The properties of nuclear matter at zero and finite temperatures

The properties of nuclear matter are studied in the frame of the Brueckner theory. The Brueckner-Hartree-Fock approximation plus two-body density-dependent Skyrme potential which is equivalent to three-body interaction are used. Various modern nucleon-nucleon potentials are used in the framework of the Brueckner-Hartree-Fock approximation, e.g.: CD-Bonn potential, Nijm1 potential, and Reid 93 potential. These modern nucleon-nucleon potentials fit the deuteron properties and are phase shifts equivalent. The equation of state at T = 0, pressure at T = 0, 8, and 12 MeV, free energy at T = 8 and 12 MeV, nuclear matter incompressibility, and the symmetry energy calculation are presented. The hot properties of nuclear matter are calculated using T ²-approximation method at low temperatures. Good agreement is obtained in comparison with previous theoretical estimates and experimental data, especially at low densities.     

The magnetic and hyperfine properties of iron in silicon carbide

The magnetic and hyperfine properties of iron impurities in 3C- and 6H- silicon-carbide are calculated using the abinitio method of full-potential linear-augmented-plane-waves. The iron atoms are introduced at substitutional carbon, Fe _C , and silicon, Fe _Si , sites as well as at the tetrahedral interstitial sites with four nearest neighbours carbon atoms, Fe _I (C), and four nearest neighbours silicon atoms, Fe _I (Si). The effect of introducing vacancies at the neighbours of these sites is also studied. Fe atoms with complete neighbors substituted at Si or C sites are found to be nonmagnetic, while Fe atoms at interstitial sites are magnetic. Introduction of a vacancy at a neighboring site reverse the picture.     

Parametrization of nuclear parton distributions

Optimum nuclear parton distributions are obtained by analysing available experimental data on electron and muon deep inelastic scattering (DIS). The distributions are given at Q ²=1 GeV² with a number of parameters, which are determined by a X ² analysis of the data. Valencequark distributions are relatively well determined at medium x, but they are slightly dependent on the assumed parametrization form particularly at small x. Although antiquark distributions are shadowed at small x, their behavior is not obvious at medium x from the F ₂ data. The gluon distributions could not be restricted well by the inclusive DIS data; however, the analysis tends to support the gluon shadowing at small x. We provide analytical expressions and computer subroutines for calculating the nuclear parton distributions, so that other researchers could use them for applications to other high-energy nuclear reactions.     

Few-body Studies at Nuclotron-JINR

Recent results on the deuteron analyzing powers in dp- elastic scattering obtained at Nuclotron (JINR, Dubna) are compared with the calculations performed within relativistic multiple scattering model. The data demonstrate strong deviation form the predictions at large angles in the cms. The preliminary data on the energy dependence of the cross section in the dp → ppn reaction at 150–250 MeV/nucleon for different configurations and dp elastic scattering up to 1 GeV obtained at internal target station at Nuclotron are reported. The prospects of the further few-body studies at JINR are discussed.     

Energy dependence of peripheral reactions induced by heavy ions

Collisions of ¹⁶O ions on targets of ⁹⁴Zr, ¹⁹⁷Au, ²⁰⁸Pb, and ²³²Th are investigated at incident energies of 140 and 315 MeV and compared to published data on peripheral collisions at 33.6 GeV. At 140 MeV, the isotope-production cross sections resemble the ground-state Q-value systematics characteristic of a partially-equilibrated, di-nuclear system formed in deeply-inelastic scattering. The yields are independent of shell and pairing effects in the target and residual nuclie. These Q-value systematics fail at 315 MeV, where the relative element yields are similar to those at 33.6 GeV. A theory of projectile fragmentation accounts for the shapes of the inclusive energy spectra as well as for the isotope yields at both energies. The relative cross sections are target independent (i.e., factorize) for the data at 315 MeV incident energy, but limiting fragmentation (i.e. isotope yields independent of energy) applies only at higher energies. The differential cross sections peal at the grazing angle or decrease exponentially, depending on the incident energy and the mass of the ejectile; the distributions are described by classical trajectories and diffraction models for which the reaction time is estimated to be typical of direct reactions. The kinetic energies of the reaction products depend primarily on their charge and only slightly on their mass number. For the 315 MeV results, the velocities of the reaction products at the maximum of the spectrum and the grazing angle are slightly less than the beam velocity and decrease rapidly for larger scattering angles. The results are interpreted with simple fraction and fragmentation models, and are compared to observations at 33.6 GeV.     

