bluuebunny/crossref_metadata_2025 huggingface dataset:
40-kV Electron Scattering from Ne, Ar, Kr, and Xe Measured by the Sector-Microphotometer Electron-Diffraction Method
Authors: Bonham R. A. , Cox H. L.
Published: January 2005

Experimental differential cross sections for 40-kV electrons scattered by Ne, Ar, Kr, and Xe were measured using the gas electron-diffraction sector-microphotometer method. Three different camera distances (11, 28, and 62 cm) were used to collect experimental intensity data over a range of the scattering variable s from s=0.9 to s=26.

The experimental-intensity curves were compared with theoretical-intensity curves where the elastic portion of the scattered intensity was calculated using both partial-wave and first Börn scattering amplitudes. Hartree—Fock inelastic scattering factors calculated by Tavard were used for the inelastic portion of the scattered intensity, as well as inelastic scattering factors calculated using the plane-wave approximation suggested by Liberman. In the case of Kr and Xe the agreement between the experimental and theoretical intensity curves was better when the partial-wave amplitudes were incorporated in the elastic portion of the intensity than when the first Börn amplitudes were used. In the case of Ne and Ar, the difference in the agreement using partial-wave and first Börn amplitudes was too small to be significant. The total electronic energies for the atoms studied were also estimated.
Local Electric Fields and the Paramagnetic Resonance of Charge-Compensated Sites in (Ca, Ce)WO4
Authors: Mims W. B. , Gillen R.
Published: January 2005

Nonaxial paramagnetic resonance spectra in Ce-doped CaWO4, with and without sodium compensation, have been observed and the g parameters measured. It is suggested that the compensation-site g ellipsoids can be largely explained as a perturbation of the axial-site g ellipsoid caused by the odd fields of the compensating charges. According to this model the compensation-site g parameters can be predicted by making measurements of the linear g shifts in laboratory applied fields for the axial sites. The model is illustrated by some simple comparisons between experimental g ellipsoids, and g ellipsoids predicted in this way. Electric-field shifts have also been measured for the compensation-site spectra. Similarities between the compensation-site shifts and the shifts measured for axial sites afford some evidence in support of the primary assumption that the strong odd fields arising from the compensating charges can be treated as axial site perturbations. The compensation-site shifts can also be used to make partial corrections for quadratic and other higher-order odd-field effects which were ignored in the sample description of the model. Predictions made for the g ellipsoids due to charge compensation at the nearest-neighbor Ca site agree reasonably well with the strongest nonaxial spectra observed in the uncompensated (vacancy compensated) and in the Na-compensated samples. This shows that the local strains, and the even fields due to the compensating charges are of only secondary importance in this system. The local odd fields were estimated by using the bulk dielectric constants of CaWO4. The success of this procedure in predicting g values for the strongest nonaxial spectra in the two samples suggests that compensating charges at a nearest-neighbor site produce changes in the dielectric similar to those produced by macroscopic electric fields. The g parameters and electric-field shifts for a second, less intense nonaxial spectrum in the vacancy-compensated sample were also studied. The results were not so easy to interpret in this case. Miscellaneous observations were also made on some weaker lines in the two samples.
Vapor—Solid Interactions and the Effusion Oven. I. The Total Effusion Current through a Cylindrical Orifice
Authors: Winterbottom W. L.
Published: January 2005

Until recently, all treatments of molecular flow in and from an effusion cell have been based upon the ``diffuse reflection'' vapor—solid collision model of Clausing. Winterbottom and Hirth have pointed out the inadequacy of a collision process that assumes the diffuse emission of an impingent vapor molecule from the point of its incidence and have treated the oven with a more realistic collision process that assumes the adsorption of the vapor molecule following a surface collision. The treatment presented here modifies the model developed by Winterbottom and Hirth to include the influence of the mobility of the adpopulation on the inside walls of the oven. The results of the analysis of the total effusion current from a cylindrical orifice agree qualitatively with those of the earlier treatment in predicting an appreciable surface-diffusion contribution for certain orifice geometries when the vapor—solid interactions are typical of chemisorption. Quantitatively, however, the analysis deviates significantly from the earlier predictions and indicates the necessity of considering the adpopulation on the walls within the cell. Numerical solutions for the total effusion current under steady-state conditions are presented and compared with the predictions of earlier models and with some recent effusion measurements. New definitions for the Clausing transmission probability and an effusion coefficient are presented to remove the ambiguities that exist in the older versions for the model of effusion considered here. The results show that the Clausing model, where there is a zero time of stay in the adsorbed state, is just a limiting case of the more general model considered in which the effusion current and its spatial distribution are material-, pressure-, and geometry-dependent.
Correlation Effects in Complex Spectra. II. Transition Probabilities for the Magnesium Isoelectronic Sequence
Authors: Zare Richard N.
Published: January 2005

Absolute multiplet strengths have been calculated for electric dipole transitions involving the ground state and/or several lower-lying excited-state configurations of Mg I, Al II, Si III, P IV and Ca IX. Configuration mixing is taken into account by using linear combinations of Hartree—Fock—Slater (HFS) determinantal wavefunctions. Dipole length and dipole velocity expressions for the transition probability are evaluated, and in most cases these alternative formulations agree to within 25% of each other. Three modifications of the ``universal'' exchange potential used in the HFS self-consistent field method are investigated, and the differences in the calculated transition probabilities are found to be quite small, with perhaps a slight preference for the variational adjustment proposed by Lindgren. Calculated absolute multiplet strengths are compared with the available experimental measurements, and with other calculations.
Molecular-Weight Dependence of Viscoelastic Properties of Polystyrene Solutions
Authors: Thurston George B.
Published: January 2005

