bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Pressure on Diffusion in CS2 Organic Mixtures
Authors: Koeller R. C. , Drickamer H. G. 
Published: January 2005

Diffusion coefficients are presented as a function of pressure to 10 000 atmospheres for the following systems: 50 mol percent n−heptane−50 percent CS2 0∘−20∘−40∘;50 mol percent 2,4 dimethylpentane−50 percent CS2 20∘−40∘;50 mol percent toluene−50 percent CS2 20∘−40∘;50 mol percent methylcyclohexane−50 percent CS2 0∘−20∘−40∘;50 mol percent n−octane−50 percent CS2 20∘C;50 percent chlorobenzene−50 percent CS2 20∘−40∘;80 percent chlorobenzene−20 percent CS2 40∘;50 percent n−butanol−50 percent CS2 20∘−40∘;50 percent iso−butanol−50 percent CS2 20∘−40∘;using S35 tagged CS2.
The results are interpreted in terms of the activation volume, enthalpy, and entropy, and conclusions are drawn concerning the effect of pressure on the structure of the liquids.
On the Electrical Conductivity of Some Alkaline Earth Titanates
Authors: Weise E. K. , Lesk I. A. 
Published: January 2005

The compounds Mg2TiO4, MgTiO3, MgTi2O5, CaTiO3, SrTiO3, and BaTiO3 were prepared in crystalline form by reactions in the solid state. The rod-shaped samples were sintered in oxygen at 1450°C and reduced in hydrogen at temperatures from 560°C to 1400°C producing n type semiconductors. Resistivity values from 10−1 to 108Ω·cm at 25°C were obtained. Reductions of about 3 percent by weight could be given the most reduced magnesium titanates while the largest reduction obtainable in CaTiO3, SrTiO3, or BaTiO3 was less than 0.25 percent.
The logarithm of resistivity was plotted versus reciprocal absolute temperature and showed a linear dependence in most cases over a wide range of temperature and resistivity. The curves for BaTiO3 changed the slope abruptly at approximately 115°C, probably attributable to the crystal structure change at the Curie temperature, about 120°C.
The dependences of impurity activation energy and Fermi level on percent reduction were determined for the case of Mg2TiO4. The Biltz-Meyer rule, stating a linear relationship of impurity activation energy with resistivity at a reference temperature, was not obeyed over the large range of reductions obtained.
Electronic Conduction in Silicon Carbide
Authors: Kendall J. T. 
Published: January 2005

Pure silicon carbide was prepared by decomposition of the vapors of silicon tetrachloride and toluene on a hot carbon filament. Various n- and p-type impurity atoms were introduced by the addition of volatile metallic chlorides during the preparation. For the pure substance either n- or p-type crystals could be obtained by varying the ratio of the reaction constituents. The results show that semiconductivity in silicon carbide may be due either to nonstoichiometric proportions of silicon and carbon, or to the presence of impurity atoms, or (as probably occurs in the commercial product) to both circumstances simultaneously.
A theoretical model for electronic conduction in silicon carbide is proposed, which satisfactorily explains the magnitude of the low and high temperature activation energies observed, their different ratios in n- and p-type crystals, the occurrence of conduction at one of the disturbance energy levels, and the anomalous low Hall constant at low temperatures found in black but not in green silicon carbide. The model may be applicable to other semiconductors in which disturbance centers can give rise to electrons in unlocalized excited states.
Unified Orbital Theory of the Excited States of the Fluorine Molecule
Authors: Mueller Charles R. 
Published: January 2005

The unification of the atomic orbital and molecular orbital theories of the excited states of diatomic molecules is achieved by means of semi-localized orbitals. In particular the classification of the states of the fluorine molecule arising from the interaction of two fluorine atoms in their ground state is discussed.
Quantitative calculations are made for the 1Σg+ and 3Σu+ states and a comparison of the singlet-triplet separation energies and binding energies from the three methods is made. Both two electron and eighteen electron calculations are made. The better molecular orbital calculations give a lower triplet than a singlet state. In the eighteen electron calculation the atomic and semi-localized orbital methods coincide, and the 1Σg+ state is found to be the ground state.
The Photochemical Decomposition of Azomethane
Authors: Jones M. H. , Steacie E. W. R. 
Published: January 2005

