bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrational Spectra of Inorganic Molecules. IV. Infrared Reflection Spectra of Liquid Lithium, Sodium, Potassium and Silver Chlorates, and Liquid Lithium Perchlorate
Authors: Wilmshurst J. K.
Published: January 2005

The infrared reflection spectra of molten lithium, sodium, potassium, and silver chlorates and lithium perchlorate have been obtained from 2900–200 cm—1 and the optical constants derived by the method of Robinson and Price. In both lithium and silver chlorate, the anion is not rotating freely about its threefold axis, and the point group symmetry of the cations about the chlorate ion does not contain a threefold rotation axis. In lithium perchlorate, it appears that the anion may be rotating freely. The presence of a lattice-like vibration band in each melt is apparent and a dielectric constant of 1.9–2.9 can be estimated from extrapolation of the low frequency refractive index data for liquid lithium perchlorate. Integrated band areas are recorded for all the materials investigated.
Molecular Rotation in Rare-Gas Crystals
Authors: Armstrong Robert L.
Published: January 2005

A study is made of the rotational states of dilute concentrations of small polar molecules trapped in a rare gas matrix at low temperatures (∼4.2°K). Under the assumption that exchange forces may be neglected, the remaining crystal interactions are found to produce only a slight splitting of those rotational states populated at the temperatures considered. It is suggested that this model provides an explanation of the free rotational effects observed in several recent experimental investigations of the spectra of such systems.
Nonequilibrium Thermodynamics of the Simple Moving Boundary Experiment
Authors: Bearman Richard J.
Published: January 2005

The usual equations for the moving boundary experiment are derived from the equations of the thermodynamics of irreversible processes. It is shown that the assumption that the partial molar volumes are constant through the liquid junction is implicit in the Lewis correction for the solvent velocity. The use of the correction has doubtful validity when there are appreciable volume changes upon mixing.
Dynamic Nuclear Polarization Studies of Charred Carbohydrates
Authors: Krebs J. J. , Thompson J. K.
Published: January 2005

The dynamic enhancement of proton spin polarization by pumping on ``forbidden'' electron-nuclear transitions is studied as a function of microwave power, O2 pressure, and magnetic field for a pair of low-temperature paramagnetic sucrose chars. The dependence of the electron spin-lattice relaxation time on O2 pressure is obtained for both samples. Comparison of the enhancement for a 405°C char with theory indicates that the electron spin resonance line is inhomogeneously broadened, and yields absolute values for the spin-spin and spin-lattice relaxation times of the spin packets. No definite fit could be made to the 605°C char data. The difference between the magnetic fields for maximum positive and negative polarization enhancement is anomalously small for the 405°C char.
Equilibrium Statistical Mechanics of Inhomogeneous Fluids
Authors: Stillinger Frank H. , Buff Frank P.
Published: January 2005

The excess thermodynamic and molecular properties induced in a classical single-component fluid by static external force fields are examined from several points of view. By utilizing the techniques of cluster theory, a local ``pressure,'' p̄(r), is constructed whose spatial integral yields directly and precisely the logarithm of the grand partition function, including the result of interaction with container vessel walls as well as other external fields (present, for example, in gravitational or centrifugal equilibrium). In particular, it is remarked that the problem arising from cluster integral dependence upon vessel volume in the usual imperfect gas theory is solved. The density expansion for p̄ is transformed into an integral involving a modification (Xg) of the well-known ``direct-correlation function,'' or non-nodal cluster function. Subsequent construction of local free energies provides a condition under which these quantities may be represented by uniform fluid values (evaluated at the local density), plus corrections involving just density gradients (or Laplacians). When the external force field is generated by a fixed set of particles, the formalism leads to new integral equations for molecular distribution functions. Comparison with similar previously known integral equations, in the pair distribution case, yields an explicit, formally exact, expression in terms of Xg for the troublesome ``elementary diagram cluster sum,'' which has prevented exact solution to the pair distribution problem. Finally, a new fluctuation theorem is derived, which relates the density derivative of surface tension for a fluid next to a planar wall of its vessel, to molecular distribution at this interface.
Dielectric Loss in the Liquid Crystal p-Azoxyanisole
Authors: Carr E. F.
Published: January 2005

The real and imaginary parts of the complex dielectric constant of the normal liquid phase of p-azoxyanisole were measured at a temperature of 140°C for a frequency range from 900 Mc to 24 kMc. A plot of the complex dielectric constant in the complex plane satisfies the requirements for a Cole—Cole representation reasonably well. The temperature dependence of the dielectric loss at a frequency of 6 kMc shows an absorption maximum in the neighborhood of the clearing point (135°C) for both the anisotropic and normal liquid phases. Measurements of the dielectric loss at frequencies 500 and 900 Mc indicate an increase in the dielectric loss as the sample changes from the anisotropic to the normal liquid phase. This change could not be established for measurements at other frequencies reported in this paper.
Electron Spin Resonance of a γ-Irradiated Single Crystal of N-Acetyl Methionine
Authors: Cipollini Ernesto , Gordy Walter
Published: January 2005

