bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared Absorption of Zinc Oxide and of Adsorbed CO2. I
Authors: Matsushita Sanjuro , Nakata Toshiko
Published: January 2005

For measuring the absorption spectra of a powdered solid in contact with a gas and adsorbed gas molecules, a new disk technique has been developed by which the powder can be formed into optical samples having sufficiently high transmissivity and a well-defined thickness. By the use of this technique the spectrum of zinc oxide under varying heat treatments and gaseous conditions was studied at 20° and 300°C mainly in the region 2000∼1200 cm—1. With samples made from zinc nitrate and evacuated at 300°C a distinct symmetrical band was observed at 1550 cm—1 which was investigated in detail. From its intensity, behavior, and correlation with absorption by free electrons, the band was attributed to an electronic absorption associated with zinc vacancies in the crystal lattice. Samples made from zinc carbonate showed strong absorption by free electrons on being evacuated, affording a useful basis for observing its variation.
Electronic Structure of LiH. V. A Radially Correlated Wave Function
Authors: Robinson J. M. , Stuart J. D. , Matsen F. A.
Published: January 2005

The electronic energy and dipole moment of LiH have been calculated with valence-bond wave functions into which some radial correlation has been introduced by assigning different orbitals to different electrons. The energy as calculated from the radially correlated functions is 0.76 ev lower than from the corresponding uncorrelated functions. The calculated dipole moment agrees well with that obtained in previous calculations. Moffitt's concept of ``atoms in molecules'' is applied to the correlated and uncorrelated functions.
On the Mechanism of the Lewis-Rayleigh Nitrogen Afterglow
Authors: Bayes K. D. , Kistiakowsky G. B.
Published: January 2005

The relative intensities in the nitrogen afterglow, from 5000 to 11 000 A, have been measured in pure nitrogen and after addition of several foreign gases. Most of the bands in the recently discovered Y — B 3Πg system are overlapped by B 3Πg — A 3Σu+ bands but intensity assignments have been made. Changes in relative intensities accompanying changes in external conditions show that the bands can be classified into five groups of different kinetic origins. The vibrational levels of the B 3Πg and Y states just below De, the energy of two separated ground state nitrogen atoms, are not populated. At low temperature the highest populated levels of the B 3Πg and Y states tend to a limit about 850 cm—1 below De. It is suggested that this is approximately equal to the dissociation energy of the 5Σg+ state of the nitrogen molecule. Some of the emission from the low vibrational levels of the B 3Πg state is associated with the radiation cascade Y→B 3Πg→A 3Σu+, but the rest has a different kinetic origin. The emission from B 3Πg (v=7, 6, 5) is probably the second step in the cascade 3Δu→B 3Πg→A 3Σu+.

Foreign gases modify the vibrational population distribution of the upper levels of the B 3Πg state, each in its characteristic fashion. Some gases quench the emission from the lowest vibrational levels of B 3Πg more effectively than the rest of the spectrum. The quenching of the emission from the higher levels depends on the pressure of nitrogen. A mechanism accounting for most of the afterglow emission is discussed.
Computation of the Equilibrium Composition of Burnt Gases
Authors: Potter Robert L. , Vanderkulk Wouter
Published: January 2005

The multicomponent chemical equilibrium composition problem is discussed generally and a formulation of it is presented in a form suitable for digital computer calculations. A geometric interpretation of the equations used to specify the chemical system is also given.
Statistical Mechanical Theory of the Diffusion Coefficients in Binary Liquid Solutions
Authors: Bearman Richard J.
Published: January 2005

The statistical mechanical theory of the diffusion coefficients in binary liquid solutions is developed from the viewpoint of the pair space linear relations. Equations for the composition dependence of the ratios of the friction and diffusion coefficients are developed. For solutions which are regular it is found that the ratio of the two self-diffusion coefficients is in the inverse ratio of the corresponding molar volumes. The assumptions of the theory are discussed critically.
Nuclear Magnetic Resonance Spectra of Some Simple Epoxides
Authors: Reilly C. A. , Swalen J. D.
Published: January 2005

High resolution NMR spectra of four epoxides have been observed at 40 Mcps and analyzed. These epoxides are of the type[Complex chemical formula]where R is a phenyl group (styrene oxide), a cyanide group (glycidonitrile), an acetyl group (1,2-epoxy-3-butanone), and a carboxyl group (glycidic acid). For each molecule the spin-spin coupling constants and nuclear magnetic screening parameters for the A, B, and C protons were derived from the experimentally determined energy levels. The method for obtaining numerical values for the energy levels from the spectra is described fully. ABK and AA′K approximations as well as an iterative ABC method of solution are described and illustrated.

Corresponding coupling constants are found to be about the same in all four molecules with JAB=5.8±0.5 cps, JAC=2.2±0.5 cps and JBC=4.6±0.5 cps. However, the variations from molecule to molecule are considerably greater than the estimated precision of ±0.05 cps. The ABX approximation is shown to be inadequate either for the precise determination of the constants or for the calculation of relative intensities. As compared with the iterated ABC solution, the ABK or AA′K approximation leads to good values for the constants and adequately describes the relative intensities.
Determination of the Dipole Moment Function from Infrared Band Intensities of Diatomic Molecules
Authors: Herman Robert , Rubin Robert J.
Published: January 2005