Experimental data are analyzed to determine the molecular-weight dependence of viscosity and oscillatory flow birefringence of polystyrene solutions in a partially chlorinated diphenyl solvent. Results for polystyrenes in the molecular weight range from 104 to 106 are given for the steady-flow intrinsic viscosity, the high- and low-frequency limits of the complex coefficient of viscosity for oscillatory flow, and the frequency dependence of the oscillatory flow birefringence. These properties are compared with the results of the theory for the flexible noninteracting Gaussian chain model composed of a finite number of chain segments and including hydrodynamic interaction within the chain as well as internal viscosity. The intrinsic viscosity is independent of the internal viscosity while the viscosity and birefringence in oscillatory flow are dependent on all factors. The three experimental properties are sufficient to determine the values of the parameters of the theory after correction for finite concentration effects. Over the complete molecular weight range studied it is found that approximately the number of monomer units per segment of the model is 10, the length of the segment is 3.0×10−7 cm, the ratio of the internal viscosity coefficient to segmental friction factor is 2.0, and the segmental hydrodynamic interaction factor is 0.3. The character of the measured properties and the theoretical results are in agreement.
ESR Study of the Photolysis of CF3OF and CF3OOCF3 at Low Temperature: The CF3OO· Radical in Solution
Authors: Vanderkooi N. , Fox W. B.
Published: January 2005

An ESR study of solutions of CF3OF and CF3OOCF3 at −196° to −170° following ultraviolet irradiation provided evidence that the predominant radical produced in each case is the trifluoromethylperoxy radical CF3OO· in which the fluorine atoms are rendered nonequivalent by hindered rotation of the trifluoromethyl group in the nonlinear C–O–O skeleton.
Infrared Spectra of the Hydrogen-Bonded Carboxylic Acids
Authors: Witkowski Andrzej
Published: January 2005

The condition of separability of different vibrational modes in dimers of carboxylic acids is analyzed. In the excited vibrational state the OH stretching modes are intrinsically coupled with the hydrogen-bond vibrations and can be separated only in limiting cases. The physical nature of this coupling is studied and for a simplified model of carboxylic acid dimer the fundamental Hamiltonian describing this coupling is derived. The formulas for the bandwidth, center of gravity, and total intensity of the infrared absorbtion spectrum are obtained.
Theory of the Ultraviolet Absorption Spectrum of Diphenyl
Authors: London Albert
Published: January 2005

The lower excited energy levels of the molecule diphenyl are calculated by the method of antisymmetrized products of molecular orbitals. The wave functions for diphenyl are constructed from linear combinations of benzene molecular orbitals and the perturbation of the original energy levels of benzene caused by the presence of the second benzene ring in diphenyl is computed. The theory predicts the splitting of the two non-degenerate singlet levels and the one degenerate singlet level of benzene into eight levels, four of which give allowed electronic transitions to the ground state and four of which do not. Experimentally three strong structureless bands are observed, one between λ = 2200A and λ = 2800A, one at about λ = 1900A, and one below λ = 1700A. The calculated spectrum has allowed transitions at about 2400A, 1900A, 1500A, and 1400A, and thus is in good agreement with the experimental observations.
The Effect of Thorium Chloride on the Potential at the Interface between Vitreous Silica and Solutions of Potassium Chloride
Authors: Wood Lloyd A.
Published: January 2005

The effect of the presence of 10−6 M thorium chloride on the zeta-potential at the interface between vitreous silica and three solutions of potassium chloride has been determined by the streaming potential method. This trace of thorium changed the zeta-potential, which was strongly negative with the same solutions without added thorium, to positive values of smaller magnitude. The theory of Langmuir by which can be calculated the thickness of the wetting film owing to the zeta-potential has been extended to apply to these 4–1, 1–1 electrolyte mixtures, and the effect of this wetting film on the capillary rise of these same solutions has been studied. With only one solution (10−5 M KCl) containing added thorium was the zeta-potential low enough so that the wetting film was negligible in the capillarimeter of Jones and Ray.
Determination of Free Radicals in Acetone Photolysis
Authors: Feldman Milton H. , Burton Milton , Ricci John E. , Davis Thomas W.
Published: January 2005

Acetone has been photolyzed in a flow system at several temperatures in the pressure range 0.5 to 11 mm with exciting radiation of wave-length 2650–2900A and 2537A. The free methyl radicals formed in the decomposition have been determined as lead tetramethyl. Approximately one methyl radical is formed for every four molecules of carbon monoxide, the actual proportion depending on temperature and pressure. Relatively more free radicals are formed at 100°C than at lower temperatures and more are formed at lower pressure than at high. A process involving the existence of a long lived metastable state for photoactivated acetone has been suggested to explain the results. The proposed scheme is found consistent with most of the published work on acetone photolysis.
Effect of Pressure on the Melting of Crystalline Rubber
Authors: Wood Lawrence A. , Bekkedahl Norman , Gibson Ralph E.
Published: January 2005