Free radicals produced by γ irradiation of single crystals of N-acetyl methionine have been investigated through their electron spin resonance patterns for different orientations in the magnetic field. Two chemically different free radicals have been found, both relatively stable at room temperature. One of them has an ESR pattern very similar to that of cystine dihydrochloride. Analysis of this resonance shows that the electron spin density is concentrated mainly on the S in a free radical which probably has the chemical form[Complex chemical formula]The g tensor for this radical is anisotropic with principal values 2.004, 2.029, and 2.064. An isotropic doublet hyperfine structure of 9.5-G spacing is observed. The second resonance has a complex, incompletely resolved, hyperfine structure with a total spread of about 26 G. Its almost isotropic g tensor with principal values from 2.002 to 2.005 indicates that the electron spin density is concentrated on a carbon. The free radical is believed to have the form[Complex chemical formula]but this structure is not proved.
ESR Study of Thio-indigo and Related Free Radicals
Authors: Bruin M. , Bruin F. , Heineken F. W.
Published: January 2005

Thio-indigo and various Cl, Br, CH3, OCH3, OC2H5, and C6H5 derivatives were converted into free radicals. The electron spin resonance of these radicals in acetone was studied under low and high resolution. The width at maximum slope of the unresolved spectrum is about 6 G. The spectra, consisting of hfs lines of 0.07–0.2 G width at a spacing of 0.1–0.4 G, could be consistently analyzed.

The relative unpaired-electron spin-density distribution in this type of molecule was determined. Cl and Br substituents do not give rise to observable splittings. Hyperconjugation appears to be effective for methyl substituents. For methoxy, ethoxy, and phenyl substituents a splitting due to the protons of these groups was found. The effect of substitution on observable electron spin densities is discussed.
Kinetics of Disappearance of Radicals Trapped in Irradiated Polyethylene
Authors: Smith W. V. , Jacobs B. E.
Published: January 2005

Development of a technique for determining the concentration of alkyl radicals trapped in irradiated polyethylene using radio-iodine is described. It is applied to study the kinetics of alkyl radical disappearance in irradiated polyethylene and polypropylene, and the kinetics are interpreted in terms of a simple model.

The radicals are assumed to be formed in isolated spherical spurs and rapidly attain an approximately uniform concentration within a spur. This concentration decreases with time due to second-order recombination accompanied by a diffusion-like expansion of the spur.

Recombination is increased by hydrogen and the diffusive expansion is increased by hydrogen and by preirradiation. Both processes are faster in polypropylene than in polyethylene. The number of free radicals per spur after the irradiation decreases with increase in radiation dose due probably to the effect of the hydrogen produced by irradiation.
Proton Magnetic Resonance Spectrum of HDO
Authors: Holmes John R. , Kivelson Daniel , Drinkard William C.
Published: January 2005

The proton magnetic resonance spectrum of the distinct species HDO has been observed in dilute solutions of H2O and D2O in carefully purified organic solvents. The HDO triplet is centered 0.030±0.003 ppm upfield from the H2O resonance. The proton—deuteron spin—spin coupling constant AHD is 1.1±0.1 cps. Approximate theories which provide explanations for the coupling constant and chemical shift are discussed.
Crystal Structure of the Carbon Tetrabromide p-Xylene Complex
Authors: Strieter Frederick J. , Templeton David H.
Published: January 2005

According to an x-ray diffraction study, crystals of the compound of carbon tetrabromide with p-xylene are orthorhombic, space group Cmcm, with a=8.48±0.03, b=8.89±0.03, and c=17.46±0.05 Å. With four molecules per cell, the density is calculated as 2.209 g cm—3. Each aromatic ring has a bromine atom on each face at a distance of 3.34 Å from the center of the ring. This configuration involving half of the bromine atoms is compatible with charge-transfer bonding. The structure consists of zigzag strings of alternate carbon tetrabromide and xylene molecules. Bond distances and angles within these molecules are normal with standard deviations of 0.02 to 0.05 Å for bond distances.
Computation of Statistical Complexions as Applied to Unimolecular Reactions
Authors: Schlag E. W. , Sandsmark R. A.
Published: January 2005

A method for the exact counting of statistical complexions based on a treatment by Fowler is suggested. In any such calculation for all complexions up to an energy E, a maximum energy ET is set in the interest of economy of time, beyond which an analytical function must be employed to obtain higher states. The commonly used function of Marcus and Rice is still too approximate unless ET is made exhorbitantly large and hence a new function is given which allows terminating the exact calculation at a reasonable energy and thus cut the value of ET by a factor of 3 or 4. Some monoenergetic reactions may proceed at an energy greater than ET above the activated complex, in this case a simple form of the complexion expression may be used directly in the formulation of a rate constant.
Radiation Decomposition of Aqueous Azide Solution
Authors: Shinohara Kenichi , Shida Tadamasa , Saito Nobufusa
Published: January 2005

When an aqueous solution of azide ion is irradiated with γ rays of 60Co, nitrogen gas, hydroxyl ions, and ammonia are produced. Hydrogen peroxide is not formed while hydrogen is produced equal to GH2w. The reaction mechanism may be well explained by assuming the oxidation of azide ion by the hydroxyl radical and the reduction by the hydrogen atom. Applying the expanding-spur theory of Ganguly and Magee to the system, all the features of the radiolysis are well understood. The number of water molecules initially decomposed was determined as 5.5. The rate constant of the reaction, OH+N3—=OH—+N3, was calculated to be 8×1010 liter mol—1 sec—1.
Quantum-Mechanical Calculation of Harmonic Oscillator Transition Probabilities. II. Three-Dimensional Impulsive Collisions
Authors: Mies Frederick H. , Shuler Kurt E.
Published: January 2005

