bluuebunny/crossref_metadata_2025 huggingface dataset:
Volumetric and Thermodynamic Properties of Fluids. VI. Relationship of Molecular Properties to the Acentric Factor
Authors: Danon F. , Pitzer Kenneth S.
Published: January 2005

A method is developed for the derivation of improved intermolecular potentials from empirical second virial coefficient data together with the acentric factors of the fluids. The Kihara core model is considered first, and relationships are derived between the acentric factor and the core size for several shapes. The resulting cores for CH4, CF4, C(CH3)4, C6H6, and N2 are reasonable in view of semiquantitative theoretical expectations, but the core for CO2 is somewhat larger than expected. An approximate treatment is given which combines the Kihara core model with an electric quadrupole interaction. The core calculated for CO2 on this model including the quadrupole moment is of a reasonable size.
Microwave Spectrum and Quadrupole Interaction in cis-1,2-Dichloroethylene
Authors: Flygare W. H. , Howe J. A.
Published: January 2005

The microwave spectrum of cis-1,2-dichloroethylene has been assigned. The rotational constants of cis-CHCl35 CHCl35 are A = 11 518.33 Mc, B = 2545.15 Mc, and C = 2082.57 Mc. The Cl35 nuclear quadrupole coupling constants have been measured and are χaa = 3.7 Mc, χbb = —35.6 Mc, and χcc = 31.9 Mc. Various aspects of the nuclear quadrupole interaction and the structure of the molecule are discussed.
Calculations of the Coefficient of Thermal Conductivity for Dissociating Hydrogen
Authors: Clifton David G.
Published: January 2005

The kinetic theory of dilute monatomic gases and gas mixtures as applied to reacting polyatomic gases has been used to calculate the coefficient of thermal conductivity of dissociating hydrogen for temperatures from 1500° to 5000°K and pressures of 0.1, 0.5, 1, 2, 10, 50, and 100 atm. The particle interaction potentials used are the same as those in a previous paper. Certain equilibrium properties of the H2⇋2H system which are necessary to the computations are given.
Nuclear Magnetic Resonance in Metal Tungsten Bronzes
Authors: Jones W. H. , Garbaty E. A. , Barnes R. G.
Published: January 2005

The nuclear magnetic resonances of Li7, Na23, and Tl203,205 have been studied in metal tungsten bronzes (MxWO3) in those composition ranges (x values) which possess metallic properties as evidenced by their electrical conductivity. In all cases, the shifts of these resonances with respect to diamagnetic reference compounds were found to be extremely small, indicating that the nuclei of the metal atoms do not interact with the conduction electrons as in the case of ordinary metals. This appears to result from the occurrence of either a radial or an angular node in the conduction band wave functions at the metal atom positions. In the case of the thallium tungsten bronze, linewidth results indicate the presence of indirect nuclear spin exchange interactions.
Time Lag in Transport Theory
Authors: Frisch H. L.
Published: January 2005

The time lag in the attainment of a stationary state or flow is defined for a class of linear and nonlinear transport equations. It is shown that the explicit calculation of the time lag can be reduced, for these equations, to the determination of the Green's function of a simpler, linear, time-independent boundary-value problem. For a linear transport equation knowledge of this Green's function enables one to recursively calculate certain time moments which afford an approximate representation of the solution. The possibility of an asymptotic exponential approach to the steady-state solution of these linear transport equations is directly related to the convergence of the sequence of these time moments. An explicit example of a nonlinear diffusion in a finite system is used to illustrate the general theory. Certain properties of the time lag for the flux of this nonlinear diffusion problem are derived in the Appendix.
Calorimetry in Liquid Thallium Nitrate-Alkali Nitrate Mixtures
Authors: Kleppa O. J. , Hersh L. S.
Published: January 2005

The enthalpies of mixing in the binary liquid mixtures of thallium nitrate with lithium-, sodium-, potassium-, and rubidium nitrate have been measured at 350°C. It is found that the molar enthalpy of mixing (ΔHM) varies in a somewhat irregular manner as the size of the alkali ion is varied. In this respect these systems give the appearance of differing in behavior both from the binary alkali nitrates on the one hand, and from the silver nitrate-alkali nitrates on the other. However, it will be shown that the results can be accounted for by an approximate semiempirical expression of the type previously used for the silver nitrate-alkali nitrate systems: ΔHM≅−X(1−X)[U′δ2+U′′δ]In this expression X and (1—X) are the mole fractions of the two components; δ=(dTlNO3—dAlkNO3)/(dTlNO3+dAlkNO3), where d is the sum of the ionic radii in the considered salts, while U′ and U″ are constants. The numerical value of U′ is 140 kcal/mole, the same value as for the previously explored nitrates. The value of U″ is 16 kcal/mole, i.e., of the same order of magnitude as the non-Coulombic contribution to the lattice energy of thallium nitrate.
Relation between ESR Spectra and Molecular Orientation in Irradiated Polyethylene
Authors: Kashiwagi Michio
Published: January 2005

Measurements have been made of the electron spin resonance spectra of irradiated polyethylene filaments with various draw ratios. The feature of the spectra is that the doublet splitting in each component of a quintet structure depends on the degree of molecular orientation in filaments. This can be ascribed to σ-proton anisotropy in alkyl radicals mainly trapped in irradiated polyethylene.

