Chemical kinetics and thermodynamics of tin ionization in H2-O2-N2 flames and the proton affinity of SnO

1998 ◽  
Vol 76 (10) ◽  
pp. 1437-1446 ◽  
Author(s):  
John M Goodings ◽  
QingFeng Chen
Keyword(s):  
Equilibrium Constant ◽  
Proton Affinity ◽  
Rate Constant ◽  
Detailed Balance ◽  
Zero Point ◽  
Recombination Coefficient ◽  
Published Data ◽  
Free Electrons ◽  
Flame Ionization ◽  
Good Agreement

A small amount (<10-6 mol fraction) of tin was introduced into five, fuel-rich, H2-O2-N2 flames in the temperature range 1820-2400 K at atmospheric pressure. Ions in a flame were observed by sampling the flame along its axis through a nozzle into a mass spectrometer. The major neutral tin species in these flames were SnO (>97%) and Sn (<3%). The principal tin ions observed were SnOH+ and Sn+. Thermodynamic functions for SnOH+, Sn+, SnO, and Sn were calculated by statistical mechanics using published data from ab initio calculations and spectroscopy. The SnOH+ ion was formed initially by proton transfer to SnO by H3O+, a natural flame ion, with which it is in equilibrium. It was also produced by chemi-ionization of SnO reacting with H; SnOH+ rapidly equilibrates with Sn+. Ion ratio measurements of SnOH+/H3O+ led to the proton affinity PA°298 (SnO) = 911 ± 21 kJ mol -1 (218 ± 5 kcal mol-1). A calculated equilibrium constant provided the SnOH+/Sn+ ion ratio. When electron-ion recombination of SnOH+ with free electrons was made dominant by the addition of CH4 and K, the measured recombination coefficient of SnOH+ was (0.116 ± 0.065)T-(1.66±0.16) cm3 molecule-1 s-1; the temperature dependence is in good agreement with the T-1.5 dependence predicted by simple theory. The rate constant for chemi-ionization could not be measured due to impurity ions from potassium and sodium, but the equilibrium constant for chemi-ionization/recombination was calculated to be 0.004 863 exp (-52 070/T). Assuming detailed balance and the experimental recombination coefficient, the relatively small rate constant for chemi-ionization was given by 3.27 × 10-10 exp (-48 630/T) cm3 molecule-1 s-1. Finally, calculated values were obtained for the bond energy D°0(HO-Sn+) = 408 ± 21 kJ mol-1, and the standard zero-point enthalpy of formation deltafH°0(SnOH+) = 637 ± 21 kJ mol-1.Key words: flame ionization, chemi-ionization, proton affinity, mass spectrometry, tin.

Kinetics of oxidation of Cu(I) complexes of cysteine and penicillamine: nature of intermediates and reactants at pH 10.0

1989 ◽  
Vol 67 (4) ◽  
pp. 736-745 ◽  
Author(s):  
Stephen P. Mezyk ◽  
David A. Armstrong
Keyword(s):  
Equilibrium Constant ◽  
Rate Constant ◽  
Rate Constants ◽  
Slow Component ◽  
Mixed Valence ◽  
Planar Geometry ◽  
Published Data ◽  
Diffusion Controlled ◽  
Square Planar ◽  
Thiolate Ligand

The Cu(I)•L2 complex with cysteine ligands at total Cu(I) concentrations of 10–30 μM was shown to be oxidised by cysteinyl radicals (RS•) with a diffusion-controlled rate constant k11a = 1.8 × 109 M−1 s−1. The corresponding reaction with the cysteine disulphide anion (RS•—SR−) proceeded at a slower rate, k11b = 2.7 × 108 M−1s−1. At higher Cu(I) concentrations, a slow and a fast component of absorption growth was observed. The slow component rate was independent of Cu(I) concentration, but it became more intense as the Cu(I) concentration rose. The yields and kinetic data were shown to be consistent with the presence of an equilibrium between the Cu(I)•L2 species and a second Cu(I) complex, Cu(I)2•L3, with an equilibrium constant of K1 = 162.[Formula: see text]This finding is consistent with the earlier work of Bagiyan etal. The rate constant of the oxidation of Cu(I)2•L3 by the cysteinyl radical was k12 = 1.0 × 109 M−1 s−1. Similar results were obtained with penicillamine, except the rate constants and equilibrium constant were smaller, (k11a = 4.5 × 108 M−1 s−1, k11b < 2 × 108 M−1 s−1, k12 = 5.5 × 108 M−1 s−1 and K1 = 113). This was attributed to the presence of the β-methyl groups in penicillamine, which exert a large steric effect.The ultraviolet spectra of the long-lived products, which are stable on a millisecond timescale, was consistent with a Cu(II)•L2 structure with a square planar geometry. The oxidation of the Cu(I)2.L3 species proceeded via intermediates, which relaxed to the final product spectra with rate constants of k13b = 2.6 and 1.1 × 104 s−1 for cysteine and penicillamine, respectively. Comparison of the spectra of the intermediates with published data showed that they were consistent with the presence of a bridging thiolate ligand between Cu(I) and Cu(II). Keywords: oxidation, copper, mixed valence, cysteine, penicillamine, complexation.

