bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion and Exchange of Zinc in Crystalline Zinc Sulfide
Authors: Secco E. A.
Published: January 2005

The diffusion and exchange of zinc vapor with crystals of zinc sulfide has been measured from 925 to 1075°C. The measured exchange rate was observed to be controlled by the diffusion of Zn in ZnS. A critical examination of the log D versus 1/T plot reveals that three distinct diffusion processes are operative in the temperature range studied. At 1 atmos zinc pressure, the diffusion coefficients were calculated as D=3×10−4exp(−35 kcal/RT) cm2 sec−1below 940°C, D=1.5×104exp(−75 kcal/RT) cm2 sec—1 between 940° and 1030°C, and D=1×1016exp(−150 kcal/RT) cm2sec−1above 1030°C. Variation of zinc pressure from 0.25 to 2.0 atmos showed that D varies as PZn1.5. Values of D were observed to increase with increasing penetration of Zn into the ZnS crystals. The kinetic and structural interpretations of these results are discussed.
Statistical Theory of Chemical Reaction Rates
Authors: Keck James C.
Published: January 2005

A ``statistical'' theory of chemical reaction rates based on ``scattering theory'' in the strong coupling approximation is presented. The theory is developed explicitly for reactions involving the dissociation and recombination of a diatomic molecule in the presence of an atomic catalyst but is also readily applicable to other reactions. The theory formally includes Wigner's theory of three-body recombination and the classical theories of both recombination and dissociation. A limited comparison with experiment shows reasonable agreement.
Sedimentation in Multicomponent Systems
Authors: Peller Leonard
Published: January 2005

The formalism of irreversible thermodynamics is employed to derive expressions for the sedimentation coefficients of the species in a multicomponent system in terms of experimentally accessible quantities. Equations are presented for certain limiting cases which may be encountered experimentally. The determination of the hydration of macromolecules by sedimentation methods is examined.
Pseudo-Energy Transfer in Some Unimolecular Decompositions
Authors: Szwarc M. , Herk L.
Published: January 2005

The unimolecular decomposition of molecules involving rupture of a bond and formation of unstable radicals (i.e., ones which decompose exothermally) is discussed. It is shown, by using contour maps, that two cases should be considered. If the decomposition of the unstable radical does not involve activation energy, then the process starts as expansion of one bond, but eventually the reaction path turns toward the center and the process proceeds as a simultaneous decomposition of the molecule into 3 or more fragments. The transition point is represented by a saddle point and the activation energy is lower than the expected bond dissociation energy. In a loose language, the exothermicity of the radical decomposition helps in the primary dissociation process.

On the other hand, if the decomposition of the unstable radical does involve activation energy, then the unimolecular rupture of the first bond proceeds normally.
Potential Function of NF3
Authors: Schatz Paul N.
Published: January 2005

An approximate potential function has been determined for NF3 by using the four fundamental frequencies, the experimentally determined rotational distortion constant DJ, and physical arguments based on the absolute intensity results. Use has also been made of an argument proposed by Polo and Wilson based on a comparison of NF3 with the isoelectronic molecule CF3H.

The rotational distortion constants have been calculated as a function of the force field using the method of Kivelson and Wilson. Explicit formulas are given for the change in moment of inertia with symmetry coordinate for an XY3(C3v) type molecule.

Using the approximate potential function, values of the valence type force constants and the rotational distortion constant DK have been calculated.
Statistical Thermodynamics of Polymer Solutions. I. Theory of the Second Virial Coefficient for a Homogeneous Solute
Authors: Casassa Edward F. , Markovitz Hershel
Published: January 2005

An approximate theory of the second virial coefficient A2 for a system of identical random flight polymer chains of n steps, of average length b, is developed on the basis of a treatment by Zimm in power series form which, though formally exact, is not rapidly enough convergent to be practically useful. By introducing, as an approximation, a spherically symmetrical distribution of the chain segments of two interacting molecules averaged relative to the locus of an initial intersegmental contact, it becomes possible to sum the series, the terms of which relate to molecular configurations with progressively greater numbers of simultaneous contacts. The result, a double integral, is evaluated numerically; but the simple relation A2=const[1−exp(1.42ψ)]/1.42ψ,in which ψ=4βn1/2(3/2πb2)3/2 and β is the mutually excluded volume for a pair of segments, differs from the integral by less than one percent for all positive values of the parameter ψ. The analytical form of this equation is justified in terms of the theory.

Virial coefficients calculated from the theory with parameters derived from intrinsic viscosity measurements agree fairly well with the observed dependence on solute molecular weight for two systems in good solvents, but the magnitudes obtained are too small. If, however, the parameters of the theory are considered arbitrary, correspondence with experiment, to within errors of measurement, can be achieved.
Electron Capture Processes in the Hydrogen Halides
Authors: Frost D. C. , McDowell C. A.
Published: January 2005

The formation of negative ions by resonance capture processes of the type XY+e=X+Y—, has been studied for the hydrogen halides. A monoenergetic electron source has been used and it has been possible to determine the true shape of the resonance capture peaks in these cases. It has been found that the negative ions appear at energies which are in agreement with recent values for the dissociation energies of the H—X bonds, and the electron affinities of the halogen atoms.
Negative Ion Formation and Electric Breakdown in Some Halogenated Gases
Authors: Hickam W. M. , Berg D.
Published: January 2005

