六参数高精度双原子分子解析势能函数

提出一种构造解析势能函数的新方法,得到一种六参数解析势能函数,该势能函数适用于多种基本类型的双原子分子.用同核中性基态双原子分子Li₂-X¹Σ_g⁺、Na₂-X¹Σ_g⁺,异核带电基态双原子分子离子(BC)^--X³∏,异核中性激发态双原子分子PbS-A¹Σ⁺、BaO-A¹Σ,异核带电激发态双原子分子离子(CS)⁺-A²∏,同核中性激发态双原子分子K₂-B¹∏_u,同核带电激发态双原子分子离子N₂⁺-B²Σ_u⁺等共36个算例对该势能函数进行验证,计算结果与RKR(Rydberg-Klein-Rees)数据或振动能谱实验数据高精度符合.同时发现,在分子振动能谱计算精度方面,该势能函数总体上优于Murrell-Sorbie势能函数.     

α-碘酸锂的电流弛豫和偏压场作用下表观介电常数弛豫行为

本工作较为详细地测定了静电场作用下α-碘酸锂的电流弛豫行为:在撤去c轴方向上的静电场后,从我们所用测量电流仪器的响应时间到某一t_k的区间内,放电电流服从(t/t₀)^-α的负幂次方律;而在t>t_k,其规律近似地为:(t/t₀)^{(-α′ln(t/t₀))}。相关的弛豫参数α,α′和t_k在有限的范围内,依赖于温度和施加电压的大小,也因样品不同而有差异。对将近十个样品进行了测试,结果表明,大多数晶体在尽可能小的电压下0.43≤α≤0.7,0.07<α′<0.09;上述的电流弛豫表达式与α-碘酸锂在偏压场作用下观察到的其它物理现象的弛豫行为,与在中子衍射加强和表观介电常数中的表现如出一辙;可以初步肯定各种现象的弛豫行为具有相同的物理根源。 关键词：     

Au(110)表面结构和氧原子吸附的第一性原理研究

用密度泛函理论(DFT)研究了金属Au(110)表面结构以及氧原子的吸附状态.计算得到Au(110)-(1×2)缺列再构表面原子的弛豫分别是-15.0%(Δd₁₂/d₀)和-1.1%(Δd₂₃/d₀),表面能为52.7 meV/²,功函数Φ=5.00 eV;Au(110)-(1×3)缺列再构表面的Δd_{1 关键词： 缺列再构Au(110)表面 STM图像 氧原子吸附}     

邻苯二甲酸二甲酯系材料中α-弛豫的降温介电谱测量与分析

对邻苯二甲酸二甲酯(dimethyl phthalate)、邻苯二甲酸二乙酯(diethyl phthalate)、邻苯二甲酸二丁酯(dibutyl phthalate)和邻苯二甲酸二异辛酯 (dioctyl phthalate)系列材料中, α-弛豫的降温介电谱进行了测量, 得出了相应材料α-弛豫的平均弛豫时间τ_α^a 随温度T的变化关系. 通过τ_α^a 的实验结果与经验的Vogel-Fulcher-Tammann)定律τ_α^a = τ_α⁰ exp (A/(T-T₀))的拟合, 获得了上述系列材料的τ_α⁰, A和T₀. 分析发现, 随邻苯二甲酸二甲酯系列分子侧链中碳原子数目n的变化, 材料的τ_α⁰, A, T₀ 和T_g 表现出一定的规律性, 具体为随n的增加, 即分子内部自由度的增多, A和T_g 都表现出近乎相同的先减后再增的趋势, 而1/τ_α⁰ 和T₀ 则表现出基本相同的先快速减小, 然后保持基本上不变的趋势. 关键词： 玻璃化转变 介电谱 α-弛豫')" href="#">α-弛豫 邻苯二甲酸二甲酯系列材料     

