MgF2:Mn2+光谱、超精细常数和局部结构的关联

基于电子顺磁共振(EPR)超精细常数A_s确定键长的新方法和半自洽场d轨道理论，对MgF₂:Mn²⁺光谱和EPR超精细常数作出了统一解释.得到室温下MgF₂:Mn²⁺晶体中杂质中心Mn—F的键长为0.2124±0.0010nm. 关键词： 晶体场 电子顺磁共振 光学和磁学性质     

MgF2:Mn2+合成及发光

本文首次报导了采用碱式碳酸盐和氟化铵一步合成MeF2:Mn2+长余辉材料新方法。研究了各种条件和Mn2+浓度对荧光粉的影响,所得到的MgF2:Mn2+发射为橙红色,主峰在590nm,色度值为x=0.559,y=0.438,余辉大约200ms。荧光粉呈现均匀圆球状的颗粒,属于四方晶系。     

锌磷酸盐玻璃掺杂VO~(2+)吸收光谱和EPR谱研究

3d1离子(如VO2+,V4+)是一类非常重要的离子,其掺杂电子顺磁共振谱已有大量的研究,积累了丰富的实验数据。利用3d1离子在四角压缩八面体对称中EPR参量的高阶微扰公式,计算了锌磷酸盐玻璃晶体中掺杂VO2+的EPR参量(g因子g‖,g⊥和超精细结构常数A‖,A⊥)和光吸收谱。由于锌磷酸盐玻璃晶体中掺杂VO2+中配体O2-的自旋-轨道耦合参量ζ0p(≈150cm-1)与中心过渡金属3d1离子V4+的ζ0d(≈248cm-1)相差不太大,故来自配体的自旋-轨道耦合参量ζ0p对EPR参量和光吸收谱的贡献必须予以考虑。采用重叠模型建立了杂质中心结构参数与电子顺磁共振(EPR)参量以及光吸收谱之间的定量关系;通过拟合锌磷酸盐玻璃中V4+中心的EPR参量和光吸收谱理论与试验符合,获得了杂质中心[VO6]8-基团的局域结构;研究发现,[VO6]8-基团的平行和垂直于C4轴的键长分别为:R‖≈0.175nm,R⊥≈0.197nm,即[VO6]8-基团的局域结构为沿C4轴方向呈压缩的八面体结构;所得EPR参量和光吸收谱的理论值与实验符合很好,并对上述结果的合理性进行了讨论。这说明微扰法可以用来研究材料中掺杂3d1过渡金属离子的EPR参量和光吸收谱。此外,对超精细结构常数(A‖和A⊥)的研究发现,较大的芯区极化常数κ值说明VO2+中未配对的s电子对超精细结构常数有较大的贡献。     

用EPR谱研究ZnS:Mn、Cu的Mn2+团形成和它对发光特性的影响

Mn2+浓度C(0.5%,0.6%)相同,而煅烧温度不同的DCEL ZnS:Mn、Cu粉未样品的EPR谱是不同的.用微机模拟EPR谱,计算出Mn2+团所占Mn2+的比例Cc/C.煅烧温度低于950℃时,Mn2+团比例随锻烧温度升高而减少,煅烧温度高于950℃时,六角晶相比例和Mn2+团比例同时随锻烧温度的升高而增加.分析表明,六角晶相有利于Mn2+间的间接电子自旋交换作用,在相同的掺Mn、Cu浓度条件下,对比立方晶相,它将使更多的Mn2+形成团,使材料的发光亮度降低.文中还讨论了锻烧DCEL ZnS:Mn、Cu材料的最佳温度问题.     

Mn2+在CoSiF6·6（H2O）:Mn2+体系中EPR谱的理论研究

本文采用对角化三角场中d5电子组态的完全能量矩阵的方法,并同时考虑EPR的二阶参量D和四阶参量(a-F),研究了Mn2+在CoSiF6.6(H2O)体系的局域结构畸变.结果表明:在CoSiF6.6H2O:Mn2+体系中,Mn2+取代了Co2+离子后整个晶体显示出伸长畸变,并且其结构参数R=2.260,θ=52.5192°被确定.     

