bluuebunny/crossref_metadata_2025 huggingface dataset:
Unimolecular Decomposition in Nonequilibrium Systems. sec-Butyl and sec-Butyl-d1 Radicals Produced by Chemical Activation at Different Levels of Vibrational Excitation
Authors: Rabinovitch B. S. , Kubin R. F. , Harrington R. E.
Published: January 2005

Results of earlier studies on the decomposition of activated sec-butyl radicals formed in nonequilibrium systems by the addition of H or D atoms to trans-butene-2, to cis-butene-2, and to butene-1 are summarized together with new data. The work constitutes a program of study in which butyl radicals have been produced at six different levels of minimum internal excitation energy. Two choices of ambient temperature (300° and 195°K), together with pressure variation over the (ideal) limiting range of zero to infinity, give rise in these systems to a further increase in the number of values of the average energy of the reacting radicals; these energies correspond to a range from 7.2 to 14.2 kcal mole—1 for the average excess energy of the radicals with respect to decomposition. Twenty-one of such average energy states out of the possible twenty-four values, corresponding to two pressure extremes at each of two temperatures, have been obtained experimentally. These data permit a more consistent test of the theoretical models which were presented in the earlier work. A comparison and discussion of the observed rates is given. The agreement is satisfactory. An ``energy'' isotope effect which arises upon replacement of reactant H atom by D is well accounted for. It is concluded that the merits of the chemical activation technique for clarifying the nature of unimolecular reaction, at high levels of vibrational excitation of polyatomic species, are well borne out. The present evidence, together with other work, shows the usefulness of the Marcus—Rice rate expression in all systems where the assumptions may apply, when accurate calculations are made with quantum statistical models. The effect of variation of thermochemical and molecular parameters on the calculations is described. Not only are all vibrational degrees of freedom to be taken as active, as the best a priori assumption, but there is evidence that where they exist, internal rotations and possibly one of the over-all rotations should be so treated also.
Kinetics of Small Systems. I
Authors: McQuarrie Donald A.
Published: January 2005

An extension of chemical kinetics to small systems is made by means of the application of stochastic processes. The classical, or deterministic, approach to chemical kinetics is replaced by a probabilistic model which furnishes not only concentration—time expressions, but also expressions for the statistical fluctuations about the deterministic curves.
Electronic States of Hopfield's Oxygen Emission Bands
Authors: LeBlanc Francis J.
Published: January 2005

The Hopfield emission bands of oxygen are shown to arise from a transition in the O2+ molecule. The upper state is new, designated c 4Σu—, assuming an allowed transition, while the lower state is the known b 4Σg— state. The single observed vibrational level of the c 4Σu— state lies at 24.56 eV above the ground state of the O2 molecule. The rotational constant B of the upper state vibrational level has a value of 1.557 cm—1.
Mean First-Passage Times and the Dissociation of Diatomic Molecules
Authors: Shuler Kurt E. , Weiss George H.
Published: January 2005

The collisional activation of diatomic molecules to dissociation can be considered as a random walk with an absorbing barrier in the energy space of the molecules. In such a model, the rate of activation to dissociation is related to the mean first-passage time of the molecules across the absorbing barrier. We have computed here the mean first-passage time for an ensemble of oscillators in an initial Boltzmann distribution with transitions limited to nearest-neighbor states (| Δv |=1) and for an ensemble of oscillators initially in the ground state (v=0) which undergo transitions between nonnearest-neighbor states (| Δv |≥1). It is shown that the magnitude of the mean first-passage time is very sensitive to the height (in energy space) of the absorbing barrier and to the ``jump distance,'' | Δv |>1, for nonnearest-neighbor transitions. The implications of these results on the mechanism of the activation and dissociation of diatoms are discussed briefly.
Melting of Graphite at Very High Pressure
Authors: Bundy F. P.
Published: January 2005

A method of flash-heating small rods of graphite inside a superpressure cell has been developed. The heating energy was inserted in less than 7 msec from a bank of electrolytic capacitors. This quick heating and cooling allowed fusion and freezing of the graphite to occur without serious melting or reaction of the surrounding wall material. Electrical data were recorded with oscillographs and cameras. The start of melting was found to be indicated by an abrupt downward trend of resistance. Polished cross sections of the samples showed clearly the part which melted. Melting temperatures increased from about 4100°K at 9 kbar to a maximum of about 4600°K in the region of 70 kbar, then decreased to about 4100°K at 125 kbar. A value of 25 kcal/mole for the heat of fusion at 48 kbar was determined. The graphite/diamond/liquid triple point is shown to be at about 4000 to 4200°K and 125 to 130 kbar.
Study of the H6 Ring in the Molecular Orbital and Alternant Molecular Orbital Approximation
Authors: Moskowitz Jules W.
Published: January 2005

A configuration interaction calculation in a molecular orbital basis has been carried out on a system of six hydrogen atoms arranged in a regular hexagon. The alternant molecular orbital and second-order perturbation theory approximations have been investigated. All multicentered integrals have been accurately computed.
Normal Vibrations of the Polymer Molecules of Helical Configuration. III. Polyoxymethylene and Polyoxymethylene-d2
Authors: Tadokoro Hiroyuki , Kobayashi Masamichi , Kawaguchi Yôichi , Kobayashi Akira , Murahashi Shunsuke
Published: January 2005

