bluuebunny/crossref_metadata_2025 huggingface dataset:
Monte Carlo Equation of State of Molecules Interacting with the Lennard-Jones Potential. I. A Supercritical Isotherm at about Twice the Critical Temperature
Authors: Wood W. W. , Parker F. R.
Published: January 2005

Values obtained by Monte Carlo calculations are reported for the compressibility factor, excess internal energy, excess constant-volume heat capacity, and the radial distribution function of Lennard-Jones (12,6) molecules at the reduced temperature kT/ε*=2.74, and at thirteen volumes between v/v*=0.75 and 7.5. (v is the molar volume; v*=2—½N0r*3; N0 is Avogadro's number; ε* is the depth, and r* the radius of the Lennard-Jones potential well.) The results are compared with the experimental observations of Michels (∼150–2000 atmos) and Bridgman (∼2000–15 000 atmos) on argon at 55°C, using Michels' second virial coefficient values for the potential parameters. Close agreement with Michels is found, but significant disagreement with Bridgman. The Monte Carlo calculations display the fluid-solid transition; the transition pressure and the volume and enthalpy increments are not precisely determined. The Lennard-Jones-Devonshire cell theory gives results which disagree throughout the fluid phase, but agree on the solid branch of the isotherm. Limited comparisons with the Kirkwood-Born-Green results indicate that the superposition approximation yields useful results at least up to v/v*=2.5.
Structure and Molecular Interaction in HX–DX Mixed Crystals
Authors: Hornig D. F. , Hiebert G. L.
Published: January 2005

The infrared spectra of mixed HCl–DCl and HBr–DBr crystals have been studied at 66°K in their lowest temperature crystalline phase over the entire composition range. It is demonstrated quantitatively that the observed spectra are those of linear zigzag chains in both cases. The magnitude of the interaction constant between displacements of neighboring molecules suggests that in the crystal ∂μ/∂r is about 2d/A for both molecules, more than twice the value in the free molecule.
Measurement of Chapman-Jouguet Pressure for Explosives
Authors: Deal W. E.
Published: January 2005

The Chapman-Jouguet pressures of RDX, TNT, 64/36 Composition B, and 77/23 Cyclotol have been measured by determining initial free-surface velocity as a function of thickness for 24ST aluminum plates in contact with the detonating explosive. An optical technique is described for the measurement of the velocities. The pressures determined for RDX, TNT, 64/36 Composition B, and 77/23 Cyclotol are 338, 189, 292, and 313 kilobars, respectively.
Higher Order Rotation-Vibration Energies of Polyatomic Molecules. II
Authors: Amat Gilbert , Goldsmith Mark , Nielsen Harald H.
Published: January 2005

The calculations of third- and fourth-order rotation-vibration energies of a general polyatomic molecule are herein continued with a discussion of the zero-, first-, second-, and third-order transformed Hamiltonians.
Some Photoelectric Properties of Chlorophyll
Authors: Nelson R. C.
Published: January 2005

Both chlorophyll a and methyl chlorophyllide a have been found to be photoconductive in films deposited from solvents. The photoconductivity of methyl chlorophyllide a resembles that of some cyanine dyes in having two time constants for rise and decay, one less than a second, and the other of the order of several minutes. The action spectrum of the ``fast'' photoconductivity is similar to the absorption spectrum of the pigment, the red peak falling at 6740 A. Both pigments sensitize photoconductivity in cadmium sulfide films, and the contact potential difference at the interface is of the correct sign to permit electron transfer from dye to crystal. These properties give some support to Katz's hypothesis regarding the primary process in photosynthesis.
Microwave Spectra of Molecules Exhibiting Internal Rotation. I. Propylene
Authors: Lide David R. , Mann D. E.
Published: January 2005

The microwave spectrum of propylene, CH3CH:CH2, has been investigated in the region 17–36 kmc. Measurements have been made on the normal isotopic species and on the H3CC13H:CH2 species. Most of the observed lines are split slightly as a result of internal rotation. These splittings have been satisfactorily analyzed by the methods of Hecht and Dennison, giving an internal potential barrier of 692.4±6 cm—1 or 1978±17 cal/mole. Principal moments of inertia (in units of amu A2) are 10.973, 54.312, and 62.175 for H3CCH:CH2 and 11.160, 54.318, and 62.382 for H3CC13H:CH2. The electric dipole moment has a magnitude of 0.364 D and makes an angle of 8° with the a principal axis. With reasonable assumptions concerning the location of the hydrogen atoms the remaining structural parameters are: rCC=1.488 A, rC:C=1.353 A, ≤ CCC=124°45′.
Infrared and Raman Spectra of Fluorinated Ethanes. IX. 1,1,1-Trifluoro-2-chloro-2-bromoethane
Authors: Theimer Rose , Nielsen J. Rud
Published: January 2005

The infrared absorption spectrum of gaseous 1,1,1-trifluoro-2-chloro-2-bromoethane has been obtained with a 1-m cell and a Perkin-Elmer double-pass spectrometer equipped with CsBr, NaCl, and LiF prisms. The Raman spectrum of the liquid phase has been photographed with a 3-prism glass spectrograph of reciprocal linear dispersion 15 A/mm at 4358 A. The 18 vibrational fundamentals have been assigned as follows: 72, 160, 202, 229, 310, 364, 520, 552, 665, 718, 814, 863, 1133, 1179, 1198, 1273, 1313, and 3017 cm—1. The four lowest are for the liquid state, the others for the gas. The spectra have been interpreted in detail. Thermodynamic functions have been calculated.
Magnetic Susceptibilities of Some Pu+4 Compounds
Authors: Lewis W. Burton , Elliott Norman
Published: January 2005