The temperature of melting of a sample of stark rubber has been found to increase from about 36° to 70°C as the pressure is raised from 1 to 1170 bars.
Free Volume and Entropy in Condensed Systems I. General Principles. Fluctuation Entropy and Free Volume in Some Monatomic Crystals
Authors: Frank Henry S.
Published: January 2005

In a system of atoms whose motions are classically excited, the change in entropy in any isothermal process can be written R ln (Vf2/Vf1) per mole, one such term for each kind of atom in the system. The free volume Vf used in this expression is the effective volume accessible to the centers of gravity of the atoms, corrected for fluctuation effects. Corresponding expressions can be written for the classical (translational or rotational) part of the motions of polyatomic molecules in real liquids and solids. In solids the free volume can be written Vf = Nvf, where v is a box, or cage, volume accessible to one particle, and f, the fluctuation factor, has a numerical value which depends on the way in which the box is defined. R ln f is a contribution to the entropy of the system, and the name ``fluctuation entropy'' is proposed for it. The fluctuation entropy includes what has been called ``communal entropy'' as well as a term due to the temperature variability of cell sizes. The free volume in a monatomic crystal can be determined from thermodynamic data, one convenient relationship being Pvap = (RT/Vf) exp (— ΔH/RT). When this is applied to the data for the vapor pressures of the solids A, Kr, Xe, Mg, Zn, Cd, Hg, values of Vf are obtained which are about ½ percent of the volumes of the solids. The values of f found for these crystals support Rice's view that solids should display a rather large fluctuation entropy.
Free Volume and Entropy in Condensed Systems II. Entropy of Vaporization in Liquids and the Pictorial Theory of the Liquid State
Authors: Frank Henry S.
Published: January 2005

The results of the first paper of this series, and a generalization of a method due to Eyring, are used to obtain an expression for the free volume of a liquid, Vf=fb3g3/h3n3×[RT/ΔEv]3, and an equation for the entropy of vaporization. ΔS=R[ln Vg−lnVl−ln β+3lnβ+3ln(ΔH/RT−1)]. Here β=γfb3g3/h3n3, where γ measures the interference in the liquid with the internal motions (rotations, vibrations) of the molecule, and f, b, g, h, n are quantities which depend on the geometry of the liquid and the energetic and dynamic interaction of the molecules. The rule of Barclay and Butler, that the 25°C value of ΔS for various pure liquids has a rough linear relationship to the corresponding ΔH of vaporization, is shown to imply a general tendency for a liquid to have a smaller β the larger its ΔH of vaporization. In many cases this means a smaller γ, resulting from increased interference with rotation of the molecules in the liquid. Pitzer's perfect liquid has a value β = 16, sensibly independent of ΔH. This is taken to mean that in such a liquid as benzene or carbon tetrachloride (β≈6) the interference with free rotation is considerable. For CS2 there is evidence that the intermolecular force field differs from ``normal,'' and the difference in potential function between liquid metals and normal liquids shows up strongly. Accepting the value β = 16 found for the ideal liquid as a norm, it is proposed to call R ln (16/β) for any liquid the hypothetical entropy defect (HED) and interpret it as the amount by which the entropy of the liquid (referred to the same substance as a perfect gas) is less than that of the ideal liquid in the ``corresponding'' state.
Thermodynamic Properties of Ethylbenzene Vapor from 300° to 1500°K
Authors: Brickwedde F. G. , Moskow M. , Scott R. B.
Published: January 2005

In this paper are presented tables of the more important thermodynamic functions of ethylbenzene in the ideal gas state from 300° to 1500°K. These functions were calculated using spectroscopic, structural, and calorimetric data. Six investigations of the Raman spectrum of ethylbenzene and three of the infra-red absorption spectrum were available for an assignment of frequencies to the intramolecular vibrations. Included in the paper is a calculation from calorimetric data of the enthalpy and entropy of saturated vapor at 294°K relative to the solid at 0°K. This paper completes a report on a determination of the thermodynamic properties of ethylbenzene covering the solid, liquid, and vapor phases, extending from 0° to 1500°K. All the experimental results are presented in detail in preceding papers.
The Reaction of Hydrogen Atoms with Acetone
Authors: Harris G. M. , Steacie E. W. R.
Published: January 2005

The reaction of hydrogen atoms with acetone vapor has been investigated by means of the Wood-Bonhoeffer technique at room temperature. The sole reaction products under these conditions are methane and carbon monoxide. A deuterium exchange experiment showed that the methane product is almost completely deuterized, while undecomposed acetone is exchanged to the extent of 4.1 atom percent. A reaction series has been devised which satisfactorily explains the experimental facts. The activation energy of 9 kcal. found for the over-all process has been assigned to the proposed initiatory step: H+CH3COCH3→H2+CH3COCH2.
The Reaction of Hydrogen Atoms with Dimethyl Mercury
Authors: Harris G. M. , Steacie E. W. R.
Published: January 2005

