Au表面等离子体激元激发的扫描探针电子能谱

结合扫描隧道显微镜（STM）与电子能谱仪是实现表面微区元素分析的途径之一．我们将环形电子能量分析器和三维扫描探针系统相结合,建立了一台扫描探针电子能谱仪(SPEES)．通过测量针尖近场发射束流激发的Au表面能量损失谱,我们用研究了Au原子的等离子体激元激发现象．进一步通过改变针尖－样品距离,我们研究了Au等离子体激元峰与弹性散射峰的强度比随针尖－样品距离变化的关系．研究结果发现该强度比与针尖－样品距离的关系并不是单调变化,而是在一个特定位置存在极大．     

Determination of the intrinsic bulk and surface plasmon intensity of XPS spectra of magnesium

Separation of intrinsic and extrinsic intensity contributions to plasmon peaks in X-ray photoelectron spectra of free-electron like metals (Me) such as Be, Na, Mg, Al and semiconductors as Si and Ge, necessary for the accurate determination of the thickness of overlayers in the range of a few nanometers, and their composition, is difficult because of their more or less coincident energies. The intrinsic bulk and surface plasmon contributions to Me 2p spectra can be determined separately from the intensities of the metallic and oxidic main peak as obtained from a series of spectra recorded from the unoxidised metal and the oxidised metal with different oxide-film thicknesses. In the present work, this method was applied to XPS Mg 2p spectra. It was shown that the method is very sensitive to deviations in the measured data, and therefore a careful error analysis is required, which has been developed in this work. Furthermore, an alternative method based on the same theory was proposed. This method yielded values of 0.17 and 0.06 for the intrinsic bulk and surface plasmon contributions to the Mg 2p spectrum relative to the Mg 2p main peak for a detection angle of 45°. It was demonstrated that the values obtained for the intrinsic bulk and surface excitation contributions determined according to both methods depend on the oxide-thickness range investigated. This observation indicates that commonly applied simplifying assumptions for the oxidation behaviour of Mg, like a layer-by-layer growth mechanism and/or the development of a homogeneous oxide with bulk MgO properties, as for composition and band gap values, do not hold. The pronounced effect of neglect of the intrinsic plasmon intensity contributions on the thickness values determined for MgO films on Mg was shown.     

Energy dependence of electron energy loss processes in Ge 2s photoemission

Deep core Ge 2s photoelectron spectra from polycrystalline Ge films induced by monochromatic synchrotron radiation, of 4, 6 and 8 keV were measured and analysed using two different methods, the partial intensity analysis and the extended Hüfner method to determine the spectral contributions from different electron energy loss processes due to bulk extrinsic, intrinsic and surface excitations. The obtained photon energy dependence of the ratio of these contributions was compared as a function of the photoelectron kinetic energy. It was found that the relative contribution of intrinsic excitations increase with the photon energy.     

Asymptotic behavior of energy band associated with a negative energy level

The mathematical foundation of the tight binding approximation is given. If ₀ is a negative energy level of a real potentialq, then there exists an energy band for a one-dimensional chain with period 2T of the same atoms which lies near ₀. We study this band whenT tends to infinity.On leave of absence from the Department of Physics, Leningrad State University, Leningrad, USSR.     

低能质子束在氢等离子体中的能损研究

实验测量了100 keV的质子束穿过部分电离氢等离子体靶后的能量损失. 等离子体靶由气体放电方式产生, 其自由电子密度在10¹⁶ cm^-3量级, 电子温度约1–2 eV, 维持时间在微秒量级. 研究结果表明: 质子束在等离子体靶中的能量损失与自由电子密度密切相关且明显大于在同密度条件下中性气体靶中的能量损失; 在自由电子密度达到峰值处, 通过实验结果计算得到此时的自由电子库仑对数约为10.8, 与理论计算结果符合较好, 该值比Bethe公式给出的中性气体靶中束缚电子库仑对数高4.3倍,相应的能损增强因子为2.9.     

Comparison of intrinsic zero-energy loss and Shirley-type background corrected profiles of XPS spectra for quantitative surface analysis: Study of Cr, Mn and Fe oxides

The intrinsic zero-energy loss profiles of transition metal 2p and 3p XPS spectra for Cr, Mn, and Fe oxides are obtained by spectral deconvolution and compared with Shirley-type background corrected profiles. The metal core level spectra are deconvoluted by O 1s spectra as the response function of each oxide. As the O 1s spectra include intrinsic and extrinsic energy loss parts, the background corrected core level spectra are zero-energy loss spectra. The good agreement of the deconvoluted spectra with the reported spectra obtained by the many body effect theory indicates that the background subtraction method is accurate. A comparison of the deconvoluted with the background corrected spectra of the Shirely-type subtraction reveals that almost all the spectra coincide with each other except for Fe 3p with -Fe₂O₃. The good coincidence of the Shirley-type corrected spectra with the deconvoluted and calculated spectra indicates that Shirley-type background correction can be used for daily quantitative surface analysis.     

