Analysis of the pseudoscalar partner of the Y(4660) and related bound states

In this article, we study the pseudoscalar bound state η _c ′f ₀(980) (irrespective of the hadro-charmonium and the molecular state) with the QCD sum rules. Considering the SU(3) symmetry of the light flavor quarks and the heavy quark symmetry, we also study the bound states η _c ′σ(400?1200), η _b '''f ₀(980) and η _b '''σ(400?1200), and make reasonable predictions for their masses.     

Plasmonics: influence of the intermediate (or stick) layer on the efficiency of sensors

This paper reports the formation of Ge nanoclusters in a multi-layer structure consisting of alternating thin films of Ge-doped silica glass and SiGe, deposited by plasma-enhanced chemical vapor deposition (PECVD) and post annealed at 1100 °C in N₂ atmosphere. We studied the annealed samples by transmission electron microscopy (TEM) and Raman spectroscopy. As-deposited and annealed samples were analyzed by secondary ion mass spectroscopy (SIMS). TEM investigation shows that Ge nanoclusters were formed in the as-deposited SiGe layer and the SiGe layer was transformed into a silicon dioxide layer embedded with Ge nanoclusters after annealing. These nanoclusters are crystalline and varied in size. There were no clusters in the Ge-doped glass layer. Raman spectra verified the existence of crystalline Ge clusters. The positional shift of the Ge vibrational peak with the change of the focus depth indicates that the distribution of the stress applied to the Ge clusters varies with depth. SIMS measurements show clearly the dramatic O increase in the as-deposited SiGe layer after annealing. The creation of Ge nanoclusters by the combination of PECVD and annealing makes possible the application in complicated waveguide components. PACS 81.07.Bc; 78.66.Jg; 42.65.Wi     

One-Parameter Coherent State Representation of the spl(2,1) Superalgebra

One-parameter general coherent states of the spl(2,1) superalgebra are constructed and their properties are discussed in detail. One-parameter matrix elements of the spl(2,1) generators in the one-parameter general coherent-state space are calculated. The parameter α may be related to the interaction parameter U in one exactly solvable model for correlated electrons.     

More on the renormalization of the horizon function of the Gribov–Zwanziger action and the Kugo–Ojima Green function(s)

In this paper we provide strong evidence that there is no ambiguity in the choice of the horizon function underlying the Gribov–Zwanziger action. We show that there is only one correct possibility which is determined by the requirement of multiplicative renormalizability. As a consequence, this means that relations derived from other horizon functions cannot be given a consistent interpretation in terms of a local and renormalizable quantum field theory. In addition, we also discuss that the Kugo–Ojima functions u(p ²) and w(p ²) can only be defined after renormalization of the underlying Green function(s).     

Investigation of the EPR parameters of the rhombic Cu2+ center in (NH4)2Mg(SO4)2·6H2O single crystal

The electron paramagnetic resonance (EPR) parameters (g factors g_x, g_y, g_z and hyperfine structure constants A_x, A_y, A_z) for Cu²⁺ in (NH₄)₂Mg(SO₄)₂·6H₂O (DHMS) crystal are theoretically investigated using the high-order perturbation formulas of these parameters. In the calculations, the ligand orbital and spin–orbit coupling for the impurity Cu²⁺ are taken into account; the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the EPR parameters with the local structure of the impurity center. The ligand orbital and the spin–orbit coupling contributions are included on the basis of the cluster approach. Based on the calculation, the theoretical EPR parameters show good agreement with the observed values. The results are discussed.     

The Effect of the Relative Motion of Atoms on the Frequency of the Emitted Light and the Reinterpretation of the Ives-Stilwell Experiment

We examine the process of the emission of light from an atom that is in a relative translational motion with respect to the medium at rest in which the electromagnetic excitations propagate. The effect of Lorentz contraction of the of electron orbits on the emitted frequency is incorporated in the Rydberg formula, as well as the emitter’s Doppler effect is acknowledged. The result is that the frequency of the emitted light is modified by a factor that is identical with what is called the ‘relativistic Doppler effect’. The new emission formula is applied for reinterpretation of the Ives-Stilwell experiment and shown that within the second order of approximation with respect to the speeds of the atom and the ‘absolute speed’ (Earth’s speed relative to the medium), the absolute motion does not affect the interference. The expression for the modification of the frequency involves both a first and a second-order term with respect to the speed of the atoms in the cathode tube. The latter turns out to be quantitatively the same as if the time would have changed its rate in the frame moving with the atoms. Thus, a new interpretation of the results of this famous experiment is provided without stipulating time dilation.     

