bluuebunny/crossref_metadata_2025 huggingface dataset:
Ectomycorrhizal colonization and richness of previously colonized, containerized Picea engelmannii does not vary across clearcuts when planted in mechanically site-prepared mounds
Authors: Jones Melanie D , Hagerman Shannon M , Gillespie M
Published: October 2002

The Sicamous Creek silviculture systems trial, which is located at a subalpine forest, comprises five replicated treatments. One-third of the timber volume was removed from 30-ha treatment units using cutblocks of 0.1, 1.0, or 10 ha or single-tree selection. Openings were mechanically site prepared by mounding and planted with nursery-grown containerized Picea engelmannii Parry ex Engelm. seedlings. Seedlings were planted in mineral soil exposed by mounding in all four of the harvested treatments as well as in undisturbed soil in the uncut control treatment. Neither the overall ectomycorrhiza colonization nor the number of ectomycorrhizal morphotypes per seedling varied across the cutblocks or among cutblocks of different sizes. This is in contrast to earlier studies at this site that showed inoculum levels to be significantly higher at 2 m from the forest edge, within the rooting zone of forest trees. We hypothesize that the difference here is due either to (i) competition between native ectomycorrhizal fungi and the ectomycorrhizal fungi present on the spruce at planting or (ii) more homogeneous levels of inoculum in the mineral soil exposed by mounding. Fewer native fungi colonized these seedlings than the nonmycorrhizal seedlings from earlier studies, which had been planted between the mounds.
Peatland pines as climate indicators? A regional comparison of the climatic influence on Scots pine growth in Sweden
Authors: Linderholm Hans W , Moberg Anders , Grudd Håkan
Published: October 2002

Six tree-ring chronologies from Sweden were analyzed to assess if Scots pine (Pinus sylvestris L.) growing on peatlands are useful as annually resolved climate indicators. Also, climategrowth relationships were compared with those of pines growing on nearby dry sites to evaluate if pines from both environments may be combined to yield climate information. While temperatures in spring and summer had positive influences on peatland pine growth, precipitation responses ranged from negative in the north to positive in the south. Climate  growth response patterns differed between peatland and neighboring dry sites, where climatic information in peatland pines was weaker. Added to the direct effect of growth-year climate, is the response of peatland pines to water table variations, a function of climate over several years, likely causing annual growth to reflect a synthesis of climate over a long period. Scots pine climate  growth responses, in both environments, changed throughout the 20th century, corresponding to changes in temperature and precipitation patterns in Sweden. Decreasing growth trends since the late 1970s may be a result of late 20th century change to a warmer and wetter climate, possibly related to a strengthening of the North Atlantic Oscillation (NAO) in recent decades.
SIMULATION OF UNSTEADY INCOMPRESSIBLE FLOWS BY USING TAYLOR SERIES EXPANSION- AND LEAST SQUARE-BASED LATTICE BOLTZMANN METHOD
Authors: CHEW Y. T. , SHU C. , NIU X. D.
Published: October 2002

In this work, an explicit Taylor series expansion- and least square-based lattice Boltzmann method (LBM) is used to simulate two-dimensional unsteady incompressible viscous flows. The new method is based on the standard LBM with introduction of the Taylor series expansion and the least squares approach. The final equation is an explicit form and essentially has no limitation on mesh structure and lattice model. Since the Taylor series expansion is only applied in the spatial direction, the time accuracy of the new method is kept the same as the standard LBM, which seems to benefit for unsteady flow simulation. To validate the new method, two test problems, that is, the vortex shedding behind a circular cylinder at low Reynolds numbers and the oscillating flow in a lid driven cavity, were considered in this work. Numerical results obtained by the new method agree very well with available data in the literature.
JORDAN–SCHWINGER-TYPE REALIZATIONS OF THREE-DIMENSIONAL POLYNOMIAL ALGEBRAS
Authors: SUNIL KUMAR V. , BAMBAH B. A. , JAGANNATHAN R.
Published: October 2002

A three-dimensional polynomial algebra of order m is defined by the commutation relations [P0,P±] = ± P±, [P+,P-] = ϕ(m)(P0) where ϕ(m) (P0) is an m th order polynomial in P0 with the coefficients being constants or central elements of the algebra. It is shown that two given mutually commuting polynomial algebras of orders l and m can be combined to give two distinct (l+m+1)th order polynomial algebras. This procedure follows from a generalization of the well-known Jordan–Schwinger method of construction of su(2) and su(1,1) algebras from two mutually commuting boson algebras.
THE CP-VIOLATING ASYMMETRY IN η → π+ π-e+e-
Authors: GAO DAO-NENG
Published: October 2002

We study the CP-violating asymmetry [Formula: see text], which arises, in η → π+π-e+e-, from the angular correlation of the e+e- and π+ π- planes due to the interference between the magnetic and electric decay amplitudes. With the phenomenologically determined magnetic amplitude and branching ratio as input, the asymmetry, induced by the electric bremsstrahlung amplitude through the CP-violating decay η → π+π-, and by an unconventional tensor type operator, has been estimated respectively. The upper bound of [Formula: see text] from the former is about 10-3, and the asymmetry from the latter might be up to O(10-2). One can therefore expect that this CP asymmetry would be an interesting CP-violating observable for the future precise measurements in the η factories.
CP VIOLATION AND MODULI STABILIZATION IN HETEROTIC MODELS
Authors: GIEDT JOEL
Published: October 2002

The role of moduli stabilization in predictions for CP violation is examined in the context of four-dimensional effective supergravity models obtained from the weakly coupled heterotic string. We point out that while stabilization of compactification moduli has been studied extensively, the determination of background values for other scalars by dynamical means has not been subjected to the same degree of scrutiny. These other complex scalars are important potential sources of CP violation and we show in a simple model how their background values (including complex phases) may be determined from the minimization of the supergravity scalar potential, subject to the constraint of vanishing cosmological constant.
WHAT DID WE LEARN FROM STUDYING ACOUSTIC BLACK HOLES?
Authors: PARENTANI RENAUD
Published: October 2002

