bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic inequivalency, electron paramagnetic resonance spectroscopy, and electronic structure of the matrix-isolated (η6-C6H3F3)V half-sandwich
Authors: Mattar Saba M. , Sammynaiken Ramaswami
Published: July 2002

Magnetic inequivalency of spatially equivalent atoms, in randomly oriented molecules, is demonstrated by isolating (η6-C6H3F3)V in an Ar matrix and recording its electron paramagnetic resonance (EPR) spectrum. This is the first experimental evidence of magnetic inequivalency in an organometallic complex. Although this phenomenon should exist in all EPR spectra of rigid polyatomic molecules, the extent of its effects crucially depends on the unpaired electron distribution. The analysis of the complete EPR spectrum yields the following spin Hamiltonian parameters: gxx=gyy=1.967(3), gzz=2.012(3), |Axx(V)|=|Ayy(V)|=103.00(5)×10−4 cm−1 and |Azz(V)|=10.20(5)×10−4 cm−1. While the principal axes of the g and vanadium hyperfine tensors are parallel to the molecular symmetry axes, those of the three 19F hyperfine tensors are not aligned with one another. Consequently, their 19F hyperfine resonance positions are different and a detailed theoretical treatment of this phenomenon is required to fully comprehend and accurately simulate their EPR line shapes. The specific expressions that give rise to these magnetic inequivalencies and the g, 51V, 19F, and 1H hyperfine tensors are derived as a function of the molecular orbital (MO) coefficients. The magnitudes and signs of the MO coefficients are independently estimated by computing electronic structure of this transient using the local density functional (LDF) method. The simulation of the experimental EPR spectra followed by the comparison of the experimental and computed spin Hamiltonian tensor components reveal that the complex, when trapped in an Ar matrix at 15 K, has a 2A1 ground state. The LDF computations also predict that the molecule is metastable in the gas phase with the 2E and 2A1 states being nearly degenerate. Thus, the influence of the matrix trapping site is a decisive factor in isolating this molecule in a stable form and in determining its ground state. This also explains why the (η6-C6H3F3)V transient is difficult to isolate in high concentrations and to characterize by infrared and electronic absorption spectroscopy.
A free-energy landscape model for primary relaxation in glass-forming liquids: Rotations and dynamic heterogeneities
Authors: Diezemann Gregor
Published: July 2002

Higher order correlation functions as observed in four-dimensional NMR experiments on glass-forming liquids are interpreted in terms of a simple model for molecular reorientations. Its key assumption is an intrinsic link between the rotational and structural relaxation of the liquid. It is shown that the introduction of an additional time scale as proposed previously is not necessary. Furthermore, the model naturally accounts for a number of features associated with rotational motions in supercooled liquids. Applications of the model to other aspects of the α relaxation in supercooled liquids are discussed.
Externally corrected singles and doubles coupled cluster methods for open-shell systems
Authors: Li Xiangzhu , Peris G. , Planelles J. , Rajadall F. , Paldus J.
Published: July 2002

The idea of an externally corrected singles and doubles coupled cluster (CCSD) method using an independent source for connected triples and quadruples is generalized to open-shell high-spin states and implemented within the framework of the unitary group based CCSD method. New and more efficient programs are designed to perform cluster analysis of ab initio wave functions and to calculate corrections to standard CCSD equations. The method is applied to describe a single bond breaking of OH in the Π2 state, using both double zeta (DZ) and DZ plus polarization (DZP) basis sets. Both full or limited configuration interaction (CI) within small and carefully chosen active spaces (AS) and complete AS self-consistent-field (CASSCF) wave functions are employed as external sources for triple and quadruple corrections. It is shown that the CI or CASSCF corrected CCSD method can effectively account for higher than pair clusters while requiring only a small additional computational effort over that of the standard CCSD approach.
Ab initio configuration interaction determination of the overtone vibrations of methyleneimine in the region 2800–3200 cm−1
Authors: Pouchan Claude , Zaki Khalil
Published: July 2002

Ab initio configuration interaction (CI) potential function calculated from a 6-311G** basis set at a MP2 level of theory is used to compute the vibrational energy levels of methyleneimine CH2NH between 2800 and 3200 cm−1. The most important configurations selected by an iterative process by means of a variational perturbational method are diagonalized. Results show a perfect agreement with the most reliable experimental values and predict the ν5+ν6, ν4+ν6, and ν4+ν5 unobserved combinations.
Comment on “Quantum-mechanical scattering of an atom from a rigid hemisphere on a flat surface” [J. Chem. Phys. 107, 9437 (1997)]
Authors: Lemoine Didier
Published: July 2002

The equivalence between the analytical formulation of Choi, Tang and Toennies [J. Chem. Phys. 107, 9437 (1997)] and that of Heuer and Rice [Z. Phys. B 59, 299 (1985)] for the exact quantum mechanical scattering of an atom from a hard hemisphere on a flat and rigid surface is demonstrated. The earlier and simpler formulation is emphasized as the straightforward application of the underlying symmetry principle ensuring that the proper boundary conditions are satisfied. This relies on expressing the scattering amplitude as the difference of two contributions. These are free hard-sphere scattering amplitudes that are evaluated at two final angles determined by reflection construction.
Comparisons of semiclassical approximations by expansion in Planck’s constant
Authors: Yoshimori Akira
Published: July 2002

