Energy-independent Parameters Research Articles

Updated heat capacities of \(^{161-164}\)Dy nuclei

This work presents the updated heat capacities of \(^{161-164}\)Dy nuclei in the nuclear temperature region from 0 to 1 MeV. The updated heat capacities are obtained within the canonical ensemble method making use of the most recent and recommended experimental nuclear level density (NLD) data together with those calculated within the back-shifted Fermi gas (BSFG) model with energy-dependent parameters. By comparing the updated heat capacities with the un-updated ones, which are obtained by using the old experimental NLD data and the BSFG with energy-independent parameters, we found that the updated and un-updated heat capacities are almost identical at low temperature, but differ from each others at high temperature. This discrepancy can be interpreted by the damping of nuclear shell structure with increasing the excitation energy. Besides, we observe that the S-shape in the updated heat capacities is much more pronounced in even-even Dy isotopes than in even-odd ones, whereas the un-updated heat capacities do not clearly exhibit this S-shape. Therefore, the updated heat capacities should provide a more convincing evidence for the signature of pairing phase transition in nuclear systems.

Spectroscopic ellipsometry for analysis of polycrystalline thin-film photovoltaic devices and prediction of external quantum efficiency

Complete polycrystalline thin-film photovoltaic (PV) devices employing CuIn1−xGaxSe2/CdS and CdS/CdTe heterojunctions have been studied by ex situ spectroscopic ellipsometry (SE). In this study, layer thicknesses have been extracted along with photon energy independent parameters such as compositions that describe the dielectric function spectra ε(E) of the individual layers. For accurate ex situ SE analysis of these PV devices, a database of ε(E) spectra is required for all thin film component materials used in each of the two absorber technologies. When possible, database measurements are performed by applying SE in situ immediately after deposition of the thin film materials and after cooling to room temperature in order to avoid oxidation and surface contamination. Determination of ε(E) from the resulting in situ SE data requires structural information that can be obtained from analysis of SE data acquired in real time during the deposition process. From the results of ex situ analysis of the complete CuIn1−xGaxSe2 (CIGS) and CdTe PV devices, the deduced layer thicknesses in combination with the parameters describing ε(E) can be employed in further studies that simulate the external quantum efficiency (EQE) spectra of the devices. These simulations have been performed here by assuming that all electron-hole pairs generated within the active layers, i.e. layers incorporating a dominant absorber component (either CIGS or CdTe), are separated and collected. The active layers may include not only the bulk absorber but also window and back contact interface layers, and individual current contributions from these layers have been determined in the simulations. In addition, the ex situ SE analysis results enable calculation of the absorbance spectra for the inactive layers and the overall reflectance spectra, which lead to quantification of all optical losses in terms of a current density deficit. Mapping SE can be performed given the high speed of multichannel ellipsometers employing array detection, and the resulting EQE simulation capability has wide applications in predicting large area PV module output. The ultimate goal is an on-line capability that enables prediction of PV sub-cell current output as early as possible in the production process.

A parameterization of nuclear track profiles in CR-39 detector

In this work, the empirical parameterization describing the alpha particles’ track depth in CR-39 detectors is extended to describe longitudinal track profiles against etching time for protons and alpha particles. MATLAB based software is developed for this purpose. The software calculates and plots the depth, diameter, range, residual range, saturation time, and etch rate versus etching time. The software predictions are compared with other experimental data and with results of calculations using the original software, TRACK_TEST, developed for alpha track calculations. The software related to this work is freely downloadable and performs calculations for protons in addition to alpha particles.Program summaryProgram title: CR39Catalog identifier: AENA_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENA_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions:Copyright (c) 2011, Aasim AzoozAll rights reserved.Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met• Redistributions of source code must retain the above copyright, this list of conditions and the following disclaimer.• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distributionThis software is provided by the copyright holders and contributors “as is” and any express or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall the copyright owner or contributors be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage.No. of lines in distributed program, including test data, etc.: 15598No. of bytes in distributed program, including test data, etc.: 3933244Distribution format: tar.gzProgramming language: MATLAB.Computer: Any Desktop or Laptop.Operating system: Windows 1998 or above (with MATLAB R13 or above installed).RAM: 512 Megabytes or higherClassification: 17.5.Nature of problem:A new semispherical parameterization of charged particle tracks in CR-39 SSNTD is carried out in a previous paper. This parameterization is developed here into a MATLAB based software to calculate the track length and track profile for any proton or alpha particle energy or etching time. This software is intended to compete with the TRACK_TEST [1] and TRACK_VISION [2] software currently in use by all people working in the field of SSNTD.Solution method:Based on fitting of experimental results of protons and alpha particles track lengths for various energies and etching times to a new semispherical formula with four free fitting parameters, the best set of energy independent parameters were found. These parameters are introduced into the software and the software is programmed to solve the set of equations to calculate the track depth, track etching rate as a function of both time and residual range for particles of normal and oblique incidence, the track longitudinal profile at both normal and oblique incidence, and the three dimensional track profile at normal incidence.Running time:1–8 s on Pentium (4) 2 GHz CPU, 3 GB of RAM depending on the etching time value

