bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactions of Free Radicals with Aldehydes. The Reactions of Methyl and t-Butoxy Radicals with Acetaldehyde and Acrolein
Authors: Volman David H. , Brinton Robert K.
Published: January 2005

The reaction in the gas phase of radicals derived from the thermal decomposition of di-t-butyl peroxide with acetaldehyde and acrolein has been studied. The activation energy for H atom abstraction from acetaldehyde by methyl was found to be 7.5±0.3 kcal/mole. The steric factor was about 3.7×10−3, in agreement with many similar reactions. Evidence for chain ending steps other than the recombination of methyl radicals is given. Acrolein polymerizes as well as decomposes in the presence of radicals. The polymerization follows the kinetics to be expected from chain propagation by radical-monomer interaction and chain termination by radical combination. Evidence that the decomposition may be the splitting off of carbon monoxide from the polymerizing chain is presented.
Velocity Distribution of Electrons in Field Emission. Resolution in the Projection Microscope
Authors: Gomer Robert
Published: January 2005

The velocity distribution of electrons in field emission has been calculated on the basis of a simple free electron or one-band model. It is found that the component of velocity transverse to the direction of emission varies approximately as the square root of the applied field. This leads to the result that resolution in the field emission microscope is practically independent of applied voltage, since transit times vary as V−½; resolution turns out to be of the order of 30A. Image formation in the case of molecules and the resolution obtainable with the proton microscope are briefly discussed.
Ultrasonic Propagation in Xenon in the Region of Its Critical Temperature
Authors: Chynoweth A. G. , Schneider W. G.
Published: January 2005

The velocity of ultrasonic waves has been measured in xenon through its critical region. Only the limited frequency range from 250 kc/sec to 1250 kc/sec could be used close to the critical temperature and over this interval a velocity dispersion of as much as 6 percent was observed. The dispersion was accompanied by an abnormally high attenuation of the sound wave confirming in this respect the previously observed behavior of other systems near their critical point. From an analysis of the dispersion measurements it is concluded that structural relaxation processes play a dominant role in the mechanical behavior of the system. The results also indicated the presence of a very wide spectrum of relaxation times.
On the Solution of the Poisson-Boltzmann Equation with Application to the Theory of Thermal Explosions
Authors: Chambré P. L.
Published: January 2005

The theory of thermal explosions originally proposed by Frank-Kamenetzky has been the subject of a number of investigations. The critical condition of inflammability requires the solution of the nonlinear Poisson-Boltzmann differential equation. For the case of a reaction vessel of cylindrical or spherical shape the solution was obtained by previous investigators by numerical integration of the equation. It is shown, however, in the following that the solutions can be obtained in terms of known functions.
Diffusional Processes in the Growth of Aerosol Particles
Authors: Frisch H. L. , Collins F. C.
Published: January 2005

Various theoretical problems encountered in the diffusional growth process of aerosol particles have been investigated. Fick's differential law with a modified boundary condition has been shown to be approximately valid even where the mean free path of the diffusing molecules is long compared to the radius of the aerosol droplet. A new method has been developed for handling the case of a plurality of competing sinks in the diffusion field. The contribution of a time-dependent uniform source function to the flux into the sinks has been calculated by a method which enables account to be taken of the transient in concentration due to the diffusion process. Such a time-dependent source function representing a change in the number of molecules available for diffusion, will arise because of temperature changes in the diffusion field in the aerosol growth problem.
Nuclear Quadrupole Coupling Constants and Molecular Vibrations
Authors: Duchesne Jules
Published: January 2005

The nuclear quadrupole coupling constants may be expected to change with vibrational quantum number. The observations of various workers on some molecules are discussed and the experimental results are interpreted in terms of theory.
Nonequilibrium Thermodynamics of the Sedimentation Potential and Electrophoresis
Authors: de Groot S. R. , Mazur P. , Overbeek J. Th. G.
Published: January 2005

The thermodynamics of irreversible processes is developed for a system placed in a centrifugal field and consisting of a number of components, some of which carry electrical charges. It is found that an Onsager reciprocal relation connects the sedimentation potential with a quantity which we call barycentric electrophoresis (i.e., the quotient of the total mass flow and the electrical field at zero centrifugal field). The latter quantity turns out to be ordinary electrophoresis in a colloid (i.e., in a system of one neutral and a number of charged components, one of which consists of colloidal particles) under certain limiting, but frequently realized, circumstances. If conduction relaxation exists, it appears in both connected phenomena described here.
A Free-Electron Model for π-Molecular Complexes
Authors: Shuler Kurt E.
Published: January 2005

The free-electron model for conjugated molecules is extended to a discussion of molecular complexes formed from conjugated molecules (π-molecular complexes). The forces responsible for complex formation are identified as ``π-delocalization'' forces. The stability and the absorption spectra of these complexes are discussed for a linear, one-dimensional model. The influence of hydrostatic pressure on the position of the complex absorption spectrum is considered, and some predictions are made regarding the resulting shifts of various absorption peaks. The free-electron model is compared with the models suggested by other workers, and good agreement is found in regard to the factors governing the formation and spectra of molecular complexes.
The Intensity of Spectral Lines Produced in Nonhomogeneous Flames
Authors: Kolb Alan C. , Streed E. R.
Published: January 2005

