Summability of the perturbation series of excitonic exchange,CuCl as an example

It is shown that for Wannier excitons the influence of exchange can be calculated by summing up a Greens-function series. A numerical model- calculation for the non-dipole-part of the exchange energy in CuCl is in good agreement with experimental data. Results of earlier work on II–VI compounds are critically surveyed and discarded in the light of our results.     

Method of determining the eigenfrequencies of an ordered system of nanoobjects

A method is proposed to determine the eigenfrequencies of nanostructures (nanotubes and nanocrystals) by measuring the eigenfrequencies of a “large system” that comprises an array of vertically oriented similar nanotubes or nanocrystals equidistantly grown on a substrate. It is shown that the eigenfrequencies of a single nanoobject can be derived from the eigenfrequency spectra of the large (array-substrate) system and of the substrate. In other words, using experimental data for large systems, one can determine the eigenfrequencies of single nanoobjects, which are difficult to determine otherwise. By way of example, the eigenfrequencies of an array of zinc oxide micro-or nanocrystals on a sapphire substrate are calculated.     

Local and gap modes due to a substitutional impurity in alkali halides: One dimensional treatment

Local modes for substitutional impurity H in NaCl, NaBr and KCl have been calculated. Isotope shift for ³⁵Cl and ³⁷Cl substituted in KI has also been calculated. Good agreement with the experimental data has been obtained.     

Microhardness of crystals of KBr-KI solid solutions with Sr2+ and OH− impurities

The microhardness, conductivity, and dielectric-loss angle have been studied in KBr and KI single crystals and in their solid solutions with Sr²⁺ and OH^– impurities. It is shown that the Sr²⁺ impurity dissolves only slightly in KI crystals and in KBr-KI solid solutions having a large KI content. Addition of the anionic OH^– impurity to the molten salts reduces the micro-hardness of KBr but it does not affect that of KI crystals or KBr-KI solid solutions having a large KI content. The composition dependence of the microhardness for KBr-KI solid solutions is constructed on the basis of the microhardness values for the corresponding crystals purified of cationic impurities of different valence.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 18–21, October, 1969.     

On the determination of the rigidity parameters of nanoobjects

The aim of this work is to develop theoretical grounds for experimental determination of the rigidity parameters of nanoobjects. An efficient way of determining elastic moduli used in macromechanics consists in measuring the eigenfrequencies of an object under testing. Details of applying this approach to nanoobjects are discussed. A method of experimental determination of the rigidity parameters is suggested that is based on dynamic damping of vibrations (antiresonance). This method provides the possibility of separating out the eigenfrequencies of the nanoobject from the frequency spectrum of a system composed of a nanoobject and the cantilever of an atomic force microscope.     

Optical absorption of s2-configuration ions in alkali halide crystals—III: The A band in Sn2+-doped crystals

The line shape of the A band in KCl:Sn²⁺, KBr:Sn²⁺, KI:Sn²⁺, RbCl:Sn²⁺ and RbBr:Sn²⁺ has been measured as a function of temperature between about 15 K and room temperature. As the spectra for all these systems are similar detailed results are presented only for RbCl: Sn²⁺, RbBr:Sn²⁺ and KBr: Sn²⁺. The experimental data resemble those of a previous study on KBr:In⁺ and KG:In⁺ in that the A band consists of two broad, overlapping components designated A₁ (the low energy component) and A₂. The separation between A₁ and A₂ is more marked at low temperature for Sn²⁺ than for In⁺, and no inversion of the ratio of the peak heights of A₁ and A₂ occurs as the temperature is varied, as was so for In⁺. Detailed calculations of the line shape are presented for KBr:Sn²⁺. These calculations show that one cannot account for the line shape purely in terms of the dynamical Jahn-Teller effect and that there is in addition a static splitting of the A state caused by a lowering in the symmetry of the crystal field.     

The origin of localized vibrations in KI: Cl and KI: H crystals

The resonant, gap, and local vibrational modes of Cl and H impurities in KI crystals are calculated recursively using the shell model. The contributions from ions located in various coordination shells around the impurity to the formation of localized vibrations are studied. The results of the calculations are in satisfactory agreement with the experimental data.     

Quantitative Determination of Reactive Species in Alkali Halide Disks

Abstract

As part of an infrared investigation of the kinetics of the reactions of KMnO₄ in a KI disk and of KIO₄ in a KI disk, the stoichiometry of the two reactions was needed. A previous study¹ has shown that MnO₄ ^? reacts in a KI matrix to produce IO₄ ^? (which then reacts further to form IO₃ ^?) and MnO₂. Iodate ion is the only observable product in the reaction of IO₄ ^? in a KI matrix¹. The infrared absorption at 740cm^?1, which is due to the presence of IO₃ ^?, was found to obey the Beer-Lambert Law. However, calibration curves for KMnO₄ in KI and for KIO₄ in KI could not be obtained because both species reacted with the dispersing medium during the preparation of the disk¹. It was also observed that no immediate reaction occurred when KBr or KC1 disks containing KMnO₄, or KIO₄ were prepared. Thus, an extrapolation method was sought which would permit the estimation of calibration curves for the reactive species.     