A discussion is given of the relations which exist among vibrational matrix elements for diatomic molecules represented as Morse oscillators. This is done according to the wave function approximation of Trischka and Salwen. It is shown how the matrix element of the dipole moment Mvi′ is related to the matrix elements M0i where v′—v≤i≤v′+v with v′>v. This relation is examined for the case of the 1–2 band of HCl. It is also shown how the matrix element M01 for DCl can be related to the matrix elements of HCl. Finally, the influence of the vibration-rotation interaction is incorporated in the wave function approximation. In an example, it is shown that the matrix element {M0,Ji,J+1 can be expressed in terms of the set of matrix elements{M0,0i,1},i=0,1,··· .
Simple Configuration-Interaction Wave Functions. I. Two-Electron Ions: A Numerical Study
Authors: Silverman J. N. , Platas O. , Matsen F. A.
Published: January 2005

The ground state energies of the two-electron ions from H— to Ne8+ are calculated for the simple wave function (1s1s′)+λ(2p)2 with optimized orbital exponents. The use of the difference between the calculated energy and the experimental energy as a function of the atomic number for accurate extrapolation is explored. The expectation values of the operators rn(n≥—2), δ(3)(r1), and δ(3)(r12) are compared with those obtained from more accurate wave functions.
Nuclear Magnetic Resonance Study of Polycrystalline NH4ClO4
Authors: Ibers James A.
Published: January 2005

The second moments of the proton resonance absorption line in polycrystalline NH4ClO4 are found to be 1.27±0.02 gauss2 at 70°K and 1.18±0.01 gauss2 at 298°K; these results are interpreted in terms of reorientation of the ammonium ion about random or nearly random axes. Spin-lattice relaxation times for polycrystalline NH4ClO4 have been measured between 77° and 298°K by the progressive saturation method. These relaxation times are consistent with a barrier hindering reorientation of 2.0±0.6 kcal.
Some Notes on Molecular Complexes between Iodine and Polynuclear Aromatic Hydrocarbons
Authors: Chowdhury Mihir , Basu Sadhan
Published: January 2005

It has been observed that when iodine concentration is high in a mixture of iodine and polynuclear aromatic hydrocarbon in carbon tetrachloride, the spectral data may be interpreted on the assumption of 2:1 molecular complex formation between iodine and aromatic hydrocarbon. The equilibrium constants for 2:1 complexes were, however, found to be much higher than those of the corresponding 1:1 complexes and they were further found to be independent of the nature of the hydrocarbon. Interpretation of the experimental data based on contact charge transfer appears to be much more reasonable in the present case.
Emission of Activated Cadmium Selenide Phosphors
Authors: Avinor M. , Meijer G.
Published: January 2005

The emission bands of cadmium selenide activated by silver, copper, and gold, and coactivated by trivalent metals, were found at 0.92, 1.20, and 1.45 μ, respectively, at the temperature of liquid nitrogen. The silver band is completely quenched at room temperature. A near edge emission of CdSe was found at 0.72 μ.
Spin Densities in Dimesitylmethyl
Authors: McLachlan A. D.
Published: January 2005

A simple valence bond calculation indicates that if the dimesitylmethyl radical were planar large unpaired spin densities would appear on the ring methyl groups giving a spectrum about 130 gauss wide. A perturbation calculation, assuming that the molecule is very twisted, gives spin densities ρ1=1.000, ρ2=—0.069, ρ3=0.054, ρ4=—0.040, ρ5=0.043 on the carbon atoms, numbered from the center outwards.
Variational Principles for Chemical Equilibrium
Authors: Dorn W. S.
Published: January 2005

Two variational principles for the chemical equilibrium of a gaseous mixture are formulated. These provide a means for calculating upper and lower bounds to the energy of the equilibrium mixture.
Becquerel Photovoltaic Effect in Binary Compounds
Authors: Williams Richard
Published: January 2005

An experimental study has been made of photovoltaic effects which occur at semiconductor-electrolyte interfaces. Single crystal specimens of CdS and several other compounds were used. It was found that in a number of cases the photovoltaic effect results from a chemical reaction of the electrode materials. In such cases the observations may be explained by a simple mechanism which relates the sign of the photo-emf to the conductivity type of the semiconductor and to the chemical reaction which is occurring. The reaction may be predicted using readily available thermodynamic data. A different process occurs when the electrode material is GaAs. It acts as an inert electrode which exchanges electrons with an oxidation-reduction couple in the solution.
Vibrational Frequencies of Alkali Halide Dimers. II. Bending, Symmetric Stretch, and B1g Modes
Authors: Berkowitz Joseph
Published: January 2005

Three of the normal vibrational frequencies of alkali halide dimers are calculated on the basis of the potential function for an ionic model. The results indicate that the out-of-plane bending mode may have a frequency almost as high as the in-plane stretching frequencies. A summary of the results of calculations for the six normal modes is presented.
Crystal Field Splitting of Energy Levels of Thulium Ethylsulfate
Authors: Gruber John B. , Conway John G.
Published: January 2005

The operator-equivalent method was employed to calculate the theoretical splitting of electronic energy levels 3P2, 1D2, 3F2, 3F3, 3F4, 1G4, and 3H6 in Tm(C2H5SO4)3·9H2O. Intermediate field corrections were made to α, β, and γ. A first-order perturbation treatment on Tm3+ (4f12) in C3h symmetry, using crystal-field parameters A20〈r2〉=13 cm—1, A40〈r4〉=—80 cm—1, A60〈r6〉=—32 cm—1, and A66〈r6〉=300 cm—1, predicts the position of the crystal quantum states in reasonable agreement with experiment.
Radiation Damage in Organic Crystals. II. Electron Spin Resonance of (CO2H)CH2CH(CO2H) in β-Succinic Acid
Authors: Heller Chonon , McConnell Harden M.
Published: January 2005

