bluuebunny/crossref_metadata_2025 huggingface dataset:
Motions of Molecules in Condensed Systems. XI. Infrared Spectrum and Structure of a Single Crystal of Ethylene
Authors: Brecher Charles , Halford Ralph S.
Published: July 2004

The infrared absorption spectra of thin sections of single crystals of ethylene have been recorded in the frequency range between 650 and 3600 cm−1, using polarized infrared radiation. Comparisons are made with similarly recorded spectra of the liquid and vapor phases. A complete assignment of the absorption bands is given. The frequencies of some primary lattice modes of the molecule in the crystal, and of some inactive molecular modes, are inferred from combinations. The ethylene crystal is found spectroscopically to be monoclinic (C2h) or orthorhombic (D2h), with the molecules located at sites of Ci symmetry. Using the known lattice of the carbon atoms, a molecular arrangement, described by space group P 21/n (C2h5), is derived as the true crystal structure.
Wave Functions and Intensity Calculations for a Rotating Anharmonic Oscillator
Authors: James Thomas C.
Published: July 2004

Wave functions which are good through second-order perturbation theory are given for a harmonic oscillator perturbed by a potential of the form V = ℏw (ax+bx2+cx3). These results are then applied to the case of a rotating anharmonic oscillator. Expressions are also given for overlap integrals 〈n̄ | m〉 between different unperturbed harmonic oscillator wave functions. A brief comparison of this treatment with similar treatments is given and a discussion of rotation-vibration interaction in non 1Σ states is included. The application to intensity calculations in electronic and infrared spectra is discussed. An approximate expression for the dipole moment matrix element 〈1J′ | u | 0J〉 is given.
Vapor Pressure of Antimony by the Torsion-Effusion Method
Authors: Rosenblatt Gerd M. , Birchenall C. Ernest
Published: July 2004

The pressures and mean molecular weights of the vapors over solid antimony (420–550°C) and solid zinc (250–335°C) have been determined by simultaneous measurements by the torsion-momentum and Knudsen weight loss methods. The torsion measurement was calibrated with mercury at 30° using a mercury vapor pressure of 2.96×10-3 mm Hg determined by concurrent weight loss experiments. Zinc vapor is confirmed to be monatomic. The zinc pressure data are represented by logPmm=(8.741±0.218) — (6630±125) /T giving ΔH298° (vap)=30.73±0.57 and 31.18±0.12 kcal/mole by the second law and third law of thermodynamics, respectively, in excellent agreement with previously reported results. The vapor over solid antimony is all Sb4 molecules within experimental error. Least-squares analysis of the antimony data yields logPmm=(10.571±0.090) — (10 300±68) /T, pressures 10%-40% lower than those previously reported. The heat of vaporization of Sb4(g) at 298.16°K is 49.83±0.31 kcal/mole by the second law and 49.45±0.09 by the third law of thermodynamics. This thermodynamic consistency and the agreement of the zinc results with accepted measurements indicate that the antimony pressures presented should be preferable to those previously reported.
Transition Probabilities in Multilevel Systems: Calculation from Impulsive and Steady-State Experiments
Authors: Carrington Tucker
Published: July 2004

The study of collision-induced transitions of molecules in a system of many energy levels is discussed in an analysis of time-dependent and steady-state experiments. These results are used in a discussion, with numerical examples, of the difficulties in calculating the transition probabilities from observed population distributions.

An intimate conceptual and mathematical relationship is established between two types of experiments which are possible at present. One is an impulse, or time-dependent experiment such as excitation with a fast flash lamp and snapshot observation after a known delay time. The other is a steady-state experiment in which molecules are fed into the system (a gas or a surface) at a single energy level, for example, and undergo transitions among the available levels in competition with a first-order removal process such as spontaneous radiation or desorption from a surface.

The ideas summarized above are used to develop procedures for calculating transition probabilities from observed population distributions. Numerical examples and qualitative considerations indicate that when transitions involving more than single quantum jumps are involved, the experimental data must be known to much higher accuracy than that desired in the transition probabilities. The difficulties increase rapidly as the number of levels in the system increases.
Law of Corresponding States for Fused Salts
Authors: Reiss H. , Mayer S. W. , Katz J. L.
Published: July 2004

Reduced equations of state are developed for strictly ionic salts through an analysis of the configuration integral. In this way, appropriate laws of corresponding states are developed for vapor pressures, surface tensions, and melting points. Agreement between theory and experiment is satisfactory for a large class of salts.
Momentum-Correlation Function in a Rayleigh Gas
Authors: Mazo Robert M.
Published: July 2004

The time-correlation function in an equilibrium ensemble of the momentum of a heavy particle imbedded in a gas of noninteracting light particles is calculated. The technique used is a density expansion of the correlation function. No statistical hypothesis beyond that of canonical ensemble at the initial time is used.
Photoionization of Ce3+ in Glass
Authors: Stroud Jackson S.
Published: July 2004