Polarized infrared spectra of polyoxymethylene (POM), — (CH2O)n—, and POM-d2, — (CD2O)n— have been measured in the region from 4000 to 100 cm—1. The spectra of POM at elevated temperatures were also observed. The selection rules for POM molecules are derived under the factor group D(10π/9). The normal vibrations of POM and POM-d2 are calculated for the Raman active A1 symmetry species, the infrared active A2 species and the Raman and infrared active E1 species, by the use of the GF-matrix method with the Urey—Bradley force field taking into account the torsional displacement coordinates of the skeleton. The results show fairly good agreement of the observed and calculated frequencies. The assignments of the bands are given and discussed.
Centrifugal Distortion Effects in Asymmetric Rotor Molecules. I. Quadratic Potential Constants and Average Structure of Oxygen Difluoride from the Ground-State Rotational Spectrum
Authors: Pierce Louis , Di Cianni Nicholas , Jackson Robert H.
Published: January 2005

The microwave spectrum of oxygen difluoride has been thoroughly investigated in the frequency regions 8 to 40 and 49 to 60 kMc. A total of 83 absorption lines have been assigned as ground-state rotational transitions in which the total angular momentum J ranges from 1 to 39. These data provide the means for a critical test of the Kivelson—Wilson theory of centrifugal distortion. It is found that the K—W energy expression only approximately accounts for the measurements. The K—W formula obtains when (1) separation of rotation and vibration is carried out to second-order of approximation, and (2) when the quartic (P4) distortion terms in the resulting effective rotational Hamiltonian are treated by first-order perturbation theory. It is found that both of these approximations must be carried one order higher to obtain a satisfactory fit of the observed rotational frequencies of OF2.

Analysis of the rotational spectrum by the method of least squares yields the following ground-state rotational parameters (Mc): A=58782.630, B=10896.431, C=9167.412, τxxxx=—0.0949559, τzzzz=—6.615402, τxxzz=0.399611, τxzxz=—0.162486, HJK=—2.2184×10—6, and HKJ=3.1073×10—6, where HJK and HJK are the coefficients of semiempirical P6 distortion terms in the effective rotational Hamiltonian. The quartic distortion constants yield vibrational frequencies which agree with the observed values to within 4% or better. By combining microwave data with the observed vibrational frequencies the following quadratic potential constants are obtained: fr=3.9499 mdyn/Åfrr=0.8059 mdyn/Å,fα/r2=0.7237 mdyn/Å,frα/r=0.1373 mdyn/Å.Using this potential function with formulas derived by Laurie and Herschbach the average structure of OF2 in the ground vibrational state is found to be 〈r〉=1.4124 Å,  〈α〉=103∘10′,where r is the OF distance, and α the FOF angle.
Molecular Interaction and Linewidth of the Asymmetric Molecule SO2. II. SO2–CO2 Collisions
Authors: Krishnaji  , Chandra Suresh
Published: January 2005

The linewidth of the 91,9→82,6 transition of SO2, broadened by carbon dioxide, has been measured. The measured linewidth for SO2–CO2 collision is 7.22 Mc/mm. The hard-sphere collision diameter corresponding to this is 8.01 Å. The result has been explained by Anderson's theory on the basis of dipole—quadrupole interaction. The quadrupole moment of carbon dioxide so evaluated is 5.37×10—26 esu.
Analytical Self-Consistent Field Functions for Positive Ions. I. Isoelectronic Series with 2 to 10 Electrons
Authors: Clementi Enrico
Published: January 2005

Analytical self-consistent field (SCF) functions for the neutral atoms and positive ions isoelectronic series of 2 to 10 electrons up to Z=36 are presented. These computations deal with the lowest electronic configuration ground states and excited states. The basis set of Slater-type orbitals (STO) is fully optimized with respect to the orbital exponent, and considerable effort was given to obtain a short expansion. A maximum of nine STO's were considered sufficient for the largest expansion. The total energies of each isoelectronic series are collected in simple series expansions in power of Z. For the 444 computed SCF functions here reported, only the most important features are discussed.
Carbon—Carbon Spin-Coupling Constants in Characteristic CC-Bond Types
Authors: Frei K. , Bernstein H. J.
Published: January 2005

Carbon—carbon spin-coupling constants have been measured for a variety of types of CC bonds (in C13-enriched compounds), usually characterized by the different hybridizations of the C atoms. For hydrocarbons in which these bond types appear, the CC spin-coupling constant is proportional to the product of the s characters of the carbon atoms forming the bond in question. For several substituted hydrocarbons ``modified s characters'' may be found, from which the spin-coupling constants can be calculated by means of the same proportionality factor found for the hydrocarbons. The enhancement in CC spin-coupling constant due to pi electrons seems pronounced for double and triple bonds but less so in acyclic conjugated systems. A simple correlation of CC-bond distance and CC-coupling constant does not exist in general, but has been found for CC single bonds in hydrocarbons.
Triplet Spin Exchange in Some Ion Radical Salts
Authors: Jones M. T. , Chesnut D. B.
Published: January 2005