The magnetic susceptibilities of Pu(SO4)2·4H2O, Rb4Pu(SO4)4·2H2O, Pu(C2O4)2·6H2O, [(CH3)4N]2-PuCl6, and PuF4 have been measured over the temperature range 77–334°K. The large departures from the Curie-Weiss law observed in these salts are discussed in terms of the crystalline field symmetry.
Heat Capacity of Terbium from 15 to 350°K
Authors: Jennings L. D. , Stanton R. M. , Spedding F. H.
Published: January 2005

The heat capacity of terbium has been measured in the temperature range 15 to 350°K. A lambda anomaly has been observed with the peak at 227.7°K. There is, in addition, an anomalous region near 220°K. The heat capacity in this region depends on the thermal history of the sample. The value of the entropy at 273.16°K is 17.50 cal/ (g atom-deg) in agreement with the value predicted on the assumption that at room temperature the 4f electrons have the same configuration as in the free tripositive ion.
Note on the Canonical Ensemble for the Ideal Einstein-Bose Gas
Authors: Ford J. , Berlin T. H.
Published: January 2005

It is shown that the canonical ensemble for the ideal Einstein-Bose gas correctly describes the condensed phase when fully treated by the method of steepest descent.
FE Theory Including an Elastic σ Skeleton. II. Changes of Molecule Dimensions due to Optical Excitation
Authors: Labhart Heinrich
Published: January 2005

A simple theory is given which relates the changes in molecular dimension due to optical excitation to the changes in kinetic energy and interaction energy of π electrons. Results for polyenes, polymethines, and for benzene are given. The latter agree quite satisfactorily with experimental determinations.
Random Flight Model in the Theory of the Second Virial Coefficient of Polymer Solutions
Authors: Albrecht Andreas C.
Published: January 2005

The theory of the second virial coefficient, A2(M2,T), for dilute polymer solutions is investigated from the point of view, first developed by Zimm, of the Ursell-Mayer-like development in terms which successively represent increasing numbers of contacts between molecular subunits of flexible chain molecules. The methods used by Fixman in treating excluded volume problems in the random flight model are here employed. Evaluation is carried out to the triple contact approximation. A formal analysis of all higher terms is presented and the contribution of one class of terms is evaluated exactly. The remaining terms appear to be inaccessible to numerical evaluation by ordinary methods so that a rigorous discussion of the asymptotic behavior of A2 is precluded. Semiquantitative arguments, however, indicate favorable agreement with experiment, provided intramolecular excluded volume effects are considered.
Lattice Constants of Separated Lithium Isotopes
Authors: Covington E. J. , Montgomery D. J.
Published: January 2005

The lattice constant for highly enriched (>99%) samples of Li6 and Li7 metal was determined at 20°C by x-ray diffraction methods. The constant for Li6 was found to be fractionally larger than that for Li7 by about 4×10—4. These results are not inconsistent with a rough theoretical estimate for the fractional difference of 3×10—4. It is likely that the constant for Li7 does not differ from that for natural lithium by more than 1×10—4. The fact that the lighter isotope has the larger lattice constant constitutes experimental evidence for the reality of zero-point energy.
Diffusion Coefficients of the Systems Xe–Xe and A—Xe
Authors: Amdur I. , Schatzki T. F.
Published: January 2005

The diffusion of radioargon, A37, and of radioxenon, Xe131m, through inert xenon was measured at —78, 0, 57, and 105°C. The apparatus, a Loschmidt cell in which saturation ionization currents were used as a measure of tracer concentrations, yielded diffusion coefficients which are estimated to have an accuracy of about one percent.

The intermolecular potentials of Xe–Xe, derived from the present results, agree with those obtained from thermal conductivity data in the same temperature range, but do not agree with potentials derived from second virial coefficients and crystal data. Nor do they agree with potentials derived from viscosity and thermal conductivity data at higher temperatures. It is shown that this lack of agreement is due to the inadequacy of the potential form. The potential well for the rare gases should be narrower than that given by the Lennard-Jones 12–6 potential.
Nuclear Quadrupole Coupling in the Alkali Chloroiodides. I. Chlorine Resonances
Authors: Cornwell C. D. , Yamasaki R. S.
Published: January 2005

Chlorine resonance frequencies are reported for the following at 298°, 194°, and 77°K: CsICl2, KICl2, KICl2·H2O, CsICl4, RbICl4, KICl4, KICl4·H2O, NaICl4·2H2O. Variations due to crystal effects in these substances amount in most cases to less than a megacycle. The average frequencies at room temperature, 19.2 and 22.3 Mc/sec, are taken as representative of ICl2— and ICl4— ions, respectively, in a crystalline environment. These values are in the neighborhood of half those found for ICl, and suggest a bonding scheme in which the electron distribution is shifted outward toward the chlorine atoms to such an extent that the electron population of iodine orbitals is not so large as to require the use of d orbitals. The conclusion is that d orbitals are rather less important to bonding in the polyhalides than has generally been supposed. The problem of arriving at a practical and meaningful separation of crystal and chemical effects is considered qualitatively, and marked crystal effects evident in the spectra of KICl4·H2O and NaICl4·2H2O are briefly discussed.
Cl35 Pure Quadrupole Resonance Studies of Relaxation Times in Solid Solutions of p-Dichlorobenzene
Authors: Woessner D. E. , Gutowsky H. S.
Published: January 2005