Mg~(2+)掺杂锰酸锂的第一性原理研究

利用基于密度泛函理论的第一性原理平面波超软赝势法对Mg~(2+)掺杂锰酸锂的晶格常数与能带结构、态密度、键布居进行计算和分析,计算结果表明:掺杂Mg~(2+)后将会促使Mn、 O原子的电荷重新分布且其相互作用加强,能带带隙减小,费米能级附近的带数增加,费米能由-1.29 eV增加到-1.02 eV, Mn、 O、 Mg在总态密度中贡献比较大,锂离子贡献比较小且峰型尖锐局域化严重,提高了Li~+的扩散效率, Mn—O键变短,共价性增强,形成的共价键较稳定,其相互作用形成的骨架较稳定不易坍塌.从而提高了材料的循环充放电性能和电池使用寿命.     

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．     

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.      

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.     

ZnS∶Mn2+与ZnS∶Fe3+体系的基态零场分裂理论研究

在ZnS晶体中掺入Mn2 + 或Fe3 + 离子的EPR谱已得到了广泛的研究 .然而 ,理论结果显示其EPR零场分裂的计算值远小于实验观察值 ,这一理论与实验的矛盾至今仍未得到满意的解决 .假定在四面体ZnS中 ,S原子在成键时采取了sp3 杂化轨道的形式 ,从而使S离子显示出正的有效电荷 .从这一观点出发 ,通过对角化三角场中的微扰能量矩阵 ,使得ZnS∶Mn2 + 和ZnS∶Fe3 + 体系的EPR零场分裂参量α ,D和 (a -F)的实验值都能得到满意的解释. The EPR spectra of Mn 2+ and Fe 3+ ions in ZnS∶Mn 2+ and ZnS∶Fe 3+ systems have been extensively studied. However, the theoretical results show that the calculation values of the zero-field splitting are always much less than those of the experimental findings. Up to now, this difficulty has not yet been satisfactorily removed. In present paper, we assume that the sulfur ion has a sp 3 hybrid configuration in tetrahedral ZnS, so that the sulfur ion displays a positive...     

Microwave spectrum of 2-aminopyridine

The microwave spectra of 2-aminopyridine-NH₂, -ND₂, and of both of the two possible -NHD molecules have been observed and assigned in the 0⁺ vibrational state of the amino group inversion vibration; the assignment for three of the molecules in the 0⁻ state is also made. From intensity measurements the 0⁺-0⁻ splitting is estimated to be 135 ± 25 cm⁻¹ for the -NH₂ molecule and 95 ± 30 cm⁻¹ for the -ND₂ molecule. The rotational constants are interpreted in terms of a structure in which the amino group is bent about 32° out of the molecular plane, the c coordinates of the two amino H atoms being 0.21 and 0.28 Å. Stark effect measurements give a dipole moment of about 0.9 D which is almost entirely in the b axis, and which changes quite significantly between the 0⁺ and 0⁻ states.     

Microwave spectrum of 2-chloropyridine

The microwave spectrum of 2-chloropyridine, C₅H₄NCl, has been studied in the frequency range from 26.5–40.0 GHz. The spectrum is characterized by strong parallel type transitions of a near-prolate asymmetric top. The assigned transitions have been used to evaluate the ground state rotational constants of the two chlorine isotopes. The rotational constants are (in MHz): A = 5872.52, B = 1637.83, C = 1280.48 for the ³⁵Cl isotopic species and A = 5872.16, B = 1591.76, C = 1252.17 for the ³⁷Cl isotopic species. The small inertial defect indicates the molecule is planar. In addition an excited vibrational state of C₅H₄N³⁵Cl has been observed and analyzed. The chlorine quadrupolar coupling constants were determined for the ground state and are: χ_aa = ?71.9 MHz for ³⁵Cl and χ_aa = ?54.9 MHz for ³⁷Cl. By assuming the pyridine ring structure the CCl bond length is found to be 1.72 Å.     

