bluuebunny/crossref_metadata_2025 huggingface dataset:
On a General Relation Involving the Glass Temperature and Coefficients of Expansion of Polymers
Authors: Simha Robert , Boyer R. F.
Published: January 2005

Treating the glass temperature TG of polymers as an iso-free volume state allows one to derive the result (αL—αG). TG=K1, a constant; or the approximate result αLTG=K2, another constant. The α's are the coefficients of cubical expansion for 100% amorphous polymer above and below TG. K1 is 0.113 for a wide variety of polymers differing in cohesive energy density, chain stiffness, and geometry. We thus have a general criterion for TG. K2 is 0.164. This latter relation combined with the principle of corresponding states, results in an expression for Tg as a function of cohesive energy density and chain rigidity. The polyalkyl methacrylates which have side-chain transitions below TG follow the first equation if αG is replaced by αG′, the expansion coefficient below the side-chain transition. Polymer-solvent systems are similar to the polyalkylmethacrylates. Two additional products, αL·TM and ΔCP·TG, where TM is the melting point of the polymer and ΔCP is the jump in specific heat at TG, are approximately constant.
Long-Range Coupling in the NMR Spectra of Aldehydic Protons in Aromatic Compounds
Authors: de Kowalewski Dora G. , Kowalewski Valdemar J.
Published: January 2005

The proton signal of the O=C–H group in ortho-substituted benzaldehydes shows a coupling with a ring proton. The analysis of the spectra of 2,4-dichlorobenzaldehyde, 2,4-dimethoxybenzaldehyde, and 2,4-dihydroxybenzaldehyde shows that the observed splitting is due to a coupling with a ring proton situated five bonds away.
Single-Center Single-Determinant Calculation of the Relative Energies of CH3+, CH3, CH4, and CH5+. The Proton Affinity of Methane
Authors: Hoyland J. R. , Lampe F. W.
Published: January 2005

Using one-center single-determinant approximations to the pertinent wave functions, the energies of CH3, CH3+, and CH5+ relative to CH4 have been calculated. If corrections for the different molecular geometries of the various species are made, reasonably good agreement with experiment for the carbon—hydrogen bond strength in methane, the ionization potential of CH3, and the appearance potential of CH3+ from CH4 is obtained. The modification of the calculation that gives the best agreement with experiment for these three known quantities leads to a value of 7.26 eV for the proton affinity of methane.
Infrared Spectra of the Azide Ion in Alkali-Halide Lattices
Authors: Bryant James I. , Turrell George C.
Published: January 2005

The infrared-active vibrational frequencies of the azide ion as an impurity in KI, KBr, KCl, and NaCl lattices have been measured as functions of temperature. Samples were prepared using the pressed-disk technique. In several cases comparisons are made of the spectra of pressed disks with those of single-crystal samples grown from aqueous solutions. Identical frequency shifts with temperature and lattice in the two types of samples offer strong evidence of lattice intermixing (solid solution) in pressed disks.

A simple electrostatic model of impurity-ion—lattice interaction is presented. It is shown that inductive, Coulombic, and short-range forces all provide significant contributions to the lattice perturbation. The experimental data on the azide ion are used to make approximate calculations of the quadratic and cubic force constants for the hypothetical ``free'' azide ion and to provide tests of the electrostatic model being considered.
Kinetics of the Reaction of HI with Propylene
Authors: Bose A. N. , Benson Sidney W.
Published: January 2005

The very slow gas phase reaction between HI and propylene has been observed to follow a second-order rate law near 230°C. The product is i-PrI with less than 0.1% of n-PrI produced initially. Above 270°C, the secondary production of C3H8 and I2 becomes important. The lower temperature data permit measurement of the equilibrium constant K2.1 for C3H6+HI⇌ lim 12i−C3H7I.The value at 238° is in excellent agreement with independent estimates of the thermodynamics for this reaction which give ΔH0=—20.6 kcal/mole, ΔS0=—34.1 cal/mole-°K, ΔCp0=—1.6 cal/mole-°K.

The rate data yield for the addition reaction (k2) logk2=−(23 400/4.575T)+7.89  (liters/mole−sec).The combination of k2 and K2.1 yield values for k1 in excellent agreement with the directly observed values by Jones and Ogg at 330°C. Independent observations on the 328°C pyrolysis of n-PrI show that appreciable isomerization to i-PrI takes place and that HI is an important intermediate.
Angular Distribution of Intensity and Polarization in the Triplet-Singlet Emission of Benzene
Authors: Hameka H. F.
Published: January 2005

The angular distribution of intensity and polarization in the triplet singlet emission of benzene is calculated for the following mechanisms: (I) a magnetic quadrupole transition caused by the interaction between the electron spins and the radiation field; (IIa) an electric dipole transition where the wave functions are first corrected for spin orbit coupling and then for vibronic interactions; (IIb) an electric dipole transition where the triplet functions are first corrected for vibronic interactions and then for spin orbit coupling.
Potential Energy Constants, Rotational Distortion Constants, and Thermodynamic Properties of Methylacetylenes
Authors: Daykin P. N. , Sundaram S. , Cleveland Forrest F.
Published: January 2005