Fermi’s golden rule is expanded in Planck’s constant to study quantum effects of nuclear baths on transitions between electronic states. For six approximations, the second-order expansion of the transition rates is compared with the exact expansion. The comparison provides the conditions for agreement between the exact and approximate rate constants in the second order. Two of the conditions show that the change in electronic states of the solute does not affect solvent structure much. The other concerns linearity of the reaction coordinate. Besides the comparison of analytical expressions, the expansion of approximations is numerically compared, using a simple model. Most approximations show similar values for a parameter set. The values approximate the value obtained by quantum molecular simulations.
Microwave spectroscopic detection of a transient phosphorus-bearing molecule, H3PO
Authors: Ahmad Imtiaz K. , Ozeki Hiroyuki , Saito Shuji
Published: July 2002

The microwave spectrum of the transient phosphine oxide, H3PO, was detected in the gas phase for the first time using a source-modulated spectrometer. The H3PO molecule was generated in a free space cell by a dc glow discharge of a mixture of PH3, CO2, and H2 gases and the corresponding spectral lines for each rotational transition of H3PO formed a pattern clearly indicative of a symmetric top molecule. Isotopomers of H3PO, i.e., H3P18O and D3PO were also produced; H3P18O in the same fashion as for H3PO, and D3PO, in a mixture of D2 and CO2 gases passing over red phosphorus grains. In total, 54 spectral lines of H3PO, 55 lines of H3P18O, and 61 lines of D3PO were measured for the fine structure of rotational transitions, J=2–1 to 12–11. The rotational constant, B0, and centrifugal constants, DJ, DJK, and HKJ were ascertained by a least squares analysis of the measured frequencies for each of the species. Using the rotational constants of the three isotopic species, the following r0 structure was determined: r0 (PO)=1.4763 Å, r0(PH)=1.4406 Å, and ∠HPO=114.26°. The value of each structural parameter deviates significantly from the most recent results predicted by ab initio calculations.
Frictional effects in the simulation of polymers pulled around smooth and corrugated posts
Authors: Hunter John E. , Seagraves Caren , Reinhardt William P.
Published: July 2002

This paper reports on a detailed study of solid and solvent frictional forces in Brownian dynamics simulations of a harmonic polymer chain pulled around a circular post in two dimensions. In the case of corrugated posts, a backward-driving normal-force-dependent tangential force arises implicitly, without the explicit inclusion of dissipation into the post, and we interpret this as a particular type of solid friction. Tension distributions in the polymer and velocities are determined in the steady state and compared with model predictions and empirical fits. For smooth posts, the mean field models developed are microscopic and predictive; in the case of corrugated posts they are phenomenological. A detailed study of the effective barrier heights for passage of polymer beads over the corrugation and how those barriers relate to couplings between neighboring beads helps to elucidate the reason for the breakdown of a simple mean field theory in the case of nonzero corrugation amplitude. The importance of the relationship between the corrugation period and the tension-dependent bead spacing is emphasized. Detailed analogies are made with a one-dimensional model of a particle in a tilted periodic potential for which analytic solutions for the steady state velocity can be determined. An Appendix briefly describes how similar results can be obtained using steady state Monte Carlo dynamics.
Deuterium isotope effect in the phase memory time of triplet pyrimidine in benzene
Authors: Chan I. Y. , Dernis M. S.
Published: July 2002

We report a systematic study of the phase memory time (TM) of normal and deuterated pyrimidine in benzene. We have performed both the Hahn (2-pulse) echo and stimulated (3-pulse) echo experiments in zero magnetic field with optical detection. We focus on the increase of TM as the guest and the host molecules are successively deuterated. For a guest/host isotopic identity of H/H, D/H, H/D, and D/D, respectively, the 2-pulse echo TM stands in ratio of 1:1.2:3.0:7.0. This follows the same trend as those in the results of Van’t Hof and Schmidt’s [Mol. Phys. 38, 309 (1979)] earlier work on quinoline/durene. However, our ratios are much smaller. The corresponding ratio of TM for 3-pulse echo is 1:2:2:3. After a careful accounting of the contribution of the triplet decay, we have established the existence of a nondecaying residual 3-pulse echo as predicted by Hu and Hartmann [Phys. Rev. 9, 1 (1974)]. We ascribe the smaller deuteration effect on our 2-pulse echo results to the 3nπ* nature of pyrimidine rather than the 3ππ* nature of quinoline. The small isotope effect on 3-pulse echoes is consistent with a few published reports. A plausible cause for the very slow spin flipping rate extracted from our data is suggested.
Equation of state for fluid mixtures of hard spheres and heteronuclear hard dumbbells
Authors: Barrio C. , Solana J. R.
Published: July 2002

A theoretically founded equation of state is developed for mixtures of hard spheres with heteronuclear hard dumbbells. It is based on a model previously developed for hard-convex-body fluid mixtures, and further extended to fluid mixtures of homonuclear hard dumbbells. The equation scales the excess compressibility factor for an equivalent hard-sphere fluid mixture to obtain that corresponding to the true mixture. The equivalent mixture is one in which the averaged volume of a sphere is the same as the effective molecular volume of a molecule in the real mixture. Thus, the theory requires two parameters, namely the averaged effective molecular volume of the molecules in the mixture and the scaling factor, which is the effective nonsphericity parameter. Expressions to determine these parameters are derived in terms of the geometrical characteristics of the molecules that form the mixture. The overall results are in closer agreement with simulation data than those obtained with other theories developed for these kinds of mixtures.
Density, temperature, and bond-length dependence of dynamic friction on a molecular bond
Authors: Vergeles Maxim , Szamel Grzegorz
Published: July 2002