Studies of the effects of spin exchange on the electron paramagnetic resonance spectra of the ion radical salts (φ3PCH3)+(TCNQ)2-, (φ3AsCH3)+(TCNQ)2-, (Cs+)2(TCNQ)3= and (morpholinium)+(TCNQ)- have been carried out. Exchange parameters have been determined from all three limiting approximations relating to line width and line separation of the exchange-modified Bloch equations. While in general the exchange frequency ν can be expressed as ν=ν0 exp (— ΔE/kT), different values of ν0 and ΔE for a given material are obtained depending upon the limiting approximation employed. This ``anomalous'' exchange-narrowing behavior is discussed in terms of the current model for these triplet-state systems with particular emphasis upon the possible complicating features presented by the presumed existence of triplet excitons.
Absorption and Rotation of Light by Helical Polymers: The Effect of Chain Length
Authors: Tinoco I. , Woody R. W. , Bradley D. F.
Published: January 2005

The absorption of light and the rotation of polarized light near an absorption band is discussed for finite polymers. Only zero-order wavefunctions and first-order energies are considered for the polymer, which is treated as a rigid array of identical groups. The length dependence of the optical properties is calculated. The resulting equations are applied to the polypeptide α helix and 310 helix, polyadenylic acid, and dye complexes with these molecules.
Radiative Lifetime of I2 Fluorescence, B 3II0+u→X 1Σ0+g
Authors: Brewer Leo , Berg Robert A. , Rosenblatt Gerd M.
Published: January 2005

The radiative lifetime of the fluorescence of molecular iodine vapor, B 3II0+u(v′=26)→X 1Σ0+g, has been determined to be (7.2±1.0)×10—7 sec by using a phase fluorometer. Measurements on equilibrium vapor have been carried out over the pressure range 10—4 to 5 mm Hg. Results at the lowest pressures are considerably shorter than the true lifetime due to mixing of scattered, incident light with the fluorescence. This effect has been corrected for analytically. At higher pressures the measured lifetime is shortened by self-quenching. A Stern—Volmer plot of the data yields a self-quenching collision diameter for I2 of 11.3 Å. Measurements have also been carried out with a molecular beam of iodine vapor.
Isomerization of Nitrous Acid: An Infrared Photochemical Reaction
Authors: Hall Richard T. , Pimentel George C.
Published: January 2005

Nitrous and deuteronitrous acid suspended in nitrogen matrices at 20°K isomerize when illuminated with infrared light. Kinetic studies indicate that both the cis to trans and the trans to cis isomerizations occur. Filter studies show that a narrow range of frequencies is responsible, 3650–3200 cm—1 for HONO and 4100–3500 cm—1 for DONO. An isomerization mechanism is proposed that involves a highly efficient intramolecular transfer of energy between vibrational modes. The height of the potential barrier to isomerization is estimated to be 9.7±0.7 kcal/mole in the matrix and 8.7±1 kcal/mole for gaseous HONO. Comparison to methyl nitrite suggests that the bondings in these two molecules are quite similar and that the reported structure of methyl nitrite is incorrect.
Structure of the f6 Configuration with Application to Rare-Earth Ions
Authors: Ofelt G. S.
Published: January 2005

Free-ion energy-level schemes for the 4f6 and 4f8 configurations of Eu3+, Sm2+, and Tb3+ are given, which have been calculated from energy matrices including interactions among the three highest multiplicities. The values obtained for the parameters are F2 = 401 cm—1, ζ = 1320 cm—1 for Eu3+; F2 = 330 cm—1, ζ = 1050 cm—1 for Sm2+; and F2 = 434 cm—1, ζ = 1705 cm—1 for Tb3+. The wavefunctions and g values for levels to 40 000 cm—1 are tabulated for Eu3+ and Tb3+. Application of the free-ion wavefunctions to the Stark splitting of EuCl3 and TbCl3 is discussed.
An Experimental Contribution to the Problem of Diamond Synthesis
Authors: Bridgman P. W.
Published: January 2005

Pressure up to 30,000 kg/cm2, and in one case 45,000 kg/cm2, has been applied to graphite alone, or to graphite seeded with diamonds, at temperatures above 2000°C. In order to maintain temperatures for times of the order of seconds it is necessary to make the apparatus large, a commercial 1000-ton press being used to generate the pressure. Two methods were used, external heating with rapid transfer of the heated specimen to the pressure vessel and application of pressure, and internal heating by a modified thermite reaction set off by the pressure itself. No detectable transformation of graphite to diamond was found in any of the experiments. In the experiments with internal heating it was established that the rate of inversion of diamond into graphite at a temperature above the melting point of molybdenum is a function of the pressure. The individual points are considerably scattered, but the mean points lie roughly on a straight line running from 100 percent graphitization at 15,000 kg/cm2 to 0 percent at 30,000 kg/cm2. Linear extrapolation would, therefore, indicate reversible transition from graphite to diamond at higher pressures. It has not been possible to check this by direct experiment. The graphite formed from diamond under these conditions has the same x-ray structure as ordinary graphite, indicating that there are no previously unknown modifications of graphite in the present range to complicate the problem. In an appendix the theoretical evidence is considered and the conclusion drawn that linear extrapolation of the equilibrium curve between graphite and diamond from data up to 1000°C gives too high values of pressure in a range above 2000° where the velocities become appreciable, and that the equilibrium curve more probably curves upward.
Physical Properties and Cation Arrangement of Oxides with Spinel Structures II. Electronic Conductivity
Authors: Verwey E. J. , Haayman P. W. , Romeijn F. C.
Published: January 2005

