四角或三角畸变立方晶场中(3d)1过渡金属离子的劈裂因子

对四角或三角畸变立方晶场中的(3d)¹离子,在已有的静电晶场理论的基础上,采用“集团模型”,进一步引入Γ_∥, Γ_⊥及K_∥, K_⊥,R_∥, R_⊥,并考虑E_g混入T_2g,导出适用于四角或三角畸变立方晶场各种可能情况的g_∥, g_⊥公式。讨论了g_∥, g 关键词：     

Mo-SiO2-C3H6催化反应体系的ESR动态表征

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C_4v扰动程度的尺度。     

关于辐射在双麦克斯韦等离子体中散射的结构因子

文献[1]在计算双麦克斯韦等离子体的辐射散射结构因子的时候,区分T_⊥≥T_∥和T_⊥≤T_∥两种情况,得到两个不同形式的解析表达式。本文指出,区分这两种情况是没有必要的,可以得到具有更高精确度的统一解析表达式。 关键词：     

非线性电子磁漂移波

本文采用重整化方法处理了无剪切磁场漂移近似下的非线性电子磁漂移波,并分析了它与托卡马克电子反常输运之间的关系。所得到的扩散系数D_⊥～(ω_pe(T_e/cB₀L_nk_⊥²)与现有托卡马克实验结果大致符合。 关键词：     

卷积差方法在过渡金属离子EPR谱中的应用

用卷积差方法提高EPR谱的分辨率,可以从多种过渡金属离子的迭加谱中直接测量出不同离子的波谱参数a_R、a_⊥、g_R和g_⊥,该方法还可提高各向异性g因子的测量精度.     

三角畸变立方晶场中d2离子的吸收光谱

用不可约张量方法,由广义Wigner-Eckart定理得出两个推论及有关结果。对三角畸变立方晶场中的d²离子,提出了从统一模型出发,计入V_c及(V_tr+H_s)产生的所有可能的相互作用,全面处理光谱与D,g_‖,g_⊥问题的有效方法。应用于钒刚玉,通过全面拟合光谱与D,g_‖,g_⊥实验值,得到的结果与实验值满意地符合。对所用的模型、方法等问 关键词：     

七种离子注入砷化镓的射程统计参数计算

采用逐级校正法数值求解LSS方程,计算了Be⁺,N⁺,Ne⁺,Mg⁺,Si⁺,Ar⁺,Cr⁺共七种离子注入到砷化镓靶中的射程统计参数R_p,△R_p,R_⊥提出了计算R_p,△R_p,R_⊥时简单的初值计算公式,既可避免能量零点发散,并有足够的计算精度。所提出的β积分表式,可大大节省机器计算时间。所使用的数值方法和计算程序也适用于其它离子注入到其它靶材料的计算。 关键词：     

三角对称晶场下d8电子组态的EPR参量的普遍公式及其应用

本文考虑到d⁸电子组态中所有自旋三重态和自旋单态对基态的影响,用高阶微扰法导出了d⁸电子组态在三角对称晶场下光谱和基态EPR普遍公式。发现在三角对称晶场下,d⁸电子组态离子的g_⊥ > g_‖或g_⊥ < g_‖和D > 0或D < 0是以立方对称晶场为界,晶体中顺磁离子的配体沿C₃轴伸长或压缩所致。利用所得公式计算了NiCl₂和NiSiF₆·6H₂O晶体的EPR参量,其结果与实验吻合较好。     

A-15超导化合物的d带相对移动模型

本文考虑了A₃B型A-15结构晶体场的特点,根据对势模型,求出A原子各d电子子能级间相对移动量△E_⊥,进而在LCAO方法基础上,提出了改进的RCA能带模型。并据此得到V₃B系化合物超导临界温度对△E_⊥的关系,理论曲线与实验数据大致相符。 关键词：     

Orientation-dependent electromagnetic properties of basalt fibre/nickel core--shell heterostructures

