Rubidium Halides Research Articles

A modified doping procedure for high O2− concentrations in potassium and rubidium halides

physica status solidi (a)Volume 35, Issue 2 p. K137-K139 Short Note A modified doping procedure for high O concentrations in potassium and rubidium halides P. Matthys, P. Matthys Laboratorium voor Kristallografie en Studie van de Vaste Stof, Gent Search for more papers by this authorM. Vanhaelst, M. Vanhaelst Laboratorium voor Kristallografie en Studie van de Vaste Stof, Gent Research Fellow of the “Nationaal Fonds voor Wetenschappelijk Onderzoek” (Belgium).Search for more papers by this authorE. Boesman, E. Boesman Laboratorium voor Kristallografie en Studie van de Vaste Stof, Gent Search for more papers by this author P. Matthys, P. Matthys Laboratorium voor Kristallografie en Studie van de Vaste Stof, Gent Search for more papers by this authorM. Vanhaelst, M. Vanhaelst Laboratorium voor Kristallografie en Studie van de Vaste Stof, Gent Research Fellow of the “Nationaal Fonds voor Wetenschappelijk Onderzoek” (Belgium).Search for more papers by this authorE. Boesman, E. Boesman Laboratorium voor Kristallografie en Studie van de Vaste Stof, Gent Search for more papers by this author First published: 16 June 1976 https://doi.org/10.1002/pssa.2210350258Citations: 5 Krijgslaan 271, B 9000 Gent, Belgium. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume35, Issue216 June 1976Pages K137-K139 RelatedInformation

Second‐Order Raman Spectra of RbCl, RbBr, and RbI Crystals

AbstractThe polarized second order Raman spectra of three rubidium halide crystals, namely RbCl, RbBr, and RbI are computed on the basis of the theory proposed by Born and Brad‐burn, taking into account first as well as second neighbour polarizability coefficients. The three‐body force shell model is employed to determine the phonon frequencies, the phonon eigenvectors, and the polarizability tensor. The polarizability coefficients are assumed to be adjustable parameters. It is found that in addition to all the first neighbour coefficients, only eight second neighbour coefficients are sufficient to obtain good agreement between the experimental and the theoretical spectra.

Effects of pressure on optical F-bands in rubidium halides : K. Mamola and R. Wu, Department of Physics, Darmouth College, Hanover, NH 03755, U.S.A.

Effects of pressure on optical F-bands in rubidium halides : K. Mamola and R. Wu, Department of Physics, Darmouth College, Hanover, NH 03755, U.S.A.

Effects of pressure on optical F-bands in rubidium halides

High pressure optical absorption measurements have been made on additively colored RbCl and RbBr at pressures up to 10 kbar and on electrolytically colored Rbl up to 4 kbar. The pressure dependence of the F-band produced in RbCl by x-irradiation in the s.c. phase is also reported. Effects of the pressure induced structure transformation in these salts are described. F-band pressure shifts are related to a semi-empirical treatment which takes account of relative ion sizes. A new Ivey law for F-centers in host crystals having the s.c. structure is presented. This relation is established using all available F-band data including those for salts transformed to the s.c. structure by the application of high pressure.

Effects of pressure on magnetic properties of F-centers in rubidium halides

Room temperature magnetic resonance measurements have been made on additively colored RbCl and RbBr and on X-irradiated RbH at pressures up to 8 kbar. In RbCl and RbH pressure shifts of the F-center isotropic coupling constant a 1 were obtained from changes in the resolved EPR hyperfine structure. Pressure shifts of first and second shell hyperfine coupling constants of F-centers in RbBr were found from high pressure ENDOR spectra. Effects of the pressure induced polymorphic phase transformations in RbCl and RbBr are discussed. No evidence was found for a structure transformation in RbH. Room pressure ENDOR measurements on additively colored RbI were made at 77°K. The first and second shell hyperfine coupling constants are reported. All results accord well with the behavior of F-centers in other alkali halides.

Excitons and continuum transitions of rubidium halides in the 10-26 eV photon energy range at low temperatures

The reflection spectra of RbCl, RbBr and RbI single crystals were investigated for temperatures between 300K and 8K in order to study excitations from the Rb+4p level (<or approximately=16 eV) as well as the higher continuum transitions from the valence band (<or approximately=10 eV). The measurements were performed by use of the synchrotron radiation of DESY. The sensitivity for detecting details of the fine structure was increased by simultaneously measuring the wavelength-modulated spectra. The experimental procedure is briefly described. New spectral features have been resolved for the exciton multiplets from the Rb+ 4p level. They are discussed in the light of predictions of a recent model for the Rb+ 4p excitons based on ligand field theory. The continuum transitions associated with the valence band and the Rb+ 4p level show characteristic structure which is compared with calculations of the joint density of states.