Optical second harmonic generation studies of the nature of the oxide-covered and clean c(4 × 4) and (2 × 4) reconstructed GaAs(001) surfaces

We report the application of the “epioptic” technique of optical second harmonic generation (SHG) to the study of surface chemical processes occurring at the technologically important (001) surfaces of the non-centrosymmetric compound semiconductor GaAs. SHG has been used to monitor the thermal removal of surface contamination from an GaAs(001) substrate mounted in a conventional molecular beam epitaxy (MBE) chamber. Rotational anisotropy plots of the reflected SH signal recorded at near-normal incidence indicate that the oxide layer is not fully disordered and possesses some structural anisotropy, i.e. some preferred net surface orientation. In addition the rotational anisotropy plots were observed to change in both intensity and apparent phase between the oxide-covered surface and the clean reconstructed surfaces. Following heating to 850 K under the background As₂ flux present in the chamber, the SH signal from the clean, reconstructed surface was approximately 5 × weaker than that observed for the contaminated surface and was subsequently found to be insensitive to the reconstruction change between the (2 × 4) and c(4 × 4) surfaces, in agreement with theoretical predictions for surfaces having 2mm and 4mm symmetry, respectively.These data are discussed in terms of the difficulties encountered when attempting to observe a surface SH response from a non-centrosymmetric substrate. The sensitivity of the technique towards the thin oxide overlayer suggests that for overlayers which are likely to possess net oriented in-plane dipoles due to the structural mismatch with the substrate, an SH response may be observed in preference to a bulk response when a normal incidence geometry is employed.     

Influence of photoexcitation pathways on the initiation of ablation in poly (methyl methacrylate)

Experimental and theoretical studies of laser ablation of polymers, under various processing conditions, have identified many possible photoexcitation pathways and consequently many likely processes responsible for the onset of ablation. We investigate the role of these processes—namely the thermal, mechanical and chemical processes—occurring in a polymeric substrate during UV irradiation. Molecular dynamics simulations with an embedded Monte Carlo-based reaction scheme were used to study ablation of Poly (methyl methacrylate) at 157 nm. Laser-induced heating and chemical decomposition of the polymeric substrate are considered as ablation pathways. For the heating case, the mechanism of ejection is thermally driven limited by the critical number of bonds broken. This fragmentation process is well reproduced by the existing bulk photothermal ablation model. Alternatively, if the photon energy goes toward direct bond breaking, it initiates chemical reactions, polymer unzipping, and formation of gaseous products leading to near complete decomposition, loss of strength and cohesiveness of the top layers of the polymeric substrate. The ejection of small gaseous molecules weakens and hollows out the substrate, facilitating liftoff of larger fragments of material. These larger clusters are thermally ejected and the photochemical ablation process can be described by the two-step model proposed by Kalontarov.     

Thermal Dehydration and Vibrational Studies of ZnK4(P3O9)2 · 6H2O

The thermal dehydration of ZnK₄(P₃O₉)₂ · 6H₂O was studied in the range 25–500°C by thermogravimetric analysis (TGA and DSC) and X‐ray diffraction. We found, based on the TGA and DSC scans, the dehydration of this salt takes place in three stages with a loss of the six water molecules. The infrared and Raman spectra of ZnK₄(P₃O₉)₂ · 6H₂O have been recorded and interpreted using a factor group analysis. The internal modes are assigned in terms of POP and PO₂ structural units using experimental and theoretical IR and Raman frequencies.     

A Re-interpretation of the Concept of Mass and of the Relativistic Mass-Energy Relation

For over a century the definitions of mass and derivations of its relation with energy continue to be elaborated, demonstrating that the concept of mass is still not satisfactorily understood. The aim of this study is to show that, starting from the properties of Minkowski spacetime and from the principle of least action, energy expresses the property of inertia of a body. This implies that inertial mass can only be the object of a definition—the so called mass-energy relation—aimed at measuring energy in different units, more suitable to describe the huge amount of it enclosed in what we call the “rest-energy” of a body. Likewise, the concept of gravitational mass becomes unnecessary, being replaceable by energy, thus making the weak equivalence principle intrinsically verified. In dealing with mass, a new unit of measurement is foretold for it, which relies on the de Broglie frequency of atoms, the value of which can today be measured with an accuracy of a few parts in 10⁹.     