The photoionization of Ce3+ is investigated by determining the optical absorption changes and the electron spin resonance changes that occur when cerium-containing silicate glasses are illuminated with ultraviolet light. The results are: (1) The room temperature quantum yield of photoelectrons from Ce3+ is 0.1. (2) The optical absorption and the electron spin resonance bands caused by trapped photoelectrons are found. (3) A Ce3+ ion from which a fourth electron has been removed by photoionization is different from a Ce4+ ion.
Monolayer Adsorption of Helium on Argon
Authors: Ross Marvin , Steele William A.
Published: July 2004

Experimental isotherms and heats of adsorption of helium on an argon surface are reported for temperatures from 10° to 20°K. The potential energy of interaction of a helium atom with an argon surface is calculated by summing the He–Ar pair interaction over the solid lattice. The experimental data are analyzed in terms of a quantum mechanical modification of the theoretical treatment presented previously [W. A. Steele and M. Ross, J. Chem. Phys. 33, 464 (1960) (I); 35, 850 (1961) (II)]. It is shown that the adsorption properties calculated from the a priori potential function are in quantitative agreement with the experiments, in the region where a quantitative comparison can be made, and that the remainder of the data is in agreement with semiquantitative theoretical estimates. A detailed description of the probable adsorption process for the He–Ar system is deduced from the comparison between experiment and theory. It is concluded that the first half of the helium atoms comprising a monolayer on this surface are highly localized at equivalent positions over the argon lattice unit cells, and are nearly all in their quantum mechanical ground state at temperatures up to 20°K. The second half of the atoms in the monolayer is adsorbed over a different position relative to the solid lattice, and is more weakly bound than the first. Although the quantitative comparison between the theory and the experiment is somewhat limited because the quantum version of the theory is not as complete as the classical, it is concluded that the agreement between experiment and theory indicates that this approach to the problem of physical adsorption may prove useful in the analysis of data taken on other suitable systems.
Electrical Conductivity and Thermodynamic Equilibrium in Nickel Oxide
Authors: Mitoff S. P.
Published: July 2004

The electrical conductivity of nickel oxide has been studied at temperatures between 600° and 1350°C and partial pressures of oxygen between 1 atm and 10−4 atm. The slope of log conductivity vs reciprocal temperature plots increases when the temperature is high enough for the sample to come into thermodynamic equilibrium with the atmosphere, and the temperature at which the change in slope occurs is observed to depend on the rate of heating or cooling of the crystal. The heat of formation of nickel vacancies may be determined from the magnitude of the change in slope by a simple calculation. Nickel oxide is a p-type semiconductor [M. Verwey, M. Haaijman, H. Romeijn, and M. van Oosterhout, Philips Research Repts. 5, 173 (1950)] in which the conductivity is proportional to the concentration of Ni3+ ions in the lattice. When thermodynamic equilibrium is established with the atmosphere the conductivity is proportional to the ⅙th power of the oxygen partial pressure.

The analysis of the conduction mechanism and the conduction data may be self-consistently correlated with nickel diffusion, nickel vacancy diffusion, and weight changes resulting from equilibration with different oxygen partial pressures. The following constants may be determined from these correlations: heat of formation of nickel vacancies, activation energy for nickel vacancy migration, activation energy for electron hole migration, and concentrations of nickel vacancies and Ni3+ ions as a function of temperature and oxygen pressure. Combined results give the following for the concentration of nickel vacancies: 0.11 (PO2)⅙ exp(−17 800/RT) vacancies per ion pair.
General Theory of Polymer Solutions
Authors: Fixman Marshall
Published: July 2004

A general theory of the thermodynamic properties of polymer solutions is given. The theory is intended to be valid for every concentration range. The formalism begins with the assumption of some functional relation between the local free energy density, for an assigned polymer configuration, and the local concentration of segments belonging to various polymer chains. That is, the thermodynamic properties of the segments are presumed known, and the problem is taken to be the determination of changes in the thermodynamic properties which are induced by a joining of the segments into a polymer chain. The local segment concentration is assumed to be close enough to the bulk or average concentration that a Taylor series expansion of the local free energy can be made and cut off at the term containing the square of the fluctuation in local concentration. The resulting free energy of the whole solution can then be cast into a form which includes as one part the free energy of a random distribution of segments, and as a second part the free energy of an imperfect gas with a pairwise additive intermolecular potential, albeit a concentration-dependent potential. At low concentrations the results are identical to previous treatments based on imperfect gas theory. At high concentrations a previously introduced calculation of the radial distribution function is employed to show that the thermodynamic properties are accurately described as those of a random distribution of segments. The Flory-Huggins formula is an example of a free-energy function which can be assumed to hold locally at any concentration, but is then found to hold macroscopically only at high concentrations.
Scattering of High-Velocity Neutral Particles. XII. He–CH4; He–CF4. CH4–CH4 and CF4–CF4 Interactions
Authors: Amdur I. , Longmire M. S. , Mason E. A.
Published: July 2004

Collision cross sections have been measured for helium atoms with energies between 500 and 2100 ev, scattered in room-temperature CH4 and CF4. The results have been analyzed to obtain the average potential between a helium atom and a CH4 molecule, 〈V(r)〉Av=602/r9.43ev,for r between 1.92 and 2.37 A, and the average potential between a helium atom and a CF4 molecule, 〈V(r)〉Av=6.18×106/r17.51ev,for r between 2.43 and 2.74 A. This He–CH4 potential is consistent with one valid at larger separation distances which has been obtained by combining potentials derived from high-temperature viscosity and second virial coefficients of helium, and from high-temperature viscosity coefficients of methane.