From the information about CH radicals of irradiated organic crystals and the molecular orientation of polymers, the relation between the doublet splitting D and the degree of molecular orientation f is obtained as follows: D=13.9(1−0.35f)12+5.1(1−0.65f)12 (gauss)for the high-density polyethylene, consisting predominantly of the crystalline regions, and the spin density of the central carbon atom of the radical is 0.70.
Potential Constants of PCl3 from Amplitudes of Vibration and Normal Vibration Frequencies
Authors: Iwasaki Machio , Hedberg Kenneth
Published: January 2005

Using the mean square amplitudes of vibration obtained from gaseous electron diffraction experiments at 300° and 505°K together with the normal vibration frequencies, a reasonable set of values has been derived for the potential constants of the general quadratic function 2V=Σfτ(Δri)2+2Σfrr(Δri)(Δrj)+Σfθ(r0Δθij)2 +2Σfθθ(r0Δθij)(r0Δθjk)+2Σfrθ(Δri)(r0Δθij)+2Σfrθ′(Δri)(r0Δθjk). The values in millidynes/A are, with estimated standard errors, fr=2.829±0.374,frr=0.589±0.298,fθ=0.278±0.038,fθθ=0.455±0.039,frθ=0.273±0.212,frθ′=0.071±0.280.
Departure from the Steady State in Chain Reactions with Two or More Radicals
Authors: Giddings J. Calvin , Shin Hyung Kyu
Published: January 2005

A method used previously for obtaining the departure from steady-state kinetics with one reactive intermediate is extended to chain reactions with two or more intermediates or radicals. This method is applied to the H2–Br2 reaction and to the pyrolyses of methane, ethane, and acetaldehyde. It is found that serious departures from steady-state conditions occur in the experimental range of ethane decomposition and H2—Br2 reaction. The departure is serious for all such processes in the very fast reaction, high-temperature region.

Using a hypothetical reaction scheme with characteristics similar to those of most chain reactions, approximate equations are obtained for the initial transients connected with the build up of radicals. The relationship between steady-state departure, both during and after the transient period, and the cumulative extent of reaction are explored for this reaction.
Photoionization of Nitric Oxide
Authors: Doering John P. , Mahan Bruce H.
Published: January 2005

The photostationary concentration of ions in gaseous nitric oxide has been measured using a Langmuir probe. The ion concentration depends on the square root of the ion production rate, which indicates that ions and electrons disappear predominately by dissociative recombination. In addition, the rate of decay of the electron concentration in the gas after interruption of the ionizing radiation has been measured. The data indicate that the ion-electron dissociative recombination rate constant is no greater than 2×10—6 cm3/ion sec, and may be as low as 4×10—7 cm3/ion sec.
Electron Distribution in the C–Cl Bonds of CH2Cl2 and Derivation of Matrix Elements Off-Diagonal in J for Two Quadrupolar Nuclei in an Asymmetric Rotor
Authors: Flygare W. H. , Gwinn William D.
Published: January 2005

The microwave spectrum of methylene chloride has been reinvestigated with the high-resolution spectrometer now available. The diagonal quadrupole coupling constants of Cl in CH2Cl235 were remeasured under high resolution, giving χaa=—41.07±0.01 Mc, χbb=1.24±0.02 Mc, and χcc=+39.83±0.01 Mc. By using second-order perturbation theory, the off-diagonal element χab was measured directly and was —52±3 Mc. These results show that the C–Cl bond in methylene chloride is not bent within an experimental error of 1°.

Matrix elements off-diagonal in J, of the quadrupole interaction Hamiltonian for two quadrupolar nuclei, are derived using Racah coefficients. The I1=I2=32 matrix elements are evaluated and listed in the Appendix.
Electron-Optical Phonon Interaction for Paramagnetic Ions in Crystalline Fields
Authors: Pollack S. A. , Satten R. A.
Published: January 2005

The theory of vibronic transitions in rare-earth and actinide series crystalline salts is applied to ions and ion complexes interacting with the vibrational modes of the entire crystal. Selection rules and expected fine structure are presented making use of space group representation theory. The results are applied to the visible spectra of three U4+ ion crystalline salts which are analyzed in higher dispersion than in previous work, and including [N(C2H5)4]2UCl6 for the first time. The similarity of the absorption bands associated with each electronic level provides additional evidence for the vibronic nature of the spectrum. Electronic level positions given earlier are confirmed. The broad features of the spectrum such as the strongest vibronic bands can be described in terms of the vibronic states of a single ion complex. These bands, however, have structure at 77°K in thin crystals and a finer structure more evident at 4.2°K, which we explain for some levels as due to the splitting of the vibrational optical branches when the wave vector k is nonzero, and for other levels the latter in combination with a splitting of vibronic bands resulting from electron-vibration interaction. The electron-vibration interaction applied to a single ion complex does not lead to structure in a vibronic spectral line. It is experimentally demonstrated that pure electronic electric dipole transitions forbidden to appear when the U4+ ion is at a center of inversion symmetry can appear due to the presence of impurities which destroy the inversion symmetry. The splitting of some of the pure electronic levels expected as one goes from Oh to D3d to D2h symmetry seems not to occur except possibly in one or two cases. More precise temperature shift measurements are presented including the [N(C2H5)4]2UCl6 salt for the first time. The possible existence of some metastable optical branches at 4.2°K is indicated.
Simple Molecular Orbital Theory of the Dichloroethylenes
Authors: Howe J. A. , Muirhead J. S. , Goldstein J. H.
Published: January 2005