Utilizing a conventional electron gun and mass spectrometer, the formation of negative ions at low electron energies have been investigated for a number of halogen containing gases used in electric breakdown studies. The SF6— peak is used as an energy calibration for establishing the appearance potential and the energy width over which capture occurs for the individual gases. It is found that the relative areas of the negative ion curves can be correlated with the electric strength of the gases. The results suggest that the formation of SF5— rather than SF6— may be the important process in providing the relatively high electric breakdown value for SF6. Electron attachment associated with SF6 and CCl4 is found to be an extremely sensitive function of the gas temperature. The gases investigated include CCl4, CCl3F, CCl2F2, CClF3, CF4, CF3SF5, SeF6, C2F3Cl, CHCl2F, CF2Cl–CF2Cl, and ClO3F.
Mean Amplitudes of Vibration in Allene and Allene-d4 Molecules. I
Authors: Cyvin Sven J.
Published: January 2005

Observed fundamentals for allene and allene-d4 are used for performing a normal coordinate analysis. Eight alternative sets of 13 force constants from the harmonic potential energy function are evaluated numerically. The normal coordinates for allene and allene-d4 are determined. Analytical expressions for all the seven types of interatomic distance displacements are given. For each of these types, both in allene and allene-d4, the standard deviations (here called mean amplitudes of vibration) are calculated. The obtained values at four temperatures, T = 0, 273, 298, and 323 °K, are reported.
Rate of Recombination of Nitrogen Atoms
Authors: Harteck Paul , Reeves Robert R. , Mannella Gene
Published: January 2005

The rate of recombination of nitrogen atoms by three-body collision has been determined at room temperature and 0.5–1.3 mm pressure. The nitrogen was dissociated (about 3–6% nitrogen atoms) in a condensed discharge and pumped continuously through a glass tube 4.2 cm i.d. and 2.5 m long. The atom concentration was measured at a given point by ``titrating'' the N atoms with NO which was introduced into the gas stream at this point which was a short distance from the discharge tube.

The N atoms react essentially instantaneously with NO in this titration, N+NO→N2+O.When excess NO is added, the unconsumed NO combines with the O atoms formed yielding the typical oxygen afterglow. If insufficient NO is added, however, the unconsumed nitrogen atoms react with the O atoms formed, yielding the typical blue color of the NO bands, N+O+M→NO*+M,When the quantity of NO added essentially equals that of the N atoms, the gas is practically colorless. This gives the N atom concentration at this point.

In order to determine the rate of recombination of the N atoms, the relative decrease in intensity of the yellow nitrogen afterglow was obtained by following the reaction along the tube by means of a photomultiplier. The intensity of the afterglow is known to be proportional to the square of the N atom concentration. With the decrease of N atoms as a function of time and with the absolute N atom concentration known at a given point, the rate coefficient could be determined.

The over-all value of the rate coefficient for the recombination reaction, N+N+M→N2+M,was determined by this experimental method to be k=1.72(±0.17)×10−32cm6/molecules2sec.

The third body was nitrogen or argon; the rate coefficient was the same for both gases within the limits of error given.
Nuclear Magnetic Resonance of Molten and Solid Thallium Salts
Authors: Rowland T. J. , Bromberg J. Phillip
Published: January 2005

Chemical shifts associated with the species present in some molten and solid thallium salts have been investigated using nuclear magnetic resonance. Shifts between the solid and liquid resonances of three simple ionic thallium salts at their melting points were measured. A correlation with electronegativity is indicated. Resonance absorptions, which corresponded to the thallous and thallic states, were found in the molten complex salts Tl2Cl4 and Tl2Br4. The separation of these absorptions was found to be temperature dependent, and an explanation based on exchange is discussed. One can infer from this that the average lifetimes of the species are about 10-5 sec at 500°K.
Reaction Rates and Affinities
Authors: Van Rysselberghe Pierre
Published: January 2005

A new definition of elementary reactions is being based upon the Marcelin-De Donder formulation of reaction rates. Complex reactions resulting from sequences of elementary reactions are examined, under steady-state conditions, both close to, and far from equilibrium. In the former case the over-all rate is proportional to the over-all affinity, while in the latter case, when all steps are far from their equilibria, the over-all rate varies exponentially with the over-all forward affinity. The problem of the identification of rate-determining steps is discussed on the basis of the adopted definition of elementary reactions. Application of the treatment to the two-step sequence A + B⇌C, C→D+E leads to a close connection with the absolute rate theory.
Spin-Orbit Coupling in the 3A2—1A1 Transition of Formaldehyde
Authors: Sidman Jerome W.
Published: January 2005

An approximate quantitative calculation is given for the effect of spin-orbit coupling in perturbing the 3A2 state of H2CO. The spin-orbit coupling mixes the 3A2 state with some higher singlet state, and allows the 3A2←1A1 transition to have nonvanishing probability. The calculations show that the 3A2←1A1, np→π2 transition of H2CO should be perturbed principally by the 1A1←1A1, π1→π2 transition. The bands of the 3A2←1A1 transition should therefore have the structure of a transition which is allowed by orbital symmetry with an oscillating electronic transition moment along the C–O axis (parallel bands). The oscillator strength, f, is calculated to be f3A2→1A1≅1.5×10−7. The natural radiative lifetime τ for the 3A2→1A1 phosphorescence transition is calculated to be τ≅1×10−2sec. The calculated value for τ is in agreement with the experimental values for the related molecules (CH3)2CO, (C6H5)2CO, and C6H5COCH3, insofar as a comparison can be made. It is further shown that the spin-orbit perturbation in the π→π* transitions of aromatic hydrocarbons should be about one thousand times less effective than the spin-orbit perturbation in the n→π* transitions of carbonyl compounds. This is in agreement with the few pieces of experimental data which have been reported thus far.
Internal Energy-Compressibility-Temperature Equation for Air in Dissociative and Ionic Equilibrium
Authors: Winchell Perrin
Published: January 2005