A special iterative method of obtaining the potential energy constants from vibrational and rotational spectra has been developed. The method has been applied to determine the potential energy constants of some methylacetylenes. The fundamental vibrational frequencies of the deuteriated and tritiated isotopic forms of the acetylenes have been calculated by transferring the force constants. The nonvanishing moments of the inertia tensor derivatives have been obtained for a CY3C≡CX type of molecule. Using a perturbation treatment, the rotational distortion constants DJ, DJK, and DK for these symmetric rotor molecules have been evaluated. These values have been compared with the values from microwave experiments where such data are available. The thermodynamic properties (heat capacity, heat-content function, free-energy function, and entropy) have been computed from the vibrational wave numbers for all the molecules. These calculations are based on a rigid-rotor harmonic-oscillator approximation for the ideal gaseous state at 1 atm pressure and for the range 100° to 1000°K.
Displacement of Photoelectrons and Positive Holes in Sheet Crystals of Silver Bromide as Shown by Development Techniques
Authors: Saunders V. I. , Tyler R. W. , West W.
Published: January 2005

The mobility of electrons in unannealed, large, thin crystals of silver bromide made from the melt was measured from the displacement of latent-image centers formed by flash exposures synchronized with pulsed electric fields; an etching-development technique was used to locate the latent image as reduced silver. Similarly, the motion of positive holes in the crystals was determined by the hole-induced destruction of previously introduced latent-image centers or fog centers, which, on development, yielded a bleached image against a background of reduced silver. At 30°C, the electron mobility in these crystals was 66 cm2 V—1 sec—1, and their lifetime about 0.3 μsec; the mobility of the positive holes was 1.7 cm2 V—1 sec—1 and their lifetime in the undisturbed crystal was greater than 10 μsec.

Even in the absence of positive holes, the formation of latent image on a surface of silver bromide may be greatly facilitated by the presence of a sensitizer, such as silver sulfide. In such a case, silver sulfide appears to act as an electron trap or in some other way not associated with the capture of positive holes.
Physics of Semicrystalline Polymers
Authors: Tobolsky Arthur V.
Published: January 2005

The physics of semicrystalline polymers is discussed under the following headings: molecular dimensions of unoreinted chains; molecular dimensions of oriented chains; fiber dimensions; statistical-thermodynamic treatment; equation of state for a semicrystalline polymer chain; equation of state for semicrystalline polymers.
Anomalous Chemical Shifts in the Proton Magnetic Resonance Spectra of the Dimethylcyclohexanes and Related Hydrocarbons
Authors: Muller Norbert , Tosch William C.
Published: January 2005

High-resolution proton magnetic resonance spectra have been determined for the dimethylcyclohexanes and several related hydrocarbons between —130° and 130°C. All of the compounds which should undergo rapid ring inversion at room temperature produce spectra which change upon cooling because of ``freezing out'' of this motion. The assumption that appearance of the ring-hydrogen resonances as a relatively narrow band is invariably a symptom of rapid ring inversion is shown to be unfounded. Several of the ring spectra differ drastically from what is predicted using a bond-anisotropy model. A previously unrecognized effect must then make a significant contribution to the observed chemical shifts.
Multiple Reactions and the Vapor Transport of Solids
Authors: Mandel G.
Published: January 2005

The method of Lever, which has enabled calculation of the steady-state diffusion limited rate of transport of solid for the case of a single chemical equilibrium, is generalized to include the situation in which several equilibria are simultaneously operating. This is accomplished for the case of N equilibria by the introduction of (N — 1) ``coupling parameters,'' so defined that the steady-state conditions become formally identical to those given previously. Following Lever, the results of these operations are combined with the usual thermodynamic relations for the temperature dependence of the equilibrium constants, finally resulting in a set of (N — 1) linear simultaneous equations in (N — 1) unknowns, the ``coupling parameters.'' These equations can be solved, in general, in terms of the ratios of (N — 1) dimensional determinants.

On the basis of the above, a straightforward procedure is devised for the calculation of the rate of transport of solid, based on knowledge of initial conditions as well as thermodynamic and diffusion coefficient data.
Matrix Representation of Thermodynamic Properties of Multicomponent Systems
Authors: Wiederkehr Robert R. V.
Published: January 2005

Thermodynamic properties of multicomponent systems can be simply generated from matrices whose elements represent basic data. Although this concept is quite general, it has been applied specifically to generating the entropy, enthalpy, and free energy of multicomponent systems, as functions of composition and temperature. Each of these properties can be generated from the product of three matrices: a row vector whose elements depend only on the composition, a rectangular matrix whose elements remain invariant for a given system, and a column vector whose elements depend only on the temperature. A given row of the rectangular matrix corresponds to one of the species in the system and may be regarded as a thermodynamic-property vector for that species. Thermodynamic-property vectors have been calculated and tabulated for 143 species which are stable at high temperatures. The matrix representation of thermodynamic data has proved to be particularly useful in formulating large multicomponent problems for a digital computer. Two numerical examples illustrate the utility of the method.
Motion in Polyethylene. II. Vibrations in Crystalline Polyethylene
Authors: Wunderlich Bernhard
Published: January 2005

Using the specific heats of completely crystalline polyethylene as a basis, the vibrational spectrum is discussed. The vibrational spectrum is found to consist of three completely separate parts. (A) The high-frequency CH2-stretching vibrations between 2850 and 2930 cm—1 which contribute little to the specific heat below 350°K. (B) The low-frequency optical vibrations between 720 and 1480 cm—1 which contribute above 150°K increasingly to the specific heat. (C) The acoustical vibrations which stretch from zero to approximately 500 cm—1 and are at 260°K to 90% excited. A and B are adequately known from infrared and Raman experiments. C can be approximated by a Tarasov-type treatment leading to θ temperatures of 123° and 540° for the three-dimensional and one-dimensional parts, respectively.