The relations between the electronic conductivity of certain spinels and the arrangement of the cations in the crystal structure (see preceding paper) are studied. Several arguments favor the assumption that Fe3O4 contains both divalent and trivalent iron in the 16-fold position. The transition point in the neighborhood of liquid-air temperature is probably associated with an increased degree of order at low temperature in the distribution of the 8 electrons between the 16 Fe-lattice points per unit cell. The considerably increased conductivity below the transition points shows tetragonal anisotropy when the crystal is cooled in a magnetic field. The possible distributions of the electrons in the crystal at low temperature are discussed. In more complicated spinels, containing other metal atoms as well as iron in both the divalent and the trivalent state, the electronic interchange is more or less inhibited by the foreign metal atoms. The higher values of their resistance in comparison to that of Fe3O4 can be roughly described by an increased activation energy. The investigation of a number of substances with different arrangements of the cations shows that the activation energy (and therefore the electrical resistance) is lowest for those cases in which the electrons can travel, as in Fe3O4, along the Fe of the 16-fold position.
Calculation of Equilibrium Constants for Isotopic Exchange Reactions
Authors: Bigeleisen Jacob , Mayer Maria Goeppert
Published: January 2005

It is pointed out that the possibility of chemical separation of isotopes is a quantum effect. This permits a direct calculation of the difference in the free energies of two isotopic molecules. Tables and approximation methods are given which permit a rapid calculation of equilibrium constants if the frequency shifts on isotopic substitution are known. Several applications are discussed.
Dependence of Bond Order and of Bond Energy Upon Bond Length
Authors: Gordy Walter
Published: January 2005

A simple inverse square relation of the form, N=aR−2+b,(where N is the bond order, R is the bond length, and a and b are constants characteristic of any given pair of atoms) has been found to agree satisfactorily with the available values for bond orders. For CC bonds a and b are found to have the values 6.80 and −1.71, respectively; for CN they are 6.48 and −2.00; for CO they are 5.75 and −1.85. The available data on bond energies suggest a relation of the same form, E=lR−2+m,between bond energy E and bond length R, where l and m represent the characteristic constants of a given atomic pair.
Comparative Thermodynamic Properties of the Restricted Rotator and the Harmonic Oscillator
Authors: Halford J. O.
Published: January 2005

The differences between the thermodynamic properties of the restricted internal rotator and a defined harmonic oscillator are expressed within narrow limits as a function of the single variable V/RT, where V is the height of the restricting potential barrier. As a result, a single table with one column for each of the four thermodynamic functions can be used in conjunction with standard harmonic oscillator tables to give the restricted rotator properties. This approximation is accurate within 0.02 cal./mole/deg. for nearly all cases to which it might be applied, and it is shown to be improbable that rotators will be found for which the error would rise appreciably above this limit. The harmonic oscillator chosen for comparison has a slightly lower frequency than the limiting one approached by the restricted rotator at very high values of V/RT.
The Consistency of the Thermodynamic Data for Water Substance Vapor Phase to 550°C. Part VII
Authors: Keyes Frederick G.
Published: January 2005

A comprehensive investigation of the thermodynamic consistency of the large body of steam data above 150°C has been completed using the new thermodynamic scale information supplied by Professor J. A. Beattie to test the consistency of measured vapor pressures, specific volumes, enthalpies at saturation and superheat and specific heats. As an aid in correlation and unification a new form of equation of state is employed which has some validity through the critical region. The results of the investigation indicate a satisfactory state of thermodynamic consistency over the liquid-vapor range with respect to vapor pressures and saturation volumes deduced from the measured vaporization quantities using the Beattie corrections to the international temperature scale. The consistency test includes also verification of the accuracy and usefulness of the new functional relation for the vapor phase, p=F(v, T) whose parameters were determined from the measured superheat p-v-T data. The superheat enthalpy data to 550°C at zero pressure is however not consistent with the present theoretical information pertaining to Cp0. The computed enthalpies of the vapor to 550°C and pressures of 300 kg/cm2 are satisfactory provided an empirical correction term is subtracted from the theoretical values of Cp0. The accuracy of the Keenan-Keyes steam tables values of specific volume, pressure, and enthalpy is confirmed.
Diffusion in Binary Liquid Hydrocarbon Mixtures
Authors: Trevoy D. J. , Drickamer H. G.
Published: January 2005

Diffusion coefficients have been obtained for binary mixtures of paraffin hydrocarbons and for mixtures of paraffin hydrocarbons with benzene using a diaphragm cell. The results have been tested by the equations of Arnold, of Stokes and Einstein, and of Stearn, Irish, and Eyring. Of these only the semi-empirical relationship of Arnold gives satisfactory agreement with experiment.
On the Photographic Reciprocity Law Failure and Related Effects. I. The Low Intensity Failure
Authors: Katz E.
Published: January 2005

(1) The order principle (o.p.) states: ``The grains of an emulsion become developable in the course of an exposure in a given sequence independent of the exposure and development variables.'' This hypothesis appears to have a wide range of applicability. It forms an ideally simple link for correlating experimental isodense exposures and theoretical single grain response predictions. Moreover, in many cases where the o.p. is not strictly applicable, corrections can be derived (Section 12) which again make quantitative comparison of theory and experimental data possible.

(2) Extending ideas of Gurney, Mott, and Webb, a quantitative theory of the low intensity reciprocity law failure (l.i.f.) is developed, by analyzing the statistics of light absorption and the survival function of the electrons. Confrontation of various theoretical possibilities with experimental data selects the following basic assumptions: (a) A monoatomic Ag speck of sub-latent image is unstable against thermal agitation, but a diatomic speck is stable for most practical purposes; finally a triatomic speck is completely stable. (b) The energy required to set free an electron from a monoatomic speck (electron trap depth) is not the same for all traps. There must be a quasi-continuous distribution of depths (e.g. as given by formula (10)).