The photolysis of azomethane has been investigated over the temperature range 24–190°C. The variation in the rates of production of nitrogen, methane, and ethane with absorbed intensity, azomethane concentration, and temperature may be accounted for quantitatively by the reactions CH3N=NCH3+hν→N2+2CH3CH3+CH3N=NCH3→CH4+CH2N=NCH3CH3+CH3→C2H6.
The quantum yield of nitrogen formation was found to be unity and independent of temperature. For the activation energy difference E2—½E3 a value of 7.6 kcal/mole was obtained. Evidence is cited for an association reaction between methyl radicals and azomethane. On the basis of an assumed mechanism, the activation energy of this process is 6.4 kcal/mole.
Infrared and Raman Spectra of Fluorinated Ethanes. VI. The Series CF3CH3, CF3CH2Cl, CF3CHCl2, and CF3CCl3
Authors: Nielsen J. Rud , Liang C. Y. , Smith D. C. 
Published: January 2005

The infrared spectra of gaseous CF3CH2Cl and CF3CHCl2 have been obtained in the range from 2 to 38μ, and the spectra of the liquids in the range from 2 to 22μ, with the aid of LiF, NaCl, KBr, and KRS−5 prisms. The Raman spectra of these compounds in the liquid state have been photographed with a three-prism glass spectrograph of linear dispersion 15A/mm at 4358A. Depolarization ratios were determined for most of the Raman bands.
All fundamental vibrational frequencies have been assigned; the spectra have been interpreted in detail, and thermodynamic functions have been calculated.
The Specific Heat of Crystalline Selenium at Low Temperatures
Authors: Desorbo Warren 
Published: January 2005

Studies on the low temperature specific heat of crystalline selenium have been extended down to 15°K. The data are compared with a calculation based on a one-dimensional-continuum model with which good agreement is shown to exist down to about 37°K. Below this temperature, deviations are described in terms of an anisotropic continuum which considers the ``interaction'' between atom chains.
The values of the thermodynamic functions, entropy, enthalpy, and free energy have been evaluated and tabulated at regular integral values of temperature up to 300°K. The entropy of crystalline selenium at 298.16°K is 10.15±0.05 cal/g-atom/deg, of which 0.22 was obtained by extrapolating below 15°K. For this extrapolation, the anisotropic-continuum model was used.
Some Observations on the Chemical Behavior of Iodine at Low Concentrations
Authors: Kahn Milton , Wahl Arthur C. 
Published: January 2005

An investigation has been made of the chemical forms assumed by I131 initially in the form of iodide ion at low concentration (the order of 10−7M) when it is oxidized under various conditions. Oxidation at room temperature in 1f sulfuric acid solution by dichromate ion or cerium(IV) results in the formation of I2 and three additional, unidentified, chemical fractions which are not readily exchangeable with I−, I2, or IO3−. Two of the unidentified fractions are extracted from aqueous sulfuric acid solution by organic solvents, one fraction being converted by aqueous sodium hydroxide to water-soluble forms exchangeable with I2. At least some of the unidentified fractions probably are the products of reactions between trace impurities, molecular or colloidal, and iodine in an oxidized reactive form such as HIO. These unidentified fractions are quite inert toward oxidation and reduction.
When iodide ion at low concentration is treated with a hot sulfuric acid solution of cerium(IV), the principal product is IO3−, or a species readily exchangeable with IO3−. The IO3− formed in this way is readily reduced at room temperature to I− by a sulfuric acid solution of iron (II).
A Theory of the Linear Viscoelastic Properties of Dilute Solutions of Coiling Polymers
Authors: Rouse Prince E. 
Published: January 2005

The necessary coordination of the motions of different parts of a polymer molecule is made the basis of a theory of the linear viscoelastic properties of dilute solutions of coiling polymers. This is accomplished by use of the concept of the submolecule, a portion of polymer chain long enough for the separation of its ends to approximate a Gaussian probability distribution. The configuration of a submolecule is specified in terms of the vector which corresponds to its end-to-end separation. The configuration of a molecule which contains N submolecules is described by the corresponding set of N vectors.
The action of a velocity gradient disturbs the distribution of configurations of the polymer molecules away from its equilibrium form, storing free energy in the system. The coordinated thermal motions of the segments cause the configurations to drift toward their equilibrium distribution. The coordination is taken into account by the mathematical requirement that motions of the atom which joins two submolecules change the configurations of both submolecules. By means of an orthogonal transformation of coordinates, the coordination of all the motions of the parts of a molecule is resolved into a series of modes. Each mode has a characteristic relaxation time. The theory produces equations by means of which the relaxation times, the components of the complex viscosity, and the components of the complex rigidity can be calculated from the steady flow viscosities of the solution and the solvent, the molecular weight and concentration of the polymer, and the absolute temperature.
Limitations of the theory may arise from the exclusion from consideration of (1) very rapid relaxation processes involving segments shorter than the submolecule and (2) the obstruction of the motion of a segment by other segments with which it happens to be in contact. Another possible cause of disagreement between the theory and experimental data is the polydispersity of any actual polymer; this factor is important because the calculated relaxation times increase rapidly with increasing molecular weight.
Determination of the Potential Constants of Ozone from Centrifugal Distortion Effects
Authors: Pierce Louis 
Published: January 2005

