Calculation of H+-ranges and H+-range stragglings in the energy region 1–1000 keV

The use of various approximations in calculating proton projected ranges has been studied by the analytical and the Monte Carlo methods. A correction is presented for the projected ranges given in the compilation (Andersen and Ziegler: Hydrogen Stopping Powers and Ranges in All Elements). The greatest correction factors at 1, 10, 100 and 1000 keV are 3.5, 2.1, 1.4 and 1.2, respectively. The corrections result from the inclusion of the tabulated electronic stopping power values in the calculation of the projected ránge to the total range ratio and from the estimation of the effect of the reflection. The Monte Carlo calculations show the electronic straggling to be a remarkable factor in the width of the proton range distributions at reduced energies larger than of the order of 100.     

Ionization of M subshells of Pb atoms by electron impact in an energy range of 5–30 keV

The relative intensities of the M ₅ N and M ₄ N satellites of Pb under electron bombardment of thick targets in the range of accelerating voltages U = 5?30 kV are experimentally investigated. Based on the previously proposed model of M X-ray emission, the relative intensities of these satellites are calculated using the total ionization cross sections of M subshells under electron impact found in different approximations. It is established that, among the models yielding analytical expressions for calculating total ionization cross sections, the model of classical binary collisions provides the best agreement with experimental data in the electron energy range under study. The parameters of the semiempirical Bethe formula for calculating the ionization cross sections of Pb M subshells under electron impact are determined.     

Transmission of ∼10 keV electron beams through thin ceramic foils: Measurements and Monte Carlo simulations of electron energy distribution functions

Electron beams with particle energy of ~10 keV were sent through 300 nm thick ceramic (Si₃N₄ + SiO₂) foils and the resulting electron energy distribution functions were recorded using a retarding grid technique. The results are compared with Monte Carlo simulations performed with two publicly available packages, Geant4 and Casino v2.42. It is demonstrated that Geant4, unlike Casino, provides electron energy distribution functions very similar to the experimental distributions. Both simulation packages provide a quite precise average energy of transmitted electrons: we demonstrate that the maximum uncertainty of the calculated values of the average energy is 6% for Geant4 and 8% for Casino, taking into account all systematic uncertainties and the discrepancies in the experimental and simulated data.     

Calculation of optical conductivity and electron energy loss spectra of YBa2Cu3O7 in the 10–160 eV range

We calculate the high frequency macroscopic dielectric function () of YBaCuO by treating the solid as a dense gas of polarizable cells. The cell polarizability is constructed from independent atomic contributions within a local-density based random phase approximation (LDRPA) and improvements thereof. In this way, interband transitions are treated very schematically but transitions from the core-like Ba 5p ⁶ shell are treated quite well. This is important, because the intense Ba 5p–5d like giant dipole resonance provides about half of the optical conductivity around 20 eV and contributes strongly to the all-valence electron plasma frequency.The calculated conductivity is in quite good agreement with experiment in magnitude and shape above 15–20 eV. The calculated EELS is similar in magnitude and shape to the experimental one but shifted to higher energies: in particular, the valence electron plasmon occurs around 33(26) eV in the calculated (experimental) EELS. This is reasonable, since the real solid involves lowlying charge transfer excitations and interband transitions which are absent in the atomic model of the YBaCuO unit cell. In the atomic model, the corresponding intensity is taken into account by higher frequency atomic transitions.     

Double-hump resonance structure of the cross sections for electron impact ionization of Ar5+

Configuration-average distorted-wave calculations are carried out for electron-impact ionization of Ar5+. Both direct ionization and the indirect excitation autoionization processes are included in our calculations. Our theoretical values are in quite reasonable agreement with the experimental data. The indirect processes contribute up to 50% to the total ionization cross sections. The possible origin of double-hump resonance structure of the cross sections is demonstrated and the contributions of metastable states are also taken into account.     

Influence of Fe on Microstructure and Physical Properties of Cu90 – xFexPd10 Ternary Alloys with x = 5, 10, 15, and 20

Physics of the Solid State - The structural and physical properties of Cu90 – xFexPd10 ternary alloys with x = 5, 10, 15, and 20 are studied using X-ray diffraction,...     