With these assumptions the theory describes satisfactorily the principal features in the shape of experimental l.i.f. curves. It is found that the l.i.f. slope varies systematically with grain size and the theory checks qualitatively with this result. The experimental temperature dependence of l.i.f. curves agrees satisfactorily with the theory.
Light Scattering in Multi-Component Systems
Authors: Stockmayer W. H.
Published: January 2005

A general equation is developed for the fluctuation of refractive index in multi-component systems, thus permitting the interpretation of turbidities for such systems in the absence of angular dissymmetry. Applications to several special cases of interest are presented.
The Infra-Red Spectrum of Hydrogen Peroxide
Authors: Giguère Paul A.
Published: January 2005

The absorption spectrum of hydrogen peroxide vapor was examined under low dispersion in the range 2–15μ. Four bands were observed at 3590, 2630, 1255, and 877 cm−1. The spectrum of the liquid also was measured between 2 and 21μ; it showed five bands at about 3400, 2780, 1350, 880, and 550 cm−1. The last one, which seems very diffuse, is presumably the torsional oscillation of the OH groups; as such it corresponds to a potential energy barrier of the order of 4 kcal./mole. New assignments are proposed in agreement with the model of Penney and Sutherland. Under high dispersion the second harmonic O–H frequency was found to consist of two identical hybrid bands at 7036.6 and 7041.8 cm−1, of which the rotational constant for the ground state is in perfect agreement with that already found for the third harmonic band. The explanation given previously for the doublet character of the vibrational levels of hydrogen peroxide is further substantiated by the present results. From both vibrational and rotational data the O–H distance in hydrogen peroxide appears to be slightly greater than that in water.
The Third Virial Coefficient for Non-Polar Gases
Authors: Bird R. Byron , Spotz Ellen L. , Hirschfelder J. O.
Published: January 2005

The third virial coefficient for non-polar gases has been calculated with great accuracy by means of punched-card techniques. The Lennard-Jones potential, with inverse twelfth-power repulsion and inverse sixth-power attraction, was used in the calculations. Excellent agreement between our computations and those of Kihara was obtained at very high temperatures; in the moderate temperature region our calculations agree moderately well with those of Montroll and Mayer and those of de Boer and Michels. A comparison with experimental data indicates fairly good agreement for the approximately spherical molecules argon, methane, and nitrogen. In other cases there are discrepancies suggesting deviations from the form of the interaction energy which we assumed. There is considerably difficulty in obtaining accurate third virial coefficients from the equation of state data. A method is suggested whereby the third virial coefficients for mixtures of gases may be estimated. The functions which are tabulated should be particularly useful for extrapolating the equation of state to very high temperatures, where no experimental data are available. The zero-pressure derivative of the Joule-Thomson coefficient with respect to pressure provides additional means for comparing our tabulated functions with experimental data, and the deviations are consistent with those discovered by comparison of the third virial coefficients themselves.
Rotation-Vibration Spectra of Diatomic and Simple Polyatomic Molecules with Long Absorbing Paths IV. The Spectrum of Methyl Fluoroform (CH3CF3) from 19μ to 0.7μ
Authors: Cowan R. D. , Herzberg G. , Sinha S. P.
Published: January 2005

The absorption spectrum of methyl fluoroform has been investigated with path lengths up to 30 meters in the region 19 to 0.7μ. Three of the fundamentals have been assigned differently from Thompson and Temple. Since the molecule is nearly a spherical top, the ⊥ bands show the same typical PQR structure as do the ∥ bands except when the Coriolis interaction constant ζ is large. This seems to be the case for the degenerate C–F stretching vibration ν9(e) and for most binary combinations involving it. The CH3 rocking vibration ν10(e) is split into two close components (separation 6 cm−1) a splitting that is here ascribed to the presence of three potential minima separated by low potential maxima. A large number of infra-red bands can be readily interpreted as binary combinations. The relative intensities of fundamentals and of overtone and combination bands are briefly discussed.
Intramolecular Reaction in Polycondensations. I. The Theory of Linear Systems
Authors: Jacobson Homer , Stockmayer Walter H.
Published: January 2005

For three types of linear polycondensing systems, equilibrium molecular size distributions, including rings as allowable species, are derived. Average molecular weights and amounts of ring and chain fractions are calculated therefrom. The fractions of rings are shown to increase with dilution, and with molecular weight. It is shown that beyond a critical dilution it is sometimes possible to obtain 100 percent yield of rings by driving the condensation to completion. Detailed calculations are made for two important cases corresponding to condensations of the decamethylene glycol-adipic acid type: (1) for equimolar amounts of the two monomers, and (2) unequal amounts, with one monomer type completely reacted.
The Microwave Spectrum and Structure of Methyl Acetylene
Authors: Trambarulo Ralph , Gordy Walter
Published: January 2005