The study of acoustic black holes has been undertaken to provide new insights about the role of high frequencies in black hole evaporation. Because of the infinite gravitational redshift from the event horizon, Hawking quanta emerge from configurations which possessed ultra high (trans-Planckian) frequencies. Therefore Hawking radiation cannot be derived within the framework of a low energy effective theory; and in all derivations there are some assumptions concerning Planck scale physics. The analogy with condensed matter physics was thus introduced to see if the asymptotic properties of the Hawking phonons emitted by an acoustic black hole, namely stationarity and thermality, are sensitive to the high frequency physics which stems from the granular character of matter and which is governed by a non-linear dispersion relation. In 1995 Unruh showed that they are not sensitive in this respect, in spite of the fact that phonon propagation near the (acoustic) horizon drastically differs from that of photons. In 2000 the same analogy was used to establish the robustness of the spectrum of primordial density fluctuations in inflationary models. This analogy is currently stimulating research for experimenting Hawking radiation. Finally it could also be a useful guide for going beyond the semi-classical description of black hole evaporation.
2D BLACK HOLES AND DIMENSIONAL REDUCTION
Authors: BALBINOT R. , FABBRI A.
Published: October 2002

The use of lower-dimensional models is exploited in many areas of physics as a way to simplify the mathematical treatment of very complicated phenomena while, at the same time, retaining the main physical ingredients. For the case of black holes, the Hawking evaporation process1 can be understood using a simple model where the gravity action is coupled to quantized matter in the form of free two-dimensional minimal scalar fields. In particular, the effective action one derives by straightforward integration of the trace anomaly2 gives a stress energy tensor which in the Schwarzschild spacetime perfectly agrees with the results one gets by standard canonical quantization. Trying to improve the model, i.e. by employing a spherically reduced 4d minimal scalar field3, one faces a number of difficulties. Unphysical results obtained for the evaporation of black holes (such as antievaporation3,4) using the anomaly induced effective action led us to perform a rigorous calculation of the quantum stress tensor in Schwarzschild by using the point-splitting regularization technique5: exact asymptotic results close to the horizon and at infinity have been derived in the three quantum states of interest (namely Boulware, Hartle-Hawking and Unruh) and two analytic approximations proposed , one valid for large r (based on the WKB) and the other being physically meaningful in the region close to the horizon. Finally, based on these results a "phenomenological" modification of the (unsatisfactory) anomaly induced effective action has been carried out6.
NEW SELF-DUAL EINSTEIN METRICS
Authors: CASTEILL P. Y. , VALENT G.
Published: October 2002

A new family of euclidean Einstein metrics with self-dual Weyl tensor have been obtained using ideas from extended supersymmetries1,2. The basic supersymmetric formalism3, known as harmonic superspace, was adapted to the computation of self-dual Einstein metrics in 4. The resulting metric depends on 4 parameters besides the Einstein constant and has for isometry group U(1) × U(1), with hypersurface generating Killing vectors. In the limit of vanishing Einstein constant we recover a family of hyperkähler metrics within the Multicentre family 5 (in fact the most general one with two centres). Our results include the metrics of Plebanski and Demianski6 when these ones are restricted to be self-dual Weyl. From Flaherty's equivalence 7 these metrics can also be interpreted as a solution of the coupled Einstein-Maxwell field equations, for which we have given the Maxwell field strength forms2.
WORLD-LINE DEVIATIONS AND EPICYCLES
Authors: VAN HOLTEN J. W.
Published: October 2002

In general relativity, only relative acceleration has an observer-independent meaning: curvature and non-gravitational forces determine the rate at which world lines of test bodies diverge or converge. We derive the equations governing this effect not only in the well-known case of point masses, but also for test bodies with charge and/or spin. The application of our method to the motion of particles in a central field results in an elegant, fully relativistic version of the Ptolemaean epicycle scheme.
ON THE DERIVATION OF THE EQUATIONS OF MOTION
Authors: KANIEL S. , ITIN Y.
Published: October 2002

General Relativity is unique, among the class of field theories, in the treatment of the equations of motion. The equations of motion of massive particles are completely determined by the field equation 1-5. Einstein's field equations, as well as most field equations in gravity theory, have a specific analytical form: They are linear in the second order derivatives and quadratic in the first order, with coefficients that depend on the variables.

We propose for the N-body problem of equations that are Lorentz invariant a novel algorithm for the derivation of the equations of motion from the field equations. It is:

(1) Compute a static, spherically symmetric solution of the field equation. It will be singular at the origin. This will be taken to be the field generated by a single particle.

(2) Move the solution on a trajectory P and apply the instantaneous Lorentz transformation based on instantaneous velocity.

(3) Take, as first approximation, the field generated by N particles to be the superposition of the fields generated by the single particles.

(4) Compute the leading part of the equation. Hopefully, only terms that involve the acceleration will be dominant. This is the "inertial" part.

(5) Compute the quadratic part of the equation. This is the agent of the "force".

(6) Equate for each singularity, the highest order terms of the singularities that came from the linear part and the quadratic parts, respectively. This is an equation between the inertial part and the force.

The algorithm was applied to Einstein's equations. The approximate evolution of the scalar curvature leads, in turn, to an invariant scalar equation. The algorithm for it did produce Newton's law of gravitation. This is, also, the starting point for the embedding of the trajectories in a common field.
IS THERE CLASSICAL SUPER-RADIANCE ON KERR-NEWMAN-ANTI-DE SITTER BLACK HOLES?
Authors: WINSTANLEY ELIZABETH
Published: October 2002

Since the formulation of the AdS/CFT correspondence 1, there has been great interest in space-times which are asymptotically anti-de Sitter, and the properties of the Kerr-Newman-anti-de Sitter (KN-AdS) space-time in various dimensions have been extensively studied 2. However, the properties of classical or quantum fields propagating on this background have not been widely studied, and, in particular, the question of whether super-radiance occurs has not been addressed. This is an important issue since a detailed understanding of classical super-radiance is necessary before tackling quantum field theory on rotating black hole geometries 3.