Transient methods have been used to measure the Cl35 nuclear relaxation times at room temperature in solid solutions of p-dichlorobenzene and p-dibromobenzene. The spin-lattice relaxation time T1 and the phase memory time T2 were found to be virtually independent of sample composition. However, the inverse line width T2* decreases very sharply from 3.1×10—4 sec in pure p-dichlorobenzene to 0.15×10—4 sec in a sample with 20 mole percent p-dibromobenzene. Thus, the main effect of the solute molecules is to broaden the absorption line by producing a distribution in the electric field gradients at the chlorine nuclei. Mechanisms for the T1 and T2 results are discussed.
Entropy, Heat Capacity, and Heats of Transition of 1,2,4-Trimethylbenzene
Authors: Putnam William E. , Kilpatrick John E.
Published: January 2005

The heat capacity and the heats and temperatures of fusion of 1,2,4-trimethylbenzene have been determined experimentally. This substance exhibits two melting points: at 229.33±0.03°K and at about 224.2°K. The only solid phase having reproducible heat capacities was found to be the one having the highest melting point. The entropy of the ideal gas at 25°C and one atmos pressure has been found to be 99.59±0.15 cal/deg mole.
Adsorption and Diffusion of Hydrogen on Nickel
Authors: Wortman R. , Gomer R. , Lundy R.
Published: January 2005

The surface diffusion and adsorption of hydrogen on Ni field emitters has been investigated by a technique previously used for similar studies of H and O diffusion on W. It was found that diffusion occurs with an activation energy of 7±1 kcal in the chemisorbed layer, without the precipitation boundaries observed on W. This is believed to result from the inherent homogeneity of f.c.c. substrates, on which most adsorption sites seem equivalent. This is supported by the marked lack of emission anisotropy of hydrogen-covered Ni field emitters.

A field dependent transformation in the adsorbed film was found between 2° and 4°K and interpreted as a shift in the equilibrium between adsorbed H2 molecules and the terminal fraction of adsorbed H atoms. The implications of this result for the mechanism of H2–D2 exchange are discussed.

The activation energy of desorption at very low coverage is determined to be 46±4 kcal from the temperature dependence of desorption rates.
Computation of Rigid Asymmetric Rotator Constants from Energy Moments
Authors: Brown L. Carlton , Parker Paul M.
Published: January 2005

Expressions are developed which relate the rotational constants of the rigid asymmetric rotator to experimental data through moments of the energy levels. The procedure in many cases permits the computation of rotational constants with much less effort than is usually met in either numerical approximation to roots of secular equations or perturbation methods.
Stretching Vibrations in Condensed Systems : Especially Bonds Containing Hydrogen
Authors: Benson A. M. , Drickamer H. G.
Published: January 2005

A study has been made of the stretching vibrations of a variety of bonds, mostly containing hydrogen, in condensed systems. In particular, measurements have been made of vapor-liquid shifts and of the shifts with pressure to 10 000 atmospheres. From the results, an attempt has been made to estimate the relative importance of dispersion, induction, orientation, and repulsion (overlap) energies. The importance of the redistribution of electrons in a molecule due to the varying electronegativity of its constituent parts is particularly noted.
Mass Spectroscopic Determination of Photoionization Products
Authors: Herzog Richard F. , Marmo Frederick F.
Published: January 2005

A radio-frequency mass spectrometer of the Bennett type has been utilized to measure the mass of ions formed by photoionization of several gases by the ultraviolet radiation of a hydrogen discharge. Investigations were performed up to 11.4 electron volts, the LiF cutoff. The mass spectra were found to be very simple and usually consisted of only one peak representing the mass of the whole molecule. This has been found to be true for acetone, butadiene, butene, carbon disulfide, methyl-ethyl ketone, nitric oxide, propylene, and toluene. Only in the case of butane, ethyl acetate, and isopropyl alcohol, fragment ions have been found. Some of them are even more intense than the parent ions. Undesirable ``secondary spectra,'' reported by Lossing and Tanaka, can be avoided by grounding of the lithium fluoride window.
Infrared Spectra of Molecules with Hydrogen Bonds
Authors: Bratož S. , Hadži D.
Published: January 2005

The unusual features of the infrared spectra of molecules with hydrogen bonds are discussed. It is shown that the broad hydrogen stretching bands associated with strong hydrogen bonds are not single bands, but groups of bands which are very sensitive to intermolecular influences. This is due to the anharmonicity of some parts of the (effective) molecular potential energy surface. This surface occasionally has two minima which implies typical double minimum phenomena. Variations in the intensity of the hydrogen stretching bands in going from the nonbonded to the bonded molecules is discussed and an explanation attributing this variation to the charge transfer associated with the hydrogen bond formation is offered.
Superiority of the Poeschl-Teller Potential to that of Morse for Diatomic Molecules
Authors: Beckel Charles L.
Published: January 2005

The accuracies of the Poeschl-Teller and Morse functions as vibrational potential energies are compared for the ground electronic states of sixty-seven diatomic molecules. For each molecule both functions are fitted to the experimental values of Y10, Y20, and Y01. The comparison of the functions is then made through examination of —Y11. For fifty-four of the molecules the P.T. function is more accurate than the Morse function. The superiority of the P.T. function seems more pronounced for ionized and for predominantly-ionic molecules than for normal covalent molecules. Parameters of Poeschl-Teller curves fitted to empirical values of Y10, Y20, Y01 and Y11 are tabulated for the sixty-seven molecules.
Series Expansion of Distribution Functions in Multicomponent Fluid Systems
Authors: Meeron Emmanuel
Published: January 2005

The equations of Kirkwood and Salzburg for distribution functions are generalized to multicomponent systems. The generalized equations serve to derive a recurrence relation between the coefficients of powers of particle number densities in a Maclaurin expansion of the distribution functions. This recurrence relation is then used to derive the general term in the expansion of the distribution functions in terms of modified irreducible integrals in multicomponent systems, which includes the original one-component expansion of Mayer and Montroll as a special case.