HfV2·Hx中扩散导致的1H核自旋弛豫 近邻无规行步处理

对氢合金HfV₂·H_x中¹H核自旋弛豫起主导的因素是偶极相互作用,研究的核心是如何理论计算¹H在基质晶格中扩散造成偶极相互作用涨落的谱密度。我们把Torrey同核偶极作用近邻无规扩散行步理论推广到同核、异核偶极作用并存的情况;并就中子衍射提供的HfV₂·H_x结构(C-15)参数计算了确定谱密度J_q^HH(ω)和J_q^HV(ω)(q=0,1,2)所需的G_HH(k,y)和G_HV(k,y)。引用以前别人的核磁共振实验数据,依照我们的理论分析计算扩散激活能和H在间隙位上的振动频率;与他们用唯象理论获得的相应数值对比,结果是满意的。 关键词：     

玉米胚芽胚乳中油水动态行为的NMR研究

应用核磁共振时域二维弛豫相关谱分析的方法,对玉米胚芽的核磁共振弛豫特性进行了研究.对以下三种样品进行了测定:(1)胚芽不含油(用化学方法蒸馏出)但是含有不同百分含量的水;(2)胚芽不含水(真空蒸发)但是含有不同百分含量的油;(3)含有不同百分含量的水的胚乳水系统.研究表明随着水含量的增加水的纵向弛豫时间T₁减小,表明水与胚芽基质具有强烈的相互作用,而油的纵向弛豫时间T₁随着油含量的增加变化很小,表明油与胚芽基质之间没有大的相互作用,油几乎独立地处在胚芽中;对低水分(少于5%)玉米胚芽水系统,结果表明水是束缚于胚芽基质上,而油则是以油胞的形式存在于胚芽中.在玉米胚芽水系统中有两个T₁弛豫成分,长T₁弛豫成分从基质到水的交换率为57s^-1;从水到基质的交换率为113s^-1.短T₁成分从基质到水的交换率为245s^-1;从水到基质的交换率为821s^-1.在低水合状态下,胚乳水系统仅有一个T₁弛豫成分.胚乳到水的交换率高于37s^-1.     

1+1维和2+1维空间上定向聚合问题的数值研究

对1+1和2+1维空间上定向聚合问题的数值模拟结果显示,任意有限温度下的横向涨落和自由能涨落在聚合尺度t较大时都将趋于零温度时强耦合下的结果:Δx∝t^ν和ΔF∝t^ω(d=1+1时,ν=2/3,ω=1/3;d=2+1时,ν≈0.6,ω≈0.2).有限温度下,由于1+1维和2+1维空间上的比热C(T,t)∝t和1+1维空间上的熵涨落ΔS∝t^1/2,1+1维空间上的系综能量涨落和内能涨落以及2+1维空间上的系综能量涨落均趋于t^1/2而远强于自由能涨落.在2+1维空间上,定向聚合问题有发生相变的迹象:当熵涨落达到其最大值时,单位聚合尺度的熵涨落和内能涨落在聚合尺度t→∞时,可能会由低温下趋于有限值(零温度除外)转变为高温下趋于零 关键词： 定向聚合 表面生长现象 Kardar-Parisi-Zhang方程     

直流偏置电场下BaTiO３基陶瓷介电常数非线性机理的研究

采用传统固相法制备了Ba_0.6Sr_0.4TiO_３(BST)和BaZr< sub>xTi_１-xO_３(x=0.25，0.3，0.35，0.4)（ＢＺＴ）陶瓷 ，并对其在直流偏置电场下的介电常数非线性行为进行了系统、详细的研究.结果表明，基 于Devonshire的宏观相变理论(phenomenological theory)提出的公式ε_r(app) ε_r(0)=1［1+αε^{３_{r(0)E２ ］1/3和ε(E)=ε1－ε2E2+ε3E4，均可定量地解释BST体系顺电相的介电常数非线性行为，其中εr (app)表示材料在电场下的介电常数，εr(0)表示不加电场即静态下材料 的介电常数，α是非谐性因子，E表示电场强度，ε(E)表示材料在电场下的介电常数，ε１，ε２，ε３分别表示线性、非线性和高阶介电常数. 而对于处于铁电相和居里温度附近的BST体系，则需要考虑铁电畴对介电常数非线性的贡献 ，这种贡献随着外加直流偏置电场强度的增大逐步减小.对于弛豫铁电体BZT体系，即使处于 顺电相，也必须考虑由极性微区的冻结与合并引起的介电常数的下降，极性微区对介电常数 非线性的贡献随着电场强度和温度的上升而有所下降. 关键词： BST x}Ti_１-xO_３')" href="#">BaZr_xTi_１-xO_３ 可调性 介电 常数非线性 直流偏置电场}     