From measurements of the J=1→2 rotational transitions of methyl acetylene and some of its isotopic modifications, the moments of inertia, IB (in the units 10−40 gm cm2), were found for the ground vibrational state: for CH3CCH, 98.1723; for CH3C13CH, 98.2132; for C13H3CCH, 100.9193; for CH3CC13H, 101.1992; for CH3CCD, 107.7234; and for CD3CCD, 124.5806. The centrifugal distortion constants, DJK, in mc/sec. are 0.161, 0.16, 0.16, 0.13, 0.14, and 0.09, respectively. The J=2→3 rotational transition of CH3CCH was also measured, and the distortion constant DJ was found to be 0.005 mc/sec. Four lines of CH3CCH corresponding to the J=1→2 transition and six lines for the J=2→3 transition in the excited vibrational state v10=1 and six lines for the J=2→3 transition in the excited state v9=1 were measured and interpreted according to Nielsen's theory of l-type doubling in symmetric tops. The calculated structure for the ground vibrational state is: C–H (acetylenic), 1.056A; C≡C, 1.207A; C–C, 1.460A; C–H (methyl), 1.097A; ∠HCH, 108°14′.
The Photolysis of Methyl Iodide
Authors: Schultz Robert D. , Taylor H. Austin
Published: January 2005

The photolysis of methyl iodide by 2537A radiation has been investigated under varying conditions of light intensity, temperature, iodine removal by rotating silver vanes and added carbon dioxide. Methane production is independent of temperature in the range 40°—100°C, directly dependent on the light, nearly independent of efficiency of iodine removal and is inhibited by carbon dioxide. Ethane production increases rapidly as the efficiency of iodine removal is increased. It is argued that methane results from the reaction, with iodide, of ``hot'' methyl radicals produced in the primary reaction. Ethane is formed from the association of cold methyl radicals. A possible decrease in ethane production with increase in temperature can be accounted for by the reaction of CH3+I2 having an activation energy of ∼1 kcal.
A Viscosity Equation for Gas Mixtures
Authors: Wilke C. R.
Published: January 2005

By application of the kinetic theory, with several simplifying assumptions, the previous equation of Buddenberg and the author has been modified to give a general equation for viscosity as a function of molecular weights and viscosities of the pure components of the mixture. Agreement of the equation with experimental data is demonstrated for a number of highly irregular binary gas systems and mixtures of three to seven components.
Vibrational Spectra of the Four Lowest Nitroparaffins
Authors: Smith Don C. , Pan Chi-Yuan , Nielsen J. Rud
Published: January 2005

The infra-red spectra from 2 to 22μ of nitromethane, nitroethane, 1-nitropropane and 2-nitropropane have been obtained for both vapor and liquid phases. The Raman shifts have been measured for the liquids, and for nitromethane the polarizations of the bands have been determined.

A satisfactory interpretation of the spectra has been obtained for nitromethane on the basis of assigned fundamental frequencies that agree with those proposed previously by Wells and Wilson, except for the B1 methyl rocking mode. The fundamental frequencies have not been determined for the other compounds, but the positions of the nitro group absorptions have been determined empirically.
Infra-Red and Raman Spectra of Fluorinated Ethylenes. III. Tetrafluoroethylene
Authors: Nielsen J. Rud , Claassen Howard H. , Smith D. C.
Published: January 2005

The infra-red absorption spectrum of gaseous tetrafluoroethylene between 2 and 22μ has been investigated with a prism spectrometer of high resolution, and the region from 20 to 37μ has been surveyed with a KRS−5 prism. The Raman spectrum of C2F4 gas has been photographed with a three-prism glass spectrograph of linear dispersion 15 A/mm at 4358A, and semiquantitative polarization measurements have been made. All of the 12 fundamental vibration frequencies have been determined, although with some uncertainty for three frequencies obtained from combination bands. The spectra have been interpreted in detail.
Force Constants for the Fluoromethanes
Authors: Pace E. L.
Published: January 2005

A calculation, involving vibrational potential functions of a general quadratic type restricted to small displacements, has been used to evaluate force constants, singly or in linear combination, for the fluoromethanes, and simultaneously, to confirm new assignments of the fundamentals of CF3H and CF2H2 arising from a detailed experimental study of their Raman spectra. The results indicate considerably greater bond strengths than expected from a mere extrapolation of the properties of analogous halogen derivatives. Particularly significant is the order of interaction terms involving the C–F stretching and the F–C–F bending motions of the molecules.
The Raman Spectrum of Vinylidene Fluoride
Authors: Edgell Walter F. , Byrd Willis E.
Published: January 2005

The Raman spectrum of vinylidene fluoride has been obtained in the liquid state at −100 to −125°C. The observed frequencies were assigned to the fundamental modes of vibration (and several combinations of these) with the aid of the infra-red data in the literature supplemented by some measurements in our laboratory. A normal coordinate treatment of the vibrations has been carried out using a simple valency force field plus one additional term depending upon the square of the change in the F–F distance. It is shown that the repulsion between the F atoms and between each F atom and the π-electrons of the double bond are of major importance.
Vibrational Intensities. I. Theory of Diatomic Infra-Red Bands
Authors: Crawford Bryce L. , Dinsmore H. L.
Published: January 2005

A rigorous treatment of the intensities of vibration-rotation absorption spectra of diatomic molecules is given, leading to explicit expressions relating the observed intensities of the fundamental and first two overtones to the appropriate coefficients in the expansions of the potential energy and the dipole moment.
The Concentration and Mobility of Vacancies in Sodium Chloride
Authors: Etzel Howard W. , Maurer Robert J.
Published: January 2005