Lattice thermal conductivities of RbBr, RbI, and RbCl from 80 to 400 K

The thermal conductivities $\ensuremath{\lambda}$ of RbBr, RbI, and RbCl were measured over the temperature range from 80 to 400 K with minimum uncertainties of \ifmmode\pm\else\textpm\fi{}2.5% at 80 K. The data were corrected for photon radiation, but the correction uncertainties caused the over-all measurement uncertainties to increase with increasing $T$. The data disagree with results by Eucken and Kuhn by as much as a factor of 4 but the RbCl data agree well with more recent work by Rosenbaum et al. The data were compared to an approximate equation for three-phonon umklapp scattering involving only acoustic mode phonons. The deviation of experimental thermal resistance ${\ensuremath{\lambda}}^{\ensuremath{-}1}$ values from calculated values increased smoothly with increasing mass ratio. The presence of four-phonon umklapp scattering processes in the rubidium halides cannot be excluded because of the high-temperature behavior of ${\ensuremath{\lambda}}^{\ensuremath{-}1}$. Distinct slope changes in ${\ensuremath{\lambda}}^{\ensuremath{-}1}$ near the Debye temperatures, similar to those which occur in Si and Th${\mathrm{O}}_{2}$, were not observed in any of the three compounds although the effect could have been masked by the large experimental uncertainties at high temperatures.

Infrared spectra of BO 2− in the alkali halides—I. Potassium and rubidium halides

The alkali halide pressed disk method has been used to observe the infrared spectra of BO 2 − in the potassium halide and the rubidium halide lattices. The anharmonic force field has been determined using a simplified quartic force field. The numerical values of the cubic and quartic force constants and the quadratic interaction force constant have been found to be invariant in the six lattices considered.

Formation and migration of vacancies in rubidium halides

Energies of formation of Schottky defects as well as cation and anion migration energies in RbCl, RbBr and RbI have been evaluated from ionic lattice calculations and the results are compared with the corresponding values obtained from ionic conductivity measurements. The experimental and calculated values of Schottky formation energies agree. Conduction in rubidium halides is mainly due to the movement of cation vacancies. The calculated value of the cation migration energy in RbCl is close to that obtained experimentally, but the calculated values in RbBr and RbI are somewhat higher than the experimental values.

Raman Scattering from RbF and RbBr

We present measurements of the three independent components of the second-order Raman scattering tensor for RbF and RbBr at 300 and 80 \ifmmode^\circ\else\textdegree\fi{}K, together with a brief analysis in terms of existing neutron data. The general features of the spectra are compared with those of the other members of the rubidium halide family.

Optical excitation of the Rb + 4p-level in rubidium halides at 8 K

In the 15–19 eV range new spectral features have been resolved in the reflection spectra of RbCl, RbBr, and RbI single crystals. They are not entirely consistent with results of a recently proposed ligand field model for the Rb +4p- excitons.

Temperature Dependence of Second-Order Raman Scattering in Potassium and Rubidium Halides

Temperature Dependence of Second-Order Raman Scattering in Potassium and Rubidium Halides

Debye–Waller factors for rubidium halides

The mean square displacements of atoms in RbF, RbCl, RbBr and RbI have been calculated for the temperature range 20 to 300°K utilizing the phonon frequencies determined from neutron-scattering measurements.

A Model Potential for Alkali Halide Crystals Including a Short Range Three‐Body Interaction

AbstractThe model potential including a short range three‐body interaction which was used by Sarkar and Sengupta [1,2] to calculate various static properties of some alkali halide crystals has been extended to include overlap interaction between next nearest neighbours. This has been used to calculate the cohesive energy, harmonic elastic constants, phase transition pressure, and transitionvolume for transition from sodium chloride to the cesium chloride structure in the case of potassium and rubidium halides. The results have been compared with experimental values and with the theoretical calculations done on other models. It is found that the inclusion of overlap interaction between next nearest neighbours considerably improves the overall agreement between theoretical and experimental results.