Based on the real gas data of Hilsenrath and Beckett, an equation E/RT=f(Z, T) is proposed to describe air in dissociative and ionic equilibrium over wide state-variable intervals. Used in conjunction with a suitable real gas state equation [e.g., Z=g(ρ, T)], an entropy-compressibility-density relation, and pertinent conservation equations, the proposed equation should complete a realistic, consistent set of dynamic and thermodynamic equations. The proposed equation exhibits excellent agreement with the data in sample calculations.
Statistical Mechanical Theory of Transport Processes in Liquids
Authors: Collins Frank C. , Raffel Helen
Published: January 2005

The hydrodynamic equations of the transport processes are developed in a form in which the irreversibility appears explicitly in terms of the instantaneous time derivatives of the stresses in a molecular scale nonequilibrium region of a system otherwise at equilibrium. The time derivatives of the stresses are shown to be proportional to the gradients of the properties being transported and to the squares of the transport coefficients. The corresponding time derivatives in the statistical mechanical treatment can be expressed as ensemble averages of molecular interactions using instantaneous values of the molecular pair density functions directly without recourse to time-smoothing with considerable gain in simplicity. Expressions for the transport coefficients are obtained by comparison of the hydrodynamic and statistical mechanical equations for the time derivatives of the dissipative stresses. The resulting hydrodynamic frictional and self-diffusion coefficients turn out to be identical to the expressions for these quantities provisionally suggested by Kirkwood, Buff, and Green. Relatively simple expressions are also obtained for the shear and volume viscosity and thermal conductivity coefficients in terms of integrals over space derivatives of the potential energy and the molecular pair density. It is further shown that, if an inter-molecular potential of the Lennard-Jones and Devonshire from is assumed, the integrals may be eliminated between these equations and the corresponding statistical mechanical equations for the hydrostatic pressure and the ideal heat of vaporization. This provides simple expressions for the shear vicsosity and the thermal conductivity coefficients directly in terms of the latter equilibrium properties. The numerical values obtained for the above two transport coefficients from evaluation of the integrals in the statistical mechanical equations and from the simple expressions in terms of equilibrium properties, are each in comparatively good agreement with experiment.
Microwave Absorption and Molecular Structure in Liquids. XXIV. The Dielectric Relaxation of Liquid Ammonia
Authors: Fish Kenneth , Miller Robert C. , Smyth Charles P.
Published: January 2005

Dielectric constant and loss measurements at wavelengths of 3.22 and 1.24 cm have been carried out upon liquid ammonia at temperatures from —55° to —35°C. The results have been used to calculate the approximate dielectric relaxation time values, 1.5×10—12 sec at —50° and 1.3×10—12 at —40°. The relaxation times and the liquid viscosities are much smaller than those of water, but extrapolation to the boiling points of the two liquids gives values of comparable magnitudes.
Paramagnetic Resonance in Rare Earth Trichlorides
Authors: Hutchison Clyde A. , Wong Eugene
Published: January 2005

Paramagnetic resonance absorption of all the naturally occurring rare earth trivalent ions in the LaCl3 structure have been investigated. The results are summarized in the form of a tabulation of the parameters g∥, g⊥, A, B, P, Δ in the spin-Hamiltonian. Theoretical calculations of crystal field states and eigenvalues as well as of g∥ and g⊥, based on optical measurements, are discussed.
Mobile Electron Model in a Magnetic Field
Authors: Weil John A.
Published: January 2005

The motion of an electron in a circular loop containing equally spaced Dirac delta-function potential spikes is considered. This problem is solved exactly for the case when a static magnetic field is present, and is of physical interest for the π-electron motions in benzene.
Vibration-Rotation Bands of Ammonia. III. The Region 3.2–4.3 Microns
Authors: Benedict W. S. , Plyler Earle K. , Tidwell E. D.
Published: January 2005

The weak absorption of NH3 between 2373–3080 cm—1 has been studied under high resolution, and a complete analysis given for over 1000 lines, including studies of the intensity and line width. The strongest bands (Sv0=0.44 and 0.20 cm—2 atmos—1, respectively) are 3ν28−0a and 3ν2a−08;ν3−ν2 (Sv0=0.074);ν3+ν2−2ν2 (Sv0=0.011);and ν2+ν4 (Sv0=0.06) have also been located. v2+v4 shows anomalous intensity behavior as well as large vibration-rotation-inversion-ζ-splitting interactions. The lines in 3v2 are 40–50% narrower than those in the microwave region, and appear symmetrical with no pressure shifts.
Calculation of the Energies of Gaseous Alkali Halide Dimer Molecules
Authors: Milne Thomas A. , Cubicciotti Daniel
Published: January 2005

