Wilson fermions on the lattice—A study of the eigenvalue spectrum

We have studied the eigenvalues of the Wilson fermion matrix on various lattice sizes and for a range of coupling constants, β, in the quenched approximation. The implications for the phase structure of lattice QCD in the presence of Wilson fermions are discussed.     

Diode laser measurements of line strengths and collisional half-widths in the ν1 band of OCS at 298 and 200K

Absolute line strengths and self-broadened half-widths have been measured at 298 and 200 K for spectral lines ranging from J = 1 to 55 in the ν₁ band (860 cm^-1) of ¹⁶O¹²C³²S, using a tunable diode laser spectrometer. The vibrational transition moment (6.412 ± 0.16 × 10^-2D) as well as the absolute intensity (29.63±1.48 cm^-2-atm^-1 at 298 K), of the ν₁ band are determined from these line-strenght measurements. By applying two semi-classical impact theories of collisional broadening, we have obtained results for half-widths at 298 and 200 K which are significantly larger than the experimental data for |m|<50. However, the variation of the linewidths with temperature is well reproduced theoretically.     

North-South asymmetry of some solar parameters: A study based on the dominance of hemispheric sunspot activity during the solar cycles 18–24

Solar activity indices differ over the solar disk, and different activity parameters are not considered to be symmetric between the northern and southern solar hemispheres. In the present paper, the daily data of a set of solar parameters (solar radio flux F10.7, total solar irradiance TSI, plage area PA, coronal index CI, solar flare index SFI, and solar mean magnetic field ǀBǀ) as well as the daily hemispheric sunspot areas (SSAs) and sunspot numbers (SSNs) during a timeframe 1945–2017 (covering almost the last seven solar cycles, 18 ̶ 24) have been employed to investigate the north-south (N-S) asymmetry of the considered solar parameters based on the dominance of hemispheric distributions of SSAs and SSNs. The N-S asymmetry for each solar parameter has been investigated and the results revealed that it is a significant aspect through different years in the entire period. The grand average of each solar parameter for the northern and southern groups over each solar activity cycle has been calculated to investigate the statistical significance of N-S asymmetry of each solar parameter in each solar activity cycle. The solar cycles 19 and 24 displayed the dominance of the southern F10.7 and PA over the northern one. However, the solar cycle 23 showed the reverse. The grand average of CI displayed the southern preference in the solar cycle 19 while, the northern dominance of CI is revealed for the solar cycle 23. The grand averages of CI demonstrated nearly symmetric distribution in solar cycles 18, and 20–22. The N-S asymmetry of the grand averages of SFI exhibited a southern dominance during solar cycles 21 and 24. On the other hand, the northern preference is observed for the grand average of SFI through the solar cycle 23. The asymmetry of the grand averages of ǀBǀ obviously has the same dominance (sign) of hemispheric sunspot activity indices for the solar cycles 21–24. The periodic behavior of the N-S asymmetry of SSAs, SSNs, F10.7, and ǀBǀ has been investigated using Fast Fourier Transformation. Many mid- and long term periodicities have been detected. We present our results and discuss their possible explanations.     

A study of the influence of surface layers’ disordering on the spectrum of energy losses of electrons passed through copper thin single crystal films

Results of the experimental investigation of energy losses of electron passed through thin films Cu (100) with a thickness of d ≈ 420 ? at E _p = 3 keV are presented. It is revealed that the surface plasmon peak disappears at a primary electron energy of ≥6 keV. For the first time, the degree of surface amorphization and area of the disordered layer are estimated by the change of elastic peak intensity during the passage of electrons through thin films of Cu (100). There is an additional energy loss of electrons peak caused by bulk plasmon, its intensity depending on the irradiation dose under ionic bombardment.     

Projected-wave-function study of the spin-1/2 Heisenberg model on the Kagomé lattice

We perform a Gutzwiller projected-wave-function study for the spin-1/2 Heisenberg model on the Kagomé lattice to compare energies of several spin-liquid states. The result indicates that a U(1)-Dirac spin-liquid state has the lowest energy. Furthermore, even without variational parameters, the energy turns out to be very close to that found by exact diagonalization. We show that such a U(1)-Dirac state represents a quantum phase whose low-energy physics is governed by four flavors of two-component Dirac fermions coupled to a U(1) gauge field. These results are discussed in the context of recent experiments on ZnCu(3)(OH)(6)Cl(2).     