We considered a classical scalar field on the KN-AdS background 4, and examined the form of the separated field modes. Given the structure of infinity in asymptotically anti-de Sitter space-times, we paid particular attention to the boundary conditions at infinity.

Unlike the situation for asymptotically flat Kerr-Newman black holes 5, super-radiance is not inevitable. It depends partly on our choice of boundary condition at infinity. For reflective boundary conditions at infinity, there is no super-radiance. On the other hand, if we consider transparent boundary conditions at infinity, then the presence of super-radiance depends on our choice of positive frequency. For those KN-AdS black holes possessing a globally time-like Killing vector, then the natural definition of positive frequency implies that there are no super-radiant modes. For other KN-AdS black holes, then this same definition of positive frequency again leads to no super-radiance.
Searches for Prompt Heavy Quarkonia & ${\rm B}^\pm_{\rm c}$ Mesons and Evidence for Radially Excited B Mesons in Z0 Decays
Authors: Eigen Gerald
Published: October 2002

We have searched for prompt heavy quarkonia and Bc mesons in 3 × 106 hadronic Z0 decays recorded with the DELPHI detector at LEP. No signal was observed in any of these modes. We achieved the highest sensitivities for gluon fragmentation into J/ψ and for semileptonic [Formula: see text] decays, yielding branching ratio upper limits of [Formula: see text] and [Formula: see text] @ 90% CL, respectively. We found the first evidence for radially excited B mesons, by observing a signal in the B(*)π+ π- final state at Q = m(B(*) π+π-) - m(B(*)) - 2m(π) = 301 ± 4 ± 10 MeV.
Search for Bc and ϒ in Hadronic Z Decays
Authors: McNeil M.
Published: October 2002

Out of 3.9 million hadronic Z decays collected by the ALEPH detector, a sample of approximately 700 J/ψ events decaying into e+ e- or μ+μ- are selected. A search for the Bc meson decaying into the channels J/ψπ+, J/ψe+νe and J/ψμ+νμ is then performed, resulting in the observation of 0, 1 and 1 candidate in each of these channels respectively, with 0.37, 0.28 and 0.36 background events expected. The following 90% confidence level upper limits are derived:

[Formula: see text]

An intriguing candidate, found in an independent analysis, is also described in detail.

Using the same data sample, a search is performed for the ϒ(1S), ϒ(2S) and ϒ(3S) states, decaying into either e+e- or μ+μ-. After kinematic and topological cuts a total of 1.2 ± 0.4 background events are expected for both channels in the mass window chosen. Two events are observed, allowing the following 90% confidence level branching fraction upper limit to be derived:

[Formula: see text]
QUANTUM ALGORITHMS FOR GENERATING RANDOM SEQUENCES OF INTEGERS
Authors: RASETTI MARIO , SBURLATI GIOVANNI
Published: October 2002

We present two quantum algorithms which generate a random sequence of integers modula a given N ∈ ℕ in which the expected frequency distribution over the set ℤN is different from the uniform distribution.
EFFECT OF IMPURITIES AND EFFECTIVE MASSES ON SPIN-DEPENDENT ELECTRICAL TRANSPORT IN FERROMAGNET-NORMAL METAL-FERROMAGNET HYBRID JUNCTIONS
Authors: ZHU ZHEN-GANG , SU GANG , JIN BIAO , ZHENG QING-RONG
Published: October 2002

The effect of nonmagnetic impurities and the effective masses on the spin-dependent transport in a ferromagnet-normal metal-ferromagnet junction is investigated on the basis of a two-band model. Our results show that impurities and the effective masses of electrons in two ferromagnetic electrodes have remarkable effects on the behaviors of the conductance, namely, both affect the oscillating amplitudes, periods, as well as the positions of the resonant peaks of the conductance considerably. The impurity tends to suppress the amplitudes of the conductance, and makes the spin-valve effect less obvious, but under certain conditions the phenomenon of the so-called impurity-induced resonant tunneling is clearly observed. The impurity and the effective mass both can lead to nonmonotonous oscillation of the junction magnetoresistance (JMR) with the incident energy and the thickness of the normal metal. It is also observed that a smaller difference of the effective masses of electrons in two ferromagnetic electrodes would give rise to a larger amplitude of the JMR.
MAGNETIC SUSCEPTIBILITY STUDIES OF B2O3-BaO-Fe2O3 GLASSES
Authors: ARDELEAN I. , TODERAS MONICA
Published: October 2002

Magnetic susceptibility studies have been done on x Fe 2 O 3 · (100-x) [3 B 2 O 3 · BaO ] glasses with 0 < x ≤ 50 mol%. For x ≤ 10 mol% it was shown that the glasses studied obey a Curie law and only Fe 3+ ions are present, but for higher concentrations the magnetic susceptibility is described by a Curie–Weiss law and both Fe 3+ and Fe 2+ valence states, which participate in antiferromagnetic interactions, are evidenced.
DEMONSTRATION OF SPEED AND POWER ENHANCEMENTS ON AN INDUSTRIAL CIRCUIT THROUGH APPLICATION OF CLOCK SKEW SCHEDULING
Authors: VELENIS D. , TANG K. T. , KOURTEV I. S. , ADLER V. , BAEZ F. , FRIEDMAN E. G.
Published: October 2002

A strategy to enhance the speed and power characteristics of an industrial circuit is demonstrated in this paper. It is shown that nonzero clock skew scheduling can improve circuit performance while relaxing the strict timing constraints of the critical data paths within a high speed system. A software tool implementing a nonzero clock skew scheduling algorithm is described together with a methodology that generates the required clock signal delays. Furthermore, a technique that significantly reduces the power dissipated in the noncritical data paths is demonstrated. The application of this technique combined with nonzero clock skew scheduling to the slower data paths is also described. Speed improvements of up to 18% and power savings greater than 80% are achieved in certain functional blocks of an industrial high performance microprocessor.
SPATIO-TEMPORAL CHAOS AND SOLITONS EXHIBITED BY VON KÁRMÁN MODEL
Authors: AWREJCEWICZ J. , KRYSKO V. A. , KRYSKO A. V.
Published: October 2002