The influence of orientation on electromagnetic properties of basalt fibre/nickel core--shell heterostructures prepared by a simple electroless plating method is investigated. For comparison, the same investigation is also performed on naked basalt fibres. For electromagnetic measurement, the directions of basalt fibre/nickel and naked basalt fibres are parallel, random and perpendicular to the direction of external electric field, termed E_\vert\vert sample, random sample and E_⊥ sample, respectively. Electromagnetic anisotropy can be clearly observed in the basalt fibre/nickel core--shell heterostructures, while electromagnetic properties of naked basalt fibres are unrelated to the orientation. The E_⊥ basalt fibre/nickel shows the highest dielectric loss but the lowest magnetic loss, and E_|| basalt fibre/nickel exhibits the highest magnetic loss but the lowest dielectric loss. The dielectric loss of E_⊥ basalt fibre/nickel is several times as large as that of E_|| basalt fibre/nickel, which could be attributed to the increase of polarization relaxation time as a consequence of the nanosize-confinement effect. The magnetic loss of E_|| basalt fibre/nickel is even one order of magnitude higher than that of E_⊥ basalt fibre/nickel, which originates mainly from the natural magnetic resonance of basalt fibre/nickel core--shell heterostructures.     

Spectra of negative particles and photons in collisions of p−W and16O−W at 200 GeV/u

p _⊥ spectra of negative particles were measured for p?W and¹⁶O?W collisions at 200 GeV/u in the rapidity range 0.9<y<1.9. Within the systematic errors of 20% the spectra are identical in the range 0.05<p _⊥<2.0 GeV/c. The p?W and¹⁶O?W spectra exhibit an exponential shape forp _⊥ >250 MeV/c. This is consistent with previous p?A data, but there is a significant excess above this exponential at lowerp _⊥. Photon spectra were measured using a conversion method. Theirp _⊥ distribution agrees in shape with the sum of known hadronic γ-sources.     

Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

Invariant cross-sections are presented for the inclusive reaction p + p → π^o + anything, Measurements of large transverse momentum π^o's (2.5 GeV/c<p_⊥<9 GeV/c) were made near 90° at the CERN ISR at five centre-of-mass energies (√s = 23.5, 30.6, 44.8, 52.7 and 62.4 GeV. At large p_⊥, the invariant cross-sections are seem to vary with s and p_⊥, in good agreement with a fit of the form Ap_⊥^?nF(p_⊥/√s), with n≈8 and F(p_⊥/√s)≈exp(?26p_⊥/√s).     

Low-frequency dispersion of the effective transverse conductivity in inhomogeneous media in strong magnetic field

On crystalline silicon specimens with a nonuniform carrier concentration distribution produced by an optical method, a dispersion of the effective transverse conductivity σ _⊥ ^eff (ω) is observed near the frequency ω≈ω_c=τ _⊥ ^?1 ≡ε/4πσ _⊥ ^eff . At ω<ω_c, an anomalous transverse effective conductivity is observed: σ _⊥ ^eff (ω) is greater than the transverse conductivity of a homogeneous specimen σ _⊥ ^h (ω) (in the frequency range studied in the experiment σ _⊥ ^h (ω) = const). Near ω≈ω_c, the conductivity σ _⊥ ^eff decreases, and, at ω>ω_c it coincides with σ _⊥ ^h .     

Transverse momentum of muon pairs produced in hadronic collisions

The observed p_⊥ distributions of large mass muon pairs produced in proton-nucleus collisions are quantitatively explained in QCD by also explicitly taking into account the intrinsic wave function p_⊥ spread of partons inside the hadrons. The experimental data indicate 〈p_⊥〉 ～ 500–600MeV for each parton.     

