The electron structure and x-ray emission spectra of noble metal aluminides

A calculation of the electron structure of [Al₈Cu₄] and [Al₈Au₆]- clusters was performed by the XαSW SCF-method. The X-ray emission and photoelectron spectra for noble metal aluminides Al₂Cu and Al₂Au are interpreted on the base of these calculations. The question of the possible influence of d-states on the distribution of Al3s-states and the shape of the AlL_2,3-emission spectrum is discussed for Al₂Cu.     

Temperature dependent peaks in secondary electron emission spectra

Peaks in the secondary emission spectra not associated with Auger effects have been observed in various metals (particularly copper and cobalt). These peaks are suppressed at elevated temperature and appear to have amplitudes which are unique functions of temperature. They are characteristic of well ordered, and, particularly, clean surfaces, and are interpreted in terms of the diffraction of the emitted secondary electrons.     

X-ray emission spectra and electron structure of neutron irradiated V3Si

The results of the X-ray VKβ₅ emission spectra of V₃Si irradiated with fast neutrons are reported. A comparison with the spectrum for unirradiated V₃Si as well as with cluster calculations suggested that the changes observed in the electron structure of irradiated V₃Si result from antisite defects and inhomogeneous atomic distribution.     

Time-dependent induced potentials in convoy electron emission

We study the time-dependent induced potentials at the convoy electron position due to the self-interaction with a metal surface and to the shock wave created by the positive hole (vacancy) left. The time evolution of these potentials are calculated using the linear response theory. Results obtained are fitted with simple functions. We find that those two potentials nearly cancel each other in the first ten atomic units of time.     

Visualization of field induced ferroelectric electron emission from TGS using emission electron microscopy

Field induced electron emission from triglycinesulfate (TGS) has been investigated using parallel imaging electron emission microscopy (EEM). The emission phenomenon has been induced by applying an ac electrical field up to 2 kV/mm to a single crystal of approximately 0.1 mm thickness. Emission patterns have been observed as a function of the applied field amplitude and of the crystal temperature. At voltages below the coercive field, no emission is visible. When approaching the Curie temperature, emission gradually disappears. This indicates an electron emission mechanism relying on the existence of a switchable ferroelectric phase. The information content of the images is discussed, an interpretation is given on the basis of existing theories. PACS 68.37.-d; 77; 77.80.Fm; 77.80.-e     

空气中激光烧蚀Cu产生等离子体发射光谱的研究

利用Q-开关Nd:YAG激光器产生的1.06 μm、10 ns的脉冲激光聚焦在空气中的Cu靶上,观测了激光诱导的Cu等离子体发射光谱.采用不同的激光能量,分析了波长范围为440 nm到540 nm的空间分辨发射光谱.在局部热力学平衡(LTE)条件近似下,根据谱线的相对强度,得到了等离子体电子温度约在104 K以上,给出了靶面附近电子温度的空间演化规律,并探讨了N(Ⅱ)500.52 nm谱线的谱线强度和半高全宽随激光能量的变化规律.     

Auger electron emission spectra from foil and gas excited carbon beams

Auger electron emission spectra from 2 MeV C⁺ ion excited by collisions with thin carbon foils and Ne gas are presented. The similarity of qualitative features for the C⁺ → C (foil) and C⁺ → Ne spectra indicates the similarity of ionization mechanisms for beam foil and beam gas excitation. The spectra were normalized to the lowest lying Li-like quartet state (1s 2s 2p)⁴P⁰ in carbon by comparison with time delayed foil excited electron decay-in-flight spectra. Comparison to Hartree-Fock calculated transition energies indicates that transitions in three and four electron carbon ions dominate the prompt spectra.     

Ion induced secondary electron emission from single crystal surfaces

Yields of ion impact induced electrons from very pure Ni(110) and Ni(111) surfaces have been measured. In several tilt planes the angle of incidence of a 5 keV H⁺, H⁺₂ or H⁺₃ ion beam is varied from perpendicular to grazing incidence. Below = 75° the yield increases as sec but shows characteristic depressions when the beam is incident along crystallographically low indexed lattice directions. This is explained by kinetic electron emission with respect to the projectile transparency of the crystal lattice.     

Optical spectra and electron structure of cubic boron nitride

On the basis of the known reflection spectrum, we calculate a complete set of fundamental optical functions for cubic boron nitride (c-BN) in the region of 2–23 eV. The integral spectrum of dielectric permeability is decomposed into 16 elementary components. Three main parameters (maximum energy, half-width, and oscillator force) for each of the components are determined. Using the well-known theoretical calculations for bands of boron nitride as the base we suggest a scheme of the nature of these dielectric permeability components. To whom correspondence should be addressed. Udmurtiya State University, 1, Universitetskaya Str., Izhevsk, 426034, Russia:e-mail: sobolev@matsim.udmurtia.su. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 579–583, July–August, 1999.     

“Fluorescent electron emission” — A prediction for resonant photoemission spectra

We have studied the effects of electronic relaxation in resonant photoemission spectra using a model of discrete plasmon-type relaxation with finite plasmon lifetime. In addition to the usual satellite peak with fixed binding energy, we predict the existence of a “fluorescent electron emission” peak at fixed electron kinetic energy.     