scholarly journals Structural elastic and thermal properties of SrxCd1−x O mixed compounds — a theoretical approach

2014 ◽  
Vol 32 (3) ◽  
pp. 350-357
Author(s):  
Purvee Bhardwaj
Keyword(s):  
Phase Transition ◽  
Vibrational Energy ◽  
Zero Point ◽  
Study Phase ◽  
Energy Effect ◽  
Phase Transition Pressure ◽  
Vegard’S Law ◽  
Extended Interaction ◽  
Experimental Values ◽  
Good Agreement

AbstractIn the present paper, the structural and mechanical properties of alkaline earth oxides mixed compound SrxCd1−x O (0 ≤ x ≤ 1) under high pressure have been reported. An extended interaction potential (EIP) model, including the zero point vibrational energy effect, has been developed for this study. Phase transition pressures are associated with a sudden collapse in volume. Phase transition pressure and associated volume collapses [ΔV (Pt)/V(0)] calculated from this approach are in good agreement with the experimental values for the parent compounds (x = 0 and x = 1). The results for the mixed crystal counterparts are also in fair agreement with experimental data generated from the application of Vegard’s law to the data for the parent compounds.

Doppler-Shifted Cyclotron Resonance in Thin Metal Films

1972 ◽  
Vol 50 (18) ◽  
pp. 2122-2137
Author(s):  
R. Turner ◽  
J. F. Cochran
Keyword(s):  
Magnetic Field ◽  
Metal Films ◽  
Thin Metal Film ◽  
Thin Metal ◽  
Free Electrons ◽  
Fermi Surfaces ◽  
First Order ◽  
Simple Quantum ◽  
The Magnetic Field ◽  
Good Agreement

According to Van Gelder the microwave absorption by a thin metal film in the presence of a static magnetic field normal to the film contains a series of peaks as the magnetic field is varied. In the present paper it is argued that these peaks correspond to Doppler-shifted cyclotron resonances of the carriers in the metal due to the quantization of electron momenta normal to the plane of the film. A simple quantum calculation is presented for the case of free electrons where the film is thin enough that to first order the microwave fields within are determined only by the boundary conditions and Maxwell's equations. The quantum expression is in good agreement with the absorption calculated using semiclassical arguments which can be readily extended to more complicated Fermi surfaces.

Analysis of Thermal Variation of Length and Refractive Index of Lead Fluoride to Study its Optical Properties

1989 ◽  
Vol 172 ◽  
Author(s):  
T. S. Aurora ◽  
D. O. Pederson ◽  
S. M. Day
Keyword(s):  
Refractive Index ◽  
Room Temperature ◽  
Linear Thermal Expansion ◽  
Small Variation ◽  
Published Data ◽  
Thermal Variation ◽  
Lead Fluoride ◽  
Superionic Phase Transition ◽  
Lorenz Relation ◽  
Good Agreement

AbstractLinear thermal expansion and refractive index variation have been measured in lead fluoride with a laser interferometer as a function of temperature. Data has been analyzed using the Lorentz-Lorenz relation. Molecular polarizability, band gap, variation of refractive index with density, and strain-polarizability parameter have been studied as a function of temperature. They exhibit a small variation with temperature except near the superionic phase transition where the variation appears to be more pronounced. The results are in good agreement with the published data near room temperature.

scholarly journals The Distribution of Larvae of Randomly Moving Insects

1961 ◽  
Vol 14 (4) ◽  
pp. 598 ◽  
Author(s):  
EJ Williams
Keyword(s):  
Normal Distribution ◽  
Bessel Function ◽  
Theoretical Distribution ◽  
Frequency Function ◽  
Published Data ◽  
Modified Bessel Function ◽  
Theoretical Conclusion ◽  
Constant Rate ◽  
Spatially Distributed ◽  
Good Agreement

Though randomly moving insects released from a central point in a uniform environment are often found to be distributed according to a circular normal distribution, their larvae will not conform to this distribution. When such insects lay at a constant rate and are subject to constant mortality, their larvae are found to be spatially distributed according to a highly peaked frequency function, depending on the modified Bessel function of the second kind. This theoretical conclusion is in good agreement with published data. Some of the properties of the theoretical distribution are discussed.