Parameterization of the optical functions of a-Si1−xCx:H: applications to C depth-profiling and surface temperature monitoring in solar cell preparation

We have fitted the dielectric functions of hydrogenated amorphous silicon–carbon alloy (a-Si1−xCx:H) films to a Kramers–Kronig consistent analytical expression. The best-fit photon energy-independent parameters in this expression have been determined as polynomial functions of the carbon content, x (0≤x≤0.23), and measurement temperature, T (50≤T≤200°C). Such databases increase the analytical power of real time spectroscopic ellipsometry for determining x and T with high precision (δx∼±0.01 and δT=±2°C) in studies of a-Si1−xCx:H preparation and processing in solar cell structures.

SIMPLE UNDERSTANDING OF THE ENERGY DEPENDENCE OF THE B/M RATIO AND HADRON MULTIPLICITIES IN e+e− ANNIHILATION

With the help of the color dipole model (CDM) in describing the parton shower process in the perturbative phase in e+e− annihilation, we extend the quark combination model (QCM) of the original form to a more general one in a multiparton system. Then we derive baryon and meson multiplicity formulas for the multiparton system. The new multiplicity formulas are expressed in terms of CDM quantities [Formula: see text] and [Formula: see text]. From these formulas, we can readily understand that the energy behavior of the B/M ratio implied by the multiplicity data in e+e− annihilation is the consequence of two competitive processes: one is the dipole splitting which makes B/M decrease and the other is the increase in combination chain length which makes it higher. To check these basic formulas further, we give multiplicities of most ground hadrons at three energies, 10, 30, 90 GeV, by using five main energy-independent parameters, 75% of which agree with data within 1.5 standard error.

Effective dielectric function modeling of inhomogeneous and anisotropic silver films

The physical properties of vapor deposited films, upon growth at oblique incidence with respect to a substrate, display inhomogeneity and anisotropy. In order to describe the optical properties of such films, it is necessary to model the dielectric response of the film by means of a dielectric tensor using an effective medium theory to obtain its “effective” dielectric function. We have developed a method to model the optical response of such films by considering a three-phase system; air-anisotropic film-substrate. The principal components of the dielectric tensor of the film are obtained by using an Effective Medium Approximation (EMA). We compared our results with spectroellipsometric measurements (pseudo-dielectric function) of silver films deposited at oblique incidence on glass slides obtaining five microstructural energy independent parameters for the films. These results compare adequately with experimental data in the entire interval considered (1.5–5.0 eV).

Selection of fat-equivalent materials in postprocessing dual-energy quantitative CT.

Postprocessing dual-energy QCT is supposed to be able to predict the bone mineral more accurately than single-energy QCT. In addition, the fat content in the vertebral body can be determined. To this aim, some methods include fat-equivalent materials in the calibration device. However, the choice of an appropriate fat-equivalent material is difficult. To solve this selection problem, a method has been developed in which the x-ray interactions of tissue are characterized by three energy-independent parameters. For five different known constituents of anatomical fat, fat-equivalent materials are evaluated. It is shown that it is not possible to find one fat-equivalent material for all anatomical fat compositions. For this reason, the influence of a mismatch between the characterization parameters of anatomical fat compositions and fat-equivalent materials has been evaluated. It is shown that a mismatch in tissue characterization parameters can result in deviations of 10% in the bone mineral content and more than 300% in the estimated fat contents.

Four-quark states in hyperon pair production

We discuss the use of four-quark states as intermediates in the description ofp\(\bar p\) scattering to exclusive hyperon anti-hyperon pairs. We use four energy-independent parameters to account for initial and final state interactions. Some experimentally observed features of these reactions are easily accounted for in this model, but a few features are not well described. We conclude that less crude initial and final state interactions may make the model more useful.

Ion beam etching of GaAs and GaAs/AlGaAs heterostructures probed in real time by spectroscopic ellipsometry

A rotating polarizer, multichannel spectroscopic ellipsometer, operating over the spectral range from 1.5 to 4.0 eV, has been employed for process characterization during etching of GaAs and GaAs/AlGaAs heterostructures. The purpose of this study is to assess the capabilities of this relatively new ellipsometric technique for characterizing III–V semiconductor materials, surfaces, and interfaces during preparation and processing. In this work, each pair of ellipsometric spectra, {Ψ(hν),Δ(hν)} is acquired in 3 s with a repetition period of 16 s. Such spectra are analyzed by well-established linear regression techniques to deduce the time evolution of photon energy independent parameters. In the simplest case of sputter etching with Ar ions, the damage layer thickness, composition, and an estimate of surface temperature of the material can be obtained. For the heterostructures, instantaneous etch rates for both GaAs and AlGaAs can be obtained under identical conditions, and the extent of ion-induced intermixing can be determined as the interfaces are crossed. Future advances are expected in this area through assessment and optimization of technologically important reactive ion etching processes.

