal spectra taken in three mutually perpendicular planes are given as input. The program plots these line positions. The user then manually determines the lines by selecting the true data points on the plot and fitting them to a well-known variation function. If selection is not suitable, the process is canceled and renewed. By this process, as many resolvable lines as in the spectra can be resolved and determined. The user then groups the resolved lines according to the paramagnetic center to which they belong. This includes the attribution of correct nuclear spin I and M _I to correct lines. After this step, hyperfine and g tensor elements can be found, constructed, and diagonalized.

[Supplemental materials are available for this article. Go to the publisher's online edition of Spectroscopy Letters for the following free supplemental resource: a copy of the EPRES computer program.]     

EPR and Optical Study of Cu<Superscript>2+</Superscript> Ions Doped in Sodium Zinc Sulfate Tetrahydrate Single Crystals

Electron paramagnetic resonance (EPR) study of Cu²⁺-doped sodium zinc sulfate tetrahydrate is done at liquid nitrogen temperature. Two magnetically equivalent sites for Cu²⁺ are observed. The spin-Hamiltonian parameters determined by fitting the EPR spectra to the rhombic-symmetry crystalline field are g _x  = 2.2356, g _y  = 2.0267, g _z  = 2.3472, A _x  = 27 × 10⁻⁴ cm⁻¹, A _y  = 54 × 10⁻⁴ cm⁻¹and A _z  = 88 × 10⁻⁴ cm⁻¹. The ground state wave function is also determined. The g-anisotropy is evaluated and compared with the experimental value. With the help of optical study, the nature of bonding in the complex is discussed.     

An EPR Study on the Chemical form of Mn2+ in the Chinese Loess Samples

Electron paramagnetic resonance (EPR) spectroscopy in combination with thermal methods were used to identify and characterize Mn²⁺ in the Chinese loess that is a multimineral system. EPR spectra of the loess samples from the classic loess-paleosol section in central China show the presence of trace amounts of Mn²⁺; whereas paleosol samples present no Mn²⁺ EPR signal. The spectral changes upon step heating from room temperature to 1000 °C suggest that this EPR signal in the loess arises from Mn substituted into CaCO₃. This study provides a direct evidence that the loess-paleosol profiles were formed under the changing redox conditions caused by a past climatic change.     

Theory studies of the local lattice distortions and the EPR parameters for Cu2+, Mn2+ and Fe3+ centres in ZnWO4

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (g factors, hyperfine structure constants and zero-field splittings) for Cu²⁺, Mn²⁺ and Fe³⁺ in ZnWO₄ are theoretically studied based on the perturbation calculations for rhombically elongated octahedral 3d⁹ and 3d⁵ complexes. The impurity centres on Zn²⁺ sites undergo the local elongations of 0.01, 0.002 and 0.013 Å along the C₂ axis and the planar bond angle variations of 8.1°, 8.0° and 8.6° for Cu²⁺, Mn²⁺ and Fe³⁺, respectively, due to the Jahn–Teller effect and size and charge mismatch. In contrast to the host Zn²⁺ site with obvious axial elongation (～0.31 Å) and perpendicular (angular) rhombic distortion, all the impurity centres demonstrate more regular octahedral due to the above local lattice distortions. The copper centre exhibits significant Jahn–Teller reductions for the spin-orbit coupling and orbital angular momentum interactions, characterised by the Jahn–Teller reduction factor J (≈0.29 ? 1). The calculated EPR parameters agree well with the experimental results. The local structures of the impurity centres are analysed in view of the corresponding lattice distortions.     

三角晶场中4A2(3d3)态离子全组态EPR理论研究

在中间场耦合图像中,建立了＾４Ａ２（３ｄ＾３）态离子全组态ＥＰＲ理论;研究了ＥＰＲ参量随三角晶参量Ｖ、Ｖ＇及立方晶场参量Ｄｑ变化关系;用完全对角化方法验证了Ｍａｃｆａ５ｌａｎｅ ＥＰＲ的三阶微扰公式,结果表明,在较大的晶场范围内微扰公式的收敛性很好;研究了ＥＰＲ参量的微观起源及自放二重态对ＥＰＲ参量的贡献,指出自旋二重 对零场分裂参量的贡献不可忽略,二重态对ｇ因子的贡献甚微。     

Investigations on the EPR parameters and tetragonal distortions for Cu2+ in alkali lead tetraborate glasses

The electron paramagnetic resonance parameters (g factors and hyperfine structure constants) and local structures are theoretically investigated for Cu²⁺ in alkali lead tetraborate 90R₂B₄O₇·9PbO·CuO (R = Li, Na and K) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d⁹ complex. The [CuO₆]^10? complexes are found to experience the relative tetragonal elongation ratios 18%, 23% and 30% for R = Li, Na and K, respectively, due to the Jahn–Teller effect, much larger than those for similar ARbB₄O₇ (A = Li, Na and K) glasses. This point is attributed to the lattice expansion (longer A–O bond lengths) with doped PbO, yielding lower force constants and more intense Jahn–Teller elongations in the 90R₂B₄O₇·9PbO·CuO glasses. The increasing tendency (Li > Na > K) of the relative elongation ratio λ, covalency and the ratio Δg_///Δg_⊥ for g-shifts are systematically analysed in a uniform way.     

