bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small-Angle X-Ray Scattering from the Low Carbon Paraffins
Authors: Buttrey John W. 
Published: January 2005

The small angle x-ray scattering patterns from the four lowest carbon normal paraffins: methane, ethane, propane, and butane have been determined near the critical temperature using a single crystal spectrometer. Monochromatization was obtained with a rocksalt crystal reflecting the Kα lines of copper, and detection was with a Geiger counter.
The data have been analyzed to show a qualitative confirmation of the well-known Zernike-Prins relation between the x-ray intensity scattered at small angles and the isothermal compressibility. A study of a ``particle size'' corresponding to the size of regions of statistical density fluctuation near the critical temperature fails to show a detectable difference in the size of these regions for different thermodynamic conditions of the same hydrocarbon or for different hydrocarbons at roughly equivalent conditions, but indicates an increase in the number of such regions as the transition between liquid and vapor is approached from either the vapor or the liquid.
Distribution of Electrons in the Water Molecule
Authors: Banyard K. E. , March N. H. 
Published: January 2005

The electron distribution in H2O is examined using the wave functions of Ellison and Shull (ES) and the density averaged over all orientations about the O nucleus is computed. This is compared with that calculated from the simple central field wave functions used previously by the authors in the interpretation of x-ray scattering results, and there is good agreement between these densities. In addition to the s term in the expansion of the ES density in spherical harmonics, the p term is also exhibited explicitly; it is this which determines the dipole moment of the molecule.
In the second part of the paper a general method is developed for the calculation of the x-ray scattering by a gas of nonspherical molecules. Using this formulation together with the ES density for H2O it is shown that the p term has only a very small effect on the scattering factor. The results using the ES density are in good agreement with those obtained previously and with experiment.
Theory of Multi-Component Fluid Mixtures. I. Statistical Order-Disorder Analysis in Multi-Component Fluid Mixtures
Authors: Salsburg Zevi W. , Wojtowicz Peter J. , Kirkwood John G. 
Published: January 2005

Recent theories of solutions (Prigogine and co-workers; Scott) have been developed without specific reference to a molecular model by the use of a corresponding states procedure which relates the properties of the solution to the properties of one of the pure components. These considerations have been based exclusively upon intuitive postulates which have been formulated by analogy from previous ``cell'' theories of solutions.
The basis for a corresponding states treatment is examined in a rigorous manner by the use of statistical mechanics. A general method is given for reducing the multi-component configurational partition function to a form peculiar to a system of one component. Two types of approximations to the rigorous theory that are amenable to numerical calculations are developed on a strictly mathematical basis, and are used to estimate the magnitudes of the correction terms to a corresponding states analysis.
Calculation of Energy Levels for Internal Torsion and Over-All Rotation. II. CH3CHO Type Molecules; Acetaldehyde Spectra
Authors: Kilb R. W. , Lin Chun Chia , Wilson E. B. 
Published: January 2005

Methods are described for the calculation of energy levels for the over-all rotation and internal torsion of molecules with a plane of symmetry and one symmetric internal rotor. Typical examples are CH3CHO, CH3SiH2D, and CH3OH. Analysis of the microwave spectra of CH3CHO, CD3CDO, CD3CHO, CH2DCHO, CHD2CHO, C13H3CHO, CH3C13HO, C13H3C13HO, and CH3CHO18 yields V3=1162, 1151, 1143±30 cal, and V6&lt;100 cal, respectively, for the first three isotopic species, where the barrier to internal rotation is V=V3(1—cos3α)/2+V6(1—cos6α)/2. The aldehyde oxygen was found to be opposite one of the methyl hydrogens in the equilibrium orientation of the methyl group. The measured moments of inertia of the nine isotopic species lead to a structure with the parameters
Methyl group: C–H=1.086 A C–D=1.088 H–C–H=108°16′ D–C–D=108°32′ C–C=1.501
Aldehyde: C–H=1.114 C=0=1.216 C–C–H=117°29′ C–C–O=123°55′
The Stark effect gave a dipole moment of 2.69 debyes.
Microwave Spectrum, Structure, and Internal Barrier of Methyl Silane
Authors: Kilb R. W. , Pierce Louis 
Published: January 2005