The emission and absorption of radiant energy in a nonhomogeneous flame is discussed. Multiple scattering is neglected and the solution of the basic one-dimensional equation of transfer is obtained in series form. The series is rapidly convergent and a first term approximation yields a simple formula for a flame source having a plane of symmetry which gives satisfactory agreement with experimentally determined nonlinear spectrochemical calibration curves.
Energy Transfer by Collisions in Cis- and Trans-Dichloroethylene Vapors
Authors: Sette D. , Busala A. , Hubbard J. C.
Published: January 2005

Some recent measurements by Sette of ultrasonic absorption in liquid halogenated hydrocarbons have indicated strong structural differences upon which, it was hoped, further light would be given by a study of some of these compounds in the vapor state. Ultrasonic velocity and absorption in cis- and trans-dichloroethylene have been measured at 34.7°C, at frequencies of 0.425, 1.985, and 2.982 Mc sec−1 and at pressures from 12 to 250 mm Hg, giving a range of f/p of 1.27 to 125 Mc/sec atmos. The results show that energy equilibrium in the molecule is more quickly attained in the trans- than in the cis-form. Without consideration of departure from the ideal gas law, the results may be explained by the assumption of two regions of f/p in which relaxation occurs, one relaxation frequency of 3.5 Mc/sec atmos being common to both, there being also one of 30 for the cis and 90 for the trans. The molecular absorption per wavelength computed from dispersion data are in good qualitative agreement with those measured. The values of Cv/R for both forms fall from 7.5 at one Mc/sec atmos to about 3.5 at 100 Mc/sec atmos. The results indicate the pre-eminent importance of short-range forces in determining the energy transfer by collisions.
The Near Ultraviolet Absorption Spectra of 1,4 Bis-(Trifluoromethyl)Benzene and 1,3,5 Tris-(Trifluoromethyl)Benzene
Authors: Cooper C. D. , Noegel F. W.
Published: January 2005

The vapor absorption spectra of 1,4 C6H4(CF3)2 and 1,3,5 C6H3(CF3)3 have been obtained with a Bausch and Lomb Littrow spectrograph. Corresponding solution spectra were obtained with a Beckman DU spectrophotometer. Oscillator strengths f were found to be 12.0×10−3 and 2.1×10−3 for the para di- and tri-substituted compounds, respectively. Both of the vapor spectra are diffuse with the bands of the 1,3,5 compound showing extreme diffuseness. The 0,0 band of the 1,4 bis-(trifluoromethyl)benzene is located at 37460 cm−1. Progressions and combinations involving the upper state frequencies of 210, 770, and 1020 cm−1 are observed. The 210 and 1020 values are correlated with the observed ground state values of 240 and 1070 cm−1, and these are associated with totally symmetric vibrations. The 1,3,5 tris-(trifluoromethyl)benzene spectrum is interpreted as a ``forbidden'' one and the bands at 38670 and 38070 cm−1 are assigned as 0,1 and 1,0 bands, respectively. Rough calculations show the 0,0 band to be shifted about 300 cm−1 toward the violet relative to the benzene spectrum.
The Cut-Off Phenomena of Protein Crystallography
Authors: Booth Andrew D.
Published: January 2005

The well-known paucity of experimentally observed reflections obtained from x-ray studies of protein single crystals, and their tendency to occur in well-marked spherical shells of reciprocal space, are examined quantitatively.

It is shown that, in the case of one protein for which data is available, a simple model with no assumed internal structure gives adequate agreement with experiment.

The addition of simple detail, such as nearest neighbor minimum approach distances, leads to further relations which could be used to produce improved agreement if required.
Infrared Studies of Mixed Crystals: Naphthalene-d8 in Naphthalene
Authors: Person Willis B. , Pimentel George C.
Published: January 2005

Polarized infrared studies in the region 615 to 645 cm−1 have been made using dilute solid solutions of naphthalene-d8 in naphthalene. The ab plane at normal incidence was studied with light polarized either parallel or perpendicular to the b axis. The mole fraction of C10D8 was varied from 0.10 to 0.30. The dichroic splitting of the 632-cm−1 band observed in pure C10D8 decreases with concentration. This is the splitting predicted in the factor group analysis and is attributed to intermolecular coupling. This is a further indication that the magnitude of this splitting in molecular crystals such as C10H8 is only a few cm−1, and that the ``oriented gas'' model is applicable. Using this model, the 632-cm−1 band of C10D8 is assigned as a single fundamental of the B1u or B3u class.
Infrared and Raman Spectra of Fluorinated Ethylenes. V. Hexafluoropropene
Authors: Nielsen J. Rud , Claassen H. H. , Smith D. C.
Published: January 2005

The infrared absorption spectrum of gaseous CF2:CF–CF3 has been obtained in the region from 2 to 38μ, with the aid of LiF, NaCl, KBr, and KRS-5 prisms. The Raman spectrum of both the gaseous and the liquid phase has been photographed with a three-prism glass spectrograph of linear dispersion 15 A/mm at 4358A, and depolarization ratios have been measured for the stronger bands. A complete assignment of fundamental vibrational frequencies is given, although four of the twenty-one fundamentals must be regarded as uncertain. The spectra are interpreted in detail.
A Modified Silberstein Model of Optical Anisotropy
Authors: Matossi Frank
Published: January 2005