More detailed spectra are discussed, and a semiempirical best fit is given. The one-dimensional Debye function necessary for this discussion has been computed to five places and is tabulated in steps of hν/kT=0.01.
Study of Vinyl Polymerization by Proton Magnetic Relaxation
Authors: Bonera G. , De Stefano P. , Rigamonti A.
Published: January 2005

A study of molecular motion during the process of polymer formation has been performed with measurements of proton magnetic relaxation. The presence of two distinct relaxation processes for the protons of the monomer molecules and those of the polymer chains has been observed. During the polymerization the spin-lattice relaxation time T1 of the monomer protons decreases very slowly while the flow viscosity of the sample increases greatly; this reveals that the motions responsible for the relaxation are mainly rotational. These motions can be considered to be thermally activated: the activation energies increase as the polymerization proceeds. The results we have obtained can be explained by assuming that there is a motion which has a predominant effect upon the relaxation and that a distribution of correlation frequencies, the width of which increases as the polymerization proceeds, is present. By making certain assumptions it has been possible to obtain some information about this distribution.
Determination of Gaseous-Diffusion Coefficients from Viscosity Measurements
Authors: Weissman Stanley , Mason E. A.
Published: January 2005

Diffusion coefficients for pairs of simple gases have been determined from the experimental viscosities of binary mixtures. The calculational procedure is essentially independent of any intermolecular-force model. The resulting diffusion coefficients are in good agreement with directly measured experimental diffusion coefficients, even in the temperature range where quantum effects are important.
Hindered Internal Rotation and ESR Spectroscopy
Authors: Stone Ellery W. , Maki August H.
Published: January 2005

A theory of the effect of hindered internal rotation on β-proton coupling constants in free radicals is proposed and discussed. The results of both classical and quantum-mechanical treatments are applied to recent ESR data on the anion radicals of several nitroalkanes. It is shown that a twofold barrier to internal rotation of magnitude 1.4 kcal/mole can account for the observed variation of proton coupling constants between the nitroethane and 2-nitropropane anion radicals. The temperature dependence of the coupling constants is predicted. In the equation aβH = (B0+B2 cos2θ)ρπ, it is shown that the term B0 may be attributed to residual torsional motion of β protons in the crystal lattice.
Infrared Intensities of Silane
Authors: Levin Ira W. , King W. T.
Published: January 2005

The integrated intensities of the fundamental absorption bands of SiH4, SiD4, and SiD3H have been measured using the Wilson—Wells—Penner—Weber method. These data indicate that the derivatives of the molecular dipole moment with respect to the bond-stretching and bond-bending coordinates are of opposite algebraic sign.
Adsorption of Hydrogen on a (110) Nickel Surface
Authors: Germer L. H. , MacRae A. U.
Published: January 2005

Hydrogen adsorption at room temperature on a clean (110) surface of a nickel single crystal is accompanied by reconstructive rearrangement of the surface metal atoms to form a (2×1) surface structure. It is possible to remove this adsorbed hydrogen and obtain a planar surface by heating the crystal slightly above room temperature. A determination of the temperatures and equilibrium hydrogen pressures necessary to remove this adsorbed hydrogen yields an isosteric heat of adsorption of 1.2 eV.

Oxygen displaces the hydrogen in the (2×1) structure from the surface and results in the formation of the (1×2) structure characteristic of adsorbed oxygen. This oxygen can be removed from the surface, however, by heating the crystal to 200°C in hydrogen.
Classical Model for Vibrational and Rotational Excitation of Diatomic Molecules by Collision. II. Interaction with Arbitrary Potential Functions
Authors: Benson Sidney W. , Berend George C. , Wu James C.
Published: January 2005

Two classical models for vibrational energy transfer between a diatomic harmonic oscillator A-B and an atom C are examined in detail. The first model corresponds to a harmonic repulsion between B and C with a smooth cutoff at zero interaction. It can be solved exactly. The second corresponds to a Morse-like potential between B and C. In this case, the orbits for colinear collisions are followed on a digital computer, and ΔEv the inelastic energy transfer is ``measured'' from this numerical solution for the equation of motion. The results can be transformed into probabilities by defining excitation as the condition: 2hν>ΔEv≥hν. ΔEv is a strong function of the phase angle of the oscillator. The probability function for excitation is transformed into a rate constant by averaging over the temperature-dependent distribution functions for energies.

In contrast to other ``classical'' solutions, it is found that P, the probability of excitation (or de-excitation), has a nearly Arrhenius type of dependence on temperature. The activation energy of P is quadratically sensitive to the range of the repulsive interaction between B and C. This arises from the result that the excitation probability P(ER) goes very sharply to zero as ER, the relative collisional energy, approaches some small limiting value. This is in marked contrast to present theories for which P(ER) goes asymptotically to zero with ER.