The microwave spectrum of methyl silane has been reinvestigated. Seven symmetric top and ten asymmetric top isotopic species have been studied. These molecules, together with the six symmetric tops studied by Lide and Coles, yield a total of thirty-three rotational constants. A least-squares analysis of these constants gave the following structural parameters:     rSiC=1.8668±0.0005 A,    rCH=1.093±0.005 A,    rSiH=1.485±0.005 A,∠HCH=107∘40′±30′,∠HSiH=108∘15′±30′.Analysis of the spectra of the isotopic species CH2D–SiH2D and CH2D–SiHD2 shows conclusively that methyl silane in its equilibrium configuration has the methyl group staggered with respect to the silyl group.
Certain transitions in the asymmetric top isotopic species, e.g., CH3SiH2D, are split into doublets because of coupling of over-all and internal rotation. These splittings were used to determine the barrier to internal rotation. The form of the potential hindering internal rotation was taken to be V = ½V3(1 — cos3α)+½V6(1 — cos6α), giving the result V3 = 1700±100 cal, V6∼0–150 cal. This is in reasonable agreement with the result of Kivelson's analysis of the J = 0→1 torsional satellites of CH3–SiH3.
Concentration Dependence of Diffusion Coefficient: Analysis of Skewed Diffusion Curve
Authors: Nishijima Yasunori , Oster Gerald 
Published: January 2005

Skewed diffusion curves are analytically treated in terms of the Gram-Charlier expansion applied to the Boltzmann equation. The concentration dependence of the diffusion coefficients can be expressed in terms of moments of the diffusion curves.
When the diffusion coefficient is linearly dependent on concentration, the slope is expressed in terms of three parameters of the diffusion curve, namely: (1) the third moment, (2) the height at the initial boundary, and (3) the average diffusion coefficient.
Crystalline Field Selection Rules: The Effect of Vibration-Electronic Interaction
Authors: Satten Robert A. 
Published: January 2005

It is pointed out that the selection rules for stationary ions in crystalline electric fields are violated for many transitions in the neodymium bromate and ethylsulfate absorption spectra, making it impossible consistently to assign irreducible representations to crystalline levels. The appearance of spectral lines not obeying the usual crystalline field selection rules is assumed to be due to the interaction of the vibration of the rare earth ion or ion-water complex with its electronic motion about the nucleus. The theory of such an interaction is presented and selection rules derived for D3h, C3v, D3, C3, and C3h local symmetries about the equilibrium position. It is found that the vibration interaction can account for the type of violations seen and with intensities that are probably comparable to some allowed pure electronic transitions.
A satellite structure, which is a consequence of the vibration-electronic interaction, is predicted for all spectral lines except transitions between upper and lower J = ½ or J = 0 levels. Such a structure may be manifested experimentally as a high-temperature ``line width.'' Such satellites of pure electronic transitions should obey the same selection rules and have the same Zeeman effect as the ``parent'' pure electronic transition. The intensity of the individual satellite components of a line does not depend on the strength of the vibration-electronic interaction but only on the Boltzmann factors of their lower state and on the intensity of the parent line.
Burning of a Liquid Droplet. III. Conductive Heat Transfer within the Condensed Phase during Combustion
Authors: Wise Henry , Ablow C. M. 
Published: January 2005

The problem of internal heating by conduction during the combustion of a spherical fuel droplet is examined.
The analysis indicates that the temperature pattern within such a system is governed by the dimensionless ratio of burning rate coefficient to thermal diffusivity of the liquid. During combustion the temperature in the center of the droplet may closely approach the surface temperature for liquid fuels commonly employed in propulsion. Such an increase in temperature may lead to thermal degradation and carbon formation observed during the combustion of certain organic compounds.
Vibrational Spectrum and Structure of Metal-Cyanide Complexes in the Solid State. II. KAu(CN)2
Authors: Jones Llewellyn H. 
Published: January 2005

The infrared spectra of solid KAu(CN)2 and the mono- and di-substituted C13 and N15 species have been observed. The seven fundamental vibrations of the linear, symmetrical Au(CN)2— ion have been assigned at 2160, 452, 2141, 427, 305, 368, and 100 cm—1.
From the observed frequencies of the normal and isotopic species, force constants were calculated for two possible structures: N–C–Au–C–N and C–N–Au–N–C. It is shown that the latter structure gives unreasonably large values for the CN stretching force constant and the CN, AuN interaction constant, and that therefore the cyanides are most likely bound to the gold through the carbon atoms.
Reaction of Diborane with Hg 6(3P1) Atoms
Authors: Hirata T. , Gunning H. E. 
Published: January 2005