A simple molecular orbital treatment, including overlap, has been employed to compute the electron distribution and energy eigenvalues of the dichloroethylenes. The Coulomb and exchange integrals used were those previously employed for vinyl chloride and were not subject to further adjustment in the present calculations. Comparison with available photoionization potentials, electric dipole moments, and nuclear quadrupole data shows, on the whole, a satisfactory agreement between observed and calculated properties. The results obtained are considered to provide support for the occurrence of lone-pair conjugation in the vinyl halides.
Experimental f Values and Electron Diffraction Amplitudes for Bromine
Authors: Hanson Harold P.
Published: January 2005

The atomic scattering observed in electron diffraction for the Br2 molecule is not predicted well by theory. The difficulty lies in the sensitivity of the scattering to the f values at small s. Taking advantage of this, one can obtain experimental values for the electron scattering amplitudes and the atomic structure factor. These values seem to be preferable to those obtained from calculations using statistical models. The method described is applicable to any element found in a simple, easily vaporized molecule.
Shrinkage Effect by Thermal Vibrations in Linear-Skeleton Molecules
Authors: Morino Yonezo , Nakamura Junko , Moore Peter W.
Published: January 2005

Apparent shrinkages of the interatomic distances along the carbon-carbon chains in allene and dimethyl-diacetylene are calculated from spectroscopic data. The L—1 matrices obtained from a normal coordinate analysis are used to calculate the perpendicular mean-square amplitudes of vibration from which the shrinkages are obtained. The computed values of the shrinkages are in fairly good agreement with those obtained from electron diffraction investigations.
Rate Constants for the Unimolecular Decomposition of Excited Molecular Species Near Threshold
Authors: Wolfsberg Max
Published: January 2005

The theoretical formulation of the unimolecular decomposition of excited (active) molecules developed by Marcus is applied to the numerical calculation of rate constants for such processes in the threshold region. The Marcus formulation for calculating numbers of vibrational energy states and densities of such states is briefly investigated. Threshold-region rate constants are investigated as a function of threshold energy and of molecular size. Decompositions of excited molecule ions in the ion source of a mass spectrometer are discussed in terms of these rate constants. It is found that this more exact theory of unimolecular dissociations removes some of the difficulties found in an earlier approach to the theory of mass spectra. Some interesting predictions of the present formulation are pointed out.
Selective Excitation of Trivalent Thulium via Intramolecular Energy Transfer
Authors: Crosby G. A. , Whan R. E.
Published: January 2005

The results of luminescence studies of thulium trisbenzoylacetonate and thulium trisdibenzoylmethide are reported. Selective excitation of the 1G4 level of Tm3+ via energy transfer has been achieved. Emission from the 3F4 level of the ion has been observed, and all the groups of lines appearing in the visible and near infrared spectral regions have been assigned. A quenching mechanism involving vibrational coupling of the ion with the ligand is discussed. Ligand field splitting is reported.
Nucleation of Zinc on Glass
Authors: Hudson John B.
Published: January 2005

The nucleation kinetics of zinc crystals from the vapor onto Pyrex glass have been measured over a range of more than 106 in zinc vapor pressure. Results can be brought into accord with classical nucleation theory only by the assumption of a thermal accommodation coefficient of less than unity for the self-adsorbed zinc layer on the glass substrate.
Pyrolysis of Di-tertiary Butyl Peroxide: Temperature Gradients and Chain Contribution to the Rate
Authors: Batt Leslie , Benson Sidney W.
Published: January 2005

An investigation of the pyrolysis of di-tertiary butyl peroxide over the range 27–130 mm Hg pressure and 130–160°C has shown that the experimental stoichiometry is 3.0 rather than the previously reported 2.9. Trace amounts of t-BuOH (0.5 to 1.0%), isobutylene oxide (1–2%) and t-BuOMe (0.02%) have been identified as well as biacetonyl and small amounts of other ketones. By using spherical vessels and octopus vessels of large surface/volume ratio, it is shown that the previously reported scatter in the Arrhenius parameters can be attributed to temperature gradients established in the vessel. This is confirmed by direct measurement of the gas temperature with fine thermocouple wires in thin glass wells.

The best rate constant for the first-order decomposition in the absence of temperature gradients is given by: logk=15.6–37 400/4.575T sec—1 with an uncertainty in E of about ±0.5 kcal. Assuming zero activation energy for the recombination of t-butoxy radicals, this gives the peroxide bond dissociation energy of 37.4±0.5 kcal/mole. An estimate of the standard entropy change for dtBP→2 t-BuO gives the remarkably low value of 108.2 l/mole-sec for the Arrhenius factor for the recombination of t-BuO radicals. It is shown that such a low value is needed to explain the concordance in Arrhenius parameters for liquid and gas state pyrolyses.

The isobutylene oxide puts a limit to the chain contribution of about 1 to 2%. The t-BuOH and t-BuOMe yields permit independent estimates of the rate of dissociation of t-BuO radicals in fair agreement with each other and other investigations.

