bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the Rate of Dissociation of Oxygen
Authors: Byron Stanley R.
Published: January 2005

The rate of dissociation of oxygen behind strong shock waves in pure oxygen, in mixtures of oxygen and argon, and in air was determined over a temperature range from 2800°K to 5000°K. A long duration spark interferometer and drum camera were used to measure the shock speed and the variation of density behind the shock. The dissociation rate determined from the data can be represented by a collision theory equation, assuming that all of the available energy of vibration of the particles is transferred to dissociation in an inelastic collision. Oxygen atoms were found to be very effective in causing dissociation of oxygen molecules; the measured transition probability for energetically possible collisions between an oxygen atom and an oxygen molecule was 1.7, that for collisions between two oxygen molecules was 0.24. Collisions between nitrogen and oxygen molecules in air were found to be relatively ineffective in causing dissociation of oxygen; the measured rate of dissociation of oxygen in air was less than a factor of 2 larger than that caused by collisions between oxygen atoms and molecules alone.
Natural Spin Orbital Analysis of Hydrogen Molecule Wave Functions
Authors: Shull Harrison
Published: January 2005

Approximate wave functions for the hydrogen molecule ground state previously available in the literature are analyzed quantitatively into approximate natural spin orbital functions with particular attention to the corresponding occupation numbers. The analysis demonstrates the very great similarity of all such trial wave functions, and especially the largely molecular orbital nature of the wave function. In addition it shows a close relationship between the molecular orbital and valence bond functions, and the importance for allowing for angular correlation of the electrons by including terms dependent upon the azimuthal coordinate. The analysis particularly demonstrates that approximate natural spin orbital occupation numbers are nearly invariant under a wide variety of choices of basis functions, and therefore are particularly suitable for comparison of different approximate functions and for discussion of their respective properties.
Nuclear Magnetic Resonance Spectra of Some Dialkylmercury Compounds
Authors: Dessy Raymond E. , Flautt T. J. , Jaffé H. H. , Reynolds G. F.
Published: January 2005

The Hg199 and H1 nuclear magnetic resonance spectra of a series of dialkylmercury compounds have been obtained. The Hg199 results indicate that the shielding of the mercury increases along the series Me<n—Pr< Et<i—Pr. This increased shielding seems to be connected with an interaction of Hg199 and the β protons, as evidenced by the H1 resonance peaks and the Hg199–H1 spin-spin coupling constants.
Electron Drift Mobility in Liquid n-Hexane
Authors: LeBlanc Oliver H.
Published: January 2005

By means of a new experimental technique, the drift mobility of electrons in liquid n-hexane has been measured at field strengths below 2 kv/cm and at several temperatures in the range +27° to —47°. The drift mobility is found to vary with temperature as μ=μ0 exp(−Δε/kT), where μ0=0.3±0.2 cm2/volt-sec and Δε=0.14±0.02 electron volt. The results indicate that electrons injected into the liquid neither behave as free particles nor are they permanently attached to form negative ions. It is proposed that the injected electrons are alternatively trapped and thermally untrapped many times during their drift through the liquid. The experimental quantity Δε is interpreted as the average energy with which an electron is trapped. The origin of the traps is not evident, but possible trapping mechanisms are discussed.
Combustion Instability: Acoustic Interaction with a Burning Propellant Surface
Authors: Hart R. W. , McClure F. T.
Published: January 2005

A theory of the response of a burning solid to a sound wave is developed, based on time-dependent solutions of the transport equations relevant to a combustible having idealized physical and chemical properties. The development is restricted to small perturbations about the steady-state conditions for a rather simple model whose parameters have either a direct physical significance, or are experimentally determinable. The introduction of ad hoc time delays, or other phenomenological parameters has been entirely avoided. Time-dependent reaction rate chemistry also has been avoided, by considering only sufficiently fast reactions that the volumetric rate of reaction corresponds to the steady-state rate appropriate to the instantaneous local conditions as described by solution of the time-dependent transport equations. The predictions of the theory are discussed briefly, and several rather general observations are made. However, in view of the complexity inherent in the phenomenon and the present state of inadequate available empirical knowledge regarding this phenomenon, it is not yet possible to make a quantitative comparison between the theory and experiment.
Exact Lattice-Cluster Expansion for the Frost Points of Argon-Krypton Gas Mixtures
Authors: Walling J. F. , Halsey G. D.
Published: January 2005

The frost points of argon-krypton mixtures at various pressures and compositions of the gas phase have been determined. These results have then been analyzed by a generalized form of regular solution theory, where the energy of mixing parameter wAB has been allowed to vary with mole fraction as well as temperature. The results have been compared with an exact expansion in terms of Mayer cluster sums of the lattice-solution (Ising) model. The model does not entirely account for the data.
Exact Definition of Quasi-Thermodynamic Point Functions in Statistical Mechanics
Authors: Hill Terrell L.
Published: January 2005

The present note provides a rigorous definition and justification for the use of a ``local'' or ``point'' chemical potential (or activity coefficient), constant in value, in a transition region between two phases, or in the immediate neighborhood of a particular molecule or ion in a homogeneous fluid or solution. In the transition case, other quasi-thermodynamic point functions are also given exact definition; for example, the Helmholtz free energy, internal energy, and entropy. Possible applications, past and future, include the theory of liquids, solutions, electrolytes, and surface tension.
Normal Coordinates for the Out-of-Plane Deformations of Vinyl Bromide
Authors: Scherer J. R. , Potts W. J.
Published: January 2005