The energies of formation of gaseous alkali halide dimer molecules from the monomers have been calculated with a model suggested by Pauling. The dimers were found to be from 40 to 60 kcal more stable, energetically, than their separated monomers. These results are in agreement with the experimental data available. The free energies of dimerization were estimated and used to predict the trends observed in the ratio of monomer to dimer for several salts. It was found that the energies of dimers with different cations were slightly more negative than the average of the two pure dimers. Some experimental results supporting this conclusion are presented.
Vibronically Induced Absorption of Forbidden Infrared Transitions
Authors: Thorson Walter R.
Published: January 2005

The usual selection rules governing the appearance of infrared fundamental frequencies in absorption are found to break down in the case that the molecule is in a degenerate electronic state capable of other vibronic interactions such as the Jahn-Teller effect. The intensity of such forbidden transitions is discussed and the conclusion reached that absorption is too weak to be observed except in such cases that the Jahn-Teller effect has produced sufficient distortion to destroy the symmetry of the original configuration and remove the electronic degeneracy; and under such conditions the previously ``forbidden'' transitions always become allowed by normal considerations for the nondegenerate electronic state of the molecule in the distorted configuration.
Perpendicular Bands of Allene and Allene-d4
Authors: Overend John , Crawford Bryce
Published: January 2005

The distribution of intensity in the perpendicular bands of allene has been examined, taking into account the effect of the Coriolis interaction between the degenerate levels v9 and v10. The results indicate that in all the perpendicular bands of allene and allene-d4 the RQ0 branch lies on a line which divides the band into two equal (or very nearly equal) areas. This has been used as a criterion for a new rotational assignment of these bands and the rotational constants A and ζ have been re-evaluated. The present A values, together with Stoicheff's (reference 16) B values indicate that the CH bond length is 1.061 A and the HCH angle 116°.
Calculation of Nuclear Magnetic Resonance Spectra of Aromatic Hydrocarbons
Authors: Johnson C. E. , Bovey F. A.
Published: January 2005

The free electron model of Pauling is used to calculate the magnetic field around a benzene ring which is rotating rapidly about all axes in an external magnetic field. It is assumed that the π electrons precess in two circular paths, one on each side of the ring, equal in radius to the C–C distance in the benzene ring. The separation of these rings is taken as 1.28 A, which gives a calculated value for the nuclear magnetic resonance shielding value for benzene protons equal to the observed value. The field thus calculated is employed to predict shielding values for other aromatic compounds. Agreement with experiment is in general good, but there are some exceptions.
Effect of Poisons on Crystal Growth
Authors: Sears Gerald W.
Published: January 2005

The effect of impurities is inexplicable by the accepted theory of crystal growth. In this report a mechanism is presented which describes the specific action of crystal-growth poisons.

By this model the step motion in growth is hindered and nucleation rate on an ideal surface is increased. To rationalize the effect of growth poisons it is necessary to postulate that complete monostep adsorption occurs at growth steps. In addition, the poison ion or molecule must present energetic and/or steric barriers to the addition of solute atoms so as to form an unpoisoned step by burying the adsorbed line of molecules.
Mass Spectrometric Study of the Vaporization of LiF, NaF, and LiF–NaF Mixtures
Authors: Porter Richard F. , Schoonmaker Richard C.
Published: January 2005

Vapors effusing from Knudsen cells containing LiF, NaF, and LiF–NaF mixtures have been analyzed mass spectrometrically. The over-all temperature range studied is between 900 and 1150°K. Monomers, dimers, and trimers of LiF and NaF are observed. The LiF system has the higher concentration of dimers and trimers. In the LiF–NaF system at 50 mole percent LiF the mixed dimer, LiNaF2, is the major polymeric vapor species. Thermochemical data for LiF(g), NaF(g), Li2F2(g), Na2F2(g) and Li3F3(g) have been obtained. For the reaction Li2F2(g)+Na2F2(g)=2LiNaF2(g), ΔH° is approximately zero.
Evidence for the Triplet State in Photoconductivity in Anthracene
Authors: Rosenberg Barnett
Published: January 2005

Some evidence is presented indicating that the formation of a triplet state is involved as an intermediary step in the creation and transfer of charges in the photoconduction process in organic substances. On the basis of the simple potential curve picture, approximate solutions are obtained to the rate process equations. These equations predict that the density of the triplet states under thermal and optical equilibrium conditions will follow a Boltzmann exponential dependence upon temperature with an energy equal to a low multiple (1 or 2) of the vibrational spacing of the excited singlet state. The assumption is made that the photocurrent is proportional to the triplet state density. Measurements by the author and others of the photoconduction activation energy in a number of aromatic hydrocarbons are in very good agreement with this. The triplet state model also requires that the buildup and decay of the photocurrents be approximately monomolecular with time constants at low temperatures and intensities equivalent to the lifetime of the triplet state. The experimental results corroborate this. The model also suggests that direct absorption into the triplet state should cause photoconduction. The experimental results with anthracene are not conclusive on this point.