Nature of oxygen in the passive film on stainless steels in 0.1 M NaCl solution

Three different oxygen species, O^2–, OH^–, and H₂O, are introduced into the deconvolution of the oxygen peaks measured in the prior study and their true concentrations are investigated in the depth profile. It is found that H₂O exists mainly in the outermost part of the passive film at the interface of solution and the passive film. OH^– and O^2– are found throughout the passive film; they have a maximum concentration in the outer layer at around 10 to 20 Å depth, with a concentration of 40 at.% for the stainless steel 29-4-2 and 50 at.% for 18-12. After the maximum the concentrations are sharply reduced with increasing sputtering time and remain at a constant concentration of about 10 at.% at 35 Å depth. Both species still exist at this concentration even after long time sputtering.     

Aerosol Synthesis of Fullerene Nanocrystals in Controlled Flow Reactor Conditions

Fullerene nanocrystals in the size range 30–300 nm were produced starting from atomized droplets of C₆₀ in toluene. The experiments were carried out under well-controlled conditions in a laminar flow reactor at temperatures of 20–600°C. Particle transformation and crystallization mechanisms of polydisperse and monodisperse (size classified) fullerene aerosol particles were studied. The results show that fullerene particles are roughly spherical having pores and voids at temperatures of 300°C and below. Particles are already crystalline and likely fine-grained at 20°C and they are polycrystalline at temperatures up to 300°C. At 400°C monodisperse particles evaporate almost completely due to their low mass concentration. Polydisperse particles are crystalline, but sometimes heavily faulted. At 500°C most of the particles are clearly faceted. In certain conditions, almost all particles are hexagonal platelets having planar defects parallel to large (111) faces. We suggest that at 500°C fullerene particles are partially vaporized forming residuals with lamellar defects such as twins and stacking faults, which promote crystal growth during synthesis. Subsequently fullerene vapor is condensed on faces with defects and hexagonal particles are grown by a re-entrant corner growth mechanism. At 600°C particles are single crystals, but they have a less distinct shape due to higher vaporization of fullerene. The final size and shape of the particles are mainly determined at the reactor outlet in the short time when the aerosol cools.     

Generation and evolution of partial misfit dislocations and stacking faults in thin-film heterostructures

An analysis is made of the specific features in the generation and evolution of partial misfit dislocations at the vertices of V-shaped configurations of stacking fault bands, which terminate in the bulk of the growing film at 90° partial Shockley dislocations. The critical thicknesses h _c of an epitaxial film, at which generation of such defect configurations becomes energetically favorable, are calculated. It is shown that at small misfits, the first to be generated are perfect misfit dislocations and at large misfits, partial ones, which are located at the vertices of V-shaped stacking-fault band configurations emerging onto the film surface. Possible further evolution of stacking-fault band configurations with increasing film thickness are studied.     

Absorption,excitation and fluorescence spectra of thallium activated cesium bromide

Absorption, excitation and fluorescence spectra of T1⁺ doped cesium bromide have been investigated at various thallium concentrations. At very low thallium concentration two absorption bands are obtained at 225 nm and 264 nm. With rise of thallium concentration additional absorption bands are obtained at 230, 244, 258, 270 and 285 nm. A single bell-shaped fluorescence band at 357 nm in the ultraviolet region is obtained at low thallium concentration. Two additional visible fluorescence bands appear at 440 and 540 nm with rise in thallium content. The excitation spectra for ultraviolet emission band and visible emission bands are found to be different. Accordingly the ultraviolet emission band is attributed to the characteristic A emission in T1⁺ ion and the visible bands are attributed to dimer centers havingD _4h site symmetry.     

