Band-mapping of InP (100) along the ΓX-line

We have prepared InP (100) surfaces from wafer-material by cycles of argon ion sputtering and gentle annealing. From these samples normal-emission photoelectron spectra were recorded using photons in the energy range 10eV<h<75eV. From the results we derive the initial-state band disperison along the X-line of the 3-dimensional Brillouin zone. Our results are fully consistent with initial-state bands mapped by other authors along the KX-line. From the good agreement we conclude that the quality of the (100)-surfaces as used in our work is at least adequate for bulk band investigations.     

Combined theoretical and experimental determination of the atomic structure and adsorption site of Na on the Si(100)2 × 1 surface

The Na/Si(100)2 × 1 interface is studied by both ab initio local density functional total energy DMol molecular calculations using very large cluster models and photoemission EXAFS which provides the unique feature of probing both Na adsorbate and Si substrate environments. Theoretical and experimental bond lengths are found to be in very good agreement and enable a definite assignment of the adsorption site: Na is adsorbed on a single site, the cave, with no Na-Na distance consistent with any “double layer” models. The growth and existence of a second Na layer are shown to occur only in presence of very low level impurities.     

Interpretation of Z_b(10610)and Z_b(10650)in the ISPE mechanism and the Charmonium Counterpart~

The initial single pion emission(ISPE) mechanism is applied to the processes γ(55)→πB~((*))B~((*)),whose details have been recently reported at ICHEP2012,and we obtain reasonable agreement with Bell's measurements;that is,we succeed in reproducing the enhancement structures of Zb(10610) and Zb(10650).Inspired by this success,we also predict the corresponding enhancement structures in open charm one-pion decays of higher charmonia near the thresholds of D*D and D*D*.     

Adsorption and organisation of para-hexaphenyl molecules on Si(100)

Para-hexaphenyl molecules (p-6P: C₃₆H₂₆) can be grown as nanofibres on various surfaces having optical properties of technological relevance. We report here the first observations of the initial stages of adsorption of individual p-6P molecules on Si(100)-(2×1) using room temperature Scanning Tunnelling Microscopy (STM). Depending on the substrate temperature, the hexaphenyl molecules adsorb in two configurations; indicating both weak and strong chemisorption. All six phenyl rings are clearly visible and the molecules are found to adsorb with characteristic angles between the long axis of the molecule and the silicon dimer rows. A statistical analysis of the spatial distribution of the molecules suggests that the clustering required for crystallographic nanofibre growth does not occur at the atomic scale under the experimental conditions used here.     

Renormalization group equation and QCD coupling constant in?the?presence of?SU(3) chromo-electric field

We solve the renormalization group equation in QCD in the presence of a SU(3) constant chromo-electric field E ^a with arbitrary color index a=1,2,…,8 and find that the QCD coupling constant α _s depends on two independent Casimir/gauge invariants C ₁=[E ^a E ^a ] and C ₂=[d _abc E ^a E ^b E ^c ]² instead of one gauge invariant C ₁=[E ^a E ^a ]. The β function is derived from the one-loop effective action. This coupling constant may be useful to study hadron formation from color flux tubes/strings at high energy colliders and to study quark–gluon plasma formation at RHIC and LHC.     

Calculation of vibrations of the H-bonds and electrooptical parameters of the F(HF)2]− complex

The problem of calculating the vibrations of the F(HF)₂]^? complex with hydrogen bonds is considered with allowance for the anharmonicity and interaction of motions in different degrees of freedom. A systematic solution of this problem is proposed which consists in separating the total vibrational system into subsystems, obtaining sufficiently exact vibrational wave functions of subsystems, and expanding the vibrational wave functions of the total system in basis functions constructed from the wave functions of subsystems. At the first stage of our study, the stretching and bending modes of two F...HF hydrogen bonds are considered with the use of an exact kinetic energy operator and a nonempirical three-dimensional potential energy surface. It is shown that these vibrational modes of the complex are characterized by significant mechanical and electric anharmonicities. The calculated values of frequencies of the symmetric and antisymmetric vibrations of hydrogen bonds are in good agreement with the experimental findings.     

Effect of the mesons σ* and Φ and the variety of U(N)Σ on the transition density of hyperon stars

The effect of the mesons σ* and φ and the variety of U(N)Σ on the transition density of hyperon stars is examined within the framework of relativistic mean field theory for the baryon octet {n,p,∧,∑-,∑0,∑+,Ξ- and Ξ0} system.It is found that,compared with that without considering the mesons δ* and φ,the transition density of hyperon stars decreases,the critical baryon density that hyperons Σ-,Σ0,Ξ+,Ξ- and Ξ0 appears to decrease too,but for A the effect is not obvious.As U(N)Σ goes up,the critical baryon density of Σ+,Σ0 and Σ- increases,that of Ξ0 decreases and that of A and Ξ- is fixed.In addition,it is found that the variety of U(N)Σ almost does not influence the transition density.     

ββ(2ν) decay of 100Mo to the first excited 0+ state of 100Ru

The rate of the double-beta ββ(2ν) decay of ¹⁰⁰Mo to the first 0⁺ excited state in ¹⁰⁰Ru is measured by a γγ-coincidence technique in which two HPGe detectors are used to detect the two γ rays (E _γ1=590.76 keV and E _γ2=539.53 keV) from the daughter nucleus ¹⁰⁰Ru as it deexcites to the ground state via the transition sequence 0⁺ → 2⁺ → 0⁺. In contrast to all previous ββ-decay experiments, this technique provides data that are essentially background-free. By using a 1.05-kg isotopically enriched (98.4%) disk of ¹⁰⁰Mo, 22 coincidence events (with the background estimated at 2.5 events) are detected in 440 d of measuring time, which translates into a half-life time of [5.9 _?1.1 ^+1.7 (stat.)±0.6(syst.)]×10²⁰ yr.     