Temperature effects on the width,shift and asymmetry of 748.8 nm self-broadened neon line

The influence of temperature on the shape of the self-broadened 748.8 nm Ne line emitted from the low pressure glow discharge of neon was investigated with a Fabry-Perot interferometer. Detailed analysis showed departures of the registered line shapes from the ordinary Voigt profile. These departures were consistent with fits of the speed-dependent asymmetric Voigt profile to experimental profiles. The values of the pressure broadening, shifting and collision-time asymmetry were determined and compared with those calculated in the adiabatic approximation for the van der Waals and Lennard-Jones potentials.     

Experimental and theoretical study of N2-broadened acetylene line parameters in the ν1 + ν3 band over a range of temperatures

N₂-broadened line widths and N₂-pressure induced line shifts have been measured for transitions in the ν₁?+?ν₃ band of acetylene at seven temperatures in the range 213–333?K to obtain the temperature dependences of broadening and shift coefficients. For the room-temperature spectra the line mixing effects have been also investigated. The Voigt and hard-collision line profile models were used to retrieve the line parameters. All spectra were recorded using a 3-channel tuneable diode laser spectrometer. The line-broadening and line-shifting coefficients as well as their temperature-dependence parameters have been also evaluated theoretically, in the frame of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole–quadrupole and pairwise atom–atom interactions as well as on exact trajectories driven by an effective isotropic potential.     

Sterical effects of encapsulation on some cobalt complexes built up in zeolite Y – A Mössbauer emission spectroscopy study

Mössbauer emission spectroscopy revealed effects of encapsulation on 2,2′-bipyridine and 1,10-phenantroline complexes of ⁵⁷Co²⁺ synthesized in the supercages of zeolite Y. The tris coordinated phenantroline complex, unexpectedly, did not form in the supercage due to the blocking effect of the cage walls. The spectra of the tris bipyridine complex did not show the high spin state of the nucleogenic iron(II) complex. This is attributed to the very short lifetime of this state destabilized by the misfit to the volume of the zeolite cage. The relaxation rate was estimated and compared with lifetimes measured on the complex embedded in other matrices.     

Experimental and theoretical study of long counters on the departure of “point” assumption and scattering background influence

A new long counter has been constructed and calibrated with the inherent efficiency of 11.5 cm² in the 2.5 MeV neutron field, and a relative flat energy response of 20% disparity within 0.5 MeV–15 MeV. Using this detector and another commercial DePangher counter, the departure of “point” assumption at near distance and the scattering background influence are investigated by performing three groups of experiments in low, middle and high scattering room. Simulation studies are also performed to supplement the experimental data.Two conclusions are deduced. First, the direct efficiency η is very sensitive when the source is very near, and the departure of point assumption is very evident at this situation. So, a revising method is tried to put forward, employing the on-site calibration with a known neutron source and theoretical calculated coefficient D = (η/ε)/(η_cf252/ε_cf252). And second, scattering backing counts are found mainly from the nearest wall or scatterers. However, the relatively uniform isotropic scattered neutrons contribute insensitive to the source-detector distance, which means the background tally can be eliminated by some simple ways.     

A study of the influence of chemical environment on the Li (i = 1–3) subshell X-ray intensity ratios and the L3 absorption-edge energy for some compounds of 66Dy using synchrotron radiation

In the present work, the X-ray intensity ratios, I_Lk/I_Lα (k = l, β, γ_1,5, γ₂,₃, γ₄), have been measured for different compounds of ₆₆Dy, namely, Dy₂O₃, Dy₂(CO₃)₃, Dy₂(SO₄)₃.8H₂O, DyI₂, and the ₆₆Dy metallic foil by tuning the incident photon energies across its L_i (i = 1–3) absorption-edge energies covering the region 7.8–10 keV in order to investigate the influence of chemical effects on these intensity ratios in the presence of the many-body effects, which become significant at photon energies in proximity to the L_i absorption-edge energies. The present measured intensity ratios I_Lk/I_Lα have been compared with two sets of values calculated using the nonrelativistic Hartree–Fock–Slater model-based L_i (i = 1–3) subshell photoionization cross sections, the Dirac–Fock model-based X-ray emission rates, and two sets of the fluorescence and Coster–Kronig yields. The L₃ absorption-edge energy of ₆₆Dy in its different compounds and metallic foil has been deduced from the XANES spectra recorded in the present work. The L₃ absorption-edge energy shifts obtained from these absorption-edge energies are found to increase linearly with the partial charge on the metal atom (₆₆Dy).     