An investigation has been made of the decomposition of diborane, photosensitized by mercury-6(3P1) atoms under static conditions, at 29.30°C.
The quantum yields of pressure increase and product formation have been found to be independent of substrate pressure in the complete quenching region. For runs of one hour duration at an incident light intensity of 2.5×10—6 einstein/min, the quantum yields are 0.50±0.02 for hydrogen, 0.25±0.02 for tetraborane, 0.02±0.02 pentaborane and 0.070±0.002 for pressure increase. The mean quantum yields of hydrogen and tetraborane formation were found to decrease with increasing duration of exposure during the first half-hour of irradiation. Constant values were reached after 30–45 min of exposure. The ratio of the rates of hydrogen to tetraborane formation was found to maintain a value of two, independent of substrate pressure and duration of exposure, for runs exceeding five minutes in duration. Extensive decomposition was found to lead to solid products.
A mechanism is proposed involving the primary scission of the B–H bond which accounts qualitatively for the observed characteristics of the reaction. The resemblance between ethane and diborane with respect to their behavior toward Hg 6(3P1) atoms is pointed out.
Scattering of High Velocity Neutral Particles. X. He–N2; A–N2. The N2–N2 Interaction
Authors: Amdur I. , Mason E. A. , Jordan J. E. 
Published: January 2005

Total collision cross sections have been measured for helium atoms with energies between 500 and 2100 ev, and for argon atoms with the same energies, scattered in room temperature nitrogen. The results have been analyzed to obtain the average potential between a helium atom and a nitrogen molecule, 〈V(r)〉Av=1.19×10−10/r7.06 ergs,for r between 1.79 A and 2.29 A, and the average potential between an argon atom and a nitrogen molecule, 〈V(r)〉Av=1.21×10−9/r7.78 ergs,for r between 2.28 A and 2.83 A.
A procedure which takes into account the noncoincidence of the center of mass and the centers of force in the N2 molecule has been developed for expressing these average atom-molecule interactions as functions of the atom-atom potential between the beam particle and either of the nitrogen atoms. These interatomic potentials have been combined with potentials previously determined for He–He and A–A to obtain a hypothetical potential between two nitrogen atoms in different N2 molecules. The following average intermolecular potential for the N2–N2 system has been obtained by averaging such N–N interactions over all mutual orientations of the two N2 molecules: 〈V(r)〉Av=9.54×10−10/r7.27 ergs,for r between 2.43 A and 3.07 A. This N2–N2 potential is consistent with one valid at larger separation distances, which has been derived from measurements on gaseous viscosity at high temperatures.
Exchange of Ammonia between Metal-Ammine Cations and Solvent in Liquid Ammonia
Authors: Wiesendanger Hans U. D. , Jones Walter H. , Garner Clifford S. 
Published: January 2005

The rates of exchange of NH3 between solvent liquid ammonia and ligand ammonia in five metal-ammine cations have been measured with N15 labeling. Reactants were separated by distilling off the solvent ammonia. Within the exchange times of 0.5, 3, and 11 minutes, respectively, exchange is complete for Ag(NH3)2+, Cu(NH3)4+2, and Ni(NH3)6+2 at concentrations of ca 0.01 f and in the dark at —33.5°C. Based on a single run, exchange with 0.013 f Cr(NH3)6+3 in the dark at 25.0°C exhibited a good McKay plot with a half-time of 1500 minutes, corresponding to a bimolecular rate constant k=1.3×10—6 l·mole—1·sec—1. Exchange with Co(NH3)6+3 was shown to be slow (half-times of the order of several hours at 0.002–0.005 f in the dark at 25.0°C), but reproducible results were not obtained. All complexes were studied as the nitrates. The observed slow exchange for Cr(NH3)6+3 and Co(NH3)6+3 is consistent with their classification as ``inert inner-orbital'' complexes.
Exchange of N15 between NO3— and solvent liquid ammonia, including exchange during the hot NaOH treatment used to distill off the ammonia, is less than 3% at 0.05 f NO3— and 25°C.
Reactions of Alkoxy Radicals. I. Photolysis of Methyl Acetate
Authors: Wijnen M. H. J. 
Published: January 2005

