bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Chemical Combination on the X-Ray K Emission Spectra of Oxygen and Fluorine
Authors: Fischer David W.
Published: January 2005

Band shapes, wavelengths, and intensities are presented and discussed for the K emission spectra of oxygen and fluorine from some simple oxides and fluorides. It is shown that band shapes and peak positions are dependent upon the target material from which they are emitted. Evidence is presented illustrating that this dependence is in part due to such solid-state properties as crystal structure, valence, and coordination.

Results were obtained from a flat-crystal vacuum spectrometer with a thin window flow proportional counter using electron excitation.
Intrinsic Viscosity of Polymer Chains
Authors: Pyun Chong Wha , Fixman Marshall
Published: January 2005

The intrinsic viscosity [η] of polymer chains is recalculated by methods similar to those of Kirkwood and Zimm. The theory is based on the preceding paper by Fixman, with the adoption of a smoothed excluded-volume potential and the following first-order approximation to the operator L which determines the segment coordinate distribution function ψ; for L acting on the nonequilibrium part of ψ, only the diagonal part of L in the free-draining basis representation is used. This corresponds qualitatively to the Zimm theory in Hearst's version. However, the avoidance of preaveraging the Oseen hydrodynamic interaction tensor in the present work leads to larger values for the relaxation times of various normal modes when the hydrodynamic shielding effect is not negligible. The effect is more pronounced for lower modes, amounting to about eight percent increase in the lowest mode excited by the velocity gradient in the nondraining limit. The value of [η] in the same limit is found to be [η]=2.68×1023 L3/Mw (L: the root-mean-square end-to-end distance, Mw: the molecular weight of the polymer; cgs units) and is about 5% lower than that obtained by the Zimm treatment. A similar correction to the flow birefringence extinction angle is also given.
Energy Migration and Localization Processes in γ-Irradiated, Amorphous n-Alkyl Disulfides
Authors: Truby Frank K. , Wallace Duane C. , Hesse James E.
Published: January 2005

It was previously determined that amorphous alkyl disulfides irradiated at 77°K contain ionic species, alkyl radical species, and RS· radical species. The current study has been undertaken in order to determine the relative amounts of these species as a function of alkyl chain length in an effort to understand more clearly the energy migration and localization processes which occur in these compounds. It was found that no significant dependence of alkyl chain length (from methyl disulfide through eicosyl disulfide) occurs for the yield of ion pairs formed as a result of charge migration to the sulfur. This study indicates that essentially all free charge created in these compounds as a result of exposure to ionizing radiation migrates to and localizes at the disulfide group. From examination of the alkyl and RS· radical yields in these compounds as a function of chain length, it appears that excitation also localizes at the disulfide group. However, the localization of excitation at the sulfur group occurs less readily than does charge localization. Models concerning possible mechanisms for localization of excitation are discussed. Utilizing the models presented, the results of this study indicate that the probability for localization of excitation at the disulfide group is about seven times greater than that for localization of excitation at any CH2 group.
Bounds for the Derivatives of the Free Energy and the Pressure of a Hard-Core System near Close Packing
Authors: Fisher Michael E.
Published: January 2005

A simple argument shows how bounds to the derivatives of the free energy (or other thermodynamic potentials) may be derived from bounds to the free energy itself. The method is applied to study the divergence of the pressure p as a function of specific volume v for a system of particles with hard cores near close packing, Υ = [(v/vmin) − 1]→0. For a classical d-dimensional system with oriented ``cubical'' hard cores we prove that ξ1d/Υ≤p(v)vmin/kBT≤ξ2d/Υ,where the constants satisfy 0<ξ1<1<ξ2<∞. For a general hard-core system we establish only η1lnΥ−1≤p(v)vmin/kBT≤η2(lnΥ−1)d/Υfor any η1<1<η2.
Primary Process in the Photolysis of Ethane at 1236 Å
Authors: Akimoto Hajime , Obi Kinichi , Tanaka Ikuzo
Published: January 2005