The previous one-dimensional calculations of Shuler and Zwanzig for the vibrational transition probabilities for harmonic oscillators undergoing impulsive hard-sphere collisions with an incident atom have been extended to three dimensions. By the use of the modified wave number approximation, the three-dimensional scattering problem is related to the one-dimensional solution and the three-dimensional transition probabilities are obtained through numerical integration over the previously calculated one-dimensional probabilities. It is shown that vibrational transitions with | Δv | >1 are strongly allowed (in addition to the | Δv | = 1 transitions) in good agreement with the one dimensional impulsive collision results. The implication of this result on the mode and rate of the dissociation of diatomic molecules is discussed briefly.
Analysis of the NMR and Double-Resonance Spectra of the Isomers of N2F2
Authors: Noggle Joseph H. , Baldeschwieler John D. , Colburn Charles B.
Published: January 2005

The assignment of F19 NMR spectra of the two isomers of N2F2 is consistent with the assumption of trans and cis 1,2-difluorodiazine structures for these molecules. The qualitative features of the F19—{N14} double-resonance spectra, and a comparison of the F19 NMR spectra at 56.4 and 40.0 Mc/sec strongly favor a cis structure over a 1,1-difluorodiazine structure for the more reactive isomer. A comparison of the indirect N–F coupling constants for the two isomers indicates that the FNN angles are probably quite different for cis and trans N2F2.
Effect of Absorbed Water upon the Dielectric Properties of Certain Acrylic Ester Polymers
Authors: Scheiber Donald J. , Mead Darwin J.
Published: January 2005

The effect of absorbed water upon the dielectric properties of polymethylmethacrylate, polyethylmethacrylate, and polyethylacrylate is experimentally investigated over a temperature range from 70°C to —195°C and at frequencies between 100 cps and 200 kc. It is found in each case that the absorbed water gives rise to a discernible loss index peak in the low-temperature region (0° to —100°C). The 2.1% water absorbed in a specimen of polyethylacrylate acts as a plasticizer, apparently lowering the glass transition by 5C°. The facts that the apparent activation energy and the temperature location of the water induced peak changes with variations in the polymeric structure indicate that the induced loss peak is not to be identified with the loss peak found in ice, and furthermore suggests that the dielectric method can be employed to learn more about the water—polymer complex which is formed when water is absorbed into a polymer.
Quenching and Energy Transfer by the Same Substance
Authors: Furst Milton , Kallmann Hartmut P.
Published: January 2005

The quenching by 0-terphenyl of the gamma-ray induced fluorescence of 0-xylene/9,10-diphenylanthracene solutions does not give the usual linear dependence of I0/I on quencher concentration. The effect is ascribed to a quencher concentration-dependent energy transfer from the solvent to 0-terphenyl which has a finite transfer probability to the fluorescent solute. This interpretation is confirmed by the enhancement of energy transfer caused by the addition of 0-terphenyl to a solution of a fluorescent solute in tri-n-butylphosphate, a solvent having a very low transfer efficiency.
Infrared Spectroscopic Evidence for the Rotation of the Water Molecule in Solid Argon
Authors: Redington Richard L. , Milligan Dolphus E.
Published: January 2005

High-resolution spectra of H2O, HDO, and D2O suspended in solid Ar have been observed in the range 4°—27°K. Evidence has been obtained for the rotation of these species in Ar matrices. The majority of the observed lines are found to be in very good agreement with low-J transitions of the gas spectra, allowing for a small matrix shift. Transitions arising from both spin modifications of H2O and D2O have been observed and the observed intensities suggest that a large degree of spin equilibration has taken place. A small contamination of O2 may be responsible for this. A perturbation of one of the rotational levels of ν2—H2O is discussed.
Nucleation of Vapor Deposits
Authors: Walton D.
Published: January 2005

The size of the critical nucleus in the formation of metal deposits from the vapor is very small, probably containing 10 atoms or less. For nuclei of this magnitude the uncertainties concerned with the liquid-drop model and the concept of surface energy in the Volmer and Weber and Becker and Doring treatment of nucleation become serious. An expression for the density of clusters of atoms is developed using statistical mechanics. From this an expression for the nucleation rate is derived on a kinetic basis. It is also observed that certain orientation effects in the deposit can be explained if the small size of the critical nucleus is taken into account.
Valence-Bond Studies of the Dependence upon Substituents of C13–H and Si29–H Coupling
Authors: Juan Cynthia , Gutowsky H. S.
Published: January 2005

An interpretation is presented for the additivity of substituent effects on the C13–H coupling constant, which has been observed previously in the high-resolution NMR spectra of substituted methanes. Each atom or group X is assigned a characteristic ``affinity'' for s character in the carbon hybrid orbital of the C—X bond. Distribution of s character among the carbon orbitals in accord with the relative s affinities of the four substituents leads to the observed additivity relation provided that the total s character is conserved. The valence-bond approach used with this model gives a linear relation between the s character of the carbon hybrid orbital involved in the C–H bond (αH2) and the observed C13–H coupling constant (JCH=500 αH2). Also, it allows the determination of the s character of the other carbon orbitals. The dependence of the s character of the C—X bond on the electronegativity of X is discussed in terms of electron spin and charge correlation. It is noted that the hybridization changes should affect not only JCH but also JHH, which is consistent with the observed proportionality between JCH(CH3X) and the cis and trans H–H coupling constants in CH2=C13HX.