Forced oscillations of flexible plates with a longitudinal, time dependent load acting on one plate side are investigated. Regular (harmonic, subharmonic and quasi-periodic) and irregular (chaotic) oscillations appear depending on the system parameters as well as initial and boundary conditions. In order to achieve highly reliable results, an effective algorithm has been applied to convert a problem of finding solutions to the hybrid type partial differential equations (the so-called von Kármán form) to that of the ordinary differential equations (ODEs) and algebraic equations (AEs). The obtained equations are solved using finite difference method with the approximations 0(h4) and 0(h2) (in respect to the spatial coordinates). The ODEs are solved using the Runge–Kutta fourth order method, whereas the AEs are solved using either the Gauss or relaxation methods. The analysis and identification of spatio-temporal oscillations are carried out by investigation of the series wij(t), wt,ij(t), phase portraits wt,ij (wij) and wtt,ij(wt,ij, wij) and the mode portraits in the planes wx,ij(wij), wy,ij (wij) and in the space wxx(wx,ij,wij), FFT as well as the Poincaré sections and pseudo-sections.
SIMULATIONS OF GLYCOLYTIC OSCILLATIONS IN CELLS WITH COMPARTMENTS
Authors: ZHDANOV VLADIMIR P.
Published: October 2002

We present Monte Carlo simulations of glycolytic oscillations inside the cell with a chemically inactive compartment. The model employed takes into account the glucose supply to the cell via the cell membrane and a few elementary reaction steps running inside the cell in the area between the external membrane and the compartment. The model parameters are chosen so that the typical size of oscillatory patterns is comparable with the cell size. Although the compartment does not directly participate in the reaction, its presence is found to amplify irregular oscillations provided that the compartment size is appreciable and it is located in the center of the cell.
SUFFICIENT CONDITIONS FOR A CENTER AT A COMPLETELY DEGENERATE CRITICAL POINT
Authors: GINÉ J.
Published: October 2002

Consider the two-dimensional autonomous systems of differential equations of the form [Formula: see text] where P3(x, y) and Q3(x, y) are homogeneous polynomials of degree 3, and P4(x, y) and Q4(x, y) are homogeneous polynomials of degree 4. The origin is a completely degenerate critical point of this system. In this work we give sufficient conditions in order to have a center at the origin.
ADAPTIVE SYNCHRONIZATION FOR RÖSSLER AND CHUA'S CIRCUIT SYSTEMS
Authors: HEGAZI A. S. , AGIZA H. N. , EL-DESSOKY M. M.
Published: October 2002

This study addresses the adaptive synchronization of Rössler and Chua circuit systems with unknown parameters. By using Lyapunov stability theory the adaptive synchronization law with a single-state variable feedback is derived, such that the trajectory of the two systems are globally stabilized to an equilibrium point of the uncontrolled system (globally stable means that the method of the solution is restricted in area of phase space i.e. globally in a subset of a phase space with bounded zero volume). We use the Lyapunov direct method to study the asymptotic stability of the solutions of error system. Numerical simulations are given to explain the effectiveness of the proposed control scheme.
EDGE ADVANCING RULES FOR INTERSECTING SPHERICAL CONVEX POLYGONS
Authors: HA JONG-SUNG , SHIN SUNG-YONG
Published: October 2002

In this paper, we propose new rules of advancing edges for computing the intersection of a pair of convex polygons in the plane. These rules have no ambiguities when extended into the spherical surface, differently from those of O'Rourke et al.4 Finally, we design a linear-time algorithm for computing the intersection of a pair of spherical convex polygons, and prove its correctness.
BIRGET–RHODES EXPANSION OF GROUPS AND INVERSE MONOIDS OF MÖBIUS TYPE
Authors: CHOI KEUNBAE , LIM YONGDO
Published: October 2002

In this paper we prove that if a group G acts faithfully on a Hausdorff space X and acts freely at a non-isolated point, then the Birget–Rhodes expansion [Formula: see text] of the group G is isomorphic to an inverse monoid of Möbius type obtained from the action.
SOME LOOP ALGEBRAS OF HAMILTONIAN LIE ALGEBRAS
Authors: AVITABILE MARINA
Published: October 2002

We consider a class of thin Lie algebras with second diamond in weight a power of the characteristic of the underlying field. We identify these Lie algebras with loop algebras of a graded Hamiltonian algebra or loop algebras of an extension of the Hamiltonian algebra by an outer derivation. We also prove that the Lie algebras considered are not finitely presented.
SECOND ORDER SCALAR INVARIANTS OF THE RIEMANN TENSOR: APPLICATIONS TO BLACK HOLE SPACETIMES
Authors: CHERUBINI CHRISTIAN , BINI DONATO , CAPOZZIELLO SALVATORE , RUFFINI REMO
Published: October 2002

We discuss the Kretschmann, Chern–Pontryagin and Euler invariants among the second order scalar invariants of the Riemann tensor in any spacetime in the Newman–Penrose formalism and in the framework of gravitoelectromagnetism, using the Kerr–Newman geometry as an example. An analogy with electromagnetic invariants leads to the definition of regions of gravitoelectric or gravitomagnetic dominance.
THE GENERALITY OF INFLATION IN SOME CLOSED FRW MODELS WITH A SCALAR FIELD
Authors: PAVLUCHENKO S. A. , TOPORENSKY A. V. , SAVCHENKO N. YU.
Published: October 2002

The generality of inflation in closed FRW Universe is studied for the models with a scalar field on a brane and with a complex scalar field. The results obtained are compared with the previously known results for the model with a scalar field and a perfect fluid. The influence of the measure chosen in the initial condition space on the ratio of inflationary solution is described.
PERSISTENCE AND GLOBAL STABILITY OF A POPULATION IN A POLLUTED ENVIRONMENT WITH DELAY
Authors: MUKHERJEE DEBASIS
Published: October 2002