A procedure which assumes the centers of force to reside in the peripheral H or F atoms has been used to analyze these average atom-molecule interactions in terms of the effective He–H and He–F interatomic potentials. These interatomic potentials have been combined with the potential previously determined for He–He to obtain effective H–H and F–F potentials for atoms in different CH4 and CF4 molecules. These effective interatomic potentials were then summed and averaged over all molecular orientations to yield the average potential between two CH4 molecules, 〈V(r)〉Av=5.64×106/r15.47ev,for r between 2.47 and 3.06 A, and the average potential between two CF4 molecules, 〈V(r)〉Av=1.17×1022/r39.27ev,for r between 3.43 and 3.77 A. This CH4–CH4 potential is consistent with one valid at larger separation distances which has been derived from measurements on gaseous viscosity at high temperatures.
Effect of Pressure on the Spectra of Transition Metal Ions in MgO and Al2O3
Authors: Minomura S. , Drickamer H. G.
Published: July 2004

The effect of pressure to 150 kbar has been measured on the spectra of several transition metal ions in MgO and Al2O3. In general, there is an increase in crystal field strength with increasing pressure. The inter-electronic repulsion parameter decreased slightly with increasing pressure indicating a small increase in covalency. For Al2O3, Dq shifts as (V0/V)5/3 indicating that the R−5 law holds, and the local compressibility is the same as the bulk compressibility. In MgO the shift is always more rapid than R−5, indicating local relaxation near the foreign ion. Above about 50 kbar there is a marked increase of trigonal distortion in Al2O3.
On the Classical Boltzmann Equation for Gases
Authors: Andrews Frank C.
Published: July 2004

With great simplicity we formulate the Boltzmann equation for dilute classical gases from the reduced Liouville equation by using the three assumptions: no three-body effects, collision time much less than the experimental time, and negligible change in local properties of the system over distances of order of the range of the intermolecular forces. The nature of these assumptions sheds some light on recent attempts to generalize the Boltzmann equation. We find that it is easy formally to relax the first assumption to permit more than two-body effects. The resulting equation is an intuitive extension of the Boltzmann equation.
Infrared Spectra of Carbon Monoxide as a Solid and in Solid Matrices
Authors: Maki Arthur G.
Published: July 2004

The fundamental infrared absorption frequency of several isotopes of CO has been observed in solid carbon monoxide and in the solid matrices N2, Ar, and CH4. In addition, the overtone in solid carbon monoxide has been measured. It is shown that frequency shifts due to isotopic substitution in the solid state follow the formulas developed for the gas phase only when molecules of the same isotopic species are not adjacent to each other, i.e., only in dilute solutions.
Molecular-Weight Dependence of the Viscoelastic Properties of Whole Polymers
Authors: Peticolas Warner L. , Menefee Emory
Published: July 2004

A method has been developed by which it is possible to determine the type of molecular weight averaging upon which viscoelastic properties of polymers may depend and which may be used to verify the normal-coordinate theory of viscoelasticity for various types of polymers. The method is extraordinarily simple to carry out since it involves only measurement of the property on whole polymers and mixtures of whole polymers. Neither fractionation nor molecular-weight measurements themselves are required.

Methods of determining the correct average-molecular-weight dependence of melt viscosity and steady-state elastic compliance have been worked out in detail and are illustrated with data on linear polyethylenes.

The method is also applicable to other polymer properties which are molecular-weight dependent.
Theory and Measurement of Pressure-Induced Shifts of HCl Lines Due to Noble Gases
Authors: Ben-Reuven A. , Kimel S. , Hirshfeld M. A. , Jaffe J. H.
Published: July 2004

Pressure shifts of HCl absorption lines in both the 1–0 and 2–0 bands caused by five noble gases have been measured. An outstanding feature of these measurements is that the shifts are not the same for all lines of a band, but there is a strong dependence on the rotational quantum number J. However, there is evidence that the shifts tend to a constant limit for high J numbers. In order to interpret these results induction- and dispersion-type van der Waals forces were considered and used in conjunction with existing line-shape theories. In cases where perturbation theory can be applied, the limit shifts were accounted for fairly well, although no satisfactory explanation has emerged for the J dependence. Attention is drawn to the significance of observations of this sort as a means of obtaining information about intermolecular forces and molecular constants. Of particular interest is the possibility of obtaining such information for molecules in specific quantum states.
Microwave Faraday Effect in Weakly Magnetic Gases
Authors: Sage Martin L.
Published: July 2004

The microwave Faraday effect is proposed as a method of measuring rotational magnetic moments in gases. The theory of the Faraday effect is developed by using the method of Karplus and Schwinger. In particular, it is applied near a microwave absorption frequency of the gas. The magnitude of the effect indicates that the Faraday effect may be a more satisfactory method of measuring small (less than 0.1 nuclear magneton) magnetic moments than the Zeeman effect. However, it requires intensity rather than frequency measurements and is therefore difficult.
Measurement of the Resistivity of Cesium at Elevated Temperatures
Authors: Hyman Julius
Published: July 2004