The microwave spectrum of O3 was reanalyzed to include the effect of centrifugal distortion. Using the Kivelson-Wilson energy expression for a semirigid rotor it was possible to fit eighteen rotational lines to within a mean deviation of ±1.4 Mc. The rotational constants determined in this manner are a=106 534.74 Mc, b=13 348.95 Mc, c=11 834.30 Mc. The four distortion constants predicted vibrational frequencies which differed by only four percent from the observed values.
A sensitive determination of the potential function was made by requiring it be compatible with both the observed infrared spectrum and the distortion frequency shifts derived from the direct analysis of the rotational spectrum. The resulting force constants are: fd=5.70×105 dyne cm−1, fα/d02=1.28×105 dyne cm−1, fdα/d0=0.332×105 dyne cm−1, fdd=1.52×105 dyne cm−1. The force constants were then used to calculate distortion constants for O16O18O16 and these in turn were used to analyze its rotational spectrum.
Emission of Vacuum Ultraviolet Radiation from the Acetylene-Oxygen and the Methane-Oxygen Reactions in Shock Waves
Authors: Kistiakowsky G. B. , Richards L. Willard 
Published: January 2005

The C2H2–O2 and CH4–O2 reactions were studied by observing the emission of vacuum ultraviolet radiation from shock waves in gas mixtures containing 85 to 99% Ar and with 2×10−6≤[O2]≤60×10−6 moles/l. In both reactions after an induction period of length ti, the emission intensity rises exponentially with a time constant τ and then decreases about as rapidly. For the C2H2–O2 reaction, emission predominantly in the wavelength range 1500&lt;λ&lt;1700 A was observed. It was estimated that one photon was emitted in this range per 3×104 C2H2 molecules passing through the reaction zone at 1840°K. The integrated emission intensity depends on the temperature as if the process producing it has an activation energy of 15 kcal/mole. In the range of conditions 0.65≤[O2]/[C2H2]≤3.6 and 1300≤T≤2200°K it was found that log10([O2]ti)  (mole  sec/l)=−10.57+17 100/4.58T. The data for τ from mixtures with 0.65≤[O2]/[C2H2]≤7.7 fit the expression log10([O2]τ)  (mole  sec/l)=−11.48+17 100/4.58T with a standard deviation of a factor of 1.4 in τ. In the first approximation the values of [O2]ti and [O2]τ are functions of temperature only. In lean mixtures, however, [O2]τ and especially [O2]ti are larger than the average. These results are explained in terms of a branching chain mechanism in which the reaction H+O2=OH+O plays the dominant role in controlling the rate.
The CH4–O2 reaction was studied in the range of conditions 0.5≤[O2]/[CH4]≤4.5 and 1800≤T≤2700°K. The emission intensities are an order of magnitude smaller and more strongly temperature dependent, τ is a factor of 2 or 3 larger, and ti is a factor of 20 larger at the low temperatures and a factor of 4 larger at the high temperatures than for the C2H2–O2 reaction. The kinetic implications of these findings are discussed.
Rates of Reaction of Hydrogen with Iodine. II
Authors: Sullivan John H. 
Published: January 2005

The rate of reaction of hydrogen with iodine was measured at 666.79° and 799.77°K. The elementary reactions were considered to be  ⇀   ↼H2+I2⇌2HI,            (1)  (2) I+H2⇌HI+H,            (3)  (4) H+I2⇌HI+I,            (5)  (6)     I2=2I,                  where the left-hand equation number applies when the reaction proceeds to the right and the right hand number when the reaction proceeds to the left.
Our previous measurements over a shorter and lower temperature range had given E4∼0 kcal and an apparent temperature dependence for k4/k5 which suggested a negative temperature coefficient for k5. The present more extensive and more precisely treated data show that k4/k5 is temperature independent and E4=0 kcal, E5=0 kcal. The specific rate [(mole/cc)−1 sec−1] of (3), which at 800°K accounts for about 95% of the HI production, is given by log(k3/T12)=12.55±0.07−(32 800±250)/4.575T. The close agreement of our rates with those calculated from data in the literature leads to the conclusion that the experimentally determined values of k4/k5 are equal to values of k4/k5 for thermal energy distributions of H atoms.
Rotational Freedom of Ammonium Ions and Methyl Groups by Cross-Section Measurements with Slow Neutrons
Authors: Rush J. J. , Taylor T. I. , Havens W. W. 
Published: January 2005