Effect of Coulomb repulsion on spin and orbital magnetism of cobalt–benzene complex: A relativistic density functional study

We have demonstrated electronic configurations and magnetic properties of single Co adatom on benzene (Bz) molecule in the framework of relativistic density functional theory. A sequence of fixed spin moment (FSM) calculations were carried out with and without Coulomb repulsion (U). We have investigated that varying the strength of Coulomb repulsion results to different equilibrium positions for the Co adatom on benzene molecule. It was shown that inclusion of the on-site Coulomb repulsion in the Co 3d orbitals affects significantly the geometry of Co–Bz complex. We also found two stable low-spin and high-spin multiplicities for the complex. The nature of the high-spin configuration was explained according to the Hubbard electron–electron correlation in 3d shell of the Co adatom. Our FSM results indicate that the high-spin state is a global minimum in the presence of Hubbard parameter U. The relativistic spin–orbit coupling and using orbital polarization correction induce considerable orbital magnetism in both low and high spin states of the Co–Bz complex. We have also calculated magnetic anisotropy energies for two spin states and we found out that an out-of-plane magnetic orientation of Co adatom is more favorable in the low spin state whereas the Coulomb repulsion (U = 2 eV and U = 4 eV) predicts an in-plane magnetic orientation for Co adatom. Our findings can be implicitly taken into account for the extended system of added single Co atom on graphene.     

Doping influence on Sm1 − x Th x OFeAs superconducting properties: Observation of the effect of intrinsic multiple Andreev reflections and determination of the superconducting parameters

We studied SNS and S-N-S-N-...-S contacts (where S is a superconductor and N is a normal metal) formed by “break-junction” technique in polycrystalline Sm_{1 ? x} Th _x OFeAs superconductor samples with critical temperatures T _C = 34–45 K. In such contacts (intrinsic) multiple Andreev reflections effects were observed. Using spectroscopies based on these effects, we detected two independent bulk order parameters and determined their magnitudes. Theoretical analysis of the large and the small gap temperature dependences revealed superconducting properties of Sm_{1 ? x} Th _x OFeAs to be driven by intraband coupling, and $\sqrt {V_{11} V_{22} } /V_{12} \approx 14$ (where V _ij are the electron-boson interaction matrix elements), whereas the ratio between density of states for the bands with the small and the large gap, N ₂/N ₁, correspondingly, was roughly of an order. We estimated “solo” BCS-ratio values in a hypothetic case of zero interband coupling (V _{i ≠ j} = 0) for each condensate as 2Δ_{L, S}/k _B T _C ^L,S ≤ 4.5. The values are constant within the range of critical temperatures studied, and correspond to a case of strong intraband electron-phonon coupling.     

A study on the best irradiation dose of X-ray for Hep-2 cells by Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) was employed to study the human epidermis larynx car- cinoma cell lines (Hep-2) which were irradiated by different doses of X-ray.The results show that (1) the irradiation of X-ray damages the structure of the CH_3 groups of the thymine in DNA,which restrains the reproduction of Hep-2 cells effectively,(2) the 8 Gy dose of X-ray irradiation changes the framework and the relative contents of some proteins,lipids and the nucleic acid molecules intercellular in the greatest degree,and (3) the 8 Gy dose of X-ray irradiation is the best irradiation dose for lowering the degree of the cancerization of Hep-2 cells according to the criteria for the degree of the cancerization reported recently.Meanwhile,the apoptosis of these cells were detected by using flow cytometry (FCM) primarily. It shows that the apoptotic ratio of the Hep-2 cells depends on the irradiation dose to some extent,but is not linearly.And the apoptotic ratio of the 12 Gy dose group is the maximum (20.36%),but the apoptotic ratios of the 2 to 8 Gy dose groups change little.     

A pre-Columbian copper alloy smelting furnace: Mössbauer and XRD study of the firing conditions

Samples from a pre-Columbian furnace used for copper alloy smelting on the Pampa de Chaparrí in northern Peru during the Middle to Late Sicán Period (AD 900–1375) were studied by Mössbauer spectroscopy, X-ray diffraction and X-ray fluorescence. The data thus obtained allow conclusions as to the temperatures and oxidation-reduction conditions prevaling at different positions inside the furnace during the smelting process.     

