Nuclear axial polarizability and the α + α interaction

The 27π-exchange part of the α + α interaction is studied in terms of the response of the α -particle to a static pion field which is related to the static nuclear axial polarizability. We show that the experimental α + α phase shifts for l ? 4 and T_lab ? 50 MeV (that probe the asymptotic tail of the potential) cannot be fitted taking only into account the nucleonic responses of the individual nucleons in the α-particle. This result is interpreted as evidence for an appreciable contribution of the nuclear polarization of the α-particle in the scattering process, nearly twice as large as the nucleonic contribution. The magnitude of this effect, as extracted from the experimental data, is consistent with the theoretical expectations.     

Mechanical properties and the evolution of matrix molecules in PTFE upon irradiation with MeV alpha particles

The morphology, chemical composition, and mechanical properties in the surface region of α-irradiated polytetrafluoroethylene (PTFE) have been examined and compared to unirradiated specimens. Samples were irradiated with 5.5 MeV ⁴He²⁺ ions from a tandem accelerator to doses between 1 × 10⁶ and 5 × 10¹⁰ Rad. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS), using a 20 keV C₆₀⁺ source, was employed to probe chemical changes as a function of α dose. Chemical images and high resolution spectra were collected and analyzed to reveal the effects of α particle radiation on the chemical structure. Residual gas analysis (RGA) was utilized to monitor the evolution of volatile species during vacuum irradiation of the samples. Scanning electron microscopy (SEM) was used to observe the morphological variation of samples with increasing α particle dose, and nanoindentation was engaged to determine the hardness and elastic modulus as a function of α dose.The data show that PTFE nominally retains its innate chemical structure and morphology at α doses <10⁹ Rad. At α doses ≥10⁹ Rad the polymer matrix experiences increased chemical degradation and morphological roughening which are accompanied by increased hardness and declining elasticity. At α doses >10¹⁰ Rad the polymer matrix suffers severe chemical degradation and material loss. Chemical degradation is observed in ToF-SIMS by detection of ions that are indicative of fragmentation, unsaturation, and functionalization of molecules in the PTFE matrix. The mass spectra also expose the subtle trends of crosslinking within the α-irradiated polymer matrix. ToF-SIMS images support the assertion that chemical degradation is the result of α particle irradiation and show morphological roughening of the sample with increased α dose. High resolution SEM images more clearly illustrate the morphological roughening and the mass loss that accompanies high doses of α particles. RGA confirms the supposition that the outcome of chemical degradation in the PTFE matrix with continuing irradiation is evolution of volatile species resulting in morphological roughening and mass loss. Finally, we reveal and discuss relationships between chemical structure and mechanical properties such as hardness and elastic modulus.     

Laboratory Enrichment of Heavy Water by Electrolysis Part II: Effect of Current Density,Cathode Material,and Temperature on the Separation Factor

The different parameters affecting the electrolytic H-D separation factor were investigated. The separation factor α was found to increase with current density and then attains a constant value. With different α increased in the following way: Phosphated iron > iron > stainless steel > nickel. It was found that α decreased as the temperature increased. Applying Arrhenius equation it was possible to calculate the difference in the free energy of activation for proton and deuteron transfer using different cathodes. Excessive reduction in the volume of electrolyte lowered the separation factor. No marked effect on α was observed by changing the type or concentration of electrolyte.     

Effect of temperature on the dislocation structure of the ordered alloy Ni3(Fe,Cr)

Transmission electron microscopy is used to study the dislocation structure of ordered polycrystalline Ni₃(Fe, Cr) alloy after deformation at temperatures of 293, 473, 673, and 773°K. The flow stress σ is plotted as a function of the density of dislocations ρ. It is observed that there is a direct proportionality between σ and ρ^1/2, which indicates that the relation τ= αGbρ^1/2 is satisfied, where τ is the shear stress, G is the shear modulus, b is the Burgers vector, and α is a coefficient weakly dependent on the density of dislocations. The values of α are found for different deformation temperatures from the slope of the lines. It is found that α decreases with increasing deformation temperature. When the temperature is increased from 293 to 773°K the reduction in α is about 20% in agreement with estimates of the resistance to motion by superdislocations caused by nonconservative drag of dislocation jogs.     