The corresponding expansion of the potentials of average force is derived. The use of the new expansion is illustrated by a relatively simple derivation of the Fuchs expansion of the grand potential in multicomponent systems.

Possible applications to ionic solutions, impurities in solids and x-ray diffraction in solutions of several solutes are briefly discussed.

Some new formulas in the theory of cumulants (Thiele semi-invariants) are presented.
Structure of Gaseous Chloropicrin as Determined by Electron Diffraction
Authors: Barss W. M.
Published: January 2005

The structure of chloropicrin was studied as a step in the investigation of several families of methane derivatives to determine variations in carbon bond angles and bond lengths in compounds having approximately tetrahedral carbon bonds. The results obtained showed the carbon-nitrogen bond to be longer in chloropicrin than in either nitromethane or tetranitromethane.

The electron diffraction patterns were obtained in a camera in which high background intensity gradients were corrected by means of a rotating shutter intercepting the scattered electrons. Intensity curves derived from microphotometer traces were subjected to Fourier analysis to obtain a radial distribution function. Intensity curves were synthesized for a series of molecular models to make a refined determination of the molecular parameters for chloropicrin.
Heat Capacity of Calcium from 1.8 to 4.2°K
Authors: Griffel Maurice , Vest R. W. , Smith J. F.
Published: January 2005

The heat capacity of high-purity calcium has been measured over the temperature interval from 1.8 to 4.2°K. The electronic contribution is linear in T and the coefficient γ is 3.08±0.01 millijoules/(gram-atom) deg2 corresponding to a density of states at the Fermi level of 0.653 momentum state per electron volt per atom. A Debye temperature of 239±2°K was obtained.

For purposes of testing the calorimeter, the heat capacity of copper was determined. In agreement with other recent measurements, the value obtained for γ is 0.691±0.006 millijoule/(gram-atom) deg2 and θD is 342±2°K.
Drude-Model Calculation of Dispersion Forces. I. General Theory
Authors: Bade W. L.
Published: January 2005

The dipole-dipole part of the London-van der Waals interaction energy of a system of N molecules is calculated in the general order of perturbation, using a model which represents each molecule as an isotropic harmonic dipole-oscillator. The calculation assumes that the characteristic dispersion frequencies of the molecules are all equal. The advantages and limitations of the oscillator model are discussed.
Infrared Spectra and Vibrational Assignment of Monomeric Formic Acid
Authors: Millikan Roger C. , Pitzer Kenneth S.
Published: January 2005

The infrared spectra of monomeric HCOOH, HCOOD, DCOOH, and DCOOD have been studied in the gaseous phase with emphasis on the 800 to 450 cm—1 region. New absorption bands were found for HCOOD at 541 and 512 cm—1, and for DCOOD at 538 and 489 cm—1. These bands are attributed to the a′ OCO bending and to the a″ O–D torsion motions, respectively. In HCOOH and DCOOH the bands arising from the corresponding vibrations apparently coincide at approximately 630 cm—1. An assignment of fundamentals for the four isotopic species has been derived. Excellent agreement is obtained with the Teller-Redlich product rule. Also the calculated entropy agrees with the experimental value from the third law of thermodynamics.
Magnetic Analysis of Alloys by Electron Diffraction
Authors: Yamaguchi S.
Published: January 2005

Electron diffraction patterns obtained from ferromagnetic substances (Cu–Ni and stainless steel) are influenced by the magnetic fields of the substances. The results obtained are of use for magnetochemical analysis of ferromagnetic alloys.
Thermoluminescence and Coloration of Lithium Fluoride Produced by Alpha Particles, Electrons, Gamma Rays, and Neutrons
Authors: Morehead Frederick F. , Daniels Farrington
Published: January 2005

The coloration and thermoluminescence produced in LiF by 2 Mev alpha particles, by 2 Mev electrons, by 1 Mev gamma rays from Co60, and by thermal neutrons are described. The energy initially required to produce an F center varies. It is about 700 ev for alpha, 140 ev for beta, 65 ev for gamma rays, and 65 ev for thermal neutrons.

The amount of thermoluminescence light produced and the number of thermoluminescence peaks increased with the exposure to each of these radiations. The larger the radiation dosage, the greater is the fraction of thermoluminescence emitted at the higher temperatures. All of the thermoluminescence is related to the emptying of F centers, but only one photon is emitted as visible thermoluminescence for every 104 electrons removed from F centers.