Analytical approach for transient photoconductivity in undoped a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
M. Goerlitzer ◽  
P. Pipoz ◽  
H. Beck ◽  
N. Wyrsch ◽  
A. V. Shah
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Analytical Approach ◽  
Room Temperature ◽  
Free Electrons ◽  
Recombination Time ◽  
Sample Quality ◽  
Transient Photoconductivity ◽  
Light Intensities ◽  
Good Agreement

ABSTRACTTransient photoconductive response of undoped a-Si:H has been studied; the changes were analysed between two slightly different steady-state illumination conditions, at room temperature. A theoretical model is developed to describe transient photoconductivity; it yields good agreement with the measured curves for a whole range of light intensities. Numerical evaluations allows one to extract the recombination time of electrons. Comparison with steady-state photoconductivity yields a band mobility of free electrons between 0.1 and 6 cm2V−1s−1, depending upon sample quality.

Comparative Numerical Simulation of Natural Convection in a Porous Horizontal Cylindrical Annulus

2014 ◽  
Vol 670-671 ◽  
pp. 613-616 ◽  
Author(s):  
Jabrane Belabid ◽  
Abdelkhalek Cheddadi
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Saturated Porous Medium ◽  
Published Data ◽  
Governing Equations ◽  
Alternating Direction Implicit ◽  
Cylindrical Annulus ◽  
Alternating Direction ◽  
Concentric Cylinders ◽  
Good Agreement

This work presents a numerical study of the natural convection in a saturated porous medium bounded by two horizontal concentric cylinders. The governing equations (in the stream function and temperature formulation) were solved using the ADI (Alternating Direction Implicit) method and the Samarskii-Andreev scheme. A comparison between the two methods is conducted. In both cases, the results obtained for the heat transfer rate given by the Nusselt number are in a good agreement with the available published data.

A Study on the Low Cycle Fatigue Behavior of the Steel for Shipbuilding Industry

2005 ◽  
Vol 297-300 ◽  
pp. 10-15 ◽  
Author(s):  
Kyung Su Kim ◽  
Byung Ok Kim ◽  
Young Kwan Kim ◽  
Chang Hwan Lee ◽  
Sung Won Lee
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Published Data ◽  
Cycle Fatigue ◽  
Maritime Industry ◽  
Shipbuilding Industry ◽  
Design Procedures ◽  
Calculation Results ◽  
Good Agreement

Recently, most of fatigue cracks in ship structures are reported within a few years after delivery. This type of fatigue characteristics cannot be explained adequately by the S-N curve based on high cycle fatigue. Calculation results under critical loading conditions reveal that stress magnitude higher than three times the yield stress occurs at some critical locations. It shows the fatigue cracks are related to low cycle fatigue. But the existing recommended design procedures in maritime industry do not properly cover low cycle fatigue problems. This work represents the first step in an effort to develop a design code that addresses low cycle fatigue problems. Low cycle fatigue test for uniform round specimen made of base/weld metal and for cruciform welded joint are carried out under constant amplitude alternating load, controlled by strain. Strain-cycle curves for the base metal and weld joints show good agreement with published data as well as some code recommended design curves.

The Aldol Condensation of Acetaldehyde: the Equilibrium Constant for the Reaction and the Rate Constant for the Hydroxide Catalyzed RetroAldol Reaction

1974 ◽  
Vol 52 (11) ◽  
pp. 2037-2040 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Equilibrium Constant ◽  
Rate Constant ◽  
Aldol Condensation ◽  
Aldol Reaction ◽  
Enthalpy Change

An indirect thermochemical estimate of the equilibrium constant for the aldol condensation of acetaldehyde suggested that this reaction was much less irreversible than has been believed. The rate of the hydroxide catalyzed retroaldol reaction has been measured; k21 = 2.8 × 10−3 M−1 s−1 at 25°, so that the equilibrium constant is 4.0 × 102 M−1. The γ value for acetaldehyde as addend is 0.40. The enthalpy change for the aldol reaction is −9.84 kcal/mol.

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