A normal coordinate analysis of the out-of-plane modes of vinyl bromide shows that the description of the 943 cm—1 and 583 cm—1 modes given by Torkington is not entirely correct. The 943 cm—1 mode has a close resemblance to the ethylene type twist and the 583 cm—1 mode may be easily visualized as a wagging motion of the whole vinyl group. A comparison is also made with C2H3D and trans-C2H2D2.
Solubility of Carbon in Silicon and Germanium
Authors: Scace R. I. , Slack G. A.
Published: January 2005

The solubility of carbon in silicon has been measured over the temperature range 1560 to 2900°C. The enthalpy of solution is 59±3 kcal/mole. A phase diagram for the system Si–C is presented, embodying these solubility data as well as the results of other high-temperature experiments with silicon carbide. It is found that SiC possesses a peritectic point at 2830±40°C. These studies were carried out in argon at pressures as high as 35 atmos. Solubilities of carbon in germanium were measured in the temperature range 2780 to 3170°C, at argon pressures up to 55 atmos, and a tentative phase diagram is given.
Direct Method of Measuring Molecular Quadrupole Moments
Authors: Buckingham A. D.
Published: January 2005

An experiment whose object is the determination of permanent molecular quadrupole moments is suggested. It is analogous to those used in measurements of electro-optical Kerr constants, but the uniform electric field proportional to the applied voltage V is replaced by the field gradient of a square four-wire condenser. If the wires at x=±a are at a potential V relative to those at y=±a, then the field gradient on the z axis will tend to orient quadrupolar molecules so that a fluid in the condenser will become doubly refracting. The induced anisotropy in the refractive index of a gas is shown to be first order in the applied voltage and of the form nx—ny=[B+(A/T)]V, while in the Kerr effect it is second order in V, and is given by nx—ny=[C+(D/T)+(E/T 2)]V2. The constant A is proportional to the molecular quadrupole moment and to the anisotropy in the polarizability, while B is proportional to the quadrupole moment induced in a molecule by a uniform field. In spherical molecules A, D, and E are zero. Calculations indicate that measurements of nx—ny, leading to accurate molecular quadrupole moments, should be practicable with present-day equipment. The theory of the effect in dense media is also developed.
NMR Spectrum of the Ethyl Group. An Exact Solution
Authors: McGarvey Bruce R. , Slomp George
Published: January 2005

An exact solution of the spin Hamiltonian for the ethyl group has been calculated and the results have been compared with the experimental NMR spectra of ethyl sulfide and tetraethylsilane. For ethyl sulfide it was found that δH0=52.8±0.4 cycles at 40 Mc and J=7.42±0.05 cycles. For tetraethylsilane, δH0=—16.9±0.4 cycles at 40 Mc and J=7.9±0.2 cycles.
Statistical Theory of Mass Spectra: Difficulties in Interpretation of Spectra of the Lower Alkanes
Authors: Friedman L. , Long F. A. , Wolfsberg M.
Published: January 2005

Mass spectra of a group of normal alkanes, C4 through C8, have been studied as a function of ionizing voltage. Appearance potentials have also been measured for most of the ions. At all voltages the yields of the ion fragments produced by loss of hydrogen atoms and by loss of methyl radicals are surprisingly low relative to their appearance potentials. Since for the lower ionizing voltages it can safely be assumed that there are no significant contributions to the patterns from secondary decompositions, these low yields must indicate a low intrinsic probability for the primary processes by which these ions are formed. For the typical case of n-pentane, the experimental data have been analyzed from the standpoint of the statistical theory of mass spectra and it is found that frequency factors in the ratio of 1:104:108 must be proposed to account for the yields from the hydrogen atom:methyl radical:ethyl radical extraction processes at low ionizing voltages. The implications of this wide range of frequency factors are discussed briefly.
Negative Atomic Ions
Authors: Johnson H. R. , Rohrlich F.
Published: January 2005

A semiempirical method is proposed for the computation of the electron affinities of negative atomic ions by extrapolation from the ionization potentials of the corresponding isoelectronic sequences. The method is based on a formula which can be justified on physical grounds and of which at least two parameters have direct physical interpretation. The results for the two short periods agree with experiments, with the exception of S—. The poorly determined ionization potentials of its sequence may well be responsible for part of this discrepancy. The method predicts a stable N— ion of small binding energy. The excited states and the fine-structure splitting can also be obtained by extrapolation based on theoretical formulas. The use of these formulas seems preferable to the method by Bates and Moisewitsch, but the results on excited states are the same. Our results make it appear likely that metastable excited states exist in B—, Al—, and P—.
Raman Intensities of the A1 Lines of Oxyanions
Authors: Chantry George W. , Plane Robert A.
Published: January 2005

The trace of the derived polarizability tensor has been measured on an absolute scale for the ions CO3=, NO3—, PO4—3, SO4—2, and ClO4— in aqueous solution. From these and the known normal coordinate matrix elements, the values of the derivative with respect to bond length have been calculated. Results are interpreted in terms of bond order, and indicate appreciable π bonding in the ions NO3—, SO4—2, and ClO4—. In these cases, as opposed to hydrocarbons, a π electron makes a larger contribution to the derived bond polarizability than does a σ electron.
``Improved'' Free-Volume Theory of Liquids. II
Authors: Dahler John S. , Hirschfelder Joseph O.
Published: January 2005