An experiment is described in which the electrical resistivity of liquid cesium was measured from ambient temperature to 419°C, and experimental values are presented. In the low-temperature region the data agree quite well with measurements made by others. A linear approximation which best correlates the data from the melting point to 419°C to ±1% is ρcs=38.5[1+0.00308(T−50)] μ ohm−cm.Here T is temperature in degrees centigrade. By use of the Widemann-Franz relation, a thermal conductivity of 0.048 to 0.050 cal/sec-deg C-cm is predicted.
Gaseous Detonations. XIII. Rotational and Vibrational Distributions of OH Radicals
Authors: Kistiakowsky G. B. , Lyon R. K.
Published: July 2004

In an earlier paper in this series, some observations of the rotational temperature of OH radicals in the reaction zone of gaseous detonations were reported and interpreted as meaning that abnormal rotational excitation is produced by extremely fast chemical reactions. In the present study new experiments were made on detonations of C2H2+2½O2 and CO+H2+O2 mixtures. An improved method of data reduction was developed and applied to both the new and the previously reported experiments. It is concluded that in all reported experiments the vibrational and rotational distributions of OH remain the same within experimental errors from the front of the wave to beyond the C-J plane. This is tentatively attributed to the turbulent gas flow behind the detonation front which restricts the usefulness of the present method, rather than to abnormal distributions in the reaction zone caused by fast chemical reactions.
Light Scattering by Anisotropic Inhomogeneities in Thin Polymer Films under Strain. II
Authors: Bhatnagar Hari L.
Published: July 2004

Scattering by anisotropic inhomogeneities embedded in thin polymer films under two- and three-dimensional strain is treated theoretically. To take into account the effect of polydispersity, the differential cross sections for scattering are obtained for an assumed Maxwellian distribution in size at constant value of p, the ratio of the minor to major axis of an inhomogeneity.
Atomic Polarization. II. Vibrational Polarization of Liquids
Authors: Illinger Karl H. , Smyth Charles P.
Published: July 2004

A theory applied specifically to the problem of the vibrational polarization of liquids is presented, and a detailed discussion is given of the vibrational polarization terms in isotropic condensed states.
Atomic Polarization. III. Vibrational Polarization Terms Associated with Forbidden Transitions in Polyatomic Molecules
Authors: Illinger Karl H. , Smyth Charles P.
Published: July 2004

The contribution, to the total vibrational polarization, of transitions forbidden by harmonic oscillator selection rules is examined for the case of polyatomic molecules in the gaseous state. Numerical calculations are given for a number of molecules. In connection with these results, criteria are developed for the completeness of the treatment, developed in a previous paper, taking into account the anharmonicity of the vibrations but limiting the contributions to those associated with transitions allowed by harmonic oscillator selection rules. The present work permits one to draw conclusions as to the applicability of this approximation to a given polyatomic molecule.
Atomic Polarization. IV. Temperature Dependence of the Vibrational Polarization of Gases
Authors: Illinger Karl H. , Smyth Charles P.
Published: July 2004

A treatment of the temperature dependence of the vibrational polarization of gases is given in several degrees of approximation. Calculations are presented for a number of molecules.
Atomic Polarization. V. Normal Mode Polarizability and the Additivity of the Vibrational Polarization
Authors: Illinger Karl H.
Published: July 2004

The vibrational polarizability of a molecule is derived in several degrees of approximation and is calculated for a number of molecules. An extension of this treatment is then presented, terminating in the development of the properties of the normal mode polarizability. The criteria for the additivity of the vibrational polarization of a molecule in terms of the normal mode polarizabilities of its constituent segments are developed. Numerical calculations of the normal mode polarizability terms are given for a large number of molecules.
Atomic Forces and Thermal Effects in Solids
Authors: Rosenstock Herbert B.
Published: July 2004

It is shown that the vanishing of an interatomic force constant in a solid can produce specific heat anomalies very similar to the familiar ``lambda point'' phenomena. Possible application of this to higher order phase transitions is discussed.
Effect of Pressure on the Spectra of Certain Complexes of Cu++, Co+++, and Fe++
Authors: Stephens D. R. , Drickamer H. G.
Published: July 2004

The effect of pressure is as measured on the spectra of four Cu++ salts, and on K3COF6 and FeSiF6·6H2O. The four Cu++ salts have varying degrees of distortion from octahedral (or tetrahedral) symmetry. For the Tutton's salt (the more distorted octahedral complexes) there were measurably larger effects on the shift and especially on the intensity of the transition. The Co3+ and Fe++ systems were compared to investigate the possibility of crossover from spin free to spin paired arrangement in the former. From the data it is estimated that this should occur at 220–250 kbar.
Paramagnetic Resonance Absorption of the Dimesitylmethyl Radical
Authors: Chesnut D. B. , Sloan G. J.
Published: July 2004

The isotropic hyperfine structure of the electron paramagnetic resonance spectrum of the dimesitylmethyl radical has been observed. Nearly 300 of the 910 theoretical lines have been resolved and analyzed in terms of the coupling constants of the various nuclear species. A spin-density distribution throughout the molecule has been deduced from the measurements and is compared with recent theoretical calculations.
Cubic Potential Surfaces in the Transition-State Theory of Unimolecular Reactions
Authors: Slater Noel B.
Published: July 2004