The optical and thermal decolorizations are discussed.
Studies of Color Centers in Polycrystalline Compressed Pellets of Alkali Halides
Authors: Hersh Herbert N.
Published: January 2005

Compressed and uncompressed powders of several alkali halides (KCl, KBr, KI, CsI) have been colored by x-rays and by chemical addition and their spectra measured. The x-ray darkenability of pellets is greater than of single crystals, with respect to F, V2, and V3 bands. The F centers are relatively unstable optically; their bleaching is rapid and complete and does not give rise to appreciable K, M, R and N bands, in contrast to F centers in single crystals. After F irradiation the pellets still exhibit intense, well-resolved V2 and V3 bands and, upon dissolving in water, liberate free halogen. The relative intensity of the F and V bands may be controlled by varying the x-ray or F-light exposure. KI pellets may be additively colored at room temperature with iodine. In general V bands may be produced by adsorbing halogen onto the crystalline surface and are more stable in the compressed pellets than the unconfined powder. By virtue of their different physical makeup from a single crystal the pellets exhibit the above color-center phenomena to a larger degree than single crystals.
Kinetics and Equilibria of Complex Reactions
Authors: Hollingsworth C. A.
Published: January 2005

The kinetics of complex reversible reactions are treated by a method that clarifies the relationship between the rate laws and the thermodynamic condition for equilibrium. It is shown that this relationship takes on simple forms only under very special conditions. Some of the equations obtained appear to be useful for the treatment of certain types of complex rate processes. The theory of steady-state diffusion in the presence of an external field is treated briefly.
Neighbor Interactions and Symmetric Properties of Polyelectrolytes
Authors: Lifson Shenior , Kaufman Bruria , Lifson Hanna
Published: January 2005

The grand partition function of polyelectrolyte molecules, considered as linear Ising chains, is studied with respect to certain symmetry properties of these systems. The degree of ionization and the buffering capacity are shown to possess a symmetry with respect to the point of half neutralization. Equations for the pH, the degree of ionization, and the buffering capacity are derived explicitly for a model in which only the interactions between first- and second-neighbors are taken into account. The results are compared with those of the theory of first-neighbor interactions, and graphs of titration and buffering-capacity curves are given. The properties of the maxima and minima occurring in the buffering-capacity curves are discussed. It is found that the form of buffering-capacity curve provides information on the order of non-negligible interactions.
Infrared Intensities and Bond Moments in CO12O18
Authors: Eggers D. F. , Arends C. B.
Published: January 2005

By using isotopically enriched samples, the three fundamentals and one overtone of CO16O18 have been located in the gas phase. Positions disagree with predictions of a simplified theory by somewhat more than experimental error, especially for the Fermi-resonant pair ν1 and 2ν20. Intensities were also measured on the Fermi-resonant pair, and the bond moment derivative thus calculated, 5.79×10—10 esu, is in excellent agreement with that determined from the ν3 vibration of the normal isotopic molecule. This result lends support to the simple bond-moment hypothesis for stretching vibrations. Intensities were also measured on the solid phases of CO16O18 and of N2O; the results are in poor agreement with measurements on the gas phase, though the frequencies are only slightly shifted.
General Theory of Bimolecular Reaction Rates in Solids and Liquids
Authors: Waite T. R.
Published: January 2005

An argument is presented to show that the theory of kinetics of diffusion limited reactions developed previously may be generalized to a theory of bimolecular reaction rates in condensed phases. The rate at which particles arrive at a separation suitable for reaction is given by differential equations describing the random walks of the particles. The probability of reaction of particles separated by this collision diameter (i.e., near neighbors in the condensed system) is given by a steric and activation energy factor. The resulting boundary value problem is solved in detail. Explicit expressions for the reaction rates are presented. The reaction follows second-order kinetics except that the most general rate ``constant'' is time dependent. Reaction rates are discussed in terms of the diffusion parameters and forces between the reactant particles. Physical interpretations of the rate constant are suggested. Reaction rates in liquid solvents are related to the viscosity of the solvent phase. An effective capture radius is derived for particles with long-range forces.
Theory of Isotropic Hyperfine Interactions in π-Electron Radicals
Authors: McConnell Harden M. , Chesnut Donald B.
Published: January 2005

Indirect proton hyperfine interactions in π-electron radicals are first discussed in terms of a hypothetical CH fragment which holds one unpaired π electron and two σ-CH bonding electrons. Molecular orbital theory and valence bond theory yield almost identical results for the unpaired electron density at the proton due to exchange coupling between the π electron and the σ electrons. The unrestricted Hartree-Fock approximation leads to qualitatively similar results. The unpaired electron spin density at the proton tends to be antiparallel to the average spin of the π electron, and this leads to a negative proton hyperfine coupling constant.

The theory of indirect proton hyperfine interaction in the CH fragment is generalized to the case of polyatomic π-electron radical systems; e.g., large planar aromatic radicals. In making this generalization there is introduced an unpaired π-electron spin density operator, ρN, where N refers to carbon atom N. Expectation values of the spin density operator ρN are called ``spin densities,'' ρN, and can be positive or negative. In the simple one-electron molecular orbital approximation a π-electron radical always has a positive or zero spin density at carbon atom N, 0≤ρN≤1. In certain π-electron radical systems; e.g., odd-alternate hydrocarbon radicals, the spin densities at certain (unstarred) carbon atoms are negative when the effects of π—π configuration interaction are included in the π-electron wave function.

The previously proposed linear relation between the hyperfine splitting due to proton N, aN, and the unpaired spin density on carbon atom N, ρN,aN=QρNis derived under very general conditions. Two basic approximations are necessary in the derivation of this linear relation. First, it is necessary that σ—π exchange interaction can be treated as a first-order perturbation in π-electron systems. Second, it is necessary that the energy of the triplet antibonding state of the C–H bond be much larger than the excitation energies of certain doublet and quartet states of the π electrons. This derivation of the above linear relation makes no restrictive assumptions regarding the degree of π—π or σ—σ configuration interaction. The validity of the above approximations is discussed and illustrated by highly simplified calculations of the proton hyperfine splittings in the allyl radical, assuming the π—π configuration interaction—and hence the negative spin density on the central carbon atom—to be small.