The treatment developed for methanes has been extended to JCH in substituted ethylenes and to the Si29–H coupling in silanes. For the former, introduction of the s-electron affinities, obtained from the values of JCH(CH3X) observed for the substituted methanes, leads to the result that JCH(CH2=C13HX) = JCH(CH2=CH2)+43 [JCH(CH3 X) – JCH(CH4)]. Values predicted in this manner are systematically larger than those observed, which implies that there is a small, negative π-electron contribution of 5 to 10 cps to JCH(CH2=C13HX). Such a contribution is compatible with current theories for proton and C13 hyperfine splittings in ESR spectra of free radicals. The Si29–H coupling constants observed in substituted silanes exhibit large, systematic deviations from the simple additivity found in the methanes. These deviations are explicable qualitatively in terms of changes in the Si–H-bond polarity.
Absorption Spectrum of Nd3+ in LaBr3
Authors: Richman Isaac , Wong Eugene Y.
Published: January 2005

The absorption spectrum of 0.5 mole % Nd3+ in a LaBr3 single crystal was obtained and most of the crystalline field Stark levels identified. The spectrum is very similar to that obtained from Nd3+ in LaCl3 and, in fact, the crystalline field parameters that fit LaCl3 to 5 cm—1 fit LaBr3 to 7 cm—1. The major difference in the two spectra is a general shift of levels to the red in the LaBr3. This is similar to the spectra of Pr3+ in the two crystals discussed previously [E. Y. Wong and I. Richman, J. Chem. Phys. 36, 1889 (1962)]. The explanation for this shift in both Pr3+ and Nd3+ spectra is probably the same.
Absorption Spectra of Gaseous Halide Ions and Halogen Electron Affinities : Chlorine, Bromine, and Iodine
Authors: Berry R. Stephen , Reimann Curt W. , Spokes G. Neil
Published: January 2005

Absorption spectra have been taken of partially dissociated vapors of chloride, bromide, and iodide salts of rubidium and cesium. The salts have been heated by shock waves. Continuous absorption spectra characterized by sharp thresholds are attributed to the ions Cl—, Br—, and I—. The low-energy thresholds for the three ions fall at approximately 3424, 3685, and 4040 Å, respectively. From the threshold wavelengths and appropriate small environmental corrections, the electron affinities of chlorine, bromine, and iodine are determined to be 3.628±0.005, 3.378±0.005, and 3.078±0.005 eV, respectively.
Calculation of Crystal-Field Splittings of Sm3+ and Dy3+ Levels in LaCl3 with Inclusion of J Mixing
Authors: Axe J. D. , Dieke G. H.
Published: January 2005

Calculations of the crystal-field splitting of the low lying sextet multiplets of the f5 and f9 configurations in a field of C3h symmetry have been performed and the results are compared to experimental data on Sm3+ and Dy3+ in LaCl3. The effect of inclusion of terms coupling different free ion J manifolds is examined, and several interesting features which arise from this effect are discussed. For Sm3+ 39 observed crystal-field levels are reproduced with a standard deviation of ±3.2 cm—1 with the crystal-field parameters B20 = A20〈r2〉 = 80.85 cm—1, B40 = —22.75 cm—1, B60 = —44.39 cm—1, and B66 = 425.7 cm—1. For Dy3+ 39 observed levels are reproduced with a standard deviation of ±2.7 cm—1 with the parameters B20 = 91.30 cm—1, B40 = —38.97 cm—1, B60 = —23.17 cm—1, and B66 = 257.8 cm—1. The remaining small discrepancies between calculated and observed levels can probably be attributed to inadequate free-ion wave functions.
Ionization of the Methane Molecule by Electron Impact
Authors: Inokuti Mitio
Published: January 2005

The cross section for ionization of the methane molecule by impact of fast electrons is evaluated by means of the Born approximation. Use is made of a single-configurational wave function set up from analytic one-center MO's for the description of the electronic ground state of the molecule. The wave function of the ejected electron resulting from ionization is approximated by a Coulomb continuum function. The calculated cross section is compared with experiment. The calculated momentum distribution of the ejected electron has a maximum at a very low momentum.
ESR Study of Free Radicals Produced by Irradiation in Benzene and Its Derivatives
Authors: Ohnishi Shun-ichi , Tanei Tadayoshi , Nitta Isamu
Published: January 2005

Benzene and some of its mono- and di-substituted derivatives including toluene, chlorobenzene, benzoic acid, phenylcyclohexane, polystyrene, and xylenes were irradiated in their solid state at —196°C. After the irradiation their ESR spectra were measured at that temperature and also up to their melting points. The spectrum of benzene consisted of two components. One was a main triplet (splitting 47.5 G) with a quartet substructure (splitting 10.4 G), each quartet showing further fine (probably triplet) splitting of ∼2.5 G, and it was assigned to cyclohexadienyl radical C6H7·. When the temperature was raised this spectrum showed a marked narrowing from about —173°C where the C6 reorientation of the benzene molecule sets in. At the same time the radical began to diminish, and decayed out at —32°C, which is far below the melting point. The other component of the spectrum was a singlet of 25-G width at the maximum slope, and was assigned to phenyl radical C6H5·. This component decayed out at 0°C. The spectra of the benzene derivatives were triplet, quite similar to that of benzene, and were interpreted to be due to the radicals produced as a result of hydrogen addition to the benzene ring. The GR values determined at —196°C for benzene, cyclohexane, their 1:1 mixture, and phenylcyclohexane were 0.14, 5.04, 2.4 and 0.66, respectively. It is concluded that in the case of phenylcyclohexane some energy-transfer process may occur from the cyclohexyl ring to the phenyl ring.
Motion in Polyethylene. III. The Amorphous Polymer
Authors: Wunderlich Bernhard
Published: January 2005