The photolysis of ethane has been carried out at room temperature at the krypton resonance lines. The isotopic analyses of products in the photolysis of C2H6+C2D6 mixtures and CH3CD3 have been made to obtain information on the primary processes. From these results, the relative weights of the primary processes have been determined as follows: C2H6*→C2H4*+H2  41C2H4*→C2H2+H2  27C2H4*→ lim +MC2H4  14C2H6*→C2H4+2H  31C2H6*→CH4+CH2  22C2H6*→2CH3  <6These results agree with those reported by Hampson and McNesby.
Measurement of the Hall Effect in Metal—Ammonia Solutions
Authors: Kyser D. S. , Thompson J. C.
Published: January 2005

The Hall effect in solutions of Li (1.5 to 20 mole % metal), Na (0.3 to 8 mole %), and Ca (4 to 9 mole %) in liquid ammonia has been measured. Solutions above about 4 mole % were found to have a free-electron (metallic) Hall coefficient given by RH = (ne)−1, where n is the metallic valence-electron concentration. The corresponding Hall mobility is related to the metal concentration x, expressed in mole percent metal, by the simple power law μ∝x2m, where m is about 2.2 in Li and Na Solutions, and 1.0 in Ca solutions. The mobility increases from 0.6 cm2/V·sec at 5 mole % to 20 cm2/V·sec at 20 mole %. Upon dilution below 4 mole %, the Hall coefficient and mobility rapidly increase several orders of magnitude. This effect is indicative of a metal—nonmetal transition. The mobility of a Na solution has a maximum of 200 cm2/V·sec at 0.5%. The experimental techniques are discussed briefly and the results are compared with other experiments.
Energy-Minimum Principle for Hartree—Fock Calculations of Certain Excited Atomic States
Authors: Perkins J. F.
Published: January 2005

An energy-minimum principle, 〈E〉≥Eexact, for Hartree—Fock calculations of atomic states not the lowest of a given symmetry, is shown to hold under conditions which are satisfied for a large number of optical states, without the necessity of constraining the trial function to be orthogonal to wavefunctions of lower states of the same symmetry. The principle follows from application of a theorem by MacDonald and by Hylleraas and Undheim to an expansion-type Hartree—Fock procedure in which the radial function of the excited electron is expanded in a fixed basis set while all other orbitals are assumed fixed.
Condensation of Tungsten on Tungsten in Atomic Detail: Monte Carlo and Statistical Calculations vs Experiment
Authors: Young Russell D. , Schubert David C.
Published: January 2005

The preceeding paper reports the arrangement of tungsten atoms evaporated onto a low-temperature tungsten substrate. The present paper gives the results of Monte Carlo and statistical calculations assuming that the condensing atoms either remain in the first potential well they encounter upon contacting the surface (migration-free condensation) or make one or more surface migration ``jumps'' before being permanently bound. A comparison of the two calculations with experimental results leads to the conclusion that, at least below 77°K, tungsten atoms remain in the first potential well they encounter. It is shown that migration-free condensation is predicted by a one-dimensional calculation. Caution must be exercised in applying one-dimensional calculations to real surfaces.
Trapping of Triplet Excitons and the Temperature Dependence of Delayed Fluorescence in Anthracene Crystals
Authors: Siebrand W.
Published: January 2005

Singh and Lipsett have observed that the intensity of fluorescence due to triplet—triplet annihilation in anthracene crystals exhibits an anomalous temperature dependence involving several distinct maxima. It is shown that this behavior can be understood on the basis of trapping of triplet excitons. A simple kinetic model leads to the conclusion that every trapping level with a triplet lifetime long compared to the lifetime of a ``free'' triplet exciton gives rise to such a maximum. In favorable cases these observations can be analyzed completely in terms of depths, concentrations, and triplet lifetimes of traps. An analysis of Singh and Lipsett's data is presented. It leads to a broad continuum of trapping levels with depths ranging from about 3000 cm−1 to very small values, and two more or less discrete traps with depths of about 650 and 130 cm−1, respectively. The shallower traps are shown to have the higher concentrations and the longer triplet lifetimes. Indirect evidence is presented for the existence of still shallower traps with a very short triplet lifetime. The nature of these traps is discussed.
Crystal Structure of Piezoelectric Ferromagnetic Gallium Iron Oxide
Authors: Abrahams S. C. , Reddy J. M. , Bernstein J. L.
Published: January 2005