This article concentrates on the study of delay effect on a model of single species in a polluted closed environment. The cases of constant emission and instantaneous spill of a toxicant are considered in the model study. Sufficient criteria on persistence of the population are derived. Global attractivity condition for the positive equilibrium is obtained.
UV/VUV FREE ELECTRON LASER OSCILLATORS AND APPLICATIONS IN MATERIALS SCIENCE
Authors: MARSI M. , LOCATELLI A. , TROVÒ M. , WALKER R. P. , COUPRIE M. E. , GARZELLA D. , NAHON L. , NUTARELLI D. , RENAULT E. , GATTO A. , KAISER N. , GIANNESSI L. , GÜNSTER S. , RISTAU D. , POOLE M. W. , TALEB-IBRAHIMI A.
Published: October 2002

After having reached the status of user facilities in the infrared, Free Electron Laser (FEL) oscillators are becoming interesting light sources for scientific research also in the UV/VUV wavelength region. Thanks to continuous advances in accelerator and mirror technology, it has been possible to reach with tunability energies which are hardly accessible with conventional lasers (the European FEL project at Elettra recently lased below 190 nm), with the realistic perspective of reaching even shorter wavelengths in the near future. Thanks to their unique properties, such as tunability, full coherence, high intensity, spectral and temporal stability, they offer new opportunities for many kinds of spectroscopy: in particular, storage ring FELs are ideal sources for pump–probe experiments in conjunction with synchrotron radiation, as demonstrated by a series of studies of the nonequilibrium space charge distribution at photoexcited Si surfaces and interfaces performed at SuperACO. Besides, especially when operated at shorter wavelengths, FEL oscillators are very attractive also for one-photon experiments requiring high power and full tunability. We describe here the properties of the sources, and provide an overview of the experiments that have been performed and that are planned to exploit the new opportunities they offer.
XPEEM WITH ENERGY-FILTERING: ADVANTAGES AND FIRST RESULTS FROM THE SMART PROJECT
Authors: SCHMIDT TH. , GROH U. , FINK R. , UMBACH E. , SCHAFF O. , ENGEL W. , RICHTER B. , KUHLENBECK H. , SCHLÖGL R. , FREUND H.-J. , BRADSHAW A. M. , PREIKSZAS D. , HARTEL P. , SPEHR R. , ROSE H. , LILIENKAMP G. , BAUER E. , BENNER G.
Published: October 2002

The second development step of the SMART project, i.e. an energy-filtered but not yet corrected photoelectron emission microscope, operates at the undulator U49/1-PGM beamline at BESSY II. It already demonstrates the variety of methods of the final version: microscopy, spectroscopy and electron diffraction. Some recent experimental results are reported for these three operation modes. In addition, the theoretical improvement of lateral resolution and transmission of PEEMs in general by using an energy filter is discussed for systems without and with aberration correction.
X-RAY MAGNETIC CIRCULAR DICHROISM IMAGING IN A LOW ENERGY ELECTRON MICROSCOPE
Authors: LOCATELLI A. , CHERIFI S. , HEUN S. , MARSI M. , ONO K. , PAVLOVSKA A. , BAUER E.
Published: October 2002

The magnetic domain structure of patterned permalloy films and of a Co(0001) single crystal surface are studied with elliptically polarized light from the new nanospectroscopy beamline at ELETTRA in a low energy electron microscope, using it as a diagnostic tool in the commissioning phase of the beamline. Mirror and low energy electron microscopy as well as low energy electron diffraction are shown to be valuable fast techniques for system alignment and specimen characterization.
AUGER ELECTRON SPECTRA OF Kr2p HOLES USING MONOCHROMATIC SOFT X-RAYS
Authors: SUZUKI I. H. , OKADA K. , KAMIMORI K. , SASAKI J. , YOSHIDA H. , HIRAYA A. , SHIMIZU Y. , NAGAOKA S. , TAMENORI Y. , OHASHI H. , IBUKI T.
Published: October 2002

Normal Auger electron spectra from Kr2p hole states, L 23 M 45 M 45 and L 23 M 23 M 45, have been measured using monochromatized synchrotron radiation and a high resolution electron spectrometer. Measured spectra were reproduced with a fitting calculation, where Voigt functions including an instrumental resolution and natural lifetime widths of related core hole states were used. At most final states estimated energies for spectral peaks agree with those by electron and ion beam techniques. Relative intensities for some peaks are appreciably different from the previous results.
SELECTIVE CLEAVAGE OF FUNCTIONAL GROUPS IN THE FUNCTIONALIZED ORGANIC MONOLAYERS BY SYNCHROTRON SOFT X-RAYS
Authors: KANG TAI-HEE , KIM KI-JEONG , HWANG CHAN-CUK , IHM KYU-WOOK , SHIN HYUN-JOON , LEE MIN-KYU , KIM BONGSOO , PARK CHONG-YUN , LA YOUNG-HYE , MOON JOONG HO , KIM HYUN JU , PARK JOON WON
Published: October 2002

Aminosilylated surface was treated with halide-substituted aromatic aldehydes, and the resulting molecular layers were examined with synchrotron X-ray photoelectron spectroscopy at the 2B1 SGM and 4B1 microscopy beamline in the Pohang Accelerator Laboratory. It was observed that the halide group of the film diminished upon the irradiation, but the other bands were constant in terms of the intensity and the shape. This observation indicates that the functional groups of the organic monolayers are cleaved selectively by soft X-rays. The cleavage rate was measured as a function of photon energy and normalized with photon flux. The cleavage is first-order to the concentration of the functional group. Its rate constant is sensitive to the molecular structure of the organic monolayers and the kind of substituents on the aromatic ring.
PHOTODEGRADATION OF POLY(TETRAFLUOROETHYLENE) AND POLY(VINYLIDENE FLUORIDE) THIN FILMS BY INNER SHELL EXCITATION
Authors: OKUDAIRA KOJI K. , YAMANE HIROYUKI , ITO KAZUYUKI , IMAMURA MOTOYASU , HASEGAWA SHINJI , UENO NOBUO
Published: October 2002