We apply the theoretical formalism developed by us earlier [M. Vergeles and G. Szamel, J. Chem. Phys. 110, 6827 (1999)] to study density, temperature, and bond-length dependence of the dynamic friction on a molecular bond. We show that the theory reproduces all the trends seen in molecular dynamics (MD) simulations. The theoretical predictions agree reasonably well with the results of MD simulations except for very low densities or very short bond lengths.
Three pulse photon echo studies of nondipolar solvation: Comparison with a viscoelastic model
Authors: Larsen Delmar S. , Ohta Kaoru , Fleming Graham R.
Published: July 2002

Three pulse stimulated photon echo peak shift (3PEPS) measurements were used to probe the solvation of a quadrupolar solute in three room temperature nondipolar solvents; benzene, CCl4, and CS2, and the results were compared with those for two polar solvents, methanol and acetonitrile, and one weakly polar solvent, toluene. Our data reveal three distinct solvent dynamical time scales; a sub-100 fs ultrafast component attributed to inertial motions, a slow (∼2–3 ps) component attributed to structural relaxation, and an intermediate time scale (∼600 fs) of uncertain origin. The six solvents were chosen to reflect a range of possible interactions, but exhibit similar dynamics, suggesting that similar mechanisms may be at work or that different mechanisms may exist, but occur on similar time scales. A viscoelastic continuum solvation model proposed to describe nonpolar solvation [J. Phys. Chem. A 102, 17 (1998)] was used for a preliminary analysis of our data.
Real-space surface crystallography: Experimental stereographic projections from ion scattering
Authors: Bolotin I. L. , Houssiau L. , Rabalais J. W.
Published: July 2002

Scattering and recoiling imaging spectrometry (SARIS) in the blocking configuration is used to obtain experimental two-dimensional stereographic projections of the Ni(110) and Pt(111) surfaces. The development of this technique as an element-specific real-space surface crystallography that is sensitive to interatomic spacings in the surface and subsurface layers of a crystal is described. This projection imaging method is based on the blocking of atomic trajectories scattered from subsurface layers by atoms in layers nearer to the surface. The resulting magnification of the blocking cones, as captured by a gated position-sensitive microchannel plate detector, is ∼109. The images of the blocking patterns provide direct information on interatomic spacings and surface symmetry and structure. Classical ion trajectory simulations using the three-dimensional scattering and recoiling imaging code (SARIC) are used to simulate the stereographic projections and blocking patterns and to provide quantitative interpretations. The method is sensitive to interatomic spacings in the surface and subsurface layers. The physical properties of the blocking process are derived from analysis of the data and a simplified, approximate, two-atom model of the scattering/blocking process is developed.
Mass transport of phosphoric acid in water: A H1 and P31 pulsed gradient spin-echo nuclear magnetic resonance study
Authors: Chung S. H. , Bajue S. , Greenbaum S. G.
Published: July 2002

Aqueous solutions of phosphoric acid (H3PO4) of varying concentrations have ionic conductivities as high as 0.25 Scm−1 at ambient temperatures which cannot be accounted for on the basis of regular hydrodynamic movement of mobile ions. We report careful measurements of self-diffusion coefficients (D) of mobile species for the 85 wt% (14.6 M) phosphoric acid solution over a range of temperature from 293 to 353 K, using H1 (I=1/2) and P31 (I=1/2) pulsed gradient Hahn spin-echo (PGSE) techniques. The experimental D values are interpreted together with previously published viscosity (η) and conductivity (σ) data. The data show that protons diffuse faster than the phosphorus carrying species. The diffusion data for both nuclear species are found to be linear on an Arrhenius plot with activation energies of 25 and 36 kJ mol−1 for H1 and P31 species, respectively. Analysis on the basis of the Nernst–Einstein relation yields a proton transference number of t≈0.99 and a proton charge carrier number density of n≈1.6×1028 m−3. A plot of the product Dη as a function of temperature suggests that the proton and phosphorus species undergo significantly different mass transport mechanisms. In particular the P31 data show a nonlinear increase in Dη with temperature, while the H1 data exhibit a decrease in Dη with increasing temperature which is not expected for hydrodynamically simple fluids. The latter behavior is attributed to the water mediated transfer of protons between the phosphate groups. Room temperature P31 diffusion coefficients of condensed phosphates are also reported, and as expected the diffusion coefficient is dependent on the size of the moving species.
Chemistry of NO2 on CeO2 and MgO: Experimental and theoretical studies on the formation of NO3
Authors: Rodriguez José A. , Jirsak Tomas , Sambasivan Sharadha , Fischer Daniel , Maiti Amitesh
Published: July 2002