The Kirkwood nonlinear integral equation for determining the optimum free volume of a liquid is integrated by an iterative procedure with the approximation that the cell distribution function is spherically symmetrical. The potential of the system is assumed to be pairwise additive and the interaction between two molecules obeys the Lennard-Jones 12–6 potential. To simplify the computations, the contributions to the cell potential by molecules beyond the first shell of nearest neighbors are calculated as though the molecules were located at their lattice points. The method of Levine, Mayer, and Aroeste was used to optimize the lattice dimensions and take into account the existence of holes. Extensive tables are given for the configurational internal energy, compressibility factor, and configurational entropy. Comparison of the configurational internal energy and compressibility factor with the Monte Carlo calculations indicates that our isotherms correspond to extensions of the crystalline phase into a metastable low density region. Comparison of our configurational entropy with experimental data indicates that we are lacking the entropy of fusion. Our values of the configurational internal energy agree rather well and our values of the compressibility factor agree very poorly with the experimental data. Comparisons are also made with the results of other theoretical treatments.
Trapped Free Radical Concentrations
Authors: Hecht Charles E.
Published: January 2005

Average concentrations of trapped free radicals condensed from a gaseous mixture are calculated on the basis of a statistical model that assumes these concentrations to be those obtaining in the solid for which the free radicals and diluents are distributed in such a way that the entropy of the system is a maximum. This entropy is calculated in an independent pair, Bethe approximation. All kinetic and energetic considerations are neglected. The results are given as a function of diluent concentration and of the number of nearest neighbors in the solid. When condensed from a completely dissociated gas without diluents the free radical fraction ranges from 0.12 for a simple cubic lattice to 0.08 for a face-centered cubic lattice.
Effects of Gases on Irradiated Polyvinyl Chloride as Studied by Electron Spin Resonance
Authors: Kuri Zenichiro , Ueda Hisashi , Shida Shoji
Published: January 2005

The radicals produced by gamma irradiation of polyvinyl chloride powder in various gases and in vacuum are observed by electron spin resonance. Different patterns are observed for the irradiation in vacuum, air, and sulfur dioxide. No electron spin resonance absorption is obtained by the irradiation in nitrogen oxide, halogens, and hydrogen sulfide. The recombination reaction velocity of the radical produced in vacuum is measured at different temperatures to get the activation energy 38 kcal/mole.
Kinetics of the Deposition and Dissolution of Silver
Authors: Despic A. R. , Bockris J. O'M.
Published: January 2005

Galvanostatic measurements, made on spherical silver electrodes in highly purified aqueous acid solutions of silver perchlorate at current densities up to 10 amp cm—2, gave overpotential as a function of time and Faradaic current density at constant total current. Variables were total current density, concentration of silver ions and state of the electrode surface.

The theory of the surface diffusion kinetics was developed to encompass high current density regions and the surface adion concentration (cad0) evaluated.

A theoretical analysis of the steady state of surface diffusion control of the metal-ion exchange reaction shows that the current is distributed nonuniformly between growing sites, with constant potential over the electrode surface.

An equation previously developed by Rojter, Juza, and Polujan has been modified and shown to be applicable to galvanostatic transients when the transfer reaction is rate controlling. The symmetry factor β, of electrode kinetics, is shown to be potential dependent, and, in systems of sufficiently high i0 values, to tend to zero at high overpotential. This results in a limiting current density for a transfer controlled process. The tendency towards such a current was observed and shown to be quantitatively consistent with the discussion of β.
Nitrogen Chained Compounds as Intermediates in the Photolysis of Solid HN3
Authors: Papazian Harold A.
Published: January 2005

The ultraviolet and visible absorption spectrum of irradiated solid HN3 has been studied. Gas evolution during warmup of irradiated samples has been analyzed. It is proposed that photolysis in the solid yields NH radicals which react with the matrix to form the nitrogen chained compounds diiminohydrazine (H–N=N–N=N–H), triazene (H2–N–N=N–H), and the radical H–N=N. The latter is responsible for the blue color and paramagnetism of the solid. Multichained nitrogen compounds are known only as organic derivatives. Here they are formed and stabilized at low temperatures. On warmup of the blue solid, these compounds undergo decomposition yielding the products found from the blue solid.
Infrared Emission Spectrum of Gaseous HBO2
Authors: White David , Mann David E. , Walsh Patrick N. , Sommer Armin
Published: January 2005