ICP-MS研究黄河三湖河口表层沉积物对Cd~(2+)和Cu~(2+)的吸附-解吸特性

为了研究黄河上游表层沉积物与Cd~(2+)和Cu~(2+)的相互作用机理,以黄河三湖河口表层沉积物(简称样品)为研究对象,采用电感耦合等离子体质谱(ICP-MS)技术,优化样品对Cd~(2+)和Cu~(2+)的吸附固液比、时间、pH等条件。并在此条件下研究了Cd~(2+)和Cu~(2+)在样品上的吸附特性和解吸特性。结果表明:两种金属的优化吸附条件不同,在各自优化吸附条件下,样品对Cu~(2+)和Cd~(2+)的平衡吸附量分别为0.88和0.13 mg·g~(-1);对两种金属的吸附动力学符合伪二级吸附动力学模型,且样品对Cu~(2+)的吸附速率大于对Cd~(2+)的吸附速率;吸附热力学拟合结果显示吸附过程符合Freundlich模型,对两种金属的吸附均属于优惠型吸附,且吸附过程属于吸热过程,可自发进行;解吸动力学研究表明,两个金属的解吸过程均符合Elovich方程,属于非均相扩散;在多离子竞争吸附-解吸实验中发现,样品对Cu~(2+)的吸附-解吸受到共存离子的影响更大。研究结果揭示了黄河三湖河口表层沉积物对Cd~(2+)和Cu~(2+)吸附和解吸的作用机理以及共存离子对吸附解吸特性的影响。对于分析重金属在水体与沉积物之间的作用机理、固液两相分布规律以及重金属迁移能力提供了理论依据,同时也为制定研究区域针对性的重金属防控措施具有一定指导意义。     

Dy^(3+)掺杂Lu_(2)O_(3)和Y_(2)O_(3)单晶光纤下转换荧光测温性能EI北大核心CSCD

稀土倍半氧化物单晶光纤材料凭借超高的熔点(~2400℃)、稳定的物化性能以及灵活的结构被认为是极具潜力的高温传感介质。本文采用激光加热基座(LHPG)法,成功生长了透明无开裂Dy^(3+)离子掺杂的倍半氧化物单晶光纤Lu_(2)O_(3)和Y_(2)O_(3)。依据Dy^(3+)离子的^(4)I_(15/2)和^(4)F_(9/2)能级为一对热耦合能级对(TCLs),测试得到了430~520 nm波长范围内的下转换荧光光谱。荧光强度比(FIR)结果显示,晶体在298~673 K温度范围内的荧光强度具有良好的温度相关性。其中Dy∶Lu_(2)O_(3)在该范围内的最大相对灵敏度和绝对灵敏度分别为0.97%·K^(-1)(315 K)和1.62×10^(-4) K^(-1)(673 K),展现出更为优异的温度传感性能。     

晶体CsMgCl3:Ni2+的局部结构、光谱和EPR谱的理论研究

本文采用半自洽场(semi-SCF) 自由Ni2+的3d轨道波函数、点电荷-偶极子模型和Ni2+-6X-(X=F,Cl,Br,I)络合物的μ-κ-α模型,建立了结构参数与光谱、EPR谱之间的定量关系,利用完全对角化方法,由光谱和电子顺磁共振(EPR)谱,确定了CsMgCl3:Ni2+晶体的局部结构参数,统一解释了CsMgCl3:Ni2+晶体的吸收光谱和EPR 谱.此外,还讨论了高阶微扰方法、参量拟合方法等问题.理论计算结果与实验值符合得很好.     

CLi+5超碱团簇的结构及储氢性能的理论研究

利用密度泛函理论( B3LYP) 方法,在 6 - 311 + + G ( d,p) 基组水平上,对超碱团簇 CLi₅及其阳离子体系 CLi₅⁺的几何结构和稳定性等物理化学性质进行理论计算,并进一步研究它们的储氢性能． 分析可知,CLi₅⁺超碱离子团簇结构相比中性 CLi₅团簇结构动力学稳定性要高,表面吸氢能力更强． 氢分子在 CLi₅⁺表面能以介于物理吸附与化学吸附之间的形式吸附,每个 Li 原子最多可以有效吸附三个 H₂,平均吸附能处于 1. 065 ～ 2. 732 k Cal/mol 范围内,储氢质量分数可达 39. 30 wt % ,表明 CLi₅⁺超碱离子团簇可以作为一种理想的储氢材料．