Structure determination of the Cu(0 0 1)–c(4 × 4)-Sn surface by low-energy electron diffraction

Low-energy electron diffraction (LEED) have been used to determine the Cu(0 0 1)–c(4 × 4)-Sn structure formed at 300 K. It is demonstrated that a structural model suggested by scanning tunneling microscopy observations is correct: The model consists of one substitutional Sn atom and four Sn adatoms in the unit cell. Optimum parameters of the determined c(4 × 4) structure reveal that Sn adatoms laterally are displaced by 0.30 Å away from ideal fourfold-hollow sites along the 〈100〉 directions. It is proposed that such displacements of the Sn adatoms cause the formation of a network of octagonal rings on Cu(0 0 1). The substitutional Sn atom is located at each center of the octagonal rings. The formation conditions of the network are discussed.     

Comparative Study of the Nernst–Ettingshausen Coefficient in the Normal Phase in the Y1 – xPrxBa2Cu3Oy and Y0.85 – xPrxCa0.15Ba2Cu3Oy Systems

Physics of the Solid State - The results of the comparative study of the modification of the temperature dependences of the Nernst–Ettingshausen coefficient Q in the normal phase of two...     

The scattering suppression of X-rays with energy of 20–200 keV in spectrometers with Barkla polarizers

The method is proposed for estimating the polarization parameters and the scattering suppression coefficients in energy dispersive X-ray spectrometers with Barkla polarizers (EDPXRS) for X-ray fluorescence (XRF) analysis. The scatter suppression coefficients are estimated accounting primary beam polarization, secondary beams yields, detectors response function, and partial factors. Estimations of scatter suppression coefficients due to polarization do not require the use of Stokes parameters and matrices. The method gives the possibility to make polarization-related corrections in calculations by XRF theory based on scattering cross sections of unpolarized beams. Calculations clarify early estimations of EDPXRS parameters with Barkla polarizers in the 20–200 keV range. The polarizing ability at δ = 7° deviations varies from 0.973 at 20 keV to 0.863 at 200 keV. The analyzing ability of registration system is about the same. In a simple XRF version on a synchrotron radiation with Barkla polarizer, the scattering can be decreased 60 times at 20 keV and 11 times at 80 keV with δ_s = 3°. In EDPXRS, the scatter suppression factor varies within 10–4.2 at deviations δ = 10° and within 20–4.8 at δ = 7°. The scatter suppression at low energies is determined by angular factor and background and at high energies is limited by energetic factors.     

Morphology and the Thermoelectric Properties of γ-GdxDy1 – xS1.5 – y Solid Solution Ceramics

Physics of the Solid State - The temperature dependences of the Seebeck coefficient, the electrical conductivity (T = 300–873 K) and also the heat conductivity coefficient, and the...     

Temperature dependence of the permittivity of PbWO<Subscript>4</Subscript> crystals in the range 290–550 K

The temperature dependence of the permittivity ε of PbWO₄ crystals is studied in the range T = 290–550 K at a frequency of 1 kHz. The ε(_T) dependences measured on heating and cooling are different. On heating, groups of narrow maxima at 290–330 K and 330–400 K are observed in the ε(_T) curves. The first group of peaks is dominant. High-temperature polarization produces an additional broad peak in the ε (_T) curve at 400 K. A linear ε(_T) dependence is observed in the range 400–470 K. Above 470 K, the variation in ε(_T) closely follows an exponential law. Restoring relaxation of ε in the range 25–30 at 290 K after high-temperature sample heating proceeds exponentially in a few stages. The features of ε(_T) curves are determined by the dipole polarization and the hopping mechanism of charge exchange between complex dipole associates. Such structural defects may be pairs of doubly charged lead and oxygen vacancies (diplons). These defects also form a basis for more complicated defect complexes with localized holes (or electrons) at the corresponding vacancies.     