Exact solution for the extended Debye theory of dielectric relaxation of nematic liquid crystals

The exact solution for the transverse (i.e. in the direction perpendicular to the director axis) component α_⊥(ω) of a nematic liquid crystal and the corresponding correlation time T_⊥ is presented for the uniaxial potential of Martin et al. [Symp. Faraday Soc. 5 (1971) 119]. The corresponding longitudinal (i.e. parallel to the director axis) quantities α_⊥(ω), T_⊥ may be determined by simply replacing magnetic quantities by the corresponding electric ones in our previous study of the magnetic relaxation of single domain ferromagnetic particles Coffey et al. [Phys. Rev. E 49 (1994) 1869]. The calculation of α_⊥(ω) is accomplished by expanding the spatial part of the distribution function of permanent dipole moment orientations on the unit sphere in the Fokker-Planck equation in normalised spherical harmonics. This leads to a three term recurrence relation for the Laplace transform of the transverse decay functions. The recurrence relation is solved exactly in terms of continued fractions. The zero frequency limit of the solution yields an analytic formula for the transverse correlation time T_⊥ which is easily tabulated for all nematic potential barrier heights σ. A simple analytic expression for T_∥ which consists of the well known Meier-Saupe formula [Mol. Cryst. 1 (1966) 515] with a substantial correction term which yields a close approximation to the exact solution for all σ, and the correct asymptotic behaviour, is also given. The effective eigenvalue method is shown to yield a simple formula for T_⊥ which is valid for all σ. It appears that the low frequency relaxation process for both orientations of the applied field is accurately described in each case by a single Debye type mechanism with corresponding relaxation times (T_∥, T_⊥).     

Diffusion in thermotropic liquid crystals

Diffusion coefficients in mesophases of thermotropic liquid crystals have been measured to a considerable extent only during the last twelve years. Some theories on diffusion in mesophases have been developed too. Measurements in nematic, smectic A, smectic B, and smectic C mesophases have been carried out by mass transport techniques, detected by radio-tracers or optically, by NMR spin-echo techniques, and by quasi-elastic neutron scattering. The diffusion is anisotropic in most of the cases. In nematics self-diffusion parallel to the molecular director (D₆) is somewhat faster than perpendicular (D_⊥). Both diffusion coefficients show about the same activation energy. Impurity diffusion (small molecules dissolved in mesophases) demonstrates the same behaviour with less anisotropy. In smectics A and C the diffusion coefficients D₆ and D_⊥ can be nearly equal. The anisotropy is now shown in their respective activation energies with E₆>E_⊥. This effect is more pronounced in impurity than in self-diffusion. In addition impurity diffusion shows a strong anisotropy of the diffusion coefficients (D_⊥?D₆). In smectics B the activation energies E₆ and E_⊥ of self-diffusion seem again to be equal and the diffusion coefficients show a small anisotropy (D_⊥≥D₆).     

Evidence for planar events and a forward double jet structure in deep inelastic Muon scattering

The final states of charged hadrons produced in 280 GeV μp scattering are analysed with respect to their planarity and jet structure. Distributions of p_⊥² in and p_{⊥ out}² are presented. A two jet structure in the forward hemisphere is observed for events with high p_⊥ tracks are predicted by QCD models.     

Supersymmetric enhancement factor for the 1-jet cross-section inp - \bar p reactions

We compare the 1-jet inclusive cross-section at highp _⊥ in proton-antiproton reaction atSPS collider predicted by standard QCD and by its simplest supersymmetric extension (SQCD). We first compute the total enhancement factorK between QCD and SQCD jets as a function ofp _⊥. Then we compute the observable enhancement factor which is smaller thanK since the transverse momentum of supersymmetric particles is not fully observable. We have analyzed two cases (i)p _⊥ is small compared to the masses of squarks and only light gluinos (2 GeV) are considered (ii)p _⊥ is large compared to the masses of squarks (17 GeV in our analysis) and both gluinos and squarks are taken into account. The observable enhancement factor between QCD and SQCD is found to be small (of order 1.3 to 1.5 forp _⊥=100 GeV). Missingp _⊥ events with one ordinary jet and one jet due to the production of a supersymmetric particle are found to be non negligible with respect to those with two supersymmetric jets. We also display some interesting supersymmetric relations among parton cross-sections.