Isotropic hyperfine interactions in molecules in liquid solution can also arise from spin-orbital interaction effects, and it is shown that these effects are negligible for proton hyperfine interactions in aromatic radicals.
Irreversible Electrochemical Processes of Membranes
Authors: Kobatake Yonosuke
Published: January 2005

Theoretical equations of membrane potentials and of the permeation rates of ions through membranes are derived from the entropy production in the membranes. The entropy production is calculated by means of the irreversible thermodynamics of continuous systems based on hydrodynamics. The calculation was carried out under the assumptions that the membrane has a porous mosaic structure and that the ionic concentration in the membrane capillaries ought to be determined by means of the Poisson-Boltzmann equation, and also that there is no pressure difference between two sides of the membrane. The equation of the membrane potential here obtained agrees with that derived from the Eyring theory of rate processes, but the former is more rigorous than the latter. The experimental data were found to be in good agreement with the theory. Furthermore, a new equation for the permeability of ions was derived by the same procedure.
Application of the Method of Deformed Atoms in Molecules to the Li2 Molecule
Authors: Arai Tadashi , Sakamoto Michiko
Published: January 2005

The method of deformed atoms in molecules, proposed previously to remedy deficiencies in the method of Moffitt, is employed to calculate energies of the ground state 1Σg+ and the lower excited states 3Σu+, 1Σu+, and 1IIu of the Li2 molecule. As basis for the molecular calculation, modified atomic functions are introduced to take deformation of atoms in molecules into account. These modified functions are constructed from atomic eigenfunctions in a manner which fully preserves correlation between electrons. Exact atomic energies are used to calculate the atomic energy parts of the matrix elements of the molecular calculation, while the energy defects due to deformation of atoms are determined by using approximate functions.

The modified atomic functions are made up so that their charge distributions are well described by the use of Slater orbitals with equal orbital exponents for all atomic states. Interatomic interaction operators, overlap integrals, and energy defects due to deformation of atoms are calculated using Slater orbitals. For the 1s)22s)2p) 3P and 1P states of the Li— ion, the exchange correction due to binding a free electron into the 2p orbital is considered. The energy defects of Slater orbitals from Hartree-Fock orbitals are found to have small effect on the dissociation energy of the ground state.

The calculations are performed for three sets of values for the orbital exponents. The dissociation energy obtained for one set of values is 0.96 ev, in good agreement with the observed value of 1.05 ev. The excitation energies obtained of 1.63 ev for 3Σu+—1Σg+, 2.05 ev for 1Σu+—1Σg+ and 2.59 ev for 1IIu—1Σg+ also agree reasonably well with the corresponding observed values of (1.35 ev), 1.76 ev, and 2.54 ev.

The calculation is discussed and compared with the orbital approach and Moffitt's method. Conclusions are stated regarding the nature of bonds and orbital exponents in Li2.
Structure of Sodium Metaphosphate Glass
Authors: Brady George W.
Published: January 2005

The x-ray diffraction pattern of sodium metaphosphate glass (formula NaPO3) has been determined. The radial distribution function determined from the diffraction pattern indicates that the structure consists of long chains of PO4 tetrahedra crosslinked to other chains by O–Na–O— bonds. This model agrees with the one advanced by other workers who applied high polymer techniques to the study of metaphosphates.
Spin Densities in the Perinaphthenyl Free Radical
Authors: McConnell Harden M. , Dearman Henry H.
Published: January 2005

Valence bond theory is used to calculate π-electron spin densities (ρi) on carbon atoms in the perinaphthenyl free radical,[Complex chemical formula]The results are ρ1=—0.176, ρ2=+0.321, ρ3=—0.220, ρ13=+0.262. The theoretical spin densities ρ1 and ρ2 are compared with the ``experimental'' values |ρ1|=0.098, |ρ2|=0.325 which are obtained from the equation ai=Qρi and the absolute isotropic proton hyperfine splittings (|a1|=2.2, |a2|=7.3 gauss) which have been observed in the electron magnetic resonance of the perinaphthenyl free radical by Sogo, Nakazaki, and Calvin. Valence bond theory thus yields calculated spin densities in this odd-alternate radical which are in reasonably good agreement with the ``experimental'' densities. Molecular-orbital theory without configuration interaction predicts only positive spin densities and is therefore inadequate to describe experimental densities in the perinaphthenyl radical or in any other substance with large negative spin densities.
Electron Diffraction Study on the Rotational Isomerism in n-Propyl Chloride
Authors: Morino Yonezo , Kuchitsu Kôzo
Published: January 2005

The molecular structure and the rotational isomerism of n-propyl chloride were investigated by means of the sector-microphotometer method of electron diffraction. The following structural parameters were obtained: C–Cl=1.775±0.02 A, C–C=1.535±0.02 A, and ∠C–C–Cl=111°±2°. It was confirmed that there are two isomers in the vapor phase; one is the trans-form, and the other is the gauche-form. From the analysis of the scattering intensity of the small-angle region (q=5∼15), the angle of ∠C–C–C, the azimuthal angle of the gauche-form, and the fraction of the trans-form were found to be 109.5°±2.5°, 59°±5°, and 19±5%, respectively. It was also found through the calculation of the partition functions that the gauche-form is only a few hundred calories/mole more stable than the trans-form, in fairly good agreement with the spectroscopic results. The procedure used in the analysis of the small-angle region is described in detail.
Molecular Structure and Internal Rotation of Hexachloroethane, Hexachlorodisilane, and Trichloromethyl-Trichlorosilane
Authors: Morino Yonezo , Hirota Eizi
Published: January 2005

The molecular structure and internal rotation of C2Cl6, SiCCl6, and Si2Cl6 molecules were investigated by means of the sector-microphotometer method of electron diffraction. An unmodified radial distribution function was proposed together with a reliability factor for the analysis of intensity curves obtained by the sector method.

