一种研究自旋翻转散射效应的新方法

金属中自旋翻转散射长度远长于电子平均自由程，近来关于自旋翻转散射效应的研究主要集中于扩散区域．文章作者提出了一种使用双势垒磁性隧道结来研究纳米尺度结构中弹道区域的自旋翻转散射效应的新方法．这种方法可以从磁电输运性质的测量，得出中间隔离层中的自旋翻转散射效应的温度和偏压关系，进一步可以得出诸如电子平均自由程和自旋翻转散射长度等自旋散射信息，以及中间层的态密度和量子阱信息．     

有机铁磁体中链间次近邻电子跳跃积分诱导的电荷密度波

在链间耦合中同时计入相邻链相同格点间电子跳跃积分和相邻链次近邻格点间电子跳跃积分,研究了链间耦合对电荷密度和自旋密度分布的影响．结果表明,链间耦合可以导致主链上出现电荷密度波,不同格点间的链间耦合诱导自旋密度在侧基和主链间发生不同的转移． 关键词：     

电荷转移型Hubbard模型的相图

用玻色化技术和高斯波泛函变分理论研究了电荷转移型Hubbard模型.通过自旋密度波和电荷密度波的位相结构的变化，并结合其相应能隙的变化，得到以下结论：系统的Ising相变与Mott相变不重合，中间有一个SDI(spontaneouslydimerizedinsulating)的过渡相.在BI(band-insulator)相，自旋密度波与电荷密度波都具有能隙，而在MI(Mott-insulator)相，电荷密度波具有能隙，自旋密度波没有能隙. 关键词： Hubbard模型 电荷密度波 自旋密度波 相图     

有缺陷铁磁体的中子非弹性散射

本文对有缺陷铁磁体的中子-自旋波散射作了理论研究。计算了在简单情况下的非弹性散射的微分截面。通过慢中子的散射实验可能证实自旋波局域模的存在。我们在文中得出了散射态波函数,并证明了它们与局域模波函数一起在自旋偏离为一的子空间中组成了正交归一完整的波函数系。 关键词：     

小粒子体系的自发磁化

从自旋波理论出发,通过直接求解Heisenberg模型,研究了低温下小粒子自旋体系的自发磁化规律。研究表明:极低温下自旋波被冻结;在任何温度范围内,Bloch T^3/2定律都不再严格成立。同时,本文还给出了小粒子中自旋受激反转几率随位置的分布,指出低温下不存在运动明显剧烈的表面层。 关键词：     

自旋-轨道耦合玻色-爱因斯坦凝聚势垒散射特性的研究

对自旋-轨道耦合玻色-爱因斯坦凝聚中的双势垒散射问题进行了研究, 得到了系统透射系数的解析表达式, 并对如何克服Klein隧穿以及如何束缚Dirac粒子进行了讨论并给出囚禁Dirac粒子的实验方案. 此外, 运用时间劈裂谱方法对Dirac粒子势垒散射问题进行了数值模拟. 分析了Dirac粒子分别在势垒Klein阻塞区域中心以及边缘的透射情况. 最后从排斥和吸引相互作用两方面研究了非线性相互作用对于Dirac粒子演化的影响, 结果表明弱非线性相互作用对散射特性的影响非常小, 而强非线性相互作用会彻底破坏波包的动量分布, 从而改变Dirac粒子的势垒散射效果． 关键词： 自旋-轨道耦合 Klein隧穿 势垒散射 玻色-爱因斯坦凝聚     

钇铁石榴石自旋波导管中磁钉扎对自旋波模的影响（英文）

利用微磁模拟,研究钇铁石榴石自旋波导管边界的磁钉扎对其中自旋波动力学的影响。模拟结果表明：磁钉扎引起的双磁子散射将自旋波散射到多个方向,使得自旋波在k空间的分布更加分散。自旋波模的演化表明：不同自旋波模的共振场不同,而双磁子散射使得自旋波模的共振场更为接近。另外,双磁子散射通过改变自旋波模的弛豫速率,改变了自旋波模的共振强度,幅度可达40%。增大自旋波导能够降低磁钉扎的影响,可以用来提升自旋波导的性能。     