The Silberstein model of optical anisotropy is modified by the introduction of screening factors for the fields of the interacting induced dipoles. Thus, it is possible to apply the model consistently to molecular refraction, Rayleigh scattering, Raman effect, dipole moment, infrared intensities, and Kerr effect. The numerical evaluation is carried out for O2, N2, Cl2, CO2, and CS2.
The Excluded Volume Effect in Polymer Chains and the Analogous Random Walk Problem
Authors: Rubin Robert J.
Published: January 2005

An excluded volume random walk is studied in an m-dimensional space. A general expression is obtained for the mean square length of a walk of N steps, 〈RN2〉. It is shown that the increase in 〈RN2〉, δs, resulting from the interaction of only the ith and i+sth steps in the walk is a constant independent of s in two dimensions. In three and four dimensions δs is of the order s−½ and s−1, respectively. Thus, the interaction of the steps is surprisingly large. An estimate is made of the upper bound on 〈RN2〉 caused by the simultaneous interaction of all steps. The result in three dimensions is that in the limit of large N, 〈RN2〉/N is at most of order N½.
Dipole Moments Derived from Force Constants and Ionic Refractions
Authors: Møller Chr. Knakkergaard
Published: January 2005

For simple hydrogen compounds an approximate formula is derived which correlates the dipole moments of the H-bonds with the corresponding stretching force constant, bond length, and ionic refraction—and which contains only a single adjustable parameter.
On the Early Stages of Condensation of Rare-Gas Type Molecules
Authors: Reed Sidney G.
Published: January 2005

The early stages of condensation are treated from the standpoint of the associative equilibrium of single molecules and stable molecular aggregates. Formulas are presented for partition functions from which one can calculate standard chemical potentials and concentrations of specified configurations of up to 8 molecules having a Lennard-Jones (6–12) interaction. Numerical results are given for nitrogen. It appears that nitrogen aggregate concentrations fall steeply with decreasing temperature. Results of this procedure, using a restricted region of phase space, are compared with those obtained with no restrictions for 2 and 3 molecule aggregates.
The Effects of Hydrostatic Pressure on the Ionic Conductivity of AgBr
Authors: Kurnick S. W.
Published: January 2005

Comparison of the conductivities of pure AgBr and AgBr doped with varying concentrations of CdBr2 in the intrinsic temperature range determines the concentration of defects and the mobilities of silver vacancies and interstitial ions. These quantities have been measured as a function of pressure up to 8000 kg/cm2 at three temperatures below 300°C. From the pressure variation of the defect concentration, the molar volume ΔV* of the imperfections is found to be 16 cc/mole below 300°C. An analysis of the pressure variation of the mobilities u0 and u□ of the Ag+ interstitial ions and of the silver vacancies, respectively, indicates that the free volumes associated with their motions are 2.7 cc/mole and 7.4 cc/mole. The value of ΔV*=16 cc/mole is consistent with the Frenkel disorder type. At temperatures above 300°C, however, the observed value of |∂ lnσ/∂p| is larger than expected from a simple Frenkel disorder type. An effort is made to interpret this behavior in terms of mixed Frenkel and Schottky defects.
An Investigation of Certain Solvent Effect in Absorption Spectra
Authors: LeRosen Arthur L. , Reid Charles E.
Published: January 2005

A study of the solvent effects in the spectra of non-ionic compounds to whose structure a zwitter ion form makes appreciable contribution (particularly in the excited state) has revealed three distinct effects:

1. A shift of absorption bands to greater wavelength with increasing refractive index, as predicted by Kundt's rule. This is ascribed to the effect of electronic polarizability on the zwitter ion structure, and is seen unmixed with the other effects only when the solvents are hydrocarbons or aryl halides.

2. A further shift which appears with most solvents other than hydrocarbons and aryl halides, and is ascribed to orientation of molecules of nonuniform polarizability.

3. The Kuhn-Brockmann effect—a large shift which appears whenever hydrogen bonds between the solvent and solute occur. This is believed to be due to the stabilization of the zwitter ion by the electrostatic nature of the hydrogen bond.

No correlations of the spectra of phenolphthalein, p-rosaniline hydrochloride, or iodine with the properties of the solvent were found.
Long-Lifetime Phosphorescence and the Diffusion Process
Authors: Debye P. , Edwards John O.
Published: January 2005

The long-lifetime phosphorescence of certain, easily oxidizable organic compounds in rigid media at the temperature of liquid nitrogen has been found to decay by an inverse power function of the time. Decay kinetics of this type have been observed previously in inorganic phosphors. Employing the diffusion equation and the observed rate law, a distribution function for electrons in the solid media is derived. Data from the experiments are discussed in relation to this theoretical treatment.
The Scattering of Atoms from Diatomic Molecules
Authors: Curtiss Charles F. , Adler F. T.
Published: January 2005