Composition of oxide compounds supported on metal meshes when synthesizing catalysts for the oxidation of hydrocarbons

Samples of a woven mesh of metal wire (fechral) with supported aluminum hydroxide compounds are studied. Aluminum hydroxide is formed in its bayerite modification. Aluminum oxides are produced during calcination: η-Al₂O₃ at 600°C, and θ-Al₂O₃ at 900°C. Subsequent modification with silicon, cerium, lanthanum, tungsten, and calcination at the same temperature results in the formation of their oxides. Interaction between alumina and tungsten at 600°C, and alumina and lanthanum at 900°C, are observed.     

Simultaneous Generation of Multi-Wavelength Laser from Nd:YAG Crystals in a Cruciform Cavity

A cruciform cavity is presented for multi-wavelength laser generation. On the basis of considering the optimal power ratio and good spatial overlap of the two fundamental beams, the maximum output power of 589 nm laser reaches 3.5 W when the pumping power of Nd：YAG A and Nd：YAG B are 311.5 W and 261.8 W, respectively. At the same time, the other wavelength lasers are also obtained with the output power distribution of 2.5 W at 66Onto, 15 W at 532nm, lOOmW at 1319nm and 240mW at 1064nm. The corresponding beam quality factors are M^2 x = 4.93, M^2 y = 5.01 at 589nm, M^2z = 4.51, M^2 y = 4.85 at 660hm, and M^2 x = 4.12, M^2 y = 3.96 at 532nm, respectively. The instabilities of the three visible lights are measured, which are also less than 2% within three hours.     

Hyperfine interactions in intermetallic compounds between Gd and 3d transition metals

Measurements of hyperfine interactions at ¹⁵⁵Gd nuclei in metallic compounds between Gd and 3d transition metals and at ⁶¹Ni in GdNi compounds by Mössbauer spectroscopy are reported. The results are discussed in terms of various models proposed for the electronic structure of these compounds. The Gd isomer shifts with respect to metallic Gd are at variance with the model of a strong d electron transfer from rare earths to transition metal ions. From the observation of a linear relation between magnetic hyperfine fields at Gd and at Dy nuclei in corresponding compounds it is inferred that crystal-field induced variations of Dy moments are neglible and that the conduction electron polarization induced by 4f moments is directly related to that caused by 3d moments.     

Electron density distribution in GaAs using MEM

Electron density distribution of GaAs is determined by means of the maximum entropy method (MEM) using reasonably good X-ray data collected at room temperature and 200 K. The bonding electron distributions are clearly visible in the MEM map and the mixed covalent-ionic character in GaAs is evidenced. The density distributions at 200 K show more condensed electronic clouds as compared to the room temperature map, preserving the trend in the bonding characters. The electron densities at the middle of the bond are 0.79 and 0.70 e/ų at 200 K and at room temperature, respectively. The refined harmonic thermal factors are in good agreement with the published values.     

First state selective electron capture measurements with trapped highly charged ions

The first state selective electron capture cross section measurements at eV energies are reported for collisions between C⁴⁺ ions and H₂ molecules. The cross sections are measured in a crossed beam experiment by means of Photon Emission Spectroscopy. The ion beams are decelerated in an octopole ion trap where the trap is used to guide the ion beam through the collision region. The experimental results are in excellent agreement with previous measurements at higher energies. The 3-state atomic orbital calculations of Gargaud and McCarroll generally agree with our measurements although there are some discrepancies at lower energies. However, the results for C⁴⁺ are still on a relative scale. To put our measurements on an absolute scale the N⁴⁺+ H system is investigated at keV energies. These results are in good agreement with the data of previous experiments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fiber optical communications devices

