bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Capacities of CrF3 and CrCl3 from 15 to 300°K
Authors: Hansen Wilford N. , Griffel Maurice
Published: January 2005

The heat capacities of CrF3 and CrCl3 have been measured over the temperature range from 15 to 300°K. CrF3 has two peaks; the upper peak has its maximum at 69.8°K and is associated with a known magnetic transition. The lower peak has its maximum at 45.6°K and has not been correlated with magnetic phenomena. The total magnetic entropy is divided almost equally between the two. CrCl3 has a single peak at 16.8°K which is associated with a ferromagnetic transition.

For CrF3, S298.150=22.44 eu; for CrCl3, S298.150=29.38 eu. Other thermodynamic functions are tabulated.
Consolidated Variation Perturbation Theory
Authors: Shull H. , Simpson W. T.
Published: January 2005

A formula is derived which gives the exact remainder to the approximate energy eigenvalue obtained by the variation method. The remainder formula and approximations to it are closely related to the usual second-order perturbation formula. A scheme is suggested for consolidating the linear variation method and remainder formula into a single approximation method for energy eigenvalues. The method is illustrated with a calculation of the energy of the ground state of helium using 136 basis functions.
Motional Corrections to Distances Derived from NMR Data: NH4Cl, NH4F, and N2H6F2
Authors: Ibers James A. , Stevenson D. P.
Published: January 2005

Corrections for the effects of zero-point energy vibrations on the second moments of the nuclear magnetic resonance (NMR) spectral lines of NH4Cl, NH4F, and N2H6F2 are considered in detail and new N – H distances are derived. It is found for these particular substances that the corrections to the second moments for librational motions are relatively more important than corrections for bending or stretching motions. It is also found that because of the anharmonicity of the stretching motion the error involved in replacing the derived average of the distance by the equilibrium distance is relatively small.
Electron Diffraction Study of Lead Tetramethyl
Authors: Wong Chi-hsiang , Schomaker Verner
Published: January 2005

A reinvestigation of Pb(CH3)4 has shown the diffraction pattern to be in agreement with a symmetrical molecular structure and the complex atomic scattering factors of Ibers and Hoerni. The measured interatomic distances are Pb–C = 2.203±0.010 A and Pb···H = 2.79±0.05 A.
Electron Diffraction Study of Trifluoromethyl Iodide
Authors: Wong Chi-hsiang , Schomaker Verner
Published: January 2005

A reinvestigation of CF3I by electron diffraction for this molecule has confirmed the complex atomic scattering factors of Ibers and Hoerni. The structural parameters agree with those reported from earlier, inconclusive determinations.
Dispersion and Absorption of Sound in Ethyl Formate and Study of the Rotational Isomers
Authors: Tabuchi Daisaku
Published: January 2005

It was shown by Karpovich that there is the relaxational absorption of sound in liquid ethyl formate and that it results from the rotational isomerism about the C–O bond. Dispersion of sound velocity is expected from the absorption data, and its existence is confirmed by the present experiments. The sound velocities are measured over the frequency range from 300 kc to 9 mc/sec and at 5°C intervals from 10°C to 40°C by an ultrasonic interferometer. From these experimental results, the energy differences, the equilibrium constant, the rate of isomerization, and the height of the potential barrier hindering the internal rotation are calculated. The value of the energy difference is 2.50 kcal/mole and the height of the potential barrier, referred to the higher energy state is 3.38 kcal/mole. The calculated values of the heat capacity owing to the chemical reaction, the sound velocity at infinite frequency, and the maximum values of the absorption coefficient of sound per wavelength are in good coincidence with the experimental data.
Interactions of H— Ions and H Atoms with Ne, A, and H2
Authors: Mason Edward A. , Vanderslice Joseph T.
Published: January 2005

Previous work on the systems H—–He and H–He serves as a model for the calculation of the interactions of H— ions and H atoms with Ne, A, and H2 from an analysis of beam scattering measurements. It is shown that a mutually consistent interpretation can be developed on the assumption that the forces are repulsive in the region of interest. The H— ion elastic scattering cross sections are used to calculate the interactions of H— with Ne, A, and H2, and the electron detachment cross sections are used to locate the points at which these potential energy curves cross the corresponding curves for H atoms. The crossing points are shown to be consistent with potential energy curves for the interactions of H atoms with Ne, A, and H2 obtained directly or indirectly from independent scattering measurements involving beams of H atoms. The crossing points are used to extend these potential energy curves over a wider range of validity than previously available. Such a mutually consistent picture does not seem to emerge when attractive forces are assumed for the H— interactions.
Interpretation of Infrared Dichroism in Axially Oriented Polymers
Authors: Fraser R. D. B.
Published: January 2005

Although the actual distribution of chain directions in a partially oriented polymer cannot be determined from observations of infrared dichroism it is desirable to express the results in terms of a plausible model. A general relation between dichroic ratio and the parameter describing any model distribution is derived and applied to a number of suggested distributions. None are found to give plausible density functions for chain directions and a model based on the orientation of crystallites in a stretched polymer is suggested as a more suitable representation.
Application of a High-Speed Electronic Computer in Diffusion Kinetics
Authors: Flanders Donald A. , Fricke Hugo
Published: January 2005