A hydrodynamic model for hadron production ine +?e ? annihilation

We consider hadron production ine+-e− annihilation within the framework of a hydrodynamic model. The two key assumptions in the moddel are (i) the initial shape of a Lorentz-contracted disc for the hadronic fireball, with the jet axis providing the necessary longitudinal direction and (ii) the criterion of a critical size of hadronic dimension for the expanding fireball to break up into finalstate particles. Experimental data on charged multiplicity, inclusive distributions, dispersions and particle spectra upto the highest centre-of-mass energy, presently accessible in colliding-beam machines, are explained satisfactorily with only three energy-independent parameters. The present analysis brings out the similarity in the mechanism for hadron production inp-p collision ande+-e− annihilation and attributes the apparent differences to the presence of leading-particle effect in the former process.

Annihilation of e +−e − into hadrons in a hydrodynamic model

A hydrodynamic model with modified boundary conditions is proposed for the two-jet component of e +−e − annihilation into hadrons. Satisfactory agreement with data for charged multiplicity and inclusive distributions of hadrons is obtained with three energy-independent parameters.

Pion Charge Exchange Scattering at High Energies

By a phenomenological choice of the residue functions, a very good fit with experiment for the pion-nucleon charge exchange reaction at Fermilab energies is obtained on a simple Regge-pole model using a quadratic p trajectory and energy-independent parameters.

P-p??n Scattering at Fermilab Energies

By a phenomenological choice of the residue function, a very good fit with experiment is obtained on a simple Regge pole model using a linear A2 trajectory and energy-independent parameters.

Off-Energy-Shell Effects in the Triton with the Boundary-Condition Interaction

The boundary-condition model of the two-nucleon interaction due to Feshbach and Lomon is used without an external potential tail to determine the ground-state properties of the three-nucleon system for the purpose of studying the off-energy-shell properties of the two-body $T$ matrix. Calculations are performed using an average singlet-triplet $s$-wave interaction giving a completely symmetric triton wave function. The $T$ matrix is separable and depends on three energy-independent parameters \char22{} the boundary radius ${r}_{0}$ and the boundary condition $f$ at ${r}_{0}+\ensuremath{\epsilon}$ which are determined from the two-nucleon phase shifts, and the boundary condition $b$ at ${r}_{0}\ensuremath{-}\ensuremath{\epsilon}$ which is specifically an off-shell parameter that does not appear in the on-shell $T$ matrix. With $f=0.11$ and ${r}_{0}=0.95$ F, the Faddeev equations are solved for the triton energy eigenvalues and spectator functions for several values of $b$. It is found that the binding energy varies from 3.9 to 19.4 MeV for $b$ between 0.5 and 0.6, with a value of 8.5 MeV at $r=0.537$. The average kinetic energy and charge form factor are determined as a function of $b$, and qualitative agreement of the charge radius with experiment is obtained for $b=0.5\ensuremath{-}0.6$. The charge form factor, compared with experiment, does not drop off rapidly enough with ${q}^{2}$, indicating the presence of relatively too much large $q$ component in the spectator functions. The changes to be expected from the inclusion of tensor coupling in the boundary parameters are discussed.

Pion-Nucleon Scattering Amplitudes in the Range 300-700 MeV

The cross section for the scattering of ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ by nucleons in the energy range 300-700 MeV has been analyzed in terms of energy-independent parameters. The parameterization is based on a dispersion relation satisfied by the partial-wave amplitudes, by replacing the left cut by a superposition of poles and the inelasticity function ${R}_{l}=\frac{{\ensuremath{\sigma}}_{l}(\mathrm{tot})}{{\ensuremath{\sigma}}_{l}(\mathrm{el})}$ by a ratio of polynomials in the momentum. Detailed results are presented for the real and imaginary parts of the phase shifts with $l<~3$. The structure of the "second resonance" is more complicated than has heretofore been thought, ${p}_{11}$, ${s}_{11}$, and ${d}_{13}$ waves all playing an important part. The width of the ${d}_{13}$ resonance is found to be considerably smaller than previous values from total cross-section measurements. The role of the (possibly resonant) amplitudes ${p}_{11}$ and ${s}_{11}$ is discussed.

The resonance absorption integral of 238U

The resonance absorption integral of infinitely diluted 238U is calculated between the first resolved level (6·7 eV) and I MeV. The energy-independent parameters Γ n 0/ D and Γ γ / Γ n 0 of the average absorption cross-section are determined from the region of resolved resonances and the nuclear model theories, The effect of l > 0 neutrons is shown to be small but significant. The total value of 277 ± 10 per cent barns is in good agreement with experiment.

Comparison of D–T and D– 3 He at low energies

A thin gas target was used to measure the absolute cross-section and angular distribution of α -particles from the two ‘ mirror ’ reactions D– 3 H and D– 3 He for deuteron energies below 45 keV. The reactions were found to be isotropic and the variations of the total cross-sections over the energy range 20 to 45 keV can be expressed by the simple Gamow theory of penetration of the coulomb barrier. The simple theory assuming the same energy-independent nuclear parameters for the mirror nuclei 3 H and 3 He was unable to account for the observed cross-sections of these two reactions.