The infrared emission spectrum of the vapor phase of the B2O3(l)–H2O(g) system has been studied at elevated temperatures over the region 700–4000 cm—1. Characteristic bands were found near 3680, 2030, and 1420 cm—1, and approximate B10–B11 and H–D isotope shifts measured. It is shown that these bands arise from the molecule HBO2. The intensity of the 2030 cm—1 band was studied as a function of both temperature and water pressure. The intensity vs temperature measurements lead to a heat of formation, ΔH0o, of —135.0±3 kcal/mole for HBO2(g). The spectroscopic data, considered in the light of our analysis of the B2O3(g) infrared spectrum, are compatible with the structure O=B–O–Hin which the OBO group is linear and the H is off-axis. The force constants are found to resemble those determined for B2O3(g). Complete vibrational assignments are given for HBO2(g) and its trimer (HBO2)3(g), a species which has recently been shown to exist in this system. Thermal functions have been computed for both molecules over a wide temperature range.
Unimolecular Decomposition of Chemically Activated Ethyl-d2 Radicals
Authors: Rabinovitch B. S. , Dills D. H. , McLain W. H. , Current J. H.
Published: January 2005

Addition of H atoms to trans-ethylene-d2 produces chemically activated ethyl-d2 radicals. This choice of the reactant ethylene permits all subsequent secondary processes of the hot ethyl radicals to be counted. The system has been studied between —78° and 160°C, and in most detail at room temperature, as a function of ethylene pressure. Experimental details are similar to those given in previous work on butyl. The relative energy spread of the formed ethyl radicals is here effectively greater than that observed for butyl radical since the thermal spread is not superimposed upon a minimum excess above the critical energy, as was the case for butyl. Nevertheless, relative to high-temperature thermal decompositions, the product ethyl radicals are comparatively monoenergetic, especially at the lowest temperature. The observed rate constant for decomposition ka was evaluated from the amounts of stabilization vs decomposition by C–H rupture. The decomposition rate is compared with theoretical expressions. An isotope effect appears to exist for transfer of H and D in the disproportionation of ethyl-d2 radicals at 25°.
Chlorine Nuclear Spin-Lattice Relaxation Time in Solid Sodium Chlorate and p-Dichloro Benzene
Authors: Bender P. A. , Jennings D. A. , Tanttila W. H.
Published: January 2005

The temperature dependence of the chlorine nuclear spin-lattice relaxation time between the pure quadrupole levels has been measured as a function of temperature in sodium chlorate and paradichlorobenzene. The results are compared with Chang's theory and found to be in good agreement. The Debye temperatures necessary to establish a fit with Chang's theory are 200°K and 90°K for sodium chlorate and paradichlorobenzene, respectively. The measurements were made in the temperature interval 300–10°K.
Electron Diffraction Study of the Structure of Trimethylphosphine
Authors: Bartell L. S. , Brockway L. O.
Published: January 2005

The structural parameters of gaseous trimethylphosphine, including standard errors, were found to be as follows: center of gravity bond distances were rCP=1.8465±0.003 A, and rCH=1.091±0.006 A; angles were <C–P–C=98.6±0.3°, and <P–C–H=110.7±0.5°; root-mean-square amplitudes of vibration were lCP=0.054±0.003 A, lCH=0.073±0.006 A, lP— —H=0.110±0.006 A, and lC— —C=0.084±0.005 A. The methyl groups were observed to be in staggered configurations analogous to those in ethane, with rotational barriers probably 1.5 kcal/mole or higher. A brief structural comparison with halogen derivatives and hydrides is presented.
Density of the Bonding Electrons in Diamond
Authors: Carpenter G. B.
Published: January 2005

The electron density in diamond, for the bonding electrons only, is derived from old but accurate experimental x-ray diffraction data by subtracting the contribution of the inner shall electrons from the total. The carbon-carbon single bond appears to be very diffuse.
Temperature Dependence of the Chlorine Pure Quadrupole Resonance Frequency in Molecular Crystals
Authors: Gutowsky H. S. , McCall D. W.
Published: January 2005

The Cl35 pure quadrupole resonance frequency has been observed in polycrystalline CH2Cl2, CHCl3, CCl4, (CH3)3CCl, and CH3CCl3 at temperatures of 77°K and above. In all cases, the resonance frequency decreases at higher temperatures, in qualitative agreement with Bayer's theory for the torsional motions of the molecules. However, a quantitative comparison of the theory with experiment, including Livingston's results at 4 and 20°K, reveals significant discrepancies which are discussed and attributed mainly to the decrease in torsional frequencies at higher temperatures. The resonance was found to ``fade out'' at temperatures below the transition points in those solids, CCl4, (CH3)3CCl, and CH3CCl3, where internal or molecular reorientations are known to occur. In the other compounds the resonance was observable up to the melting point. The origin of this phenomenon is discussed briefly.
Velocity of Compressional Waves in Liquid Hydrogen Fluoride and Some Thermodynamic Properties Derived Therefrom
Authors: Lagemann Robert T. , Knowles C. Harry
Published: January 2005

The velocity of compressional waves (sound waves) has been measured in liquid hydrogen fluoride over the temperature range — 15–19°. Using values of density and the specific heat at constant pressure from the literature, values of the following thermodynamic properties have been calculated over the same temperature range: adiabatic compressibility, isothermal compressibility, volume coefficient of expansion, specific heat at constant volume, and the ratio of specific heats.
Analysis of the Solid-State Spectra of Trivalent Neodymium and Erbium
Authors: Wybourne B. G.
Published: January 2005

A term analysis of the solid-state spectra of trivalent neodymium and erbium has been made and this has allowed terms to be assigned to most of the observed levels of these ions. The complete spin-orbit matrices, with the addition of the electrostatic interaction energies, corresponding to the f3 and f11 configurations have been diagonalized to calculate the energy level schemes for the neodymium and erbium ions, respectively. The appropriate parameters were calculated by a least-squares method.
Low Excited States in C2
Authors: Clementi Enrico , Pitzer Kenneth S.
Published: January 2005