The photolysis of methyl acetate has been investigated in the vapor phase over the temperature range 29 to 217°C at varying light intensities and initial pressures. The main primary step is a split of the ester molecule into CH3CO and CH3O radicals.
The following reactions involving methoxy radicals have been established: CH3O+CH3→CH2O+CH4CH3O+CH3→CH3OCH3CH3O+CH3COOCH3→CH3OH+CH2COOCH3.As activation energies for reactions (A) and (C) were obtained EA≤1.5 kcal and EC≃4.5 kcal. No information could be obtained regarding the extent to which reaction (D) occurred. 2 CH3O→CH3OH+CH2O.An activation energy of 10 kcal was obtained for the abstraction of a hydrogen atom from methyl acetate by methyl radicals.
Reactions of Nitrogen Atoms. I. Oxygen and Oxides of Nitrogen
Authors: Kistiakowsky G. B. , Volpi G. G. 
Published: January 2005

Several reactions of nitrogen atoms have been investigated in a low-pressure flow system, using the principle of a ``stirred reactor'' and a mass spectrometer for the determination of steady-state concentrations.
The elementary processes which have been definitely demonstrated to occur and their rate constants are as follows: N+NO=N2+Ok1≥4×1011 cc mole−1sec−1(1)N=O2=NO+Ok8=2×1012×exp(−6200/RT) cc mole−1sec−1(8)N+NO2=N2O+O10−2k1&lt;k9&lt;10k1(10)O+NO=NO2k3≥1013 cc mole−1sec−1(3)O+NO2=O2+NOk6≥1012 cc mole−1sec−1.(6)Unless indicated, the rate constants are at room temperature.
The rate constant of nitrogen atom reaction with nitrous oxide is less than 108 cc mole—1 sec—1 at 280°; that of oxygen atoms is less than 2×108 at room temperature, neither having been observed to occur.
Nitrogen atoms probably react with nitrogen dioxide also by a different mechanism than (10), yielding 2NO and/or N2+O2, at a rate which is competitive with (10). Nitrous oxide is probably formed also by another mechanism, which does not involve nitrogen atoms and may well be the reaction of vibrationally excited nitric oxide with nitrogen dioxide.
The accommodation coefficient of glass walls, treated with phosphoric acid, for the recombination of oxygen atoms, has been determined as 10—4 in one reactor and is larger than this in another.
Intensity of the Symmetry-Forbidden Electronic Absorption Band of Formaldehyde
Authors: Pople J. A. , Sidman J. W. 
Published: January 2005

The weak bands of formaldehyde extending from λ3500 A to λ2300 A are normally assigned to a 1A2←1A1, n→π transition (C2ν symmetry) which is forbidden by electronic selection rules. The present paper gives a quantitative theoretical discussion of the total intensity of these bands in each of the three directions of polarization. Using approximate wave functions for the various electronic states involved, the theory shows that the intensity of the perpendicular bands can be accounted for by vibrationally-induced mixing of excited electronic states. The calculated total intensity due to this mechanism is f=3×10—4. It is predicted that most of this intensity is produced by the out-of-plane bending vibration and is consequently polarized perpendicular to the C–O axis and in the molecular plane (B1 polarized). The contribution due to in-plane vibrations (CH2 wagging and antisymmetric C–H stretch), which would be polarized perpendicular to the molecular plane (B2 polarized), is predicted to be much weaker. This is in agreement with experiment.
The weak parallel bands that have been observed cannot be interpreted in terms of vibrational-electronic interaction. It is suggested that these derive their intensity by borrowing, induced by rotation around the C–O axis, from the strong 1A1←1A1, π→π transition. A quantitative theory of this effect gives f∼10—6 for the total oscillator strength of the parallel bands. Several predictions which might be tested experimentally are made on the basis of this hypothesis.
Investigations of the Detonation Properties of Condensed Explosives with Equations of State Based on Intermolecular Potentials. I. RDX with Fixed Product Composition
Authors: Fickett W. , Wood W. W. , Salsburg Z. W. 
Published: January 2005

An attempt is made to determine an average pair potential of intermolecular force for the mixture of product gases of the condensed explosive RDX (cyclotrimethylenetrinitramine) from measurements of the detonation velocity. The principal approximations are that the products of detonation consist of CO, H2O, and N2 in equimolar proportions and that the equation of state for this mixture can be calculated from theories of the free-volume type with the use of an average intermolecular potential. It was found that the average intermolecular potential was fairly well determined at distances somewhat less than the crossover distance.
This result was almost independent of the choice of equation of state, although the calculated values of detonation temperature and pressure were not.
Analysis of Dielectric Loss in Two Urea Addition Compounds : The Hindered Single Axis Polar Rotator
Authors: Lauritzen John I. 
Published: January 2005

