磷,砷,锑和铋原子nd轨道在原子簇中的成键作用

对原子簇P_4,As_4,Sb_4,Sb_4~(2-)和Bi_4~(2-)中磷、砷、锑和铋原子的nd轨道参予成键作用进行了研究.通过对体系能量和在形成化学键的两原子间找到键子的几率的计算表明,磷、砷、锑和铋原子的nd轨道对这些原子簇中键的形成起着重要的作用.     

强磁场下的固体物理研究进展

强磁场下的物理研究是一个富有成果的研究领域，40T以下稳态强磁场的研制成功为固体物理研究提供了新的科学机遇。文章简要地介绍强磁场下某些固体物理，其中包括高温超导体的H－T相图和非费米液体行为，德哈斯（de Haas)效应和费米面性质，电子的Wigner结晶及其动力学行为，磁场诱导的相变（如绝缘体－金属和超导转变），多级磁有序，串级自旋密度波和大块材料中的量子霍尔效应等的实验研究的近期进展，希望以此引起人们对国内强磁场下物理研究的关注。     

Elastic scattering of low-energy electrons by NO

We report elastic integral, momentum transfer and differential cross sections for electron scattering by N₂O for energies up to 50 eV. These results were obtained at the static-exchange approximation with the Schwinger Multichannel Method with Pseudopotentials [M.H.F. Bettega, L.G. Ferreira and M.A.P. Lima, Phys. Rev. A 47, 1111 (1993)]. In general our results show good agreement with experimental data and with other theoretical results but some discrepancies are found. We have also found a shape resonance around 4 eV in agreement with previous calculations using the R-matrix Method of Sarpal et al. [J. Phys. B 29, 857 (1996)]. On the other hand, the existence of a resonance at about 13 eV, clearly seen by the Schwinger Variational Iterative Method [Michelin et al., J. Phys. B 29, 2115 (1996)], can not be confirmed by our calculations. At this energy, our cross sections show a broad bump with no clear resonant behavior given by the eigenphase sum. Received: 13 November 1997 / Revised: 13 March 1998 / Accepted: 9 April 1998     

高偏压Al-MgF_2-Au(Cu)隧道结的结构、导电和发光

本文对我们所发明的Al-MgF_2-Au(Cu)薄膜发光器件[1]的内层结构、导电过程和发光机理做了进一步的研究,对以前报导的一些结论作了原则性的修正:前所报导的Al-MgF_2-Au结内层的实际结构是Al-Al_2O_3-MgF_2-Au,而不仅仅是Al-MgF_2-Au;且正是由于Al_2O_3膜的存在,方才使MgF_2膜得以具有绝缘作用。是来之负电极的隧穿电子,而不是MgF_2膜内的热电子,导致了该结的导电和发光。据此,本文对该结在高偏压下的logL∝V的新型伏安特性曲线及其发射光谱中位于3.4ev(3600)附近的截止频率给出了理论解释;从而得出:电子隧穿,激发SPP,然后SPP退激发光的这一物理过程,即使在Al、Au两电极间的绝缘层厚度由3μm左右增加到20μm左右时,也可依然存在。     

Elastic scattering of electrons by helium atoms in high energy higher order Born approximation

The differential cross-sections forē-helium elastic scattering are calculated by using Yateshigh-energy higher order Born approximations, through 0 (K _i ^{Emphasis>−2} ) of the incident electron momentum, and comparisons have been made with the recent theoretical and experimental results.     

(e, 2e) triple differential cross section for ionization-excitation of helium

Simultaneous ionization and excitation of helium by electron impact is considered in an improved second Born approximation. The wave function of the low energy ejected electron is obtained in the field of residual He⁺ ion in 2s-state. The calculation has been done for the processe ⁻+He→e ⁻+He⁺(2s)+e ⁻ in the coplanar asymmetric geometry with Hartree-Fock wave function of Byron and Joachain for the helium ground state and the results are compared with the absolute experimental data of Dupreet al [J. Phys. B25, 259 (1992)] at ∼ 5.5 keV incident energy. Our results are found to increase the ratio of the recoil peak to binary peak intensity by about 30% over the first Born results and thus to bring it closer to the experimental data.     

Recent progress in quantitative and high spatial resolution AES

Progress in high resolution Auger electron spectroscopy (HR-AES or scanning Auger microscopy, SAM) during the past few years is characterized by the use of efficient field emission electron sources, parallel detection capabilities and improved data acquisition, storage and processing, thus enhancing spatial resolution (to about 10 nm), signal to noise figure and quantification of elements in different chemical bonding states, e.g. by routinely using factor analysis. Optimized ion sputtering facilities, particularly sample rotation, enable depth profiling with high, depth independent resolution. The basic features of SAM are discussed with respect to EPMA (electron probe micro-analysis), emphasizing fundamental limitations and future developments.     

铁磁薄膜中圆偏振光感应的瞬态磁光Kerr峰的物理起源

使用飞秒时间分辨抽运-探测磁光Kerr光谱技术,实验研究了圆偏振光抽运面内磁化FePt和垂直磁化GdFeCo薄膜的磁化演化动力学,发现在时间延迟零点处均出现瞬态Kerr峰.分析了此Kerr峰的起源,指出此瞬态Kerr峰与铁磁性无关,可能起源于自由电子的顺磁磁化,而顺磁磁化的外磁场来自圆偏振抽运光的逆Faraday效应.基于顺磁磁化模型的计算结果支持此观点.基于此观点,逆Faraday效应感应的磁场脉冲宽度应该与激光脉冲宽度一致.     

低能He~(2+)入射He原子转移电离实验中出射电子成像研究

利用反应显微谱仪对70keV He2+-He转移电离过程中的出射电子进行了成像,研究了出射电子的空间速度分布特征.结果表明:电子主要集中在散射平面内;在散射平面内,电子速度分布介于零与入射离子速度Vp之间(即前向出射)且在散射离子和靶核核间轴处有一极小值,呈现出典型的双峰结构.出射电子的上述分布特征可由出射电子波函数σ振幅和π振幅的干涉进行定性解释,σ振幅和π振幅对出射电子波函数的贡献与碰撞参数相关.在小碰撞参数下,π振幅的贡献更加明显;而在大碰撞参数下,σ振幅的贡献更加显著.     

用锁相放大技术采集电子自旋共振信号

利用示波器通过电子顺磁共振波谱仪观察了DPPH样品中未偶电子的自旋共振信号,使用锁相放大技术采集了电子自旋共振信号的微分线,讨论了影响实验结果的因素,给出了相关的实验参数。分析发现,所采集到的微分线为典型的Guass线型,这与所使用固体试样中电子的周边环境是一致的,这从实验的角度实现了锁相放大器对电子自旋共振信号的采集。