The heat capacity of completely amorphous polyethylene is separated above 250°K into contributions from the optical vibrations, the acoustical vibrations and hindered rotations, the trans—gauche equilibrium, and the hole equilibrium. The glass transition interval which stretches from 250° to 120°K can be explained by a separate freezing in of the hole equilibrium at 237°K and a slower freezing in of the trans—gauche equilibrium, which is completely arrested at 120°K with 0.165 of the bonds left in the gauche position.
Relative Signs of Geminal and Vicinal Coupling Constants in 1,1,4,4-Tetramethylcyclohexyl-cis-2,6-Diacetate
Authors: Rao B. D. Nageswara , Baldeschwieler John D. , Musher J. I.
Published: January 2005

The proton—proton double resonance spectrum of 1,1,4,4-tetramethylcyclohexyl-cis-2,6-diacetate is analyzed using a Hamiltonian made stationary by transformation to a rotating coordinate system. Frequency-sweep spectra are calculated by numerical diagonalization of the Hamiltonian, and the field-sweep spectra are obtained by a graphical method. The geminal and vicinal proton spin—spin coupling constants in this molecule are opposite in sign.
Interactions between Ordinary Vibrations and Hindered Internal Rotation. I. Rotational Energies
Authors: Kirtman Bernard
Published: January 2005

The effect of vibration-hindered rotation interactions on the rotational energy levels of molecules containing a symmetric internal rotor has been re-examined theoretically. The complete Hamiltonian has been derived and includes terms which are due to Coriolis coupling and to the explicit dependence of the kinetic energy on the angle of internal rotation.

Over-all and internal rotation are separated from vibration, in zeroth order, by means of the Eckart and Sayvetz conditions. Difficulties in previous treatments are traced back to the application of these conditions. For each vibrational state, an approximate Hamiltonian for over-all and internal rotation is obtained by a Van Vleck perturbation treatment in which torsional denominators are assumed to be negligible. A correction for these denominators is determined by taking the first term in a power series expansion.

A preliminary transformation, similar to that described by Hecht and Dennison, is used to remove zeroth-order coupling between the angular momenta of over-all and internal rotation. Simple product wavefunctions, then, form a suitable basis for evaluating first-order energy corrections due to higher-order coupling of internal and over-all rotation.

Symmetric rotors, slightly asymmetric rotors, and asymmetric rotors with relatively high barriers to internal rotation are each treated separately. Empirical frequency expressions for rotational transitions of all three types of molecule are given. The symmetric rotor formula is identical in form to Kivelson's but the empirical constants must be interpreted differently. A symmetric rotor analysis was done on CH3SiF3 and CD3SiF3. K→K, J—1→J transitions of slightly asymmetric rotors obey a particularly simple frequency relation. Two groups of asymmetric rotor transitions are tractable: (1) The 00,0→10,1, ½[11,0→21,1+11,1→21,2], and 22,1→32,2 transitions, where the designation of levels is for a prolate rotor, and (2) transitions between the two members of an asymmetry doublet.
Effect of Partial Draining on the Intrinsic Viscosity of Flexible Macromolecules
Authors: Hearst John E.
Published: January 2005

This calculation applies the theory of Zimm to the problem of the partial draining of Gaussian coils. Zimm's free-draining eigenfunctions are assumed to be sufficiently accurate as eigenfunctions in the nondraining limit, and the function required for the intrinsic viscosity is tabulated as a function of a draining parameter in a manner similar to that of Kirkwood and Riseman. The use of a scaling factor as proposed by Kurata and Yamakawa is shown to give low results with a maximum error of the order of 10%. The first relaxation time is tabulated and found to be a rather weak function of the draining parameter.
Nitric Oxide Bands near 1 μ in Shock-Heated Air
Authors: Wurster Walter H. , Treanor Charles E. , Thompson Herbert M.
Published: January 2005

The banded radiation from a strong radiating system has been observed in the near-infrared spectrum of shock-heated air. The dependence of the radiant intensity upon species concentration and temperature, as well as an estimate of the oscillator strength, indicate that the radiation results from transitions between excited electronic states of nitric oxide. This system is shown to be a significant contributor to the infrared emission spectrum of high-temperature air.
Thermal Study of Crystal Field Splittings in Erbium Ethylsulfate
Authors: Gerstein B. C. , Penney C. J. , Spedding F. H.
Published: January 2005

The heat capacities of erbium ethylsulfate and yttrium ethylsulfate have been measured in the range 12°—300°K. The magnetic contribution of the erbium ion has been evaluated with the help of an assumption concerning the difference in lattice contributions between the erbium and yttrium salts. This contribution agrees, to within experimental error, with the experimental energy level scheme for the 4I15/2 state published by E. H. Erath [J. Chem. Phys. 34, 1985 (1961)].
Computation of Asymmetric Rotator Constants from Energy Moments. IV
Authors: Genusa Vincent A. , Parker Paul M.
Published: January 2005

The energy-moment procedure is used to develop expressions which are helpful for the analysis of centrifugal distortion effects in asymmetric top spectra. In principle, all first-order distortion constants can be evaluated if a sufficient number of transition frequencies are available from experiment.
Proton Chemical Shifts and Pi-Electron Distributions in the Hydroxy-Benzenes
Authors: Schug John C. , Deck Joseph C.
Published: January 2005