Condensation of the Roots of Real Random Polynomials on the Real Axis

We introduce a family of real random polynomials of degree n whose coefficients a _k are symmetric independent Gaussian variables with variance , indexed by a real α≥0. We compute exactly the mean number of real roots 〈N _n 〉 for large n. As α is varied, one finds three different phases. First, for 0≤α<1, one finds that . For 1<α<2, there is an intermediate phase where 〈N _n 〉 grows algebraically with a continuously varying exponent, . And finally for α>2, one finds a third phase where 〈N _n 〉∼n. This family of real random polynomials thus exhibits a condensation of their roots on the real line in the sense that, for large n, a finite fraction of their roots 〈N _n 〉/n are real. This condensation occurs via a localization of the real roots around the values , 1≪k≤n.     

Analysis of the Fourier transform infrared spectrum of the stannane species 116SnH4 in the region 1270–1600 cm-1

Monoisotopic stannane 116SnH4 has been investigated at room temperature in the 600–850 cm-1 and 1270–1600 cm-1 regions by FTIR spectroscopy with an effective resolution of 2.1 ×10-3 cm-1 and 2.0 ×10-3 cm-1 respectively. The simultaneous analysis of infrared transitions of both the bending triad and the hot band {bending triad} minus {bending dyad}, enabled us to determine 26 parameters for the (22) band and the combination band (2+4). The standard deviation of the fit was about 1.5×10-3 cm-1. In this analysis, we have used, for the bending triad, a Hamiltonian developed to the fourth order of approximation. 163 observed transitions for the hot band and most observed transitions for the bending triad spectrum, were assigned to the two bands 22 and (2+4), up to J=9. In the fit of the Hamiltonian parameters, we have used for the ground state and for the fundamentals 2 and 4, the parameters determined by Brunet, Pierre, and Bürger [J. Mol. Spectrosc. 140, 237 (1990)].     

Analysis of the high-resolution 5-μm spectra of the ν4(E) and 2ν2(A1) bands of 12CD3F

The infrared spectrum of the ν₄(E) and 2ν₂(A₁) bands of ¹²CD₃F have been recorded and deconvolved to ∼0.005 cm⁻¹ resolution. More than 1890 transitions have been assigned to one of the 37 subbands (−18≤KΔK≤+18) comprising the spectrum of the ν₄ band with a maximum assigned J value of 41. The weak 2ν₂(A₁) band has never been reported in the infrared prior to this work. A total of 358 transitions in K ≤ 8 subbands have been assigned to the 2ν₂ band. The two bands are members of the 24 interacting state complex of ¹²CD₃F spectra in the 5-μm region. The ν₄ and 2ν₂ spectra are highly perturbed, exhibiting local and global resonances. Effective parameters of the two bands were obtained by fitting the data in a restricted manner leaving out the obviously perturbed transitions. The effective parameters, the identification of the different resonances affecting the bands, and estimates of some of the coupling constants are reported.     

Ab initio investigation of tensile strengths of metal(1 1 1)/α-Al2O3(0 0 0 1) interfaces

Ab initio calculations using plane wave pseudopotential method within density funtional theory are applied to investigate mechanical and electronic properties of Al-terminated Me(1 1 1)/Al₂O₃(0 0 0 1) (Me = Al, Ag, Cu, Nb) interfaces. Stress–displacement relationships of separation perpendicular to the interface are calculated. It is shown that obtained results such as work of separation and tensile strength can be understood from electronic structure.     

Exact Solution of the Pseudoharmonic Oscillator in the Space of Constant Positive Curvature

We present analytically the exact solution of the radial Schrödinger equation with the pseudoharmonic oscillator potential in constant positive curvature representation. Exact bound state eigenfunctions and eigenvalues obtained using factorization method. Finally, energy eigenvalues obtained here compared with the results of the theoretical methods in the limit of flat space.     

Magnetic-dichroism study of iron silicides formed at the Fe/Si(100) interface

The interplay between the phase composition, electronic structure, and magnetic properties of the Fe/Si(100)2×1 interface has been studied at the initial stages of its formation (at Fe doses up to 8 Å). The experiments were carried out in ultra high vacuum by using high-resolution photoelectron spectroscopy with synchrotron radiation. The interface magnetic properties were examined in terms of magnetic linear dichroism in angle-resolved Fe 3p core-level photoemission. It was found that at room temperature a disordered Fe–Si solid solution is formed at the first stage of Fe deposition (≤3.4 Å). In the coverage range of 3.4–4.3 Å the solid solution transforms into Fe₃Si. However, the in-plane ferromagnetic ordering of the silicide occurs only at 6.8 Å Fe that demonstrates the thickness dependence of the magnetic properties of Fe₃Si. The subsequent sample annealing to 150°C transforms Fe₃Si to ε-FeSi, leading to the disappearance of ferromagnetic behavior.