In this paper the energies of the low electronic states of the C2 molecule are calculated, using a semi-empirical approach. In the calculation, the two-center core integrals, and the one-center Coulomb integral, are empirical parameters which are obtained by fitting of the Morse potential curves and from atomic data, respectively. The standard ASMO-LCAO state wave functions are expanded in covalent, single ionic, and double ionic components, which are constructed so as to obey the Wigner-Wittmer dissociation rules at infinite internuclear distances. The contributions for each component of the expanded state wave functions are obtained by the variational method. The states considered are 1Σg+ state of the πu(4) configuration (of 2p orbitals), the 3Πu and 1Πu states of the πu(3)σg(1) configuration, and the 3Σg−,1Δg,1Σg+ states of the πu(2)σg(2) configuration. The calculated energies of the 1Σg+ and 1Πu electronic states agree well with experiment. Finally, a critical analysis is given of the coefficients of the expansion in covalent and ionic structures.
Experimental and Theoretical Aspects of Higasi's Equation for a Quick Determination of Electric Dipole Moment in Solution
Authors: Krishna Bal , Srivastava K. K.
Published: January 2005

In the present investigation the authors have determined the electric dipole values for twenty-three organic solutes according to Higasi's method. Except for two substances, viz., iodoform and ethylene dibromide, the dipole values so obtained agree fairly well with those obtained by usual methods. A reassessment of Higasi's equation has been made on theoretical grounds and a more general equation has been obtained.
Dielectric Relaxation of Dilute Solutions in the Millimeter Wave Region
Authors: Schneider Jürgen
Published: January 2005

The dielectric losses of benzophenone, diphenylether, diphenylamine, chlorobenzene, and aniline, measured at 12.33, 6.19, 3.08, and 2.47 mm wavelength in dilute benzene solutions, have been found to fit Debye type relaxation curves within the limits of experimental error. The distinctly lower relaxation time of diphenylether and of diphenylamine, compared to the one for benzophenone, can be explained by a high internal mobility of the phenyl rings in these two molecules. Similarly, the mobility of the amino group in aniline results in a decrease of the relaxation time, compared to the rigid chlorobenzene molecule.
Microwave Absorption in Compressed Oxygen
Authors: Maryott A. A. , Birnbaum G.
Published: January 2005

Precise measurements of the absorption in oxygen resulting from the small magnetic dipole moment are reported at frequencies near 2, 3, 9, and 23 kMc and at pressures in the range from 3 to 70 atmos. Up to 10 atmospheres the resonant contribution agrees with the Van Vleck-Weisskopf theory and the line width increases in proportion to the pressure. The line width (relaxation frequency) for the nonresonant contribution also increases in proportion to the pressure, but is only about one-third as large as the resonant line width. Above 20 atmospheres the resonant absorption shows anomalous behavior resembling that previously noted in the case of the inversion spectra of NH3 and ND3. In particular, the resonant frequency appears to decrease rapidly while the line width changes much less rapidly than the pressure.
Theory of Microwave Absorption by Compressed Oxygen Gas
Authors: Mizushima Masataka
Published: January 2005

A theoretical explanation of the deviation between observed microwave absorption by high-pressure oxygen gas and the prediction by the simple Van Vleck-Weisskopf theory is attempted. The nonspherical part of the intermolecular force is considered and the distortion of energy levels and wave functions is calculated. It is found that the nonresonant absorption vanishes and a low-frequency (∼10 kMc) resonance appears at high pressure, while the 60 kMc resonance does not change much. This theory can explain the observed data.
New Method for the Measurement of Microwave Integrated Line Intensities and Line Widths
Authors: Dymanus A. , Dijkerman H. A. , Zijderveld G. R. D.
Published: January 2005

A method is described for the measurement of microwave line widths and integrated intensities with Stark-modulation spectrometers. The method makes use of a property that the peak intensity αmax,meas, measured at a given Stark field E, depends, under certain conditions, only on the half-width a and the peak intensity αmax. In the present investigation, the method has been used with a Stark cavity spectrometer employing ``antimodulation'' techniques which were described in an earlier paper. Experimental procedure, and the possibilities of the method are illustrated by measurements on two lines arising from the J=1→2 rotational transition of the 16O12C32S molecule in the ground state, and in the excited bending-vibrational state (l-doublet). The measured integrated intensity of the ground-state line of (103±3.5)10—5 cm—1 sec—1 at 1 mm Hg agrees well with the theoretical value of 101.5·10—5 cm—1 sec—1. The half-width constant of the ground-state line and of the l-doublet line was found to be 6.27±0.18 and 6.17±0.23 Mc/mm Hg, respectively. From the measurements on the various mixtures of OCS and N2, a value of 4.36±0.12 Mc/mm Hg has been obtained for the collision broadening factor for OCS molecules with N2 molecules.