Influence of defects on the luminescence in KI

Quenching of exciton luminescence caused by coloration with u.v.-irradiation in KI and KI:Tl has been studied. Reduction in the luminescence intensity by coloration is found to depend on the coloration temperature as well as on the concentration of Tl⁺ ions. Evidences are shown that the defects with which excitons interact are vacancies and V-centers.     

Organic dopant added polyvinylidene fluoride based solid polymer electrolytes for dye-sensitized solar cells

The effect of phenothiazine (PTZ) as dopant on PVDF/KI/I₂ electrolyte was studied for the fabrication of efficient dye-sensitized solar cell (DSSC). The different weight percentage (wt%) ratios (0, 20, 30, 40 and 50%) of PTZ doped PVDF/KI/I₂ electrolyte films were prepared by solution casting method using DMF as a solvent. The following techniques such as Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), X-ray diffractometer (XRD) and AC-impedance analysis have been employed to characterize the prepared polymer electrolyte films. The FT-IR studies revealed the complex formation between PVDF/KI/I₂ and PTZ. The crystalline and amorphous nature of polymer electrolytes were confirmed by DSC and XRD analysis respectively. The ionic conductivities of polymer electrolyte films were calculated from the AC-impedance analysis. The undoped PVDF/KI/I₂ electrolyte exhibited the ionic conductivity of 4.68×10⁻⁶ S cm⁻¹ and this value was increased to 7.43×10⁻⁵ S cm⁻¹ when PTZ was added to PVDF/KI/I₂ electrolyte. On comparison with different wt% ratios, the maximum ionic conductivity was observed for 20% PTZ-PVDF/KI/I₂ electrolyte. A DSSC assembled with the optimized wt % of PTZ doped PVDF/KI/I₂ electrolyte exhibited a power conversion efficiency of 2.92%, than the undoped PVDF/KI/I₂ electrolyte (1.41%) at similar conditions. Hence, the 20% PTZ-PVDF/KI/I₂ electrolyte was found to be optimal for DSSC applications.     

Simplified method for solving problems of vibrating plates of doubly connected arbitrary shape,part II: Applications and experiments

The eigenfrequencies of ring-shaped polygonal plates, ring-shaped elliptical plates, rectangular plates with elliptical inner boundaries and circular plates with elliptical inner boundaries are obtained. The method developed by the author in the companion paper (Part I) is applied for finding the eigenfrequencies. To verify the present results, experimental tests have also been carried out for some important cases.     

Origin of discrepancy in the theoretical value of the polarizability correction to the (μ4He)+ energy levels

Different approaches in calculating the polarizability correction to the energy levels of the muonic ⁴He ion are compared. These calculations disagree with each other by giving results 3 to 10 times larger than the experimental uncertainty. The origin of the major discrepancy is traced to the treatment of the nuclear excitations. It is shown that the experimental value of the electric polarizability of ⁴He provides a crucial restriction on model calculations.     

Dipolar and quadrupolar detection using an FT-ICR MS setup at the MPIK Heidelberg

Dipolar and single-phase two-electrode quadrupolar detection schemes have been investigated at a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) setup built for the KATRIN experiment at the Max-Planck-Institute for Nuclear Physics (MPIK) in Heidelberg. We present first experimental results of ⁷Li^?+? signals from a cylindrical Penning trap configuration for both detection schemes. While the prominent signal of the conventional dipolar detection scheme marks the reduced cyclotron frequency, the main signal for the quadrupolar detection appears at the sum of the reduced cyclotron frequency and the magnetron frequency. For ideal trapping fields, this sum frequency equals the ion cyclotron frequency ?? _c ?=?qB/(2??m). Sidebands due to the combined motions of the cyclotron mode and magnetron mode are observed by quadrupolar detection which allows the determination of the respective combinations of eigenfrequencies.     

BH4− Induced far-infrared absorption in the phonon gap of KI

High resolution measurements of the far-infrared lattice gap modes due to BH₄^? in KI are reported. The observed bands at 85.45 ± 0.05 and 84.94 ± 0.05 cm^?1 are ascribed as resulting from the presence of two stable boron isotopes in the BH₄^? ion. The gap modes are calculated by allowing for the elastic relaxation of the lattice around the impurity. The results of a calculation for the Br^? gap modes in KI are also presented.     

