电子与钠原子散射的S, T, U参数研究

电子原子散射中的S，T，U参数可用来描述散射前后自旋状态的变化，研究精细结构水平上的散射激发振幅之间的关系，进而揭示电子原子碰撞过程中电子自旋-轨道耦合以及电子-电子交换等自旋相关效应.采用扭曲波玻恩近似计算了钠原子受电子散射S→P跃迁中的S，T，U参数，分析了多种入射能(2.2—60 eV)的电子与钠原子激发S→P跃迁过程的S,T,U参数随散射角的分布，其中对10 eV入射能的S_p参数与已报道实验数据符合一致.结果表明，较低能电子入射下的S,T,U参数随散射角的分布幅度和起伏都比较明显，入射能大于40 eV的电子入射，S,T,U参数的散射角分布变化很小. 关键词： 散射激发 S')" href="#">S T')" href="#">T U参数')" href="#">U参数 散射振幅 自旋相关效应     

电子与钠原子散射极化参数的计算

采用扭曲波方法对电子与钠原子非弹性散射截面，及与散射过程有关的极化参数进行了计算，将所得结果与实验值和CCC方法所得结果进行了比较.可以看出在中高能(5—10倍阈能)领域，扭曲波法是一种模型清晰、结果可靠的方法. 关键词：     

电子被氩,氪,氙原子散射总截面的光学模型研究

文中基于光学模型势方法，详细分析并改进了一种准自由模型吸收势，把它作为光学模型的虚部，在能量０．１－３００ｅＶ的范围内计算了电子被Ａｒ，Ｋｒ，Ｘｅ原子散射的总截面，计算结果与实验值进行了比较。     

基于递归T矩阵的离散随机散射体散射特性研究

本文根据电磁场矢量球波函数多极点展开原理及矢量叠加定理提出了递归T矩阵算法的矢量形式,并且基于矢量递归T矩阵算法建立了多散射球模拟离散随机散射体散射的三维电磁散射模型.通过计算不同尺寸、随机分布散射球的散射以及分析散射球间的高阶散射效应,结果表明:矢量递归T矩阵算法具有很高的计算精度,算法中包含多散射体间的高阶散射效应,因此能够精确计算多散射体总的散射效应.本文所建模型可应用于土壤湿度探测工程中评估地表下掩埋离散随机散射体散射对雷达回波信号产生的影响.     

自旋极化电子原子散射的(e,eγ)符合实验研究

本文介绍了自旋极化电子原子散射的(e,eγ)符合实验的理论基础、实验装置和参数测量方法,描述了符合实验研究主要结果,说明了符合实验研究的物理意义。     

自旋极化电子原子散射的(e,eγ)符合实验研究

本文介绍了自旋极化电子原子散射的(e,eγ)符合实验的理论基础、实验装置和参数测量方法,描述了符合实验研究主要结果,说明了符合实验研究的物理意义。     

铁基超导体Fe1+yTe1-xSex中磁性的中子散射研究

本文对本研究组主要的研究领域——利用中子散射研究铁基超导体系Fe_1+yTe_1-xSe_x中磁性与超导的相互作用进行简要综述. Fe_1+yTe_1-xSe_x具有和其他铁基、铜基超导体相似的相图——母相Fe_1+yTe是反铁磁体, 随着Se掺杂的增加, 母相的反铁磁序受到抑制, 随后在x～30%处体超导出现, 在x～50%处达到最佳掺杂, 此时超导转变温度T_c～ 15 K, 达到整个体系在常压下的T_c最大值. 它们的相图又存在着差别: 在相图末端, 即当Se掺杂达100%时, Fe_1+ySe 仍然超导, T_c～8 K. 该体系母相磁有序的面内波矢大致为(0.5,0) (采用每个原胞含2个铁原子的四方结构), 随着Se含量的增加, 在超导逐渐发展的同时, 磁激发谱的谱重被逐渐转移到波矢为(0.5,0.5) 处. (0.5,0.5) 处在温度低于T_c 时出现中子-自旋共振峰. 施加外磁场后, 超导受到抑制, 该共振峰也被压制. 从这些实验结果我们得到以下的结论: 在这个体系中磁性和超导紧密耦合在一起——(0.5,0) 处的静态磁有序与超导互相竞争, (0.5,0.5) 附近的自旋激发则可能对超导电性的形成具有重要的促进作用. 本文还将简要讨论磁性的来源和3d 过渡金属的替代效应.     

纵向运动双散射散斑场的动态特性研究

研究了慢纵向运动双散射散斑场的统计性质,得出纵向运动双散射散斑振幅自相关函数、强度涨落自相关函数,并由此得出,夫朗和费衍射区内的接收平在上任意点上的自相关函数是时间的非平稳随机过程,而在光轴附近小区域内,强度涨落自相关函数是时间的平稳随机过程,相关时间与散射体纵向运动速度或反比,理论和实验结果相一致。     

电子散射的钠原子受激态取向参数研究

原子碰撞中的取向(orientation)参数的研究为原子碰撞动力学、原子受激态结构提供了丰富的信息.散射靶原子集合可用态多极(state multipole)描述，用它可以表征受激态原子的取向参数.通过取向参数与受激原子态退激的偶极辐射光子的Stokes参数之间的关系，可以进行实验与理论的比较.本文主要研究钠原子受电子散射S→P跃迁中取向参数，根据散射理论的扭曲波近似展开计算得到的散射振幅，带入态多极，然后计算钠原子3P态取向与散射角的关系及不同入射能下受激态取向参数变化特点，并与电子-光子符合散射实验所测数据进行比较.考虑到符合散射实验的测量困难，在误差范围内，理论分析与实验结果符合得比较好. 关键词： 取向参数 态多极 Stokes参数 电子-光子符合测量     