铁磁超导态/绝缘层/自旋三重态p波超导体结的直流Josephson电流

由Bogoliubov-de Gennes方程得到铁磁超导共存态(FS)的自洽方程，利用推广的Furusaki-Tsukada的电流公式计算了铁磁超导态/绝缘层/自旋三重态p波超导体(FS/I/p)结的直流Josephson电流随结的温度、相位差以及FS中磁交换能、结界面的势垒散射强度的变化关系.研究表明：FS中磁交换能、结界面的势垒散射均抑制FS/I/p结的直流Josephson电流.当自旋三重态超导体具有p_x波配对势时，自旋三重态超导体结的直流Josephson电流随结两侧相位差的振荡周期是π. 关键词： 铁磁超导态 自旋三重态超导体 p波超导体 直流Josephson电流     

考虑自旋的散射问题分波解

研究粒子体系的散射问题,考虑靶核的自旋,给出其弹性散射问题的振幅的分波表达式,并对结果进行讨论。     

具有铁磁绝缘层超导体结的直流Josephson电流

在s波超导体/铁磁绝缘层/s波超导体Josephson结（S/FI/S）中，考虑结界面铁磁绝缘层的磁散射和粗糙散射情况下，运用Bogoliubov-de(BdG)方程和Furusaki-Tsukada(FT)的电流公式计算准粒子的输运系数及S/FI/S结的直流Josephson电流与温度T，结两侧的相位差之间的关系，研究表明：结界面的磁散射和粗糙散射均抑制结中准粒子的Andreev反射，降低了流过S/FI/S结的直流Josephson电流。     

相对论粒子的散射与低速粒子的散射

研究了相对论粒子间散射的规律,推导了相对论粒子间散射的洛伦兹因子公式.结果发现:如果两个粒子的静止质量相同,则粒子在高速时的碰撞规律和低速时的碰撞规律相同,即两个正碰粒子互换速度;如果两个粒子的静止质量不同,则粒子在高速时的碰撞规律和低速时的碰撞规律不同,高速正碰时重粒子将损失大部分能量,轻粒子的速度将接近光速,而不等于重粒子速度的2倍.     

Subthreshold resonances in three-particle molecular systems

This paper examines the resonant scattering of a light particle by a pair of identical particles in the Efimov limit. An analytic expression for the resonance widths is derived. The results of calculations are compared with the solution of Faddeev integral equations within a broad range of masses of the light particle. It is shown that the widths of the subthreshold resonances in the scattering amplitude obtained from the integral equations with Yamaguchi potentials are accurately described by the analytic expression, which makes it possible to use this expression in a range of masses inaccessible to numerical calculations. The conclusion is drawn that the lifetime of highly excited negative molecular ions is infinite. Zh. éksp. Teor. Fiz. 115, 1973–1986 (June 1999)     

On existence of nanoparticles below the sooting threshold

Nanometer-sized particles were studied by photoionisation mass spectrometry and scanning mobility particle sizer in laminar premixed ethylene flames above and below the critical sooting threshold. For sooting flames, both techniques detected a large number of particles with masses between 1 and 50 ku or diameter around a few nanometers. Neither method detected an appreciable number of particles below the sooting threshold in flames similar to those studied earlier for UV absorption and scattering of transparent soot. The absence of particle signals in both experimental techniques raises the question about the origin of UV absorption under nonsooting conditions.     

Electrodynamics of a Scalar Particle in a Plane Electromagnetic Wave Field

In the present paper, compact expressions are derived for the probability of photon emission by a scalar particle and for the probability of creating pairs of scalar particles in an arbitrary plane electromagnetic wave field. Based on these general expressions, the amplitude of elastic scattering of a scalar particle and the amplitude of elastic scattering of a photon are derived by the method of dispersion relations (in the first-order approximation for the fine-structure constant ₀ = e ²/4). The real components of these amplitudes determine the radiative corrections for particle masses in the examined fields. Some particular cases of the plane wave field are examined. In particular, the above-indicated amplitudes in the external electromagnetic field being a superposition of a constant crossed field and a plane elliptically polarized electromagnetic wave propagating along the direction orthogonal to the magnetic and electric components of the constant crossed field are investigated. The amplitude of elastic scattering of a scalar particle in an arbitrary plane electromagnetic wave field is also obtained by direct calculations of the corresponding mass operator of the scalar particle in this field.     

