A study of the optical absorption and the hyperfine constant of the F-centre in alkali halides by means of the multiple scattering Xα method

The F-centre in several alkali halides has been investigated by means of the multiple scattering Xα method. The calculated values of the first absorption peak and the hyperfine splitting constant are compared to experimental results and other theoretical work. It is found that the results agree quite well with experimental values.     

Inequalities of the electron density at the nucleus and radial expectation values of the ground state for the lithium isoelectronic sequence

The electron density at the nucleus, ρ(0), and the radial expectation values, (-2≤n≤10), of the ground state for the lithium isoelectronic sequence are calculated with a full core plus correlation (FCPC) wavefunctions. By using these obtained expectation values, the accurate inequalities of the electron density at the nucleus and the radial expectation values derived by Gálvez and Porras for these systems are examined and verified. The final results show that FCPC wavefunctions used in this work can give satisfactory results in full configuration space.     

Criterion of homogeneous boiling-up of superheated liquids

It is difficult to eliminate the effect of vessel walls and impurities in practical studies of boiling-up of strongly superheated liquids. Therefore, some doubts are always cast upon validity of experiments and their agreement with the classical theory of homogeneous stationary nucleation, impairing the verification of theoretical considerations. This paper reports main results of the theory of homogeneous nucleation and presents formulas for calculating the work of formation of a critical nucleus by an incline of the accessible superheating boundary on isobars and isotherms. Matching of experimental and theoretical values of the work of formation was considered as the homogeneous boiling-up criterion. Calculations by isobars and isotherms were made for some liquids. The theoretical values of the work of formation of a critical nucleus were 1.23–4.5 times higher than the corresponding empirical values for all the liquids, i.e., they were much higher than the calculation error. Thus, boiling-up of the studied liquids was not homogeneous and, hence, it did not correspond to the classical theory of nucleation. The work was financially supported by the President of the Russian Federation (No. NSh-4429.2006.8) and the Russian Foundation for Basic Research (Grant No. 07-08-00575-a).     

CHARGE DISTRIBUTION IN THE 14.7MeV-NEUTRON-INDUCED FISSION OF 232Th: INDEPENDENT YIELDS OF ISOTOPES OF Rh,Ag, In AND Sb

The 12 cumulative yields and 7 independent yields in the symmetric region were determined in the fission of ²³²Th induced by 14.7MeV neutrons with nuclear chemistry techniques. The independent yields of the present work, along with the independent yields obtained in our previous work, were used to calculate the empirical Z_p values on the basis of a Gaussian charge distribution function with a σ of 0.56. A mean value of 0.49±0.25 for ΔZ(=Z_p—Z_UCD) is obtained from all Z_p values in the asymmetric region. Abnormal ΔZ values in the symmetric region seem to suggest that the width of charge distribution for symmetric splits is larger than the value of 0.56. The results show strongly in favor of the Two-Mode-Fission-Hypothesis.     

boldmath Multi-configuration Dirac-Hartree-Fock (MCDHF) calculations for Zn-like sequence from Z=48 to 54

The 4s4p excitation energies and the 4s²-4s4p E1 transitions for zinc-like ions from Z=48 to 54 are calculated by the multi-configuration Dirac-Hartree-Fock (MCDHF) method in this paper. The results for fine-structure energy levels, wavelengths and lifetimes between Z=48 (Cd) and Z=54 (Xe) are presented and compared with other theoretical and experimental results. The calculated values including core-valence correlation are found to be very similar to other theoretical and experimental values. We believe that our calculated values can guide experimentalists in identifying the fine-structure levels in their future work.     

Quantum Fisher Information of Decohered W and GHZ Superposition States with Arbitrary Relative Phase

Quantum Fisher Information (QFI) is a very useful concept for analyzing situations that require phase sensitivity. It become a popular topic especially in Quantum Metrology domain. In this work, we study the changes in quantum Fisher information (QFI) values for one relative arbitrary phased quantum system consisting of a superposition of N Qubits W and GHZ states. In a recent work (Ozaydin et al. Int. J. Theor. Phys. 52, 2977, 2013), QFI values of this mentioned system for N qubits were studied. In this work, we extend this problem for the changes of QFI values in some noisy channels for the studied system. We show the changes in QFI depending on noise parameters. We report interesting results for different type of decoherence channels. We show the general case results for this problem.     

Work function and barrier heights of transition metal silicides

The work function of 13 polycrystalline transition metal suicides was measured by photoemission in uhv. Their values are discussed in relationship to their Schottky barrier heights on n-Si. While there appears to be a weak correlation for a certain group of transition metal suicides, the values of the 5d-noble metal suicides including some of the lattice matched Ni suicides appear to be completely uncorrelated. Experimental values of work functions are compared to the values proposed previously by Freeouf.     