The quantum mechanics of the collision of an atom with a diatomic molecule is discussed. This is an example of the scattering of particles by a nonspherical potential field. In the region in which the atom and molecule are not interacting, the wave function for the system can be written as the product of a wave function for the free atom and that of the free molecule. By an analysis of this function one can write the asymptotic form of the true wave function in the terms of the scattering coefficients, representing the angular dependence of the transition probabilities. In a previous paper, group theoretical arguments were used to separate the rotational coordinates from the n-particle Schroedinger equation. A set of coupled differential equations for the internal wave functions was derived. In the present paper, the scattering coefficients are obtained by an analysis of the solutions of the internal wave equations involving the three coordinates specifying the internal configuration. This set of equations is transformed into a set of coupled ordinary differential equations in which the coupling is the result of the transitions in the state of the molecule. The equations are solved by a perturbation method which is valid in the case of low energy collisions in which transitions occur relatively seldom. The angular transition probabilities are obtained explicitly in terms of integrals of the interaction potential and a set of phase shifts.
The Physical Properties of Molecules in Relation to Their Structure. I. Relations between Additive Molecular Properties in Several Homologous Series
Authors: Bernstein H. J.
Published: January 2005

Relations between the additive physical properties of the substituted methanes, ethanes, ethylenes, benzenes, and the acyclic saturated hydrocarbons have been derived assuming strict additivity for the contributions from nonbonded atoms as well as for the contributions from bonded atoms.
On the Calculation of Electronic Levels in Pyridine and the Isomeric Picolines
Authors: Nordheim Gertrud P. , Sponer H.
Published: January 2005

The molecular orbital method was used for calculating electronic levels in pyridine and the picolines. The change of the benzene Coulomb integrals caused by the nitrogen atom in the ring and the CH3 substitution is treated by introducing into the secular determinant perturbation parameters δk at the appropriate positions. Bonding and antibonding single-electron molecular orbitals are calculated neglecting the overlap integral and electronic repulsion. The average heights are determined for the four one-electron transitions corresponding to the fourfold degenerate level in benzene. By using the assumption that the centers of gravity of the actual singlets are proportional to these average heights, these centers of gravity are predicted for pyridine and the three picolines using two different perturbation parameters δN. The values for pyridine show satisfactory agreement with the experimental mean value 6.14 ev.
Study of X-Ray Induced Optical Absorption Bands in CaF2
Authors: Barile Sam
Published: January 2005

The absorption spectrum of CaF2 crystals containing color centers was investigated as a function of temperature and time elapsed after having been irradiated with x-rays under various conditions. A weak absorption band previously unobserved has been found near 2280A. The intensities of the four absorption bands of crystals irradiated at room temperature decreased to the same extent after having been heated at various temperatures for various time intervals. Irradiation with light at room temperature does not cause any appreciable bleaching. At elevated temperatures the bleaching rate is increased by light. The color of the absorbed light does not however produce any preferential bleaching of any one of the bands. The type of decay and the energies involved were calculated from results obtained by bleaching the crystals at several temperatures. In view of these facts, it would seem that the bands are due to either one type of center, or else to several types incapable of existing independently. The results of the computation of the number of color centers responsible for three of the bands are not incompatible with this point of view.
Comparison of Absorption Spectrum of Uranium Tetrachloride with that of Praseodymium Trichloride and of Uranium Trichloride with that of Neodymium Trichloride
Authors: Sancier Kenneth M. , Freed Simon
Published: January 2005

The absorption spectra of the following substances were taken at 77°K: crystals of anhydrous uranium tetrachloride, praseodymium trichloride, uranium trichloride, neodymium trichloride, uranium tetrafluoride, and a solution of uranium tetrachloride in a solvent consisting of propyl alcohol, propene, and propane.

The spectra of the ``iso-electronic'' ions U+4 and Pr+3 exhibited a match in wave number of the centers of gravity of the separate absorption groups. The correspondence is especially evident between the spectrum of uranium tetrachloride and that of praseodymium chloride. The uranium tetrafluoride furnished a spectrum resembling the chloride but the separations of the absorption regions were not so clear.

These correspondences between U+4 and Pr+3 lead to term assignments for the basic and activated electronic states of U+4 since those of Pr+3 are known. Thus, the two least stable electrons of U+4 in the basic state and to a good approximation in the excited states lies within the 5f shell.

The interaction of the fields of the environment of the ions in the case of U+4 is greater than in the case of Pr+3 and is especially marked in their 1I6 states. The greater interaction is in agreement with the greater effects of different ionic environments on the spectra of U+4, the greater intensity of the ``forbidden'' transitions and other physical properties.

The correlation of the spectra of U+3 and Nd+3 is less distinct even though the same approach may well be valid in view of their similar color. The areas of absorption are not as distinctly separate and may even overlap.

A new method has been developed for obtaining the absorption spectra of very small anisotropic crystals.
Recombination of Methyl Radicals and Atomic Cracking of Ethyl Radicals
Authors: Marcus R. A.
Published: January 2005

The characteristics of this atomic cracking reaction and of the pressure and steric effects associated with the recombination of methyl radicals are all intimately related. The available data on these reactions are correlated by means of a previously developed theory. Some experimental results on the steric factor and the data on the remaining subjects appear to be consistent with the assumption that the methyl radicals must be highly oriented with respect to each other in order that recombination occur. However, experimental steric factors of unity have also been reported in the literature. The corresponding assumption of no orientation leads to disagreement with the remaining data unless some of the rotational degrees of freedom of the ``active'' molecule, in addition to the vibrations, are assumed to be ``active.'' Even then, the difficulties are not completely removed. Further experimental work on these reactions is needed.
Cyanogen Flames and the Dissociation Energy of N2
Authors: Thomas N. , Gaydon A. G. , Brewer L.
Published: January 2005

The behavior of cyanogen flames under a variety of conditions has been observed. Because of the relatively high stability of cyanogen, the behavior is considerably different from that of hydrocarbon flames. Because of the high stability of the combustion products, CO and N2, the flame temperature can reach temperatures above 4800°K. Thus the cyanogen-oxygen flame is the hottest natural flame known.