The Argonne electronic computer AVIDAC is applied in the numerical solution of ∂n/∂t=∇2n−k1n2−k2n, which, with suitable boundary and initial conditions, represents the reaction kinetics of the one-radical model used earlier by Fricke to describe the track effect in the radiation chemistry of a solution of a single solute. The fractional number of radicals combining with solute molecules is computed in terms of two dimensionless parameters that completely define the problem. Comparison with the formulas derived by using Jaffé's approximation method shows in most cases agreement to within 10% (though in some extreme cases only to within 50% to 80%), which indicates that Jaffé's method should give useful results in developing other aspects of diffusion kinetics.
Stokes' and Einstein's Law for Nonuniform Viscosity
Authors: Broersma S.
Published: January 2005

The equations of hydrodynamics have been solved for the case of a viscosity dependence upon the distance r to a particle of radius a, suspended in a continuous fluid, as given by η∞/η(r)=1−εm(am/r)m. When |ε|<0.2, m⩾0 or ε⩾1, m>6 the omissions are less than 25% of the new terms. The force upon a spherical particle is given by 6πv∞η∞am[1+εm/(m+1)·(m2+4m+15)/(m+3)(m+5)]. The torque upon a spherical particle is 8πω∞η∞am3[1+εm·3/(m+3)]. The viscosity of a dilute suspension with 1 particle per sphere of radius R is η/η∞=1+εm(am/R)m 3/(3−m)+5/2(am/R)3·[1+εm3/(m−3)·(m3+5m2+47m−21)/(m+3)(m+5)(m+7)+4/5ε0]. This enables a study of the diffusion constants of a suspended particle, its effect upon the viscosity of a fluid, and the transition of a liquid into a gel. Experimental data concerning proton magnetic relaxation times of diamagnetic solutions and self-diffusion of protein and solvent molecules are discussed. The effect of slipping is examined.
Calculation of Reaction Profiles behind Steady-State Shock Waves. I. Application to Detonation Waves
Authors: Duff Russell E.
Published: January 2005

A numerical procedure for the integration of an arbitrary system of kinetic equations subject to the constraints imposed by steady state shock hydrodynamics is described. The detonation profile has been calculated for a 2H2+O2+Xe mixture at an initial pressure of 30 mm Hg. These conditions correspond to those used by Kistiakowsky and Kydd in a measurement of the wave profile. The calculated profile is in qualitative agreement with the measured one. The calculation provides empirical evidence that a frozen sound speed definition of the Chapman-Jouguet state cannot correspond to reality.
Evaluation of Lattice Interactions in or near a Cubic Crystal
Authors: Durham George S. , Soderberg Barbara A.
Published: January 2005

Procedures, based on the methods of Madelung, have been developed for the evaluation of lattice sums of inverse-power particle-interactions, λa—n, at any point in or near a cubic crystal. Although not as elegant mathematically as those of Hove and Krumhansl, they are more complete in including the important cases of a point near a plane or line of particles, and are sufficiently simple in principle to be understood and applied by anyone with a background in differential calculus.

Applications to a face-centered cubic ionic crystal are discussed and, as an example, the dipole-dipole van der Waals energy of a chloride ion before a NaCl half-crystal is calculated.
Polarized Infrared Spectrum of Potassium Thiocyanate
Authors: Jones Llewellyn H.
Published: January 2005

The polarized infrared spectrum of crystalline potassium thiocyanate is reported in this paper. This additional information necessitates certain assignment changes in the observed vibrational frequencies from those previously reported. The vibrational spectrum now appears quite complete and in agreement with the crystal structure report of Klug.
Study of the NH Radical by the LCAO-SCF Molecular Orbital Method
Authors: Boyd Marjorie E.
Published: January 2005

Wave functions, orbital energies, and total molecular energies have been obtained for the ground and five excited states of the NH radical. The Roothaan method was used, modified for the case of a molecule with unfilled orbitals. Separate self-consistent procedures were carried out for the ground state and a doubly excited state, while results for the intermediate excited states could be calculated with the ground state orbitals. Dissociation energies, dipole moments, and electron population analyses were also computed.

Comparison with the sparse experimental data indicates that the calculated states are too widely separated in energy. It is also found that this complete treatment gives higher energy values than Higuchi reported in an incomplete computation employing various approximations, although the wave functions are little changed.

In general, results seem to be about as reliable for the diatomic open shell case as for the usual closed shell molecules. Contrary to Sahni's suggestion, they do not appear to be better for the heteronuclear than for the homonuclear case.
On the Compressibilities of Simple Metals
Authors: McMillan W. G. , Latter A. L.
Published: January 2005

An isothermal equation of state is derived from the Coulomb virial theorem for ``simple'' metals consisting of imperturbable (i.e., invariant) kernels embedded in a uniform sea of valence (e.g., s) electrons. Comparison with experiment at room temperature gives good agreement for the alkali and alkaline earth metals, but is understandably erratic for other groups. The compressibility is simply related to the heat of formation of the normal gaseous ion kernel.
Investigation by Nuclear Magnetic Resonance of the Effects of Pressure on the Thermal Transition and Rotator Phase of 2,2-Dinitropropane
Authors: Billings J. J. , Nolle A. W.
Published: January 2005