The explosion limits for the decomposition are estimated to be about 7.5 atm (150°C). The present work confirms the importance of temperature gradients in contributing to spurious activation energies for very exothermic reactions.
On the Speed of Reactions at High Pressures
Authors: Teller Edward
Published: January 2005

Application of high pressures can give rise to explosive decomposition of various materials. Possible reasons for this phenomenon are discussed.
Absorption Coefficients of Sulfur Dioxide in the Vacuum Ultraviolet
Authors: Golomb D. , Watanabe K. , Marmo F. F.
Published: January 2005

Absorption coefficients of sulfur dioxide in the spectral region 1050–2170 A were measured photoelectrically at about 500 points of the spectrum. The absorption spectrum below 1350 A is interpreted in terms of a Rydberg series converging upon the ionization potential of 12.34 ev obtained by the photoionization method.
Deuteron Quadrupole Coupling in Diatomic ``Hydrides''
Authors: Kolker H. J. , Karplus M.
Published: January 2005

For LiD and DF, the deuteron quadrupole coupling constant (eqQ/h) has been calculated with single-determinant SCF-LCAO-MO functions. The results obtained are 38 kc/sec for LiD and 373 kc/sec for DF, in rather satisfactory agreement with the recently measured values (30±3 kc/sec for LiD and 340±40 kc/sec for DF). To evaluate the molecular integrals required for the determination of q, a formulation in terms of confocal elliptic coordinates was used. This made possible the introduction of certain auxiliary functions that are very convenient for the calculation of field gradient and related integrals. A comparison of the quadrupole coupling constants obtained with a number of different molecular orbital functions is presented. The results demonstrate the importance of using atomic basis functions with exponents optimized for the molecular system and suggest that exact Hartree-Fock functions may yield relatively reliable values for field gradients and other one-electron weak-interaction parameters.

A calculation of the field gradient at the Li nucleus (q = —0.0401 a.u.) yields a value of —3.7×10—26 cm2 for the Li7 quadrupole moment when combined with the coupling constant measurement of +346±1 kc/sec.
Molecular Interaction in Saturated Hydrocarbons
Authors: Rastogi R. P. , Girdhar H. L.
Published: January 2005

A semiempirical relationship between the critical constants and the chain length of saturated hydrocarbons has been established.
Spin Density Fluctuations in the Cyclooctatetraene Negative Ion
Authors: McLachlan Andrew D. , Snyder Lawrence C.
Published: January 2005

Vibronic coupling between the doubly degenerate orbital of the odd electron and the in-plane antisymmetric stretching vibration of the C–C bonds in C8H8— radical leads to two ground states of equal energy if the radical is planar. They correspond to vibrations about either of two equivalent distorted structures with alternating double and single bonds. The potential barrier between these structures has been estimated to be 824 cm—1. We find that the barrier considerably damps the fluctuations of electron charge and spin density which would occur in the undistorted planar radical. This situation is to be contrasted with benzene negative ion, in which vibronic coupling involved a degenerate vibration, and for which large undamped fluctuations have been anticipated on the basis of a similar theoretical description. This conclusion agrees with the recent observation of considerably narrower lines in the electron spin resonance spectra of C8H8— than were reported by Townsend and Weissman for spectra of the benzene and coronene negative ions.
Some Studies on Argon, Helium, and Carbon Dioxide with an Integrated-Schlieren Instrumented Shock Tube
Authors: Daen Jerome , de Boer P. C. T.
Published: January 2005

Using integrated-schlieren instrumentation, an investigation has been made of shock waves in argon, helium, and carbon dioxide. In argon and helium a residual signal has been observed, which is ascribed to curvature of the shock front in the vicinity of the wall. A discussion is presented of the way in which the curved shock satisfies the boundary conditions, and of the resulting flow pattern, which includes a ``pressure adjustment region.'' Preliminary measurements on the variation of the apparent ``zone thickness'' with density and shock speed in these gases are reported. The importance of the observed shock curvature in measurements of the vibrational relaxation time for gases like carbon dioxide is considered. Preliminary results for the vibrational relaxation times of dry CO2 are reported for temperatures up to about 900°K, and are compared with results obtained by others.
Electrical Resistance of Alpha Hydrogen-Palladium
Authors: Lindsay W. T. , Pement F. W.
Published: January 2005

Electrical resistance measurements of gas-charged alpha hydrogen-palladium alloys have been made in the range 100° to 400°C. The fractional increase of palladium resistance caused by addition of hydrogen is proportional to hydrogen concentration. The constant of proportionality is independent of temperature, indicating that Matthiessen's rule is inapplicable to this system. When the results of this work are combined with those of previous authors, all of the data can be adequately represented in the range 75° to 400°C by the equation (R/R0) — 1 = (2.41±0.04) m, where R is the resistance of alpha hydrogen-palladium, R0 is the resistance of hydrogen-free palladium, and m is the hydrogen-to-palladium atom ratio.
NMR Measurements of Self-Diffusion in Normal Hydrogen Gas from 55° to 90°K
Authors: Lipsicas Max
Published: January 2005

An absolute measurement of the self-diffusion coefficient D11 in hydrogen gas has been made at 78°K and 117 Amagats. Relative measurements have been made of D11 as a function of gas density at 55°, 78°, and 90°K, up to a maximum density of 650 Amagats. The experimental results are compared with viscosity data and with the theories of Buckingham and Mason. The observed density dependence of D11 is in marked disagreement with the Enskog dense-gas theory.
Secondary Reactions in the Ion Chamber of a Mass Spectrometer
Authors: Marmet P. , Morrison J. D.
Published: January 2005

A study has been made with a mass spectrometer of the ionization efficiencies of a number of gases, using an ion source incorporating an electron velocity selector. It is found that the shapes of the I.E. curves are affected by numerous instrumental factors. These have been examined, and the data lead to the following conclusions. Ions may be formed on the walls of the ionization source, at energies different from those corresponding to the ionized states of the free molecules. Charge transfer reactions may occur between these bound ions, and other neutral molecules on the walls. The surface ions may subsequently become detached, and are detected at the collector of the mass spectrometer.