Ion time-of-flight (TOF) mass spectra of poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) thin films near fluorine and carbon K-edges were observed. For PTFE thin films, peaks corresponding to F +, CF +, and [Formula: see text] appeared, while for PVDF F + and H + were mainly observed. They indicate that for PTFE the polymer chain (C–C bonds) as well as C–F bonds are broken by irradiation of photons near fluorine and carbon K-edges, while for PVDF the bond scission occurs mainly at the C–F and C–H bond. Partial ion yields (PIY) of these ions for PTFE and PVDF thin films show strong photon energy dependencies near fluorine and carbon K-edges. The excitation from fluorine 1s to σ( C – F )* is specially efficient for F + ion production for both PTFE and PVDF.
FEASIBILITY STUDIES OF THE THREE-DIMENSIONAL DETECTOR FOR SOFT X-RAY EMISSION SPECTROSCOPY
Authors: OURA M. , KOBAYASHI K. , WATANABE M. , HARADA Y. , SUZUKI T. , SHIN S. , JAGUTZKI O.
Published: October 2002

A time-resolving two-dimensional position-sensitive detector was applied to soft X-ray emission spectroscopy (SXES) and its feasibility was successfully studied by using synchrotron radiation. A soft X-ray emission spectrum synchronously acquired with bunch signal of the storage ring has elucidated that a threefold higher signal-to-noise ratio could at least be achieved. By adopting a pump–probe technique to SXES, we have preliminarily studied the effect of the electron–hole plasma (EHP) on the Si 2p soft X-ray emitting processes of Si crystal. A meaningful change in the excitation curve for the elastic scattering yields near the 2p thresholds was found to be probably due to the many-body interactions caused by the EHP.
A SOFT X-RAY UNDULATOR BEAMLINE AT THE ADVANCED LIGHT SOURCE WITH CIRCULAR AND VARIABLE LINEAR POLARIZATION FOR THE SPECTROSCOPY AND MICROSCOPY OF MAGNETIC MATERIALS
Authors: YOUNG ANTHONY T. , ARENHOLZ ELKE , FENG JUN , PADMORE HOWARD , MARKS STEVE , SCHLUETER ROSS , HOYER EGON , KELEZ NICHOLAS , STEIER CHRISTOPH
Published: October 2002

A new undulator beamline at the Advanced Light Source, Lawrence Berkeley National Laboratory is described. This new beamline has an Apple II type undulator which produces linearly and elliptically polarized X-rays. A high resolution monochromator directs the radiation to two branchlines. The first branchline is optimized for spectroscopy and accommodates multiple endstations simultaneously. The second branchline features a photoemission electron microscope. A novel feature of the beamline is the ability to produce linearly polarized radiation at arbitrary, user-selectable angles. Applications of the new beamline are also described.
DEVELOPMENT OF SUPERCONDUCTING TUNNEL JUNCTIONS FOR EUV DETECTORS
Authors: TAKIZAWA Y. , IKEDA T. , OKU T. , OTANI C. , KAWAI K. , SATO H. , SHIMIZU H. M. , MIKAMI H. , MIYASAKA H. , WATANABE H.
Published: October 2002

Superconducting tunnel junctions (STJs) are applicable to as photon detectors with an energy resolution and a high photon-counting rate. The absorption of a photon in the superconductor of the STJ generates a number of quasiparticles that is proportional to the photon energy. Especially for soft X-ray and extreme ultraviolet (EUV) applications, STJs have good performance because of their high absorption efficiency below 1 keV. We are developing an energy-dispersive photon detector for EUV radiation using STJs with Al trapping layers. We evaluated the performance of the detector for EUV photons by using the Synchrotron Facility at KEK-PF in Tsukuba, Japan. We achieved an energy resolution of FWHM=18 eV (including the external noise of 17.6 eV) for 55 eV EUV photons with a 100 × 100 μ m 2 STJ. We present details of the junction design and discuss our experiments and the results.
DESIGN AND FABRICATION OF MULTILAYER MIRRORS FOR He-II RADIATION
Authors: HOTTA YOSHIFUMI , FURUDATE MINAJI , YAMAMOTO MASAKI , WATANABE MAKOTO
Published: October 2002

Design, fabrication, and reflectance evaluation of multilayer mirrors for He-II radiation are described. Based on the available complex refractive indices of materials at the wavelength of 30.4 nm, Mg, Al, Si, Cr, and C were selected as small absorption material to be paired. Mo/Si and Sc found in previous works were also included. In referring to optimum design for the highest reflectance, multilayers of Al/Mg, Au/Mg, C/Mg, Sc/Mg, C/Si, Al/C, and Mo/Si were fabricated by ion-beam sputtering. The highest reflectance of 27% was observed by a 15-period Mg/Sc mirror.
CHANGES INDUCED IN THE SURFACE ELECTRONIC STRUCTURE OF Be(0001) AFTER Si ADSORPTION
Authors: JOHANSSON L. I. , VIROJANADARA C. , BALASUBRAMANIAN T.
Published: October 2002

A study of effects induced in the Be 1s core level spectrum and in the surface band structure after Si adsorption on Be(0001) is reported. The changes in the Be 1s spectrum are quite dramatic. The number of resolvable surface components and the magnitude of the shifts do decrease and the relative intensities of the shifted components are drastically different compared to the clean surface. The surface band structure is also strongly affected after Si adsorption and annealing. At [Formula: see text] the surface state is found to move down from 2.8 to 4.1 eV. The band also splits at around 0.5 Å-1 along both the [Formula: see text] and [Formula: see text] directions. At [Formula: see text] and beyond [Formula: see text] only one surface state is observed in the band gap instead of the two for the clean surface. Our findings indicate that a fairly small amount of Si in the outer atomic layers strongly modifies the electronic properties of these layers.
TRACKING THERMALLY DRIVEN MOLECULAR REACTION AND FRAGMENTATION BY FAST PHOTOEMISSION: C60on Si(111)
Authors: GOLDONI A. , LARCIPRETE R. , CEPEK C. , MASCIOVECCHIO C. , EL MELLOUHI F. , HUDEJ R. , SANCROTTI M. , PAOLUCCI G.
Published: October 2002