The slope Δσs/Δλn of a plot of the scattering cross section per proton vs the wavelength of subthermal neutrons is shown to increase with increasing freedom of rotation of ammonium ions. For ammonium iodide, the slope increases from 6.2 b/Å—H in phase II to 11.2 b/Å—H in phase I, where the ammonium ions are rotating relatively freely. Measurements on five liquid methylbenzenes indicate greater hindrance to rotation of methyl groups in o-xylene (slope=9.5±0.3 b/Å—H), than in toluene, m-xylene, p-xylene, and mesitylene (slopes=11.4±0.3 b/Å—H).
From an empirical plot of slopes vs barriers to rotation of ammonium ions in several ammonium salts, slopes of 5.5 and 5.8 b/Å—H for (NH4)2CrO4 and NH4CNS indicate a barrier of about 4 kcal mole−1 for both these salts, while a high slope of 13 b/Å—H for NH4ClO4 predicts a barrier of only about 0.1 to 0.2 kcal mole−1. Assuming a similar type curve for methyl groups, the barrier to rotation of the methyl groups in o-xylene is estimated to be about 1 kcal mole−1, and a value of 0.1 to 0.4 kcal mole−1 is predicted for the other methylbenzenes.
EPR Study of Tetracene Positive Ion
Authors: Hyde James S. , Brown Harmon W. 
Published: January 2005

The EPR response of tetracene positive ion formed by dissolving tetracene in concentrated sulfuric acid has been investigated in detail. The splittings of the hyperfine lines have been carefully measured and the spectrum analyzed. Relaxation processes (T1 and T2) have been investigated over a range of experimental conditions. At low temperatures anisotropic hyperfine interactions determine linewidths and result in asymmetric spectra. This asymmetric interaction differs for the various classes of protons and depends on the form of the hyperfine tensor for each class. A second broad resonance of integrated intensity equal to that of the tetracene positive ion has been detected. In one experiment deuterated sulfuric acid was used, and it was found that the deuterium exchanged with the tetracene protons.
Considerable attention has been paid to experimental techniques useful in investigating narrow line spectra. Both 100-kc field modulation, where modulation sidebands were encountered, and superheterodyne detection have been employed. Linewidths as narrow as 35 mG have been obtained.
d Orbitals in Compounds of Second-Row Elements. I. SF6
Authors: Craig D. P. , Zauli C. 
Published: January 2005

Optimum exponent values for 3s, 3p, and 3d orbitals of sulfur in SF6 have been calculated in an electrostatic approximation. The sulfur electrons are perturbed by fluorine potentials appropriate to self-consistent field wave functions for the fluorine orbitals, and the energy minimized with respect to wave-function exponents. The optimum values are k3s=2.0, k3p=1.6, and k3d=1.2, corresponding to expansion of 3s and 3p orbitals, and contraction of 3d, compared with free-atom values. The values are remarkably stable to changes in valence-orbital configurations as between SF6, S+F6−, S++F6=, and even S−F6+. They are also little affected by change in hybridization at fluorine, and should therefore be suitable for use in the construction of molecular wave functions.
Although the calculated energies include no exchange terms they are still of some interest. They suggest for example that the promotion energy to the configuration sp3d2 of sulfur (estimated to be 25–31 eV) can be compensated by the energy of molecule formation.
Primary Reactions in the Mercury-Photosensitized Decomposition of 1-Butyne, Propyne, and Acetylene at Low Pressures
Authors: Kebarle P. 
Published: January 2005