Features of the classical model are discussed in some detail and comparisons are made with experimental data from shock tubes. Because of the extreme sensitivity of the model to the value for the range parameters, no absolute predictions of de-excitation probabilities are possible. However, it is possible to fit the temperature dependence reasonably well with physically acceptable Morse parameters.
Thermodynamic Stability of Polymer Crystals. II. Torsional Vibrations of Chain Molecules
Authors: Peterlin Anton , Fischer E. W. , Reinhold Chr.
Published: January 2005

By taking into account the decrease of interchain potential barrier for longitudinal displacement as a consequence of incoherent longitudinal vibration of adjacent chains, the free-energy density exhibits a minimum at a finite number N* of monomer units in the straight section of the macromolecule between the (001) surfaces. Crystals with N* are thermodynamically stabler than those with N≠N*. The agreement with experimental data can be very much improved by considering torsional vibrations. Starting with the known interaction energy between two CH2 groups and considering the influence of the six adjacent polyethylene chains only the lattice force field was derived and the torsional fluctuation amplitude calculated. The resulting N* fits very well with measurements of Fischer and Schmidt on crystals grown at different temperature from dilute xylene and butyl acetate solution when the surface energy is assumed close to 40 erg/cm2. With this value the theory does not predict stable crystals with finite N* above 110°C; thus the growth tendency of polyethylene crystals during annealing has no limits at least until the macromolecules are completely stretched.
ESR Investigation of Some Thiazine and Oxazine Dye Radicals
Authors: Heineken F. W. , Bruin M. , Bruin F.
Published: January 2005

ESR spectra of semiquinone radicals, formed as intermediary reduction products in reversibly reducible thiazine and oxazine dyestuffs, have been investigated in acid as well as in alkaline solution.

In acid solutions at relatively high concentration of the dye the spectra consist of four lines. In alkaline solutions at high concentration there are three lines. At lower concentrations most spectra could be resolved further into many components.

A tentative interpretation of the spectra is given.
Electron Spin Resonance of Azulene Anion Radicals
Authors: Bernal Ivan , Rieger Philip H. , Fraenkel George K.
Published: January 2005

The electron spin resonance spectra of the anion radicals of azulene, azulene-1,3-d2, 4,6,8-trimethylazulene, and 4,6,8-trimethylazulene-1,3-d2 have been examined. These hydrocarbons are nonalternant and have aromatic ring structures with C–C–C bond angles that depart from 120°. The radicals were generated electrolytically in N,N-dimethylformamide using tetra-n-propylammonium perchlorate as supporting electrolyte. Sigma-pi-interaction calculations of the parameter QCHH [in the relation aiH=QCHHρiπ between the isotropic proton hyperfine splitting (aiH) and pi-electron spin density (ρiπ)] have been performed as a function of the bond angles at the carbon atom bonded to the proton. These calculations indicate a strong dependence of this parameter on angle. By using recent x-ray data on azulene, predictions could be made of the Q's at the different positions in the radicals. In contrast, the proton splitting at a methyl-group substituent, determined by the parameter QCCH3H, is predicted to be independent of the bond angles at the carbon atom of the aromatic system. Calculations of the pi-electron spin density were made in both the simple Hückel and the McLachlan extended self-consistent field molecular-orbital theory approximations. These calculations were used with the experimental splitting constants to make a comparison with the predicted bond-angle variation of the sigma-pi interaction parameters (Q's). The McLachlan procedure gives much more satisfactory results than the Hückel calculations, but the agreement with experiment, involving use of the predicted dependence of QCHH on bond angle, is only approximate. The theoretical estimates of the variation of QCHH with bond angle, and of the constancy of QCCH3H, appear to be qualitatively correct. Applications of the theory for the change of QCHH with angle may in some instances necessitate taking into account bent bonds.
Thermal and Magnetic Study of Crystal Field Splittings in Thulium Ethylsulfate
Authors: Gerstein B. C. , Jennings L. D. , Spedding F. H.
Published: January 2005

The heat capacity and principal susceptibilities of thulium ethylsulfate have been measured in the range 15°—300°K and 1.3°—200°K, respectively. The heat capacity of lutetium ethylsulfate has been measured in the range 15°—300°K. The contribution of the 4f electrons in Tm to the heat capacity of thulium ethylsulfate has been evaluated experimentally by making an assumption concerning the difference in the lattice heat capacities of Tm and Lu ethylsulfates. The contribution of the 4f electrons in Tm to the heat capacity and principal susceptibilities has been calculated using the angular part of the crystal field matrix elements calculated by Stevens and Elliott [K. W. H. Stevens, Proc. Phys. Soc. (London) A65, 209 (1952). R. J. Elliott, Revs. Modern Phys. 25, 167 (1953); R. J. Elliott and K. W. H. Stevens, Proc. Roy. Soc. (London) A219, 387 (1953); A218, 553 (1953)], and two sets of crystal field parameters currently available in the literature [E. Y. Wong and I. Richman, J. Chem. Phys. 34, 1182 (1961); J. B. Gruber and J. G. Conway, ibid. 32, 1531 (1960)]. The experimental results indicate that the crystal field parameters of Wong and Richman are more nearly correct than those of Gruber and Conway.
On Small-Angle Critical Scattering
Authors: Frisch H. L. , Brady G. W.
Published: January 2005