The Wood-Bonhoeffer method has been applied to a study of the reaction of hydrogen atoms with dimethyl mercury. The organometallic undergoes rapid decomposition at room temperature, giving as products methane, ethane, and metallic mercury. The variation of the ratio of methane to ethane formation with change in the relative concentrations of reactants has been satisfactorily explained on the basis of a postulated reaction mechanism, all steps in which are assumed to have an activation energy ≤6 kcal.
The Mercury Photosensitized Reactions of Propane at Low Pressures
Authors: Darwent B. deB. , Steacie E. W. R.
Published: January 2005

The mercury photosensitized reactions of propane have been investigated at room temperature between 0.7 and 84.5 mm Hg. At high pressures the products consisted almost entirely of hexane and hydrogen but at low pressures methane and C2 and C4 hydrocarbons were produced in increasing amounts. The production of methane was much less than in the similar reactions of ethane. The effect of pressure on the nature of the reaction can be accounted for by a C–H split followed by atomic cracking and recombination reactions as proposed by Steacie and Dewar, but the difference in the products from propane and ethane make it likely that the reaction proceeds, at least in part, by the formation of an active molecule. At low pressures the rate of propane disappearance is retarded and the extent of C–C split increased by the addition of hydrogen. The effect of added hydrogen is explained by an increase in the rates of recombination of hydrogen atoms and of atomic cracking reactions.
Molecular Constants and Chemical Theories V. Some Remarks on Physical Constants and Theories of Higher Valence States
Authors: Samuel R.
Published: January 2005

In answer to a recent article of Dr. Wheland, criticizing the previous papers of this series, some points of theoretical and experimental evidence are discussed. The criticism of the above paper is rejected in full (with the exception of a minor point on the calculation of ionic percentage contributions from bond moments). This article goes slightly beyond the previous ones in a number of points. Attention may be drawn to two of them. The question why different values of molecular constants are produced by the process of sharing or by a change of valency is discussed in greater detail. Furthermore, while maintaining that individual constants cannot distinguish between different structures or theories, it is shown that they can do so in conjunction. Indeed in conjunction they offer definite experimental evidence which supports the classical concepts but is not compatible with the semipolar double bond and its translation into resonance structures.
Hydrogen Overvoltage in Concentrated Sulfuric and Phosphoric Acid Solutions
Authors: de Béthune André J. , Kimball George E.
Published: January 2005

The overvoltage for the discharge of hydrogen on a mercury cathode has been measured at 25°C in sulfuric acid solutions in the concentration range 0.125 to 9.65 molar. In dilute solution, the overvoltage is independent of the acid concentration, the cathode reaction being the discharge of a proton from water. At concentrations in excess of 2.83 molar, the overvoltage decreases approximately as a linear function of the weight percentage. Evidence is presented to show that in this region, the cathode reaction involves the hydrogen sulfate molecule, H2SO4. Preliminary results on phosphoric acid solutions also show a drop in the overvoltage as the concentration is increased beyond 1 molar.
Amphipathic Character of Proteins and Certain Lyophile Colloids as Indicated by Absorption Spectra of Dyes
Authors: Sheppard S. E. , Geddes A. L.
Published: January 2005

A characteristic change of spectral absorption of certain dyes as between water and organic solvents is shown to appear in aqueous solutions of gelatin or of the colloidal detergent, cetyl pyridinium chloride. This behavior is attributed to a bilateral character of lamellar micelles of such bodies, the elementary lamellae being polar and hydrophile on one side, non-polar and organophile on the reverse side. The possibility is indicated of diagnosing such amphipathic characteristics by comparative spectrophotometric measurements with suitable dyes.
The Fluorescence of Diethyl Pseudo-Isocyanine Chloride in Solution
Authors: Hutten E. Hirschlaff , Pringsheim Peter
Published: January 2005

The fluorescence and absorption spectra of the dye diethyl pseudo-isocyanine chloride in various solid solutions and at several concentrations and temperatures have been obtained by means of a spectrograph of high dispersion. It has been shown that the dye is fluorescent not only in the polymerized state but also when it is embedded in a ``rigid'' medium.
On the Fluorescence Spectra of Naphthacene in Solid Solution of Anthracene for Different Exciting Wave-Lengths
Authors: Ganguly S. C.
Published: January 2005

The fluorescence of green anthracene crystal (naphthacene in solid solution of anthracene) has been studied with exciting light of different wave-lengths and the long wave-length limit for excitation has been found. From the study of the fluorescence and absorption spectra an attempt has been made to interpret the mechanism of the fluorescence phenomenon in this crystal.
The Thermal Expansion and Compressibility of a Three-Dimensional System of Harmonic Oscillators
Authors: Matsen F. A. , Walkey John E.
Published: January 2005

Thermal expansions and compressibilities are calculated from equations of state of the Grüneisen form which are derived from a general partition function. The non-thermal energy and frequency are obtained as functions of volume, the constants in these functions being evaluated from data on the second virial coefficients of gases. Data of state are calculated for three types of thermal energy distributions, the classical, the Einstein, and the Debye. A limitation on the harmonic oscillator approximation is discussed as is the quantal effect in the law of corresponding states.
The Calculation of the Contribution of Freely Rotating Groups to Electron Scattering by Gases
Authors: Karle J.
Published: January 2005