The model of photoconduction in organic material is predicated on a molecular rather than an extended band model approach. The major contribution to the photocurrent comes from molecules which have undergone a spin conversion while in the excited state to the triplet state of the molecule. The long lifetime of this metastable state and the assumed partial localization of the uncoupled electrons increases the probability of an intermolecular quantum tunneling of the positive hole in the ground state orbital.
1,2- versus 1,4-Addition to 1,3-Butadiene by a Simple LCAO-MO Method
Authors: Pilar Frank L.
Published: January 2005

The addition of various reagents such as halogens and hydrogen halides to 1,3-butadiene by an ionic mechanism is ideally visualized as proceeding in two steps, viz., the electrophilic attack of the 1- or 2-position followed by nucleophilic attack to form either the 1,2- or 1,4-addition product. A simple LCAO—MO approach was applied to a proposed transition state arising from the first step of the reaction. Atom stabilization energies and frontier electron densities were calculated for the various positions of attack involved during the final step of the addition. The effect of the electronegativity of the group adding during the first step relative to the electronegativity of the carbon atoms in the conjugated system was used to alter certain of the LCAO—MO parameters. Agreement of the results with experiment is discussed briefly.
Molecular Diffusion Studies in Gases at High Temperature. II. Interpretation of Results on the He–N2 and CO2–N2 Systems
Authors: Walker R. E. , Westenberg A. A.
Published: January 2005

Experimental data on the binary diffusion coefficients of He–N2 and CO2–N2 obtained by the ``point source'' technique over the temperature range 300–1150°K are discussed in terms of intermolecular potential energies. For He–N2, the data can be satisfactorily represented by a purely repulsive potential. The data include the extremes of the concentration dependence for DHe–N2, i.e., with either He or N2 present only as a trace component, and this effect is taken into account in the theoretical interpretation. It is shown that, at their upper temperature limit, the data come within 150° of overlapping the range of validity for the diffusion coefficient predicted from the repulsive potential obtained by Amdur et al. from molecular scattering experiments. A slight interpolation indicates quite remarkable agreement between the two types of experiments. This is good evidence of the validity of predicting high-temperature transport properties from scattering potentials in certain cases—a possibility first pointed out by Amdur. A modified Buckingham (Exp-Six) potential is also obtained which covers both the diffusion and scattering potentials. For CO2–N2, the data are fitted with a Lennard-Jones (6–12) potential. It is shown that (for both He–N2 and CO2–N2) the predictions derived from viscosity parameters for the pure components and simple combining rules are quite unreliable at high temperatures.
Kinetic Studies of Hydroxyl Radicals in Shock Waves. II. Induction Times in the Hydrogen-Oxygen Reaction
Authors: Schott G. L. , Kinsey J. L.
Published: January 2005

The formation of OH in the shock wave induced combustion of H2 and O2 has been measured by oscillographically recording the absorption of ultraviolet OH line radiation. The main features of the reaction course are: (1) an induction period whose length, ti, varies inversely with [O2], (2) an increase in the product [O2] ti as ti becomes short compared to the vibrational relaxation time of O2, and (3) at the end of the induction period, a sigmoid rise of [OH] to a maximum, followed by a slow decrease. ti has been studied over the ranges: 1100°≤T≤2600°K, 1.3×10—5≤[O2]≤8.0×10—4 mole/1, 0.25≤[H2]/[O2]≤5., 0.004≤[O2]/[Ar]≤0.20, and 5≤ti≤500 μsec. Agreement between incident and reflected shock experiments has been demonstrated. According to the branching chain mechanism known from explosion limit studies, ti is governed by the rate of H+O2→ lim k1OH+O according to: 2 k1[O2]ti=2.303 n, where n is the number of decades by which [OH] increases between initiation and the end of the induction period. The values of [O2]ti, which is nearly proportional to 1/k1, are summarized by: log10([O2]ti) (mole 1—1 sec)= —10.647+(3966±625)/T. The value k1=1.4×109 deduced at 1650°K from this work is combined with data near 800°K to give: k1=3×1011 exp(—17.5±3. kcal/RT) (mole/1)—1 sec.—1. The relation of these results to detonation experiments is discussed.
Nuclear Magnetic Resonance Absorption in Glass. I. Nuclear Quadrupole Effects in Boron Oxide, Soda-Boric Oxide, and Borosilicate Glasses
Authors: Silver A. H. , Bray P. J.
Published: January 2005

The nuclear magnetic resonance spectrum of B11 has been investigated in several glassy materials containing boron oxide. A value of 2.76±0.05 Mc for the nuclear quadrupole coupling constant of B11 has been calculated from the second-order quadrupole perturbation of the m = ½→—½ resonance line. The same quadrupole interaction has been observed in pure boron oxide, B2O3, soda-boric oxide binary glasses, and two commercial borosilicate glasses. The quadrupole coupling constant is interpreted as arising from the bonding electrons in BO3 groups which comprise the glass network in boron oxide. Addition of oxygen ions to the glass network induces a change in the boron configuration from BO3 planar groups to BO4 tetrahedra resulting in a reduction in the quadrupole interaction. This effect has been observed in the Na2O–B2O3 glasses and in Corning ``Pyrex'' and 707 borosilicate glasses.
Study of Hydrogen Bonding in Systems of Hydroxylic Compounds in Carbon Tetrachloride through the Use of NMR
Authors: Saunders Martin , Hyne James B.
Published: January 2005