Ground state of an infinite two-dimensional system of dipoles on a lattice with arbitrary rhombicity angle

A class of possible periodic orientational configurations of a system of dipole moments located at the sites of an infinite flat rhombic lattice with an arbitrary rhombicity angle α is studied by using the Luttinger and Tisza method. In the framework of the method it is obtained that: for α ⪅ 80° the ground state is ferromagnetic, at α = 60° being continuously degenerate in direction; for 80° ⪅ α ⩽ 90° the ground state is antiferromagnetic, at α = 90° being also continuously degenerate with respect to one parameter. It is shown that the restriction of the interaction range leads to a change in the type of the ground state: at α = 60° this takes place between the third and the fourth coordination spheres and at α = 30° at a distance of about 500 lattice constants. From comparison with known results of numerical experiments on finite systems it is established that the type of the ground state of a finite and an infinite system may be essentially different.     

Effect of the α-F̃1 center interaction on the luminescence lifetime of the F center

The presence of α and F′ centers in a F coloured KCl crystal produces an increase of the lifetime of the luminescence excited with F light. One can exclude that the increase of the luminescence lifetime arises from the contribution of an F′ excited state. The increased lifetime is studied at temperatures lower than 80°K and for some α center concentrations as a function of the initial F center concentration. The results are possibly due to the perturbation of the wavefunction of the F excited state by the α centers present after the F → F′ conversion.     

On the search for time variation in the fine-structure constant: Ab initio calculation of HfF+

A technique based on the relativistic pseudopotential method is proposed to calculate the derivative of the electronic vibrational level energy with respect to the fine-structure constant α for heavy-element compounds. The effect of a small change in α on the frequency of a transition between the vibrational levels of the ground and first excited states of the molecular cation HfF⁺ is calculated. This information is necessary to prepare experiments aimed at determining the time variation in the fine-structure constant.

     

A comment on coherent states of the isotonic oscillator

Landau's theory of density and pair fluctuations in a Fermi liquid is extended to include also fluctuations in the vertex functions, i.e. in the Landau parameters themselves. This is a natural consequence of the higher effective action Г[G, α] which depends explicitly on the full propagator G and the vertex α and whose extreme in G and α determine physical configurations of these quantities.     

A simple model for the quantitative evaluation of the XPS line shape asymmetries in nearly free electron and noble metals

We show that the Born approximation for the scattering by a linearly screened simple model “hole” potential, derived by pseudopotential data, is sufficient to provide an accurate evaluation of the XPS line shape asymmetry parameter α. We get a simple analytical close form expression for α as a function of r_s, which emphasizes the role of electronic screening and evidentiates that α is increasing with increasing r_s.     

Multilayer interference mirrors for the XUV range around 100 eV photon energy

For the first time successful results have been obtained demonstrating interference effects in the reflectance of multilayer films at high photon energies where n = 1 and k is large. Films with 3.5 to 4.5 periods of Au/C and Cu/C were investigated for angles of incidence α = 15° to α = 60° in the wavelength interval 80 to 300A?. The highest near-normal incidence reflectance found was R = 2.7% for Au/C and R = 1.2% for Cu/C at λ ～ 190A?and α = 15°. These values were by a factor of 7 higher than those for a single layered opaque Au film (respectively a factor of 6 for Cu) evaporated under the same conditions. Further improvements appear to be possible. Calculations were performed to guide the investigations and to help the interpretation of the results.     

α SPECTROMETER USING CELLULOSE ACETATE NUCLEAR TRACK DETECTOR MADE IN CHINA

By using the method of etching tracks from the reverse side of a plastic SSNTD, the cellulose acetate SSNTD made in China can be used for α spectrometer. The energy resolution for α particles of 5.31—8.78MeV is in the region of 66—90keV. A formula to obtain the α particle ranges in cellulose acetate SSNTD is given. The α particle ranges in it have been measured and compared with the calculated ranges.     