Pitfalls in measuring work function using photoelectron spectroscopy

Accurate measurement of work function is essential in many areas of research and development. Despite the importance of photoelectron spectroscopy as a technique for measuring work function, there has been relatively little discussion in the literature of how to conduct accurate measurements. We review the basic technique of measuring work function using ultraviolet photoelectron spectroscopy and discuss several common sources of error related to the experimental setup. In particular, the sample-detector geometry is found to be a key experimental parameter; accurate results are only obtained when the sample is perpendicular to the electron detector. In addition, we demonstrate that photoelectron work function values correspond to the minimum work function “patch” on a non-uniform surface, in contrast to the average work function measured by other techniques, such as the Kelvin probe method.     

Effect of dielectric coating on the electron work function and the surface stress of a metal

The electron work function, contact potential difference, and surface stress of the elastically deformed faces of the metal covered by a dielectric are calculated by using the Kohn–Sham method and stabilized jellium model. Our calculations demonstrate the opposite deformation dependencies of the work function and contact potential difference. Dielectric coating leads to a negative change in the work function and a positive change in the contact potential difference. It is shown that the measurements of the contact potential difference of a deformed face by the Kelvin method give only the change in the value of the one-electron effective potential in the plane of a virtual image behind the surface, rather than the value of the electron work function. The obtained values of the electron work function and surface stress for Al, Au, Cu, and Zn are in agreement with the results of experiments for polycrystals.     

Relativistic configuration interaction calculations on Kα X-ray satellites of magnesium ions

In this work, the multi-configuration Dirac-Fock (MCDF) and relativistic configuration interaction (RCI) methods have been used to calculate the transition wavelengths, electric dipole transition probabilities, line strengths and absorption oscillator strengths for the Kα X-ray from Mg III to Mg XI. We also take the contributions from the Breit interaction, finite nuclear mass corrections and quantum electrodynamics corrections to the initial and final levels, into account. The present values for Mg X and Mg XI were in good agreement with the previous experimental and theoretical results. The new data in this work provide reference values for the level lifetimes, charge state distributions, and average charge of magnesium plasmas.     

Theoretical fluorescence yields and widths of the K shell and the L subshells,for the Ne,Ar, and Kr isoelectronic sequences

In this work, we present fluorescence yield and width values of Ne-, Ar-, and Kr-like ion levels for selected values of Z, using a state-of-the-art multiconfiguration Dirac–Fock approach. The results may be useful for the interpretation of spectra from plasmas, in both laboratory and astrophysics, as well as from ion collision experiments.     

The influence of O and C doping on the ionization potentials of Li-clusters

The influence of doping of Li-clusters by electronegative O and C atoms on the ionization potentials was investigated. Experimentally, we report ionization potentials for bare Li_n clusters deduced from photoionization efficiency spectra. The values are compared with the results for Li_nO and Li_nC clusters. Observed differences are largely attributed to a quantum size effect caused by the segregated molecular part around the impurity, which changes the electron work function. Theoretically, the Fermi and exchange-correlation energies which enter the work function, are calculated in the frame of the augmented plane wave (APW) method by taking explicitly into account the presence of the molecular core. The other contribution to the work function, the moment of the double layer at the cluster surface, is computed by solving the corresponding Poisson's equation. Received 9 September 1999 and Received in final form 7 February 2000     

Sprinkler irrigation uniformity: Impact on the crop yield and water use efficiency

In this work, an assessment of the effect of distribution uniformity over water use efficiency is shown. The experimental study took place in Sebha region, southern Libya, characterized by arid climate and interested a barley field. The results of water irrigation in the sprinkler irrigation system with respect to the operating pressure (P) and raiser height of sprinkler (H) are reported with respect to distribution uniformity and water use efficiency. The main objective of irrigation is to apply the optimum amount of water to the crop root zone that is needed for its growth and maturation, and it is, hence, important for to check the uniformity of irrigation systems in order to adjust the operating parameters involved. To assess uniformity, the coefficient of uniformity (CU), the low quarter distribution uniformity (DU), and the coefficient of variation (CV) were considered, while the grain yield (GY), the crop height (CH) and the water use efficiency (WUE) weremeasured in order to find the best solution in terms of operating conditions. The highest values reached by the uniformity parameters with varying the operating conditions defined the best operating practices under which the irrigation system works efficiently: the results demonstrated that the maximum values for CU and DU, 91.37% and 0.85, respectively, were obtained at the highest P and H, and under the same conditions, also grain yield, plants height and WUE recorded the highest values: 5.50 t·ha^?1, 63.49 cm and 0.75 kg·m^?3, respectively. The results emerged in this work can be useful for similar arid regions like Sebha region, in order to solve the problems related to water scarcity and water use efficiency.     