The hydroxyl NMR frequencies for t-butanol, phenol, and methanol have been measured as functions of concentration in carbon tetrachloride solution. The curves obtained were found to fit well to theoretical curves calculated for monomer-trimer equilibrium for t-butanol and phenol with K3=5.60 l2/M2 and 4.78 l2/M2, respectively and a monomer-tetramer curve with K4=28.4 l3/M3 for methanol. The data of Becker et al.1 on the ethanol-carbon tetrachloride system have been fitted to theoretical curves for monomer-trimer K3=5.19 l2/M2 and monomer-tetramer K4=44.9 l3/M3.
Potential Field and Force Constants of Octahedral Molecules
Authors: Pistorius C. W. F. T.
Published: January 2005

The force constants of 10 molecules and 5 ions of the type XY6 belonging to the Oh symmetry are calculated from the observed frequencies by Wilson's F—G matrix method, using Raman and infrared data. Although only one force constant is neglected, imaginary results were found in the cases of MoF6 and WF6. Possible causes for this are discussed.
Isotropic Nuclear Resonance Shifts
Authors: McConnell Harden M. , Robertson Richard E.
Published: January 2005

It is shown that isotropic (or average) nuclear resonance shifts for a nucleus in a paramagnetic molecule in solution, and in a polycrystalline solid, can be used to distinguish between Fermi contact and ``pseudocontact'' contributions to isotropic nuclear-hyperfine interactions. The pseudocontact interaction is that isotropic hyperfine coupling which arises from the combined effects of (electron-spin)-(nuclear-spin) coupling, (electron-orbit)-(nuclear-spin) coupling, and electron spin-orbit interaction. When the magnetic hyperfine interaction between the electronic moment and nuclear spin is approximated by a point dipolar interaction, and the isotropic hyperfine interaction is exclusively pseudocontact, then the isotropic nuclear shift in a polycrystalline solid exceeds the solution shift by the factor 3(g∥+g⊥)/(g∥+2g⊥) where g∥ and g⊥ are the spectroscopic splitting factors parallel and perpendicular to the molecular symmetry axis. Isotropic shifts due to the Fermi contact interaction are the same for both solid state and solution cases.
Structure in Ionic Solutions. III
Authors: Brady George W.
Published: January 2005

Measurements of x-ray scattering from ferric chloride solution in the concentration range from 1.5M to 5M have been made. The radial distributions calculated from these measurements indicate a large degree of local ordering of the ions, with formation of Fe+3—Cl— complexes. At the highest concentration the [FeCl6]—3 ion appears to be the main species present. As the concentration is lowered the coordination of the Cl—s around Fe+3 becomes less definite and other species appear; in particular, the presence of Fe2Cl6 is indicated.
Low Frequency Dispersion in Ionic Crystals
Authors: Breckenridge R. G.
Published: January 2005

A new region of anomalous electrical response has been observed at low frequencies in ionic crystals that have been treated to introduce relatively large number of lattice defects. The crystals thus far studied include various alkali halides and silver chloride. The effect is attributed to a jumping of the positive ions to vacant lattice sites under the influence of the applied field. This jumping is observed as a relaxation process, producing a change in the dielectric constant which is small and frequently within the limits of error of measurement, and an associated peak in the dielectric loss tangent which is readily measurable. This maximum of tan δ has been studied both as a function of frequency at a fixed temperature and as a function of temperature at fixed frequency. From the magnitude of the peak and position on the frequency or temperature scales it is possible to calculate the number of lattice defects present in the sample and the activation energy for diffusion U of the positive ion in the crystal. A knowledge of U allows a separation of the activation energy for conduction, (W/2)+U, into its components, thus determining W, the activation energy for hole formation.
Carbon-Hydrogen Bond Strengths in Methane
Authors: Voge H. H.
Published: January 2005

Earlier formulas for the electron-pair bonding energies of methane, and radicals derivable from methane, are combined with recent data on the energy levels of the carbon atom, the heat of sublimation of carbon, the energy for removal of the first hydrogen, and the dissociation energy of CH to obtain the energies of CH3 and CH2. A consistent set of values is found which is in agreement with a heat of sublimation of carbon of 120–140 kcal. and gives for the energies of successive removals of hydrogen atoms from methane 101, 90, 80, and 80 kcal., respectively.
A Tabulation of General Formulas for Inverse Kinetic Energy Matrix Elements in Acyclic Molecules
Authors: Decius J. C.
Published: January 2005

In terms of internal coordinates of the bond stretching and bending type, together with a torsional type of coordinate, general formulas for inverse kinetic energy matrix elements have been computed for all 33 possible acyclic configurations involving the given types of coordinates. Tabulations are given both for the general case and for three special cases in which all valence angles of the configuration are assumed to be 90°, 109°28′, and 120°, respectively.
Thermodynamic Functions for Tritium and Tritium Hydride. The Equilibrium of Tritium and Hydrogen with Tritium Hydride. The Dissociation of Tritium and Tritium Hydride
Authors: Jones W. M.
Published: January 2005

The heat capacity, entropy, internal energy, and free energy are calculated to 2500°C for tritium and tritium hydride. The distribution of tritium between the ortho and para states is considered. The equilibrium constant for the formation of tritium hydride from hydrogen and tritium is calculated from 50°K to 2500°K. The dissociation of tritium and tritium hydride into the atoms is discussed. The bearing of the radioactivity of tritium and tritium hydride on the attainment of thermodynamic equilibrium is briefly considered.
Apparatus and Methods for Measurement and Interpretation of the Angular Variation of Light Scattering; Preliminary Results on Polystyrene Solutions
Authors: Zimm Bruno H.
Published: January 2005