The thermal transition for 2,2-dinitropropane, which normally occurs at —5°C, is observed at various pressures up to 1000 kg/cm2 in terms of the proton magnetic resonance line width. The spin-lattice relaxation time (T1) is observed for temperatures from —11°C to 65°C, at atmospheric pressure and under 1000 kg/cm2. The compressibility and the specific volume are measured, and x-ray powder patterns are compared, for temperatures above and below the transition. The latent heat of transformation and specific heat, above and below the transition, are calculated. Self-diffusion sets in at the transition, for all pressures studied. Under pressure, molecular rotation in the higher temperature phase is restricted and T1 is insensitive to temperature. The correlation time for molecular rotation at atmospheric pressure and 50°C is 7×10—12 sec, in fair agreement with dielectric data. The temperature dependence of T1 suggests that the fraction of molecules subject to rotation in the upper phase increases with the temperature.
Electron Spin Resonance in Transition Metal Chelates. I. Copper (II) Bis-Acetylacetonate
Authors: Maki A. H. , McGarvey B. R.
Published: January 2005

Electron spin resonance at 3.2 cm has been observed from copper(II) in single crystals of copper(II) bis-acetylacetonate diluted to ½ mole % with palladium(II) bis-acetylacetonate at 77°K and 300°K. The parameters of the spin Hamiltonian have been expressed in terms of the atomic orbital coefficients of molecular orbital wave functions describing the electron hole in the orbital ground state and two excited states. Experimental determination of the spin Hamiltonian then results in expressions for the molecular orbital wave functions. The results indicate that the in-plane sigma and pi bonding are appreciably covalent, whereas the out-of-plane pi bonding with the acetylacetonate ring is ionic.

The hyperfine interaction may be expressed by a relation of the type K2g2=A2g∥2cos2θ+B2g⊥2sin2θ+2C2g∥g⊥sinθcosθ, where C2 increases with decreasing temperature. The appearance of the term in sinθ·cosθ is attributed to low symmetry crystal fields due to the crystallographic array, the main symmetry being determined by the molecule itself. A small amount of rhombic character was observed in the g tensor, but was not enough to make an accurate location of the gx and gy directions possible. For the purpose of analysis, the g factor is expressed in terms of the two principal values g∥ and g⊥ which do not vary between 77°K and 300°K to the accuracy of the determination.
Statistical-Kinetic Theory of Phase Change
Authors: Gold Louis
Published: January 2005

Reaction rate kinetics is applied to the phenomenon of phase change. Two rate constants, one for nucleation and the other for growth processes, are embodied in the theory. These microscopic parameters are of a basic nature, with a significance quite distinct from the macroscopic quantities employed by Johnson-Mehl and Avrami (JMA) in the conventional phenomenological formulation. Expressions for the nucleation rate and the degree of transformation are established once the basic properties of the Poisson exponential binomial limit distribution have been determined. The statistical kinetic theory does indeed lead to a sigmoid-shaped transformation curve commonly observed in phase changes. An essential ingredient of the present theory, not incorporated in the JMA phenomenological theory, is the role of nuclei and specimen size; unusual behavior may be expected in small particles undergoing transformation.
Substituted Methanes. XXVIII. Infrared Spectral Data and Assignments for CHCl2F and CHClF2 and Potential Energy Constants and Calculated Thermodynamic Properties for CHCl2F, CDCl2F, CHClF2, and CDClF2
Authors: Weissman Herman B. , Meister Arnold G. , Cleveland Forrest F.
Published: January 2005

Infrared spectral data were obtained with NaCl and CsBr prisms for gaseous CHCl2F and CHClF2 from 270 to 4000 K (K=kayser=wave/cm) and the observed absorption bands were assigned to the vibrational modes for both molecules. Using the Wilson FG matrix method, reasonable values of the F-matrix elements were found which reproduced the observed wave numbers to within 2%. These were then used to calculate the wave numbers corresponding to the fundamental vibrations of CDCl2F and CDClF2. Also, these F-matrix elements and analytical expressions obtained from the theory of Gold, Dowling, and Meister were used to get values of the f-matrix elements (potential energy constants). Having tested the assignments by the normal coordinate treatments, the observed wave numbers for CHCl2F and CHClF2 were then used to calculate the enthalpy function, the free energy function, the entropy, and the heat capacity for 1 atmos pressure and for 12 temperatures from 100 to 1000°K, to a rigid rotor, harmonic oscillator, ideal gas approximation. Since the calculated wave numbers for CDCl2F and CDClF2 should be reliable to within about 2%, these were used in similar thermodynamic calculations to establish tentative values of the thermodynamic functions for these molecules.
Ultrasonic Absorption in MnSO4 Solutions
Authors: Kor S. K. , Verma G. S.
Published: January 2005

Ultrasonic absorption in MnSO4 solutions has been studied in great detail in the frequency range 1–6 Mcps., at concentrations varying from 0.0025 to 1 molar. The relationship between the excess sound absorption and the concentration is found to be linear from 0.02 to 0.1 molar, but becomes nonlinear both below 0.02 and above 0.1 molar. The frequency behavior of the excess sound absorption can be represented by a relaxation curve at about 3 Mcps. The mechanism responsible for excess sound absorption is of the dissociation type and is supported by the study of the influence of the dielectric constant of the solvent on the absorption and the temperature shift of the relaxation frequency.
On the Approximate Calculation of Eigenvalues with Special Reference to the Helium Atom
Authors: Gray B. F.
Published: January 2005

