共查询到18条相似文献,搜索用时 156 毫秒
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文章考察了Mo-SiO2催化剂体系在丙烯歧化反应过程中的动态ESR波谱,发现在催化歧化反应过程中有两种Mo5+顺磁中心,一种为扰动八面体配位,g||=1.89,g⊥=1.94;另一种为扰动四棱锥配位,g||=1.86,g⊥=1.95。测得同位素95,97Mo5+的各向异性超精细耦合常数A||=90.3×10-4cm-1,A⊥=44.8×10-4cm-1;观测到反应产生的积炭信号,g≈2.0O2;氧阴离子自由基信号g1=2.018,g2=2.011,g3=2.005。用LCAO-MO理论对上述Mo5+的ESR波谱进行计算,求得分子轨道系数,发现并总结出△g||/△g⊥与△g成直线关系,并建议用△g||/△g⊥=4(△E(B2→E))/(△E(B2→B1)(β1/ε)2之比值作为衡量C4v扰动程度的尺度。 相似文献
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基于完全对角化方法,研究了4B1(3d3)态 离子在四角对称晶场中的磁相互作用,分析了自旋哈密顿参量(b02, g∥, g⊥ , Δg)的微观起源.结果表明 :在被考虑的大部分晶场区域,人们通常考虑的SO(spin-orbit)磁相互作用的贡献最为重要 ;然而,对于零场分裂参量b02而言,来自其他机理(包 括SS(spin-orbit),SOO(sp in-other-orbit),SO-SS-SOO)的贡献在大部分晶场区域超过了20%;在部分晶场区域,其 他机理的贡献甚至超过SO机理的贡献.详细地分析了Macfarlane 零场分裂参量b02 近似三阶微扰理论的收敛性,结果表明:该理论在大部分晶场区域收敛性较差.讨论了3d3 态离子第一激发态2Eg分裂的微观起源.并利用 群论方法解 释了在C4v和C3v对称晶场中2Eg< /sub>态分裂的不同机理.
关键词:
4B1(3d3)态离子')" href="#">4B1(3d3)态离子
磁相互作用
自旋哈密 顿参量
完全对角化方法(CDM)
微扰理论方法(PTM) 相似文献
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铜化合物ESR g张量和A张量的相关性及其与结构的关系 总被引:8,自引:0,他引:8
对于某些含有特定配位原子的钢化合物,找出了钢的ESR g‖和A‖之间的线性相关性;总结了相关性与钢化合物的分子结构间的联系;认为相关性与分子对称性及分子轨道性有关,分子对称性的提高和钢-配体间成键分子轨道共价性的降低引起g‖的增大和A‖绝对值的减小,对某些钢化合物,g‖与β12,A‖与β12之间存在线性关系.总结出由实测的g‖和A‖估算分子轨道系数β12值的方法. 相似文献
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五种还原Keggin结构杂多阴离子的ESR谱 总被引:2,自引:0,他引:2
本文报道了五种具有Keggin结构的还原杂多阴离子的溶液和-150℃冷冻ESR谱,它们是SiV2Mo10O406-、bSiV2Mo9O407--、PV3Mo9O406-、PV3W9O406-和VV3W9O406-。在室温下pH≤3时,所有杂多酸阴离子均为8条锐线,pH=7-8时,均为8+15条线并且随着放置时间增长逐步变成8条线。在-150℃时均呈现出V4+8条线的复杂粉末谱,作者根据一种修正的Ble-aney方法成功地模拟了这些冷冻谱,得出g‖、g⊥、A‖、A⊥,按照DeArmond理论计算了近似的K、α值并讨论了它们的物理意义。最后从异构体的数目和简并度的观点初步解释了观察不到V3物种22条超精细线的原因。Back 相似文献
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An EPR study of tetravalent vanadium centers created by room temperature X-irradiation in CaF2 and SrF2 is presented. The production efficiency of these centers is enhanced by previous annealing of the samples at 1000 K in air. The symmetry of V4+ ions is tetragonal and its EPR spectrum can be described by an axial spin Hamiltonian including a Zeeman and hyperfine term with and (corresponding to 51V nuclei). The following values for the spin Hamiltonian parameters are obtained g∥ = 1.947 ± 0.002, g⊥ = 1.935 ± 0.005, A∥ = 500 ± 5 MHz, A⊥ = 150 ± 10 MHz in the case of SrF2 and g∥ = 1.945 ± 0.002, A∥ = 505 ± 5 MHz and A⊥ < 200 MHz, in the case of CaF2. A model for the center including an interstitial O2? ion is tentatively proposed. 相似文献
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Zheng Wen-Chen 《辐射效应与固体损伤》2013,168(3-4):323-328
Abstract The zero-field splitting D, the anisotropic g-factors g ∥, Δg(=g ∥ ? g ⊥) and the first excited state splitting Δ(2 E) for the trigonal Cr3+–VK center in KMgF3: Cr3+ crystals have been studied from Macfarlane's high-order perturbation formulas. From the studies, the local structure of the trigonal center is obtained. The local lattice distortions (i.e., the displacement directions of the ions in the center) are consistent with the expectation based on the electrostatic interaction. 相似文献
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The electron paramagnetic resonance parameters D, g ∥ and g ⊥ for V3+ ions in α-Al2O3 crystals are calculated on the basis of the complete diagonalization method and the superposition model. In the calculation, the contributions of the variation of the cation–ligand bond lengths and bond angles are taken into consideration. The calculated results agree well with the experimental data. Our investigation shows that the local structure around the V3+ ions possesses a compressed trigonal distortion above the O2?-triangle and an elongated trigonal distortion in the lower one. 相似文献
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In this paper, the crystal field (CF) levels and spin-Hamiltonian (SH) parameters (g factors g ∥ and g ⊥ and hyperfine structure constants A ∥ and A ⊥) of the rare-earth ion Yb3+ in lithium yttrium fluoride crystals are calculated under D 2d point symmetry assumption. Two main methods are used in the calculation to study the SH parameters: one is the perturbation theory method and the other is the complete diagonalization (energy matrix) method (CDM). Comparing the calculated results with the experimental data, we can see that the CDM is more effective to calculate the SH parameters. In addition, the CF J-mixing of all excited-state multiplets into the ground-state multiplet 2F7/2 is considered. The validity of the calculated results is discussed. 相似文献