The dielectric behavior of two real substances is related to their molecular structure by the application of a theory of the general type proposed by Hoffman. The two real substances are the urea addition compounds of 12-bromotricosane and 16-hentriacontanone, where the polar long-chain molecules exhibit dielectric loss through rotation about their long molecular axes between orientational sites. This dielectric loss has been measured by Meakins, who proposed a qualitative theory similar to the one used here.
Smith has determined the crystal structure of the urea addition lattice. The orientational sites of the polar molecules are determined by the potential energy of the crystalline field, which is estimated from the geometrical configuration of the lattice by a Lennard-Jones (6–12) potential.
The dielectric loss is calculated in terms of the energy minima and maxima of the potential energy. The energy minima and the differences between the energy maxima are evaluated by a fit of the experimental dielectric loss of 12-bromotricosane in urea. These values are in good qualitative agreement with the potential energy obtained from the crystal structure.
The temperature dependence of the dielectric properties of 12-bromotricosane in urea are predicted under certain assumptions. The validity of these assumptions and the applicability of the theory are investigated by considering the dielectric loss of 16-hentriacontanone in urea over a wide temperature range.
Pure Quadrupole Resonance Determinations of Molecular Charge Distributions. I. Substituted Quinones, Quinolines, Pyridines, Pyrimidines, and Triazines
Authors: Bray P. J. , Moskowitz Saul , Hooper H. O. , Barnes R. G. , Segel S. L. 
Published: January 2005

The charge distributions in quinone and several heterocyclics containing nitrogen in the ring have been determined from the pure quadrupole resonance frequencies of attached halogens. Agreement with values from molecular orbital calculations is good in quinone and pyridine but poor in quinoline.
Quantitative measurements are presented for the effect of ring nitrogens on the double bond character of carbon-halogen bonds.
Kinetics of Gas Phase Halogenation Reactions
Authors: Benson Sidney W. , Buss Jerry H. 
Published: January 2005

Making use of the independently measured rate constants for the reactions X+X+M⇌X2+M (where X=Br, I, etc.) it is possible to calculate the times needed to approach the stationary state for X atoms. On applying these results to the kinetic studies which have been made of halogenation reactions, it is found that for most thermal brominations, the times are in excess of 100 seconds. For thermal chlorinations, the times are in excess of 1000 seconds while for more strongly bonded diatomic molecules they are still higher. In photochemical systems the times are of the order of 0.1 to 1.0 second for absorbed intensities of 1012 quanta/cc sec which are quite usual. The implications of these values for many of the systems studied, are that heterogeneous initiation and termination of chains are contributing significantly to the kinetics of thermal halogenations at temperatures below 500°C.
An examination of the brominations of isobutane, toluene, and neopentane shows that the mechanisms proposed in each case may be suspect and that heterogeneities are of likely importance and may account for the anomalous rate constants reported for these systems.
Methods are employed for estimating to ±2 cal/mole °K the entropies of free radicals and molecules. The entropy of t-butyl bromide is estimated to be 86.6 eu at 400°K while neopentyl bromide is 105.3 eu at 470°K. These entropy estimates make possible an examination of the self-consistency of the rate data with the proposed rate laws. It is shown that for the systems mentioned above, the data lead to the conclusion that other termination processes must be important, in contradiction to the empirically observed rate laws.
Finally, arguments are presented to show that bimolecular Arrhenius frequency factors should be less than collision frequencies.
Quantum Mechanics of the H3 Complex
Authors: Kimball George E. , Trulio John G. 
Published: January 2005

A minimum energy and the associated nuclear configuration are given for linear symmetric H3 in the ground (2∑u+) state. An LCAO MO wave function with complete configuration interaction, is constructed from a set of five 1S hydrogen-like orbitals with centers equally spaced on the line of nuclei. Apart from symmetry, nuclear positions and orbital centers are unrelated but the screening constant is the same for each orbital. The nonlinear parameters which were varied are the screening constant, internuclear distance, and the distance between adjacent orbital centers. An energy of —72.4±0.5 kcal/mole (relative to three separated H-atoms) is obtained; the experimental value2 is ∼—103 kcal/mole.
Many difficult 3- and 4-center repulsion integrals were evaluated numerically, using the CPC at Watson Scientific Computing Laboratory. The chief advantage of this model is that all the difficult integrals belong to one family characterized by essentially three parameters. Thus, all of them were computed from a single numerical program.