The contribution from freely rotating atoms to the intensity of electron scattering by gaseous molecules is obtained by means of an asymptotic evaluation of an integral, using the saddle point method. It is possible now to estimate the effect of the approximation in using the Debye formula, which is a specialization of the derived series, and, if desired, to obtain a higher degree of accuracy. Two cases are considered numerically.
The Thermodynamics of High-Polymer Solutions: II. The Solubility and Fractionation of a Polymer of Heterogeneous Distribution
Authors: Scott Robert L.
Published: January 2005

The free energy relations for heterogeneous molecular weight distributions developed in Part I, are applied to problems of solubility and fractionation. Critical conditions for solubility are obtained. A rigorous expression for the solubility is derived, although certain approximations are made to facilitate calculation, and to permit extension to polymers which are part ``gel.'' Following the same methods the thermodynamic equilibria involved in fractionation are described by mathematical expressions which permit a comparison of the extraction and precipitation methods. The effectiveness of fractionation is shown to be strongly dependent upon concentration.
The Influence of Molecular Flexibility on the Intrinsic Viscosity, Sedimentation, and Diffusion of High Polymers
Authors: Simha Robert
Published: January 2005

Expressions for the mean square separation of chain ends and modifications of the formula for an ideal coil are discussed. On the basis of these and of the hydrodynamic theory of intrinsic viscosity, an interpretation of the modified Staudinger rule is offered. It relates the exponent a of the molecular weight to a flexibility parameter p of the chain in a given solvent, varying between zero and one (Eq. (4), (5)). Recent data on polystyrene and on cellulose nitrate are analyzed in greater detail. By means of the frictional ratio f/f0, the sedimentation constant s and the diffusion constant D, respectively, are connected with the degree of polymerization in terms of p (Eq. (9)). The limiting dependence of sedimentation and diffusion rate upon molecular weight for a straight chain and an ideal coil is also found in this manner. A comparison shows satisfactory agreement between values for p found from intrinsic viscosity and those determined from sedimentation or diffusion rates, for certain cellulose esters and starch derivatives. Effects of solvent and of inhomogeneity in respect to molecular weight are discussed briefly.
Multiple Adsorption from Solutions
Authors: Walter John E.
Published: January 2005

The general theory of the adsorption of solutes from solutions which are treated by a process similar to that employed in chromatography is presented. By assuming a chemical equilibrium between adsorbed material and the solution, the adsorption equations can be solved explicitly. A detailed discussion of the two-component problem is given; the many-component problem and the extension of the theory to more general adsorption isotherms are considered briefly.
The Structure of Liquid Argon
Authors: Lund Louis H.
Published: January 2005

The method of Wall for calculating the free volume per atom in a liquid has been applied to liquid argon, using the atomic distribution curves at 84.3°K and at 91.8°K given by Eisenstein and Gingrich. From the free volumes at these temperatures, the entropy of the liquid at the boiling point is calculated to be 15.8 cal. degree−1 mole−1. This value, together with the calculated entropy, 32.2 cal. degree−1 mole−1, of argon vapor at the boiling point, give an entropy of vaporization of 16.4 cal. degree−1 mole−1. The latent heat of vaporization is thus calculated to be 6.01 kilojoules per mole; this is to be compared with the observed value of 6.3 kilojoules per mole. Presented also is a comparison of theoretical and experimental atomic distribution curves at the temperatures, 84.3°K and 91.8°K.
The Heat Content of Manganese at High Temperatures
Authors: Naylor B. F.
Published: January 2005

Heat contents above 298.16°K of two samples of electrolytic manganese were determined from room temperature to about 1440°K. From these data three transitions occurring at 1000±2°, 1374±5°, and 1410±5°K with heat effects of 535, 545, and 430 calories per gram-atom, respectively, were observed. Smooth curve values at 100° intervals and corresponding entropies are given as well as heat content and specific heat equations for the four modifications of manganese. A specific heat equation for γ-manganese was derived for the temperature range 298–1374°K from low temperature and high temperature thermal data; and corresponding heat contents and entropies above 298.16° for γ-manganese were calculated.
Phenomenological Theory of Emulsion Polymerization
Authors: Montroll Elliott W.
Published: January 2005

The process of emulsion polymerization is observed to occur in the following manner. An aqueous emulsion of monomer is prepared using a soap as the emulsifier. The addition of a catalyst starts the polymerization after an initiation period whose length depends on the mean radius of the monomer globules (long periods for large mean radius and short periods for small mean radius). As the reaction proceeds, the mean radius of the globules diminishes and the free soap concentration increases. It is believed that the initiation period is the result of the existence of an inhibitor in the monomer. The catalyst reacts with that part of the inhibitor which is dissolved in the water phase, so that in order for equilibrium to be restored some of the inhibitor must diffuse out of the monomer. Rate curves are derived on this basis using the added assumptions: (a) polymerization occurs at the monomer-water interface after the inhibitor concentration has reached a low threshold value. (b) radius distribution function of monomer has a single maximum.
Kinetics of the Isotopic Exchange Reaction Between Carbon Monoxide and Carbon Dioxide
Authors: Brandner John D. , Urey Harold C.
Published: January 2005

The rate of exchange of the C13 isotope between carbon monoxide and carbon dioxide has been studied. It has been found to be a surface catalyzed reaction on quartz, gold, and silver surfaces. Within the limits of experimental error, which are rather large because of change of surface activity, the reaction is independent of pressure and composition of the gas mixture. The exchange is accelerated by hydrogen or water vapor. Oxygen produces a rapid initial exchange attributed to a chain process of oxidation of carbon monoxide, but is without effect on the subsequent exchange. Isotope exchange takes place with a velocity convenient for study around 900°C, and at this temperature the apparent energy of activation is about 100 kcal.