The proton magnetic resonance spectra of phenol, hydroquinone, catechol, resorcinol, and pyrogallol have been studied, and the chemical shifts of the aromatic protons relative to benzene determined. The chemical shifts for the isolated molecules were obtained by making measurements in two solvents and extrapolating to a medium of unit dielectric constant. The electric fields at the protons from the C–O and O–H bond dipoles were calculated, and their contributions to the proton chemical shifts were removed by employing the approximate relation derived by Buckingham. It was assumed that the remaining parts of the chemical shifts were due to changes in the pi-electron distributions. Hückel molecular orbital calculations were performed, and it was shown that the corrected chemical shifts, δi, can be expressed in the form δi=aqi+a′qi′+a′′qi′′,where qi is the excess number of pi electrons on the ith carbon atom, qi′ is the sum of those on the two adjacent carbon atoms, and qi″ is the sum of those on any oxygen atoms ortho to the ith proton. The constants a, a′, and a″ were evaluated by fitting the chemical-shift data with a least-squares procedure. The derived constants depended sensitively on the values chosen for the necessary Coulomb and resonance integrals. It was not possible to conclude whether sigma inductive effects should be included or not, so it is suggested that they be omitted for the time being. By requiring reasonable values for the constants, i.e., a≅7, a′≅1, and a″≅0 ppm/electron and searching for closest agreement between calculated and observed chemical shifts, it was possible to choose as the most appropriate molecular orbital parameters, αO=αC+0.75 βCC, and βCO=1.0 βCC.
Infrared Spectrum of Methylsilylacetylene
Authors: Robinson Dean W. , Reeves R. Bruce
Published: January 2005

The compound methylsilylacetylene has been prepared for the first time and its vibrational spectrum has been obtained and assigned. All but two of the fundamentals have been identified. The rotational Q branches of the perpendicular bands have been resolved for the three group modes of SiH3, and a comparison of the Coriolis coupling constants with those of other silyl-containing molecules indicates a low or vanishing barrier to internal rotation. The relative intensities of the Q branches further supports this observation.
Charge Exchange between Gaseous Ions and Atoms
Authors: Rapp Donald , Francis W. E.
Published: January 2005

A calculation of symmetric resonant charge exchange cross sections has been made for a selection of atoms in the velocity range where the impact parameter method is applicable. Cross sections for other atoms can be estimated by interpolating in terms of their ionization potentials. The results are in fair agreement with experiment. A similar calculation has been attempted for asymmetric nonresonant charge exchange processes. The approximations used are more restrictive in this calculation, the calculations being only semiquantitative in nature. The cross section of an asymmetric charge exchange process is determined in terms of the ΔE of the reaction and the ``average'' ionization potential of the two atoms. The results are qualitatively in agreement with experiment. A very brief discussion of approaches for extrapolating data to lower velocities, where the rectilinear orbit impact parameter method is not applicable, is given.
Reactions of Excited Butane Molecules
Authors: Beck D. , Niehaus A.
Published: January 2005

To study the unimolecular reactions of highly excited molecules, a method for detection and analysis of the uncharged fragments has been reported. It uses excitation of the molecule by electron impact and—after about 10—5 sec—ionization and analysis of the fragments in a mass spectrometer.

This paper presents results for the butane molecule. The actually determined quantities are the relative concentrations of the uncharged fragments in the ion source. They are obtained with an average error of 20% and may be used to infer the relative probabilities (cross sections) of production from the molecule. The latter, constituting the neutral spectrum of the molecule, are compared quantitatively with the ion spectrum. A quantitative scheme for the decay of an excited butane molecule is set up and discussed. It is found that: (1) Radical production from the decay of the molecule occurs very seldom; (2) Excitation, high enough to be followed by break up, is about equally probable for ionized and neutral molecules.

For the radicals C3H5, C3H3, C2H5, CH3, CH2, and H, which originate from the decay of the molecule ion, the ionization potentials are reported.
Electrical Conduction in Nonstoichiometric α-Nb2O5
Authors: Janninck R. F. , Whitmore D. H.
Published: January 2005

The electrical conductivity of nonstoichiometric α-Nb2O5—x was measured as a function of both the composition over the range 0.001≤x≤0.137 and the temperature from 77° to 1270°K. The temperature dependence of the conductivity of a specimen of fixed oxygen content may be rationalized on the basis of excitation of electrons from donor centers at low temperatures and an exhaustion region at high temperatures. The conductivity data are interpreted in terms of an oxygen ion vacancy defect capable of trapping two electrons which can be thermally excited into a narrow 4d conduction band. Assuming this type of defect, an estimate of the mobility of the electrons in the conduction band is made from the conductivity data in the exhaustion region.
Molecular Vibrations and Structure of High Polymers. III. Polarized Infrared Spectra, Normal Vibrations, and Helical Conformation of Polyethylene Glycol
Authors: Miyazawa Tatsuo , Fukushima Kunio , Ideguchi Yoshiko
Published: January 2005