A photoelectric apparatus for the measurement of the angular dependence of light scattering from solutions is described in detail and its performance is discussed. Methods of calculation for the determination of the average extension of the scattering molecules from the data are described. Data are presented for two fractions of polystyrene in various solvents, showing the effect of changing solvent power and temperature, and also confirming a theoretically derived formula for the concentration dependence of the scattering.
Does Ultraviolet Absorption Intensity Increase in Solution?
Authors: Jacobs Lois E. , Platt John R.
Published: January 2005

Absolute absorption intensities and oscillator strengths were determined for isoprene and cis- and trans-piperylenes in the region 1750–2400A, in vapor and in n-heptane solution, using a vacuum fluorite spectrograph. More accurate oscillator strengths are obtained if our measurements at short wave-lengths are combined with the Beckman data of Shell Development Company at longer wave-lengths.

For the three compounds the best values of the experimental Lorentz-Lorenz correction, or ratio of integrated intensities under the molar absorption curves for solution and vapor, were close to unity, a result obtained previously by Pickett and co-workers for cyclopentadiene and cyclohexadiene absorption in this same region. A value of 0.98±0.04 for this correction represents the mean of all five of these determinations. Although the values obtained from our data alone without using the Shell curves showed a much larger spread, every determination was substantially below the correction factor of 1.30 predicted by Chako's classical oscillator theory for this wave-length region and these solvents.
Ionization Potentials of Some Hydrocarbon Series
Authors: Honig Richard E.
Published: January 2005

A new method is described which permits ionization and appearance potentials to be determined reproducibly, within ±0.02 volt, by electron impact in a conventional 180° mass spectrometer. The energy spread of the ionizing electrons, while not eliminated, is accounted for in an analytical expression that describes the ionization efficiency curve of argon near the initial upward break. It is shown that an ionization or appearance potential can be determined graphically by drawing a tangent of critical slope to the efficiency curve which has been plotted on a semilog scale. Absolute values are obtained by referring the unknown to the ionization potential of a calibrating gas (usually krypton). For the monatomic gases studied, electron impact and spectroscopic values agree within the experimental uncertainty. For some known polyatomic molecules, the ``vertical'' impact values exceed the ``adiabatic'' spectroscopic potentials by 0.02 to 0.2 volt, depending on molecular complexity. Paraffins, 1-olefins, and 2-olefins show a systematic reduction in potential with chain length. A similar decrease is observed when the mono-olefins are arranged according to the number and size of substitutions on the basic ethylene structure.
Search for Near Ultraviolet Bands in Borazole
Authors: Jacobs Lois E. , Platt J. R. , Schaeffer G. W.
Published: January 2005

Borazole, B3N3H6, shows no absorption bands in the region 2000A−4600A, at pressures of about 2 atmospheres in a 4-cm cell. Since bands analogous to those of benzene are expected on theoretical grounds, it is concluded that the analogues of the benzene 2600A and 1830A bands are the borazole 1995A and 1720A bands, with the analogues of the benzene 2080A bands perhaps being hidden in between.
Absorption of the Alkyl Cyanides in the Vacuum Ultraviolet
Authors: Cutler Janice A.
Published: January 2005

The vacuum ultraviolet spectra of methyl and ethyl cyanide have been determined in the region 1000A to 1800A. Three members of a Rydberg series were found for methyl cyanide starting at 1292A, the limit of the series corresponding to an ionization potential of 11.96 ev. Vibrational band changes which have been found to accompany the first two members have been assigned to fundamental frequencies of the molecule by comparison with Raman data. The electronic transition, expressed by the Rydberg series, was ascribed to excitation of a π electron in the triple bond. At higher pressures, a continuous absorption appeared which was followed only to 1600A. No structure could be observed in the spectrum of the ethyl cyanide, although it paralleled that of methyl cyanide in having a stronger absorption starting at 1342A and a weaker one appearing at higher pressures and spreading to longer wave-lengths.
Low Temperature Transport Properties of Gases. II. Neon, Argon, Krypton, and Xenon
Authors: Amdur I.
Published: January 2005

Values are computed for the viscosity, thermal conductivity, and coefficient of self-diffusion, as functions of temperature, for the following gases: neon (60°−200°K), argon (110°−290°K), krypton (150°−370°K), and xenon (210°−550°K). The method of calculation is the same as that previously developed for gaseous helium and involves the use of classical scattering theory within angular regions where diffraction effects are absent, to obtain appropriate classical transport cross sections for insertion into the exact formulas of Chapman and Enskog.

The average absolute deviations between calculated and experimental values are 5.5 percent for viscosity and 5.9 percent for thermal conductivity. In the case of self-diffusion, only two experimental values are available for comparison with calculated values, one each for krypton and xenon. The absolute deviations are 9.7 and 10.3 percent, respectively.

A procedure is suggested for obtaining approximate values of the mutual diffusion coefficient of a binary gas mixture from the self-diffusion coefficients of the constituents.
On the Nature of the Interaction between Starch and Iodine
Authors: Stein R. S. , Rundle R. E.
Published: January 2005

(1) It is postulated that the interaction between starch and iodine in the amylose-iodine complex is of dipolar nature.

(2) A model for such dipolar interaction is proposed and the necessity for a cooperative effect is discussed.

