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1.
The hardening effect of Mg2+, Ca2+, Sr2+, Cd2+ and Ba2+ impurities in polycrystalline AgCl was investigated. With exception of Mg2+ the hardening effect of the impurities decreases with increasing atomic number (atomic weight). The hardening effects of Mg2+ and Ca2+ are expressively stronger than those of the three remaining impurities. Approximately linear dependence of the stress at the beginning of plastic deformation on the impurity concentration was found. Possible causes of the different hardening effects of the divalent impurities are discussed. 相似文献
2.
The far-infrared absorption in the phonon band of CsBr due to Na+, K+, Rb+, In+, and Tl+ impurities has been measured and compared with the calculated density of phonon states of the host lattice. 相似文献
3.
The pair modes due to Cl?, Br?, Na+W and Rbv impurities in KI have been investigated using the Greens function technique. Group theory is used to put the final results as solutions of (2 × 2) determinants which could be tried by a hand calculator. Even a mass defect approximation reproduced the gap modes due to chlorine pairs, but in all cases a small change in the force constant, deduced from fitting single impurity gap modes, was used. The Raman active modes in all these cases were also computed. 相似文献
4.
Quadrupole moment and dipole polarizability tensor components are calculated at the correlated complete-active-space self-consistent-field (CASSCF) and complete-active-space perturbation-theory (CASPT) levels for 2P states of O?, F, Ne+, Na2+, S?, Cl, Ar+, 98, K2+ , Se?, Br, Kr+, Rb2+ and 3P, 1D, 1S states of O?, F+, Ne2+, Na3+, S, Cl+, Ar2+, K3+, Se, Br+, Kr2+, Rb3+. Relativistic corrections are included perturbatively for the 34- and 35-electron systems. 相似文献
5.
The ordering of the mobile ions in the conducting layers to form an superlattice has been investigated in K+, Ag+ and Rb+ β-aluminas by electron diffraction. In addition to the correlation of mobile ions within the conduction layer, the correlation between conduction layers has also been detected in Rb+ β-alumina with periods of 68.4 Å and 22.8 Å, or three and one multiple of the dimension. A possible mechanism for such long distance correlation through spinel blocks is discussed. 相似文献
6.
Normal and less polarised water models are used as the solvent to investigate Hofmeister effects and alkali metal ionic effects on dodecamer d(CGCGAATTCGCG) B-DNA with atomic dynamics simulations. As normal water solvent is replaced by less polarised water, the Hofmeister series of alkali metal ions is changed from Li+ > Na+ ? K+ ? Cs+ ? Rb+ to Li+ > Na+ > K+ > Rb+ > Cs+. In less polarised water, DNA experiences the B→A conformational transition for the lighter alkali metal counterions (Li+, Na+ and K+). However, it keeps B form for the heavier ions (Rb+ and Cs+). We find that the underlying cause of the conformation transition for these alkali metal ions except K+ is the competition between water molecules and counterions coupling to the free oxygen atoms of the phosphate groups. For K+ ions, the ‘economics’ of phosphate hydration and ‘spine of hydration’ are both concerned with the DNA helixes changing. 相似文献
7.
8.
A. Valance 《Physics letters. A》1976,59(4):271-273
A Hellmann type pseudopotential, is used to calculate the six lowest Σ potential energy curves of Na+2, K+2, Rb+2 and Cs+2 molecular ions. 相似文献
9.
The reactions between AgI and Rb2AgI3, RbI and RbAg4I5 and AgI and RbI have been investigated by measurements of reaction layer thickness and by experiments with inert markers. A theoretical derivation of the growth kinetics for reactions with double layers is given. The Rb+-diffusion coefficients, which are needed to apply these relations to the reaction between AgI and RbI, have been obtained from an investigation of the other two reactions which form only a single product layer. The diffusion coefficient of Ag+in Rb2AgI3 was also determined from conductivity measurements on Rb2AgI3. 相似文献
10.
Abstract The relative roles of the materials of construction of the reactor (stainless steel or titanium) and the effects of Group 1 cations are discussed in terms of their effect on the rate of decarboxylation of acetic acid derivatives, RCO2H. Past work indicates that the reaction container composition has a very large effect when R is CH3—. A smaller but significant effect is seen when R is electron neutral (i.e., R=H). When R is electron Withdrawing the rate depends less on the reactor type than the nature of R. The effect of the counter ion M on the rate of decarboxylation of monovalent malonate salts, HC&CHzC02M, is discussed for M=Li+, Na+, K+, Rb+, and Cs+. The rate generally increases with the ionic radius except that the Rb+ salt exhibits the fastest rate. Preliminary explanations are given. 相似文献
11.
