Low energy electron spectroscopy of CO in the 10.600–14.400 eV energy loss range

Excitation spectra of CO have been obtained at low electron impact energy in the 10.600–13.400 eV energy loss range for scattering angles from 10 to 120°, with a 35 meV experimental resolution. The angular behaviour of the observed peaks is used to discriminate singlet-singlet and singlet-triplet transitions. Previously calculated Rydberg states are observed, in particular the triplet analogue of the F¹Σ⁺ state. A new high energy valence triplet state is identified; the first observed vibrational level is at 11.595 eV and the vibrational spacing is 90 meV. Upper levels are strongly affected by predissociation.     

Electron inelastic interactions in bioorganic compounds in the energy range of 20–10000 eV

Systematic calculations of stopping powers (SPs) and mean free paths (MFPs) for 10 bioorganic compounds have been performed for electrons with energies lower than 10 keV, based on dielectric response theory and Penn’s statistical approximation. The exchange effect is also taken into account in the calculations. An empirical approach to obtain an optical energy loss function is presented for those organic compounds without available optical data. Using this method, the calculated values of the optical energy loss function are in good agreement with experimental data. Comparisons of SP and MFP values derived in this study with other published values are presented. Using the described model, the calculated mean ionization potentials agree well with the predictions from Bragg’s rule and the calculated SPs have also been compared with the Bethe–Bloch results at an energy of 10 keV. PACS 34.50.Bw; 61.82.Pv     

Photoelectron asymmetry parameters and branching ratios for sulfur dioxide in the photon energy range 14–25 eV

Triply differential photoelectron spectroscopy has been performed in the photon energy range 14–25 eV for sulfur dioxide. The results are presented in the form of electronic branching ratios and asymmetry parameters, and are discussed briefly in the context of similar data for CO₂ and of the inner-shell spectra of SO₂.     

Electrorheological effects in carbon, barium titanate, and nickel coated with barium titanate suspensions

Effects of the electric field on the rheology, electrorheological (ER) effects, are investigated on carbon, barium titanate (BaTiO₃) and BaTiO₃-coated nickel (BT-Ni) suspensions. Among some electroreological properties, electric field frequency dependence of the induced shear stress (yield stress) observed for three suspensions shows a contrasting behavior. With increase in the electric field frequency, the yield stress decreases above 100 Hz in the carbon suspension, monotonously increases in the BaTiO₃ suspension, and is almost constant in the BT-Ni suspension. The difference in the frequency dependence and magnitude of the yield stress is discussed on the basis of the magnitude and relaxation time of the interfacial polarization and the effect of the particle rotation under the shear flow.     

Electron microscopy of barium strontium titanate nanostructures in the aluminum oxide matrix

Electron microscopy has revealed the mechanism of formation of barium strontium titanate nanostructures during crystallization in the bulk of pores of the aluminum matrix. The nanostructures have the form of nanotubes or nanocolumns 100–200 nm in diameter and a few microns long, which are formed by barium strontium titanate crystals 3–100 nm in size.     

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.     

Low energy electron spectroscopy of N2 in the 11.8–13.8 eV energy range

In the 11.8–13.8 eV energy range differential threshold and energy loss spectra of electrons scattered by N₂ molecules have been obtained at an incident energy of 14.3 eV and with a 30 meV experimental resolution. The study of the angular behaviour of the observed peaks permits us to distinguish between singlet-singlet and singlet-triplet transitions. The predicted F³Π_u and G³Π_u Rydberg states are observed. Also some levels of unknown triplet states are seen at 13.155, 13.395 and 13.635 eV.     

Electron mean free paths in ge in the range 70–1400 eV

Accurate values of the electron inelastic scattering mean free path, λ(E), in amorphous germanium have been measured in the electron energy range 70–1400 eV and are compared with other experimental values for Si, GeO₂, and SiO₂. The data are also compared with predictions from a variety of theoretical models.     