Both low attenuation silica optical fibers with peak transmission in the wavelength regions of 0.85 μm, and 1.05 μm, and improved lasers at both wavelengths are now available. In this review paper, the principal components for emission, modulation and detection are described. The characteristics of both semiconductor lasers, made of GaAs and related compounds, emitting at 0.85 μm or 1.05 μm and high neodymium-content lasers are discussed. For modulation, current modulation of GaAs lasers and external electro-optic modulation are considered. Concerning detection, the realisation of Si photodetectors suitable at 0.85 μm and the new photodetectors at 1.05 μm from Ga_1−x In _x As are reviewed.     

Measurement ofL-shell photoelectric cross sections in highZ elements at 37 and 74 keV

L-shell photoelectric cross section measurements have been made at 36·818 and 74·409 keV for four elements in the range 81 ≤Z ≤ 92. The measurements at 74·409 keV are found to agree with theory, within experimental uncertainties, but the experimental values at 36·818 keV are found to be higher than the theoretical predictions. The possible reasons for the observed discrepancy are discussed.     

Antiproton-proton elastic scattering at 6.2 GeV/c

Antiproton-proton elastic scattering data at 6.2 GeV/c in the range 0.3 (GeV/c)² ? ?t ? 10.0 (GeV/c)² is presented. The experiment, using spark chambers and proportional chambers, was performed at the CERN Proton Synchroton.The dip at about ?t = 0.5 and the structure at about ?t = 2.2 (GeV/c)² are equally strong at 6.2 GeV/c as they are at 5.0 GeV/c. The differential cross sections around 90° c.m. are not very different at 5.0 GeV/c and at 6.2 GeV/c, whereas in the backward region there is a decrease of the order of one magnitude.     

Growth and spectroscopic characteristics of Nd-doped PbWO4 crystal

Nd-doped PbWO4 crystals are grown by using the modified Bridgman method.The spectroscopic properties of the crystals are investigated.The changes of the absorption band at 350 nm are discussed for samples annealed at 740℃ and 1040℃.The radiative lifetime of the 4 F 3/2 level is calculated by using the Judd-Ofelt theory according to the absorption spectrum of 0.5 at.% Nd-doped PbWO 4 crystal.The spontaneous Raman scattering properties of the crystals are analysed.     

Interaction between Intermetallic Compounds <Emphasis Type="Italic">R</Emphasis>Ni<Subscript>3</Subscript> (<Emphasis Type="Italic">R</Emphasis> = Gd,Dy) and Hydrogen at Low Temperatures

The hydride phases of the intermetallic compounds GdNi₃ and DyNi₃ are synthesized at room temperature and at 273 K under a hydrogen pressure of 1–30 bar. The phase composition of the obtained samples is established using the X-ray diffraction method and the crystal-lattice parameters of the hydride phase are determined. The crystal phases are synthesized at room temperature under a hydrogen pressure of about 1 bar. At 273 K and under a pressure of 30 bar, amorphous samples are formed. The desorption of hydrogen from amorphous hydrides at 573 K leads to the formation of well-crystallized samples of the initial intermetallides. The amorphous samples are formed due to the ordering of hydrogen atoms in the metallic matrix of the hydride at low temperatures.     

Bulk matter physics and its future at the Large Hadron Collider

Measurements at low transverse momentum will be performed at the LHC for studying particle production mechanisms in pp and heavy-ion collisions. Some of the experimental capabilities for bulk matter physics are presented, focusing on tracking elements and particle identification. In order to anticipate the study of baryon production for both colliding systems at multi-TeV energies, measurements for identified species and recent model extrapolations are discussed. Several mechanisms are expected to compete for hadro-production in the low momentum region. For this reason, experimental observables that could be used for investigating multi-parton interactions and help understanding the “underlying event” content in the first pp collisions at the LHC are also mentioned.