A method is developed for treating the error in the energy of a variation function as a perturbation, the variation function serving to describe the ``unperturbed state.'' An effective potential is defined from the variation function, and comparison of this with the correct potential for the helium atom gives useful information about the behavior of the variation functions as the electronic separation approaches zero. In the second section, iterative methods of improving a variational wave function without increasing the number of parameters are discussed and the conditions under which they will be applicable are examined.
Reactions of Gaseous Molecule Ions with Gaseous Molecules. IV. Experimental Method and Results
Authors: Stevenson D. P. , Schissler D. O.
Published: January 2005

This paper is concerned with a detailed description of quantitative studies of certain secondary reactions involving simple molecules and ions that occur in the ion source of a mass spectrometer. It is found that the phenomenological reaction cross sections for reactions of the type P++R→S++···are independent of the temperature of the gas in the ion source, and vary inversely with the square root of the product of the ion repeller field strength and the reduced mass of the reactant ion-reactant molecule pair. For the reactant ion (P+) a rare gas, hydrogen, nitrogen, or carbon monoxide, and the resultant molecule (R) hydrogen, the cross sections for formation of the secondary ion, S+=PH+, are found to be one or two orders of magnitude greater than the ordinary, kinetic theory collision cross sections for similar atoms and molecules.
Magnetic Susceptibility of Ferrous Ammonium Tutton Salt at Liquid Helium Temperatures
Authors: Richardson J. T. , Sapp R. C.
Published: January 2005

The magnetic susceptibility of ferrous ammonium sulfate hexahydrate has been measured between 0.95 and 4.2°K by both the Faraday and the ballistic mutual inductance bridge methods. At 4.2°K the susceptibility is (1.45±0.05)×10—3 emu/g, close to the value given by the high temperature Curie-Weiss law, 9.71×10—3/(T+3.2). Below 2°K the susceptibility is constant at (1.85±0.05)×10—3 emu/g. The results are shown to be compatible with available specific heat data in the low temperature region, provided that the lowest level is taken to be a singlet and the constant susceptibility is ascribed to temperature-independent paramagnetism of the lowest level.
Generalized United-Atom Theory of Molecules. I. Spherical Contributions in the sσ Wave Functions for H2+
Authors: Chen Tien Chi
Published: January 2005

The generalized united-atom view of molecules suggests that electronic states of symmetric molecules may be characterized by means of ``atomic'' quantum numbers.

A test for the purity of the quantum number l in sσ states in H2+ is facilitated by the Tibbs-Wannier theory of a Coulomb field with cutoff. Comparison shows that 96% of the ground-state electronic energy is due to contributions of spherical functions.
Organic Photoconductors. IV. Sign of the Charge Carrier
Authors: Nelson R. C.
Published: January 2005

If the energies of carriers in the conduction band and valence band of a dye can be determined with respect to the corresponding levels in cadmium sulfide, then the sign and magnitude of the photo-emf developed at a junction between dye and cadmium sulfide can often be interpreted as indicating a transfer of carriers between conduction bands, conduction hence being due primarily to electrons; or as a transfer between valence bands, conduction thus being due to holes. In this way the majority carrier in several cationic dyes is shown to be electrons; in erythrosin, an anionic dye, holes; and in methyl chlorophyllide-a, a non-ionic dye, probably electrons.
Temperature Dependence of the Phase Transition in Cerium
Authors: Herman R. , Swenson C. A.
Published: January 2005

The cubic-condensed cubic transition in cerium has been observed as a function of temperature and pressure from 360°K and 11 000 atmos to 78°K and zero pressure. The data which were obtained definitely link the high pressure, room temperature and the low temperature, zero pressure transitions which have been observed previously. While the data show some unexplained features, the calculated value for the latent heat of transition at 288°K (1150±100 cal/mole) agrees as to order of magnitude with a directly measured value (880±40 cal/mole) by other workers.
Kinetics of Decomposition of Isobutyryl Peroxide and Reactions of Isopropyl Radicals
Authors: Smid J. , Szwarc M.
Published: January 2005

The kinetics of decomposition of isobutyryl peroxide was investigated in isooctane solution. The decomposition was shown to be unimolecular, the activation energy being 27.3 kcal/mole and the frequency factor 2.8·1014 sec—1. The lower activation energy of this decomposition, as compared with decompositions of other acyl peroxides, suggests that energy is supplied to the O–O bond by the decarboxylation of radicals resulting from the dissociation of this peroxide. The problem of energy supply is taken further in the following publication.

The reactions of isopropyl radicals formed in the dissociation process were studied quantitatively.
Vibrational Spectra of the Crystalline Methyl Halides
Authors: Dows David A.
Published: January 2005

The infrared spectra of the crystalline methyl halides, CH3Cl, CH3Br, and CH3I, at 80°K are reported. Information on gas-solid frequency shifts, band splittings due to site symmetry and intermolecular coupling, librational frequencies, and relative intensities of band components is summarized and compared.