The polarized infrared spectra of highly oriented crystalline films of polyethylene glycol were measured in the region 3500–400 cm—1. Five parallel bands and eleven perpendicular bands due to the fundamental vibrations were observed in the region 1500–600 cm—1. From the analysis of these bands, the polyethylene glycol chain was found to belong to the dihedral group and have twofold axes intersecting the helix axis at right angles. The structural models of polyethylene glycol were discussed by the use of the equations for the helical parameters (the second paper of this series). The most likely model (TGT) contains seven repeating units and two helical turns per fiber period of 19.25 Å. The internal rotation angles for this model are calculated to be 60° for the C–C bond and 191.5° for the C–O bond. The A1, A2, and E(θ) normal vibrations of polyethylene glycol were calculated by the general method for treating helical polymers (the first paper of this series). The normal vibrations of p-dioxane were also calculated. The modified Urey—Bradley force field was used for the calculations and the potential constants were transferred from polyethylene, dimethyl ether, and propyl alcohol. The frequencies calculated for the TGT model agreed well with the observed frequencies. The potential energy distributions were also calculated and the nature of the infrared bands was elucidated. The far-infrared spectra of crystalline films were also measured in the region 600–50 cm—1 and two parallel bands and two perpendicular bands were observed. The skeletal normal vibrations of the TGT model were also calculated, taking into account the torsional potential field. The torsional constants correspond to a potential barrier of 3 kcal/mole. The calculated frequencies agreed well with the observed, providing substantial support for the TGT model. The infrared bands in the region of 3000 cm—1 were assigned to the C–H stretching modes and the infrared active combination vibrations.
Study of the Reaction of K with HBr in Crossed Molecular Beams
Authors: Beck D. , Greene E. F. , Ross J.
Published: January 2005

The reaction of K+HBr→KBr+H is studied by measuring elastic and reactive scattering in crossed molecular beams. The K beam is well collimated and made nearly monoenergetic by a mechanical velocity selector. The HBr effuses from a low-temperature source as a diverging beam. Angular distributions of KBr at fixed K energy and the variation of the total chemical reaction cross section with initial relative energy indicate a reaction threshold energy below 0.4 kcal/mole and a nearly constant reaction cross section at higher energies up to about 4.5 kcal/mole. The difference between the measured scattered K and the K intensity calculated classically for hypothetical nonreacting molecules scattered elastically leads to a determination of the variation of the probability of reaction with impact parameter or with the potential energy at the distance of closest approach in the collision. The influence of the requirement of conservation of angular momentum on the probability of reaction is evident. At impact parameters below about 3.5 Å, 90% of the collisions lead to reaction. Above threshold the reaction cross section is found to be about 34 Å2.
Microwave Spectrum of Chlorine Dioxide. IV. Determination of Centrifugal Distortion Effects and Potential Constants
Authors: Pillai M. G. Krishna , Curl R. F.
Published: January 2005

A reanalysis of the microwave spectrum of chlorine dioxide, taking into account the effects of centrifugal distortion, has been carried out. When the centrifugal distortion constants are forced to be consistent with the harmonic vibrational frequencies obtained from the visible spectrum, 18 rotational transitions of Cl35O2 are fitted with a standard deviation of 2.5 Mc.

The rotational and force constants obtained are A=52079.5±0.8 Mc, B=9952.23±0.15 Mc, C=8333.99±0.13 Mc, fd=7.0175±0.003×105 dyn cm—1, fα/d02=0.6514±0.002×105 dyn cm—1, fdα/d0=0.0064±0.0008×105 dyn cm—1 and fdd=—0.1699±0.003×105 dyn cm—1. The force constants were used to calculate the distortion shifts for the Cl37O2 molecule and the rigid-rotor frequencies for 7 rotational transitions of Cl37O2 were fitted with the rotational constants.
Theory of Surface Specific Heats of Solids
Authors: Stratton R.
Published: January 2005

It is shown that the result of a recent calculation by M. Dupuis, R. Mazo, and L. Onsager [J. Chem. Phys. 5, 1452 (1960)] for very low temperatures, is in exact agreement with the low temperature limit of an earlier treatment [Phil. Mag. 44, 519 (1953)] by the present author after correction of two minor errors in the latter calculation.
Absolute Infrared Intensities in Crystalline C2H4 and C2D4
Authors: Wieder Grace M. , Dows David A.
Published: January 2005

Absolute infrared intensities of the ungerade fundamentals of crystalline C2H4 and C2D4 have been measured under high spectral resolution at 63°K and compared with the available intensity data in the gas phase. The intensity changes from gas to solid vary considerably among modes of the same symmetry species. Attempts to predict the transfer of intensity among certain vibrational modes in the crystal by an intermolecular hydrogen repulsion coupling mechanism have met with limited success. Intensity sum rules are discussed.
Density and Expansivity of Solid Xenon
Authors: Sears D. Richard , Klug Harold P.
Published: January 2005

Lattice parameters, densities, and thermal expansion coefficients of polycrystalline xenon are reported for the temperature range from 5.5° to 75°K. A value of 6.1317±0.0005 Å is obtained for the lattice parameter extrapolated to 0°K. Preferred orientation and annealing effects in frozen gases are discussed briefly with reference to matrix isolation methods.
Sequential Filling of a Line by Intervals Placed at Random and Its Application to Linear Adsorption
Authors: Mackenzie J. K.
Published: January 2005

A line with integral length n is filled sequentially at random with nonoverlapping intervals of integral length a, their end points having integer coordinates. It is shown that, as n tends to infinity, the average value of the length left vacant tends asymptotically to (n+a) A1(a) while its variance tends to (n+a) × aA2(a), where A1(a) and A2(a) are constants whose values are given numerically for all a; these asymptotic results are accurate to four significant figures for n/a>8. Some results are also given for the (average) relative numbers of vacant spaces of length i=0, 1,..., a—1.