In environmental catalysis the destruction or removal of nitrogen oxides (DeNOx process) is receiving a lot of attention. Synchrotron-based x-ray absorption near-edge spectroscopy, high-resolution photoemission, and first-principles density-functional calculations (DFT-GGA) were used to study the interaction of nitrogen dioxide with CeO2 and MgO. The only product of the reaction of NO2 with pure CeO2 at 300 K is adsorbed nitrate. The NO3 is a thermally stable species which mostly decomposes at temperatures between 450 and 600 K. For the adsorption of NO2 on partially reduced ceria (CeO2−x), there is full decomposition of the adsorbate and a mixture of N, NO, and NO3 coexists on the surface of the oxide at room temperature. Ce3+ cations can assist in the transformation of NO and NO2 in DeNOx operations. Adsorbed NO3 (main product) and NO2 are detected after exposing MgO to NO2 gas. A partial NO2,ads→NO3,ads transformation is observed on MgO(100) from 150 to 300 K. DFT-GGA calculations show strong bonding interactions for NO2 on Mg sites of this surface, and dicoordination via O, O is more favorable energetically than monocoordination via N. The NO2,ads species disappears from magnesium oxide at temperatures below 600 K, whereas part of the NO3,ads is stable up to temperatures near 800 K. MgO can be very useful as a sorbent for trapping NO2. A general trend is found after comparing the chemical behavior of NO2 on different types of oxides (CeO2, MgO, TiO2, Fe2O3, CuO, ZnO). On all these systems, the main product after adsorbing NO2 at 300 K is nitrate with minor amounts of chemisorbed NO2 and no signs of full decomposition of the adsorbate. This trend and the results of DFT-GGA calculations indicate that NO2 is very efficient for the nitration (i.e., formation of NO3 as a ligand) of metal centers that are missing O neighbors in oxide surfaces.
Ab initio potential energy surface for the reactions between H2O and H
Authors: Bettens Ryan P. A. , Collins Michael A. , Jordan Meredith J. T. , Zhang Dong H.
Published: July 2002

Interpolated ab initio potential energy surfaces which describe abstraction and exchange reactions in collisions of hydrogen and water are reported. The electronic structure calculations are performed at the QCISD(T) level of theory, with an additivity approximation. A sufficiently large basis set is required to describe the Rydberg character of the electronic state for molecular configurations which are important for the exchange process. Classical and quantum dynamics calculations on the surfaces are presented.
Linear stability of symplectic maps
Authors: Howard J. E. , MacKay R. S.
Published: July 2002

A general method is presented for analytically calculating linear stability limits for symplectic maps of arbitrary dimension in terms of the coefficients of the characteristic polynomial and the Krein signatures. Explicit results are given for dimensions 4, 6, and 8. The codimension and unfolding are calculated for all cases having a double eigenvalue on the unit circle. The results are applicable to many physical problems, including the restricted three-body problem and orbital stability in particle accelerators.
Multiparameter solutions of Yang–Baxter equation from braid group representations
Authors: Li You-Quan
Published: July 2002

On the basis of weight conservation of the An case, Yang–Baxter relations are solved without the assumption that the upper-left triangle of each sub-block of S matrix vanishes. A family of braid group representations having no transpose symmetry are obtained and shown to construct link polynomials. Finally, a sequence of solutions of the Yang–Baxter equation with multiparameters are obtained via the Yang-Baxterization procedure.
Quasi-invariant Lagrangians on Lie groups and the method of coadjoint orbits
Authors: Inamoto Tadashi
Published: July 2002

Starting with a two-cocycle globally defined on a Lie group G, the Lagrangian system on G is constructed whose Lagrangian is quasi-invariant under a right translation canonically lifted to the tangent bundle TG. A direct consequence of the quasi-invariance is the appearance of central extensions in the Noether-symmetry algebra. Then, it is shown that the kinematical sector of such a model realizes, through a symplectic reduction, the Kirillov–Kostant symplectic structure on the coadjoint orbit of the Lie group with the central extensions. The generalization to a ‘‘higher-dimensional’’ theory of the Wess–Zumino–Witten-type is also discussed herein.
On Abelianization of first class constraints
Authors: Gogilidze S. A. , Khvedelidze A. M. , Pervushin V. N.
Published: July 2002

A systematic method for the conversion of first class constraints to an equivalent set of the Abelian constraints based on the Dirac equivalence transformation is developed. A representation for the corresponding matrix of this transformation is proposed. This representation allows one to reduce the problem of Abelianization to the solution of a certain system of first order linear differential equations for matrix elements.
Obstructions to pin structures on Kleinian manifolds
Authors: Alty L. J. , Chamblin A.
Published: July 2002

We develop various topological notions on four-manifolds of Kleinian signature (−−++). In particular, we extend the concept of ‘‘Kleinian metric homotopy’’ to nonorientable manifolds. We then derive the topological obstructions to pin-Klein cobordism for all of the pin groups. Finally, we discuss various examples and applications which arise from this work.
Integrability of the quantum adiabatic evolution and geometric phases
Authors: Cassinelli G. , De Vito E. , Levrero A.
Published: July 2002

We show that the cyclic adiabatic evolution of a quantum system is completely integrable as a classical Hamiltonian system. In this context the Berry phases arise naturally as cohomology of the invariant tori.
The ∂̄-dressing method and the solutions with constant asymptotic values at infinity of DS-II equation
Authors: Dubrovsky V. G.
Published: July 2002

Several classes of exact solutions with constant asymptotic values at infinity of DS-II equation are constructed via the ∂¯-dressing method. Among these solutions are the solutions with functional parameters, multi-line solitons and breathers, and pure rational solutions.
Hypergeometric integrals arising in atomic collisions physics
Authors: Colavecchia F. D. , Gasaneo G. , Garibotti C. R.
Published: July 2002