Oxidation of Si(100)2x1 and Gex Si1−x (100)2x1

High resolution electron energy loss Spectroscopy (HREELS), X-ray photoelectron Spectroscopy (XPS) and low energy electron diffraction (LEED) have been used to characterize initial stages of oxidation of Si(100)2x1 and Ge_x Si_1−x (100)2x1 surfaces. Different oxidation stages of Si were identified by measuring Si 2p core level shifts and characteristic vibrations of Si-O-Si complexes. The latter may be described in the framework of continuous random network models.Then,from the experimentally determined frequencies, force constants,average bond angles and bond lengths are determined. Complementary,marker experiments with atomic hydrogen as a probe in conjunction with HREELS were used to determine the local, atomic structure for different stages of oxidation from chemical shifts of Si-H and Ge-H stretching mode intensities, respectively.     

Relaxation of the analyzing power of the (p, τX) and (p, αX) reactions in the continuum

The observed continuous decrease of the analyzing power for the reactions ($\text{p}$, τX) and ($\text{p}$, αX) on ⁹⁰Zr and ²⁰⁹Bi at E_p = 72 MeV as a function of the excitation energy of the final nucleus is described by a phenomenological relaxation process.     

Structural, thermal, and electrical properties of (100?x) ZrO2 (x) Bi2O3 compound

Composition (100?x) ZrO₂ (x) Bi₂O₃ (x?=?15, 20, 25) is synthesized by solid-state reaction method to study the effect of Bi₂O₃ doping on ZrO₂. The as-prepared samples are characterized by various methods. The X-ray diffraction pattern of all these samples exhibits three phases, namely, m-ZrO₂, ??_III-Bi₂O₃, and ??-Bi₂O₃. The differential thermal analysis curves do not show any phase transition/decomposition, which clearly indicated the stabilization of ??-Bi₂O₃ phase. The conductivity changes in all the samples are discussed in terms of different phase formations and their volume fractions. The microstructural and energy dispersive analyses indicate the presence of different phases. A maximum conductivity at high temperature (800?°C) was observed for the x?=?25 composition, i.e., ???=?4.21?×?10^?2 S/cm.     

Design and assembly of the CsI(Tl) crystal module of the BESⅢ electro-magnetic calorimeter

The CsI(Tl) crystal modules of the Beijing Spectrometer Ⅲ (BESⅢ) electro-magnetic calorimeter (EMC) were designed and assembled through Monte Carlo simulation and experiments. After the assembly was finished, the performance of each crystal module was tested by cosmic rays. All crystal modules were found to work well before the installation of EMC.     

A Comparative Study of the Growth of Cr on (110)TiO2 Rutile, (0001) α-Al2O3 and (100)SrTiO3 Surfaces

Thin Cr films were deposited on single crystal -Al₂O₃, SrTiO₃ and TiO₂ (rutile) substrates under ultrahigh vacuum conditions using molecular beam epitaxy (MBE). The growth behavior and thermal stability of the films were investigated with scanning tunneling microscopy (STM), X-ray phototelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and transmission electron microscopy (TEM). Cr grew as 3D clusters on all substrates. For all three Cr/oxide systems a strong temperature dependent interfacial reaction was observed. The results suggested that these reactions depended greatly on thermodynamics and on transport properties in the oxide substrates.     

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.     

Design and assembly of the CsI(Tl) crystal module of the BESⅢ electro-magnetic calorimeter

The CsI(Tl) crystal modules of the Beijing Spectrometer Ⅲ (BESⅢ) electro-magnetic calorimeter (EMC) were designed and assembled through Monte Carlo simulation and experiments. After the assembly was finished, the performance of each crystal module was tested by cosmic rays. All crystal modules were found to work well before the installation of EMC.

     

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.     

Shape Invariant and Rodrigues Solution of?the?Dirac-shifted Oscillator and?Dirac-Morse Potentials

We show that the Dirac equation for a charged spinor in spherically symmetric electromagnetic potentials as Dirac-shifted oscillator and Dirac-Morse potentials have the conditions of shape invariant symmetry in non-relativistic quantum mechanics. The relativistic spectra of the bound states and spinor wavefunctions can be obtained by the Rodrigues polynomials of one associated differential equation.     

Similarities in the decomposition and dehydrogenation of cyclohexene on (4 × 4)-CMo(110) and Pt(111)

The decomposition and dehydrogenation of cyclohexene have been used as probing reactions to directly compare the surface reactivities of carbon-modified Mo(110) and Pt(111). By using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS), we find that the dominant decomposition pathway of cyclohexene can be converted from complete decomposition to atomic carbon and hydrogen on clean Mo(110) to partial dehydrogenation to benzene and hydrogen on (4 × 4)-CMo(110). The latter reaction mechanism is very similar to that observed on Pt(111). Furthermore, in contrast to the near identical catalytic properties that are commonly observed for bulk molybdenum carbide and nitride powder materials, we find that the reactivities of carbon-modified and nitrogen-modified Mo(110) surfaces are qualitatively different.     

Supersymmetry and the cohomology of (hyper) Kähler manifolds

The cohomology of a compact Kahler (hyperKähler) manifold admits the action of the Lie algebra so(2,1) (so(4,1)). In this paper we show, following an idea of Witten, how this action follows from supersymmetry, in particular from the symmetries of certain supersymmetric sigma models. In addition, many of the fundamental identities in Hodge-Lefschetz theory are also naturally derived from supersymmetry.