The frequency factor of a unimolecular dissociation rate is enhanced if the molecular vibrations are loosened during the approach to the activated state; this loosening may be regarded as affecting the partition function or entropy in the nonreactive degrees of freedom. These ideas are illustrated here in terms of cubic potential surfaces, with examples of linear molecules and of the effect of freeing an internal rotation. As a more general but related point, the uniqueness of the reaction coordinate of transition-state theory is discussed with some reference to isotope effects.
Thermodynamic Properties of Trifluoroacetonitrile from 12°K to Its Boiling Point
Authors: Pace E. L. , Bobka R. J.
Published: July 2004

The saturated heat capacities of trifluoroacetonitrile have been measured from 12°K to the normal boiling point 205.47°K. The vapor pressure of the liquid to 1 atm is represented by the equation log10Pmm=−1337.916/T−4.02312 log10T+18.69693.The solid-liquid-vapor triple-point temperature is 128.73°K. The heat of fusion at the triple point and the heat of vaporization at the normal boiling point are, respectively, 1187.7 cal/mole and 4262 cal/mole. The experimental value of the entropy of the gas at the normal boiling point, 65.01±0.20 eu/mole, is in excellent agreement with the theoretical value of 64.96 eu/mole calculated from spectroscopic and molecular data assuming a symmetrical top molecule.
Anharmonic Potential Constants and Their Dependence upon Bond Length
Authors: Herschbach Dudley R. , Laurie Victor W.
Published: July 2004

Empirical study of cubic and quartic vibrational force constants for diatomic molecules shows them to be approximately exponential functions of internuclear distance. A family of curves is obtained, determined by the location of the bonded atoms in rows of the periodic table. Displacements between successive curves correspond closely to those in Badger's rule for quadratic force constants (for which the parameters are redetermined to accord with all data now available). Constants for excited electronic and ionic states appear on practically the same curves as those for the ground states. Predictions based on the diatomic correlations agree with the available cubic constants for bond stretching in polyatomic molecules, regardless of the type of bonding involved. Some implications of these regularities are discussed.
Determination of Excited-State Dipole Moments of Azulene
Authors: Robertson W. W. , King A. D. , Weigang O. E.
Published: July 2004

The absorption spectra of three transitions of azulene were observed in a number of polar and nonpolar solvents. These frequency shifts were used to evaluate the constants in an equation developed by McRae representing solvent-solute interactions, and the constants gave the change in dipole moment for each of the transitions.
Formulation of a Cell Model Using Periodic Boundary Conditions
Authors: Squire David R. , Salsburg Zevi W.
Published: July 2004

A cell-type model for the liquid state, based upon the consideration of small systems with periodic boundary conditions, is introduced. The equation of state for rigid-sphere molecules is then calculated for a tetragonal cell. By properly choosing the dimensions of the tetragonal cell, the equation of state for a system of rigid spheres which form a face-centered cubic lattice in their regular lattice configuration is obtained. The model yields the correct second virial coefficient. The results are compared with the Monte Carlo calculations of Wood and Parker, the ``averaged model'' results of Buehler et al., and the Lennard-Jones and Devonshire theory.
The Effect of Impurities on the Molecular Weight Distributions of Anionic Polymers
Authors: Orofino T. A. , Wenger F.
Published: July 2004

The deactivating influence of impurities in anionic polymerizations is considered from the point of view of the ultimate molecular weight distributions obtained with various systems.

With the assumption that initiation is much faster than propagation, theoretical expressions for the weight distribution functions and the weight-to-number average chain length ratios are derived for the cases in which mono- and bifunctional growing chains are subjected throughout the course of polymerization to given, fixed ratios of monomer to impurity concentrations. The relationships obtained are shown to be applicable to systems of practical interest.

The molecular weight distributions of both mono- and bifunctional anionic polymers derived from the foregoing model are found to broaden with increasing impurity content in the monomer supply. The molecular weight distributions for the latter are narrower than those for the former at corresponding levels of impurity content. For moderate degrees of deactivation, the weight distribution function for bifunctional polymers exhibits the characteristic maximum as well as the rudiments of a second relative maximum at lower molecular weight.
Taylor Series Expansion of the Intermediate Coupling Energy Levels of Nd3+ and Er3+
Authors: Wong Eugene Y.
Published: July 2004

A Taylor series expansion of the intermediate coupling energy levels for Nd3+ and Er3+ was calculated. New energy levels can be calculated without rediagonalizing the matrix. A calculation for NdCl3 is discussed as an example.
Thermodynamics of the Vaporization of Nickel Oxide
Authors: Grimley R. T. , Burns R. P. , Inghram Mark G.
Published: July 2004

A mass spectrometric investigation of the vapor species in equilibrium with nickel oxide has shown the vapor phase to consist of Ni, O2, NiO, and O, whereas the solid phase consists of a NiO solid solution and Ni(s). The dissociation energy of NiO(g) was found to be 86.5±5 kcal/mole.
Parameterization of Orthogonality and Normalization Conditions for the NbF7—2 Structure
Authors: Wilson Russell L. , Duffey George H.
Published: July 2004