内壳层电子激发(电离)诱发的电子波函数的弛豫及其对辐射跃迁概率的影响

利用多组态Dirac_Fock(MCDF)理论方法，通过对Ar原子在基组态3p⁶和激发组态1s^-14s，2s^-14s，2p^-14s，3s^-14s，3p^-14s情况下电子波函数的计算，系统地研究了不同内壳层电子激发(或电离)引起的电子波函数的弛豫现象以及由此导致的k_α和k_β线的跃迁波长和概率的变化情况，并与以往的理论结果进行了比较. 关键词： MCDF方法 弛豫效应 电子波函数 跃迁概率     

Belle实验ϒ(5S)数据中新类底偶素态的寻找

Belle实验组利用在ϒ (5S)共振峰上采集的大数据样本,对e⁺e^－→π⁺π^－ϒ (nS)和π⁺π^－h_b (mP) (n=1,2,3,m=1,2)过程进行了研究,在π^±ϒ (nS)和π^±h_b(mP)的系统中,同时观测到了两个新的带电类底偶素结构——Z_b(10610)和Z_b(10650)。它们衰变到底偶素末态,同时还带有电荷,所以它们的组成成份中至少含有4个夸克。最近,对e⁺e^－→π⁺π^－π⁰ γ ϒ (1S)过程也进行了研究,在ωϒ (1S)系统中对类X(3872)的底偶素态X_b进行了寻找。     

激发态极化效应的修正模型

本文考虑到极性晶体中不同的热释电过程以及辐射跃迁中平均发射频率ν₂与电子跃迁频率ν₃的差异(斯托克斯位移),提出了激发态极化效应的修正模型。根据该模型及不同作者利用不同激发光源在不同实验条件下对厚度不同的LiNbO₃:Cr³⁺晶体样品所得的实验结果,计算了该晶体中Cr³⁺离子激发态的偶极矩改变△μ。在实验误差范围内,由不同的实验数据算得的△μ完全一致:△μ约为3Debye;在整个实验温度区间(50—300K)内,△μ几乎与温度无关。 关键词：     

Hafnium binding to rat serum transferrin

Using the TDPAC-technique binding parameters for Hf were determined afterin vivo uptake of¹⁸¹Hf in rat plasma. As much as 98.5% of the metal ions proved to be bound to protein, essentially to transferrin. The main fraction of the¹⁸¹Hf ions experiences a well defined electric quadrupole perturbation frequency (vQ1=(1516 ± 15)MHz, δ₁=(5.3 ± 0.8)%) connected with a marked relaxation damping (λ = (46 ± 8)MHz). The remaining Hf nuclei are subject to a fairly broad distribution of electric field gradients (v_Q2=(1014 ± 37)MHz, δ₂=(16±3)%). The results are compared with data obtained within vitro ¹⁸¹Hf-labeled human transferrin.     

无扩散相变中界面动力学的唯象理论及其应用

固态相变中相界面或畴界面的平均运动速度V与有效相变驱动力△G＇(相变驱动力△G与相界面运动阻力△G_R之差)之间的关系可表示为V=φ(△G—△G_R)。当有单向变化的外场(场强为ξ,变化速率为ξ)作用于相变系统并能诱导相界面运动时,就会产生母相/新相间的转变。在相变过程中同时叠加一个交变应力时,则可计算得界面动力学关系V=φ(△G—△G_R)与相变过程内耗Q^-1、相关的模量亏损(△M/M)、相变速率dF/dξ、相变应变ε₀间的关系为 [d lnφ(△G-△G_R)/d(△G-△G_R)]= Q^-1ω/n²M(dF/dξ)ξ = (△M/M)ω/nMε₀(dF/dξ)ξ, 以及 (△M/M)/Q^-1=ε₀/n。此处ω为交变应力的圆频率,M为与振动模式有关的弹性模量,n为应力与界面运动的耦合因子。因此,界面动力学关系式的通解为 V = ∑(±n)/(α≠-1) A_α exp{[(△G-△G_R)/△G_α^*]^{α+ 1}/(α+ 1)} +∑(m)/(β₀) A_β[(△G-△G_R)/△G_β^*]^β 此处n,m为正整数。上式中的各项参数可由实验数据确定。此外,(△M/M)/Q^-1的等式还可用于判别相变过程的模量亏损中有无声子模软化的贡献。 关键词：     