The electrical conductivity of sodium chloride, containing cadmium chloride as an impurity, has been determined as a function of temperature. From these data it is calculated that the mobility of the positive ion vacancies is given by the equation μ=(19600/T)exp(−9860/T) cm.2/volt-sec. between 250°C and 400°C. The concentration of positive ion vacancies in a ``pure'' sodium chloride crystal was 1.0×1017 cm−3 and independent of temperature below 550°C.
On the Vibrational Spectra of Crystals
Authors: Bowers Wayne A. , Rosenstock Herbert B.
Published: January 2005

In order to check the accuracy of distributions of characteristic vibration frequencies in crystals as calculated by approximate methods proposed by various workers, the frequency distribution is calculated rigorously for a lattice for which this is possible, viz., a two-dimensional square lattice with vibrations perpendicular to the lattice plane. The calculation is then repeated by the use of the various approximate methods, and comparisons are drawn. The effect of using any of the approximate distributions in place of the exact one in the calculation of thermodynamic functions is illustrated by a calculation of the specific heat of this same crystal. Finally, an extension to three dimensions is discussed.
Light Scattering and Spectrophotometry of Colloidal Solutions
Authors: Doty Paul , Steiner Robert F.
Published: January 2005

During the past several years it has been demonstrated that the light scattered from dilute solutions of macromolecules or colloidal particles is intimately related to the weight, size, and interaction of the solute species. Theoretical developments and improved techniques have made possible the determination of the molecular weight, dimension and activity coefficient of a number of polymers and proteins in solution. In these investigations the intensity of light scattered at various angles from a monochromatic beam passing through the solution has been measured by means of specially designed photometers. However, it would appear that the equivalent information could be derived from a different means of observation—that of transmission measurements at various wave-lengths. If this possibility could be exploited the common techniques of spectrophotometry could replace the more specialized ones now used. The extent to which this is feasible is explored in this paper.

As a first step it is necessary to review some aspects of the scattering from small particles and the internal interference arising in the case of larger particles. This opportunity is taken to present a compilation of the scattering factors and the quantities derived from them, that is the dissymmetry and correction factor, in a more precise and convenient form than has appeared previously, because of the use to which they are put in the following sections. The calculations relating to the case of transmittance of solutions containing larger particles are then presented and in the final sections the application of both methods of observation to the determination of the molecular weight and size of samples of polystyrene and tobacco mosaic virus is reported.
Substituted Methanes: V. Infrared Spectra and Calculated Thermodynamic Properties for Some Trichloromethanes
Authors: Madigan John R. , Cleveland Forrest F.
Published: January 2005

Wave numbers and estimated relative intensities for the infrared absorption bands of CCl3H, CCl4, and CCl3Br and a percent transmission curve for CCl3Br in the region 400–3500 cm−1 are given. Probable values of the infrared wave numbers are established and compared with previously obtained Raman and calculated values. Assignments of the observed bands are made. Thermodynamic properties—heat content, free energy, entropy, and heat capacity—have been calculated from the spectroscopic and molecular structure data to a rigid rotator, harmonic oscillator approximation for nine temperatures from 298.16° and 1000°K.
The Ionization Potentials of the Deuterated Methanes
Authors: Lossing F. P. , Tickner A. W. , Bryce W. A.
Published: January 2005

The ionization potentials of methane, and of the four deuterated methanes, have been determined by electron impact using two 90° mass spectrometers with different types of sources. In addition, the ionization potentials of acetylene, deuterated acetylene, ethylene, and deuterated ethylene have been measured. A simple empirical method is used to obtain values which are reproducible to ±0.02 volt. For the methanes the ionization potential is found to increase with the number of deuterium atoms in the molecule, with a difference of 0.18 volt between the value for CH4 and that for CD4. Although this difference is found to be the same on each of the mass spectrometers, there is a difference of 0.11 volt between the absolute values of the ionization potential as determined for CH4 on the two instruments. In order to explain the difference between the ionization potentials of CH4 and CD4 on the basis of zero point energy differences, it is estimated that the force constants in the ionic state would need to have only about ¼ of their value in the ground state. Since this seems unreasonably low, it is suggested that the difference between the ionization potentials of the methanes, as measured by electron impact, may be caused, in part, by excess energy required for a ``vertical'' transition.
The Diffusion of Copper in Cuprous Oxide
Authors: Moore Walter J. , Selikson Bernard
Published: January 2005

Cuprous oxide strips were prepared by the oxidation of copper at 1000°C. The diffusion of radiocopper in this material at 800 to 1050° gave a self-diffusion coefficient, D=0.0436 exp(−36100/RT). Virtually the same D is obtained from experiments in which radiocopper is plated on copper strips, and the distribution of activity measured in the cuprous oxide film formed on oxidation in air. The observed D values are in accord with a predicted relation k/D=4, where k is the parabolic rate constant for copper oxidation. It is suggested that parabolic rate constants with large negative entropies of activation and low heats of activation may be due to grain boundary diffusion.
Vibrational Intensities. III. Carbon Dioxide and Nitrous Oxide
Authors: Eggers David F. , Crawford Bryce L.
Published: January 2005

Experimental intensity measurements can be combined with known harmonic and anharmonic potential constants of molecules to determine the variation of dipole moment with displacement. We have used a finite Taylor's series for both potential energy and dipole moment. The effect on intensity of frequency variation over the band is included explicitly for both parallel and perpendicular bands as in Fermi resonance between several bands. Intensities of two fundamental and four combination bands in carbon dioxide were measured. A complete second-order perturbation treatment of intensities was carried out for several bands, and the possible relation of the results to resonance structures is mentioned. The relative importance of electrical and mechanical anharmonicity is indicated.