It is suggested that these ions formed by such processes may account for many of the spurious ``breaks'' often found in measured I.E. curves. The sharpness of the structure in the present curves indicates that the half-width of the electron energy spread is of the order of 0.02 ev.
ESR Studies on the Formation of Sulfur Radicals in Irradiated Cysteine, Glutathione, and Djenkolic Acid
Authors: Henriksen Thormod
Published: January 2005

The formation of sulfur radicals in irradiated cysteine, reduced glutathione, and djenkolic acid has been followed by qualitative and quantitative ESR measurements. In these compounds sulfur radicals are induced as the results of secondary processes, which are observed as time-dependent spectral changes. For the compounds under investigation these secondary reactions occur at different temperature levels. Thus, they proceed efficiently in cysteine at 193°K, in glutathione at room temperature, whereas for djenkolic acid, temperatures of about 100°C seem to be necessary. The results show that this formation of sulfur radicals may be described by a sum of first-order reactions.
Electron Paramagnetic Relaxation in Ionic Solutions
Authors: Pearson Ralph G. , Buch Tomas
Published: January 2005

The interaction of paramagnetic cations with paramagnetic anions in solution is considered. The resultant broadening of the paramagnetic resonance lines of one of the species can be used to measure rates of formation of ion-pairs in cases in which the interaction is strong. Experimental results are given for a number of ions in water and compared to theoretical rates of diffusion controlled reactions between ions of opposite charge. The effect of the presence of inert, diamagnetic ions in the solution is considered.
Composition Stability Limits of PbTe. II
Authors: Brebrick R. F. , Gubner E.
Published: January 2005

Small single crystals of Cu-doped, Fe-doped, and undoped PbTe have been saturated with either Pb or Te from an external phase between 400° and 884°C, quenched, and their Hall constants and conductivities have been measured. Small single crystals of 3×1018 cm—3, p-type PbTe pulled from nearly stoichiometric melts have been vacuum-annealed between 395° and 800°C for short times, quenched, and measured. The composition at the invariant melting point is at least 50.012 at. % Te (7×1018 holes/cm3 at room temperature) on the basis of the simplest applicable model. The Pb-rich solidus line crosses the stoichiometric line near 860°C. The range of stability is a maximum near 800°C and corresponds to 0.015 at. % (1.5×1018 electrons/cm3 for Pb-saturated PbTe and at least 7.7×1018 holes/cm3 for Te-saturated PbTe). Te-saturated PbTe precipitates excess Te with great rapidity above 600°C, the resulting precipitates behaving like a bulk Te-rich phase. Cu is a donor in PbTe and Fe is tentatively assumed to be a low-lying donor which is un-ionized at room temperature in n-type PbTe. Our previous results for PbTe saturated with Pb at 800°C and below, including the room-temperature instability, are shown to be in error due to a subsequently detected Cu impurity. Our new results suggest that the predominant atomic point defects in PbTe are Pb vacancies and Te vacancies.
Optically Active Lattice Vibrations of α-Uranium Trioxide
Authors: Tsuboi Masamichi , Terada Minoru , Shimanouchi Takehiko
Published: January 2005

Infrared absorption spectra of α—UO3, β—UO3, U3O8, and UO2 have been observed in the spectral region from 4000 down to 90 cm—1. By assuming a modified central force field for the previously determined crystal structure of α—UO3, frequencies of the four infrared-active and two Raman-active lattice vibrations have been calculated. On the basis of the results of these calculations and on the basis of the comparison of the four spectra, all of the eight bands observed for α—UO3 are reasonably assigned either to the infrared-active fundamentals or to infrared-active combination tones. Brief discussions are also given on the force constants obtained for α—UO3 and on the absorption bands of other three uranium oxides.
Studies of Hydrogen Peroxide: The Infrared Spectrum and the Internal Rotation Problem
Authors: Redington R. L. , Olson W. B. , Cross P. C.
Published: January 2005

Several hydrogen peroxide infrared absorption bands have been obtained under 0.2 cm—1 resolution. They demonstrate both doubling due to internal rotation and effects due to the inertial asymmetry. The ground-state rotational constants are found to be: A″=10.068 cm—1, B″=0.8740, C″=0.8384. These parameters indicate a wide dihedral angle for H2O2, as proposed in the following structure: OO bond=1.475 A, OH bond=0.950 A, dihedral angle=119.8°, and OOH angle=94.8°.

The constants are applied to the microwave data for H2O2 and the deuterated species. The ground-state splitting is found to be 11.44 cm—1, and this, used with the recently reported torsion at 317 cm—1, yields the barriers hindering internal rotation. They are Vcis=1300 cm—1 and Vtrans=300 cm—1. A simple correlation of the infrared doublings is attempted.
Reactions of CF3 Radicals with Perfluoroacetone
Authors: Gordon Alvin S.
Published: January 2005

A homogeneous reaction of perfluoro methyl radicals with perfluoroacetone leading to the product perfluoro t-butyl methyl ether is reported. The reaction to form the (CF3)2ĊOCF3 radical is proportional to the first power of both the perfluoro methyl concentration and the perfluoroacetone concentration, with an Eact=9.7±0.26 (std. deviation) kcal/mol. The reverse reaction of the (CF3)2ĊOCF3 radical decomposing to a perfluoro methyl radical and perfluoroacetone is 30.6±1.3 (std. deviation) kcal/mol, so that the heat of reaction to form the (CF3)2COCF3 radical is —20.9 kcal/mol.
Diffusion Kinetics in Radiation Chemistry. II. One-Radical-One-Solute Model; Calculations
Authors: Kuppermann Aron , Belford Geneva G.
Published: January 2005