We introduce a method of obtaining volume integrals involving confluent hypergeometric functions. This method is based on the integral representation of these functions and enabled us to write a generalized Nordsieck integral in terms of hypergeometric functions of many variables. We explore some particular results that could be useful when calculating transition matrices in collision theories.
S
4
symmetry of 6j symbols and Frobenius–Schur indicators in rigid monoidal C* categories
Authors: Fuchs J. , Ganchev A. Ch. , Szlachányi K. , Vecsernyés P.
Published: July 2002

We show that a left-rigid monoidal C* category with irreducible monoidal unit is also a sovereign and spherical category. Defining a Frobenius–Schur-type indicator we obtain selection rules for the fusion coefficients of irreducible objects. As a main result we prove S4 invariance of 6j symbols in such a category.
Two-dimensional electron gas in a magnetic field and point potentials
Authors: Gredeskul S. , Avishai Y. , Azbel’ M. Ya.
Published: July 2002

This paper presents a brief review of the electron properties in two-dimensional systems which contain zero-range scatterers which are subjected to a magnetic field. The electron spectrum is described for a periodic arrangement of point scatterers and rational magnetic flux per unit cell. Delocalized states on the Landau levels are constructed for the case of positional disorder. The electron localization in a one-dimensional disordered set of scatterers is studied. Application to the study of electron transmission through quantum dots and ballistic channels is reviewed.
The smoothing of the surface structure in solids under irradiation
Authors: Slezov V. V. , Apalkov V. M. , Boı̆ko Yu. I. , Carstanjen H. D.
Published: July 2002

The general system of equations describing the smoothing of surface structure in solids under irradiation is formulated. It is shown that under real conditions the system can be reduced to a simpler form which has an exact solution. A general formula describing the smoothing of surface structure with time is derived. As a special case, this formula gives the evolution (smoothing) of the relief in the absence of radiation, which is associated with the difference in curvatures for different roughnesses. The physical reason behind the intensification of smoothing under irradiation is the difference between the positions of the centers of gravities for concentration profiles of vacancies and interstitials. The radiation gives rise to a new type of dependence of the rate of smoothing on the roughness parameters of the surface, which permits the experimental separation of the contribution from radiation to smoothing and simultaneously makes it possible to determine some parameters which are difficult to measure.
Residual low-temperature resistivity and peculiarities of infrared absorption of YBa2Cu3O6+x superconductor as manifestations of the long-distance potential relief
Authors: Eremenko V. V. , Kachur I. S. , Piryatinskaya V. G. , Ratner A. M. , Shapiro V. V.
Published: July 2002

Various physical phenomena connected with long-distance potential relief created by negative oxygen impurity ions in a conducting plane are considered. The long-distance potential generates a secondary electron structure responsible for these phenomena. The relation between the residual low-temperature resistivity and the secondary structure is established experimentally. The high sensitivity of the residual resistivity to photoillumination, modifying the long-distance potential, and its increase with decreasing temperature suggest the low-temperature localization of holes in long-distance potential wells. Optical transitions between energy levels of the secondary structure differing from other optical transitions in a much higher probability and a high sensitivity to the shape of the long-distance potential well are analyzed. The results of analysis are in qualitative agreement with the available data on optical absorption spectra.
The effect of pressure and silver impurity on the superconducting properties of the HTS YBa2Cu4O8
Authors: Kleı̆ner V. Z. , Ovcharenko O. N. , San’kov A. A. , Tereshina N. S. , Finkel’ V. A.
Published: July 2002

The effect of uniform compression is studied on the superconducting transition temperature of the HTS ceramics YBa2(Cu1−xAgx)4O8±δ(x=0, 0.05, 0.1, 0.15). It is shown that the pressure effect in these compounds differs considerably from that in the system YBa2(Cu1−xAgx)3O7−δ. The observed peculiarities are discussed on the basis of the van Hove anomaly in the electron energy spectrum of oxide cuprates. The correspondence of the superconducting properties of the 1–2–4 and 1–2–3 systems under pressure with certain models of high-temperature superconductivity is discussed. The nature of nonlinearity of the temperature dependence of the electrical resistance of the 1–2–4 system in the normal state and the effect of substitution of silver for copper on it are studied. The corresponding phase diagram is constructed. The correspondence of the observed increase in crossover temperature with the Nagaoza–Lee theory is discussed.
Surface energy relaxation of conduction electrons in bismuth using transverse electron focusing technique
Authors: Andrievskii V. V. , Komnik Yu. F. , Rozhok S. V.
Published: July 2002

The position of the first and second lines of transverse electron focusing on the scale of magnetic fields is analyzed to determine the loss of excess energy of conduction electrons in bismuth as a result of collisions with the crystal boundary upon normal incidence as well as the shape of the functional dependence of this quantity on the initial excess energy. It is found that beginning from relatively low values of excess energy (∼3 meV), a sharp drop in energy occurs upon reflection of electrons at the boundary.
Peculiarities of domain walls with vertical Bloch lines at low temperatures
Authors: Dovgij V. T. , Kalkin A. A. , Astaf’eva T. G. , Bar’yakhtar F. G. , Yampolskaya G. I.
Published: July 2002