Sound insulation of domestic roofing systems: Part 1

The three parts of this paper are to be published in three issues of Applied Acoustics. The present part discusses the experimental facilities of the measuring laboratory and gives details of tests conducted on ceiling specimens. In Part 2 the work on various types of roof component will be presented. In Part 3 will follow the results of tests carried out on the roof and ceiling components combined. It will also consider the ability of the roofing system to provide sound insulation, as a component of the whole building envelope, from typical external noise spectra. The availability of sound insulation values obtained by laboratory measurements does provide the building industry with guidance in building design, even though values for actual buildings may vary considerably from laboratory-measured values.     

Speeding up of internal excitation calculations and application to x‐ray analysis

An improved calculation method is described for the calculation of internally excited x‐rays. The basis of the method is to express the internal excitation term of a point‐like source by three parameters and to store their precalculated values in a look‐up table. The intensities are taken from this table for the actual values of the parameters instead of calculating them repeatedly on the spot. Therefore, the computational work has been reduced significantly. The results of this calculation are compared with those obtained by standard methods and the speed increment was proved. The method was also tested and validated experimentally for several samples. Copyright © 2004 John Wiley & Sons, Ltd.     

Measuring Cu2+-Nitroxide Distances Using Double Electron–Electron Resonance and Saturation Recovery

Distance measurements were obtained between a bound Cu²⁺ and a spin label on two polypeptides of differing length using the double electron–electron resonance (DEER) and saturation recovery experiments. Distance distributions obtained from the DEER results resolved differences between the average distance and distribution of distances for each peptide. An average distance was also obtained for each peptide using the relaxation-based saturation recovery experiment. Predicted average distances for the relaxation-based method, <r_ESR>, were calculated using the distance distributions from the DEER experiment. The predicted <r_ESR> values were similar to those measured by saturation recovery; both were biased to shorter values compared with the DEER results. The breadth of the distance distributions had a significant effect on the average distance measured by saturation recovery. This work highlights the advantage of using DEER to measure metal-nitroxide distances in that the average distances measured are less biased than in relaxation-based techniques.     

Investigation of the resolution ability of an image inversion interferometer

The present paper presents the experimental measurement of the interferometric point spread function of an image inversion interferometer (III). The measurement was realized by scanning a pointlike source in the object plane and integrating the intensity in the image plane for each position of the point source. The achieved results are compared to the theoretical expectations and the results, which we received in a previous work by using a different method. The improved resolution of two neighbouring points in comparison to the conventional image is demonstrated. In addition we propose an explanation concerning the divergences of the values to be expected in theory.     

Experimental study of the efficiency of a SDD X‐ray detector by means of PIXE spectra

The efficiency of a silicon drift detector with ultrathin window was studied for energies between 0.27 and 25 keV. Experimental values of the X‐ray yields from samples of known stoichiometry were obtained by impact of 2 MeV protons. By using theoretical calculations of these yields the relative efficiency of the detector was evaluated. The results are compared with efficiency values obtained from the window transmission and the detector quantum efficiency. A quantitative analysis of a particle induced X‐ray emission spectrum for a reference sample was performed in order to evaluate the consistency of the data presented in this work. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of the spin Hamiltonian constants for electron spin resonance at energy level crossing points

The crossing point of the Cr⁺³ ion energy-levels in single-crystal K₃Co(CN)₆, with the applied magnetic field parallel to the y-axis, is determined experimentally. Precisely calculated values of the constants E and D of the EPR spin Hamiltonian are shown to agree closely with those obtained by other authors.In conclusion, I wish to thank Professor V. S. Grechishkin for supervising my work and discussing the results.     

Energy harvesting in the nonlinear two-masses piezoelastic system driven by harmonic excitations

We examine the energy harvesting system consisted of two different masses (magnets) attached to piezoelastic oscillators, coupled by the electric circuit, and driven by harmonic excitations. The nonlinearity of the system is achieved by variable distance between vibrating magnetic masses and the magnets attached directly to the harvester. We also introduce the mistuning parameter which describes the disproportion of vibrating masses (their ratio). In our work we examine the dependence of output power (in terms of mean squared voltage) generated on electric load on excitation frequencies for different values of mistuning parameter and additionally for different values of system nonlinearity parameter. We compare obtained results with the dia- grams presenting relative displacements of these oscillators (in terms of standard deviation) vs. excitation frequencies. In the second part of this paper we present the phase boundary lines (phase portraits) for selected values of applied frequency to show the complicated behavior of the oscillators in the nonlinear regime when the mistuning appears.