钠5S态与基态钾原子的碰撞能量转移

在Ｎａ－Ｋ混合蒸汽中，利用染料激光器，将基态Ｎａ原子双光子激发到５Ｓ态。用荧光法测量了过程Ｎａ（５Ｓ）＋Ｋ（４Ｓ）→Ｎａ（３Ｓ）＋Ｋ（８Ｄ，１０Ｓ）的碰撞转移截面，Ｋ８Ｄ，１０Ｓ对Ｎａ５Ｓ的荧光比中，含有Ｋ８Ｄ１０Ｓ碰撞转移的影响。第２个实验可以消除这个影响，双光子激发Ｋ原子到８Ｄ（或１０Ｓ）探测８Ｄ（１０Ｓ）对１０Ｓ（８Ｄ）的荧光比，Ｎａ（５Ｓ）→Ｋ（８Ｄ，１０Ｓ）碰撞转移截面（１０－１５ｃｍ２）分别是１０．５±４．２和９．５±３．８     

Quasiclassical parameter calculation of elastic electron scattering by a xenon atom

A calculation (accurate up to terms in ²) is performed of quasiclassical phase shifts and of differential and total cross sections of elastic electron scattering by a xenon atom in the static field approximation, with and without exchange.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 69–73, October, 1972.The author is grateful to N. I. Zhirinov, under whose guidance this work was performed.     

Statistical model of an atom in electron scattering calculations

The parameters describing scattering of electrons by atoms, which usually involve multiple integration of the atomic potentials, may be severely affected by the accuracy of these potentials. In the present work an iterative procedure is proposed providing a sequence of solutions of the Thomas-Fermi equation with increasing accuracy. Such a sequence makes it possible to establish the sensitivity of a given parameter to the accuracy of the atomic potential, and consequently to determine the accurate value of this parameter. Based on the present solutions, the differential scattering cross-sections for the Thomas-Fermi atom are calculated, and are found to deviate from the literature data.     

The spectroscopy of surface vibrations by atom scattering

The recent progress in the production of highly monochromatic atomic beams is opening new perspectives in surface physics, having paved the way for a full determination of the surface vibrational structure. After a discussion on the possible determination of Rayleigh wave dispersion curves from angular distributions exploiting the kinematical focussing effect, a short review is presented on the direct measurement of surface phonon dispersion curves, first achieved by Brusdeylins, Doak and Toennies in alkali halides, from time-of-flight (TOF) spectra of scattered He atoms. A comparison is made with the existing theories of surface phonons in ionic crystals. The state of the art in the theory of inelastic processes is briefly illustrated in order to discuss the theoretical interpretation of TOF spectra. The one-phonon energy loss spectra of He scattering from LiF(001) calculated for a hard corrugated surface model are found to be in general good agreement with the experimental TOF spectra. From such a comparison evidence is obtained that: i) one-phonon processes are predominant, and ii) in addition to Rayleigh waves important contributions to the inelastic scattering come from the surface-projected density of bulk phonons. Important effects due to inelastic resonances with surface bound states are put in evidence and explained by simple kinematical arguments. The possible observation of surface optical modes in NaF(001) is finally discussed.     

Determination of nuclear parameters by inelastic electron scattering at low-momentum transfer

The second-order Born-approximation treatment of Cutler and Schucan was applied to inelastic electron scattering data on ⁶Li, ⁶⁰Ni, and ¹¹⁴Cd acquired at low momentum transfers. The form factors as a function of momentum transfer q in the range of 0.25–0.57 fm^?1 were obtained by angular distribution measurements performed at incident energies of 30 to 60 MeV. The correlation between two parameters deduced from the measurements, the reduced transition probability B(E2↑) and the transition radius R⁽²⁾_tr, is discussed. It is suggested that inelastic electron scattering data at low-q is best used either in conjunction with an accurate value of B(EL↑) (available from the model-independent analysis of “photon” experiments at zero momentum transfer) to allow accurate determination of R⁽²⁾_tr, or in conjunction with high-q inelastic electron scattering data to allow accurate determination of B(EL↑) as well as R⁽²⁾_tr.     

电子枪功率与束宽对金属原子蒸气特性的影响

在原子法激光同位素分离工程中,电子枪加热金属铀产生的原子蒸气的密度、速度以及温度等宏观量分布特性是非常重要的参数.为了分析电子枪功率和束宽对原子蒸气密度、速度、温度、质量通量和速度分布等物理特性的影响,采用直接MonteCarlo方法用柱坐标模拟了铀原子平面蒸发动力学过程.在电子枪加热方式下,蒸发源温度场不均匀,而且温度场随电子枪功率和束宽变化.着重研究这种变化对蒸气各种物理特性的影响.模拟结果表明,电子枪功率越高,蒸气径向宏观漂移速度越大,蒸发量越大;电子束束宽越窄,蒸发量越大. 关键词： 金属蒸发 原子法激光同位素分离 直接MonteCarlo 电子枪     

The influence of exchange effects in elastic electron scattering from sodium clusters

Elastic scattering of electrons from sodium clusters (Na₈, Na₂₀) is investigated for impact energies below the inelastic threshold of about 1 eV. We show that the observed resonance structure of the elastic cross section strongly depends on the inclusion of exchange effects between the cluster and the projectile electrons.     

Coincidence investigation of inelastic electron–atom collisions with magnetic selection of scattering angle – feasibility study

New apparatus for electron–atom collision investigations incorporating the magnetic angle changing method into the coincidence technique has been set-up. Combination of the two enables measurements of Electron Impact Coherence Parameters in the full range of scattering angles. First energy loss and coincidence spectra are presented.