The present method is applicable to sharp (also weak) lines of which the Stark splitting pattern is quantitatively known.
Proton Magnetic Resonance Studies of Some Silicones
Authors: Kusumoto Hazime , Lawrenson Ian J. , Gutowsky H. S.
Published: January 2005

Proton magnetic resonance techniques have been used to study the molecular motions occurring in some dimethyl silicones. The substances investigated were cured Silastic 80, 400 Gum, and 200 Fluid (viscosity grade 20 centistokes at 25°C). Measurements were made of the absorption line shape from 77°K to room temperature, and of the spin-lattice relaxation time, T1, from 160°K to 415°K. Evidence is found for the existence of methyl group reorientation about the triad axis, segmental motions about the Si–O bonds and a form of intramolecular ``spiral'' motion of the (CH3)2Si groups. The relation of the latter motion to the difference in macroscopic properties of natural and silicone rubbers is discussed.
Complete Classical Theory of Vibrational Energy Exchange
Authors: Rapp Donald
Published: January 2005

By using purely classical mechanics, the amount of energy ΔEvib transferred to an harmonic oscillator molecule in a head-on molecular collision of velocity v0 is calculated. In the classical limit for small transition probabilities, the quantum-mechanical probability per collision of going from the ground state to the first excited state is given by P0→1=(ΔEvib/ℏω), where ω is the frequency of the oscillator, and ΔEvib is the energy classically transferred to the oscillator in one collision. This transition probability is integrated over a normalized distribution of collision velocities to give an average probability for all collisions 〈P0→1〉. Finally, 〈P1→0〉 is calculated from the law of microscopic reversibility. The result turns out to be the same as that obtained by Herzfeld,1 who used a quantum-mechanical perturbation treatment and went to the classical limit by assuming that the de Broglie wavelength of the molecule colliding with the oscillator is small compared to the range of the intermolecular forces.
Construction of Hybrid Orbitals
Authors: Murrell J. N.
Published: January 2005

A method is given for constructing the best hybrid orbitals for a molecule M—(X1···Xk) from a set of n atomic orbitals of M, based on the principle of maximum overlap. To illustrate the theory, hybrid orbitals for ClF3 are constructed from the chlorine 3s, 3p, and 3d atomic orbitals.
Theoretical Investigations on the Light Scattering of Colloidal Spheres. VIII. Angular Location of Intensity Maxima and Minima in the Radiation Diagram of Colloidal Spheres
Authors: Nakagaki Masayuki , Heller Wilfried
Published: January 2005

The angular position of scattering maxima and minima in the radiation diagram of nonabsorbing colloidal spheres is calculated for (m—1)→0 and for m=1.20, by using in the former case the Rayleigh-Gans approximation and in the latter the exact Mie scattering functions. By means of empirical equations based upon the discrepancies between the Rayleigh-Gans data and the Mie data, the approximate location of scattering maxima and minima is calculated also for the m values 1.05, 1.10, 1.15, 1.25, and 1.30. The expected precision and accuracy of particle size determinations from the angular location of scattering maxima and minima is discussed and the minimum angular ranges to be covered in a given instance are defined. A few pertinent features of the related La Mer method (HOTS) are briefly discussed.
Electron Attachment in C8F16O
Authors: von Hoene J. , Hickam W. M.
Published: January 2005

The negative ion spectrum of C8F16O6 at low electron energies has been obtained using the mass spectrometer. The most intense peaks are identified as C8F16O—, C7F14—, C5F9O—, C4F8O—, C4F7O—, C3F6O—, and CF3O— ions. Formation of the CF3O— ion requires a rearrangement process. Appearance potentials and attachment energy ranges of the most intense peaks are given. Positive and negative ion fragmentation of the molecule is discussed relative to the components of the mixture, perfluoro-2-butyltetrahydrofuran and perfluoro-2-propyltetrahydropyran and its separation.
Infrared and Raman Spectra of Fluorinated Ethanes. XII. 1,1,2,2-Tetrafluoroethane
Authors: Klaboe Peter , Nielsen J. Rud
Published: January 2005

The infrared absorption spectra of gaseous CHF2–CHF2 at five temperatures between 30° and 170°C and of the crystalline solid at —170°C have been obtained with a Perkin-Elmer double-pass spectrometer equipped with CsBr, NaCl, and LiF prisms. The Raman spectrum of the liquid at 20°, —25°, and —80°C has been photographed with a 3-prism glass spectrograph of reciprocal linear dispersion 15 A/mm at 4358 A, and polarization measurements have been made. In the gaseous and liquid states the compound exists as a mixture of two rotational isomers of symmetries C2h and C2, respectively, the former (trans) being the more stable. In the crystalline state only the trans configuration is present. A value of 1160±100 cal/mole was found for the enthalpy difference ΔH0 in the gas. In the liquid ΔH0 is much smaller. With some uncertainties, the vibrational fundamentals have been assigned for each isomer.
Electron-Population Analysis and the Dipole Moment of the LiH 1Σ+ Excited State
Authors: Karo A. M.
Published: January 2005

Detailed consideration is given to some properties of the first excited electronic state. Following the analysis proposed by Mulliken, SCF LCAO-MO coefficients are used to obtain qualitative information about the electron distribution. Comparison is made with earlier work with respect to the description of the excited state in terms of the interacting configurations. In addition to the excited-state dipole moment, the effective electric moment between the ground and excited states is also calculated. From this, the oscillator strength for the first allowed transition is computed as a function of the internuclear distance.
Mechanics of Atomic Recombination Reactions
Authors: Bunker Don L.
Published: January 2005

A treatment is developed by means of which it is possible to calculate an equilibrium constant for the formation of a collision complex from a pair of chemically interacting atoms. For iodine atoms, this leads to a value of the rate constant for I+I+M→I2+M, if the mechanism is 2I⇌I2*(1Σ), I2*+M→I2+M. The rate constant so calculated agrees with that obtained by a statistical procedure [J. Keck, J. Chem. Phys. 29, 410 (1958)].