Relative intensities of band components are not in agreement with the predictions of the ``oriented gas'' model. Most other observations are consistent with the assumption of isomorphism between the crystal structures of the three compounds, but the data are not sufficient to prove the isomorphism.
Infrared Emissivity of NO in High-Temperature Air
Authors: Breene R. G.
Published: January 2005

The emissivity treatment developed by Mayer has been modified herein for specific application to rotation-vibration spectra. In order to obtain the oscillator strengths requisite to such a calculation, an earlier developed calculation of the vibrational matrix elements of NO has been utilized. The emissivity of an equilibrium distribution of NO in high-temperature air has been calculated for one layer thickness and several values of temperature and pressure. This emissivity calculation has been programed on the IBM 704 electronic data processing machine.
Morse Potentials for Excited States of Diatomic Molecules
Authors: Keyes Robert W.
Published: January 2005

A model is presented, according to which the nuclear potential functions of the various electronic states of a diatomic molecule form a one-parameter family of Morse functions. The variable parameter represents the fraction of the valence electrons which are in antibonding orbitals. By using the properties of the ground state to determine the Morse constants, a relation between ωe and re of the various electronic states is obtained. This relation reproduces the observed data rather accurately. Somewhat cruder predictions of vibrational anharmonicity, ωeχe, and of dissociation energies are also obtained. Properties of molecular ions and of bonds in polyatomic molecules are also obtained from the model. The measure of bond strength obtained from the model is similar to that deduced from electron configurations in the usual way.
Diffusion and Heterogeneous Reaction. I. The Dynamics of Radical Reactions
Authors: Wise Henry , Ablow Clarence M.
Published: January 2005

The diffusion and heterogeneous reaction of labile species in a cylinder of finite length are examined. The effects of radial and longitudinal diffusion are included in the mathematical treatment. The results of this analysis are applied to published data of the recombination coefficients of oxygen and hydrogen atoms on the surfaces of various materials.
Delayed Singlet-Singlet Emission from Molecular Crystals
Authors: Blake Norman W. , McClure Donald S.
Published: January 2005

The fluorescence emission from the molecular crystals naphthalene and phenanthrene may be observed after a delay of several milliseconds from the time of excitation. The decay time is strongly temperature dependent and the decay law is nonexponential. The delayed emission is connected with the crystalline state of the material, but is not otherwise understood.
Internal Barrier of Propylene Oxide from the Microwave Spectrum. II
Authors: Herschbach Dudley R. , Swalen Jerome D.
Published: January 2005

Several long progressions of perpendicular transitions have been measured in the microwave spectrum of propylene oxide. These have provided an opportunity to test the theory of internal rotation over a very large range of rotational quantum numbers, J=1 to 48 and K=1 to 25, in the ground torsional state. For low K, the K doubling which arises from the asymmetry of the molecule is much larger than the splittings due to tunneling through the potential barrier. The spectrum resembles that of an ordinary asymmetric rotor except that each line is split into a close doublet by the tunneling. At high K, the K doubling becomes negligible. A triplet fine structure is observed in which the spacings show a periodic dependence on K, essentially the same as that calculated for the case of two coaxial symmetric tops. (For a true symmetric rotor, the selection rules would prevent the observation of this pattern.) At intermediate K, the K doubling and the tunneling perturbations become comparable. The mixing of the rotational wave-functions which results permits ``forbidden'' lines to appear. Very good agreement with theory is obtained over the whole range of K, with the barrier height V3=895 cm—1 (2560 cal/M).

Rotational transitions have also been assigned for molecules in the first and second excited torsional states, in which the tunnel effect splittings are greatly magnified. For both the excited states, the barrier height is found to be identical with the ground state result. This supports the usual assumption that perturbations from vibrational interactions with internal rotation and from the sixfold V6 term in the potential barrier are small enough to be safely neglected.
Reaction of Methyl Radicals with Ethylene
Authors: Brinton R. K.
Published: January 2005

The gas phase reaction between methyl radicals and ethylene has been studied between 124° and 159° by the thermal decomposition of di-t-butyl peroxide in presence of ethylene. The value of k4a/k31/2 for the reactions, CH3+C2H4→ lim k4aC3H7  2CH3→ lim k3C2H6,is 3.3×10−7exp−8660/RT molecule−1/2cm3/2sec−1/2 and the steric factor for the addition of methyl radicals to ethylene is about 7.6×10—3. At low ethylene concentrations no evidence could be found for polymerization beyond the initial methyl radical addition.
Electric Strength, Molecular Structure, and Ultraviolet Spectra of Hydrocarbon Gases
Authors: Heylen A. E. D.
Published: January 2005

Previous careful measurements of the sparking potential of a number of hydrocarbon gases over a wide range of pressures and a fixed electrode spacing have been extended to cover olefins which involve methyl substitution around the ethylenic double bond. The effect of cyclization in a monoolefin and of methyl substitution in a diene are also included with measurements in cyclopentene and isoprene. Using an established Townsend-like expression for the ionization coefficient α and for the sparking potential, the molecular parameter B, a constant in the expression for α can be determined for each gas. This constant can be directly related to molecular structure and to mean electron-molecule scattering cross sections. Thus the influence on B of CH3 and CH2 groups and chromophoric groups involving double and triple bonds can be assessed and cross-section values determined accordingly. These prove to be independent of methyl substitution. Information from ultraviolet absorption spectra furnishes supporting evidence for this model which should make it possible to correlate the sparking potentials of a large range of hydrocarbons than hitherto.
Thermodynamics of Nonstoichiometric Nickel Tellurides. II. Dissociation Pressures and Phase Relations of Tellurium-Rich Compositions
Authors: Westrum Edgar F. , Machol R. E.
Published: January 2005