We followed in real time the thermal reaction of fullerene molecules with the Si(111) surface by means of fast photoemission spectroscopy. The formation of SiC via C 60 fragmentation on Si(111) is used as a key example of the capability of fast photoemission, associated with a fine temperature control, in determining the nature of thermally induced chemical reactions. By monitoring every 13 s the evolution of the C 1s core level photoemission spectrum, as a function of temperature and as a function of time at fixed temperature, we were able to identify several steps in the interaction of C 60 with Si(111). A model describing the thermal evolution of this interaction, in agreement with these and other experimental observations, considers the initial chemisorption of C 60 in mainly metastable configurations, the evolution toward more stable configurations, allowed by molecular rotations and breaking of Si–Si bonds, the cage deformation to further increase the number of C–Si bonds, the final cage fragmentation and SiC formation only above 1050 ± 10 K .
VACUUM ULTRAVIOLET EMISSION FROM A LASER-PRODUCED PLASMA AND SPECTROSCOPIC APPLICATION TO A SOLID STATE MATERIAL
Authors: KAKU MASANORI , YAMAURA TAKAHIRO , KUBODERA SHOICHI , SASAKI WATARU
Published: October 2002

Vacuum ultraviolet (VUV) continua emitted from a laser-produced plasma have been utilized for the spectroscopy of a solid state laser material. An absorption spectrum of 0.1% Nd:LaF 3 has been measured by use of the continuum emission. The minimum absorption coefficient of 1.4 cm -1 was evaluated at 174 nm.
HIGH ENERGY RESOLUTION MAGNETIC CIRCULAR DICHROISM MEASUREMENT OF THE FERRITE FAMILY
Authors: AGUI AKANE , SAITOH YUJI , YOSHIGOE AKITAKA , NAKATANI TAKESHI , MATSUSHITA TOMOHIRO , MIZUMAKI MASAICHIRO
Published: October 2002

Magnetic circular dichroism (MCD) spectra of spinel ferrites MFe 2 O 4 (M = Co, Mn, Fe, Co and Ni) have been measured by using a photon-helicity-switching method. The method achieves high energy resolution and a low noise-to-signal ratio. The Fe L2,3 absorption spectra of MFe 2 O 4 show a similar spectral profile; on the other hand, the MCD spectra show the characteristic fine structures. These differences are attributed to the variety of 3d electron configuration of Fe ions ( Fe 2+ or Fe 3+) and the local symmetry (tetrahedral or octahedral). The origin of the positive peak of MFe 2 O 4 (M = Fe, Co and Ni) MCD spectra at the L3 edge is attributed to the tetrahedral Fe 3+ (3d5) state.
SPIN ARRANGEMENT OF THE Mn/Fe(001) SYSTEM INVESTIGATED BY SPIN-POLARIZED PHOTOELECTRON DIFFRACTION
Authors: OKUDA TAICHI , HARASAWA AYUMI , KINOSHITA TOYOHIKO , NAKAYAMA KENTARO , FUJIKAWA TAKASHI , CHASSÉ ANGELIKA
Published: October 2002

We demonstrate the application of the advanced spin-polarized photoelectron diffraction (SPPD) method, the photoelectron diffraction measurement of specific core levels in different spins, to the investigation of the spin arrangement of magnetic overlayers on magnetic thin films. Comparing the experimental SPPD result of the Mn 3p core level with that of calculation, we have determined the possible spin arrangements of the Mn overlayer (~1 ML) on the Fe(001) thin film which was epitaxially grown on Ag(001) substrate. Consequently, one of the most plausible spin arrangements of this system is a c (2 × 2) ordering of Mn atoms on the ferromagnetic Fe substrate. The other possible spin arrangement is a p (2 × 2) ordering of Mn atoms ferromagnetically coupled with the ferromagnetic Fe substrate. In both cases, the c (2 × 2) surface reconstruction is necessary to reproduce the experimental results properly.
UNIFIED THEORY ON ANGLE-RESOLVED PHOTOEMISSION AND LIGHT ABSORPTION SPECTRA OF STRONGLY CORRELATED ELECTRON SYSTEMS
Authors: TOMITA NORIKAZU , NASU KEIICHIRO
Published: October 2002

Very recently, the angle-resolved photoemission spectrum (ARPES) of [ Ni(chxn) 2 Br]Br 2 (chxn=1R, 2R-cyclohexanediamine), which is a typical one-dimensional Mott insulator, has been experimentally observed. The experiment has strongly suggested that a one-body gap, which is defined as double the ARPES gap, is much smaller than an optical gap given by the light absorption spectrum (LAS). The apparent difference between these two gaps indicates the breakdown of a mean field description of this strongly correlated electron system. In this paper, we show, by using a quantum Monte Carlo method, that the ARPES and LAS of [Ni(chxn) 2 Br]Br 2 are consistently explained within the framework of the one-dimensional extended Hubbard model. It is suggested that the large difference between the one-body and optical gaps is caused by the dynamical Zeeman field induced by the quantum fluctuations.
OXIDATION AND ANNEALING EFFECT ON COBALT FILMS ON PALLADIUM(111)
Authors: KIM WOOKJE , OH S.-J. , NAHM TSCHANG-UH
Published: October 2002