Spectroscopic observations have been made of both the reaction zone and the mantle of completely combusted gases. Rotational and vibrational temperature measurements using the CN violet system have indicated that the reaction zone is not in thermal equilibrium but that the mantle is in thermal equilibrium. Comparison of the calculated flame temperatures based on different heats of dissociation of N2 with the observed mantle temperatures has fixed DN2=9.764±0.005 ev and DCN=8.2±0.2 ev.
The Infrared Spectrum of Nitrosyl Fluoride. Part I. Prism Spectrum
Authors: Woltz P. J. H. , Jones E. A. , Nielsen A. H.
Published: January 2005

The prism spectrum of NOF is reported from 2–38μ. Twelve absorption bands were observed and identified in terms of the fundamental frequencies ν1(N–O)=1844.03 cm−1, ν2(bending)=521 cm−1, ν1(N–F)=765.85 cm−1. Comparison with the companion molecules NOCl and NOBr is made.
The Infrared Spectrum of Nitrosyl Fluoride. Part II. Rotational Analysis of ν1 and ν3
Authors: Magnuson Dale W.
Published: January 2005

Analysis of the rotational structure of ν1 and ν3 infrared bands of nitrosyl fluoride at 1844.03 and 765.85 cm−1 showed that this molecule is nearly a prolate symmetric top. The following rotational parameters based on symmetric-top theory were found and are expressed in cm−1: for ν1, 2B″=0.7515, 2B′=0.7483, DJ′+DJ″=0.0000275; for ν3, 2B″=0.7521, 2B′=0.7503, DJ′+DJ″=0.00000236. The anharmonic term x33 was found to be −1.06 cm−1 from ν3. The anharmonic term x12 was found to be +1.03 cm−1 from ν1.
The Pyrolysis of n-Propyl-Benzene and the Heat of Formation of Ethyl Radical
Authors: Leigh C. H. , Szwarc M.
Published: January 2005

The investigation of the pyrolysis of n-propyl-benzene by the ``toluene carrier'' technique revealed that this compound decomposes initially into benzyl and ethyl radicals: C6H5·CH2·C2H5→C6H5·CH2·+C2H5.Ethyl radicals decompose rapidly into ethylene and hydrogen atoms. The hydrogen atoms reacting with toluene produce H2 or CH4. The rate of the initial dissociation process can be measured by the rate of formation of C2 hydrocarbons.

It was shown that the decomposition is a homogeneous, first-order gas reaction. The activation energy was estimated at 57.5 kcal/mole, the frequency factor at 3.1012 sec−1. It appears that the activation energy is equal to D(C6H5·CH2–C2H5). Since the heat of formation of benzyl radicals is known, the estimation of D(C6H5·CH2–C2H5) leads to the value for the heat of formation of ethyl radicals, i.e., ΔHf(C2H5)≈22 kcal/mole.The latter value makes it possible to evaluate various relevant bond dissociation energies, i.e., D(C2H5–H) ≈94±4 kcal/mole.
The Structure and Internal Motion of 1,2-Dichloroethane
Authors: Ainsworth J. , Karle J.
Published: January 2005

The structure and internal motion of 1,2-dichloroethane were investigated by means of electron diffraction. Values were obtained for several distances involving hydrogen atoms. In addition, the average amplitude of vibration was found for many of the distances. The predominant isomer was in the trans-form and the less abundant one was in the gauche-positions at 109±5° from the trans-equilibrium position. The amount of gauche-isomer was found to be 27±5 percent at 22°C.
Theory of Resonance Topology of Fully Aromatic Hydrocarbons. I
Authors: Gordon M. , Davison W. H. T.
Published: January 2005

The computation of resonance forms of any specified number of unpaired electrons (``radicality'') of aromatic hydrocarbons is reduced to combinatorial problems, many of which can be solved on the basis of five simple lemmas. In this first of two papers, only unexcited (Kekulé) forms are computed. Algorithms are deduced for deriving the number N of such forms for classes covering practically all nonreticulate aromatic hydrocarbons and a number of singly, doubly, or triply infinite series of reticulate ones. One lemma leads to a simplification of the combinatorial problems from the hexagonal to the square lattice (``dot diagrams''). Points of purely mathematical interest arise and may merit further study.
Polarized Infrared Spectrum of Sodium Nitrite
Authors: Newman Roger
Published: January 2005

The infrared spectra of single crystals of NaNO2 were obtained in polarized light. The polarization behavior of the strong absorptions leads to the following assignment of the nitrite fundamentals ν1 = 1325 cm−1, ν2 = 831 cm−1, and ν3 = 1360 cm−1. Other bands of lower intensity are observed. A combination band (ν1+ν2) at 2670 cm−1 shows a polarization behavior in accord with site group selection rules. An effect is discussed which results from the use of an infrared microscope in the investigation of polarization spectra.
The Molecular Structure of MoF6, WF6, and UF6 from Infrared and Raman Spectra
Authors: Burke T. G. , Smith D. F. , Nielsen A. H.
Published: January 2005

This paper is a report of the complete investigation and interpretation of the Raman and infrared spectra of MoF6, WF6, and UF6. The Raman photographs of MoF6 and WF6 exhibit three intense lines in accord with earlier measurements on UF6 in solution. The exploration of the infrared spectra of MoF6 and WF6 from 2–40μ yielded a great many bands for each molecule. Two of these were quite intense in each case and were identified as fundamentals while the remaining weaker ones were identified as overtones and combinations. The infrared spectrum of UF6 was repeated from 2–17μ with substantially the same results as in the earlier work. Extension of this spectrum from 17–40μ was made and three new bands were discovered.