Two methods were used for estimating the height of potential barrier; one, which is applicable in case of high potential barrier, is to compute the height from the observed mean square amplitude of the gauche chlorine pair, the contribution of the skeleton vibrations being evaluated by a calculation based upon the force field compatible with the observed normal frequencies. The other method, which is available in case of low barrier, is to calculate the scattering intensity of a model having a certain potential barrier by taking a weighted average over-all values of internal angle. For SiCCl6 both approximate methods resulted in almost the same value for the barrier height. The heights of the potential barrier obtained were 10.8, 4.3, and 1 kcal/mole for C2Cl6, SiCCl6, and Si2Cl6, respectively.
Separation of Boron Isotopes. I. Boron Trihalide Addition Compounds
Authors: Healy R. M. , Palko A. A.
Published: January 2005

Isotopic separation factors for several gas-liquid systems for concentrating boron isotopes have been determined. Separation factors at 25°C are:         System(B10/B11) liq/(B10/B11) gasBF3(g) vs anisole·BF3 (liq.)1.032±0.011 (95% C.I.)BF3(g) vs di−n−butyl sulfide·BF3 (liq.)1.033±0.005 (95% C.I.)BF3(g) vs phenol·BF3 (liq.)1.027±0.014 (95% C.I.)Separation factors for a number of BCl3-organic systems have also been studied, and a new compound (C6H5)2O·BCl3 has been prepared and characterized.
Stress-Enhanced Diffusion in Glass. II. Glass under Shear
Authors: McAfee Kenneth B.
Published: January 2005

Glass has been subjected to large shear strain to determine its effect upon the diffusion rate of gases through the solid. It was found that shear strain, γ, up to 4·10—3 does not alter the diffusion constant appreciably in the glass. Additional evidence is presented in support of the conclusion of the previous paper that the large increase in diffusion constant in glass results from the effect of tension. Arguments are expanded which support the interpretation that stress enhancement is caused by the reversible opening of submicroscopic fissures or channels in the random glass network.
Transference Experiments on Lead and Thallous Ions in Potassium Chloride Crystals
Authors: Fredericks William J. , Scott Allen B.
Published: January 2005

The electrolytic migration of lead and thallium in potassium chloride crystals to which small additions of lead chloride and thallous chloride have been made has been studied in a transference experiment. Lead was found to migrate toward the anode, indicating that it is bound in a negatively charged complex. Thallium did not migrate appreciably at temperatures below 600°; at higher temperatures it moved toward the cathode. Thallium clearly may exist as the simple cation at elevated temperatures; however, the results at lower temperatures do not permit a conclusion to be drawn with certainty regarding the existence of complex ions.
Reactions of Alkoxy Radicals. III. Photolysis of Methyl-d3 Acetate below 100°C
Authors: Wijnen M. H. J.
Published: January 2005

The photolysis of CH3COOCD3 has been investigated at 30 and at 90°C at varying initial pressures and light intensities. The following primary steps were shown to occur: (1a)CH3COOCD3+hv  →CH3CO+CD3O(1b)→CH3+CO2+CD3(1c)→CH3+CO+CD3O.The following reactions regarding methoxy and methyl radicals have been investigated: (3)CH3               →C2H6(6)CH3+CD3O        →CH3OCD3(7)→CH3D+CD2O(11)CD3O              →CD3OD+CD2O(16)CD3O+CH3COOCD3→CD3OH+CH2COOCD3(17)→CD3OD+CH3COOCD2.A value of about 1.4 was obtained for k7/k6 at 30 and 90°C, indicating the activation energy of reaction (7) to be zero kcal. Data obtained for the abstraction reactions (16) and (17) are discussed.

Quantitative data have been obtained and are discussed for the disproportionation and recombination reactions of methyl and acetyl radicals.
Vibrational Spectra and Thermodynamic Properties of ClF3 and BrF3
Authors: Claassen Howard H. , Weinstock Bernard , Malm John G.
Published: January 2005

The Raman and infrared spectra of ClF3 and BrF3 have been studied. The spectra of ClF3 give strong support for a planar T-shaped molecular model. The spectra of BrF3 are less complete but are sufficiently similar to that of ClF3 to confirm a like shape for this molecule. The fundamental vibrational frequencies of ClF3 observed for the vapor are 326(a1), 364(b2), 434(b1), 528(a1), 703(b1), and 752(a1) cm-1. S0 for ClF3, calculated statistically at the boiling point, 11.75°C, is 66.60 cal mole-1 deg-1 compared to the value of 67.04 obtained from a revised calculation of this quantity from available thermal data. For BrF3 only two fundamental frequencies were observed in the vapor, 613(b1) and 674(a1) cm-1; the others were estimated by a normal coordinate calculation. S0 for BrF3 calculated statistically is 70.86 cal mole-1 deg-1 at 43.11°C compared to a value of 71.90 calculated from available thermal data. Tables of the thermodynamic functions of ClF3 and BrF3 from 250 to 1000°K are given.
Characteristic Exponent for the Radial Wave Equation with a Maxwellian Potential
Authors: Drauglis E. , Widom B.
Published: January 2005

The radial Schrödinger equation with a repulsive R—4 potential energy is equivalent to a Mathieu equation, and the associated characteristic exponent is an important parameter in determining the properties of the solution. The characteristic exponent has been tabulated for the six lowest angular momentum states and for a range of energies of interest in molecular dynamics.
Effect of Pressure on Cyanide and Carbonyl Spectra in Solution
Authors: Wiederkehr R. R. , Drickamer H. G.
Published: January 2005

The C–N vibration of CH3CN has been studied in a series of solvents, mostly substituted methanes, to 10 000 atmospheres pressure. Shapes of the curves of frequency versus pressure can be predicted reasonably well from a model which considers the interaction of each bond of the solvent molecule with the CN bonds. It is possible to estimate the relative contributions of dispersion, orientation, induction, and repulsion forces to the net shift.