Recent theoretical studies of simplified models of cooperative assemblies of atoms or molecules suggest that the pair correlation function G(r) at the critical is not given by the Ornstein—Zernike (O.Z.) expression but that this relation becomes asymptotically valid for large distances r away from the critical. Based on some further heuristic considerations we suggest that the low-angle scattering of radiation or particles from real three-dimensional cooperative assemblies at the critical composition and temperatures, above but near the critical is essentially given by the Fourier transform of a G(r) which is an interpolation between the O.Z. expression and the critical G(r) suggested by the simplified models. We derive thus the form of the relative, reduced small angle scattering intensity and indicate in what ways departures from the O.Z. predictions are expected and comment on their magnitude. These calculations may possibly explain certain small but systematic anomalies observed in small angle x-ray scattering from critical binary fluid mixtures. In a particular instance we can thus show that the apparent linearity of an O.Z. plot (reciprocal intensity versus essentially the square of the scattering angle) is not sufficient evidence for the validity of the O.Z. theory at the critical point. We point out the possibility of two types of clustering (``ferromagnetic'' and ``anti-ferromagnetic'') in binary mixtures and indicate the usefulness of the Zimm cluster integral as a measure of the first type in clarifying the interpretation of scattering data. We speculate briefly on the possibility of ``critical cluster'' formation.
Simple Evaluation of the Paramagnetic Part of the Proton Magnetic Shielding Constant
Authors: Chan Sunney I. , Das T. P.
Published: January 2005

General arguments are proposed to show that the second-order paramagnetic susceptibility of a molecule is a minimum when the origin of the magnetic vector potential is chosen at the electronic centroid. It is shown that with this choice of gauge, it is possible to evaluate a major portion of the paramagnetic part of the proton magnetic-shielding constant from a knowledge of the dipole moment, bond distances, and bond angles of the molecule alone. This formulation is applied to the molecules H2, HF, HCl, HBr, HI, LiH, HCN, C2H2, CH4, and NH3. Good agreement is obtained when the results are compared with available data from molecular-beam experiments.
Symmetry Properties of the Asymmetric-Rotator Centrifugal-Distortion Constants
Authors: Parker Paul M.
Published: January 2005

The symmetry properties of the first-order centrifugal-distortion Hamiltonian for the asymmetric rotator have been studied. The number of independent distortion constants needed to interpret centrifugal-distortion effects in microwave and infrared spectra of asymmetric top molecules is determined for the asymmetric-rotator point groups and a number of relationships existing between these constants is given.
``Improved'' Free Volume Theory of Liquids. III. Approximate Theory of Molecular Correlations in Liquids
Authors: Chung Harold S. , Dahler John S.
Published: January 2005

An approximate theory of molecular correlations in liquids is presented in an effort to improve the free volume theory of Dahler and Hirschfelder. Two approximations are studied, one suggested by Taylor and the other corresponding to the ``cell-cluster'' expansion scheme of de Boer. The formalism is based entirely upon the self-consistent field theory of Paper II except that the cell distribution functions are replaced by Gaussian error functions in order to facilitate numerical computation and to make the problem more tractable. The results ``suggest'' quantitative improvements over those obtained in II and illustrate that the treatment of correlative effects is practical from a numerical standpoint. Extensive tables of compressibility factor, configurational energy, and configurational entropy are given. Graphical comparisons between our results and those of other theories and experiments are presented.
Diffusion of Krypton-85 in Dense Gases
Authors: Durbin Leo , Kobayashi Riki
Published: January 2005

With two high-pressure quasi-stationary diffusion cells, one depending upon ionization current measurement and the other scintillation detection of radioactive tracer activity, Fick's law diffusivities were determined for the diffusion of tracer amounts of krypton-85 in dense gases of krypton, argon, nitrogen, helium, carbon dioxide, and ethylene for isotherms about room temperature and densities to 15 mole/liter. In order to obtain absolute diffusivities, the cross-sectional area to length ratio of a primary standard porous plug consisting of a bundle of glass capillaries was precisely determined by weight-of-mercury and resistance-of-mercury calibrations. Stirring in the end chambers of the ionization cell was found to increase the determined diffusivity of krypton-85 in argon at 35°C by as much as 4.5% at a density of 12 mole/liter. The density—diffusivity product increases with density in the lower density region below about five moles per liter for all the isotherms. Extrapolations of the experimental data to low densities yield diffusivities which are in good agreement with low-pressure results by other investigators and Chapman—Enskog dilute-gas-theory predictions. Krypton self-diffusion coefficients calculated according to the real-gas modified Enskog theory with PVT properties, agree remarkably well with the experimental data over the density range investigated. The binary diffusivities of krypton-85 in dense base gases of argon, nitrogen, and ethylene are best predicted by the real-gas modified Enskog theory with PVT properties evaluated at a base-gas reduced temperature corresponding to the temperature of the system reduced by the mixed interaction potential temperature. In terms of precision of results and technological ease of operation the ionization cell proved to be superior to the scintillation cell.
Effect of Added Quenchers in Organic Scintillator Solutions: Organometallics
Authors: Kropp John L. , Burton Milton
Published: January 2005