Dissociation pressures of tellurium over liquid and solid nickel telluride solutions have been measured with a silica Bourdon gauge at compositions corresponding to NiTe1.5, NiTe1.7, NiTe1.9, NiTe2.0, and NiTe9 at temperatures up to 780°. Modifications of the manometric technique are described which permit accuracies of 0.1 mm pressure and 0.1° at high temperatures with corrosive substances where the pressure is sensitive to impurities or to composition changes. The results, together with data on the vapor pressure of pure tellurium, define the partial molal free energies and entropies of tellurium and, together with direct eutectic temperature measurement, delineate features of the phase diagram for compositions with more than 60 atomic percent tellurium.
Random Events in a Liquid
Authors: Turner R. E.
Published: January 2005

A model is suggested for the evaluation of the time integral of the autocorrelation function for inter-molecular forces. This integral plays the part of a ``friction constant'' in the statistical mechanical theory of transport processes.

A cluster of a small number of molecules is regarded as a nonisolated system. By using a self-consistency principle i.e., the identity of the autocorrelation function for all molecules, a fourth-order differential equation is derived, which in principle could be made to give a unique determination of the autocorrelation function. Two methods are given for finding an approximate solution.

An alternative expression for the autocorrelation function is found by the introduction of ``collective'' coordinates. Comparison of this expression with the result obtained by the principle of self-consistency leads to a unique determination of the integral of the autocorrelation function.

The result has a reasonable physical interpretation for the mechanism of correlation breakdown, namely, the transfer of energy from ``collective'' motion or sound waves to ``individual'' or ``average'' motion.
Electron Impact Studies of Sulfur Dioxide and Sulfuryl Fluoride
Authors: Reese Robert M. , Dibeler Vernon H. , Franklin J. L.
Published: January 2005

Mass spectra and appearance potentials have been obtained for the principle positive and negative ions of SO2 and SO2F2. Ionic heats of formation and probable ionization-dissociation procesess are tabulated. The electron-impact data for SO2 support the values of 3.3 ev for D(S2) and 5.15 ev for D(SO). The molecular ionization potential is in good agreement with recent photoionization measurements. The ΔHf(SO2F2) = — 205 kcal/M is calculated from the appearance potential of the SO2+ ion. Other ionic heats of formation are based on this value. The ΔHf(SO+) is in good agreement for both molecules. A minimum value of 3.0 ev is calculated for the electron affinity of F2 from the appearance potential of the F2- ion.
Thermodynamic Functions of Carbon Tetrachloride and Monochloride
Authors: Gordon John S.
Published: January 2005

Data were calculated for the ideal gases CCl4 at 298.16 to 2000°K and CCl at 298.16 to 6000°K. The CCl4 data are in good agreement with published values.
Crystal Structure of Copper Fluoride Dihydrate, CuF2·2H2O
Authors: Geller S. , Bond W. L.
Published: January 2005

The crystal structure of copper fluoride dihydrate, CuF2·2H2O, has been determined from single crystal x-ray data. The monoclinic unit cell, space group C2h(3)—12/m, with a=6.416, b=7.397, c=3.301, all ±0.005 A, β=99.6±0.1°, contains two formula units. The atoms are in the following positions: Cu(II) in 2(a): (0, 0, 0; ½, ½, ½): F— in 4(i): (0, 0, 0; ½, ½, ½)±(x, 0, z) with x= —0.222, z=0.311; O in 4(g): (0, 0, 0; ½, ½, ½)±(0, y, 0) with y=0.261. The estimated parameters of the H atoms in 8(j): (0, 0, 0; ½, ½, ½)±(x, y, z; x, y, z) are x=0.107, y=0.340, z= —0.073. In this structure the Cu(II) atoms have two fluorine neighbors at 1.89 A, two (water) oxygen neighbors at 1.93 A, and two fluorine neighbors at 2.47 A. These form a highly distorted octahedron about the Cu(II), and in fact, the distance of the two further fluorine atoms implies that the Cu(II) prefers square coordination. The distance 2.66 A between an oxygen and a fluorine associated with a neighboring lattice point implies appreciable hydrogen bonding between these atoms .Comparisons are made with other Cu(II) halide compounds and the observed antiferromagnetism is discussed.

The morphology and optic axes have been investigated. The refractive indices (NaD) are α=1.51, β=?, γ=1.54. The optic angle 2V≅46° and the optic axes lie in the (010) plane between +a and +c, one optic axis making an angle of 16° with the c axis.
Effect of Pressure on the Spectra of Certain Transition Metal Complexes
Authors: Parsons R. W. , Drickamer H. G.
Published: January 2005

The effect of pressure (to 130 000 atmospheres) has been measured on the splitting of the 3d levels of the nickel and chromium ions complexed with water and ammonia. Data have also been obtained on CoSO4· 7H2O and K3Fe(CN)6. In general, the effect of pressure is to increase the effect of the ligand field and to increase the splitting of the levels. This is interpreted in terms of the change in ligand-metal distance. A phase transition was noted in [Ni(H2O)6]SO4 at 65 000 atmospheres.