《Journal of Physics and Chemistry of Solids》1986,47(7):707-717
The electrical conductivity of a great number of SrCl2 crystals, either purified or doped with Na+, K+, Rb+, Gd3+ and Ce3+, has been studied. The microscopic models used for the interpretation of the results have been justified by dielectric loss measurements, ITC and EPR (for Gd3+). The thermodynamic parameters of point defects have been derived, over the temperature range 420–860 K, from the fitting of experimental data to the equations of the Lidiard-Debye-Hückel theory. The values of the enthalpies of Cl vacancy mobility (0.30 eV) and Cl interstitial mobility (0.76eV), association of Cl vacancy with Na+ (0.53 eV), K+ (0.42 eV), Rb+ (0.40 eV) and ionic Frenkel defects formation (2.20 ± 0.11 eV) have been used in the interpretation of the experimental results over a large concentration range. The solubility enthalpy of Na + is 1.2 ± 0.1 eV; the solubility of the rare earths is very small at low temperature. The thennodynamic parameters which have been found have been compared with other known experimental values and with theoretical results. 相似文献
12.
Mohamed A. Mahmoud 《Central European Journal of Physics》2008,6(3):530-538
We have studied the formation of the molecular ion Rb2+ and the atomic ion Rb+. These are created in laser excited rubidium vapor at the first resonance, 5s–5p and 5p-nl transitions. A theoretical model
is applied to this interaction to explain the time evolution and the laser-power dependence of the population density of Rb+ and Rb2+. A set of rate equations which describe: the temporal variation of the population density of the excited states; the atomic
ion density; and the electron density, were solved numerically under the experimental conditions of Barbier and Cheret. In
their experiment the Rb concentration was 1×1013cm−3 and the laser power was taken to be 50–500 mW at vapor temperature = 450 K. The results showed that the main processes for
producing Rb2+ are associative ionization and Hornbeck-Molnar ionization. The calculations have also showed that, the atomic ions Rb+ are formed through the Penning Ionization (PI) and photoionization processes. Moreover, a reasonable agreement between the
experimental results and our calculations for the ion currents of the Rb+ and Rb2+ is obtained.
相似文献
13.
Randell L. Mills William Good Peter M. Jansson Jiliang He 《Central European Journal of Physics》2010,8(1):7-16
Rb+ to Rb2+ and 2K+ to K + K2+ each provide a reaction with a net enthalpy equal to the potential energy of atomic hydrogen. The presence of these gaseous ions with thermally dissociated hydrogen formed a plasma having strong VUV emission with a stationary inverted Lyman population. Significant Balmer α line broadening of 18 and 9 eV was observed from a rt-plasma of hydrogen with KNO3, and RbNO3, respectively, compared to 3 eV from a hydrogen microwave plasma. The reaction was exothermic since excess power of about 20 mW/cc was measured by Calvet calorimetry. We propose an energetic catalytic reaction involving a resonance energy transfer between hydrogen atoms and Rb+ or 2K+ to form a very stable novel hydride ion. Its predicted binding energy of 3.0471 eV with the fine structure was observed at 4071 Å, and its predicted bound-free hyperfine structure lines matched those observed for about 40 lines to within.01 percent. Characteristic emission from each catalyst was observed. This catalytic reaction may pump a CW HI laser. 相似文献
14.
《Solid State Ionics》1987,25(1):41-44
Complexes of alkali metal salts with various polymers have for some time been recognized as fast ionic conductors. Polymer electrolyte fast ion conductors are currently under consideration for use in high energy density electrochemical cells. In order to aid in our understanding of the mechanism of ionic conductivity we have examined systematically complexes of poly(ethylene oxide) (PEO) with the alkali metal salt series of Li+, Na+, K+, Rb+ and Cs+ with both tetraflouroborate (BF4-) and trifluoromethanesulfonate (CF3SO4-) anions. The ratio of monomer to salt was 10:1 in all cases. Complex impedance measurements were made on all samples in the temperature range 40°–125°C. With CF3SO4- as the anion a definite trend was apparent with the smallest cation Li+ being the worst conductor and Cs+, the largest cation, being the best. When BF4- salts are used, the Na+ complex is found to be the best conductor and Rb+ the worst. This study, in connection with our earlier studies, has shown that synergy between cation and anion in the polymer matrix is an important consideration in determining the ionic conductivity. 相似文献
15.
Nathan A. Stump George K. Schweitzer Lester L. Pesterfield Joseph R. Peterson George M. Murray 《光谱学快报》2013,46(8):1421-1432
Abstract Salts of the [Eu(2,6-pyridinedicarboxylate)3]3- complex anion and various monovalent inorganic and organic counterions (Li+, Na+, K+, Rb+, Cs+, NH4 +, and pyridinium+) have been synthesized and studied by emission spectroscopy. The Eu3+ ion emission spectra exhibited by these salts have been observed with high resolution (less than 1.0 cm?1) and at low temperature (77 K). The emission spectra of these compounds indicate that changing the attached counterion does not affect the site symmetry observed by the europium ion beyond slight distortions indicated by small shifts in the energies of the Eu3+ electronic levels. 相似文献
16.