High-resolution normal emission UV-photoelectron spectra and band structure of Cu

The energy distribution curves of photoelectrons emitted along the normal direction from Cu (111), (001) and (110) surfaces using unpolarized HeI (hv=21.2 eV) and HeII (hv=40.8 eV, 48.4 eV) radiation incident at 45° to the surface were measured. For the interpretation the band structure as calculated by Janak et al. and by the combined interpolation scheme was used. The high resolution spectra along the [111] and [001] directions show dominant features from direct transitions, indicating strong residualk _z conservation, and density of states features, too. The band gap emission along the [110] direction using HeI radiation can be explained with direct transitions into evanescent states with nearly free electron bands. From the width of the peaks electron escape depths were calculated.     

基于微陷阱结构的金属二次电子发射系数抑制研究

近年来,金属二次电子发射系数的抑制研究在加速器、大功率微波器件等领域得到了广泛关注.为评估表面形貌对抑制效果的影响,利用唯象概率模型计算方法对三角形沟槽、矩形沟槽、方孔及圆孔4种不同形状微陷阱结构的二次电子发射系数进行了研究,分析了微陷阱结构的形状、尺寸对二次电子发射系数抑制特性的影响规律.理论研究结果表明:陷阱结构的深宽比、孔隙率越大,则其二次电子发射系数抑制特性越明显;方孔形和圆孔形微陷阱结构的二次电子发射系数抑制效果优于三角形沟槽和矩形沟槽;具有大孔隙率的微陷阱结构表面的二次电子发射系数对入射角度的依赖显著弱于平滑表面.制备了具有不同表面形貌的金属样片并进行二次电子发射系数测试,所得实验规律与理论模拟规律符合较好.     

Physical aspects of the shape of electron emission spectra for ferroelectric electrets

A correlation between the specific features of the electron emission spectrum of a ferroelectric electret and the behavior of the potential at the surface of the sample is determined within the theoretical approach proposed. The physical nature of the main features in experimental emission spectra is interpreted in terms of the behavior of the potential relief. It is revealed that the electret charge relaxation affects the spectrum shape due to the bifurcation (branching) of singularities in the spectrum.     

Surface structure from angular dependence of auger electron emission

Auger electrons emitted from atoms in the vicinity of a solid surface can show strong angular dependence in their emission due to elastic scattering from the surrounding ion cores of the solid. Model calculations for the emission of Auger electrons from sulphur adsorbed on a Ni (100) surface show that these angular features are very sensitive to the adsorption site of the emitting atoms, and that a study of these effects should produce a method of surface structure analysis for the location of preferred surface adsorption sites. This approach would appear to be an improvement over LEED because of its high sensitivity to structural changes and because it does not require long range order in the adsorbate layer.     

Transmission electron microscopy studies of femtosecond laser induced modifications in quartz

Cross-sectional transmission electron microscopy investigations of femtosecond laser induced sub-micrometer structural modifications inside crystalline quartz were carried out. Modifications from single laser shots and from lines built of overlapping shots were imaged. Both single laser shot modifications and line structures show an amorphous core surrounded by a disturbed crystalline structure. A strong strain field surrounding the central, irradiated, core is responsible for an increase of the refractive index. Finite element method calculations of the strain field show maxima on both sides of the irradiated core, which are in good agreement with optical measurements of the refractive-index change. Received: 29 September 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002 RID="*" ID="*"Corresponding author. Fax: +49-3641/947792, E-mail: tatiana.gorelik@rz.uni-jena.de     

飞秒激光烧蚀硅表面产生等离子体的发射光谱研究

对中心波长为800 nm,脉宽为100 fs的激光脉冲烧蚀空气中硅(111)产生的等离子体发射光谱进行了时间和空间分辨研究. 结果表明,在等离子体羽膨胀初期(小于50 ns时间范围内),等离子体发射光谱主要由连续光谱构成,此后连续光谱强度逐渐减弱,线状光谱开始占主导地位;在羽体膨胀过程中离子谱线的存在时间短于原子谱线的存在时间. 由时间分辨发射光谱发现在羽体膨胀过程中等离子体辐射波长存在红移现象,波长红移量随时间演化呈二次指数衰减. 最后给出等离子体发射光谱谱线强度的时空演化规律. 关键词： 飞秒激光 脉冲激光烧蚀 等离子体 发射光谱     

Anomalous electron emission spectra and polarization phenomena in a lead magnesium niobate single crystal

The time dependences of the intensity and the energy positions of fine-structure of the spectra of anomalous electron emission from a polarized lead magnesium niobate (PMN) single crystal irradiated with soft x-rays are investigated experimentally. It is shown that the relaxation time of the electret charge can be determined from the graphs of these dependences, and the depth distribution of the potential in the surface layer of the sample can be determined from the profile of the anomalous electron emission spectrum. Estimates of the fields in the surface layers of a polarized PMN single crystal, obtained from the characteristics of the anomalous electron emission spectra, agree with data obtained by electrophysical research techniques. Fiz. Tverd. Tela (St. Petersburg) 39, 1446–1451 (August 1997)