An analysis of the electron spin resonance of x-irradiated single crystals of β-succinic acid shows that: (a) the principal long-lived paramagnetic species produced by the radiation damage is (CO2H)CH2–ĊH(CO2H); (b) the radical is oriented in the crystal lattice in nearly the same way that the parent succinic acid molecule is oriented in the undamaged lattice; (c) the strongly anisotropic hyperfine interaction due to the σ proton is very nearly the same as that previously found for the σ proton in the malonic acid radical, (CO2H)ĊH(CO2H). In these molecules the σ proton is directly bonded to the carbon atom on which the odd electron is largely localized. The two methylene protons in the radical are not equivalent, and their hyperfine interactions are nearly isotropic, and in the range 80–100 Mc.
Second Differences of Moments of Inertia in Structural Calculations: Application to Methyl-Fluorosilane Molecules
Authors: Krisher Lawrence C. , Pierce Louis
Published: January 2005

An extension and application of the method recently proposed by Pierce for the location of ``near-axis atoms'' from spectroscopically determined moments of inertia is made. Equations are derived which are required for the application of the method to asymmetric top molecules with Cs symmetry. The method is applied to the determination of silicon coordinates in the molecules CH3SiH2F and CH3SiHF2. The experimental results are combined with results of previous microwave investigations of these molecules in order to determine their structures. Addition of each fluorine atom lowers the SiC distance. The SiF distance is lowered on adding the second fluorine. In the case of CH3SiHF2 the equilibrium conformation (staggered) is also determined.
Rotational Diffusion Constant of a Cylindrical Particle
Authors: Broersma S.
Published: January 2005

The torque constant of a closed cylinder rotating in a viscous medium has been calculated for length (2a) over width (2b) ratios larger than 3.5 to within a first order in b/a. The analysis demonstrates how the contributions to the viscous dissipation tend to be underestimated in hydrodynamic considerations so that the geometrical values deduced from them come out too high. Experimental results for the torque on cylindrical rods and ellipsoids for a/b values from 3.5 to 30 are close to the theoretical results. For a/b>10 the difference is about 10%; for shorter molecules 20%. With the rotational diffusion constant given by 3kT (σ—γ)/8πηa3ω, where σ=log2a/b we obtain best fit with γ(σ>2)=1.57–7 (1/σ—0.28)2±0.25. Experimental data for the rotational diffusion constant of a cylindrical virus (a/b=20) in water, obtained by O'Konski and Haltner agree with this result within 10%. The length of the protein fits within 3%.
Viscous Force Constant for a Closed Cylinder
Authors: Broersma S.
Published: January 2005

The viscous force constant of a moving cylinder closed at the ends has been calculated including first-order effects in width (2b)/length (2a). Experimental results, obtained for macroscopic models, are in essential agreement with this. For a/b>20 the discrepancy is about 8%, for shorter cylinders near 20%. With the force on a cylinder moving sideways given by F=8πηav/(σ—γ), where σ=log2a/b, it is found that γ(σ>2)=0.35–4(1/σ—0.43)2±0.25. For a translation lengthwise, with F=4πηav/(σ—γ), the relation γ(σ>2)=1.30–8(1/σ—0.30)2±0.25 holds.
Analysis of the Nuclear Magnetic Resonance Spectrum of a Six-Spin System of Monofluorobenzene
Authors: Fujiwara Shizuo , Shimizu Hiroshi
Published: January 2005

This paper is concerned with the general analysis of a six-spin system belonging to the point group C2V, using monofluorobenzene as an example. The apparatus used for the NMR measurements is the one constructed in this laboratory, operating at 27.030 Mc. The absorption lines calculated suggest the doublet structure of the spectrum, which is consistent with the observed spectrum. It was confirmed that this doublet structure is due to the spin-spin couplings of the ring protons with fluorine. More precise comparison of the calculated results with the observed spectrum was made by integrating the intensities of the lines having a suitable line shape and width. It was noted that this procedure for constructing the absorption spectrum from the calculated lines is useful in the discussion of the power of resolution of the apparatus and the type of line shape.
Relative Signs of Spin-Spin Interactions in Nuclear Magnetic Resonance. II
Authors: Alexander S.
Published: January 2005

The spectrum of the allyl group in allyl amine is discussed in detail. The interpretation of the spectra of 1-butene and 3,3-dimethyl-1-butene are also discussed. It is shown how the chemical shifts, spin-spin interactions, and in particular the relative signs of the latter can be determined by numerical methods.

In all three molecules all spin-spin interactions among the vinyl protons have the same sign. One of the three vinyl-methylene interactions is found to have a different sign than the other two. This interaction has the same sign (and approximately the same magnitude) as the methyl-methylene interaction in 1-butene.
Thermal Diffusion of Ternary Mixtures
Authors: de Vries A. E. , Laranjeira M. F.
Published: January 2005

Experiments have been performed on ternary mixtures, consisting of two isotopes and a nonisotopic compound. It is found that the influence of the third compound on the separation of the isotopes cannot always be foreseen, the hardness (RT value) being of extreme importance.
Method for Calculating Average Molecular Weights and Molecular Weight Distributions of Polymeric Materials from Sedimentation Equilibrium Experiments
Authors: Fujita Hiroshi
Published: January 2005