Influence of pyrazole on the photovoltaic performance of dye-sensitized solar cell with polyvinylidene fluoride polymer electrolytes

We investigate the influence of the pyrazole content on the polyvinylidene fluoride (PVDF)/KI/I₂ electrolytes for dye-sensitized solar cells (DSSCs). The solid polymer electrolyte films consisting of different weight percentage ratios (0 20, 30, 40, and 50 %) of pyrazole doped with PVDF/KI/I₂ have been prepared by solution casting technique using N,N-dimethyl formamide (DMF) as a solvent. The as-prepared polymer electrolyte films were characterized by various techniques such as Fourier transform infrared spectroscopy (FT-IR spectroscopy), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), alternate current (AC)-impedance analysis, and scanning electron microscopy (SEM). The 40 wt% pyrazole-PVDF/KI/I₂ electrolyte exhibited the highest ionic conductivity value of 9.52?×?10^?5 Scm^?1 at room temperature. This may be due to the lower crystallinity of PVDF and higher ionic mobility of iodide ions in the electrolyte. The DSSC fabricated using this highest ion conducting electrolyte showed an enhanced power conversion efficiency of 3.30 % under an illumination of 60 mW/cm² than that of pure PVDF/KI/I₂ electrolyte (1.42 %).     

Similarity Transformations of Hermitian Hamiltonians and Pseudo-Hermitian Coupling Between Two Electromagnetic Modes

Pseudo-Hermitian Hamiltonians and pseudo-Hermitian coupling between two electromagnetic modes are analyzed by using similarity transformations of Hermitian Hamiltonians or of Hermitian operators, including a special metric and biorthogonal relations replacing the usual orthogonal relations used in quantum mechanics. The coupling between two electromagnetic (em) modes including certain decay and amplification processes is related to a coupling matrix G which has parity-time (PT) symmetry and which obeys the pseudo-Hermiticity condition ηGη⁻¹ = G ^† where η is a metric. The linear equations representing the pseudo-Hermitian coupling between the two em modes are diagonalized, in the interaction picture, by introducing ‘dressed’ αˉ and β~ operators which have real or pure imaginary eigenfrequencies. The commutation-relations (CR) for the α~ and β~ operators and for the two-mode operators ā and b~, in the interaction picture and under the condition of real eigenfrequencies are obtained by the use of the pseudo-Hermiticity property of the G matrix. These CR for real eigenfrequencies, are preserved in time without any Langevin noise terms.     

Effect of cubic hydrostatic compression on the elastic properties of single crystals of halides of sodium and potassium

Experimental studies (by the ultrasonic pulse method) and theoretical investigations (with the model of polarizable ions) were made of changes in the elastic moduli of single crystals of NaCl, NaBr, NaI, KCl, KBr, and KI in cubic hydrostatic compression in the pressure range up to 10⁸ Pa at a temperature of 298°K. The experimental unit and method of measurement are described. Theoretical values of the derivatives of the elastic moduli with respect to pressure are presented for the compounds studied and are compared with existing empirical data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 71–75, October, 1985.     

Meson exchange contributions to electron-3He scattering

Theoretical calculations have been done corresponding to Ω-, σ-, π°-meson exchange between pairs of nucleons in ³He for e-³He inelastic scattering and compared with the experimental data for 14.6 GeV incident electrons. The purpose of these calculations was to see if these calculations could account for the experimental cross sections on either side of the quasi-elastic peak, where the impulse approximation calculations gave results less than 10% of the experimental cross sections. Meson exchange calculations account impressively for the experimental cross sections on the left side of the quasi-elastic peak, whereas the contribution of the meson exchange calculations on the right side of the quasi-elastic peak was found to be negligible.     

Predicting the eigenmodes of a cavity containing an array of circular pipes

An array of pipes inside a cavity, as found, for example, in a shell-and-tube heat exchanger, changes the eigenfrequencies of the cavity. It can be tedious to determine the shifted eigenfrequencies with a finite-element model. Based on previous work by Meyer and Neumann, Parker proposed a simple relationship for predicting the shifted eigenfrequencies. In this paper, results obtained from this relationship are compared with eigenfrequencies obtained from very accurate finite element simulations. From the results it can be concluded that Parker's relationship gives fairly good predictions of the eigenfrequencies for the first few modes in a cavity with pipes arranged in a rectangular configuration. The predictions are not so accurate for pipes arranged in a diamond configuration, and a modified version of the relationship is suggested for this configuration. If the number of pipes in the cavity is small, the simple relationship is no longer valid.     

Fast luminescence processes in KI : In caused by excitation in the a absorption band

The temperature dependence of the decay time (τ) of the luminescence pulses from the 440 nm emission band as well as the rise time (τ_R) of luminescence pulses from the 575 nm emission band has been investigated for KI : In by pulsed light excitation in the A absorption band. From the agreement of τ and τ_R independent of the temperature it can be concluded that the X minimum on the ³T₁₄ adiabatic potential energy surface (APES) is mainly populated by a radiationless transition from the tetragonal T minimum of the same APES.Furthermore, a comparison of parameters for the impurity centre luminescence corresponding to the tetragonal emission band in KI : In and KI : Tl has been drawn.