The results of experimental studies of the vertical Bloch line (VBL) generation and stability in the epitaxial iron-garnet films (EIGF) with different compounds, anisotropy, implantation, and compensation temperatures are presented. It is shown that the critical fields of the VBL generation and annihilation in the stripe domain (SD) walls increase and that its values differ considerably (the VBL stability region increases) with decreasing temperature. The domain period increases as a result of magnetic inhomogeneities of the domain walls. The magnetic profile and the energy potential barrier account for the existence of the metastable domain structures with different periods. It is established that the VBL existence domains are limited by the region near the Néel temperature TN and the compensation point temperature Tc (in films with Tc).
Exchange metamagnetism in systems with triangular structure
Authors: Zavorotnev Yu. D. , Medvedeva L. I.
Published: July 2002

The splitting of magnetization jumps in the metamagnetic phase of compounds based on iron phosphide in a magnetic field is obtained as a result of analysis of two models with the Landau potential with different degrees of complexity. The conditions for realization of transitions between the paramagnetic, metamagnetic, and ferromagnetic phases are established.
Exchange and spin relaxation in solid He3
Authors: Cowan B. , Fardis M.
Published: July 2002

Spin relaxation measurements in solid He3 in the temperature region where exchange dominates the behavior are reviewed and reanalyzed. A model which brings together the complex exchange modulation of the dipolar interaction into a single correlation time is adopted. This may be regarded as introducing an effective pairwise exchange Hamiltonian. On the basis of this model new procedures are proposed for obtaining mathematical expressions for the dipolar autocorrelation function and the spectral density functions, which determine the relaxation times. By the appropriate treatment of short-time and long-time asymptotic behavior, together with a method for taking into account the mid-range behavior, it is possible to fit the experimental data extremely well. The success of this procedure seems surprising in the light of multiple spin exchange in solid He3. It is an indication that the dominant exchange processes scale with density in a similar way. This conclusion is supported by path-integral Monte Carlo calculations. Some consequences and implications of this conclusion are discussed.
Possibility of ripplon-induced weak localization
Authors: Dahm A. J.
Published: July 2002

Ripplon-induced weak localization is proposed for electrons on a liquid-helium surface. Ripplon scattering is quasi-elastic, the ripplons are quasi-static relative to the electron velocity, and the relative change in occupation number of the ripplon state in a scattering event is small. Conditions for the observation of ripplon-induced weak localization are calculated.
Peculiarities of resistive properties of layered superconductors in a magnetic field
Authors: Grishin A. M. , Medvedev Yu. V. , Rao K. B.
Published: July 2002

The peculiarities of electrodynamics of layered HTS materials in a longitudinal magnetic field, which are associated with fluctuations of the shape of an Abrikosov vortex formed by a set of weakly coupled 2d-vortices centered in equilibrium in superconducting planes, are studied. The value of the longitudinal critical current of the layered media is estimated, and its temperature dependence is determined.
Manifestations of non-Heisenberg interactions in the temperature dependence of the NMR frequency of a NiCl2 crystal
Authors: Kalita V. M. , Lozenko A. F.
Published: July 2002

A thermodynamic analysis of the influence of non-Heisenberg interionic spin-spin interactions on the temperature dependence of the NMR frequency of a NiCl2 crystal is carried out.
Quantum magnetotransport in a highly correlated two-dimensional electron liquid on a superfluid helium surface
Authors: Monarkha Yu. P. , Shirahama K. , Kono K.
Published: July 2002

The theoretical concept of the inelastic quantum magnetotransport of highly correlated surface electrons on superfluid helium is presented. The low-temperature magnetoconductivity data are obtained from the damping of the edge magnetoplasmons. It is shown that the temperature and magnetic field dependences of the magnetoconductivity can be perfectly described by the inelastic many-electron theory as the interplay of two kinds of Landau level broadening produced by scatterers and by mutual Coulomb interaction.
Peculiarities in the effect of hydrogen on CDW transition in NbSe3
Authors: Chashka Kh. B. , Bychko V. A. , Obolenskii M. A. , Hasan Raid , Beletskii V. I. , Basteev A. V. , Prognimak A. N.
Published: July 2002

The influence of intercalated hydrogen concentration on the physical properties of NbSe3 is investigated. The mass-spectrometric analysis reveals a nonlinear dependence of hydrogen extraction from the crystal structure on the saturated pressure. Resistive measurements make it possible to study the concentration dependence of the temperature TCDW corresponding to a phase transition accompanied with the formation of a charge density wave (CDW) and temperature dependence of CDW pinning threshold fields. A metal-semiconductor phase transition is observed for certain concentrations of intercalated hydrogen. All the measurements are made in the temperature range of the first CDW transition (90–300 K).
Molecular adsorption states and sticking probability of D2 molecules on the W(110) surface at liquid helium temperatures
Authors: Osovskii V. D. , Ptushinskii Yu. G. , Sukretnyi V. G. , Chuikov B. A.
Published: July 2002