A method is proposed for the determination of average molecular weights and molecular weight distributions of polymeric materials from sedimentation equilibrium experiments in theta solvents. The data required are the refractive index gradients at the center of the ultracentrifuge cell as a function of a parameter λ = (1—v̄ρ0) (r22—r12)ω2/2RT; here v̄ is the partial specific volume of the polymer solute in the given solvent, ρ0 is the density of the solvent, ω is the rotor speed, r1 and r2 are the radial distances from the rotor axis to the meniscus and the bottom of the cell, respectively, T is the absolute temperature, and R is the gas constant. The most important feature of the proposed method is that it allows calculation of the number-average molecular weight. The desired distribution of molecular weights of a given sample can be obtained by solving an integral equation of the Fredholm type.
Rotation-Vibration Interaction in Electronic Transitions. Application to Rotational ``Temperature'' Measurements
Authors: James Thomas C.
Published: January 2005

The effect of rotation-vibration interaction on line intensities in electronic transitions in diatomic molecules is discussed. It is shown that this effect is closely related to the variation in the electronic transition moment with internuclear distance. The relation of this to the determination of rotational temperatures is discussed, using the OH radical as an example. It is shown that a neglect of this interaction can lead to the observation of apparently abnormal temperatures.
Application of Least-Squares Method to Gaseous Benzene in Electron Diffraction Investigation
Authors: Kimura Katsuma , Kubo Masaji
Published: January 2005

The intensity data of gaseous benzene obtained at 18°C by the sector-microphotometer technique in electron diffraction were analyzed by use of a least-squares method, D6h symmetry being assumed for the molecule. A total of thirteen parameters comprising two bond distances, seven root-mean-square amplitudes, three background parameters, and one intensity scale factor were refined in the least-squares treatment. Uncertainties in these parameters were determined by computing standard errors due to the over-all errors involving systematic and random errors. Results for bond distances r and root-mean-square amplitudes l are as follows: r(C–C)=1.3969±0.003 A;r(C–H)=1.0845±0.0020 A;l(C1–C2)=0.0456±0.003 A;l(C1···C3)=0.0555±0.005 A;l(C1···C4)=0.0614±0.009 A;l(C1–H1)=0.0748±0.010 A;l(C1···C3)=0.0975±0.008 A;l(C1···H3)=0.0925±0.016 A;l(C1···H4)=0.0960±0.0023 A. These values were compared with data available in the literature. An empirical formula is proposed for experimental background scattering and the selection of weighting factors in least-squares refinement is discussed.
Electronic Structures and Spectra of Nitromethane and Nitrogen Dioxide
Authors: McEwen K. Lenore
Published: January 2005

The electronic structures and spectra of nitromethane and nitrogen dioxide have been calculated by a semiempirical method. The self-consistent molecular orbitals and energies of the π-electron system have been calculated; however, for the nonbonding σ-electron system Hückel-type molecular orbitals are used. The nonbonding 2p oxygen orbitals of nitromethane are very slightly modified by mixing with the σ-electron system; in nitrogen dioxide, on the other hand, the totally symmetric combination of 2p oxygen orbitals and the sp2 nonbonding nitrogen orbital mix strongly to form slightly bonding and slightly antibonding molecular orbitals. The calculated transition energies of nitromethane are in reasonable agreement with experiment. For nitrogen dioxide a series of transition energies are obtained which may illuminate experimental results; the complexity of the empirical data, however, and the multitude of calculated low-energy excited states, preclude definite assignment of the observed band systems at this stage.
Redetermination of the Intermolecular Potential for Krypton
Authors: Mason Edward A.
Published: January 2005

The intermolecular potential for krypton has been redetermined from transport property data, including new experimental results on thermal diffusion and thermal conductivity. Both the Lennard-Jones (12–6) and the exp-6 potential functions have been used and reproduce the data about equally well. The parameter α of the exp-6 potential is not uniquely determined by the data, but a tentative selection of α=13.5 has been made semiempirically on the basis of the theory of the dispersion energy and the consistency with the other rare-gas potentials. The most important conclusion is that there is a large discrepancy, not found for the other rare gases, between the present results and the experimental crystal properties and second virial coefficient. No amount of parameter adjustment has been able to reduce the discrepancy to a reasonably acceptable value. Possible explanations and implications of this unusual and unsatisfactory situation are discussed.
Theory of Dilute Polymer Solution. III. Heterogeneous Polymer
Authors: Yamakawa Hiromi , Kurata Michio
Published: January 2005

The second virial coefficients of osmotic pressure and light scattering of heterogeneous chain polymer solutions are calculated to the double-contact approximation. Two types are assumed for the molecular weight distribution: the Schulz distribution, and the distribution with two deltalike peaks.

Then, the heterogeneity corrections for intrinsic viscosity are evaluated on the assumption of the Schulz distribution. On the basis of the results obtained, a tentative attempt is made at interpreting the proportionality between the intrinsic viscosity at the Θ temperature and the square root of the molecular weight without discarding the hydrodynamic scheme, and the relation between the hydrodynamic and statistical radii of heterogeneous polymer coil is also examined.