The general diffusion-kinetic equations are applied to a one-radical-one-solute model of the radiolysis of dilute aqueous solutions. The validity of the prescribed diffusion approximation is examined. Results of calculations of the effect on the molecular and radical yields of the following parameters are given: solute concentration, solute depletion, shape of initial radical distribution, radical density, diffusion coefficients, and rate constants. Conditions under which a straight track of equal and equidistant spherical spurs can be replaced by either isolated spherical spurs or an axially homogeneous cylindrical track are examined.
Nuclear Quadrupole Resonance of N14 in Solid N2
Authors: Scott T. A.
Published: January 2005

Pure quadrupole resonance of N14 in the α phase of solid nitrogen has been studied in the temperature range from 1.5° to about 34.5°K. The resonance frequency at 4.2°K is 3.4873±0.0001 Mc. The line shape and relaxation times at 4.2°K are discussed. A hydrostatic compression to 130 atm at 4.2°K gives (dν/dP)4.2=33 cps/atm. The temperature dependence of the resonance frequency below 20°K has been analyzed in terms of a modified Bayer theory in which account is taken of volume expansion. The torsional frequency of oscillation of the molecule is found to be νt=1.12×1012 sec—1, and the quadrupole resonance frequency without zero-point vibrations is ν0=4.16 Mc. The resonance frequency decreases very rapidly as the phase transition at 35.6°K is approached and pure quadrupole resonance has not been observed in the β phase.
Comparison of the Classical Theories of Unimolecular Reactions
Authors: Thiele Everett
Published: January 2005

Three classical strong-collision-mechanism theories of unimolecular reactions, due to Slater, Kassel, and Giddings and Eyring have been rederived using Slater's new approach to rate theory. These derivations show the importance of the gap distribution problem, and help point the way toward further development of a nonlinear theory.
Quadrupolar Study of Barium in Barium Bromide Dihydrate by Proton Magnetic Resonance
Authors: McGrath J. W. , Silvidi A. A.
Published: January 2005

The Zeeman-split quadrupolar resonances for Ba137 in BaBr2·2H2O were measured by using coincident enhanced proton resonance as a detector. The principal axes of the electric field gradient were found to be oriented thus: x parallel to b, y parallel to c, and z perpendicular to the bc plane. a, b and c are the crystallographic axes. The asymmetry parameter is 0.73±0.01 and the pure quadrupole resonance frequency is 24.38±0.03 Mc/sec.
Energy Parameters in Adsorption
Authors: Ehrlich Gert
Published: January 2005

The energy quantities for chemisorbing systems derived from calorimetry, isotherms, rate studies, and steady state measurements are analyzed. It is shown that if equilibration of the adsorbed layer occurs rapidly before evaporation (as it does for most metals) and the kinetic processes are properly identified, then the energy parameters deduced from thermodynamic and kinetic measurements are comparable.
Mass Spectrometric Studies of Atom Reactions. I. Reactions in the Atomic Nitrogen-Ozone System
Authors: Phillips L. F. , Schiff H. I.
Published: January 2005

A method has been developed for following the kinetics of fast atomic reactions with a mass spectrometer. The method has been used to determine separately the rate constants for the following reactions which are relevant to an atomic nitrogen-ozone system. N+O3→NO+O2k1=(5.7±1.4)×10−13 cm3molec−1sec−1N+NO→N2+Ok2=(2.2±0.6)×10−11 cm3molec−1sec−1O3+NO→NO2+O2k3=(2.1±0.5)×10−14 cm3molec−1sec−1O3+O→2O2k4=(2.5±0.5)×10−14 cm3molec−1sec−1O+NO2→O2+NOk5=(2.5±0.6)×10−12 cm3molec−1sec−1These reactions have been used to interpret the observed changes of concentration with time for reactants and products of the N–O3 reaction. The concentrations of N2O and NO2 in the system were below the detection limits of the mass spectrometer, which is consistent with predictions based on the above rate constants. Evidence was obtained for the production by reaction (2) of vibrationally excited N2 molecules having energies greater than 23.4 kcal/mole. Such energetic molecules are not present in significant quantities in discharged O2 or N2.
Radiolysis of Methylcyclohexane. I. Liquid Phase
Authors: Freeman G. R.
Published: January 2005

The gamma-radiolysis of liquid methylcyclohexane has been studied over the dose range 0.40 to 35.0×1019 ev/ml. The initial 100 ev yields of the products are: H2, 4.80±0.07; (1-methylcyclohexene+methylenecyclohexane), 2.65±0.15; (3-methylcyclohexene+4-methylcyclohexene), 0.83±0.10; open chain heptene′, 0.33±0.02; open chain heptene″, 0.31±0.04; bi-methylcyclohexyl, 0.75±0.05; methylcyclohexylheptene, 0.13±0.02. Methylcyclohexyl-methylcyclohexene was a secondary product, resulting mainly from reaction of methylenecyclohexane and partly from reaction of 1-methylcyclohexene.