On the superconductivity and structural properties of YBa2Cu3 − xCdxO7 − y

A series of superconducting cuprates with the nominal composition YBa₂Cu_3 − xCd_xO_7 − yand the effect of Cd substitution on Cu sites in this compound is presented. X-ray powder diffraction patterns for these cadmium cuprates with reduced diamagnetism indicate an orthorhombic unit cell like-perovskite structure for (0 ≤ x ≤ 0.15), while for higher Cd concentration, i.e.x = 1.0 the material is polyphasic. The observed superconducting transition temperature of the samples is nearly the same ([formula] K), except for (x = 1.0) whereT_cdrops to 72 K and a transition from metallic to semiconducting behavior of the normal state of the resistivity is observed. Such a decrease inT_cfor higher Cd concentration could be attributed to the presence of the green phase in this composition.     

Excitation of projectile Rydberg states in the collisions Be+-He and Mg+-He, 10–75 keV

The photoabsorption coefficient of molecular oxygen has been measured at 1215.70 Å and in the ranges 1205 Å–1214 Å and 1218 Å–1225 Å with an average resolution of ±0.015 Å. The light source in this experiment was the Doppler shifted radiation obtained from Stark quenching of a metastable hydrogen beam with energies between 2 keV and 60 keV. Using observation angles of 45°, 90°, and 135° with respect to the beam the above mentioned tuning ranges are obtained. Our data join smoothly to those of Ogawa [1] in the range 1214 Å–1218 Å and are in fair agreement with earlier measurements in other laboratories. Analytical expressions for the absorption coefficient for use in geophysical applications are presented for the whole wavelength range 1205 Å–1225 Å. Rotational structure of the absorption coefficient in the range 1220 Å–1223 Å arising from the 3-0 band of theα ¹ ∑ _u ⁺ -X ³ ∑ _g ^? forbidden transition in molecular oxygen is clearly resolved in the present measurements. A transition probability ofA=4×10⁴ s^?1 is obtained for this system. A careful study of a possible pressure dependence of the absorption coefficient was made. Except from the region were rotational line absorption occurs and the single point at 1215.70 Å no measurable effect was found for pressures below 100 Torr.     

Parametric Model of the Optical Constant Spectra of Hg1 – xCdxTe and Determination of the Compound Composition

Optics and Spectroscopy - A parametric model describing the spectra of optical constants n(λ) and k(λ) of a Hg1&nbsp;–&nbsp;xCdxTe (MCT) solid solution for the x values in...     

Temperature dependence of twinning stress – Analogy between Cu–Ni–Al and Ni–Mn–Ga shape memory single crystals

Abstract

To obtain a direct non-magnetic analogy to Ni–Mn–Ga 10M martensite with highly mobile twin boundaries, we present the recalculation of twinning systems in Cu–Ni–Al martensite. In this approach, the twinning planes denoted as Type I, Type II and compound have similar orientations for both alloys (Ni–Mn–Ga and Cu–Ni–Al). In Cu–Ni–Al, compound twinning exhibits the twinning stress of 1 to 2 MPa comparable to twining stress of Ni–Mn–Ga. In contrast Type II twinning stress of Cu–Ni–Al is approximately 20 MPa, i.e. much higher than twinning stress for Type II in Ni–Mn–Ga (0.1 to 0.3 MPa). Similarly to Ni–Mn–Ga, the twinning stress of Type II in Cu–Ni–Al is temperature independent. Moreover, no temperature dependence was found also for compound twinning in Cu–Ni–Al.     

Synthesis and X-ray Diffraction Studies of Cu2ZnGexSn1 – xSe4 Solid Solutions

Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - Quaternary compounds (Cu2ZnGeSe4 and Cu2ZnSnSe4) and solid solutions on their basis are prepared via single-temperature...     

Quantum Fluctuations in FexMn1 – xSi with Inclusion of the LDA + U + SO Calculations of the Electronic Structure

Physics of the Solid State - Quantum spin fluctuations are studied in chiral helicoidal FexMn1&nbsp;–&nbsp;xSi ferromagnets on the basis of the direct calculations of the electronic...