We have investigated the effects of oxygen exposure on Co films grown on Pd(111) single crystal using magneto-optical Kerr effect and X-ray photoemission spectroscopy. Upon 300-langmuir oxygen exposure, the cobalt films are oxidized as CoO and a small amount of Co 3 O 4, the latter being reduced to CoO on short heating at temperatures higher than 700 K. The ferromagnetic properties disappear by oxygen exposure. However, part of CoO decomposes into cobalt and oxygen on further annealing, and the ferromagnetic property reappears.
USXES AND OPTICAL PHENOMENA IN Si LOW-DIMENSIONAL STRUCTURES DEPENDENT ON MORPHOLOGY AND SILICON OXIDE COMPOSITION ON Si SURFACE
Authors: TORCHYNSKA T. V. , MORALES RODRIGUEZ M. , POLUPAN G. P. , KHOMENKOVA L. I. , KORSUNSKAYA N. E. , PAPUSHA V. P. , SCHERBINA L. V. , DOMASHEVSKAYA E. P. , TEREKHOV V. A. , YU. TURISCHEV S.
Published: October 2002

It has been shown that the intensive and broad "red" photoluminescence band in porous silicon is a nonelementary one and could be decomposed on at least three elementary bands. Photoluminescence, ultrasoft X-ray emission spectroscopy, infrared absorption and atomic force microscopy methods were used to study the reasons for both luminescence band appearance in porous silicon photoluminescence spectra, prepared in different technological conditions. The mechanisms of radiative transition for both elementary bands have been discussed as well.
DIRECT AND RESONANT PHOTOEMISSION STUDY OF ULTRATHIN Gd ON W(110)
Authors: RADER O. , PAMPUCH C. , SHIKIN A. M.
Published: October 2002

Gd/W(110) represents an important system for understanding magnetic coupling phenomena and the magnetic structure of rare earths. In connection with our study of quantum-well states in this system, there is a remarkable behavior of photoemission spectra at lowest coverages (0–3 monolayers). After the disappearance of W surface-derived features, a set of intense, sharp features appears in the energy region of the Gd bulk band gap. Their origin is tested using resonant photoemission at the Gd 4d–4f excitation threshold.
SELF-ENERGY EFFECTS IN THE UNOCCUPIED AND OCCUPIED ELECTRONIC STRUCTURE OF Cu
Authors: STROCOV V. N. , NILSSON P. O. , CLAESSEN R. , ARYASETIAWAN F. , BLAHA P. , THEMLIN J.-M. , NICOLAY G. , HÜFNER S.
Published: October 2002

We report on self-energy effects in the electronic structure of Cu as a prototype weakly correlated system containing electron states of different localization. The unoccupied and occupied excited states were mapped fully resolved in the three-dimensional k using very-low-energy electron diffraction and photoemission, respectively. The self-energy corrections to the density-functional theory show distinct band- and k-dependence. These results are well described by quasiparticle GW calculations, especially for less localized states. We find correlation of the self-energy effects with spatial overlap of the one-electron wave function with the electron density, and elucidate the essential physics of this effect based on the electron-gas exchange correlation behavior.
X-RAY ABSORPTION SPECTROSCOPY IN NaCo2O4, LaCoO3andSrCoO3
Authors: MATSUSHITA TOMOHIRA , MIZUMAKI MASAICHIRO , IKEDA NAOSHI , NAKAZAWA MAKOTO , AGUI AKANE , SAITOH YUJI , NAKATANI TAKESHI , YOSHIGOE AKITAKA , NAKAMURA SHIN
Published: October 2002

We have performed Co 2p X-ray absorption spectroscopy (XAS) on a mixed valence hexagonal layered system NaCo 2 O 4, which shows large thermopower and metallic conductivity. We also measured XAS for SrCoO 3 and LaCoO 3 as examples of typical Co ionic states. The Co ions of the last two materials are octahedrally surrounded by oxygen atoms. A Co atom in NaCo 2 O 4 also has octahedral coordination with oxygen atoms but it is distorted slightly. The Co ions in SrCoO 3 and LaCoO 3 are in the d5 and d6 configuration respectively. The spectrum of NaCo 2 O 4 resembles that of LaCoO 3 rather than that of SrCoO 3; the Co ions in NaCo 2 O 4 can be regarded as the d6 configuration. Also, we have tried to calculate the XAS spectra by using the charge-transfer multiplet model (CT-M). Although we could not find out the best-fitting parameters, the results suggested the itinerancy of the Co 3d states.
VACUUM ULTRAVIOLET ABSORPTION SPECTRA OF SOLID HYDROGEN HALIDES
Authors: WATANABE MAKOTO , OKADA KAZUMASA , IBUKI TOSHIO
Published: October 2002

Absorption spectra of solid HCl, HBr and HI films deposited on LiF single crystals cooled at 103–104 K and those annealed have been obtained in the 4–11.5 eV region. The first peaks found around the absorption edges correspond to the first bands (dissociative) in isolated molecules, so that they are regarded as Frenkel exciton peaks. The spectral feature of as-deposited films changed after annealing irreversibly, which suggests the structural transition from an amorphous phase to a crystalline phase in HCl and HBr. In HI, it was revealed that the first band in the gaseous phase consists of three components. The broad structures found above the first peaks do not resemble the structures of the isolated molecules in the same energy region which consist of many lines. The band structures of solid hydrogen halides seem to resemble those of sodium halide crystals and solid rare gases.
LOW TEMPERATURE STUDIES OF THE DIELECTRIC AND ELECTRICAL PARAMETERS OF GLASSY Se90Ge10-xInx
Authors: ABOU EL-HASSAN S.
Published: October 2002

The dielectric properties of the system Se 90 Ge 10-x In x (x = 2, 4 and 6 at. %) were studied in the temperature range of 78–273 K and in the frequency range of 400 Hz–20 kHz. The density of localized states N(E) and the activation energy of hopping wk for the samples were deduced at different temperatures. The exponents s, m1 and m2 of the equations σ ac (ω) = Aωs, ε′ = Bωm1 and ε′′ = Cωm2 have been deduced for the samples. The composition and temperature dependence of s, m1, m2, wk and N(E) have been determined. The results are interpreted in terms of the correlated barrier hopping (CBH) model and the concept of localized states.