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对于一个N电子体系, 正确的交换Hamilton应该由两项组成,为Hex=-2A1ii·sj-2A2ii·sj,而不是以往的铁磁学理论使用的Hex=-2Aii ·sj (其中A为A1与A2的代数和, A1>0, A2<0), 以往的理论使用了一个不合理的交换Hamiltonian量.-2A1ii·sj与-2A2ii< /sub>·sj在数学上是同类项,但是在物理上不是 同类项,它们有不同的本征态和本征值.根据量子力学中的态叠加原理,这个电子系统的本 征态矢为X〉=1A21+A22(A1 1〉+A2‖2〉),其中Dirac符号1〉表示系统所有电子 的自旋平行排列时的态(简称平行自旋态)矢量,2〉表示系统所有电子或最近邻电子的自 旋反平行排列时的态(简称反平行自旋态)矢量,Hex的本征值(即系统的 交换能) 为E=-Nz(A1-A2)-2NzA22A1 +A2=-Nz(A2-A1)-2NzA21A< sub>1+A2,其中z为最近邻电子数.当A2=0时,X〉=1〉,E =-A1, 系统具有Wei ss 铁磁性;当A1 =0 时,X〉=2〉,E =-A2,系统具有Neel 反铁磁性;当A1 =A2(即A=0)时,X〉=12 (1〉+2〉),E=-A1,系统处于自旋玻璃(spin glass)态;当A1>A 2时,X〉=1A21+A22[(A1-A2)1〉+A2(1〉+2〉)],平行自旋态与自旋 玻璃态共存;当A12时,X〉=1A21+A22[(A2-A1)2〉+A1( 1〉+2〉)],反平行自旋态与自旋玻 璃态共存.与原来理论中的Weiss铁磁态或Neel反铁磁态相比,平行自旋态与自旋玻璃态共存 或反平行自旋态与自旋玻璃态共存使系统的交换能降低.自旋玻璃态中电子自旋之间取向的 随机性或无序性是由交换Hamiltonian中-2A1iisj 与-2A2ii·sj之间的竞争引起的,不是热运 动引起的.
关键词:
交换哈密顿量
铁磁态
反铁磁态
自旋玻璃态 相似文献
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研究了硼的2P01(基态),2P02,2Pe1和4Pe14个N=2共壳P态结构的定性特征,表明了电子关联对自旋极性的依赖,显示了各量子态对取向(相对于总角动量L)的偏爱,研究了它们的几何结构和内部运动模式,侧重探讨了量子力学对称性对微观系统的决定性效应。
关键词: 相似文献
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用虚拟自旋-1/2算符理论考察了I=1的核四极共振自旋系统在其能级间隔较小时对1-2个脉冲的响应.由于核四极相互作用表象中的射频场与核自旋的相互作用(Hrf)包含时间,因而用Dyson时序算符来计算密度算符在Hrf作用下的演化. 相似文献
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本文根据算符函数的幂级数展开,给出了描述高自旋弱耦合体系的积算符理论,并用来描述In S((1)/2)体系(其中I=1/2,1,…)的DEPT实验.给出I(1)n S((1)/2)体系(例如CDn)DEPT谱线的增益系数的普遍公式,并提出了用作图法得出谱线结构的方法. 相似文献
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N. P. Hessey E. C. Booth W. J. Fickinger K. P. Gall M. D. Hasinoff D. Horváth J. Lowe E. K. McIntyre D. F. Measday J. P. Miller A. J. Noble B. L. Roberts D. K. Robinson M. Sakitt M. Salomon D. A. Whitehouse 《Zeitschrift fur Physik C Particles and Fields》1989,42(2):175-183
We have measured the weak radiative decay branching ratio (∑ + →pγ)/(∑ + →pπ0). The experiment was carried out at Brookhaven National Laboratory using a low-energy separatedK ? beam stopping in liquid hydrogen. The∑ + was tagged by observing the pion fromK ? K + p→∑ +π? in a range telescope, and the gamma was detected in a segmented NaI detector. The result is (2.81±0.39 ?0.43 +0.21 )×10?3, which is consistent with previous measurements. This corresponds to a branching ratio for (∑ + →pγ)/(∑ + → all) of (1.45±0.20 ?0.22 +0.11 )×10?3, where the quoted errors are statistical and systematic, respectively. A total of 408 signal events were observed, doubling the previous world total. 相似文献
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V. Karimäki R. Kinnunen M. Korkea-aho J. Maalampi J. Tuominiemi G. W. van Apeldoorn D. Harting D. J. Holthuizen B. J. Pijlgroms P. Johnson P. Mason H. Muirhead G. D. Patel 《Zeitschrift fur Physik C Particles and Fields》1981,10(3):189-195
Inclusive production of∑ ±(1385) resonances is studied in \(\bar pp\) interactions at 12 GeV/c. The cross sections for∑ +(1385)+cc and∑ ? are determined to be 251±38 μb and 123±30 μb, respectively. The inclusive spectra are presented as a function of Feynman x, c.m. rapidity and the squared transverse momentump T 2 . Significant differences with the correspondingpp data are found in the longitudinal momentum distributions. The qualitative features of the production can be explained by simple quark ideas. 相似文献
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基于计算双原子分子完全振动能谱及离解能的代数方法 (algebraic method,AM)和研究双原子分子解析势能函数的能量自洽法(energy consistent method,ECM),建立了计算双核分子体系精确解析势能函数的代数-能量自洽法(AM-ECM).应用AM-ECM方法研究了7Li+2-23Σg,KH-X1Σ+,NaLi-X1Σ+和NaLi-A1Σ+电子态的解析势能表达形式,并与其他方法的研究结果进行了比较,获得了能正确描述这些电子态在渐近区和离解区的精确解析表达结果. 相似文献
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P. C. Sood 《Zeitschrift für Physik A Hadrons and Nuclei》1983,310(1-2):95-97