With certain restrictions, the above results can be applied to the complete adsorption of linear molecules which when once adsorbed remain fixed in position in the line troughs of suitable crystal surfaces such as (110) on an fcc crystal or (112) on a bcc crystal. These restrictions concern the way in which the molecule sits in equilibrium on the underlying crystal sur face.
Bond Character in XYM-Type Molecules: Chlorine—Oxygen Compounds
Authors: Wagner E. L.
Published: January 2005

An internally consistent LCAO—MO method is presented for determining the bond characters in XYM-type molecules involving second-row elements. This treatment is based on Moffitt's ``atoms-in-molecules'' method, but utilizes valence-state electronegativities of the atoms involved rather than the generally unavailable valence-state ionization potentials and electron affinities. Results from the two methods compare favorably for C–O and S–O compounds.

Application of the method to the oxygen compounds of chlorine shows that the chlorine atom 3d orbitals may significantly participate in the π bonding. A successful correlation between the calculated total π-bond orders and the Cl–O bond stretching force constants is obtained when a reasonable set of β(dπ) values is used, and the observed properties of the compounds are compatible with the calculated bond characters.
Some Theoretical Aspects of Bonding in N–F Compounds
Authors: Kaufman Joyce J.
Published: January 2005

A separation of the effects of substituent groups into distinct σ and π contributions and the influence of the σ and π contributions on Hamiltonians and wave functions of various cores has proved useful for describing several diverse phenomena in N–F compounds.

(1) The ``anomalous'' difference in bond strengths in NF3 and NF2 where the N–F bond in NF3 is weaker than that in NF2.

(2) The nonconstancy of the δK value for F in ionization potentials of NF3 and CF3, whereas other substituent group effects were constant.

(3) The similarity between the effect of F on ionization potentials of NF2 and of CF3.
Microwave Spectrum of Chlorine Dioxide. III. Interpretation of the Hyperfine Coupling Constants Obtained in Terms of the Electronic Structure
Authors: Curl R. F.
Published: January 2005

The hyperfine coupling constants obtained from the microwave spectrum of chlorine dioxide are discussed in terms of the electronic structure of chlorine dioxide. It is found that these constants can be reasonably interpreted in terms of a simple molecular orbital model of chlorine dioxide in which the odd electron is in a b1 antibonding orbital.
Theory of Paramagnetic Excitons in Solid Free Radicals
Authors: Lynden-Bell Ruth M. , McConnell Harden M.
Published: January 2005

A linear chain of S=½ molecules with alternating intermolecular exchange integrals is used as a model to investigate the properties of paramagnetic excitons in solid free radicals from a theoretical point of view. The spin exchange Hamiltonian for the problem is H=Σν(JS2ν·S2ν+1+J′S2ν·S2ν−1),when J>J′>0. In the limiting case that J≫J′, the exciton bandwidth is simply J′. For this case we have calculated (a) the fine-structure splitting of the paramagnetic resonance of isolated (noninteracting) excitons, (b) wave functions for a free exciton gas of arbitrary excitation density, (c) the magnetic susceptibility of the exciton gas, and (d) first-order exchange interactions between excitations.

In the case that thermal energies are much larger than the exciton bandwidth, exchange interactions between excitations are simply proportional to the excitation concentration, but at temperatures corresponding to thermal energies less than the bandwidth, there is a ``Fermi hole'' type repulsion between the excitons that reduces the exchange interaction. In fact, the excitons behave somewhat like Fermi particles, except their number is not constant (depending on the temperature), and only one exciton may occupy a given momentum state, irrespective of spin. Also, when the exciton bandwidth is comparable to or larger than kT, it is predicted that the exciton fine-structure splitting will be temperature dependent.

When J′ becomes comparable to J, then the elementary exciton takes on a complicated, distributed spin structure.
Equation of State of Classical Hard Spheres at High Density
Authors: Salsburg Z. W. , Wood W. W.
Published: January 2005

Under certain conditions, an asymptotic expression for the equation of state of a classical mechanical system of N ν-dimensional (ν=1, 2, or 3) hard spheres confined in a volume V is obtained in the form pVNkT=ν(1–1/N)(V/V0)−1+O(1).This expression agrees with the leading term in V/V0—1 of the usual free-volume approximation for N = ∞. The conditions under which this conclusion is established are a restriction to a finite number of molecules N with periodic boundary conditions, and the requirement that as V→V0 the accessible configuration states approach a close-packed configuration whose coordination number c satisfies the requirement c≥2ν−2(ν−1)/N.Such a limiting configuration, from which only an infinitesimal region of configuration space is accessible under an infinitesimal expansion, is called a stable configuration; the above restriction on the coordination number is a necessary condition for stability. The difficulties which appear as N→∞ are indicated.
Note on the 5Σ+g State of N2
Authors: Carroll P. K.
Published: January 2005

An approximate potential curve for the 5Σ+g state of the nitrogen molecule is proposed. The curve is based on the parameters De=1100 cm—1, ωe=650 cm—1, and re=1.55 Å, which were derived from a consideration of recent afterglow measurements and from an examination of the predissociations in the a1Πg and B3Πg states. The main features of the potential are in keeping with the trend of the 5Σ+g curve as proposed in the most recent theoretical work (see the accompanying paper by R. S. Mulliken).