A charge transfer band was also observed in [NiNH3)6]Cl2. The effect of pressure is to increase the intensity with no apparent change in the location of the maximum.
Structural Isomer Discrimination between Cyanamides and Carbodiimides by Nitrogen Nuclear Magnetic Resonance
Authors: Ray James D. , Piette Lawrence H. , Hollis Donald P.
Published: January 2005

The structural isomers diethylcyanamide and N,N′-dicyclohexylcarbodiimide were studied by both proton and nitrogen NMR techniques. The structures R2N–C≡N and R–N=C=N–R have been shown to apply to cyanamides and carbodiimides, respectively.
Effect of Electrostatic Fields on the Orientation of Colloidal Particles Immersed in Shear Flow
Authors: Demetriades S. T.
Published: January 2005

The orientation distribution function for rigid colloidal particles immersed in Couette flow with an electric field parallel to the velocity gradient is derived in this study. Simple streaming birefringence experiments with variable or constant electric fields can be devised to test this theory which promises to yield a new method for measuring some geometrical and physical properties of colloidal particles.
Spectra of Homologous Series of Monosubstituted Amides
Authors: Beer M. , Kessler H. B. , Sutherland G. B. B. M.
Published: January 2005

Infrared spectra of the pure liquid and of dilute solution were observed for N-methyl, N-ethyl, N-propyl, and N-butyl acetamides and propionamides and of N-deuterated N-butylacetamide. Also infrared spectra of N15-butylacetamide and N-deuterated N15-butylacetamide and the Raman spectra of N-butylacetamide and N-deuterated N-butylacetamide were observed. In each series a band in the higher members was related to each band of the N-methyl compound on the basis of similarity in frequency, intensity, band width, and the influence of dilution. In N-methylacetamide and N-butylacetamide bands thus related were found to have also similar Raman activities and similar shifts on replacing the peptide hydrogen by deuterium. The extra bands could be related systematically to the extra CH2 groups. The implications of these results in protein spectroscopy and in the spectroscopic study of homologous series is discussed.
Ligand Field Theory of Ni(II) Complexes. III. Electronic Spectra and Solution Paramagnetism of Some Diamagnetic Ni(II) Complexes
Authors: Maki Gilda
Published: January 2005

The observed electronic absorption spectra of six diamagnetic Ni chelates are successfully assigned using ligand field theory with consistent values of the field parameters. The observed solution paramagnetism of some of these diamagnetic chelates is attributed to an equilibrium between solvated molecules of the same symmetry in singlet and triplet states rather than to a change in symmetry of the complex as has previously been postulated. Calculations of the energies of six-coordinated Ni(II) complexes indicate that solution favors a triplet ground state for each symmetry studied. With this model, the extent of solvent-ion interaction determines the separation of singlet and triplet states and hence the distribution of molecules among these states. The proposed equilibrium mechanism and the calculated energy levels of the ion, used together in a consistent manner, give a quantitative explanation of both the paramagnetism and spectra of these complexes in solution.
Properties of Hydrogen Chemisorbed on Tungsten
Authors: Eisinger Joseph
Published: January 2005

The sticking probability of hydrogen on a single crystal tungsten ribbon was measured as a function of the number of adsorbed atoms. The work function of the same ribbon was measured by a photoelectric technique. The results indicate that during the initial fast chemisorption characterized by an almost constant sticking probability of approximately, 0.2 the work function rose from 4.54 ev for the clean surface to a maximum value of 5.0 ev for the covered surface. The maximum coverage at room temperature was (7.5±1.0)×1014cm−2.Evidence for two states of adsorption is presented and the experimental techniques, used in these and earlier experiments, are described in some detail.
Semiempirical Calculation on the Electronic Structure of the Nitrogen-Containing Heterocyclic Molecules. II. Electronic Structure of Pyrazine with Particular Reference to Its n—π Transition
Authors: Anno Tosinobu , Sadô Akira
Published: January 2005

The semiempirical theory of n—π and π—π spectra of nitrogen analogs of aromatic hydrocarbons proposed in Part I is applied to calculate the lower excited levels of the pyrazine molecule. The doubly excited configurations as well as singly excited configurations are considered in CI calculation. It is shown that the usual assumption of sp2 hybridization of the nonbonding orbital of the nitrogen atoms in the pyrazine molecule results in a considerably higher calculated value for the n—π transition energy as compared with experiment, even if the doubly excited configurations are considered. In order to bring the calculated values of the lowest Ag1→B1u1,B3g1(n−π) transition energies in agreement with the observed values, the s character of the nonbonding orbital of the nitrogen atom should be taken as 0.103. Discussions which support the lower s character of the nonbonding orbitals of the nitrogen atoms in this molecule are presented.
Self-Diffusion in Argon to 300 Atmospheres
Authors: Mifflin T. R. , Bennett C. O.
Published: January 2005