The calculation also furnishes enough information about the mechanical details of collisions so that the contribution of molecular states other than 1Σ to recombination may be deduced. As a result a fairly conclusive discussion may be given of the plausibility of the various detailed mechanisms thus far suggested. A most likely mechanism and a possible calculation based on it are proposed.
Thermal Conductivity of Gas Mixtures in Chemical Equilibrium. II
Authors: Brokaw Richard S.
Published: January 2005

The expression for the thermal conductivity of gas mixtures in chemical equilibrium is presented in a simpler and less restrictive form. This new form is shown to be equivalent to the previous equations.
Dynamical Theory of Diffusion in Crystals. IV. Some Aspects of the Introduction of Irreversibility
Authors: Rice Stuart A. , Frisch Harry L.
Published: January 2005

The origin of irreversibility in the phenomenon of crystal diffusion is examined from a dynamical point of view. It is shown that straightforward considerations lead to the establishment of two time scales, one for jumps between lattice sites and one for vibrations about a given lattice point. The dissipation of energy is shown to occur almost entirely by relaxation of ``recaptured'' particles, little energy being lost in the transit across the barrier. The quasi-equilibrium and nonequilibrium formulations are compared and shown to be quite similar in structure and functional dependence.
Variational Theory of Chemical Reaction Rates Applied to Three-Body Recombinations
Authors: Keck James C.
Published: January 2005

A ``variational'' theory, which gives a least upper bound to the rate of a chemical reaction, is presented. The reaction is represented by the motion of a point in phase space across a trial surface dividing the ``initial'' and ``final'' chemical states. The trial surface is well defined in regions of phase space where interactions causing reaction are negligible, but is subject to arbitrary variations otherwise. It is shown that a least upper bound to the reaction rate can be obtained by calculating the rate at which representative points cross the ``trial'' surface and then minimizing this rate with respect to allowed variations of the surface. Explicit calculations of the recombination rate of attracting atoms in the presence of repulsive third bodies are made for a simple trial surface having one adjustable parameter. At low temperatures, the experimental rate constants are quite close to the theoretical bounds; at high temperatures, the experimental data fall away from the bounds in a manner which can be understood in terms of various approximations contained in the theory. Promising methods of improving the agreement between theory and experiment are discussed.
Dependence upon Volume of Nuclear Quadrupole Interactions in Crystals
Authors: Bernheim R. A. , Gutowsky H. S.
Published: January 2005

The electric quadrupole splitting of the Na23 nuclear magnetic resonance has been measured in single crystals as a function of pressure and temperature for NaNO3, and as a function of temperature for NaBrO3. It is found that the electric field gradient at the sodium nuclei varies as V—3.8 in NaNO3 and as V—2.0 in NaBrO3. These results, together with the previously reported V—1.9 dependence for Na23 in NaClO3, are compared with theoretical values computed from point charge models for the crystal lattices. It is concluded that the large volume dependence in NaNO3 arises from the anisotropic thermal expansion and compressibility of the hexagonal crystal plus the retention of size and configuration of the NO3— group. The experimental results for NaClO3 can be explained in the same manner, assuming a rigid ClO3— group; however, this model does not account for the V—2 dependence of the Na23 quadrupole coupling observed in NaBrO3. The assumed rigidity of the ClO3— group is supported by the small volume dependence, V—0.10, found for the Cl35 quadrupole coupling in NaClO3, and also by calculations of the interionic contribution to the field gradient at the chlorine nuclei in NaClO3 and KClO3.
Ligand-Field Theory of Linear Gaseous Molecules Involving the First Transition Series Elements
Authors: Berg Robert A. , Sinanoglu Oktay
Published: January 2005

The diatomic and linear triatomic molecules such as the oxides and halides of the ``iron-group'' elements are of importance in high temperature systems. Although the various high symmetry compounds of these elements, e.g., the solid oxides, hydrated complexes, etc., are sufficiently understood in terms of the present ligand-field theory, no semiquantitative schemes have been utilized to understand and predict the spectroscopic and thermal properties of their simple, gaseous molecules. In this article, the observed dissociation energy vs atomic number curves for the linear gaseous oxides and the halides of the first transition series are compared with the corresponding energy curves of the solid oxides and the halides, and the similarities are pointed out. It is shown that the double maximum stabilization curves observed in the gaseous molecules as well can be understood in terms of the splitting of the (3d) shell of the transition atoms in a linear (C∞v or D∞h symmetry) ligand field with two independent splitting parameters, one of which is small. A method for predicting the low-lying molecular spectral states is developed. The energies of the states depend on the splitting parameters and the electron interactions. The parameters are estimated from the first portion of the thermal data and used only for these elements. The electron interaction energy is obtained from the spectral terms of free atoms (ions). Unlike the case in the high symmetry applications, this procedure here takes into account ``electronic correlation'' (configuration interaction) effects. The generality of the treatment is revealed by comparing the results of the simple ionic and covalent models with those of the molecular orbital method. Calculations of spectral states are made for ScO, TiO, VO, and CrO, and experimental data are discussed.
On the Kinetic Theory of a Fluid Composed of Rigid Spheres
Authors: O'Toole James T. , Dahler John S.
Published: January 2005

