The Urbach Rule for the Sodium- and Potassium-Halides

1974 ◽  
Vol 29 (1) ◽  
pp. 145-157 ◽  
Author(s):  
Tetsuhiko Tomiki ◽  
Takeo Miyata ◽  
Hirokazu Tsukamoto
Keyword(s):  
Temperature Dependence ◽  
Acoustic Phonon ◽  
Frequency Factor ◽  
Host Lattice ◽  
Exciton Peak ◽  
Urbach Rule ◽  
Temperature Dependences ◽  
Hole Band ◽  
Sodium And Potassium ◽  
Potassium Halides

Phenomenological and physical aspects of the intrinsic tail spectra of the alkalihalides are studied referring to the new results on the intrinsic tail spectra of KBr and KI and to the temperature dependences of the lowest-energy Γ-exciton peak of the sodium- and potassium-halides. Systematically analysing the temperature dependence of the steepness parameter σs (T) of the Urbach rule for these halides, it is found that the frequency factor has the value nearly equal to the acoustic phonon energy at X or L of each host lattice and the steepness constant σs0 becomes larger in passing from fluoride to iodide. This halogen dependence of σs0 is discussed in terms of the hole band-mass of the Γ8-level.

Temperature Dependences in the O + OH → O2 + H Reaction. Quasiclassical Trajectory Calculation

1993 ◽  
Vol 58 (2) ◽  
pp. 234-243 ◽  
Author(s):  
Viliam Klimo ◽  
Martina Bittererová ◽  
Stanislav Biskupič ◽  
Ján Urban ◽  
Miroslav Micov
Keyword(s):  
Temperature Dependence ◽  
Energy Surface ◽  
Analytical Form ◽  
Mean Values ◽  
Quantum Numbers ◽  
Mean Lifetime ◽  
Temperature Dependences ◽  
Quasiclassical Trajectory Calculation ◽  
The Mean ◽  
Combustion Processes

The reaction O + OH → O2 + H in conditions of combustion of hydrocarbons and polymers was modelled by using the method of quasiclassical trajectories. The potential energy surface was determined by the multiconfiguration interaction method and fitted with the analytical form of the extended LEPS function. Attention was paid to the mean values of the vibrational and rotational quantum numbers of O2 molecules and their temperature dependence. The temperature dependence of the mean lifetime of the OOH collision complex was also examined. The calculated rate constants were analyzed and compared with the experimental data over the temperature region of the combustion processes.

scholarly journals The diamagnetic susceptibilities of salts forming ions with inert gas configurations II-The alkaline halides

1935 ◽  
Vol 152 (876) ◽  
pp. 342-353 ◽  
Author(s):  
G. W. Brindley ◽  
F. E. Hoare ◽  
Richard Whiddington
Keyword(s):  
Crystalline State ◽  
Experimental Methods ◽  
Inert Gas ◽  
Complete Set ◽  
Sodium And Potassium ◽  
Potassium Halides

The data so far published on the diamagnetic susceptibilities of the alkaline halides, measured for the salts in the crystalline state, are very discordant and incomplete, as reference to Table I will show. The aim in carrying out these experiments has been twofold: firstly, to obtain a complete set of values for these salts and secondly to examine more closely than has hitherto been possible how rigorously the susceptibilities of simple crystalline salts are additive. It has already been established that the susceptibilities are approximately additive, but it has not been possible to test this with exactitude because of ( a ) the large discrepancies between the results obtained by previous observers, and ( b ) the lack of data for many crystals. The discrepancies may have arisen to some extent from the different experimental methods, some of which are more accurate than others and some of which may introduce errors peculiar to themselves. We have therefore made a complete re-determination of the susceptibilities of all the alkaline halides, using the same apparatus and method under the same conditions. Since any systematic experi-mental errors will affect all our results to approximately the same extent, we shall be in a stronger position for testing the additivity of the susceptibilities than if we rely partly on our own and partly on other observers’ results. Previous investigators have measured the susceptibilities of some compounds in the crystalline state and others in solution; the latter are of no help in connexion with our problem, for an examination of the available data suggests that solutions have susceptibilities higher by several per cent, than the corresponding crystals. We cannot, therefore, arrive at any certain conclusion by using results obtained partly for crystals and partly for solutions. 2—Method The method previously described has been used to obtain a complete set of values for the susceptibilities of the alkaline halides. Although slight modifications have been made from time to time, the apparatus has remained, in essentials, the same as when used for the measurement of the susceptibilities of the sodium and potassium halides.

