Electron mobility of Sr1-xLaxTiO3 ceramics between 600 °C and 1300 °C

1-x La_xO₃ ceramics (0.003<x<0.40) were measured between 600 °C and 1300 °C. The density of electrons in the conduction band was determined from Hall and thermopower measurements. A chemical approach (Ti³⁺-titration) confirmed these results. The electron mobility was calculated by combining charge carrier density and conductivity data. The temperature dependence of the mobility obeys a power law. Its exponent varies from -1.5 for slightly doped samples (x=0.003) to -2.74 for lanthanum-rich samples (x=0.4) indicating a phonon scattering controlled transport behavior. The mobility data obtained from slightly doped ceramic samples agree very well with Hall mobilities found in undoped SrTiO₃ single crystals. Received: 22 January 1997/Accepted: 1 April 1997     

Raman optical activity spectra: basis set and electron correlation effects

Raman and vibrational Raman optical activity (ROA) spectra have been calculated for three molecules: H₂O₂, CHDTF and CHDTOH. The effects of electron correlation on the ROA parameters of these relatively small systems have been investigated by means of the multiconfigurational self-consistent field (SCF) approach. A range of correlation-consistent basis sets has been used in the calculations. The basis set convergence of the calculated ROA parameters is fairly well achieved when sets of at least d-aug-cc-pVTZ quality are used. On the other hand, the aug-cc-pVDZ set seems to be sufficient for a qualitative analysis. Diffuse functions, possibly a double set, are essential to ensure a good quality of the calculated ROA spectrum. In most cases the sign and approximate magnitude of the ROA are correctly predicted at the SCF level, and the corresponding ROA spectra should be considered qualitatively accurate.     

Mutual experimental and theoretical validation of bulk photoemission spectra of Sr1-xCaxVO3

We report high-resolution high-energy photoemission spectra together with parameter-free LDA + DMFT (local density approximation + dynamical mean-field theory) results for Sr1-xCaxVO3, a prototype 3d(1) system. In contrast to earlier investigations the bulk spectra are found to be insensitive to x. The good agreement between experiment and theory confirms the bulk sensitivity of the high-energy photoemission spectra.     

A correlation between manifestations of the magnetoplastic effect and changes in the electron paramagnetic resonance spectra after quenching of NaCl: Eu single crystals

The electron paramagnetic resonance (EPR) spectra of Eu²⁺ impurity ions in NaCl: Eu single crystals are investigated. It is found that the intensity of the EPR spectra undergoes prolonged (～200 h) multistage variations after quenching of NaCl: Eu single crystals. The variations observed in the EPR signal intensity are explained by the aggregation of impurity-vacancy dipoles into complexes. It is revealed that the magnetoplastic effect (a change in the microhardness in a magnetic field with an induction of 6 T) in these crystals manifests itself at an intermediate stage of impurity aggregation when all individual impurity-vacancy dipoles are temporarily stabilized in the sample. This can be associated with the thermally activated transformation of the internal atomic structure in the majority of already existing complexes.     

Anisotropy of plasmon dispersion in Al: An electron correlation effect

Electron energy-loss spectroscopy of epitaxial Al films shows a small, but well-established anisotropy of the plasmon dispersion. This cannot be explained within the random-phase approximation (RPA). Anisotropic electron exchange correlations, caused by the lattice pseudopotential, account qualitatively for the observed differences of dispersion.     

Incident-energy dependence of 3p electron energy-loss spectra of nickel

The intensities of two features in the 3p electron energy-loss spectrum of nickel, a dip prior to the threshold and a satellite ～ 12 eV above the threshold, are observed to systematically decrease as the incident electron energy is lowered from 1000 to 150 eV. These intensity changes indicate a dependence of the matrix elements for each excitation on momentum transfer as the incident energy is decreased, in part through changes in the strength of Fano interference near threshold.     

Calibration of electron spectra

Energy calibration procedures, which have been used in ESCA, are reviewed. Binding energies of calibration lines suitable for solid and for gaseous samples have been determined. Charging effects of nonconducting samples have been investigated for different X-radiation, sample thickness and material. A calibration relative to lines from some insulating standard compound mixed into the sample was shown to be unreliable, while experiments indicated that in calibrating relative to a surface layer, the carbon line from the hydrocarbon contamination layer can be used as well as a line from a thick layer of a noble metal on a part of the sample.     