The kinetic theory of a fluid composed of rigid sphere molecules is studied by using the methods of statistical mechanics. It is confirmed that the equation of change for the singlet distribution function has precisely the form originally suggested by Enskog on the basis of intuitive arguments involving an appeal to the notion of forward and inverse collisions. The formal derivation of the hydrodynamical equations of motion for the fluid reveals that the flux tensors for the rigid sphere fluid are of the same general form as those for a fluid composed of molecules which interact according to nonimpulsive forces.
Emission Spectra of Trivalent Terbium
Authors: Van Uitert L. G. , Soden R. R.
Published: January 2005

The luminescent emission spectra of the members of the series Y1—xTbx antipyrene 6I3 and Ca1–2xNaxTbx WO4 have been measured and compared. The antipyrene complexes show spectra similar to that for terbium octahydrosulfate which is a simple inverted multiplet. The tungstate spectra results from emissions originating from two electronic levels. The relative intensities of the emissions from these two states are dependent upon the terbium concentration. In Na0.5Tb0.5WO4 the usual spectral bands are by far the stronger. In CaWO4:Tb0.0001 the situation is reversed.
Solvent Effects in Nuclear Magnetic Resonance Spectra
Authors: Buckingham A. D. , Schaefer T. , Schneider W. G.
Published: January 2005

Contributions to nuclear screening (chemical shifts) arising from molecular interactions with solvent molecules (excluding hydrogen bonding) are discussed in terms of appropriate theoretical models. These include contributions from van der Waals interactions σw, from the magnetic anisotropy of the solvent molecule σa, and from polar effects σE. By a suitable choice of solute-solvent systems it has been possible to demonstrate each of these effects experimentally for proton resonances. For CH4 as a solute, σw was in all cases negative, its magnitude varying with the nature of the solvent and amounting to as much as 0.6 ppm for high molecular weight solvents. In agreement with the theoretical models, σa was found to be positive for disk-shaped solvent molecules and negative for cylindrically symmetrical rod-shaped molecules, its magnitude in extreme cases reaching 0.75 ppm. For CH3CN as a solute, σE was negative and showed the expected dependence on the dielectric constant of the solvent.
Dissociation of C6H5T Following Beta Decay
Authors: Carlson Thomas A.
Published: January 2005

The relative abundance of the various charged fragments formed following beta decay of mono tritiated benzene was measured with a specially designed mass spectrometer. In nearly every case the C–He bond was ruptured, the charge remaining with C6H5+. In 28% of the events the C6H5+ species were further excited to produce more than 30 different charged fragments. Comparison of this spectra with the electron impact data on benzene is made to arrive at an estimate of the energies involved in the initial excitation and the results are found to be in essential agreement with those of other tritiated hydrocarbons. The molecular excitation of benzene following beta decay is then shown to result probably from a sudden electronic perturbation following the formation of the doubly charged He3 nucleus.

Some results on the dependence of the collection efficiency of a given ion on its kinetic energy are also discussed.
Rate Constants at Low Concentrations. V. Mechanism of Reaction of Ozone with Photolyzing Nitrogen Dioxide in Presence of Excess Oxygen
Authors: Ford H. W. , Doyle G. J. , Endow N.
Published: January 2005

Trace concentrations of ozone and nitrogen dioxide in pure, dry air at atmospheric pressure were exposed to a known intensity of 3660 A radiation in a stirred flow reactor at 300°K. An increase of steady-state concentrations of ozone and nitrogen dioxide above their dark values was observed and measured. A value of k7Keq=0.44 sec—1 (NO3+NO→2NO2, k7, NO2+NO3⇌N2O5, Keq) was obtained from the data using a postulated mechanism. The good agreement between this value and the values of 1.0 sec—1 obtained by I. C. Hisatsune, B. Ogg, and R. A. Crawford [J. Am. Chem. Soc. 79, 4648 (1957)] supports the validity of the proposed mechanism.
Microwave Spectrum and Molecular Structure of Monochloroacetonitrile
Authors: Graybeal Jack D.
Published: January 2005

The microwave spectrum of monochloroacetonitrile has been measured and analyzed. By assuming certain molecular parameters the structure of the planar framework was determined from the moments of inertia of two isotopic species. The C–Cl and C–C bond lengths were found to be 1.767 A and 1.472 A, respectively. The CCCl angle was found to be 111°24′. The H···H distance was found to be 1.728 A. The chlorine nuclear quadrupole coupling constant along the C–Cl bond axis was calculated to be —76.36 Mc. The direction of the dipole moment was estimated to be between the C–Cl and C–CN bond directions, 28° from the latter. The observed C–Cl distance, in addition to the observed nuclear quadrupole coupling constants in the solid and gaseous molecules, are indications that there is very little double bond character in the C–Cl bond. The ionic character of the C–Cl bond was estimated to be 18%.