Several mechanisms for the exchange of C13 have been examined. One which is not entirely free of difficulties accounts for the experimental data. This assumes the presence of H and OH molecules (or other activated forms of H2 and H2O) on the surface with the condition that the total amounts of these molecules is constant.
The Adsorption of Gelatin to Silver Bromide
Authors: Sheppard S. E. , Lambert R. H. , Swinehart D.
Published: January 2005

Experimental data are presented illustrating a specific case of amphipathic adsorption, namely, of gelatin to silver bromide. In this there is mutual coagulation of the silver hydrosol and protein, followed by peptization in excess of dissolved protein. The phenomena in their relation to the isoelectric point of the protein and the pH of the solution are interpreted in terms of a basically duplex polar: non-polar structure in proteins, and of a resonance factor, involving both adsorbent and adsorbate, in similar cases.
Photoluminescence of Lanthanide Complexes. II. Enhancement by an Insulating Sheath
Authors: Halverson F. , Brinen J. S. , Leto J. R.
Published: January 2005

The effect of an ``insulating sheath'' in reducing radiationless energy losses from a lanthanide chelate is postulated and techniques for developing this sheath are described. Data on luminescence of various europium chelates and synergic agent complexes are presented which demonstrate the efficacy of the sheath. A quantum efficiency approaching 80% is obtained for photoluminescence of a low viscosity hydrocarbon solution at room temperature.
Experimental Determination of the Field Gradient at the Deuteron in Formaldehyde
Authors: Flygare W. H.
Published: January 2005

A high-resolution microwave spectrograph has been constructed to observe small perturbations in rotational energy levels. High-resolution spectroscopy on OCD2 yielded the following values of the quadrupole coupling constants in the OCD2 principal inertial axis system: χaa = —13±4 kc/sec, χbb = 98±4 kc/sec, and χcc = —85±4 kc/sec. The spin—rotation coupling constants in OCD2 were calculated from the values for the proton obtained from the beam-maser spectroscopy on OCH2. Data on the 212→211 transition in OCHD is then analyzed yielding the following coupling constants in the OCHD principal inertial axis system: χa′a′ = 9±2 kc/sec, χb′b′ = 76±2 kc/sec, and χc′c′ = —85±2 kc/sec.

The above data show that the principal field-gradient axis system coincides with the bond axis system within experimental error. The principal field-gradient components all in units of esu cm—3 are qαα (C–H bond axis) = 8.45×1014, qββ = —4.15×1014, and qγγ (perpendicular to molecular plane) = —4.30×1014.
Reaction Rates of Xenon Fluorides with Oxides of Nitrogen
Authors: Johnston Harold S. , Woolfolk Robert
Published: January 2005

The rate of reaction of XeF4 and XeF2 with NO and with NO2 has been studied between 300° and 350°K at pressures between 0.1 and 30 mm. The second-order rate constant at 300°K and the activation energies are, respectively: XeF4+NO, 3 liters/mole sec, 7 kcal/mole; XeF2+NO, 0.3 liters/mole sec, 10 kcal/mole. The rate of NO2 with XeF4 and XeF2 was too slow to observe, k<0.01 liter/mole sec. The fluorides of xenon react with the oxides of nitrogen much more slowly than F2 reacts with NO or NO2. By means of a Polanyi—Semenov plot, the reactions of XeF4, XeF2, and F2 with oxides of nitrogen were combined to give an estimate of the successive dissociation energies of XeF4, which are (kcal/mole): XeF4→XeF3+F, 48; XeF3→XeF2+F, 15; XeF2→XeF+F, 54; XeF→Xe+F, 11. From these kinetic and thermochemical data a strong case can be made for the stepwise reduction of XeF4.
Effect of Pressure on the Infrared Spectra of Some Hydrogen-Bonded Solids
Authors: Reynolds Joseph , Sternstein Sanford S.
Published: January 2005

By using a diamond-anvil pressure cell, the infrared spectra of oxalic acid, polyvinyl alcohol, nylon 6–6, and a number of other materials at various pressures up to 25 000 atm were obtained. Studies on two of the pressure-induced changes, (1) the shift to lower frequencies of the hydrogen-bonded —OH and —NH stretching bands, and (2) the intensity changes of the two —CH2 stretching bands, are reported.
β-Proton Hyperfine Splittings in the Vinyl Radical
Authors: Adrian Frank J. , Karplus Martin
Published: January 2005

The valence-bond method is used to evaluate the β-proton hyperfine splittings in vinyl-type radicals (HC=CH2) as a function of the H–C=C bond angle. Since only spin polarization is included, use is made of semiempirical exchange integrals to compensate for the neglect of charge transfer and the presence of other approximations in the present treatment. It is demonstrated theoretically that both β-proton splitting constants should be positive and that the coupling with the proton trans to the sigma orbital occupied by the unpaired electron should be larger than the cis coupling. If the measured values of 68 and 34 Oe found in the vinyl radical are assigned accordingly (no experimental sign determination or assignment of cis versus trans has been made), good agreement with the calculated results is obtained for a bond angle in the reasonable range of 130°—150°.
Thermodynamics of Liquid In–Sb–Zn Solutions from Mass Spectrometry of Knudsen-Cell Effusates
Authors: Norman J. H. , Winchell P. , Staley H. G.
Published: January 2005