Electromigration and permeation of hydrogen and deuterium in silver

A steady state flow technique was used to measure the effective charge number (Z*) and permeability (N) of hydrogen and deuterium in silver. Over the range of temperature (485–720°C) and pressure (220–750 torr) the effective charge number is a constant. The interstitial impurity migrates in the direction of the electron wind with Z_H* = ?6·8 and Z_D* = ? 18. The values of Z* are of the same order as self-electromigration but the size of the isotope effect is surprising. The quantum theories used to explain the isotope effect for hydrogen electromigration in Fe and Ni appear to fail here. In order to determine the effective charge number is was necessary to measure the permeability. For both H₂ and D₂, the permeability in silver follows the equation N = N_O exp(? Q/RT) where N_0D = 2·39 ± 0·40, Q_D = 14400 ± 300, N_OH = 2·86 ± 0·70 and Q_H = 14200 ± 500. Here Q is in units of cal/mol and N is in units of cc(ntp)/(sec - atm² - cm) The isotope effect ratio N_H/N_D = 1·25 was smaller than the classically expected value of (2)^1/2, but could be explained by the theory of Ebisuzaki, Kass and O'Keeffe.     

The ratio of the quadrupole moments of the isotopes95Mo and97Mo

The spin-lattice relaxation timesT ₁ of the NMR signals of⁹⁵Mo and⁹⁷Mo in aqueous K₂MoO₄ solutions were determined by the inversion recovery technique. To separate the relaxation rates due to electric quadrupole interaction and due to magnetic dipole interaction, pure H₂O and mixtures of H₂O and D₂O were used as solvent. No dependence of the ratio of the relaxation ratesT ₁(⁹⁵Mo)/T ₁(⁹⁷Mo) on the composition of the solvent was to be detected, i.e. the relaxation due to magnetic dipole interaction may be neglected. From the ratio of the relaxation rates the absolute value of the ratio of the quadrupole moments of the molybdenum isotopes was evaluated: ¦Q(⁹⁷Mo)/Q(⁹⁵Mo)¦ = 11.4 ±0.3.     

CH3I: Isotope shift for 129I in the v6 band

The isotope shift in the v₆ band of CH₃I has been measured with high resolution for the radioisotope ¹²⁹I (half-life = 1.6 × 10⁷ y) with respect to the stable ¹²⁷I, using tunable diode laser spectroscopy. The average shift obtained from 30 transitions, free from interference in the ^RQ(J, 3) and ^RQ(J, 4) branches, amounted to (-0.0135 ± 0.0006) cm^-1. The abundance ratio ¹²⁹I/¹²⁷I in the gas mixture was determined spectroscopically on ^RQ(16, 3) and found to be (0.032 ± 0.003), as compared to a mass-spectrometric analysis of (0.030 ± 0.001). The self and air broadening coefficients measured on ^RR(6, 0) of CH₃¹²⁷I were (32 ± 3) MHz Torr^-1 and (10.4 ± 1.5) MHz Torr^-1 respectively. The line strengths for ^RQ(16, 3) were found to be (2.0 ± 0.2) × 10^-21 cm^-1 mol^-1 cm² for both CH₃¹²⁷I and CH₃¹²⁹I.     