Quenching constants (γs and γx) are given for a variety of perphenyl metals (Si, Ge, Sn, Pb, Sb, and Hg) and for mercury dimethyl acting on benzene and cyclohexane solvents and p-terphenyl and DPA scintillators. Specific rates are calculated for the quenching processes and are found to break into the following classes: <7×109 M—1 sec—1 corresponding to spin-perturbation-induced quenching (with a probability factor less than unity, according to Umberger—LaMer calculations) and ≧3×1010 M—1 sec—1 (exceeding such calculated values), corresponding to highly favored excitation-transfer processes. The latter high values can be explained in terms of the domain theory of liquid scintillator solutions. Specific rates in the intermediate range for GePh4, and perhaps for SiPh4, acting on solvents are consistent with resistance to high-energy irradiation and with the attendant probability that long-lived excited states of such quenchers actually transfer excitation to the scintillator.

Anomalously high quenching constants and specific rates for quenching (as well as an anomalous relationship between quenching constants for aerated and de-aerated solutions) in the case of cyclohexane suggest that a proper view of energy deposition should be an initial nonlocalized excitation of the system, followed by competitive localization of excitation in one of several particular species: i.e., cyclohexane (which may immediately decompose if an excited state is directly produced), quencher, or scintillator.
Polarizability Change in Liquids Due to Many-Body Interactions
Authors: Yaris Robert , Kirtman Bernard
Published: January 2005

Approximate quantum-mechanical expressions for the change in polarizability due to many-body interactions in spherically symmetric liquids, or dense gases, are derived by a variational form of perturbation theory. These expressions are evaluated using Linder's continuum model for the liquid and Slater-type wavefunctions. It is shown that the change in polarizability is approximately [3gα2/8(ea0)2], where α is the unperturbed polarizability and g is a parameter which depends on the dielectric constant and molar volume of the liquid. The predicted increase in polarizability varies from 0.042% for He to 3.54% for Xe.
Structure of Cu2B10H10
Authors: Dobrott Robert D. , Lipscomb William N.
Published: January 2005

An x-ray diffraction study of the crystal structure of Cu2B10H10 shows that the earlier proposal that the B10H10—2 ion has D4d symmetry is correct, and further establishes the covalent nature of the interactions of CuI with B atoms forming the edges of the polyhedron. There are eight Cu2B10H10 in a unit cell having dimensions a = 10.11, b = 11.36, and c = 14.50, and the space group is Pcab. Bonds within a tetragonal pyramid are 1.73 Å (to apex) and 1.86 Å (along base), while B–B bonds between the tetragonal pyramids are 1.81 Å in length. The closest Cu···B distances range from 2.14 to 2.33 Å in length.
Electron Spin Resonance in Polycrystalline Graphite
Authors: Singer L. S. , Wagoner G.
Published: January 2005

The electron spin resonance of polycrystalline graphite is shown to be due to charge carriers, as for single crystals. For lampblack-base graphite, the variation in g value with temperature agrees approximately with that for single crystal graphite if it is assumed that the spins effectively average out the anisotropic interactions by rapid intercrystallite diffusion. The magnitude and temperature dependence of the spin susceptibility are found to be in excellent agreement with McClure's theoretical predictions for the charge carriers in perfect graphite. Complications of measuring these materials are discussed, including effects of skin depth and microwave heating and the dependence upon crystallite size and sample purity. It is found that two types of impurities can affect the resonance; those which become ionized and shift the Fermi level, and large un-ionized atoms which do not shift the Fermi level but act as efficient scattering centers for shortening the spin—lattice relaxation time.
Interruption of Nuclear Spin Diffusion
Authors: Jennings D. A. , Tanttilla W. H.
Published: January 2005

Experimental results are shown in which the nuclear spin diffusion responsible for nuclear relaxation at low temperature, under certain circumstances, can be interrupted by introducing strains into crystals either by the paramagnetic impurity introduced into the crystal or by surface strains made to be significant by grinding the sample to a powder. Nuclei with large quadrupole moments, such as iodine, have their spin diffusion strongly interrupted whereas nuclei with no quadrupole moment, such as fluorine, show no effect of strains on the spin diffusion. The interpretations are made from measured values of the spin—lattice relaxation time at liquid-helium temperature.
Correlation Splitting in the Hydrogen Molecule
Authors: Davidson Ernest R. , Jones Leon L.
Published: January 2005

The difference between the energy of the best open-shell and best closed-shell wavefunctions for the hydrogen molecule was calculated for various values of the internuclear distance. Both left—right and in—out correlated functions were considered. The relative importance of the type of correlation reverses at an internuclear distance of 0.8 a0.
Absorption, Ionization, and Ion-Fragmentation Cross Sections of Hydrocarbon Vapors under Vacuum-Ultraviolet Radiation
Authors: Schoen Richard I.
Published: January 2005