The dependence of the sticking probability of D2 molecules on the W(110) surface of tungsten on the degree of coverage S(θ) at the substrate temperature Ts∼5 K is measured under different conditions of adlayer formation.The effect of significant increase in the sticking probability for D2 in the course of population of weakly bound absorption states observed earlier (V. D. Osovskii et al., Pis’ma Zh. Éksp. Teor. Phys. 60, 569 (1994) [JETP Lett. 60, 586 (1994)]) increases considerably on the surface precovered with an ordered monolayer of deuterium atoms and even more strongly for a surface covered with atomic and physisorbed molecular monolayers. The peculiarities in the S(θ) dependence observed at Ts∼5 K are explained, taking into account the island mechanism of adlayer growth as well as the precursor mediated process of its formation. The S(θ) dependences are also obtained for Ts=78 and 300 K and indicate the Langmuir mechanism of adsorption during the population of the 550 K atomic state as well as the precursor mediated mechanism of formation of the 410 K atomic state.
Small-amplitude oscillations of magnetization accompanying long-lived spin-precession in He3-B
Authors: Kharadze G. A. , Suramlishvili N. G. , Vachnadze G. E.
Published: July 2002

Frequency spectrum of small-amplitude oscillations of magnetization against the background of coherently precessing (phase-correlated) spin modes in superfluid He3 placed in a strong magnetic field depends on the magnitude of spin polarization S and spin-orbit structure of dynamical ordered states. Spectrum of these oscillations is calculated for unconventional precessing modes in He3-B characterized by S=S0/2, where S0 is the value of S at equilibrium.
Nonlinear stationary profile waves in spatially disordered magnetic media
Authors: Ivanchenko E. A.
Published: July 2002

A nonlinear evolution system of hydrodynamic-type equations describing a three-dimensional multisublattice magnet is investigated. Explicit form of the energy density function for magnetic systems that have an invariant energy density relative to right and left spin rotations is obtained. For quadratic-biquadratic dependence of the energy density (in terms of Cartan’s invariant functions), exact solutions are obtained in the one-dimensional case for spin density in the form of stationary profile waves. Solutions for magnon fields that induce such waves are also obtained.
Magnetic and galvanomagnetic properties of the ordering Pd2AuFe alloys
Authors: Kourov N. I. , Tyulenev L. N. , Mydlars T.
Published: July 2002

Magnetic and galvanomagnetic properties of ordering alloys Pd2AuFe are studied in fields H⩽12 MA/m at T=4.2 K. It is shown that the disappearance of spontaneous magnetization in the region of ferromagnetic–antiferromagnetic phase transition which occurs as a result of atomic ordering of the Pd2AuFe alloys is accompanied by peaks of paraprocess susceptibility and of the anomalous positive Hall effect. The sign of the normal Hall effect is reversed in this case. It is shown that the peculiarities of galvanomagnetic properties are associated with the rearrangement of the electronic band structure during ordering of the alloys.
Neutron scattering and diffusive x-ray diffraction in acoustic modes in Nd2CuO4
Authors: Fil D. V. , Zazunov A. L.
Published: July 2002

The differential cross section of thermal neutron scattering and x-ray scattering by acoustic excitations are calculated in the framework of an anisotropic elastic medium model with an additional two-dimensional acoustic-type mode which interacts with elastic deformation. This model was proposed earlier for describing the anomalous behavior of sound velocities in Nd2CuO4. The influence of plane mode on the angular dependence of neutron scattering and on the shape of diffusive spot in x-ray diffraction pattern is studied.
Activation spin waves in the Landau theory of Fermi liquid
Authors: Akhiezer A. I. , Laskin N. V. , Peletminskii S. V.
Published: July 2002

The activation spectra of collective oscillations with a quadratic energy–momentum relation are studied for magnetically ordered Fermi liquid. It is shown that the spectrum of activation spin waves depends considerably on the structure of the Landau interaction amplitude as a function of the angle between quasimomenta of fermions. The existence of activation spin waves is manifested in neutron and light scattering processes as well as in the transformation of waves in magnetically ordered media.
Influence of cyclic change of normal and superconducting states on the deformation of Pb–In alloys
Authors: Lebedev V. P. , Krylovskii V. S. , Simoes V. M. Pinto
Published: July 2002

The effect of cyclic change of the normal and superconducting states of single crystals of Pb–In alloys is manifested in the form of strain hardening. The increase in the deforming stress in this case is attributed to an increase in the density of structural defects.
Localized two-dimensional inhomogeneous states in elastic nematics
Authors: Bogdanov A. N. , Shestakov A. A.
Published: July 2002

Analytic solutions of elasticity equations describing a system of localized axisymmetric inhomogeneous states (“isolated threads”) are obtained for nematic liquid crystals. Such structures are compressed into dense threads under the influence of magnetic or electric fields. It is assumed that such structures may be realized in thread-like nematic textures. This model serves as an alternative to the conventional disclination model. The localized states are found to be radially unstable in cholesterics. However, the existence of lattices with thread-like structures cannot be ruled out.
Magnetic properties of Ba1−xKxBiO3+y single crystals near Tc
Authors: Barilo S. N. , Gatalskaya V. I. , Shiryaev S. V. , Baran M. , Szymczak H. , Szymczak R.
Published: July 2002

Reversible magnetization and hysteresis loops of electrochemically grownBa1−xKxBiO3+y single crystals (x=0.34,0.37) are studied in the vicinity of Tc. The results of measurements of reversible magnetizations are used to construct the temperature dependences of the magnetic penetration depth λ and the critical field Hc2. The λ(T) dependences are described by the BCS theory more successfully than by the two-fluid model. The peak effect observed in these isotropic superconductors on magnetic hysteresis loops is associated with the presence of superstoichiometric oxygen regions. The behavior of the irreversibility line Hirr(T) for both single crystals is approximated successfully by the flux creep model.
Magnetoplasma waves in inversion layers with local electron states
Authors: Gleizer N. V. , Ermolaev A. M. , Haghighi Babak
Published: July 2002