Microwave spectrum of NF2

About 350 lines in the microwave spectrum of NF₂ have been measured in various ranges of frequency between 13.0 and 65.2 GHz by using two types of Zeeman effect spectrometers. Complete assignment of all lines has been achieved and, via the general microwave computer program SPINRO, the rotational constants, centrifugal distortion constants, dipole moment, electronic spin-rotation coupling constants, the constants for the coupling of the several nuclear spins with the electron spin and the nitrogen quadrupole coupling constants have all been obtained.By drawing upon the observed vibrational frequencies the average geometry of NF₂ has been evaluated. Force constants and Coriolis coupling constants have also been derived.The values of the spin coupling constants for N and for F indicate that NF₂ is a π-radical with the spin density mainly located on nitrogen. The multiplet patterns indicate that the ground electronic state wavefunction is antisymmetric to rotation about the molecular symmetry axis and so, for a π-radical, identifies the ground state as ²B₁ as has previously been assumed for this molecule.     

H2S和H2S+的振动光谱和电子能谱计算

本文基于MOLPRO软件包使用从头算方法计算了星际分子H₂S及其阳离子H₂S⁺的势能面及光电子能谱.首先,在(U)CCSD/cc-pVQZ理论水平下获取了H₂S沿法线坐标展开的势能面,势能面直观描述了不同振动模式耦合对分子能量变化的影响,S-H键的非对称伸缩振动和面内弯曲振动共同作用使得系统势能变化范围明显变大.振动多组态相互作用方法被用来计算非谐振动频率和振动光谱,计算结果显示,倍频和组合频之间出现了强烈的费米共振,使得相应波段处的红外强度显著增强.最后,使用拉曼波函数和收缩不变Krylov子空间方法首次计算了H₂SΧ¹A₁→H₂S⁺ X²B₁的光电子能谱.此项研究有助于进一步理解星际分子的内部结构,并为实验研究及星际观测提供参考.     

The rotational spectrum of 2-indanone

The rotational spectrum of 2-indanone has been analysed in the 26.5-40 GHz frequency region. The ground state, the first five excited states of the five-membered ring bending mode and the first excited state of the ring twisting and butterfly modes have been assigned and analysed. From the ground state inertial defect and the variation of the rotational parameters with the ring bending quantum number a strictly planar C2v equilibrium conformation has been established. A one-dimensional potential function of the quadratic-quartic type V(X) = 3.3(7) (X4 + 11.66(15)X2)cm-1 has been derived for the bending vibration.     

The millimeter-wave spectrum of 2-cyanoethanol

In order to better characterize the chemistry involving CN groups in regions of star-formation, we have recorded the millimeter-wave rotational spectrum of 2-cyanoethanol. Almost 6000 new transitions were assigned to two separate conformers and three torsionally excited states. The lowest energy conformer, gauche-2-cyanoethanol, its 1st excited torsion, and the ground state for the anti-I-conformer are best characterized with basic asymmetric rigid-rotor Hamiltonians including distortion. All fit close to experimental uncertainty. Fits for the 2nd and 3rd excited torsional states for the gauche-conformer are of somewhat lower quality, which might be explained by a potential interaction between these states. The results of the various fits are discussed in this paper. In all, the present characterization of the spectrum and extensions through prediction should be more than sufficient to guide future millimeter-wave observational studies of this species in the interstellar medium.     

The photoelectron spectrum of CSe2

The He I photoelectron spectrum of CSe₂ has been recorded and four of the bands observed assigned to ionization from valence shell levels that correlate well with those found for CO₂ and CS₂. Weak bands in the spectra of CS₂ and CSe₂ are assigned to shake-up processes in which electronic excitation of the ion accompanies ionization.     

Second order Raman spectrum of MoS2

The second order Raman spectra of a layer compound MoS₂ have been measured. Features characteristic of a two-dimensional phonon density of states curve have been observed. Most of the critical points in the second order spectrum are identified.     

The microwave dispersion spectrum of O2

The microwave dispersion spectrum of O₂ at 298 K and at various densities up to 1 atmosphere is calculated employing R. G. Gordon's expression for the magnetic dipole absorption spectrum. Good agreement with available refractivity measurements is obtained, indicating (as do theoretical considerations given in the Appendix) that the Kramers-Kronig relations are obeyed to a good approximation at the pressure and frequency ranges investigated.