On the search for time variation in the fine-structure constant: Ab initio calculation of HfF<Superscript>+</Superscript>

A technique based on the relativistic pseudopotential method is proposed to calculate the derivative of the electronic vibrational level energy with respect to the fine-structure constant α for heavy-element compounds. The effect of a small change in α on the frequency of a transition between the vibrational levels of the ground and first excited states of the molecular cation HfF⁺ is calculated. This information is necessary to prepare experiments aimed at determining the time variation in the fine-structure constant.     

On the Physical Meaning of Disperse Parameters of Frequency Dependence of Dielectric Permittivity in the Havriliak–Negami Model

This paper is devoted to an analysis of the frequency dispersion of dielectric permittivity in order to establish the physical meaning of the dispersion parameters α and β in the Havriliak–Negami model. It is found that parameter α is associated with the spectrum broadening of relaxation time τ. Examples with the appearance of a dispersion with parameter α of about 0.4 and 0.7 are presented. A conclusion is drawn that disorder creates a broadening of the relaxation times. Dispersion parameters α and β are introduced to preserve the unified relaxation time. The possibility of the analysis of experimental results on the basis of the Debye model in order to obtain the relaxation time distribution and determine parameters α and β according to the log(τ_HN/τ) chart is shown.     

LiIO3多型性相变的进一步研究

本文用差热分析、恒温热处理、X射线衍射等方法,对LiIO₃在常压的相变过程做了进一步的研究。对于LiIO₃的常压相变机制有了较为详尽的了解。并发现LiIO₃在高温可相对稳定存在三个相:β,η和δ,它们可分别自行熔化,其熔点相应为:432℃,421℃和416℃,从它们的热经历和存在的温度范围,表明其稳定性顺序为β>η>δ。在室温干燥空气中,与α相和β相共存的还有ζ相,ζ相升温放热转变为β相。在α相存在的温区里,ζ相经过长时间热处理并不转变为α相,同时,ζ相转变为β相的温度比α相高。与α→β的情况相同,β对ζ→β也有诱导作用。而且的ζ存在对α→β也有促进作用。θ相(θ₁与θ₂)与γ相一样,是相变过程的中间过渡相。 关键词：     

Relation between the internal stress measured in creep and the stress generated by the dislocation structure in the fcc metals

From the steady-state creep rate data treated as a function of the applied and the measured effective stress and temperature, a phenomenological dependence of the internal stress on the applied stress and temperature was derived. The result determined the expected character of the applied stress- and temperature dependences of the dislocation density, which was considered the microstructure parameter of the internal stress σ _i?=?α MGbρ ^1/2 (σ_i is the internal stress, α the dislocation interaction factor, M the Taylor factor, G the shear modulus, b the Burgers vector length and ρ the dislocation density). A scaling of the expected dislocation density by fitting it to measured dislocation density data yielded reasonable values of the parameter α in the Taylor formula, but the experimental data indicated a weaker applied stress dependence of the measured dislocation density than that of the expected dependence. An admission of an empirical formula fitting the dependence of dislocation density on the applied stress and temperature leads to a suggestion that the parameter α might be dependent on applied stress and temperature.     

On the connectedness structure of the CoulombS-matrix

The forward direction singularity of the non-relativistic CoulombS-matrix is examined and discussed. The relativistic CoulombS-matrix to order α is shown to have a similar singularity.     

Localization in a one-dimensional disordered model

Numerical investigation of a random, one dimensional Kronig-Penny-like model is performed using long chains and large ensembles. Dependence of the inverse localization length α on randomness, irreproducibility of resistance measurements and the dependence of the standard deviation of α on α and the length of the chain were studied. For energies, E=k² close to the zone boundary k=π, we have found α～(π-k).     

Systematic measurement of the D(p, pp)n cross section at KUTL

Systematic measurement of the D(p, pp)n cross section at E _p = 13 MeV at star configurations at various inclined angle α is in progress at Kyushu University tandem accelerator laboratory (KUTL). The measured cross section at space star (α = 90°) is about 12% below the recent pd calculation. The next measurement is being made at 0° < α < 90° to see if the large anomaly of about 25% found by the Köln group (2006) at backward α exists also at forward α.