Absorption and ionization cross sections of the hydrocarbon vapors ethane, propane, n-butane, n-pentane, cyclopropane, ethylene, propylene, cis-butene-2, and 1,3-butadiene were measured in the spectral range 9 to 25 eV. With the exceptions of ethylene and cyclopropane, the absorption cross sections rose smoothly to peaks near 16 eV and decreased smoothly toward higher energy. The maximum absorption cross section of an alkane could be estimated by multiplying the number of bonding electrons by 6 Mb. Similarly, a smooth rise and fall of the ionization cross sections was observed with the exceptions noted. The maximum ionization cross section could be estimated by multiplying the number of bonding electrons (π electrons excluded) by 5 Mb. The peaks of the ionization cross-section curves of the alkanes were near 16 eV and those of the olefins near 17.5 eV. Beyond the peaks the ionization efficiency was almost 100%. By combining the Seya-type monochromator with a mass spectrometer, cross sections for the production of various ion fragments of ethane, propane, cyclopropane, ethylene, and acetylene were obtained. Almost all ion-fragment cross-section curves rose for more than 2 eV above the threshold. No evidence was found for a sharp cutoff of the parent mass caused by fragmentation.
Microwave Studies of Butadiene Derivatives. I. Spectrum of Fluoroprene
Authors: Lide David R.
Published: January 2005

The microwave spectrum of fluoroprene (CH2=CHCF=CH2) has been studied in the 8–35 kMc region. The molecule is shown to have a planar trans configuration with ground-state rotational constants a=10006.26, b=4264.35, c=2989.21 Mc. The spectra of five excited vibrational states, including the first three excited torsional states, have been analyzed in detail. Relative-intensity measurements give a torsional frequency of 156±9 cm—1 with no detectable anharmonicity. Negative inertial defects are observed in the excited torsional states; this is explained by a simple model of the torsional oscillation. The dipole moment in the ground state has a magnitude of 1.417±0.010 D and makes an angle of 10°—15° with the C–F bond. Possible forms of the torsional potential function which are consistent with the experimental results are discussed. It is suggested that a function which allows for a nonplanar isomer in butadiene-type molecules (so far unobserved) gives a reasonable explanation of all the present data.
Studies on the Alternant Molecular Orbital Method. III. A Many-Parameter Energy Expression for Systems with Closed-Shell Structure
Authors: de Heer J.
Published: January 2005

A refined alternant molecular orbital (AMO) method is described in which we allow for different variable parameters for each MO pair which is coupled. A corresponding many-parameter energy expression for the ground state of an arbitrary system with closed-shell structure is derived. Results of a numerical analysis involving the pi-electron sextet in benzene are briefly reviewed. Possible future applications of this scheme are suggested.
Infrared Study of the Adsorption of Methanol and Ethanol on Aluminum Oxide
Authors: Greenler Robert G.
Published: January 2005

The adsorbed surface species which result when aluminum oxide is exposed to methanol or ethanol vapor have been studied. Three different surface species have been identified for both methanol and ethanol. At 35°C a weakly bound layer of liquid alcohol is observed, which is removed by evacuation. Another species which persists after prolonged evacuation is identified as a surface methoxide in the case of methanol and an ethoxide in the case of ethanol. When the alumina sample is heated to 170°C in alcohol vapor a formate-like surface compound is formed from methanol and an acetate-like compound from ethanol. This interpretation of the surface structure has been checked by using deuterated methanols and C13-enriched methanol.
Nuclear Spin Relaxation in Liquid CHFCl2
Authors: Brown R. J. C. , Gutowsky H. S. , Shimomura K.
Published: January 2005

Nuclear spin relaxation times have been measured for liquid CHFCl2, the values of T1H and T1F between 132° and 298°K at 27, 20 and 17 Mc, and T2H and T2F over the same temperature range at 20 Mc. The results of these measurements are discussed, and the following relaxation mechanisms are shown to be important: (a) intermolecular dipole—dipole interactions, including their effect upon the electronic, scalar coupling of the proton and fluorine nucleus, (b) the quadrupolar relaxation of the chlorine nuclei which are coupled to the proton and the fluorine nucleus by scalar couplings, and (c) the spin-rotation interaction between the fluorine nucleus and the reorientation of the molecule. It is noted that relaxation of the same type as mechanism (b) accounts for the relatively large natural linewidths and poorer resolution often found in spectra of heavier nuclei such as F and P, compared to spectra of protons in the same liquid compound.

The statistical assumptions of rotational Brownian motion of the molecule, in the liquid, when applied to the spin-rotation interaction, are found to predict the wrong temperature dependence of T1F at high temperatures. A transient rotation model is proposed in which the molecules ``jump'' from one orientation to another at random times; the spin-rotation interaction is assumed to operate during these ``jumps'' when the molecule is actually rotating. The statistical properties of such a model are calculated, and it is shown that T1F is predicted to have the correct temperature dependence. The model is compared with that developed by Johnson and Waugh for nuclear relaxation by the spin-rotation interaction in gases. The dipole—dipole and quadrupole interactions are discussed in detail, and a treatment of intermolecular dipole—dipole relaxation by Redfield's method is given, with results indicating that the electronic, scalar coupling of nuclei contributes to the inequality T2<T1 often found in liquids.
Structure of Formaldoxime
Authors: Levine Ira N.
Published: January 2005

The microwave spectra of cis-CHDNOH, trans-CHDNOH, C13H2NOH, CH2N15OH, and CH2NO18H were assigned. Together with the results of previous work on the normal species and CH2NOD, the data give the following planar structure for formaldoxime: bond lengths in Å; CHcis=1.085, CHtrans=1.086, C=N=1.276, NO=1.408, OH=0.956; bond angles; HcisCN 121°46′, HtransCN 115°33′, CNO 110°12′, NOH 102°41′.