Because of the great similarity of the spectra of these three molecules, an interpretation of the bands was made along lines suggested by Bigeleisen, Mayer, Stevenson, and Turkevich for UF6, that the molecule belongs to the point group Oh and has totally symmetric octahedral structure. It was possible to fit all but five very weak bands into an identification scheme based on this model. The success of this effort is taken to be conclusive evidence in favor of the Oh type symmetry.
Substituted Methanes. VIII. Vibrational Spectra, Potential Constants, and Calculated Thermodynamic Properties for Dibromodichloromethane
Authors: Davis Abram , Cleveland Forrest F. , Meister Arnold G.
Published: January 2005

Raman displacements, semiquantitative relative intensities, and quantitative depolarization factors for the liquid, and infrared absorption wave numbers and percent transmission curves for both the liquid and the gas, have been obtained for CBr2Cl2. The present and previous data were critically examined and probable values of the wave numbers corresponding to the fundamental vibrational frequencies were determined. Assignments were made for all observed Raman and infrared bands. As a check on the assignments, a normal coordinate treatment was undertaken, using a potential function containing all possible quadratic interaction constants. A reasonable set of potential constants was obtained. The observed fundamentals then were used to calculate to a rigid rotator, harmonic oscillator approximation the heat content, free energy, entropy, and heat capacity for 12 temperatures from 100° to 1000°K, for the ideal gaseous state at 1-atmos pressure.
Thermal Conductivity of Fluid Argon and Nitrogen
Authors: Uhlir Arthur
Published: January 2005

The thermal conductivities of A and N2 have been measured at pressures up to twice the critical pressures and at temperatures from the normal boiling points to well above the critical temperatures. By combining Enskog's transport theory for a dense gas of hard elastic spheres with free volume calculations for a close-packed lattice (assuming a communal entropy of R per mole), one can calculate the thermal conductivity λ for liquid A between 87.3°K and 141.6°K from liquid and vapor densities and entropy of vaporization. The values so calculated are within 15 percent of the measured values. However, a similarly calculated value of the viscosity is 50 percent lower than the experimental value. A correction for quantum-mechanical effects reduces the disagreement between the theoretical and experimental values of λ to about ±5 percent, which is within the uncertainty of the thermodynamic data.
Infrared and Raman Spectra of Fluorinated Ethanes. III. The Series CH3–CF3, CH3–CF2Cl, CH3–CFCl2, and CH3–CCl3
Authors: Smith D. C. , Brown George M. , Nielsen J. Rud , Smith Raymond M. , Liang C. Y.
Published: January 2005

New infrared spectra have been obtained for gaseous CH3–CF3 in the region 20–38μ, and in the region 2–38μ for gaseous CH3–CF2Cl and CH3–CFCl2, and CH3–CCl3 vapor and liquid, by use of LiF, NaCl, KBr, and KRS−5 optics. Raman spectra of gaseous and liquid CH3–CF2Cl and of CH3–CFCl2 and CH3–CCl3 in the liquid state have been obtained with a three-prism glass spectrograph of linear dispersion 15A/mm at 4358A. Depolarization ratios were obtained for all of the stronger Raman bands of the liquids.

The spectra are interpreted, a complete assignment of fundamental frequencies is proposed for each molecule, and thermodynamic functions are calculated for the temperature range 298–600°K and at the boiling point.
The Use of Isotopic Molecules for the Complete Determination of Force Constants. I. Linear Molecules
Authors: Decius J. C.
Published: January 2005

Equations are developed which show the maximum amount of information which can be obtained concerning the force constants with isotopic linear molecules. It is demonstrated that a unique solution can be found in terms of the expressions Σkλk, Σkλk2, and Σkλk3, where λk=4π2νk2, provided the νk are known for the ``unsubstituted'' molecule and for certain isotopic molecules involving respectively single, double, and triple substitutions; i.e., if ABCD··· is the unsubstituted molecule, isotopic molecules of the types A*BCD···, AB*CD···, etc., A*B*CD···, etc., and A*B*C*D···, etc., are required. More than two isotopic forms (such as A and A*) of any given atom are not required.