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Tetsu Ito Wataru Shichi Yoshie Nishioka Masao Ichida Hideki Gotoh Hidehiko Kamada Hiroaki Ando 《Journal of luminescence》2008,128(5-6):865-867
The dependence of electron spin g-factor on magnetic field has been investigated in GaAs/AlGaAs quantum wells. We have estimated the electron g-factor from spin precession frequency in time-resolved photoluminescence measurements under a magnetic field in different configurations; the magnetic field perpendicular (g⊥) and parallel (g∥) to the quantum confinement direction. When the angle between the magnetic field and the confinement direction is 45°, we have found that g-factor varies depending on the direction of magnetic field and the circular polarization type of excitation light (σ+ or σ?). These dependences of g-factor exhibit main features of Overhauser effect that nuclear spins react back on electron spin precession. The value of g⊥ and g∥ corrected for the nuclear effects agree well with the results of four-band k·p perturbation calculations. 相似文献
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G. Mennenga L.J. de Jongh W.J. Huiskamp J. Reedijk 《Journal of magnetism and magnetic materials》1984,43(1):13-20
Specific heat data on the random mixtures FepCo1-pL6(ClO4)2, where L = C5H5NO, are presented. The Fe and Co magnetic atoms have competing anisotropies since the pure Fe and Co compounds are known to be good examples of the simple cubic, , Ising and XY magnet, respectively. The experimental data show the two magnetic subsystems in the mixtures to be almost completely decoupled, which is a consequence of the fact that the crystal field anisotropies of the Fe2+ and Co2+ ions, yielding g∥ ? g⊥ and g⊥ ? g∥, respectively, are very strong compared to the magnetic exchange interactions. Consequently the two magnetic subsystems experience one another as nonmagnetic impurities. A model is presented which explains these results, as well as those previously found for related random mixtures, in terms of two interpenetrating percolation clusters. 相似文献
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The local structure of the Cu2+ centers in alkali lead tetraborate glasses was theoretically studied based on the optical spectra data and high-order perturbation formulas of the spin Hamiltonian parameters (electron paramagnetic resonance g factors g∥, g⊥ and hyperfine structure constants A∥, A⊥) for a 3d9 ion in a tetragonally elongated octahedron. In these formulas, the relative axial elongation of the ligand O2? octahedron around the Cu2+ due to the Jahn–Teller effect is taken into account by considering the contributions to the g factors from the tetragonal distortion which is characterized by the tetragonal crystal-field parameters Ds and Dt. From the calculations, the ligand O2? octahedral around Cu2+ is determined to suffer about 19.2% relative elongation along the C4 axis of the alkali lead tetraborate glass system, and a negative sign for A∥ and a positive sign for A⊥ for these Cu2+ centers are suggested in the discussion. 相似文献
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Two linear-chain compounds of formula CoCl2L2, with L = pyrazole (pz) and indazole (indz), have been investigated with the aid of IR, far-IR, ligand field and ESR spectra. Magnetic susceptibility data have been collected in the temperature region 4.2–80 K. Analysis of the susceptibility data in terms of the Ising model yielded the values of the ferromagnetic intrachain exchange constants J = 7.2(6) and 7.4(9) cm-1 for the pz and indz compound, with corresponding g-values of g∥ = 7.9(7), g⊥ = 4.6(9) and g∥ = 10.8(9), g⊥ = 3(1), respectively. The results are discussed and compared with the similar compound CoCl2(pyridine)2. The influence of the bridge geometry and of the π-bonding properties of the organic ligands on the exchange constant are considered for the explanation of different J-values. It is suggested that the π-bonding properties of the organic ligand influence the magnitude of the superexchange constant to a great extent. 相似文献