Finally, the relation between the second virial coefficient A2 and intrinsic viscosity [η] is discussed somewhat in detail. And it is shown that the initial curvature of the curve of [η]/[η]θ — 1 vs A2Mw/[η]θ is concave upward for ordinary fractionated samples, where [η]θ is the intrinsic viscosity at the Θ temperature, and Mw is the weight-average molecular weight. This statement is verified by comparison with experiment.
On the Assumptions Underlying Droplet Vaporization and Combustion Theories
Authors: Williams F. A.
Published: January 2005

A study is undertaken to determine the range of validity of the assumptions that (a) the liquid temperature is constant and equal to the boiling temperature for a burning droplet, (b) the instantaneous vaporization rate of a droplet at a given size is the same as that of a constant-diameter sphere of the same size, and (c) the duration of the initial unsteady period is much less than the total vaporization time of a droplet. It is shown that assumption (a) may lead to observable differences between the theoretical and experimental burning rates for low-energy fuels, that for practical purposes assumption (b) is probably always valid, and that approximation (c), which is most accurate for large values of the temperature at infinity, may lead to a 20% error in the computed value of the total vaporization time. The calculated duration of the initial unsteady period compares favorably with experiments on droplet ignition delay times.
Molecular Structure of Iodine Heptafluoride
Authors: LaVilla Robert E. , Bauer S. H.
Published: January 2005

Electron diffraction photographs taken in 1951 are here reanalyzed. All measurements and intensity estimates had been made visually; in the computations, allowance is made for the relative phase change of the scattering amplitudes between the iodine and fluorine atoms. Within a spread of 0.06 A, the I—F distances are approximately equal; the average value is 1.825±0.015 A. The molecular symmetry is almost D5h, in agreement with spectroscopic and crystal structure results. However, the electron diffraction patterns clearly indicate that the five fluorine atoms in the girdle are not coplanar and possibly are not equally spaced from the central iodine. The disorder reported in the crystalline state and the unusually broad NMR spectra of the liquid are readily accounted for by a sequential puckering about the polar axis and the possible out-of-phase extension from the axis of the girdle atoms. Revised values for the thermodynamic functions of the ideal gas are included.
Application of Symmetry Principles to the Rotation-Internal Torsion Levels of Molecules with Two Equivalent Methyl Groups
Authors: Myers Rollie J. , Wilson E. Bright
Published: January 2005

The set of coordinate transformations, corresponding to symmetry operations, which leave invariant the Hamiltonian operator for a molecule with two equivalent methyl groups, is obtained. These constitute a group which is a direct product of two simple groups, i.e., C3v×C3v. The possible species for the energy levels, their degeneracies, their statistical weights, and the selection rules are worked out by group theory techniques which use only the properties of the smaller groups. The higher symmetry and higher degeneracies given by approximate Hamiltonians are briefly discussed.
Multiple Ionization in Argon and Krypton by Electron Impact
Authors: Fox R. E.
Published: January 2005

The formation of multiply charged ions by electron impact in argon and krypton is studied with a mass spectrometer. The behavior of the ionization cross section as a function of electron energy is investigated for electron energies up to 600 ev. The ionization potentials in ev are determined to be as follows: Kr2+ 38.45±0.1,Kr3+ 75.6±0.5,Kr4+ 146.6±2,Kr5+ 217.5±10,Kr6+ 350±10,Ar2+ 43.4±0.3,Ar3+ 84.8±0.5,Ar4+ 150.0±5. The shapes of the ionization curves near threshold are studied and discussed in terms of the threshold law for ionization. The maximum cross sections for each multiply charged ion is determined relative to that of the singly charged ion and compared to data obtained by previous investigators.
Isotope Effects on Reaction Rates and the Reaction Coordinate
Authors: Wolfsberg Max
Published: January 2005

The high temperature limit of the reaction rate isotope effect is discussed. The Slater approach is compared in this respect to the transition state theory approach. There is no essential disagreement between the two approaches. The Slater assumption with respect to this limit for simple bond rupture represents a special case, however, and is not necessarily correct.
A One-Center Wave Function for the Methane Molecule
Authors: Saturno Antony F. , Parr Robert G.
Published: January 2005

Slater orbitals, centered on the carbon nucleus and having variable orbital exponents and principal quantum numbers, are used to construct electronic wave functions for the ground state of the methane molecule of the form Ψ=C1(s2s*2p6)+C2(s2s*2p5d)+C3(s2s*fp6)+C4(s2s*2p5f′)+C5(s2s*2p5g).Values for the five linear coefficients, the seven orbital exponents, and the seven principal quantum numbers are determined by the variational method. The total molecular energy obtained from a one-term wave function of this form is —39.50 a.u.; the five-term result is —39.80 a.u.; the experimental nonrelativistic energy is —40.51 a.u. Comparison with a similar calculation for the neon atom indicates that most of the residual error is in correlation energy, and it favors the high value for the heat of sublimation of carbon.
Casimir Coefficients and Minimum Entropy Production
Authors: Nettleton R. E.
Published: January 2005

The rate equations obeyed by scalar relaxation parameters in a liquid are extended to include inertial terms in the form of second-order time derivatives, and the relations containing these terms are then written formally as first-order equations by treating first-order time derivatives as additional parameters. The resulting equations are interpreted thermodynamically as phenomenological relations containing anti-symmetric Casimir coefficients, and this interpretation leads, with application of the Onsager-Casimir reciprocity theorem, to an additional set of phenomenological equations which reduces to those used in an earlier relaxation theory when inertial effects are neglected. In this way, earlier formulas for the bulk viscosity and high-frequency bulk modulus are recovered unchanged. It is also shown why Prigogine's minimum entropy production theorem should no longer hold when one considers inertial effects.
Valence Structure of the Higher Borides
Authors: Lipscomb William N. , Britton Doyle
Published: January 2005

An attempt is made to systematize the valence orbital structures of the boron frameworks in MB2, MB4, MB6, MB12, B12C3, and elementary boron.
On the Reciprocal Relations of Onsager
Authors: Coleman Bernard D. , Truesdell Clifford
Published: January 2005