The adsorption of ethylene by zeolite NaY and zeolite NaY modified by cation exchange with potassium, rubidium, and cesium ions was studied. Cation exchanges were carried out using KNO3, RbNO3, and CsNO3 in the concentration ranges of 0.2-10 mM. XRD patterns and specific surface areas illustrated that modification of NaY zeolite by very dilute solutions containing K+, Rb+ and Cs+ did not lead to significant changes in the crystallinity. Analysis of metals content (ICP-OES) showed that Cs+ can replace Na+ better than Rb+ and K+. Particle analysis indicated slight decreases in surface area but pore volumes and pore diameters remained unchanged. Ethylene adsorption isotherms indicated that Na-Y zeolite which was modified by 5.0 mM KNO3, 0.5 mM RbNO3 and 1.0 mM CsNO3 could adsorb ethylene better than zeolite Na-Y. K-NaY zeolite adsorbed up to 102.45 cm3/g ethylene, while Rb-NaY and Cs-NaY zeolites adsorbed up to 98.50 cm3/g and 90.15 cm3/g ethylene, respectively. Ethylene adsorption capacities depended on number of adsorption sites and surface interactions. 相似文献
17.
Die Adsorption von Tracermengen der Alkaliionen (22Na+, 42K+, 86Rb+) aus gemischten Lösungsmitteln (z. B. Wasser-Methanol, Äthanol, -Aceton, -Dioxan) an Aktivkohle (KO) steigt mit zunehmender Konzentration an organischem Lösungsmittel ab einem bestimmten Gehalt exponentiell an. Dabei nehmen die adsorbierten Ionenmengen zu, desgleichen die Geschwindigkeit der Adsorption. Bei vergleichbarer spezifischer Aktivität hängt die Adsorption von der Art und Zusammensetzung des Lösungsmittelgemisches ab. Werden die maximal adsorbierten relativen Ionenmengen bei konstanter spezifischer Aktivität gegen die reziproke Dielektrizitälskonstante des entsprechenden Lösungsmittelgemisches aufgetragen, so erhält man für bestimmte Konzentrationsbereiche an organischem Lösungsmittel charakteristische Geraden, deren Steigungen in der Reihenfolge 22Na+, 42K+, 86Rb+ abnehmen. Auβer der Zusammensetzung des Lösungsmittelgemisches sind für die Adsorption der Alkaliionen auch spezielle Wechselwirkungen zwischen Kationen und Solvatmolekühn von Einfluβ. 相似文献
18.
K. Tanimura 《Journal of Physics and Chemistry of Solids》1978,39(7):735-741
The role of Rb+ ions on defect formation in KBr has been studied. The impurity suppresses colorability due to X-raying at 6 K, but does not result in the formation of any centers characteristic to Rb+ ions at this temperature. A new optical absorption band peaked at 3.19 eV is produced only by thermal annealing of irradiated KBr:Rb. This band is annealed in parallel to the annealing of the F band in a stage at 55 K, obeying second-order rate equation with an activation energy of 0.102 eV. This band is ascribed to the HA(Rb+)-center. Calculation is made on the elastic interaction energy between the H-center and a Rb+ ion, to show that the interaction along 〈110〉 is repulsive, whereas that along 〈001〉 is attractive. Based on this result of calculation, the structure and the formation mechanism of the HA(Rb+) center, and origin of suppression of colorability at 6 K are discussed. The difference in the interaction of the interstitial atom with Rb+ during its dynamical motion and thermal motion is emphasized. 相似文献
19.
The binding interactions of bis‐3‐benzo‐15‐crown‐5 ethers and bis‐3‐benzo‐18‐crown‐6 ethers (neutral hosts) with a series of alkali metal cations Na+, K+, Rb+ and Cs+ (charged guests) were investigated using quantum chemical density functional theory. Different optimized structures, binding energies and various thermodynamic parameters of free crown ethers and their metal cation complexes were obtained based on the Becke, three‐parameter, Lee–Yang–Parr functional using mixed basis set (C, H, O, Na+ and K+ using 6‐31 g, and the heavier cation Rb+ and Cs+ using effective core potentials). Natural bond orbital analysis is conducted on the optimized geometric structures. The main types of driving force host–guest interactions are investigated. The electron donating O offers a lone pair of electrons to the contacting LP* (1‐center valence antibond lone pair) orbitals of metal cations. The bis‐3‐benzocrown ethers are assumed to have sandwich‐like conformations, considering the binding energies to gauge the exact interactions with alkali cations. It is found that there are two different types of complexes: one is a tight ion pair and the other is a separated ion pair. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
20.
Successive structural transitions of KCdF3 and K0.5Rb0.5CdF3 have been studied by means of thermal diffusivity, polarized light scattering and X-ray diffraction. It is found that transitions occur at about 460 K and 475 K in KCdF3, and at 222 K, 232 K, 250 K, 258 K and 268 K in K0.5Rb0.5CdF3. The partial exchange between K+ and Rb+ ions gives rise to simultaneous condensation of the Mz 3 and Rx 25 soft phonons. 相似文献