Similar measurements and calculations have been made for the C–O vibration in a series of compounds, using CS2 as the solvent. In this case, induction forces account for 65% of the observed interaction.
Ionization of Strong Electrolytes. VI. Nuclear Magnetic Resonance and Dissociation of Heptafluorobutyric Acid
Authors: Hood G. C. , Reilly C. A.
Published: January 2005

Proton and fluorine magnetic resonance of heptafluorobutyric acid in water have been measured and used to estimate a dissociation constant of 1.1. The effects of electrolytic dissociation below a mole fraction 0.5 and of dimerization and hydration above 0.5 are similar to those found for trifluoroacetic acid.
Nuclear Resonance Spectrum of Al27 in Chrysoberyl
Authors: Hockenberry John H. , Brown L. Carlton , Williams Dudley
Published: January 2005

The nuclear magnetic resonance spectrum of Al27 in a single crystal of chrysoberyl (BeAl2O4)4 has been investigated at room temperature in a field of 7800 gauss. The spectra obtained as the crystal was rotated about the three crystal axes have been interpreted on the basis of eight Al27 sites of two distinct types, the four sites of each type differing only in the orientation of the principal field gradients. Quadrupole coupling constants and electric field asymmetry parameters at the two types of sites were determined to be   Type I site  Type II siteCz=eQφzz/h2850±15 kc/sec2846±15 kc/secη=(φxx−φyy)/φzz0.94±0.020.76±0.02In addition, the orientation of the principal field gradients has been determined at each of the eight sites.
Proton Magnetic Resonance of the CH3 Group. IV. Calculation of the Tunneling Frequency and of T1 in Solids
Authors: Stejskal E. O. , Gutowsky H. S.
Published: January 2005

The thirty lowest eigenvalues of the Mathieu equation have been calculated numerically to nine places for a hindered rotor with threefold symmetry attached to a rigid framework. The results are tabulated for eight values of IV0/2ℏ2 ranging from 56.25 to 115.3125. The splittings of the torsional states of the CH3 group have been used to calculate the average tunneling frequency, νt, as a function of temperature for barrier heights of 825 cm—1 to 2770 cm—1. Some useful relations are developed between the eigenvalues and torsional splittings for the 2- and 3-nodal potential functions.

The BPP theory is used to calculate the proton spin-lattice relaxation time, T1, for CH3 groups undergoing hindered reorientations in solids and also over-all molecular tumblings, assuming Debye spectral density functions for both motions. The manner in which the tunneling affects T1 is considered at some length and two ways of introducing it are described. The coupling among the three protons within a given CH3 group is discussed briefly in relation to T1.
Infrared Spectra of the Isotopic Nitrous Oxides
Authors: Begun G. M. , Fletcher W. H.
Published: January 2005

The infrared spectra of N14N15O16, N15N14O16, and N15N15O16 have been observed from 2.5 μ to 20 μ using a model 112 Perkin-Elmer spectrometer. The frequencies of the three fundamental vibrational bands and fifteen overtone and combination bands have been tabulated and compared with the frequencies of N14N14O16. Using known anharmonic constants and isotopic relations, approximate zero-order frequencies have been calculated for the isotopic molecules. A set of force constants for infinitesimal displacements have been computed for the set of molecules, and the partition function ratios for the various species calculated from the data.
Compression and Densities of Four Solidified Hydrocarbons and Carbon Tetrafluoride at 77°K
Authors: Stewart John W. , La Rock Ralph I.
Published: January 2005

The piston displacement method of Bridgman has been used to measure the volume changes and compressibilities of solid ethane, ethylene, propane, propylene, and carbon tetrafluoride from 0 to 20 000 kg/cm2 at 77°K. The only polymorphic phase change observed is a first-order transition at P = 180±80 kg/cm2 at 77° in CF4. The densities of these solidified gases at 77° have been measured at atmospheric pressure by direct condensation into a volumetric flask. The accompanying pressure drop in a storage tank of known volume is observed.
Stark Effect from 1.1 to 2.6 Millimeters Wavelength : PH3, PD3, DI, and CO
Authors: Burrus C. A.
Published: January 2005

The Stark effect has been observed in the microwave rotational spectra of PH3 and PD3 at 1.1 and 2.1 mm wavelength, respectively, in DI127 at 1.5 mm, and in C12O16 at 2.6 mm. The J = 1→2 transition of PD3 has been observed at 1.08 mm. Analysis of the data yields values of the electric dipole moment, μ, as follows: PH3, 0.578±0.010 debye; DI, 0.316±0.010 debye; and CO, 0.112±0.005 debye. The centrifugal stretching constants, DJ and DJK, for PD3 are found to be 0.800 Mc and 1.31 Mc, respectively.