Given any linear relation between forces and fluxes in irreversible thermodynamics, it is shown that redefinition of forces and fluxes by linear combination yields a relation with symmetric matrix. The rate of production of entropy is unchanged by the redefinition. Thus, unless ``forces'' and ``fluxes'' are defined by some property more specific than mere occurrence in the expression for production of entropy, there is no content in the statement that the matrix of phenomenological coefficients is or is not symmetric.
Quantum Yield for Energy Transfer by Resonance
Authors: Ore Aadne
Published: January 2005

The theoretical prediction of quantum yields for electric dipole-dipole energy transfer by resonance is discussed. The common approximation which neglects transfers from each donor to all but the nearest acceptor is extended so as to include transfers to the second-nearest acceptor and, in the limit of very high acceptor concentration, to the third and fourth as well. The total quantum yield and the fractional yields due to transfers to the individual categories of nearest acceptors are evaluated, and the merits of the various approximations are discussed quantitatively.
Absorption Spectra of Solid Xenon, Krypton, and Argon in the Vacuum Ultraviolet
Authors: Schnepp O. , Dressler K.
Published: January 2005

The absorption spectra of solid xenon, krypton and argon at 4.2°K have been investigated between 3500 and 1200 A. In the region between 1510 and 1200 A solid xenon has four absorption bands, three of which lie within less than 800 cm—1 of atomic transitions, all being shifted to lower energy in the solid. Solid krypton has two bands between 1250 and 1200 A which lie within 900 cm—1 of atomic transitions but are shifted to higher energy in the solid. No absorption was found in solid argon at wavelengths longer than 1200 A. The experimental results are interpreted and discussed on the basis of valence type interatomic interactions in the excited states. It is predicted that the fluorescence spectra of these solids would be displaced to lower energy by about 1 ev.
Theory of Hyperfine Interactions in Aromatic Radicals
Authors: McLachlan A. D. , Dearman H. H. , Lefebvre R.
Published: January 2005

The relation aH=Qρ between the ring proton isotropic hyperfine splitting aH and the unpaired spin density ρ on the carbon atom in an aromatic hydrocarbon radical is derived under even more general conditions than McConnell and Chesnut's.1 There are only three essential assumptions in the new theory: (a) that σ-π exchange interaction is small; (b) that an antisymmetrised product U (π) V (σ), which allows π-π and σ-σ, but not σ-π correlations, is a good first approximation to the ground-state electronic wave function; and (c) that U (π) is formed exclusively of π-orbital configurations, and V (σ) exclusively of σ ones. In the framework of our theory the unpaired spin density in the molecular plane arises entirely from σ-electron excitations. The general relation aN=tr(QNρ) holds for any nucleus N, including C13 and N14, which lies in the molecular plane. Here ρ is the π-electron spin-density matrix, and QN a hyperfine coupling matrix, whose elements depend on σ-π exchange integrals and excited σ triplet states. The diagonal elements of QN for C13 are estimated in a simple way to be +41 gauss for the same carbon atom and —14 gauss for each next neighbor, while experimental data fit the values +41 and —6.9 gauss.
Structure of Glass-Forming Halides. II. Liquid Zinc Chloride
Authors: Mackenzie J. D. , Murphy W. K.
Published: January 2005

Measurements of viscosity and electric conductivity in liquid zinc chloride indicate that at temperatures near the melting point, the melt is associated. The degree of association diminishes rapidly with increasing temperature as shown by the decreasing energies of activation for both viscous flow and conduction. Liquid ZnCl2 is thus not a normal fused salt such as CdCl2 or MgCl2. From the crystal structure and Raman absorption spectra, a mechanism of fusion and the structure of the melt are postulated. The ease of glass formation is discussed in terms of the liquid structure.
Heat Capacity of Uranium Tetrafluoride from 1.3° to 20°K and the Thermodynamic Functions to 300°K. Calorimeter for the Range 0.8° to 20°K
Authors: Burns John H. , Osborne Darrell W. , Westrum Edgar F.
Published: January 2005

The heat capacity of uranium tetrafluoride has been determined from 1.3° to 20°K in an isothermal calorimeter with an integral gas thermometer and vapor-pressure bulb for calibration of a carbon resistance thermometer. The enthalpy, entropy, and free-energy functions were evaluated from these data and previous measurements at higher temperatures. At 298.15°K, the values of S°, (H°–H0°)/T, and — (F°–H0°)/T are 36.25±0.04, 18.08±0.02, and 18.17±0.02 cal mole—1 deg—1 for uranium tetrafluoride. A Schottky-type anomaly occurs in the heat capacity at 6.4°K, presumably as a consequence of ligand-field splitting of the electronic energy levels.
Paramagnetic-Resonance Studies of Irradiated High-Density Polyethylene. I. Radical Species and the Effect of Environment on Their Behavior
Authors: Lawton Elliott J. , Balwit J. S. , Powell R. S.
Published: January 2005