Photoelasticity in polycrystalline aggregates

A theory for the photoelastic behaviour of transparent polycrystalline aggregates consisting of randomly oriented anisotropic crystallites has been developed. Such an aggregate is isotropic but it becomes birefringent under the influence of a uniaxial load. The photoelastic constants of the aggregate are given by the components of the spatial average of the photoelastic tensor of the single crystal, and are worked out by assuming either the strain to be continuous (Voigt approximation) or the stress to be continuous (Reuss approximation). The components of the average photoelastic tensor are very different for these two limits. The elastic and the photoelastic constants of alkali halide aggregates have been evaluated for both the stress continuity and the strain continuity conditions. The maximum variation of the elastic constants in going from the Voigt to the Reuss condition is 50 per cent while the photoelastic birefringence can vary by as much as 300 per cent in alkali halides. In the case of KI and rubidium halides even the sign of the photoelastic birefringence is different for the two limits.

Shear Elastic Constant C44 and Phase Transformation of KCl

THE shear elastic constant C44 for KCl, KF and the rubidium halides is of special interest because it decreases with pressure. Born1 and Misra2 pointed out that a vanishing shear elastic constant is a sufficient condition for a phase transformation. This suggestion has been elaborated by Anderson and Demarest3 and by Thomsen4 to postulate that the phase transformation from the NaCl to CsCl structure at high pressure may be associated with the vanishing of C44. If borne out by experiment, this suggestion would be of considerable physical interest. Based on values of the first pressure derivative of C44 for the halides, measured at relatively low pressure, Demarest5 extrapolated C44 to high pressure and showed that the phase transitions actually take place at much lower pressures than those predicted by the vanishing of C44. Such extrapolation, however, does not rule out the possibility of a large downward curvature in the C44/P relation at higher pressures, especially at pressures near the phase transformation leading to a vanishing C44. Thus direct measurement of C44 up to the pressure of phase transformation appears necessary for a test of the hypothesis. I present here experimental results for ultrasonic determination of C44 for a KCl single crystal up to 20 kbar at which pressure it transforms from its NaCl structure to the CsCl structure.

Cadmium centres in cesium and rubidium halides

The peak positions and half-widths of cadmium bands in cesium and rubidium halides are reported. In cesium halides three bands are observed in the region (240 ÷ 300) nm, while in rubidium halides no such bands are observed. Two new bands were obtained in some of these crystals where irradiation was possible and are similar to theD1 andD2 bands. In additively or electrolytically coloured crystals an intense broad band was observed in the UV region in all these crystals besides theF-band and in crystals quenched from high temperatures (about 600 °C) we observe only the UV band. The intensity of this band is a function of the cadmium content. Associated with this UV band is also a broad Lorentzian EPR line. The UV band obtained after thermally quenching from 600 °C is ascribed to the cadmium colloids. No aggregateM-like centres are observed on optical bleaching of theF-band. The values ofWs,Ec andWa in the case of RbCl : Cd have been obtained from electrical-conductivity measurements as 1.40, 0.9 and 0.62 eV respectively. The dielectric-loss measurements in cadmium-doped cesium iodide give a bound-vacancy migration, energy ∼ 0.58 eV.

Transitions polymurphiques des solides induites par la pression traitement mathématique de la cinétique de l'effet de « rétropression »

Using the experimental results of the hysteresis effect, mathematical models are proposed to describe the kinetics of the rubidium halides phase transitions. Only the first stage of the reaction is considered. It is assumed that the nuclei of the new phase are independent of each other. The general relation between pressure and volume obtained for the different models is :

Lattice dynamics of rubidium halides

Lattice dynamics of rubidium halides have been studied on the basis of a theoretical model recently developed by Verma and Singh (1969) by including the effect of three body forces into the framework of the shell model. The results of the calculation are found to agree fairly well with the available experimental data on dispersion relations, second order Raman spectra and specific heats.

Au - luminescence in alkali halides

The luminescence of Au - centers between 4 K and 300 K is investigated in 7 alkali halides It consists of 4 ultraviolet bands α, A′, B′ and C′ similar to those of the isoelectronic Tl +. The halfwidth of all bands is smaller than that of the corresponding absorption bands. The Stokes shift is so small, that in some of the α and A′ emission bands zero phonon lines and vibronic structure are detected. In KCl A′ emission and A absorption are found symmetrically placed relative to the common zero phonon line. Differing from the C absorption which belongs to a 6 1S o → 6 1P 1 transition the C′ emission is interpreted to be due to a 7 3P 1 → 6 1S o transition. With increasing temperatures radiationless transitions become dominant. Their activation energies are determined. The absorption data for Au - bands in alkali halides now include those of the rubidium halides.