Investigation of the characteristic energy losses of platinum (111)

With the help of a combined LEED- and Auger-investigation, the surface of a platinum (111) crystal was cleaned first. Then, the spectrum of the characteristic energy losses for both contaminated and cleaned surfaces is studied. On the cleaned surface the following losses were found: ΔE ₁=7.4 eV, ΔE ₂=13.5 eV, ΔE ₃=24.8 eV, ΔE ₄=31.8 eV, ΔE ₅=45.1 eV, ΔE ₆=54.1 eV, ΔE ₇=71.2 eV. The present results are compared with the measurement of other investigators. In particular, in good agreement with optical measurements we identify ΔE ₁ and ΔE ₂ as interband transitions, and ΔE ₃ and ΔE ₄ as surface and volume plasma loss, respectively.     

Electronic properties of metallic bilayers deposited on Cu(1 1 1): A comparative study

The nature and the dispersion of the electronic collective excitations in different metal bilayers (Na, Ca, Ag) deposited onto the Cu(1 1 1) surface were investigated by angle-resolved electron energy loss spectroscopy. We found a nearly-flat behavior of the surface plasmon energy (absence of dispersion) in Ca and Ag bilayers, characterized by the presence of d electrons, in good agreement with theoretical predictions within the framework of the s-d polarization model. On the contrary, an initial negative dispersion was observed in the Na bilayer. The intensity of the surface plasmon was vanishing in the long-wavelength limit in all cases.     

Surface plasmon resonance of Ag nanoparticles in the vicinity of a high impedance surface

Surface Plasmon resonance of Ag nanoparticles in the vicinity of a high impedance surface is investigated. Mushroom-like nanostructures were vertically grown on silicon substrate to form a high impedance surface operating in the range of optical frequencies. Formation of Ag nanoparticles on the fabricated high impedance surface was realized using plasma bombardment process. Optical measurements show an enhancement in the surface plasmon resonances of Ag nanoparticles. Also it was shown that the plasmon resonance peak of the Ag nanoparticles shifts to blue when Ag nanoparticles approach to the high impedance surface.     

Ni25+离子1s23s-1s2np跃迁的全能域理论研究

用全实加关联方法计算了Ni25+离子1s23s和1s2np (n  9)态的能量.通过引入价电子的有效核电荷,在类氢近似下,估算了对能量的高阶相对论修正和QED修正.计算了该离子1s23s-1s2np的跃迁能,波长和在三种规范下的振子强度.依据量子亏损理论,确定了Rydberg系列1s2np的量子数亏损,据此可以实现对任意高激发态(n  10)的能量的可靠预言;得到该离子从1s23s态到电离阈附近高激发1s2np态间的跃迁振子强度以及到相应连续态跃迁的振子强度密度.     

On ionization energy losses of high-energy electron–positron pair in thin targets

The present Letter deals with consideration of high-energy electron–positron pair ionization losses in thin dielectric plate which it traverses after being emitted from substance where it is created. It is shown that in this case the Chudakov effect of reduction of pair energy losses takes place on much larger distance from its creation point than in the case of the pair motion in homogeneous infinite medium. It is demonstrated that due to transition radiation which appears during the pair emission from the substance the ratio of the pair energy losses in two plates situated on different distances from it is noticeably different from the case when the radiation is neglected.     

Fe23+离子1s22s-1s2np的跃迁能和偶极振子强度

用全实加关联方法计算了类锂Fe23 离子1s22s-1s2np(2≤n≤9)的跃迁能和1s2np(n≤9)态的精细结构.依据单通道量子亏损理论,确定了Rydberg系列1s2np的量子数亏损.用这些作为能量的缓变函数的量子亏损,可以实现对任意高激发态(n≥10)的能量的可靠预言.用在计算能量过程中确定的波函数,计算了Fe23 离子1s22s-1s2np(2≤n≤9)跃迁的振子强度.将这些分立态振子强度与单通道量子亏损理论相结合,得到该离子从基态到电离阈附近高激发束缚态间的偶极跃迁振子强度以及束缚态-连续态跃迁的振子强度密度,从而将Fe23 离子的这一重要光谱特性的理论预言外推到整个能域.     

Track structure in dielectric and semiconductor single crystals irradiated by heavy ions with high level of inelastic energy losses

The phenomenological model of the track formation processes during a heavy ion passing through materials is discussed. This model is based on the scanning tunneling and electronic microscopy investigations of diamond single crystals and stainless steel subjected to ⁴⁰Ar, ⁸⁴Kr and ¹²⁹Xe ion irradiation with energies in the MeV region. The energy and temperature criteria when crater formation on the surface during the heavy ion irradiation takes place are introduced.     

Pair neutrino energy loss for nuclei 56Fe at the late stages of stellar evolution

Based on the Weinberg-Salam theory,the pair neutrino energy loss rates for nuclei 56Fe are canvassed for the wide range of density and temperature.The results of ours (QLJ) are compared with those of Beaudet G,Petrosian V and Salpeter E.E's (QBPS),and it shows that the pair neutrino energy loss rates of QBPS are always larger than QLJ .The QBPS is 12.57%,12.86%,14.99%,19.80% times higher than QLJ corresponding to the temperature T9=0.385,1.0,5.0,10,respectively.     