For the triatomic molecule, only the singly substituted forms are required (this is also true for the perpendicular vibrations of the tetratomic molecule). It is also found that the force constants of the symmetrical linear molecule may be found using only symmetrical isotopic molecules; the number of these required is naturally less than the number required for an unsymmetrical molecule having the same number of atoms.
The Molecular Structure of 1,2-Dichloropropane
Authors: Wood William W. , Schomaker Verner
Published: January 2005

Under the assumption of V([open phi])=V0[1—cos([open phi]—[open phi]0)]/2 for the potential hindering internal rotation, visual interpretation of the electron-diffraction pattern leads to the results (best values and estimated limits of error): C–Cl, 1.79±0.035A; C···Cl, 2.715±0.025A; C–C, 1.56A (range: 1.49–1.60A); ∠C–C–Cl, 108±4°; |[open phi]0| ≤30° (i.e., essentially trans in the chlorine atoms), with a small positive value of [open phi]0 (increasing CH3···Clprimary) most likely; V0≥4 kcal/mole. The best value for V0 ranges from 10 kcal/mole for [open phi]0=0° to 30–40 kcal/mole for [open phi]0=25°. The diffraction pattern is almost indifferently compatible with fractions ranging up to 50 percent of a skew-isomer with [open phi]0∼120° and a sufficiently low value of V0, but consideration of dipole moment data provides some further evidence on its structure while showing the fraction present to be about 20 percent with an upper limit of about 30 percent.
The Viscosity of Concentrated Suspensions and Solutions
Authors: Brinkman H. C.
Published: January 2005

An expression for the viscosity of solutions and suspensions of finite concentration is derived by considering the effect of the addition of one solute-molecule to an existing solution, which is considered as a continuous medium.
Kinetics of the Decomposition of Diethyl Peroxide
Authors: Rebbert Richard E. , Laidler Keith J.
Published: January 2005

The kinetics of the gas-phase decomposition of diethyl peroxide have been studied in a flow system, using excess of toluene. The main reaction products were found to be ethane and formaldehyde, and there were smaller amounts of methane and dibenzyl. The frequency factor of the reaction is 2.1×1013, and the activation energy is 31.7 kcal per mole. The mechanism of the reaction is discussed, and it is shown that the measured rate must refer to the initial dissociation C2H5OOC2H5→2C2H5O. With a new value of 47.8 kcal for the heat of formation of gaseous diethyl peroxide, the heat of formation of the C2H5O radical is calculated to be 8.1 kcal, which agrees satisfactorily with estimates from other kinetic data. Thermochemical values for other reactions involving this radical are calculated.
The Reaction of Methyl Radicals with Some Halogenated Methanes
Authors: Raal F. A. , Steacie E. W. R.
Published: January 2005

The reactions of methyl radicals formed by the photolysis of acetone with several halogenated methanes have been investigated between 110°C and 220°C. The activation energies of these reactions have been determined relative to the activation energy of the combination of methyl radicals and are found to be (in kcal): methyl fluoride 8.7, methylene fluoride 6.2, methyl chloride 9.4, methylene chloride 7.2, chloroform 5.8, methyl bromide 10.1, methylene bromide 8.7. The steric factors of the reactions are in the range 10−2−10−4.
The Reaction of Methyl Radicals with Nitric Oxide, and the Rate of Combination of Methyl Radicals
Authors: Durham R. W. , Steacie E. W. R.
Published: January 2005

Radioactive tellurium mirrors have been used to investigate the rate of reaction of methyl radicals with nitric oxide in a flow system. The collision efficiency of this reaction has been found to be 1.5×10−4, which is higher by a factor of 10 than the previous value obtained by Forsyth. This value when applied to results obtained by Miller and Steacie for the ratio of the two reactions CH3+CH3→C2H6,CH3+NO→products,leads to a collision efficiency or steric factor, assuming the activation energy to be zero, of 0.01 for methyl combination. A comparison of this value with those obtained by other authors from photochemical studies suggests the value for the collision efficiency of methyl combination is between 0.5 and 0.05.
Microwave Spectra and Molecular Structures of Fluoroform, Chloroform, and Methyl Chloroform
Authors: Ghosh S. N. , Trambarulo Ralph , Gordy Walter
Published: January 2005

Sufficient isotopic combinations have been studied to make complete structural determinations of fluoroform and chloroform from microwave rotational spectra. The dimensions of CHF3 are dCH = 1.098A, dCF = 1.332A, and ∠FCF = 108°48′; those of CHCl3 are dCH = 1.073A, dCCl = 1.767A, and ∠ClCCl = 110°24′. Measurements were made on only the most abundant isotopic species of CH3CCl3. If the CCl3 configuration as in chloroform and the CH3 configuration as in methane are assumed, the CC distance in CH3CCl3 is found to be 1.55A.
Interchange of Fission-Product Bromine with Carrier Bromine
Authors: Stehney Andrew F. , Sugarman Nathan
Published: January 2005

Experiments on the interchange of the fission products 2.4-hr Br83 and 55.6-sec Br87 with carrier bromine have been performed. Essentially the same degree of interchange is effected by the following chemical procedures: carrier added as BrO3− and reduced by H2S, carrier added as BrO3− and reduced by excess carrier Br−, and carrier added as Br− to HCl and irradiated uranium metal dissolved.
Statistical Mechanics of Rubber
Authors: Boggs F. W.
Published: January 2005

It is shown in this paper that above the second-order transition the partition function of a rubber can be represented to a reasonably good approximation by the product of the partition function of a liquid formed of molecules similar to the chain elements and the partition function of the noninteracting chains divided by the partition function of a perfect gas. In terms of the free energy this means that the free energy of rubber will be equal to the sum of the free energy of the chain network without interactions and that of a liquid formed of the chain elements alone minus the free energy of a perfect gas having the same number of molecules as the rubber has chain elements.

This same procedure has permitted the calculation of the free energy and partial pressure of a rubber solution. This is, however, by no means the only possible application. All the thermodynamic properties of elastomer solvent systems can be obtained.