The mercury-photosensitized decomposition of 1-butyne, propyne, and acetylene was studied at very low pressures in a flow system attached to a mass spectrometer.
The primary decomposition of 1-butyne was found to proceed by the reactionsC4H6*→HC≡C–CH–CH3+H50%→HC≡C–CH2+CH3    25%→1,2 and 1,3 butadiene.7%
The primary decomposition of propyne was C3H4*→HC≡C–CH2+H80%→allene.15%
The presence of C2H radicals was detected in the decomposition of acetylene. These probably originate from the primary decomposition. The primary quantum yield for acetylene appears very much lower than that of the butyne and propyne. It is concluded that acetylene forms an excited molecule, but that the primary decomposition does not necessarily occur by this process but from reactions involving the formation of HgH and HgC2H.
New Theorem in the Classical Ensemble Theory
Authors: Albertoni S. , Bocchieri P. , Loinger A. 
Published: January 2005

In the framework of the classical ensemble theory a theorem is proved which is sufficient to justify the classical statistical mechanics.
Our result can be stated as follows. Let us consider a fixed and otherwise arbitrary subdivision in cells Iν (ν = 1, 2, …, N) of the energy shell I of an isolated dynamical system: Having introduced a suitable definition of functional average, we prove that for ``almost all'' the initial Liouville density functions ρ(p′,q′; 0) we have lim lim T→∞1T ∫ 0Tdt{[ ∫ Iνρ(p′,q′;t)dp′dq′−σνσ]2}=0,where σν and σ are the measures of Iν and I, respectively. The unitarity of the Koopman-von Neumann time-evolution operator is the only dynamical property needed to establish this theorem. On the basis of our result, it can be shown that systems with very many degrees of freedom satisfy the laws of statistical mechanics.
Quantization of Fields with Infinite-Dimensional Invariance Groups
Authors: DeWitt Bryce S. 
Published: January 2005

A general approach to the problems of quantizing fields which have infinite-dimensional invariance groups is given. Space and time are treated on a completely equal footing. A Poisson bracket is defined by means of Green's functions, independently of the discovery or recognition of canonical variables, and is shown to satisfy all the usual identities. In accordance with the measurement theoretical foundations of the quantum theory, the Poisson bracket (i.e., commutator) is defined only for physically measurable group invariants. The Green's functions give a direct description of the propagation of small disturbances arising from a pair of mutually interfering measurements.
In order to establish a correspondence between this approach and conventional canonical theory, a motivation for the adopted definition of the Poisson bracket is outlined with the aid of the fundamental theorem of canonical transformation theory. The rest of the discussion is logically independent of this, however. The general theory of ``wave operators'' and their associated Green's functions is briefly reviewed. Specific details connected with the group theoretical side of the theory are handled in such a way that problems of constraints are completely avoided. In the last section the general method is applied to the Yang-Mills field, as a nontrivial example. The problem of factor ordering is not studied.
A Problem of Analytic Completion Related to the Jost-Lehmann-Dyson Formula
Authors: Bros J. , Messiah A. , Stora R. 
Published: January 2005

One considers functions of a complex four-vector Q which are analytic in the domain formed by: (a) The future tube: ImQ in the future light-cone. (b) The past tube: ImQ in the past light-cone. (c) A complex neighborhood of a domain R of real Q space limited by two space-like surfaces.
It is shown, by using techniques pertaining to the theory of analytic functions of several complex variables, that all such functions can be analytically continued in a larger domain which coincides with the one predicted by the Jost-Lehmann-Dyson formula.
Field-Theory Analogs of the Lagrange and Poincaré Invariants
Authors: Sturrock P. A. 
Published: January 2005

The Lagrange differential invariant and the Poincaré integral invariant of classical dynamics have as their analogs in Lagrangian field theory a ``differential divergence-free vector'' and an ``integral divergence-free vector.''
The former, which is expressible as a divergence-free vector-bracket expression, may be used to derive conservation relations associated with the transformation properties of a given system. It is not necessary that these transformations should be infinitesimal; by way of example, conservation theorems are established for systems which are periodic and for systems which are invariant under spatial inversion. The differential divergence-free vector may also be used to establish reciprocity and orthogonality relations: simple examples which are here discussed are Betti's reciprocal theorem of elasticity and Lorentz's reciprocal relation of electromagnetic theory. An extended form of the differential divergence-free vector allows for variation not only of the dependent variables but also of the independent variables.
The integral divergence-free vector associates a conserved quantity with any closed one-parameter family of solutions of the field equations. As examples, we derive the ``equation of conservation of probability'' of quantum mechanics, and a classical form of the relation between the momentum and wave vectors for a plane wave in a propagating medium.
The theorem of classical dynamics relating a complete set of Poisson brackets to a complete set of Lagrange brackets cannot be extended to the present formalism. The formula which represents the obvious extension of the classical formula for the Poisson bracket is of no interest since it can be shown not to be canonically invariant.