Crystal structures of double calcium and alkali metal phosphates Ca10 M(PO4)7(M = Li, Na, K)

Crystal structures of double calcium and alkali metal phosphates described by the general formula Ca₁₀ M(PO₄)₇(M = Li, Na, K) have been studied by the Rietveld method. The lattice parameters are a = 10.4203(1) and c = 37.389(1) Å (for M = Li), a = 10.4391(1) and c = 37.310(1) Å (for M = Na), and a = 10.4229(1) and c = 37.279(2) Å (for M = K); sp. gr. R3c, Z = 6. The specific features of the distribution of alkali metal cations over the structure positions are discussed.     

X-ray photoelectron spectroscopy of FeP phosphide

The structure of the outer and inner electron spectra of iron (2p, 3p, 3s, and 3d) and phosphorus (3s and 3p) atoms in FeP monophosphide is studied in detail by the X-ray photoelectron spectroscopy (XPS) method. On the basis of the analysis of the binding energy of electrons, as well as the parameters characterizing the structure of experimental spectra, a conclusion is made that Fe³⁺ (d ⁵) cations in FeP are stabilized in a state with intermediate value of the total spin (IS, S = 3/2). The range of values of intra-atomic parameters (10Dq, J _H ) is established in which the consideration of the high degree of covalence of Fe–P bonds may lead to the stabilization of (FeP₆)^15– clusters in the IS state.     

n-changing collisions of Rydberg atoms with ground-state atoms

The inelastic transitions between hydrogenic energy levels of a Rydberg atom induced in collisions with ground-state atoms are considered. The corresponding transition probability and cross section are calculated using the Fermi pseudopotential to describe the atom-Rydberg-atom interaction and a quasiclassical expression for the density distribution of the Rydberg electron.     

One-electron capture from the inner shells in atom-multicharged ion collisions

The electron capture from the inner atomic shells by multiply charged ions at intermediate and high collision energies is considered. The cross section scaling laws, as well as the reduced energy parameter, are discussed. Universal curves for the reduced cross section versus the reduced collision energy are presented for electron capture from the K, L and M shells of Ar atoms colliding with multiply charged ions. A comparison of theoretical results with the existing experimental data is given.     

Asymptotic behavior of charge-exchange amplitude

The eikonal approximation in the distorted wave formalism is modified for application to three-particle scattering with rearrangement in the region in which neither the Born nor the adiabatic approximation is valid. The long-range effects due to Coulomb interaction between the particles in both the entrance and exit reaction channels are investigated. The leading asymptotic term (in the large impact parameter) of the eikonal charge exchange amplitude is calculated for transitions betweens states of atoms. It is shown that the general expression for the amplitude correctly describes both limiting casesvv ₀ andvv ₀.State University, Uzhgorod; P. N. Lebedev Physics Institute, USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 91, No. 1, pp. 66–82, April, 1992.     

Study of the structural quality of heteroepitaxial silicon-on-sapphire structures by high-resolution X-ray diffraction,X-ray reflectivity,and electron microscopy

Heteroepitaxial silicon-on-sapphire (SOS) structures have been studied by high-resolution X-ray diffraction, X-ray reflectivity, electron microscopy, and electron diffraction. These methods yielded a large amount of complementary data on the defect structure of both the sapphire substrate and the silicon film, including integral and local (at the atomic-resolution level) information about the substrate, film, and sapphire-silicon interface.     

Electron-microscopy study of the distribution of dopants (Ta) in Si-C nanocomposite films

At present, silicon-carbon nanocomposites (NCs) are used in everyday life as hardwearing anticorrosive coatings, because they have a very high diffusion barrier. In addition, the electrical conductivity of a film can be changed by incorporating metal impurities into a NC structure because of its porosity; in this case, the physicochemical properties are retained. The aim of this paper is to study a model of metal-impurity (Ta) incorporation into a Si-C NC matrix using methods of analytical transmission electron microscopy. An understanding of this problem gives an opportunity not only to obtain information on how the metal is incorporated into the NC matrix, but also serves as the first step toward controlling electrical conduction in these structures.