(3) The interaction energy is calculated as a function of a parameter x and it is shown that this parameter possesses a critical value at which a ``condensation'' of iodine into the complex occurs.

(4) It is demonstrated that it is physically reasonable for this parameter to attain its critical value.

(5) It is shown that additional stabilization may occur as a result of the formation of a resonating ``polyiodine'' chain at high dipolar interaction having a I–I distance and heat of formation which compares favorably with experiment.

(6) Application of the theory is made in discussing the stability of the polyvinyl alcohol-iodine complex.

(7) The color of these complexes is discussed in terms of the theory.
The Molecular Structure of Nitrogen Dioxide. A Reinvestigation by Electron Diffraction
Authors: Claesson Stig , Donohue Jerry , Schomaker Verner
Published: January 2005

An investigation of the structure of the nitrogen dioxide molecule has been made by the electron diffraction method. The interpretation of the photographs, which showed rings extending to values of q of nearly 100(q = 40/λ sinτ/2), leads to the following structural parameter values: N–O = 1.20±0.02A, <O–N–O = 132±3°. These values are discussed briefly and compared with those obtained by other methods.
Thermodynamics of the System Benzene-Biphenyl
Authors: Tompa H.
Published: January 2005

The vapor pressure of benzene and the heat of dilution of benzene-biphenyl mixtures have been measured at 25°C. The results are shown to be in fair agreement with Guggenheim's formulae based on the lattice model, assuming that the biphenyl molecule occupies twice the volume of the benzene molecule, and that the coordation number of the lattice is between 6 and 12. No agreement can be obtained if the effect of the different sizes is neglected.

The experimental results of other authors are critically examined and shown to conform to the above picture.
The Surface Tension of Liquid Metals
Authors: Skapski Adam S.
Published: January 2005

The author is opposed to the generally established opinion that the surface tension of liquid metals is abnormally high (as compared with that of non-metallic liquids) and that the metallic character (the presence of free electrons) is the main cause of the ``high'' surface tension of metals. He shows that this opinion is due to the fact that specific surface tensions (ergs per cm2) are compared and that the influence of temperature is not accounted for. Total surface energies σM—T(dσM/dT)—where σM=σspec×A is the surface tension referred to the surface A occupied (in monomolecular layer) by N-Avogadro's molecules—are of the same order of magnitude.

The author expresses the opinion that the main cause of the surface tension of all liquids, whether metallic or not, is the same, viz., the total surface energy is determined by the amount of energy required to bring the molecules or atoms (and electrons) from the bulk of the liquid to its free surface while enlarging the surface area. He shows that in organic liquids showing no dipoles this energy can be calculated directly from the heat of vaporization at absolute zero and from the configuration of nearest neighbors. In the case of metals, the change of kinetic energy of electrons must be considered in addition. The author shows that the latter must contribute a negative term to the total surface energy. In fact, liquid metals show lower surface energies than might be expected from their heats of vaporization and from the configuration of their nearest neighbors (Fig. 1).

A short review of the recent electron theories of the surface tension of liquid metals is given.
Physical Interaction of Electrons with Dielectric Media
Authors: Hill Terrell L.
Published: January 2005

Ogg's rough calculation indicating the relative ground state energetic stability of paired electrons as compared to unpaired electrons in certain dielectric media was repeated but with the opposite result. However, an approximate consideration of the complete equilibrium constant rather than just the energy factor alone suggests that a considerable number of pairs may indeed be present. The case in which the polarization of the dielectric is able to follow in detail the motion of the charged particle or particles within a cavity is also discussed.
The Vapor Pressure of Uranium Hexafluoride
Authors: Weinstock B. , Crist R. H.
Published: January 2005

The vapor pressure of uranium hexafluoride, UF6, has been measured from 273°K to 358°K. The measurements were made by a null method in an all metal apparatus with a brass sylphon bellows. The data are represented by the equations: Solid−vapor log10P(mm Hg)=−3.77962 log10T−(3123.479/T)+21.87103,Liquid−vapor log10P(mm Hg)=−3.72662 log10T−(2065.679/T)+18.60033.The constants in the equations were adjusted so that the equations would give the same heat of fusion and triple-point temperature as was determined by Brickwedde, Hoge, and Scott. The vapor pressure at the triple point is 1133±7 mm. The sublimation point at which the vapor pressure is 1 atmosphere is 56.5°C. The heat of vaporization has been calculated using the Berthelot equation to obtain the vapor volume. From this and the entropies measured by Brickwedde, the absolute entropy of the gas has been calculated.
The Calculation of Perturbation Energies in Vibrating Rotating Polyatomic Molecules
Authors: Herman Robert C. , Shaffer Wave H.
Published: January 2005

An account is presented of the calculation of the purely vibrational contribution to the eigenvalues of the vibration-rotation Hamiltonian of a polyatomic molecule. Special attention is given to the expansion of the quantum-mechanical Hamiltonian; and to the results of the contact transformation of the Hamiltonian which simplifies the calculation of the second-order energy corrections. The results of the transformation theory have been presented in the form of tables. For each type of perturbation term which appears in the first-order Hamiltonian it is possible to obtain the second-order energy corrections by inspection. This procedure eliminates the need for applying the transformation to each specific problem. The use of these results is illustrated by working out in considerable detail the case of the X2YZ2 tetrahedrally symmetric molecular model.