General spd hybrid orbitals of C2v symmetry were set up for the distorted trigonal prism NbF7—2 structure. The orthogonality and normalization conditions were introduced and expressed in parametric form. On varying the parameters, the authors found the greatest Pauling strength, averaging 2.987, when the composition was s0.89p2.49d3.62.
Approximate Analytical Wave Functions for the 1s2ns 2S½ States of Li and Li-Like Ions
Authors: Ritter Z. W. , Pauncz R. , Appel K.
Published: July 2004

Calculations have been made for the 1s22s, 1s23s, 1s24s, 1s25s, 2S½ states of Li and Li-like ions. The functional form used allows for radial correlation in the inner shell and gives sufficient flexibility for describing the outer electron. The energy values obtained for the ground state are the best among calculations which do not introduce interelectronic coordinates or angular correlation. The energy values for the excited states differ by not more than 1% from the experimental values.
Double and Triple Ionization in Molecules Induced by Electron Impact
Authors: Dorman F. H. , Morrison J. D.
Published: July 2004

Double and triple ionization by electron impact in molecules is examined and, as was found for the monatomic gases, the data support the view that the threshold law for the probability of double ionization is a square-law function of the excess electron energy. Some excited states have been detected, and autoionization does not seem to be important. The vertical potentials for all the processes of multiple ionization observed have been measured. The relative electronic-transition probabilities for single, double, and triple ionization are compared. The factors affecting the stability of multiply charged molecular ions are discussed, and an attempt is made to correlate the electron impact data with the molecular structures. It is shown that Coulomb repulsion between the separated charges causes the potential energy functions describing these ions to be of unusual form.
New Potential Function for Alkali Halide Molecules
Authors: Varshni Yatendra Pal , Shukla Ramesh Chandra
Published: July 2004

A new potential-energy function has been suggested for the alkali halide molecules, U=(−e2/r)+Pexp(−kr2),where P and k are constants. Values of αe, ωeχe, and the ionic binding energy Di have been derived for the following three functions: (1) simple Born-Mayer potential, (2) Rittner potential, and (3) the above suggested potential. The results obtained with the new function are much better than those obtained with the Born-Mayer potential, but slightly inferior to those obtained with the Rittner potential.
Collision and Activated Complex Theories for Bimolecular Reactions
Authors: Yang Kang , Ree Taikyue
Published: July 2004

By using the principles of classical mechanics, the specific rates k′ of bimolecular reactions which proceed without activation energies were obtained by taking the average of πbc2g, where bc is the critical impact parameter and g is the relative molecular velocity. The result is k′=(β/μ)(kT)(s−4)/28C2/8.Here, C and s are the constants appearing in the attractive potential, C/rs(s>2), between two reacting molecules separated by a distance r, β is a dimensionless quantity involving s, μ is the reduced mass, and other symbols have their usual meaning. After substituting proper potential parameters into the above equation, we obtained the rates of the reactions for the systems, ion-molecule and radical-radical, in exact agreement with the rates in the literature obtained using the activated complex theory. The reason for the agreement was considered, and it was shown that under two conditions pointed out in the text the equations of k′ obtained from the activated complex theory transform to those derived from the classical collision theory.
Infrared Chemiluminescence in the System H+NOCl
Authors: Cashion J. K. , Polanyi J. C.
Published: July 2004

Infrared emission has been observed arising from the low-pressure gas-phase system H+NOCl; HCl emission consists of the fundamental spectrum (Δv=1), and first and second overtones (Δv=2 and 3) of the ground electronic state. HCl† (vibrationally excited HCl in its ground electronic state) must be present in levels up to and including v=9 (possibly 10). The distribution of HCl† among vibrational levels is non-Boltzmann, indicating that some or all are formed by a chemical reaction rather than a thermal process. This reaction is thought to be H+NOCl→HCl†+NO. Only a weak emission due to NO† was observed. An emission of intensity comparable to HCl† was observed in the region of the ω1 fundamental of NOCl. From the stationary state distribution of HCl† among vibrational levels a calculation was made of the relative rate constants kv for reaction into each accessible vibrational level of HCl†. An examination of the stationary state distribution of HCl†v=1 among rotational levels indicates that while the over-all distribution is non-Boltzmann, rotators in high rotational levels are in approximate equilibrium at ∼2000°K and rotators in the lowest levels are in a distribution which roughly corresponds to that for 650°K. The absolute intensity of the infrared emission was found to be ∼0.05 w. This is equivalent to roughly 0.2 to 2.0% of the energy liberated by the reaction. From the emission intensity the partial pressure of HCl†v=1 was calculated to be ∼6×10—3 mm Hg, that is ∼0.3% of the total reagent pressure.
Uranium Monosulfide. II. Mass Spectrometric Study of Its Vaporization
Authors: Cater E. David , Rauh E. G. , Thorn R. J.
Published: July 2004