Chaos in the relativistic Euler problem

The Euler problem with two fixed point masses and one moving mass is reconsidered in the light of general relativity. The scattering of a particle by two fixed black holes is shown to be strongly chaotic. Two neutral black holes have been used for the study. The particle trajectories have been computed numerically using a modified muffin tin approximation. A plot of the scattering angle against impact parameter showing distinct signs of chaos is presented. (c) 1996 American Institute of Physics.     

Chaos in the one-dimensional gravitational three-body problem

We have investigated the appearance of chaos in the one-dimensional Newtonian gravitational three-body system (three masses on a line with -1/r pairwise potential). In the center of mass coordinates this system has two degrees of freedom and can be conveniently studied using Poincare sections. We have concentrated in particular on how the behavior changes when the relative masses of the three bodies change. We consider only the physically more interesting case of negative total energy. For two mass choices we have calculated 18 000 full orbits (with initial states on a 100x180 lattice on the Poincare section) and obtained dwell time distributions. For 105 mass choices we have calculated Poincare maps for 10x18 starting points. Our results show that the Poincare section (and hence the phase space) divides into three well defined regions with orbits of different characteristics: (1) There is a region of fast scattering, with a minimum of pairwise collisions. This region consists of 'scallops' bordering the E=0 line, within a scallop the orbits vary smoothly. The number of the scallops increases as the mass of the central particle decreases. (2) In the chaotic scattering region the interaction times are longer, and both the interaction time and the final state depend sensitively on the starting point on the Poincare section. For both (1) and (2) the initial and final states consist of a binary + single particle. (3) The third region consists of quasiperiodic orbits where the three masses are bound together forever. At the center of the quasiperiodic region there is a periodic orbit discovered (numerically) by Schubart in 1956. The stability of the Schubart orbit turns out to correlate strongly with the global behavior.     

Class of model problems in three-body quantum mechanics that admit exact solutions

An approach to solving scattering problems in three-body systems for cases where the mass of one of the particles is extremely small in relation to the masses of the other two particles and where the pair potentials of interaction between the particles involved are separable is developed. Exact analytic solutions to such model problems are found for the scattering of a light particle on two fixed centers and on two interacting heavy particles. It is shown that new resonances and a dynamical resonance enhancement may appear in a three-body system.     

Concentrated suspension theory of sound attenuation in marine sediments—linear dependence of absorption coefficient on frequency

Statistical averages of acoustic scattering and attenuation in sea bed sediments, and of the corresponding sea bed absorption coefficients, are obtained. The multiple scattering interactions among the particles in concentrated suspension are taken into account. The suspensions are assumed to be a collection of spherical particles of various sizes, and for which the masses corresponding to various radii follow a normal distribution. The numerical results obtained show that the absorption coefficient has a linear dependence on frequency if there is a sufficiently broad distribution of the particle radii. However, if βR ? 1, where R is particle radius and β is the viscous wavenumber, the absorption may be proportional to the frequency raised to a power higher than unity. Comparisons of results with some published experimental data are presented.     

微粒特征分布函数测量理论和方法的进一步研究

运用微粒散射形体微扰理论对任意形体微粒的研究结果,根据光敏区光强的Gauss分布特征和微粒穿越位置的随机性,建立了相关模型和数学方程并求得了任意位置的微粒形体影响因子分布函数的数值解,讨论了大变化区的非线性影响.其次,根据微粒数分布离散性的特征,建立了微粒粒度分布函数的反演矩阵及其实验方法.最后进行了实验验证.     

MASSES OF THE LIGHT HADRONS AND SELF-ENERGIES IN THE BAG MODEL

The masses of the light hadrons are calculated in terms. of the cloudy bag model with use of pion-energies due to both gluon and pion exchange. By use of a type of pion-guark interaction which incorporates the finite extent of the pion the convergent self-energy due to pion exchange is obtained. The difficulties in the bag models which only include one type of the self-energies can be removed by. taking account of both and the baryon spectrum is reproduced well. It is found that these self-energies are large but have opposite effect on the masses of the hadrons.