Determination of Chemical Effect on the Kβ1/Kα, Kβ2/Kα, Kβ2/Kβ1 and Kβ/Kα X-Ray Intensity Ratios of 4d Transition Metals

It is clear that detailed studies performed under identical experimental conditions are desirable to determine the effect of the chemical environment on the value of intensity ratios. To better understand this effect, we conducted measurements on Kβ₁/Kα, Kβ₂/Kα, Kβ₂/Kβ₁ and Kβ/Kα x-ray intensity ratios. The Kα and Kβ_1,2 emission spectra for compounds of 4d transition metals Y, Zr, Nb, and Mo were measured using a Si(Li) solid-state detector. The samples were excited by 22.69 keV x-rays emitted from a ¹⁰⁹Cd radioisotopes source. The experimental results for pure elements are compared with the other experimental and theoretical values.     

Rotational analysis and line intensities of the HCO B^2A＇-X^2A＇31^1 band at 296 K

This paper computes the rotational energy levels of the HCO B^2A＇-X^2A＇31^1 transition, especially, the higher values of the rotational quantum numbers NKa Kc and Ka, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration-rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO.     

Tautomerization and solvent effects on the absorption and emission properties of the Schiff base N,N′-bis(salicylidene)-p-phenylenediamine – A TDDFT study

Time-dependent density functional theory combined with a polarized continuum model has been applied to study solvent effects on the geometrical and energetic properties, as well as the absorption and emission properties, of three tautomeric forms of N,N′-bis(salicylidene)-p-phenylenediamine (BSP). The calculated properties are in agreement with the available experimental data. It was observed that the solvent environment does not affect the vertical excitation energies significantly, whereas tautomerization strongly affects both the absorption and emission spectra of BSP.     

Multispectrum measurements of spectral line parameters including temperature dependences of N2- and self-broadened half-width coefficients in the region of the ν9 band of 12C2H6

Ethane is a prominent contributor to the spectrum of Titan, particularly in the ν₉ region centered near 822 cm^?1. To improve the spectroscopic line parameters at 12 μm, 41 high-resolution (0.0016–0.005 cm^?1) absorption spectra of C₂H₆ were obtained at sample temperatures between 211 and 298 K with the Bruker IFS 120HR at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington. Two additional spectra were later recorded at ～150 K using a new temperature-stabilized cryogenic cell designed for the sample compartment of the Bruker IFS 125HR at the Jet Propulsion Laboratory (JPL) in Pasadena, California. A multispectrum nonlinear least-squares fitting program was applied simultaneously to all 43 spectra to measure the line positions, intensities, N₂- and self-broadened half-width coefficients and their temperature dependences. Reliable pressure-induced shift coefficients could not be obtained, however, because of the high congestion of spectral lines (due to torsional-split components, hot-band transitions as well as blends). Existing theoretical modeling of this very complicated ν₉ region permitted effective control of the multispectrum fitting technique; some constraints were applied using predicted intensity ratios, doublet separations, half-width coefficients and their temperature dependence exponents in order to determine reliable parameters for each of the two torsional-split components. For ¹²C₂H₆, the resulting retrievals included 17 ^pQ and ^rQ sub-bands of ν₉ (as well as some ^pP, ^rR sub-bands). Positions and intensities were measured for 3771 transitions, and a puzzling difference between previously measured ν₉ intensities was clarified. In addition, line positions and intensities were obtained for two ¹²C₂H₆ hot bands (ν₉+ν₄?ν₄, ν₉+2ν₄?2ν₄) and the ν₉ band of ¹³C¹²CH₆, as well as several hundred presently unidentified transitions. N₂- and self-broadened half-width coefficients were determined for over 1700 transitions, along with 1350 corresponding temperature dependence exponents. Similar to N₂- and self-broadened half-width coefficients, their temperature dependence exponents were also found to follow distinctively different patterns. However, while the self- and N₂-broaded widths differed by 40%, the temperature dependence exponents of the two broadening gases were similar. The variations of the observed half-width coefficients and their temperature dependences with respect to J, K quantum numbers were modeled with a set of linear equations for each K. The present broadening coefficients compared well with some of the prior measurements.