A study of the vapor effusing from a tungsten effusion cell containing uranium monosulfide has been performed with the aid of a time-of-flight mass spectrometer. Between 1700° and 2150°C uranium monosulfide vaporizes predominantly according to the reactions US(s)=US(g),and US(s)=U(g)+S(g),and to a detectable extent at 2100°C and above by the reaction 2US(s)=US2(g)+U(g).Least squares treatment of the ion current ratio IUS+/IU+ as a function of temperature between 1885° and 2130°C yields the relationship ΔHT°(I) —[ΔHT°(II)/2]=14.6±2.4 kcal/mole, where the error is estimated. In the presence of very small amounts of oxygen in the solid monosulfide the vapor species UO and UOS are found. A faint peak in the spectrum at mass 264 is suspected to have been due to ThS+.
Deionization Cross Section for Oxygen
Authors: Breene R. G.
Published: July 2004

Our atomic- and free-electron wave functions are applied to the calculation of the deionization cross section for O II. Our s- and d-wave numerical solutions to the free-electron wave equation is fitted to Coulomb functions for normalization. This result is used to determine the cross section for the transitions s wave to 2p orbital and d wave to 2p orbital. We carried out an approximate calculation for the transition to the 3p orbital with the resulting indication that the hydrogen result may reasonably be used. For the contributions from transitions to 3d and higher orbitals the hydrogen cross sections have been adopted. Our final result is 198×10—21 cm2 leading to a rate constant for radiative deionization of 218×10—14 cm3/sec.
Time Dependence of the Statistical Molecular Weight Distribution of the Polymer Resulting from Vinyl Polymerization
Authors: Nanda V. S. , Pathria R. K.
Published: July 2004

The problem of the variation with time of the statistical distribution in a polymer resulting from vinyl polymerization has been investigated. Starting from the general formula for the number distribution function of the polymer increment, formed during the time interval t to t+δt, an expression is obtained for the over-all distribution in the material polymerized up to a particular stage of the reaction. Expressions have also been obtained for the various averages pertaining to the over-all material. The integrals occurring in the final formulas cannot, in general, be evaluated in a closed form. Results are obtained in such cases by having recourse to the Chebyshev method of numerical integration. A discussion of the interesting features that emerge out of this investigation is also given.
Distribution of Space Charge in Homogeneous Metal Oxide Films
Authors: Butler James N.
Published: July 2004

Poisson's equation is solved exactly for a homogeneous semiconducting oxide film on a metal or semiconductor substrate. The potential drop from the interior of the substrate to the external surface of the oxide is given as a function of the thickness of the oxide, and the distribution of potential within the layer is given. The form of the functions is shown for an arbitrary choice of constants and the potential drop across the oxide film as a function of thickness is calculated for Cu2O on Cu at 1000°C.
Surface Energy Effect on Diffusion-Controlled Particle Growth
Authors: Somorjai G. A.
Published: July 2004

A theory of diffusion- and surface-energy-governed particle growth is presented for spherical precipitates in solids. The high surface energy of small particles retards the growth in the initial stage of the process. For large particles the limiting case is the diffusion-controlled growth as the surface-energy contribution becomes negligible.
Studies in Molecular Structure. V. Computed Spectroscopic Constants for Selected Diatomic Molecules of the First Row
Authors: Fraga S. , Ransil B. J.
Published: July 2004

Limited LCAO MO functions were computed for several diatomic molecules at four different values of the internuclear distance near Re, and the corresponding total energies fitted to a third degree polynomial in R. Spectroscopic constants ωe, ωexe, Be, αe, Re, ke were derived from the resulting potential curve and compared to observed values. The good agreement obtained in most cases suggests a valuable application of the self-consistent field function. In addition calculations were made for a few more values of the internuclear distance providing a potential curve over a reasonably broad range around Re.
Theory of Proton Magnetic Shielding
Authors: Fixman Marshall
Published: July 2004

If an unsymmetrized product of molecular orbitals is used to represent the ground state of a molecule, the proton magnetic shielding is the sum of contributions from each molecular orbital. In the simplest variation theory of the perturbation of these orbitals by the proton magnetic dipole and an external magnetic field, the perturbation vanishes if the vector potential representing the external field is caused to vanish at the charge centroid of the orbital. Proton magnetic shielding constants are evaluated on this basis with molecular orbitals of the form ψ(1) = [(1—γ)ψa2(1)+γψb2 (1)]½. This form was first examined by an energy variation on H2, the energy being minimized with respect to internuclear distance and a screening constant, and was then applied to proton magnetic shielding in H2. In subsequent calculations γ was evaluated from electric dipole moments when possible. Proton magnetic shielding constants were then evaluated for the C–H bond (methane, ethylene, and acetylene), the Group VI hydrides (H2O, H2S, H2Se), and the hydrogen halides (HF, HCl, HBr, HI).
Heat Capacities of DyCo5 in Relationship to Its Magnetic Anomaly, Third Law Entropies, and Related Thermochemical Data
Authors: Saba William G. , Wallace W. E.
Published: July 2004

Heat capacities of DyCo5 are reported for the temperature range extending from 12° to 470°K. Evaluation of the third law entropies of the compound gives [in cal deg—1 (g formula weight)—1] 55.61±0.05 and 72.05±0.07 at 298.16° and 450°K, respectively. Excess heat capacity is observed between 275° and 400°K, seemingly due to the previously observed magnetic anomaly at 360°K. Analysis of the data suggests that there is an appreciable magnetic contribution to the heat capacity throughout the temperature range covered. The profile of the thermal anomaly at about 350°K is unusual suggesting that the alteration of magnetic structure which produces it is also unusual.
Molecular Vibrations and Structures of High Polymers. I. General Method of Normal Coordinate Treatment by Internal Coordinates and Infrared Frequencies and Conformations of (—CH2—)n, (—CH2–O—)n, and (—CH2–O–CH2—)n
Authors: Miyazawa Tatsuo
Published: July 2004