Substitution effect of Ba at the Sr sites in Sr(Fe,Re)O3

We study ?-meson production in nuclei to investigate the in-medium modification of the ?-meson spectral function at finite density. We consider ( ${\bar p},\phi$ ), (γ,p) and (π ^???, n) reactions to produce a ?-meson inside the nucleus and evaluate the effects of the medium modifications to reaction cross sections. The structures of the bound states, ?-mesic nuclei, are also studied. For strong absorptive interaction cases, we need to know the spectrum shape in a wide energy region to deduce the properties of ?.     

电子关联对类铍离子1s~22s2p~3P_(0,1)能级的超精细结构常数的影响

基于MCDF方法系统地计算了Z=20~83范围内24个类铍离子的1s22s2p3P0,1态的精细结构,得到了与其它理论和实验符合很好的结果.在此基础上,进一步计算了超精细结构对角及非对角常数,并分析了不同电子关联效应和Breit相互作用对它们的影响.     

Size effect on low-lying energy spectra of an electron magnetic quantum ring

We present numerical results for the low-lying spectra of an electron confined in a magnetic quantum ring where the magnetic fields are zero inside the ring and constant elsewhere. Low-lying spectra for both on-center Coulomb acceptor and donor impurities, with qualitative aspects different from those without impurities doped, are also discussed.     

The electron impact spectra of the fluoromethanes

The electron impact spectra of methane, methyl fluoride, methylene fluoride, fluoroform, and tetrafluoromethane have been obtained out to 22 eV energy loss using electrons incident at 400 eV and scattered through small angles (0–2°). Combining the major features of these spectra with the molecular ionization potentials determined by photoelectron spectroscopy allows consistent assignments of the bound transitions to be made involving the uppermost three or four filled molecular orbitals and the lowermost two or three Rydberg levels. The assignments follow naturally from the constancy of Rydberg term values and considerations of intensity.     

Dissociative recombination of 3HeH+: comparison of spectra obtained with 100, 10 and 1 meV temperature electron beams

The heavy-ion storage ring CRYRING at the Manne Siegbahn Laboratory at Stockholm University has been used for the study of dissociative recombination of ³HeH⁺. The new adiabatically expanded electron beam at CRYRING, which is achieved by means of a superconducting magnet, was used. The electron-beam expansion factor of 100 gave a transverse electron temperature of about 1 meV. This allowed the observation of several new resonances in the recombination cross-section. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cu掺杂La0.67Sr0.33CuxMn1-xO3薄膜的光诱导效应研究

分别采用溶胶-凝胶和射频磁控溅射的方法制备了La0.67Sr0.33CuxMn1-xO3(x=0.05, 0.10和0.15)系列块材和薄膜,研究了Cu部分替代对薄膜光诱导特性的影响.实验结果表明随着Cu掺杂量的增加,薄膜的金属-绝缘转变温度向低温方向移动,且导电性降低.在金属相激光作用诱导电阻增大.光致电阻相对变化极大值随着Cu含量的增加而增大,当x =0.15时,光致电阻相对变化极大值达到58.3%,分析可能是由激光辐照诱导电子束缚于CuO2链外的局域态和晶格效应共同作用的结果.     

Spontaneous photorefractive effect in Sr1−x CaxTiO3 (x=0.014)

The temperature dependence of the principal values of the refractive index in Sr_1−x Ca_xTiO₃ (x=0.014) has been measured in the 17–275 K range under various conditions of sample illumination with 1.96 eV photons. The spontaneous photorefractive contribution δn ^ph to the temperature-induced variation of the refractive index of Sr_1−x Ca_xTiO₃, which appears after illumination of the sample in the ferrophase (transition temperature T _c=32 K) and persists in the paraphase under heating up to 150 K, has been separated. The photoinduced polarization has been estimated. Fiz. Tverd. Tela (St. Petersburg) 39, 711–713 (April 1997)     

Transition probability effect on the shape of electron energy distribution in X-ray electron spectra of copper,silver and palladium

Electron spectra of valence bands in copper, silver and palladium were calculated. It is shown that the probability of electron excitation from e_g states exceeds that from t_2g states. The density of electron states in the valence bands of these crystals differs markedly from the photoelectron energy distribution.