The spectrum and damping factor of plasma and magnetoplasma waves in a two-dimensional electron gas at low temperatures are calculated, taking into account local electron states at impurity atoms. It is shown that localization of electrons decreases the frequency of long-wave plasmons and rearranges the magnetoplasma spectrum in the vicinity of resonant frequencies of electron transitions between the Landau levels and local levels. As a result, the plasma absorption peak is displaced towards low frequencies, and the magnetoplasma peak splits. The characteristics of plasmons and magnetoplasmons are calculated for parameters of the inversion layer at the boundary between silicon and silicon dioxide.
On Hamiltonian formulation of hydrodynamic equations for superfluid He3–A
Authors: Isayev A. A. , Peletminsky S. V.
Published: July 2002

The Poisson brackets for the dynamic variables describing the spin and orbital dynamics of superfluid He3–A are obtained by using a consistent Hamiltonian formalism. The analysis is based on the derivation of the kinematic component of the system Lagrangian and on the consideration of variations of dynamic variables, which leave the kinematic component of the Lagrangian invariant. Equations of motion for the dynamic variables are derived, and Galilean invariance of the obtained equations is considered by proceeding from the invariance of the system Lagrangian to Galilean transformations.
Hyperfine-interaction-driven Aharonov–Bohm effect in mesoscopic rings
Authors: Vagner I. D. , Rozhavsky A. S. , Wyder P.
Published: July 2002

It is shown qualitatively that lifting of the electron spin degeneracy by a hyperfine field, which is generated by a nonequilibrium nuclear spin distribution, and breaking of the left-right symmetry by the spin-orbit interaction in a closed ring produces under certain conditions a persistent current, which demonstrates the Aharonov–Bohm-like oscillations with time in GaAs/AlGaAs-based mesoscopic rings even in the absence of an external magnetic field. The typical time interval of these (meso-nucleospinic) oscillations is of the order of several seconds, which is typical of the nuclear spin relaxation times in heterojunctions.
Mössbauer detection of photoinduced effects in HTSC YBa2(Cu1−x57Fex)3O6+δ
Authors: Eremenko V. V. , Lukashev D. V. , Ponomarchuk V. L.
Published: July 2002

Photoinduced changes of the effective magnetic field on Fe57 nuclei at the Cu(2) site are detected by the Mössbauer technique in YBa2(Cu0.9257Fe0.08)3O6.3. The effect is found to be reversible for several hours in the temperature range 100–300 K.
Internal friction peak in CsI single crystal at liquid helium temperatures
Authors: Smirnov S. N. , Natsik V. D. , Pal’-Val’ P. P.
Published: July 2002

Acoustic relaxation in undeformed and plastically deformed CsI single crystals is studied using the composite oscillator technique at frequencies (1–7)×105 Hz in the temperature range 2–15 K. Plastic deformation leads to the emergence of an internal friction peak localized in the temperature range 4–5 K. It is shown that the peak is shifted towards higher temperatures upon an increase of the vibrational frequency and corresponds to a thermally activated relaxation process with very low values of activation energy U≈1.9×10−3 eV and the attack frequency ν0≈6.7×108 s−1. The interaction of sound with dislocation kinks migrating in the second-order Peierls relief is considered as a possible mechanism of peak formation.
The types of acoustic excitations in two-condensate relativistic superfluid systems
Authors: Vilchinsky S. I. , Fomin P. I.
Published: July 2002

The equations describing the propagation of acoustic waves in relativistic superfluid two-condensate systems are derived and solved. It is shown that the presence of an additional acoustic mode and two types of waves of fourth sound is a peculiarity of the system under investigation.
Second-order nuclear magnetic relaxation in samples with two-level tunneling systems
Authors: Zakharov L. Zh. , Chotorlishvili L. L. , Tugushi A. I.
Published: July 2002

Second-order nuclear magnetic relaxation associated with electric quadrupole interaction between paramagnetic centers and two-level systems is studied. First- and second-order relaxation times are compared. It is shown that second-order relaxation prevails in relatively low magnetic fields.
Hydrodynamic impulse and energy of vortex tangle in superfluid turbulent He-II
Authors: Nemirovskii S. K. , Lushnikov V. A.
Published: July 2002

The average hydrodynamic impulse (or Lamb impulse) JV in the counterflowing, superfluid, turbulent He-II and the kinetic energy E, which is associated with the chaotic vortex filaments, are calculated. These quantities are defined as averages of the classical quantities taken over the stochastic vortex loop distribution. The averaging procedure was performed by using the Gaussian model of the chaotic vortex tangle elaborated earlier. Calculations show that the quantity JV has only a component in the direction of external counterflow velocity (created, e.g., by a heater). As for the energy, it is shown that besides the usual local contribution, the quantity E includes additional terms due to a long-range interaction. Some dynamic properties of the turbulent He-II due to the impulse and energy of the vortex configuration, such as suppression of the superfluid density and decrease in the velocity of the second sound that propagates in the superfluid turbulent He-II, are discussed.