陆架斜坡海域上坡波导环境中声能量急剧下降现象及其定量分析

深度较浅的声源其辐射声波在陆架斜坡海域上坡传播时,在斜坡顶端会出现声能量急剧下降现象.利用射线声学模型分析了造成这一现象的原因,并根据抛物方程声场模型计算的深海和浅海平均传播损失定义了"声能量急剧下降距离",定量分析了声源位置对该现象的影响.结果表明:声源深度对"声能量急剧下降距离"影响较大,而声源与斜坡底端水平距离对其影响较小;当声源深度变大时,部分掠射角较小的声线最终能够达到斜坡顶端,致使"声能量急剧下降距离"增大,继续增加声源深度,将导致上坡声能量急剧下降现象消失.利用抛物方程声场模型对陆架斜坡海域上坡声传播进行数值仿真,结合"声能量急剧下降距离"的定义,计算并比较了声源位置不同时该距离的变化,数值计算结果验证了理论分析.     

Determination of the K adsorption site on Fe(1 1 0) with XSW

We have used X-ray standing waves (XSW) in near normal incidence to determine the K–Fe bond length and the adsorption site of K at the saturation coverage at room temperature on the Fe(1 1 0) surface. Three different scattering geometries were used to enable the determination of the adsorption site by triangulation. From the results we conclude that the potassium atoms adsorb in a distorted hexagonal overlayer. The Fe–K distance, as determined from the measurements in the (2 2 0) Bragg reflection, is 3.4±0.2 Å. The long bridge site seems to be the preferred adsorption site for the potassium atoms in the distorted hexagonal overlayer. This geometry not only fits all the XSW data, but also explains all spots in the LEED pattern without the need to introduce multiple scattering. Comparison of the measured and simulated XSW data, based on the distorted hexagonal overlayer, enables a more accurate determination of the Fe–K bond length to 3.36±0.14 Å. This corresponds to a potassium hard sphere radius of r_K=2.12±0.14 Å. This radius is among the largest reported for potassium on a metal, which is attributed to the high coverage and coordination of the K atoms in this overlayer arrangement.     

碳原子1s22s22pns 3P态的能量和波函数

提出了构造碳原子1s22s22pns 3P态波函数的新方法,以Rayleigh-Ritz变分法为基础开发了一套计算碳原子1s22s22pns 3P态波函数和能量的Mathemtica程序,具体计算了碳原子1s22s22pns 3P(n=3-6)态的波函数和非相对论能量及其相对论修正值(包括质量修正、单体达尔文修正、双体达尔文修正、自旋-自旋接触相互作用修正),计算结果与实验值非常接近。     

Unusual line shape of B 1s core level spectra in rare earth hexaborides

We investigate the B 1s core level spectra of hexaborides, (, Ce, Pr, Nd), using high resolution X-ray photoemission spectroscopy. While all the B sites are identical, the experimental spectra exhibit a signature of multiple features manifested as an unusual asymmetry in the lower binding energy side. The analysis of the spectra reveals that the surface and bulk photoemission signals are different. In addition, the peak position shifts towards lower binding energies with the increase in 4f binding energy of the rare earth elements that can be attributed to the chemical potential shift due to lower degree of 4f-conduction electron hybridization. Decrease in temperature leads to a narrowing of the linewidth in every case. The Kondo systems exhibit more prominent narrowing of the B 1s linewidth.     

Scintillation response of Ce-doped or intrinsic scintillating crystals in the range up to 1 MeV

A hybrid photomultiplier (HPMT) was used to study the scintillation response {N_phels(E) photoelectron and L.Y.(E) light yields and energy resolutions} of various known or newly developed scintillators—namely, Ce-doped crystals (perovskites or garnets), CsI(Tl) and the intrinsic BGO crystal—at different energies in the range 8 keV–1.33 MeV. Detailed comparative studies of the scintillation properties of these crystals are presented. A newly developed fast and heavy LuAG:Ce scintillator is characterized by about a 50% higher L.Y. compared to that of well-known and popular BGO (roughly 12 500 ph/MeV against 8080 ph/MeV, respectively).     

300 eV—1GeV质子在硅中非电离能损的计算

非电离能损(NIEL)引起的位移损伤是导致空间辐射环境中新型光电器件失效的主要因素.引起质子在硅中NIEL的作用机理有库仑相互作用和核相互作用,质子能量范围从位移损伤阈能到1 GeV.当质子能量位于低能区时,库仑相互作用占主导地位,采用解析方法和TRIM程序计算NIEL;当质子能量位于高能区时,NIEL主要来自质子与靶原子核的弹性和非弹性相互作用,使用MCNPX/HTAPE3X进行模拟仿真计算由核反应引起的NIEL.实现了能量范围为300 eV—1 GeV的质子入射硅时NIEL的计算.计算结果表明,MCNPX/HTAPE3X可用于计算高能质子在材料中产生的反冲核所引起的NIEL,结合解析方法和TRIM程序可计算得到由于库仑相互作用引起的NIEL.