The coefficient of self-diffusion for argon is measured from 68 to 291 atmos at 49.4°C. A radioactive tracer technique employing A37 is used and coefficients are measured in a cell in which the path of diffusion is through a plug of porous bronze. Results agree reasonably well with the Enskog dense gas theory calculated from p-v-T data.
Molecular Collisions. I. Formal Theory and the Pauli Principle
Authors: Gioumousis George , Curtiss C. F.
Published: January 2005

The formal theory of scattering of Gell-Mann and Goldberger is used to obtain expressions for the differential cross sections describing collisions between two molecules with internal structure in terms of the asymptotic forms of the wave functions. The effect of the Pauli principle is considered explicitly.
Energy Levels, Atom Populations, Bond Populations in the LCAO MO Model and in the FE MO Model. A Quantitative Analysis
Authors: Ham Norman S. , Ruedenberg Klaus
Published: January 2005

Quantitative results for fourteen representative organic molecules are derived and analyzed on the basis of the LCAO MO model and on the basis of the FE MO model. Calculated are, besides the energy levels, the atom populations and the bond populations, quantities defined in a recent paper as an accurate measure of the distribution of electrons.

The results of the LCAO MO model and of the FE MO model are then compared, and for the more important quantities considerable agreement is found. The origin of the agreements and disagreements is shown to be different from the one generally supposed.

Because of their general usefulness, complete tables are given for the eigenvalues and eige nvectors of the fundamental topological matrices associated with the molecules investigated.
Mobile Bond Orders in Conjugated Systems
Authors: Ham Norman S. , Ruedenberg Klaus
Published: January 2005

A comparative study is made of the following bond orders: MO bond orders of Coulson, MO bond orders of Mulliken, MO bond populations of Platt-Ruedenberg-Scherr, VB bond orders of Pauling. The comparison is carried through on the basis of theoretical derivations and on the basis of numerical calculations for a large number of molecules. The main results are: an accurate functional connection between the Coulson and Mulliken bond orders; the characterization of a new type of bond order based on bond populations, and related linearly to bond lengths; a MO expression for VB bond orders.
Kinetic Theory of Nonspherical Molecules. III
Authors: Muckenfuss Charles , Curtiss C. F.
Published: January 2005

The kinetic theory of nonspherical molecules has been extended to multicomponent mixtures. The treatment is based on a set of generalized Boltzmann equations analogous to that used in the treatment of a pure gas, which are solved by a perturbation method similar to that of Chapman and Enskog. The transport coefficients are obtained in terms of a set of multidimensional integrals which depend on the dynamics of collisions of nonspherical molecules. These integrals are related to the ``bracket'' integrals of Chapman and Cowling and are generalizations of similar integrals which appear in the treatment of a pure gas of non-spherical molecules. These integrals are reduced to four-dimensional integrals, the integrands of which depend only on the geometry of the molecules, and the integrations are carried out over the surfaces of the two molecules. As an example, the final integrations are carried out for the spherocylindrical model. The coefficients of diffusion, thermal diffusion, shear and bulk viscosity, and thermal conductivity for a binary system are obtained in terms of two parameters characteristic of the shape and mass distribution of each molecule. The coefficient of self-diffusion is used to compare the thermal conductivity of a pure gas with that given by a modified form of the Eucken approximation.
Statistical Mechanical Theory of the Thermal Conductivity of Binary Liquid Solutions
Authors: Bearman Richard J.
Published: January 2005

A statistical mechanical theory of the thermal conductivity of solutions results from a generalization to the space of molecular pairs of the linear expressions appropriate to the thermodynamics of irreversible processes for the mean forces in singlet configuration space. When simplifying assumptions of the equilibrium regular solution theory are introduced into the general expression, the thermal conductivity of the mixture is obtained in terms of the thermal conductivities of the pure components, the self-diffusion coefficients, mole fractions, and molar volumes. Numerical calculations are in semiquantitative agreement with experiment.
Correlation Correction Study of CH, NH, and OH
Authors: Krauss M. , Wehner J. F.
Published: January 2005

The semiempirical intra-atomic correlation correction (ICC) of Hurley and a configuration-interaction (CI) calculation are applied to previous single configuration calculations of the ground states of CH, NH, and OH. Results are reported for the 2Π, 4Σ—, and 2Δ states of CH, the 3Σ— state of NH, and the 2Π state of OH. The binding energies and dipole moments obtained for the hydrides are compared with experimental values and with the results of a similar calculation by Hurley of the ground states of these molecules. Results of a calculation of the Fermi contact term of the magnetic hyperfine interaction are also given.
Measurement of Ionization Potentials by Electron Impact
Authors: Nicholson A. J. C.
Published: January 2005

A comparison has been made between the different methods of extracting ionization potentials from ionization efficiency curves measured by electron impact. Conventional methods are usually accurate to ±0.1 ev but the assumptions on which they are based are such that no further increase in accuracy can be expected. These methods sometimes give wildly inaccurate results; the main cause of this is the presence of fine structure in the ionization efficiency curve. Morrison's method of determining ionization potentials, because it detects fine structure, enables measurements accurate to ±0.02 ev to be made. Other methods which detect fine structure are equally accurate but require more complex apparatus.