The band-head energies of the two-quasiparticle states expected in the doubly odd deformed nucleus170Ho are calculated for a zero range residual interaction. The results are compared with the available experimental information. It is concluded that the ground state has the Nilsson configuration 6+{7/2?[523↑] p }+5/2[512↑] n being the 2.76m isomer whereas the 43s isomer is the 1+ ∑=0 state arising from the same configuration and lies at about 100 keV excitation energy in agreement with the experiment. The first excited state in this nucleus is predicted to be the 4?{3/2+[411↑] p +5/2?[521↑] n } state close to the ground state with the corresponding 1? ∑=0 member expected to appear well above the 1+ isomer. 相似文献
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利用基于全相对论框架下的多组态Dirac-Fock理论方法发展起来的程序包GRASP92和新发展的处理辐射跃迁过程的程序REOS99,计算了类镍等电子系列离子(Z=45—95)的基组态3s23p63d101S0以及低激发组态3s23p63d94l,3s23p53d104l和3s3p63d104l(l=s,p,d,f)的能级及其向基态的M1,M2,E2禁戒跃迁概率.通过分析高离化类镍离子在特定的原子序数范围内由于存在能级交叉而产生的强组态相互作用,解释了高离化类镍离子禁戒跃迁概率的反常变化现象,探讨了禁戒跃迁概率受强组态相互作用影响而变化的一般规律. 相似文献
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本工作结合多光子离化谱,激光诱导荧光及荧光激发谱技术,仔细研究Cl2分子高激发Rydberg态和混合Rydbery-价态的结构及性质,定域了11∑u+态内区的位置,证明21∑u+态强的Rydberg-价混合特征,发现一新的u对称性Rydberg态并建议标识为1∑u态的激发,对三光子激发过程,21关键词: 相似文献
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The two∑ ? reactions at rest∑ ? p→Λ 0 n and∑ ? p→Λ 0 n have been studied in order to determine the capture ratio $$r_c = \frac{{\sum ^ - p \to \sum ^0 n}}{{(\sum ^ - p \to \sum ^0 n) + (\sum ^ - p \to \Lambda ^0 n)}}$$ , theΛ 0-lifetime and the∑ ?-Λ 0 mass difference. The following results were obtained: $$\begin{gathered} rc = 0.474 \pm 0.016 \hfill \\ \tau _{\Lambda ^0 } = (2.47 \pm 0.08) \times 10^{ - 10} \sec \hfill \\ M_{\sum ^ - } - M_{\sum ^0 } = 81.64 \pm 0.09{{MeV} \mathord{\left/ {\vphantom {{MeV} {c^2 }}} \right. \kern-\nulldelimiterspace} {c^2 }} \hfill \\ \end{gathered} $$ The∑ ?-mass was determined from the range of the stopping∑ ?-hyperons,M ∑} =1197.19±0.32 MeV/c 2. 相似文献
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W. F. Mahmoudi N. Ben Nessib S. Sahal-Bréchot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):7-10
Owing to the increasing sensitivity of detectors,
accurate line profiles are needed for accurate stellar
atmospheres modelling and for laboratory and technological plasmas
as well. So, Stark broadening parameters of isolated lines of
complex atoms and ions within the impact and quasistatic
approximation are needed, even if the atomic abundance of the considered element is low.
Angular factors of the diagonal line strength entering the
quadrupole term appearing in the semi-classical expression of the
width of line broadened by electron or ion perturbers, are needed.
The aim of this paper is to extend the previous calculations of
this diagonal multiplet factor which were obtained for
configurations of the type ln and l1
nl2
m to
more complex configurations in LS coupling.
To study the Stark broadening of isolated lines in the impact and
quasistatic approximation, we use the semi-classical-perturbation
treatment, including both dipole and quadrupole contribution in
the expansion of the electrostatic interaction between the optical
electron and the perturber. We also use the Fano-Racah algebra.
Angular factors of the diagonal line strength entering the
quadrupole term appearing in the semi-classical expression of the
width of line broadened by electron or ion perturbers, are
calculated. New diagonal multiplet factor formulae for more
complicated configurations such as
(n1l1
n(LnSn)n2l2
m(LmSm)n3l3
p(LpSp))
are provided.
These formulae can enter the computer Stark semi-classical
perturbation codes. 相似文献