Two cubic potential constants were determined for nitrous oxide from measured intensities, known rotational convergence, normal coordinates, and bond distances. Using these constants a first-order intensity treatment was carried out for several combination bands. The intensities of three fundamental and three combination bands were measured. Discrepancies in measured rotational convergences are mentioned, and possible lines are suggested for further work on nitrous oxide.
The Kinetics of the Forward and Reverse Reactions for the Vapor Phase Thermal Bromination of Chloroform
Authors: Sullivan John H. , Davidson Norman
Published: January 2005

The rates of the forward and reverse reactions for the homogeneous vapor phase thermal bromination of chloroform, CHCl3+Br2=CBrCl3+HBr(A), have been measured in the range 420–455°K and are given by −d(Br2)/dt=kf(CHCl3)(Br2)12[1+k2(HBr)/k3(Br2)]−1−kr(CBrCl3)(Br2)12[1+k3(Br2)/k2(HBr)]−1; where log10kf (liter/mole)12 sec−1=(−32,030/4.575T)+11.15, log10kr=(−32,930/4.575T)+12.70. The mechanism of the reaction is, M+Br2=2Br+MCl3CH+Br=Cl3C−+HBr→(1)←(2)Cl3C−+Br2=CCl3Br+Br→(3)←(4)where log10k1=(−9300/4.575T)+9.36, log10k4=(−10,200/4.575T)+10.91, (k2/k3)=0.040. The activation energies imply that the CH bond in CHCl3 is weaker than that in CH4 by 6+E2 kcal and the Cl3C–Br bond is weaker than the H3C–Br bond by 11+E2 kcal, where E2, the activation energy of reactions (2) and (3), is estimated to be ≤7 kcal.

The directly determined equilibrium constant for (A) agrees well with the kinetic value, Ke=k1k3/k2k 4; log10Ke=(900/4.575T)−0.15. From these data, for CCl3Br, ΔH°f,298°=−9.4 kcal, S°298°=80 eu S° was calculated as 80 eu from electron diffraction and spectroscopic data.

The equation for k4 is identical with that obtained in a previous study of the exchange of radioactive bromine between Br2 and CBrCl3, thus proving this free radical mechanism for the exchange reaction.
Binding Regions in Diatomic Molecules
Authors: Berlin Theodore
Published: January 2005

The concept of intramolecular binding is given a precise definition in a way that relates binding to the forces acting on the nuclei in a diatomic molecule. A consequence of the definition is that the space around the nuclei may be separated into binding and antibinding regions. These regions are described and they depend on the Coulomb law of force and on the ratio of the nuclear charges: the internuclear distance is simply a scale parameter. The influence of a single electron on the binding due to other electrons is briefly discussed.
An Absolute Theory of Solid-State Luminescence
Authors: Williams Ferd E.
Published: January 2005

The absorption and emission spectra of the thallium-activated potassium chloride phosphor at various temperatures has been computed theoretically. An ionic model is used. The radial charge densities of free Tl+ in the ground 1S0 state and in the excited 3P10 state are evaluated using the Sommerfeld modification of the Fermi-Thomas method for the core and the Hartree self-consistent field method for the two outershell electrons. From these wave functions and from the known ionic radius, polarizability, and repulsion energy constant ρ for the ground state, these parameters are evaluated for the Tl+ in the excited state interacting with Cl−. The variation of repulsion energy with interatomic distance a is shown to be equal to the variation of S2/a with a, where S is an overlap integral. The Tl+ in the 1S0 and the 3P10 states are substituted in dilute concentrations for the K+ in KCl, and the change in total energy of the system is calculated as a function of the change in the Tl+ nearest Cl− distance Δa with the condition that the remainder of the lattice rearranges to minimize the total energy. Madelung, exchange repulsion, van der waals, ion-dipole and coulomb overlap interactions are included. The absorption spectrum is computed by recognizing that the various atomic configurations of the system in the ground state have probabilities in accord with a Boltzmann function. The emission spectrum is similarly determined by summing over configurations of the system in the excited state. The computed spectra at various temperatures are found to be in good agreement with experiment. In addition, new insight is obtained on the detailed mechanism of solid-state luminescence.
The Concentration Dependence of the Viscosity of Solutions of Macromolecules
Authors: Riseman Jacob , Ullman Robert
Published: January 2005

The theory of the concentration dependence of the viscosities of solutions is developed for the dumbbell, rigid rod, and flexible chain macromolecules. Both the intramolecular hydrodynamic interactions between the monomer units of the same molecule and the intermolecular interactions between monomer units of different molecules are considered. The methods of Riseman and Kirkwood are applied throughout. The numerical result of the calculation for the dumbbell shaped molecule is compared with that obtained by Simha.
Diffusivity of Water Vapor in Some Common Gases
Authors: Schwertz F. A. , Brow Jeanne E.
Published: January 2005

From the measured rates of diffusion of water vapor into pure hydrogen, helium, methane, ethylene, nitrogen, oxygen, and carbon dioxide, the mutual coefficients of diffusion have been determined. Measurements were made at 34°, 56°, and 80°C and at atmospheric pressure employing the technique of Stefan.