The values of the ratios of the olefin yields to the ``dimer'' yields in the cyclohexane and methylcyclohexane systems were compared with values of disproportionation to combination ratios for moderately bulky alkyl radicals in the gas phase. It was concluded that the major portions of the olefins and ``dimers'' in the radiolytic systems were formed by the disproportionation and combination of radicals. A steric hindrance effect probably has a small influence on the rate of the combination reaction.

It was illustrated that a polymerization reaction occurs, involving the olefinic products, although the polymer could not be characterized. The relative significance of the polymerization reaction increases with decreasing dose rate.
Mass Spectrometric Study of the Gaseous Molecules above AgSn, AuSn, and CuSn Alloys
Authors: Ackerman Marcel , Drowart Jean , Stafford Fred E. , Verhaegen Georges
Published: January 2005

Mass spectrometric technique has been employed to analyze the molecular beams effusing from mullite Knudsen cells containing Sn and alloys of Cu, Ag, and Au with Sn. From the experimental intensities of monatomic and diatomic species and the vapor pressure of Sn, the following dissociation energies are obtained: D0∘(Sn2)=45.8±4 kcal/mole,D0∘(AgSn)=31.6±5 kcal/mole,D0∘(AuSn)=57.5±4 kcal/mole,D0∘(CuSn)=41.4±4 kcal/mole.
Contribution to a Liquid-Like Theory of Rubber Elasticity
Authors: DiMarzio Edmund A.
Published: January 2005

The contribution to the configurational entropy of a rubber arising from the competition of chain segments for space is evaluated and the associated entropy force is derived. This is done by expressing the orientation-dependent packing entropy as a function of the number of bonds (vector lengths between segments) in each of the permitted directions and then expressing the number of bonds in each direction as a function of the stretch ratios, λi. To make the calculations tractable, the three-chain model of a rubber is used and in addition only three mutually perpendicular orientations of the bonds are allowed. The predicted stress-strain curves are compared with the experimental situation. It is found that, for a dry rubber, the correction term has the same behavior at small and moderate elongations as the difference between the experimentally observed curve and the curve predicted by the uncorrected statistical theory. However, the magnitude of the correction term is from 1/10 to ½ the magnitude of the observed difference. It is concluded that one must go outside the equilibrium statistical mechanics to explain the magnitude of the observed deviation, but it is argued that the molecular basis of the deviation is the orientation-dependent packing problem.
Axiomatic Treatment of Chemical Reaction Systems
Authors: Wei J.
Published: January 2005

To represent a chemical system, a kinetic model must possess certain qualitative characteristics (such as convergence to an equilibrium point, decrease of entropy, etc.). The nature and interdependence of these characteristics are examined. An axiomatic system is presented in which some of these characteristics appear as axioms and others as derived theorems. The convergence to equilibrium points leads to a discussion of Liapounov functions. The relation of these functions to the thermodynamic functions entropy and Gibbs free energy are discussed.
Centrifugal Stretching of CClF3 and Some Other Symmetric Tops
Authors: Johnson R. C. , Williams Quitman , Weatherly T. L.
Published: January 2005

Recently, CCl3F and CHCl3 were each reported to have a negative DJ which varies with J. Centrifugal stretching of CClF3 was examined because of bonding similar to CCl3F. The J=1→2 through 4→5 transitions for CCl35F3 are reported; these data yield B0=3335.596 Mc, eqQ=—77.98 Mc, DJK=+2.06 kc, and for DJ the constant value +0.59 kc. A comparison of theoretical and observed constants for nine XYZ3 molecules shows fair agreement for all except CCl3F and CHCl3, the only molecules considered having three identical nuclei with quadrupole moments.
Concerning Relaxation of Plane Laminar Flow
Authors: Hollingsworth C. A. , Granquist W. T.
Published: January 2005

The relaxation of laminar flow between plane parallel plates is treated. In particular the effect of the rate of stopping of the moving plane is considered.
Initial Kinetic Energy Discrimination Effects in Crossed-Field Ion Sources
Authors: Coggeshall Norman D.
Published: January 2005

Previously developed differential equations for crossed-field trajectories are particularly suitable for investigating the characteristics of the orbits in crossed-field ion sources of mass spectrometers. At low repeller voltages there can be enormous initial kinetic energy discrimination due to the cycloidal orbits turning around before reaching the plane of the first slit. Energy relations for collectible orbits will be presented. A transformation of angle may be made between the isotropic distribution of initial velocity components to the anisotropic distribution of orbits that applies in the beam defined by the first slit. The latter will depend upon the operating conditions and may be studied by deflecting the beam across the exit slit by varying the deflection voltages. The signal reaching the detector then represents a progressive lateral sampling of the beam. The width and maximum intensity in this beam are functions of operating conditions and it is shown how very misleading results may be obtained depending upon how the exit slit samples this beam. Collection efficiency can be defined and set up as an integral of a function of the projected initial kinetic energy components on the plane of motion. The area under the curve obtained by progressively pushing the beam from the first slit across the exit slit represents the flux of ions collected by the first slit. This is dependent on operating conditions and may be conveniently used to investigate initial kinetic energies.
Absolute Raman Intensities. I. Method for Molecules in the Gas Phase
Authors: Golden David M. , Crawford Bryce
Published: January 2005

A method of determining absolute gas-phase Raman intensities is described, with performance parameters for a Cary model 81 gas-phase spectrograph. The method is closely related to that of Yoshino and Bernstein; the basic calibration comparison is to the rotational Raman lines of hydrogen.
Correlations at the Critical Point
Authors: Fixman Marshall
Published: January 2005