Solution thermodynamics of the In–Sb system in the presence of 0.02 mole fraction zinc have been studied by a mass-spectrometric Knudsen effusion technique. Activity coefficients for zinc and antimony were obtained, and partial molar heats of solution of antimony were determined from the partial molar heats of vaporization of the element. Partial molar heats and entropies of solution of zinc were calculated from the temperature dependence of the zinc activity coefficients.
Some Mathematical Generalizations of the Schrödinger Equation for Two-Electron Atoms
Authors: Kemeny G. , Walsh Peter J.
Published: January 2005

Within the past few years, considerable success has been found in using interelectron coordinates in atomic wavefunctions to describe atomic systems. The purpose of this paper is to supply a mathematical background for the generalization of this method for application to more complicated atomic, molecular, and solid systems.
Proton Spin—Lattice Relaxation of n-Paraffins in Solution
Authors: Woessner D. E.
Published: January 2005

The proton T1 values for carbon tetrachloride solutions of n-paraffins have been measured as functions of concentration. The common relaxation theory in which molecules act as spheres whose translational and rotational diffusion coefficients are inversely proportional to the same viscosity is checked with the aid of diffusion coefficients. The simple theory is inadequate, especially for the greater chain lengths. Effects of changes of chain configuration with concentration may be important.
Lattice Heat Capacity of Solid Hydrogen
Authors: Ahlers Guenter
Published: January 2005

The lattice heat capacity of solid hydrogen was measured at zero pressure, and at three constant volumes. The measurements extend from 2°K to the triple point for the zero-pressure data, from 2°K to the melting temperature at 22.56 cc/mole, and from 4° to 20°K at 19.83 and 18.73 cc/mole. The Debye thetas at 0°K are 128°, 169°, and 189°K at 22.56, 19.83, and 18.73 cc/mole, respectively. The temperature dependences of the Debye thetas are similar to those for other simple solids.

Some information about other thermodynamic properties was obtained from the heat capacities. The isothermal compressibility at 16.35°K at the melting pressure is essentially the same as at 4.2°K at the same pressure. The thermal expansion coefficient at 82 atm appears to have a maximum at about 12°K. At zero pressure the thermal expansion coefficient is approximately proportional to the temperature. The thermodynamic expression for the Grüneisen relation is not obeyed in solid hydrogen.
Lattice Vibrations of LaF3
Authors: Caspers H. H. , Buchanan R. A. , Marlin H. R.
Published: January 2005

The infrared spectrum of LaF3 in the region from 50–575 cm—1 is presented. Four strong absorption bands at 185, 208, 275, and 358 cm—1 are observed. The Raman spectrum has been investigated and five lines are found at 75, 292, 310, 365, and 392 cm—1. A group theoretical analysis has been carried out for the two slightly different crystal structures proposed for lanthanum trifluoride. The room temperature data seem to favor the more symmetrical bimolecular unit cell. Symmetry coordinates are discussed and some tentative assignments are made.
Photolysis of Nitric Oxide in the Presence of Olefins
Authors: McGee J. J. , Heicklen Julian
Published: January 2005

Electronically excited nitric oxide (A2Σ) produced by irradiation with the 2265- and 2144-Å lines of a cadmium arc induces the decomposition of ethylene to acetylene and hydrogen, apparently by a molecular mechanism. The acetylene, which also absorbs the radiation, photolytically reacts with the nitric oxide to give a solid deposit.
On the Connection between the Kinetic Approach and the Correlation-Function Method for Thermal Transport Coefficients
Authors: Résibois P.
Published: January 2005

We demonstrate the complete equivalence between the kinetic approach developed by Prigogine and co-workers and the correlation function formalism for the calculation of linear thermal transport coefficients. We show that in both cases these transport coefficients are determined by the solution of an inhomogeneous integral equation for a one-particle distribution function which is the generalization to strongly coupled systems of the Chapman—Enskog first approximation of the Boltzmann equation.
Infrared Spectrum of HCO
Authors: Milligan Dolphus E. , Jacox Marilyn E.
Published: January 2005

HCO and DCO have been prepared by the photolysis of HI (DI) and of H2S (D2S) in a CO matrix at 14° and at 20°K. The earlier infrared spectroscopic identification of these species has been confirmed. The C=O stretching frequency of DCO has been revised to 1800 cm—1. Unusually low C–H and C—D stretching frequencies, 2488 and 1937 cm—1, respectively, are obtained. Observations on H13CO and D13CO support these assignments. Spectroscopic, kinetic, and electron spin resonance data all suggest that the C–H bond is exceptionally weak. Fermi resonance may occur between the C—D and C=O stretching modes of DCO. Evidence is presented suggesting that considerable activation energy is required for the reaction of H atoms with CO.
Electronic Energy Levels at a Crystal Surface as Observed by Electron Diffraction
Authors: Yamaguchi S.
Published: January 2005