Air shower universality in the energy range of 1014 to 1022 eV

Universality in the development of air showers initiated by photons and the nuclei of cosmic rays is studied over a wide range of energies (10¹⁴–10²² eV). The scaling invariance of the lateral distribution of electrons and the universal relationship between a cascade’s age and radial scaling parameter (the root-meansquare radius of the electron component) are found to remain valid up to ultimate high energies with allowance for the Landau-Pomeranchuk-Migdal effect and interaction with the geomagnetic field. Possible applications of universality for matching, reanalyzing, and verifying the validity of data from different experiments, and for reducing the effect of the nuclear interaction model’s uncertainty on estimates of the mass composition of primary cosmic rays, are discussed.     

Electron energy loss measurements on PbF2, PbCl2, PbBr2 and PbI2

The results of electron energy loss measurements on polycrystalline films of PbF₂, PbC1₂, PbBr₂ and PbI₂ are present and the calculated dielectric functions are discussed in relation to their band structures and optical data.     

Optical constants of gold and silver clusters in the spectral range between 1.5 eV and 4.5 eV

Optical constants of gold and silver clusters of various sizes are determined from measurements of their optical extinction in the range from 1.5 eV to 4.5 eV photon energy. For this purpose, it is shown that the optical extinction by spherical clusters satisfies a Kramers-Kronig relation, yielding the second quantity needed for the determination of the complex dielectric constant ε of the cluster material. The dielectric constant is then obtained applying a generalized Newton-Raphson iteration method on the measured extinction data and the Kramers-Kronig data. The results show a clear dependence on cluster size, and also deviations from bulk dielectric constants in the range of the interband transitions. From the various ε-data, a “bulk” dielectric constant of gold and silver is obtained, which fits the positions of the cluster plasmons more precisely than bulk dielectric constants from the literature.     

Scattering of e± from N2 in the energy range 1 eV–10 keV

The differential, integrated elastic, inelastic, total, momentum transfer, viscosity, and ionisation cross sections for electron and positron scattering from the homonuclear diatomic nitrogen molecule over an incident energy range of 1?eV–10?keV are calculated using the additivity rule. Dirac partial wave analysis is employed to calculate the cross sections of the constituent atoms of molecules, using a complex optical model potential (OPM). Comparison of our results of the additivity rule with the available experimental data and other theoretical predictions is presented. Our findings produce reasonable results in intermediate and high energies.     

Electron energy loss study of TiC [111]

The electron energy loss (EEL) spectra of TiC (111) were measured over a wide range of electron primary energies. The electron energy losses below 16 eV were analyzed using the theoretical band calculations of Price and Cooper [11]. The volume and surface plasma excitations were identified from their electron primary energy dependence. Energy losses due to core electrons autoinization effects were identified above 35 eV. We observed a difference in the electronic structure of the surface vs the bulk of TiC. The temperature dependence of the EEL spectra was studied between 300 to 1250 K. The reaction of the TiC surface with ethylene and oxygen was also investigated. The ethylene bonding to the TiC surface was found to be very weak. There is evidence of the formation of surface defects on the TiC (111) surface at high temperatures.     

Electron energy loss spectroscopy study of the initial stage of lanthanum oxidation

The electron energy loss spectra (EELS) of a pure metallic lanthanum surface and variations in these spectra at the initial stages of surface oxidation were studied. The measurements were performed at primary-electron beam energies E _p from 200 to 1000 eV. A very pronounced peak at a loss energy of about 7.5 eV arises due to transitions from the La4d electronic states of the valence band into the empty La4f electronic states of the conduction band at 5.0–5.5 eV above the Fermi level. Marked changes are observed in the EELS during the oxidation of lanthanum: the peak at an energy of 7.5 eV disappears, and the peak at 13.5 eV corresponding to bulk collective energy loss in lanthanum oxide becomes more pronounced. The results obtained are discussed in terms of the electronic structure of lanthanum and lanthanum oxide.