An extension of the Ornstein—Zernike approach to the determination of the radial distribution function function g (r) in the critical region is given. Nonlinear terms in the equation for the local pressure as a function of local density are introduced, the significant terms being determined from the shape of the coexistence curve. For a two-dimensional lattice gas, g2(r)—1=G2(r)∼0.86r—¼ at the critical point, in reasonable agreement with the Kaufman—Onsager result: G2(r)∼0.78r—¼. In a three-dimensional lattice gas at the critical point, G3(r)∼r—1(lnr)—½ if the coexistence curve has a quadratic top; otherwise G3(r)∼r—1.
Theory of Multicomponent Fluid Mixtures. III. A Pseudo Pair Potential
Authors: Salsburg Zevi W.
Published: January 2005

This article considers some further consequences of the exact statistical mechanical theorem (given in article I of this series) which relates the thermodynamic properties of a mixture to those of a fictitious pure fluid by defining an intermolecular potential function (called the pseudopotential) for this pure fluid. Starting with the perturbation series for the pseudopotential all terms which can be written as a sum of pairwise interactions are collected and summed to give a simple closed expression for a pseudo pair potential function for the mixture.

Retaining only these pair terms and neglecting all triplet and higher-order interactions in the pseudopotential gives an approximation which is a rigorous lower bound to the correct pseudo-potential for all configurations. For mixtures of molecules with rigid cores this pseudo pair potential is also a potential with a rigid core, but with a diameter equal to that of the smallest molecule. The extreme nature of this approximation, which severely limits the application of the theory at high densities and pressures, is shown to be a direct consequence of neglecting triplet interaction terms in the pseudopotential. The nature of the limitations inherent in any approximation of the pseudo-potential by a sum of pair-wise interactions is clarified by comparing these results with the random mixing approximation to the pseudopotential which is known to give an upper bound for all configurations. The free-volume theory for the pseudo pair potential, resulting from summing the pair terms, for mixtures of rigid spheres is developed. The results of this calculation are compared with recent Monte Carlo calculations for binary mixtures of rigid spheres to illustrate the extremely ``soft'' equation of state which results when triplet interactions are neglected.
Thermoluminescence of Solid Nitrogen after Electron Bombardment at 4.2°K
Authors: Brocklehurst Brian , Pimentel George C.
Published: January 2005

Solid nitrogen annealed at 20°K and then bombarded with electrons at 4°K gives three glow peaks on warming, at 10°, 14.5°, and 19°K. Unannealed nitrogen gave broader peaks. A feeble, long-lived glow followed the normal afterglow after bombardment at 4°K. Thermal effects during warming were observed in one apparatus with radiation shielding at 77°K, but they were not observed in a much more sensitive apparatus with radiation shielding at 4°K. The thermal effects are probably caused by an anomalous vapor pressure and loss of Dewar vacuum.

The data are discussed with reference to two interpretations, the storage of 2D excited nitrogen atoms and the recombination of 4S nitrogen atoms through diffusion. The latter explanation is preferred and a simple model is offered to account for the three diffusion activation enthalpies implied by the three thermoluminescence peaks.
Formation of Spin Centers in Carbons by Oxidation
Authors: Antonowicz K.
Published: January 2005

It was found that a high concentration of electron spin centers is obtained in carbons originally heat treated to a temperature of 1000°—2400°C by heating such carbons to 700°—1100°C in an oxidizing atmosphere. The conditions for the most efficient formation of spin centers by oxidation are: a temperature of about 800°C or somewhat higher, gas pressure above atmospheric, and a proper duration of heating. The presence of spins was detected using the usual experimental techniques of paramagnetic spin resonance absorption. Spin centers were created in various types of carbons (hard, soft, and carbon blacks). The shape and width of the paramagnetic resonance line vary greatly depending on spin concentration and on the original heat-treatment temperature of the carbon. In general the g value is close to or slightly higher than that for the free electronic spins. The experiments show that the presence of spin centers in equilibrium with an oxidizing gas is the result of the operation of two opposing mechanisms, one creating and the other destroying the centers. The creation occurs as a result of a direct chemical attack on the crystal surface. The destruction at high temperature is a result of the improvement of the crystal surface by atomic diffusion. Studies of the dynamics of formation and destruction of spin centers were carried out. The temperature dependence of spin absorption indicates a continuous change in character of spin centers with change in heat-treatment temperature. For low heat treatments the spin centers show a localized broken edge-bond character. With increasing heat-treatment temperature of a carbon the spin centers gradually change in their character into ``metallic'' conduction band electrons.
Valence-Bond Calculation of Geminal Spin-Spin Coupling Constants in Substituted Methanes
Authors: Barfield Michael , Grant David M.
Published: January 2005

A theoretical study is presented of geminal proton spin-spin coupling constants for a class of substituted methanes. Using a valence-bond approach and a six electron model, consisting of a methylene group with an adjacent π electron pair, the hyperconjugation energy and the contact contribution to the geminal coupling constant are calculated. These data, which are in agreement with the experimental findings, indicate that hyperconjugative effects give larger coupling constants than would be expected on the basis of the H–C–H angular dependence alone. This is shown to arise out of delocalized structures, which in the ground state correlate the spins of the geminal protons. It is noted that the geminal coupling constant depends on the orientation of the methylene group with respect to the adjacent π electron system, and this data is reported for two values of the C–C internuclear distance.