A cleavage face (104) of calcite was charged with electrons. This charged surface was studied by electron diffraction. Average energy of the electrons on the surface was estimated to be about 5 eV from the diffraction pattern obtained.
Critical Opalescence of Binary Mixtures: Perfluorotributylamine Isopentane
Authors: Debye P. , Caulfield D. , Bashaw J.
Published: January 2005

Critical opalescence of the binary liquid mixture perfluorotributylamine and isopentane is investigated. By combining light scattering and x-ray scattering measurements, data over a broad range of values of s/λ[s=2 sin (Θ/2), λ is wavelength] are obtained. The second moment of the averaged intermolecular pair potential is determined. It is shown how deviations from straight line behavior in plots of reciprocal intensity versus (s/λ)2 are determined by the shape of the intermolecular pair potential curve.
Molecular Distributions at Equilibrium. II. αω-Dichloropolydimethyl-N-Methylsilazanes in Equilibrium with Cyclic Dimethyl-N-Methylsilazanes
Authors: Van Wazer John R. , Moedritzer Kurt
Published: January 2005

By heating together various proportions of dichlorodimethylsilane and nonamethylcyclotrisilazane, [(CH3)2SiNCH3]3, an equilibrium is formed between the various chloroterminated N-methyldimethylsilazane chains and the trimeric ring structure. The equilibrium constant for the reaction whereby two end groups in these chains form a middle group plus dichlorodimethylsilane was found to be 2.7×10—3— a value which is a hundred times smaller than that corresponding to random sorting of the bridging methylimino groups with chlorine atoms. The ring—chain constant, which was also calculated, is large as expected for a system in which rings predominate.
Energy of Excimer Luminescence. I. A Reconsideration of Excimer Processes
Authors: Azumi Tohru , McGlynn S. P.
Published: January 2005

The interpretation of the energies of excimer luminescence of some polyacenes is considered and it is shown that neither simple molecular exciton attitudes nor charge resonance attitudes can provide satisfactory agreement with experiment. The D2k excimer formed from D2h aromatics is investigated and it is shown that the zeroth-order dimeric B3g state of 1La parentage may configurationally interact with the zeroth-order dimeric B3g state of charge resonance nature. The interaction of zeroth-order dimeric B2u states of 1La and charge resonance parentage is shown to be negligible. It is further suggested that the B3g interaction may be of sufficient magnitude to make experiment and theory compatible. The excimer fluorescences of benzene and phenanthrene have been investigated and established. A review of the data thereby provided, as well as other data in the literature, necessitates that the criteria relevant to excimer formation and luminescence given by Förster be modified. A number of other topics, including a few rather general group theoretic theorems relating to excimer formation, are briefly discussed.
Infrared Spectrum of ν2 of Dibromoborane and Dibromoborane-d
Authors: Lynds L. , Bass C. D.
Published: January 2005

The fundamental associated with the B–H and B—D stretching motions in HBBr2 and DBBr2 have been observed under high resolution. A series of evenly spaced lines occurs which has the appearance of a ⊥ band of a symmetric-top molecule. Analysis of the spectra gives an approximate value for the smallest moment of inertia from which the apex angle Br–B–Br was calculated to be 119.3±2°. It was possible to assign K values to the individual lines and to determine the position of the band centers for both HBBr2 (2622.4 cm—1) and DBBr2 (1960.1 cm—1).
Concerning the Magnetic Susceptibility of Praseodymium Oxides
Authors: MacChesney J. B. , Williams H. J. , Sherwood R. C. , Potter J. F.
Published: January 2005

Polycrystalline specimens of the compound PrO2 were prepared at high oxygen pressures (200–2000 atm). The phase so formed appears to be antiferromagnetic with a Néel temperature at 14°K. In contrast to this, measured susceptibilities of PrO2 prepared at lower oxygen pressures are reported to indicate the absence of cooperative effects. Phase relations of the system praseodymium—oxygen are examined to explain the discrepancy between the two data.
Statistical Thermodynamics of Polymer Solutions. IV. The Second Virial Coefficient for Comblike Branched Molecules
Authors: Casassa Edward F.
Published: January 2005

The statistical method of Zimm is used to derive the osmotic second virial coefficient A2 for branched polymer chains with the ``regular comb'' architecture; i.e., with branches of equal length attached at uniform intervals along the main chain. Calculations are carried as far as the ``double contact'' approximation, so that volume exclusion effects are neglected for configurations of two molecules in which there exist more than two intermolecular contacts. The treatment is, therefore, strictly applicable only near the Flory temperature (where A2 vanishes). The most significant conclusion, qualitatively, is that the behavior of A2 at this limit, for molecules of a given mass, depends on branched structure primarily through the variation of the mean-square radius of the molecule with branching. The utilization of the results in an approximate development for polymers in good solvents is discussed briefly.
Absorption Spectrum of Electrically Excited Nitrogen Molecules in the Vacuum-uv Region
Authors: Ogawa M. , Tanaka Y. , Jursa A. S.
Published: January 2005

When electrically excited nitrogen was used as an absorber, about one hundred absorption bands were observed in the 1080–1300-Å region. They are not due to absorption by ordinary nitrogen, but are produced by transitions from the vibrationally excited (v=4–13) ground state X 1Σg+ to the j 1Σu+, b 1Πu, l 1Πu, m 1Πu, and b′ 1Σu+ states.