Linear polyethylene (Marlex-50) was irradiated at different temperatures with 800-kv (peak) electrons. It was examined for paramagnetic resonance at +25° and —196°C to determine the radical species and their postirradiation behavior as well as that of the crystalline trapping medium. At low doses the spectrum is composed of two radical species which decay at different rates at room temperature. The predominant radical decays to zero in about five days; its six-line hyperfine structure is attributed to –CH2–CH–CH2–. The fast decay supports a previous suggestion that the polymer radicals are formed in pairs on adjacent chains. The other radical has a basic five-line spectrum with additional ``very fine'' structure. It lasts for months at room temperature. The behavior of the ``very fine'' structure on cooling to liquid-nitrogen (LN) temperature and the initial low concentration of the radical suggest its probable structure to be –CH2–H2C·|·CH2–CH2–. The relative numbers of each radical trapped at room temperature depend on the rigidity of the crystal and, therefore, on temperature during irradiation. The six-line radical pairs exist as several groups decaying at different rates at room temperature. The half-life of the fastest decaying group was 10 sec, that of the slowest, 25 hr. The fastest group comprises pairs in which the two radicals are formed nearly opposite each other on adjacent chains. They cause spin-spin line broadening in the time-zero LN spectrum. The decay rate of the radical pair is determined by the rigidity of the crystal. An apparent transition point for the crystal exists at —70°C, below which there is only a slight decay of the closest-spaced radicals. The total number of radicals produced and trapped by 40 megaroentgens at LN temperature was 6.2×1019/g which corresponded to a G(total radicals) = 3.0.
Sparking Potential and Molecular Structure of Unsaturated Hydrocarbon Gases
Authors: Crowe R. W. , Devins J. C.
Published: January 2005

In earlier experiments, we have shown that it is possible to relate sparking potentials of saturated hydrocarbon gases to certain molecular properties. From measurements of electric breakdown in a series of these gases, it has been found that the effective molecular cross section for electron scattering is proportional only to the number of carbon-hydrogen bonds in the molecule and is independent of their disposition. The lack of a contribution by the carbon-carbon bonds has been attributed to a shielding effect.

In the present paper, we describe and discuss the results of a similar investigation of breakdown in unsaturated hydrocarbon gases. It was found that, for a series of olefin gases, the cross section associated with the carbon-carbon double bond is greater than three times that of the carbon-hydrogen bond, while that of the carbon-carbon single bond is essentially zero as it was in the alkane series. An attempt is made to interpret this observation in terms of (1) a decrease in the shielding effect, and (2) the larger spatial configuration of the π-electron orbitals associated with the ethylenic linkage. Variations in the position of the double bond within the molecule has little or no effect upon its contribution to the total cross section.

Breakdown measurements in butadiene-1,3 and benzene indicate that conjugation results in an increase in the effective cross section of each double bond, as might be expected. Evidence of a small but measurable amount of double-bond character was also found in cyclopropane from sparking potential measurements. This is in agreement with the predictions of other investigators.
Molecular Structure Correlations
Authors: Bak Børge , Hansen-Nygaard Lise
Published: January 2005

The molecular structure of methane, ethane, ethylene, acetylene, ethyl fluoride, benzene, butadiene, allene, butatriene, propylene, cyclooctatetraene, methyl acetylene, diacetylene, methyl cyanide, methyl isocyanide, vinyl cyanide, carbon dioxide, formaldehyde, acetaldehyde, propynal, acrolein, formic acid, methyl formate, formamide, and acetyl cyanide (25 molecules) have been correlated by means of a set of empirical parameters, the physical meaning of which is discussed in part.
Emission Spectrum of the OH Radical in an Oxyacetylene Flame in the 1.5-μ Region
Authors: Rogge William H. , Yarger Frederick L. , Dickey Fred P.
Published: January 2005

The emission spectrum of the OH radical in the 1.5-μ region has been observed in an oxyacetylene flame. In order to eliminate the strong background which results from H2O emission in the same flame a double-beam method has been used. The double-beam method, which uses two flame sources, has been described. The spectrum of the 2–0, 3–1, and 4–2 vibration-rotation bands of OH which occur in this region are shown.
Radial Distribution Functions from the Born-Green Integral Equation
Authors: Broyles A. A.
Published: January 2005

Comparisons are made between solutions to the Born-Green integral equation and radial distribution functions obtained by the Monte Carlo method by Wood and Parker for the Lennard-Jones potential. It is observed that multiplying the particle separation distance in the Born-Green case by a constant factor improves the agreement for loops beyond the first.
Polarization of the First Two Electronic Transitions of Pyrene
Authors: Hochstrasser Robin M.
Published: January 2005

The polarization of the first two electronic transitions in the pyrene molecule have been determined by measuring the absorption spectra in polarized light of oriented single crystals containing pyrene. The lowest molecular level (3700 A) is assigned as 1B3u on the basis of the polarized absorption spectrum at room temperature of pyrene in phenanthrene. The second (3500 A) molecular level is assigned as 1B3u from the polarized spectrum of pyrene in dibenzyl. Although this result agrees with previous experimental evidence the assignments are at variance with theoretical predictions and thus suggest that a new model is necessary to predict the molecular levels of pericondensed hydrocarbons.
Multiple Vibrational Relaxation in Gaseous Dibromomethane
Authors: Meyer Norman J.
Published: January 2005

Ultrasonic-dispersion and absorption measurements have been made in gaseous dibromomethane at 296°K, and at pressures between 0.5 and 15 mm Hg. Wide-band transducers (solid dielectric microphone and driver) were used. A continuous selection of frequencies between 13 and 80 kc was used, generated as pulsed sine waves. Independent vibrational relaxation processes were found at 7.0 and 125 Mc/atm, with corresponding relaxation times of 3.02×10—8 and 0.146×10—8 sec. A third relaxation process was not within the experimental range of the apparatus, and occurs below 0.1 Mc/atm, with a relaxation time longer than 1.8×10—6 sec. Seven of the nine vibrational modes have sufficient population at 296°K to contribute to the various relaxation processes. Primarily based upon the specific heat contributions of each mode, the assignments of the various modes relaxing at the different relaxation times were made.
Microwave Spectrum of CFCl3
Authors: Long Maurice W. , Williams Quitman , Weatherly T. L.
Published: January 2005