Temperature dependence of exciton peak energies in ZnS, ZnSe, and ZnTe epitaxial films

1999 ◽  
Vol 86 (8) ◽  
pp. 4403-4411 ◽  
Author(s):  
R. Pässler ◽  
E. Griebl ◽  
H. Riepl ◽  
G. Lautner ◽  
S. Bauer ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Epitaxial Films ◽  
Exciton Peak

Interplay of Lewis acidity, intramolecular O→Sn interactions and selectivity: organotin-functionalized crown ethers as ditopic hosts for sodium and potassium halides

2018 ◽  
Vol 54 (7) ◽  
pp. 739-742 ◽  
Author(s):  
Alain Charly Tagne Kuate ◽  
Muhammad Moazzam Naseer ◽  
Michael Lutter ◽  
Klaus Jurkschat
Keyword(s):  
Crown Ethers ◽  
Lewis Acidity ◽  
Sodium And Potassium ◽  
Potassium Halides

Not only ditopic complexation, but also selectivity has been realized by increasing the Lewis acidity of tin atom in organotin-functionalized crown ethers.

scholarly journals The role of enzyme dynamics and tunnelling in catalysing hydride transfer: studies of distal mutants of dihydrofolate reductase

2006 ◽  
Vol 361 (1472) ◽  
pp. 1307-1315 ◽  
Author(s):  
Lin Wang ◽  
Nina M Goodey ◽  
Stephen J Benkovic ◽  
Amnon Kohen
Keyword(s):  
Temperature Dependence ◽  
Dihydrofolate Reductase ◽  
Isotope Effects ◽  
Hydride Transfer ◽  
Activation Parameters ◽  
Physical Nature ◽  
Enzyme Dynamics ◽  
Temperature Dependences ◽  
Donor Acceptor ◽  
Significant Temperature

Residues M42 and G121 of Escherichia coli dihydrofolate reductase ( ec DHFR) are on opposite sides of the catalytic centre (15 and 19 Å away from it, respectively). Theoretical studies have suggested that these distal residues might be part of a dynamics network coupled to the reaction catalysed at the active site. The ec DHFR mutant G121V has been extensively studied and appeared to have a significant effect on rate, but only a mild effect on the nature of H-transfer. The present work examines the effect of M42W on the physical nature of the catalysed hydride transfer step. Intrinsic kinetic isotope effects (KIEs), their temperature dependence and activation parameters were studied. The findings presented here are in accordance with the environmentally coupled hydrogen tunnelling. In contrast to the wild-type (WT), fluctuations of the donor–acceptor distance were required, leading to a significant temperature dependence of KIEs and deflated intercepts. A comparison of M42W and G121V to the WT enzyme revealed that the reduced rates, the inflated primary KIEs and their temperature dependences resulted from an imperfect potential surface pre-arrangement relative to the WT enzyme. Apparently, the coupling of the enzyme's dynamics to the reaction coordinate was altered by the mutation, supporting the models in which dynamics of the whole protein is coupled to its catalysed chemistry.

Temperature dependence of heats of vaporization, saturated vapour pressures and cohesive energies for a group of amines

1979 ◽  
Vol 44 (12) ◽  
pp. 3521-3528 ◽  
Author(s):  
Vladimír Majer ◽  
Václav Svoboda ◽  
Josef Koubek ◽  
Jiří Pick
Keyword(s):  
Temperature Dependence ◽  
Saturated Vapour ◽  
Temperature Dependences ◽  
Experimental Values ◽  
Cohesive Energies ◽  
Heats Of Vaporization

The temperature dependences of heats of vaporization of propylamine, isopropylamine, butylamine, isobutylamine, sec-butylamine, cyclohexylamine, diethylamine and triethylamine and saturated vapour pressures of butylamine, isobutylamine, sec-butylamine and triethylamine were measured. The cohesive energies of amines studied in dependence on temperature were calculated from the experimental values.

scholarly journals Temperature dependence of the dielectric function and critical points of α-SnS from 27 to 350 K

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hoang Tung Nguyen ◽  
Van Long Le ◽  
Thi Minh Hai Nguyen ◽  
Tae Jung Kim ◽  
Xuan Au Nguyen ◽  
...  
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Dielectric Function ◽  
Spectral Energy ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Temperature Dependences ◽  
Exciton Effect ◽  
Bose Einstein ◽  
Temperature Gradient Method

