Canadian Journal of Physics

In this study, it was aimed to prepare a series of PVdF-co-HFP based electrolytes with different LiClO₄ loadings and to investigate their chemical and electrical properties in detail. For this purpose, PVdF-co-HFP based electrolytes with different LiClO₄ loadings (1–20 weight %) were prepared using solution casting method. X-ray diffraction (XRD), differential scanning calorimetry, and thermogravimetric (TGA) –differential thermal and dielectric spectroscopy analysis of PVdF-co-HFP/LiClO₄ were performed to characterize their structural, thermal, and dielectric properties, respectively. XRD results showed that the diffraction peaks of PVdF-co-HFP/LiClO₄ electrolytes broadened and decreased with LiClO₄. TGA patterns exhibited that PVdF-co-HFP/LiClO₄ electrolytes with 20 wt % of LiClO₄ had the lowest thermal stability and it degraded above 473 K, which is highly applicable for solid polymer electrolytes. Dielectric constant, dielectric loss, and conductivities were calculated by measuring capacitance and dielectric loss factor of PVdF-co-HFP/LiClO₄ in the range from 10 mHz to 20 MHz frequencies at room temperature. In consequence, conductivities of PVdF-co-HFP/LiClO₄ increased significantly with frequency for low loading of LiClO₄ while they only slightly changed with higher LiClO₄ addition. On the other hand, dielectric constant values of PVdF-co-HFP/LiClO₄ films decreased with frequency whereas they rose with LiClO₄ addition. The dielectric studies showed an increase in dielectric constant and dielectric loss with decreasing frequency. This result was attributed to high contribution of charge accumulation at the electrode–electrolyte interface. The electrolyte showed the maximum conductivity of 8 × 10⁻² S/cm at room temperature.

This paper presents a review of recent progress in high-precision calculations for the ground state and low-lying excited states of helium, including the nonrelativistic energy, relativistic corrections of α² Ry, and quantum electrodynamic (QED) corrections of lowest order α³ Ry and next-to-leading-order α⁴ Ry, where α is the fine-structure constant. The calculations include the terms of order α⁴ Ry recently obtained by Pachucki (Phys. Rev. A, 74, 062510 (2006)). Estimates of the terms of order α⁵ Ry, including two-loop binding corrections, are included. Comparisons with experimental ionization energies indicate reasonably good agreement for the 1s^{2 1}S₀, 1s2s ¹S₀, 1s2s ³S₁, and 1s2p ³P_cm states, but there is a significant discrepancy for the 1s2p ¹P₁ state of 5.6± 3.2 MHz. An asymptotic formula for the calculation of the Bethe logarithm for Rydberg states with large angular momentum L is presented in an Appendix. PACS Nos.: 31.30.Gs, 31.30.Jv

We calculate very accurate ab initio ionization energies for both ⁴He I and ³He I as well as the isotope shifts for n = 1 to 10, L = 0 to 7 and combined these with precise laboratory data to produce a new table of levels for ⁴He I and the first table for ³He I. We adopted an experimental ionization potential of 5945 204 290 ± 33 MHz for ⁴He I and derived 5944 890 770 ± 33 MHz for ³He I. Additional calculations of the magnetic perturbations of ³He I provide the hyperfine levels, which compare favourably with the available measurements.PACS Nos.: 31.30.Gs, 31.30.Jv

New sharp line structure observed in the near-band-edge (1030 to 1135 meV) photoluminescence of Si(P, In) and Si(B, In) at temperatures ranging from 1.6 to 20 K, has been identified as due to radiative recombination of electrons bound to phosphorus donors with holes bound to indium acceptors. This is the first study of sharp line, donor–acceptor pair luminescence in silicon. Straightforward analysis, assuming only Coulomb and van der Waals interactions between otherwise isolated donor and acceptor centres indicates that recombination involving P and In centres separated by distances ranging from 7.7 to 20 Å is responsible for the observed sharp line structure. This structure is superimposed on the high energy shoulder of the broad band luminescence associated with recombination involving distant (average separation: 55 Å) P–In pairs. Transient measurements indicate decay times ranging from 70 to 100 μs for the most prominent sharp lines and an overall decay pattern consistent with that expected for donor–acceptor pair recombination.

A supersymmetric version of the modified Airy-function method is developed. Explicit calculations for eigenvalues are obtained for the Schrödinger potential V(x) = x⁶ − 3x². Comparison is made with exact numerical results as well as those of the Wentzel–Kramers–Brillouin (WKB), supersymmetric WKB (SWKB), and modified Airy-function approximation methods.

An eight-parameter bond-bending force model (BBFM), recently developed by us for zinc-blende (ZB) structure, has been used to study the lattice dynamics of other compounds of the II–VI and III–V groups. The model parameters were calculated using six critical point phonon frequencies, two elastic constants, and the lattice equilibrium condition. Phonon dispersion curves, phonon density of states, and Debye-characteristic temperatures have been calculated. The comparison of theoretical and the available experimental results reveals a fairly good agreement. The merits and demerits of the present model have been discussed in full.

Hartree–Fock calculations have been performed for the A = 4n nuclei ¹²C to ⁴⁰Ca, employing a selection of density dependent effective interactions. This selection consists of two density and momentum dependent delta function interactions, similar to the Skyrme interaction, and two density and momentum dependent finite range interactions whose radial forms are given as a sum of two Gaussian functions. A basis of single-particle axially deformed harmonic oscillator functions is used. Special emphasis is given to the study of the occurrence of alpha-particle type clustering in the density distributions of light A = 4n nuclei and the influence of the strength of the one-body spin–orbit field.

Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established. It is shown here that many or most of the observational data may be interpreted on the basis of a single physical mechanism, namely, internal atmospheric gravity waves.A comprehensive picture is envisaged for the motions normally encountered, in which a spectrum of waves is generated at low levels of the atmosphere and propagated upwards. The propagational effects of amplification, reflection, inter-modulation, and dissipation act to change the spectrum continuously with increasing height, and so produce different types of dominant modes at different heights. These changes, coupled with an observational selection in some cases, lead to the various characteristics revealed by the different observing techniques. The generation of abnormal waves locally in the ionosphere appears to be possible, and it seems able to account for unusual motions sometimes observed.

The construction and the use of a robust microbalance with a fused silica beam are described. The design is such that the microbalance is undisturbed by convection even in surroundings where it would be impossible to use an ordinary microbalance; nevertheless the instrument is very convenient to operate. A comprehensive theoretical treatment of the silica torsion balance and of the effects of constructional imperfections is given and shown to be in good agreement with experiment. The performance of the microbalance is illustrated by means of an example from the microchemical work of B. G. Harvey, where four samples of americium oxide, of masses between two and six micrograms, were weighed on 100 mgm. scale pans, with a proven accuracy better than 0.3%. The precautions that were taken to minimize the harmful effects of adsorption and dust are described. A commercial version of this microbalance is now available.