Mössbauer spectroscopy and DFT calculations on all protonation states of the 2Fe-2S cluster of the Rieske protein

The Thermus thermophilus Rieske protein (TtRP) contains a 2Fe-2S cluster with one iron (Fe-Cys) coordinated by four sulfur atoms (2xS^2? and 2xCys) and one iron (Fe-His) by two sulfur and two nitrogen atoms (2xS^2?, His134 and His154). Here, the protein is investigated at three pH values (6.0, 8.5 and 10.5) in order to elucidate the protonation states of the His-ligands. Examination of the effect of protonation on the electronic structure of the cluster via Mössbauer spectroscopy gives a deeper understanding of the coupling of electron transfer to the protonation state of the His-ligands. Two components (1 referring to Fe-Cys and 2 to Fe-His) with parameters typical for a diamagnetic [2Fe-2S]²⁺ cluster are detected. The Mössbauer parameters and the protonation state clearly correlate: while δ remains almost pH-independent with δ ₁ (pH6.0) =?0.23 (±?0.01) mms^??1 and δ ₁ (pH10.5) =?0.24 (±?0.01) mms^??1 for Fe-Cys, it decreases for Fe-His from δ ₂ (pH6.0) =?0.34 (±?0.01) mms^??1 to δ ₂ (pH10.5) =?0.28 (±?0.01) mms^??1. ΔE _Q changes from ΔE _Q1 (pH6.0) =?0.57 (±?0.01) mms^??1 to ΔE _Q1 (pH10.5) =?0.45 (±?0.01) mms^??1 and from ΔE _Q2 (pH6.0) =?1.05 (±?0.01) mms^??1 to ΔE _Q2 (pH10.5) =?0.71 (±?0.01) mms^??1. Density functional theory (DFT)-calculations based on the crystal structure (pdb 1NYK) (Hunsicker-Wang et al. Biochemistry 42, 7303, 2003) have been performed for the Rieske-cluster with different His-ligand protonation states, reproducing the experimentally observed trend.     

Pressure broadening of UF6 by argon

Pressure broadening of the R(6) manifold in ν₃ of UF₆ at 628.32 cm^?1 has been measured at pressures of 0–30 torr of Ar in a long-path cell at 199 ± 1 K. We obtain a pressure-broadening coefficient of 9.0 ± 1.5 MHz/torr (FWHM), which corresponds to 7.3 ± 1.2 MHz/torr at 300 K. The UF₆-Ar optical collision diameter is 7.4 ± 0.6 Å; this is larger than the hard-sphere kinetic theory collision diameter of 5.2 Å obtained from the diffusion coefficient and implies rapid rotational relaxation.     

Optical,photo-acoustic and electrical switching studies of amorphous GeS2 thin films

This paper reports optical, photo-acoustic and electrical switching investigations of GeS₂ amorphous thin films of different thicknesses, deposited on glass substrates in vacuum. The Tauc parameter (B ^1/2) and Urbach energy (E _U) have been determined from the transmittance spectra, to understand the changes in structural disorder; it is found that B ^1/2 increases whereas E _U decreases as the thickness of the films increases. Based on the results, it is suggested that bond re-arrangement, i.e. transformation from homopolar bonds to heteropolar bonds, takes place with increase in thickness. The thermal diffusivity values of GeS₂ thin films also show the presence of a chemically ordered network in the GeS₂ thin films. Further, it is found that these films exhibit memory-type electrical switching. The observed variation in the switching voltages has been understood on the basis of increase in chemical order.     

Potentiality of SBN textured ceramics for pyroelectric applications

Textured Sr_xBa_1−xNb₂O₆ (SBN) ferroelectric ceramics with x = 0.53 and 0.63 were fabricated by hot forging process. The objective was to obtain, in the ceramic form, the strong anisotropy of the electric properties that these materials possess in the single crystal form. Properties such as electric permittivity, pyroelectric coefficient and dielectric loss showed an anisotropy between the perpendicular and parallel direction with respect to the pressure axis (applied pressure during the forging of the ceramics). A high pyroelectric coefficient, comparable with these published for SBN single crystal with the same composition, was obtained for the SBN53/47 ceramic, when measured in the perpendicular direction to the pressing axis. From the calculus of the pyroelectric figures of merit, it was possible to conclude that the textured SBN53/47 ceramic has a high potential to be used as pyroelectric elements. This ceramic, cut in the perpendicular direction to the pressing axis, possess high potential as fast pulse detector but the same ceramic, cut in the parallel direction to the pressing axis, has better properties to be used as large area and point detectors.