Abstract We report the temperature dependence of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of biaxial α-SnS in the spectral energy region from 0.74 to 6.42 eV and temperatures from 27 to 350 K using spectroscopic ellipsometry. Bulk SnS was grown by temperature gradient method. Dielectric response functions were obtained using multilayer calculations to remove artifacts due to surface roughness. We observe sharpening and blue-shifting of CPs with decreasing temperature. A strong exciton effect is detected only in the armchair direction at low temperature. New CPs are observed at low temperature that cannot be detected at room temperature. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose–Einstein statistical factor and the temperature coefficient for describing the electron–phonon interaction.

scholarly journals Effect of Mechanical Load on Defects Level in Soft Ferrite Ceramics

2018 ◽  
Vol 186 ◽  
pp. 02010
Author(s):  
A.B. Petrova ◽  
A.V. Malyshev ◽  
A.P. Surzhikov
Keyword(s):  
Temperature Dependence ◽  
Curie Point ◽  
Room Temperature ◽  
Mechanical Load ◽  
Initial Permeability ◽  
Temperature Dependences ◽  
Four Levels ◽  
Magnetic Ring ◽  
Soft Ferrite ◽  
With Screws

The article presents the results of a study of the effect of mechanical load on the temperature dependence of the initial permeability of LiTiZn soft ferrite ceramics. Regimes of mechanical load were created by a steel non-magnetic ring with screws. In this work, four levels of mechanical load were investigated: without load, with 1, 2 and 3 screws. For obtaining temperature dependences and exclude the influence of prehistory on the initial permeability, the samples were heated to a temperature exceeding the Curie point by 50 degrees, after which they slowly cooled to room temperature. The defects level was determined by the ratio of the parameters β / α of the phenomenological expression, which describes the experimental temperature dependences. It is shown that as the mechanical load increases, the defects level of ferrite ceramics increases, and after load removing, it returns to its original level.

Temperature dependence of the resistance, impedance and capacitance of semitransparent PTB7-Th and PCBM sensor

2019 ◽  
Vol 33 (12) ◽  
pp. 1950110
Author(s):  
Muhammad Riaz ◽  
Khasan S. Karimov ◽  
Jameel-Un Nabi
Keyword(s):  
Light Intensity ◽  
Temperature Dependence ◽  
Temperature Sensor ◽  
Visual Control ◽  
Capacitance Measurement ◽  
Experimental Conditions ◽  
Temperature Resistance ◽  
Graphene Composite ◽  
Temperature Dependences ◽  
Resistance Coefficients

The temperature dependences of resistance, impedance and capacitance of semitransparent sensor having structure ITO/PTB7-Th:PC[Formula: see text]BM/Graphene composite (semisurface type) were investigated. The transparency of the sensor was 58–60%. The dependences of the resistance, impedance and capacitance at different frequencies 100 Hz, 1 kHz, 10 kHz, 100 kHz and 200 kHz and temperature in the range of 23.8–80[Formula: see text]C for the sensor were studied. It was observed that as the temperature increased from 23.8[Formula: see text]C to 80[Formula: see text]C, the resistance and impedance (at 1 kHz) of the samples decreased, on average, by a factor of 3.51 and 3.79, respectively. At same experimental conditions (1 kHz), the capacitances of the samples also decreased by a factor of 9.6. It was also noted that as frequency increased from 100 Hz to 200 kHz, the impedance of the sensor decreased by a factor of 21 and 12, at temperatures 24[Formula: see text]C and 58[Formula: see text]C, respectively. Under the same conditions, the capacitance decreased by a factor of 30 and 28, respectively. The temperature resistance coefficients were measured to be −1.31%/[Formula: see text]C, −1.30%/[Formula: see text]C, −1.27%/[Formula: see text]C, −0.84%/[Formula: see text]C, −0.72%/[Formula: see text]C and −0.33%/[Formula: see text]C for R, Z (100 Hz), Z (1 kHz), Z (10 kHz), Z (100 kHz) and Z (200 kHz), respectively. For capacitance measurement, the temperature capacitance coefficients were measured as −1.39%/[Formula: see text]C, −1.38%/[Formula: see text]C, −1.37%/[Formula: see text]C, −1.36%/[Formula: see text]C and −1.34%/[Formula: see text]C, respectively. The semitransparent PTB7-Th- and PC[Formula: see text]BM-based temperature sensor can be used for measurement of the temperature as a teaching aid in situations where visual control of illumination and light intensity is required.

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