The normal coordinate treatment of the (—A—)n chain was made in terms of internal symmetry coordinates and optically active frequencies of (—CH2—)n were calculated for various chain conformations. The calculated frequencies of polyethylene and cyclopentane agreed with the observed values. The low infrared frequency was found to be structure sensitive. The infrared band of polytetrafluoroethylene at approx 100 cm—1 may be primarily due to this mode. The low infrared frequencies of polyoxymethylene were compared with the corresponding frequencies of (—A—)n calculated for various conformations and were found to be in accord with Huggins' model but not with the planar zigzag structure. The normal coordinate treatment of (—A—B—)n was made taking into account the torsional potential as well as the stretching and bending potentials, and vibrational assignments of polyoxymethylene were made. For poly-(ethylene glycol) a structure model was proposed. This model is made up of only the gauche configuration throughout the helical chain and contains seven chemical units and five turns of the helix per fiber period. The polarized infrared spectra of this polymer were measured in the region 800–400 cm—1 and the observed skeletal frequencies were compared with the corresponding frequencies of (—A—)n calculated for various conformations. The infrared spectra were found to be in accord with the model proposed here. The infrared spectra in the rocksalt region were also reasonably assigned. Finally a general method of treating any infinite helical chain belonging to dihedral group is presented in terms of real internal symmetry coordinates. The G or F matrix of an infinite order is factored into the set of matrices G(δ) or F(δ) associated with the phase difference δ. The method is explained for the cases of polyoxymethylene and poly-(ethylene glycol).
VLA-4 integrin concentrates at the peripheral supramolecular activation complex of the immune synapse and drives T helper 1 responses
Authors: Mittelbrunn María , Molina Ana , Escribese María M. , Yáñez-Mó María , Escudero Ester , Ursa Ángeles , Tejedor Reyes , Mampaso Francisco , Sánchez-Madrid Francisco
Published: July 2004

The integrin α4β1 (VLA-4) not only mediates the adhesion and transendothelial migration of leukocytes, but also provides costimulatory signals that contribute to the activation of T lymphocytes. However, the behavior of α4β1 during the formation of the immune synapse is currently unknown. Here, we show that α4β1 is recruited to both human and murine antigen-dependent immune synapses, when the antigen-presenting cell is a B lymphocyte or a dendritic cell, colocalizing with LFA-1 at the peripheral supramolecular activation complex. However, when conjugates are formed in the presence of anti-α4 antibodies, VLA-4 colocalizes with the CD3-ζ chain at the center of the synapse. In addition, antibody engagement of α4 integrin promotes polarization toward a T helper 1 (Th1) response in humanin vitromodels of CD4+T cell differentiation and naïve T cell priming by dendritic cells. Thein vivoadministration of anti-α4 integrin antibodies also induces an immune deviation to Th1 response that dampens a Th2-driven autoimmune nephritis in Brown Norway rats. These data reveal a regulatory role of α4 integrins on T lymphocyte-antigen presenting cell cognate immune interactions.
Resistant tissues of modern marchantioid liverworts resemble enigmatic Early Paleozoic microfossils
Authors: Graham Linda E. , Wilcox Lee W. , Cook Martha E. , Gensel Patricia G.
Published: July 2004

Absence of a substantial pretracheophyte fossil record for bryophytes (otherwise predicted by molecular systematics) poses a major problem in our understanding of earliest land-plant structure. In contrast, there exist enigmatic Cambrian–Devonian microfossils (aggregations of tubes or sheets of cells or possibly a combination of both) controversially interpreted as an extinct group of early land plants known as nematophytes. We used an innovative approach to explore these issues: comparison of tube and cell-sheet microfossils with experimentally degraded modern liverworts as analogues of ancient early land plants. Lower epidermal surface tissues, including rhizoids, of
Marchantia polymorpha
and
Conocephalum conicum
were resistant to breakdown after rotting for extended periods or high-temperature acid treatment (acetolysis), suggesting fossilization potential. Cell-sheet and rhizoid remains occurred separately or together depending on the degree of body degradation. Rhizoid break-off at the lower epidermal surface left rimmed pores at the centers of cell rosettes; these were similar in structure, diameter, and distribution to pores characterizing nematophyte cell-sheet microfossils known as
Cosmochlaina
. The range of
Marchantia
rhizoid diameters overlapped that of
Cosmochlaina
pores. Approximately 14% of dry biomass of
Marchantia
vegetative thalli and 40% of gametangiophores was resistant to acetolysis. Pre- and posttreatment cell-wall autofluorescence suggested the presence of phenolic compounds that likely protect lower epidermal tissues from soil microbe attack and provide dimensional stability to gametangiophores. Our results suggest that at least some microfossils identified as nematophytes may be the remains of early marchantioid liverworts similar in some ways to modern
Marchantia
and
Conocephalum
.