The most significant feature of the structure is the difference between cis- and trans-HCN bond angles. This ``tilt'' of the methylene group appears to be too large to be attributed to steric repulsion. The C=N and N–O bond lengths are consistent with the Schomaker—Stevenson relation if allowance for resonance is made.
Correlation Diagram for H2. Oscillator Strengths
Authors: Peek James M. , Lassettre Edwin N.
Published: January 2005

The eigenvalues of a one-electron Hamiltonian, based on a model of the hydrogen molecule proposed earlier by the authors [J. Chem. Phys. 33, 1803 (1960)], have been calculated for several states as a function of internuclear distance. These results are shown as a correlation diagram which is complete for all states correlating with separated atoms having principal quantum numbers up to three. This correlation diagram provides a semiquantitative justification for the model. A number of physical implications of the diagram are discussed. Several members of the set of one-electron eigenfunctions of the model Hamiltonian have been used to calculate oscillator strengths for single electron excitations. The values 0.28, 0.556 were found for the oscillator strengths corresponding to the Lyman and sum of the Lyman and Werner bands, where the best available estimates for H2 are 0.27, 0.65, respectively. A number of other oscillator strengths, for which there is no available information for comparison, have also been calculated.
Ion—Solvent Interaction in Mixed Solvents. II. The Viscosity of Electrolytes in Mixed Solvents
Authors: Padova J.
Published: January 2005

The viscosities of Na2SO4, MgSO4, MnCl2, NaOCOCH3, Ba(OCOCH3)2, Mg(OCOCH3)2, and KOCOCH3 have been determined at 25°C in ethanol—water and acetone—water mixtures. Results have been interpreted as a function of solvated molar volume using an extension of Mooney's equation. Interaction coefficients have been calculated and correlated with the B coefficients of the Jones—Dole equation.
Orientation Birefringence of Macromolecular Solutions in Shear Flow and Electric Field
Authors: Ikeda Shoichi
Published: January 2005

The orientation distribution function of polar rigid macromolecules in dielectric media is obtained by solving the rotary diffusion equation in the steady state, when the solution flows with a constant velocity gradient and is acted upon by an electrostatic field perpendicular to the stream line. The optical properties, such as birefringence of the solution, are calculated by averaging the optical anisotropy of each macromolecule over all molecular orientations, which are weighted according to the orientation distribution function. The extinction angle and the amount of birefringence are expressed as functions of the velocity gradient and the electric field strength. The behavior of these properties is specifically dependent on the shape and the electric parameters of macromolecule. This method can provide new information about the macromolecular structure.
Mass-Spectrometer Investigation of Electron-Impact Processes at Pressures to 1 mm Hg
Authors: Curran R. K.
Published: January 2005

A mass spectrometer for the study of secondary reactions involving ions, excited species, and molecules is described. The instrument was checked with the Hornbeck—Molnar process for He2+ formation in He, O3+, and O4+ formation in O2 and N3+, and N4+ formation in N2. Source pressures to about 1 mm Hg are used. The electron beam is controlled by the retarding potential-difference technique for reducing the effective width in energy of the electron distribution.
Reaction Kinetics of a Long-Chain Molecule. II. Arends' Solution
Authors: Keller Joseph B.
Published: January 2005

In Part I [J. Chem. Phys. 37, 2584 (1962)] we considered the reaction kinetics of a long-chain molecule, each segment of which carries a reactive group. The reactivity of each group depended upon whether zero, one, or two of its nearest neighbors had reacted. The average fractions of reacted groups and of unreacted with zero, one of two reacted neighbors were found as functions of time. Now we derive C. B. Arends' [J. Chem. Phys. 38, 322 (1963)] solution for the average fraction of sequences of unreacted groups of n for n=1, 2, ···. We start with the infinite set of differential equations for these average fractions derived by W. G. Lloyd and T. Alfrey, Jr. [J. Chem. Phys. 38, 318 (1963)]. We solve them by assuming a solution of the form derived by Arends. Thus we verify that Arends' solution satisfies the equations of Lloyd and Alfrey and we derive it more simply. In addition we show that the present results yield exactly those of Part I, thus verifying the hypothesis introduced in that work.
Electronic Spectra and Hydrogen Bonding. II. Anthrols
Authors: Suzuki Satoshi , Baba Hiroaki
Published: January 2005

An investigation has been made of the effect of hydrogen bonding on the absorption and fluorescence spectra of α- and β-anthrols. It is shown that, when a hydrogen bond is formed between the anthrols and dioxane, each electronic band exhibits a characteristic behavior which supplies a substantial clue as to the origin of the band. The behavior in hydrogen bonding of the low-frequency absorption of β-anthrol clearly indicates that the absorption consists of two overlapping electronic transitions: One at lower frequencies, which was previously assigned to the 1Lb transition, shows a large red shift (340 cm—1) upon formation of the hydrogen bond, whereas the other transition, 1La, shows only a small red shift (60 cm—1). The results of experiments on both the absorption and fluorescence spectra show that the proton-donating power of the anthrols is evidently greater in the first excited state than in the ground state.