This is a generalization of the methods previously used in the statistical studies of rubber and rubber solvent mixtures.
The Influence of First-Order Rotational Resonance Interaction on Certain Bands in the Infrared Spectrum of the Allene Molecule
Authors: de Heer J.
Published: January 2005

The Coriolis coupling between two degenerate vibrations in allene has been discussed. This theoretical treatment gives a satisfactory explanation of the main features of two perpendicular bands, which have been observed in the infrared absorption spectrum of this molecule between 8 and 14μ. An analysis of the nuclear spin statistics has been carried out in order to account for the intensity alternations and to help in identifying the Q branches. A derivation of the frequency formula has been given on the basis of ordinary first-order perturbation theory. Some emphasis is laid on the ambiguity in notation and the relation of this formula to others, reported in the literature. After making some reasonable assumptions with regard to the geometry of the molecule, we have obtained numerical values for the band centers and the various Coriolis coupling coefficients. A tentative suggestion has been made in partial explanation for the appearance of satellites between the main Q branches in the spectrum.
The Measurement of Bond Moments and Derivatives in HCN and DCN from Infrared Intensities
Authors: Hyde G. E. , Hornig D. F.
Published: January 2005

The absolute infrared absorption intensities of the fundamental vibrations of HCN and DCN have been measured, using the pressure broadening technique. These measurements yield the bond moments μC–H=±1.13d, μC≡N=±1.80d and show that if C is positive in the C≡N dipole, H is positive in the C–H dipole. The change in moment with internuclear distance is found to be ∂μ/∂rC–H=±1.05d/A, ∂μ/∂rC≡N=∓0.66d/A. Two of the three anomalous peaks in the band ν1 of HCN are shown to arise from the dimer of HCN.
The Azomethane Induced Oxidation of Propane
Authors: Scheer Milton D. , Taylor H. Austin
Published: January 2005

The effect of methyl radicals from the photolysis of azomethane on propane-oxygen mixtures in Pyrex vessels has been shown to include a slow oxidation in the temperature range 35° to 200°C and cool flames at 250°C. Azomethane decomposed thermally induces cool flames in propane-oxygen mixtures at 255° and 270°C, temperatures below those at which cool flames occur in the system propane-oxygen alone. A rapid photo-oxidation has been observed in a quartz vessel in the temperature range 230 to 250°C.
On the Decomposition of Metallic Azides
Authors: Thomas J. G. N. , Tompkins F. C.
Published: January 2005

The mechanisms suggested previously for the formation and growth of nuclei in the decomposition of barium azide have been examined in detail. It is concluded that these cannot adequately account for the experimental results available on the thermal decomposition, and photo and ionic conductivity of this salt.
Flow Birefringence in Polydisperse Systems of Rod-Like Molecules Having a Montroll-Simha Distribution
Authors: Goldstein Martin
Published: January 2005

Values of the quantities measured in flow birefringence experiments (extinction angle χ and optical factor F) are calculated for polydisperse systems of rigid rod-like molecules, where the polydispersity is assumed to arise from random degradation of a system of molecules all having the same initial length. The recent calculations of Scheraga, Edsall, and Gadd, and the distribution function of Montroll and Simha are used. A number of simplifying assumptions are made, and their effect on the results is discussed.
The Microwave Spectrum of Ketene
Authors: Johnson H. R. , Strandberg M. W. P.
Published: January 2005

The microwave absorption spectra of the ketene molecules H21C212O16, H1D2C212O16, and D22C212O16 have been investigated. Reciprocal moments of inertia have been determined for each from the measurements. The centrifugal distortion theory of Hillger and Strandberg has been found valid for both Q and R branches. The structure has been calculated and dipole moment measured; results check and extend the accuracy of values previously determined by other methods. Intensities of satellites of the lightest molecule corresponding to the lowest three vibrational fundamentals have also been measured and changes in the average reciprocal moments determined. The vibrational frequencies have been calculated and found different from values reported in the literature by infrared workers. References and suggestions for further work are given.
The Heat Capacities of Uranium, Uranium Trioxide, and Uranium Dioxide from 15°K to 300°K
Authors: Jones W. M. , Gordon Joseph , Long E. A.
Published: January 2005

Heat capacity measurements have been made over the temperature range 15–300°K for uranium metal, uranium trioxide, and uranium dioxide. A maximum was observed at 28.7°K in the heat capacity curve of UO2 which is probably the result of the changing population of the magnetic quadrivalent uranium ions among their available energy states. The entropies of these substances at 298.16°K are 12.03, 23.57, and 18.63 cal deg−1 mole−1, respectively. The free energies of formation of UO3 and UO2 are −273.1±3 and −246.6±0.6 kcal mole−1, respectively.
A Single Crystal Neutron Diffraction Determination of the Hydrogen Position in Potassium Bifluoride
Authors: Peterson S. W. , Levy Henri A.
Published: January 2005

Neutron diffraction measurements on KHF2 single crystals show that the hydrogen atom occupies the central position, within 0.1A, in the linear F–H–F ion. The data also indicate asymmetry in thermal motion, which suggests that the bifluoride ion undergoes rotatory oscillation with appreciable amplitude. The study demonstrates the usefulness of single crystal neutron diffraction data for crystal structure determination.