A calculation has been made for the hyperfine spectrum of the J = 1→2 transition for symmetric-top molecules having three identical nuclei of spin 32. Measurements on the J = 1→2 through J = 6→7 transitions of CFCl3 are described and the results are used to determine the molecular structure, the quadrupole coupling constant with respect to the molecular symmetry axis, and the centrifugal distortion coefficients. The J = 1→2 transition of CHCl3 has been measured and the results are compared with those for CFCl3 and with previous work on CHCl3.
Heterogeneous Reactions Studied by Mass Spectrometry. I. Reaction of B2O3(s) with H2O(g)
Authors: Meschi David J. , Chupka William A. , Berkowitz Joseph
Published: January 2005

Knudsen effusion and mass-spectrometric techniques were employed in studying the gaseous species in thermodynamic equilibrium with condensed boric oxide and water vapor in the temperature range from 1060° to 1450°K. Water vapor was introduced into a Knudsen cell containing B2O3, and the vapor effusing from the cell was analyzed mass spectrometrically. The ions H2O+, HBO2+, H3BO3+, and (HBO2)3+ were observed. Of the various boron-containing species in equilibrium with the system, the one present in largest amounts was found to be HBO2. ΔH0° for the reaction 12H2O(g)+12B2O3(s)→HBO2(g)was calculated to be 47.6±2.0 kcal/mole. The data pertaining to the trimer (HBO2)3 are rather poor, but, in the temperature range covered, its concentration was less than 1% of that of the monomer HBO2, and at the highest temperature (1450°K) was approximately equal to the concentration of H3BO3. A crude calculation of the heat of formation of the trimer by means of the third law gives ΔH0° (f) ≈ — 540±10 kcal/mole.
Proton-Transfer Studies by Nuclear Magnetic Resonance. I. Diffusion Control in the Reaction of Ammonium Ion in Aqueous Acid
Authors: Emerson Merle T. , Grunwald Ernest , Kromhout Robert A.
Published: January 2005

Rate constants were determined by precise nuclear-magnetic-resonance techniques for the reactions: NH4++H2O−→ lim k4NH3+H3O+;NH3+H3O+−→ lim k-4NH4++H2O;and N lim −H4++NH3−→ lim k6N lim −H3+NH4+in aqueous acid at 25°C. For 0.25–3.00M NH4Cl, k—4 and k6 were 4.3×1010 sec—1M—1 and 1.17×109 sec—1M—1 respectively, independent of NH4Cl concentration. Both rate constants increase on addition of KCl. The rate constant, k4, was 24.6 sec—1 at zero ionic strength and decreased sharply with NH4Cl concentration. The values of KA needed in the kinetic analysis were measured also. The reaction of NH4+ with H2O was investigated also in 50–60 wt % H2SO4-H2O mixtures, where the half-life for isotopic exchange was between two and 20 minutes. The data allowed us to estimate the rate constant (1/τD+1/τR) for the rupture of the H3N···HOH hydrogen bond, by diffusion (D) or rotation (R). The value obtained was 51×1010 sec—1. Using Einstein's theory of Brownian motion, the value of 1/τD was estimated to be 34×1010 sec—1, leaving 17×1010 sec—1 for 1/τR, of which 12×1010 and 5×1010 sec—1 are the contributions due to the rotation of H2O and NH3, respectively. The probability that NH3 rotates during an encounter is therefore fairly small.

The order of magnitude of k—4 and k6 suggests that these reactions are diffusion controlled. Upon applying the Debye-Smoluchowski theory to calculate the frequency of encounters, we found that k—4 is consistent with reaction occurring whenever H3O+ and NH3 are next-nearest neighbors. The steric factor for this reaction appears to be unity. Since the data in strong acid suggest that rotation of a molecule during an encounter is improbable, we conclude that the reactants are oriented during their approach so that the unshared electrons of the NH3 face an acidic hydrogen. To interpret k6, we assume a mechanism in which NH3 and NH4+ become next-nearest neighbors by simple diffusion; the jump to a nearest-neighbor site then requires a somewhat higher activation energy than simple diffusion because NH3 must displace a tightly bonded water molecule. The reaction with rate constant k4 is activation controlled. The negative salt effect on k4 suggests diffusion of charge in the transition state.
Emission Spectra of Erbium in the Scheelite Structure
Authors: Van Uitert L. G. , Soden R. R.
Published: January 2005

Erbium exhibits luminescent emission from excited states at 15 300, 18 400, and 24 500 cm—1 in calcium tungstate at room temperature and at 77°K. At room temperature, emission from thermally excited states at 18 830, 19 080, and 19 200 cm—1 is also prominent.

At high erbium concentrations, the above spectra are essentially quenched at room temperature and new spectral lines which appear to originate from electronic levels just below the 18 400- and 24 500-cm—1 states are seen. However, at 77°K, emission from the 15 300, 18 400- and 24 500-cm—1 states is again strong and emission associated with levels just below these is no longer observed.

There is no evidence of exchange coupling preferentially quenching the higher-energy emission states as in the cases of Tb3+ and Eu3+. This and the temperature dependencies observed suggest that thermal coupling to the lattice is the main factor responsible for quenching the emission of Na0.5 Er0.5 WO4.