The crystal structure of Ga2—xFexO3, with 0.7≤x≤1.4, has been determined at 298°K by x-ray diffraction. Ga2—xFexO3 crystallizes in the orthorhombic system, space group Pc21n, with lattice constants a = 8.7512±0.0008, b = 9.3993±0.0003, c = 5.0806±0.0002 Å and eight formula weights in the unit cell. The complete scattering pattern was measured with PEXRAD to (sinθ)/λ≤1.02 Å−1. One gallium atom in the asymmetric unit is in a tetrahedral site, the other gallium and the two iron atoms are in octahedral sites. For x>1, the excess iron partly occupies the octahedral gallium site: the iron sites are to a smaller extent occupied by gallium. The gallium tetrahedron is very nearly regular, with Gatetr−0 = 1.846±0.005 Å. The gallium octahedron is irregular, with average Gaoct−0 = 2.026±0.004 Å; the iron octahedra are somewhat more irregular, with average Feoct−0 = 2.036±0.004 and 2.049±0.004 Å in the two crystallographically independent octahedra. The oxygen atoms pack in pseudohexagonal layers with a double-hexagonal close-packed repeat. The absolute configuration has been determined by the anomalous scattering: the positive sense of the polar b-axis is essentially parallel to an 0→Gatetr bond. The thermal vibrations in the crystal are isotropic, with a characteristic temperature Θ of 534°K. The magnetic spin structure has been deduced, and an atomic mechanism postulated for the piezoelectric effect, in terms of the crystal structure.
CO Oxidation. I. Induction Period Preceding CO2 Formation in Shock-Heated CO–O2–Ar Mixtures
Authors: Sulzmann K. G. P. , Myers B. F. , Bartle E. R.
Published: January 2005

The time history of the reaction processes occurring behind shock waves through argon-diluted mixtures of CO and O2 containing at most 1 ppm hydrogenous compounds has been studied spectroscopically between 1500° and 3000°K. The initial reaction regime was investigated by using spectral portions of the CO-fundamental and CO2−ν3-fundamental infrared bands and spectral portions of the ``CO-flame emission.'' An induction period has been observed which precedes the onset of measurable electronic ground-state CO2 formation and atomic oxygen production. The induction period is inversely proportional to the square roots of the initial mole concentrations of CO and O2. The temperature dependence of the induction time for the initiation of CO2 formation can be represented by an ``apparent activation energy'' which varies from 22 kcal/mole at 1500°K to 40 kcal/mole at 3000°K. Addition of 0.1% H2 results in a decrease of the induction period and a decrease of ``apparent activation energy'' for the induction period. At temperatures above 2400°K, the contamination by hydrogenous species becomes negligible and the induction period is attributed to the mechanism CO+O2→CO2+O,(M+)CO+O→(M+)CO2*,CO2*+O2→CO2+20.Based upon this mechanism the rate coefficients for Reactions (I) and (II) were determined to be: kI=(3.5±1.6)×1012exp[−(51 000±7000)/RT] cm3 mole−1·sec−1and kIII=(1.4±1.1)×1014exp[−(39 000±7000)/RT] cm3 mole−1·sec−1,respectively, for 2400°K≤T≤3000°K.
Liquid Phase Separation and Liquid—Vapor Equilibrium in the System Neon—Hydrogen
Authors: Streett W. B. , Jones C. H.
Published: January 2005

Liquid—vapor equilibrium phase compositions for the binary system neon—hydrogen have been determined at 10 temperatures in the range 24.59°—33.73°K and at pressures up to 200 psia. The system exhibits a phase separation in the liquid with an upper consolute temperature of 28.96°K, and an azeotrope in the region from about 12 to 20 mole % neon. The results are presented in both tabular and graphical form, and the general behavior of the system is discussed. A comparison with some earlier data is given. The experimental equipment, which includes a vapor-recirculating equilibrium system, a vapor-pressure-controlled liquid-neon bath, and a thermal-conductivity gas analyzer, is briefly described.
Photoelectron Ejection from Aromatic Negative Ions in Rigid Media
Authors: Van Voorst J. D. W. , Hoijtink G. J.
Published: January 2005

A study is made of the photoejection of electrons from negative hydrocarbon ions in a glassy solution of 2-methyl tetrahydrofuran at 77°K. The irradiation leads to a conversion M=→ lim hpM−+e−or M−→ lim hpM+e−.The threshold for photo-oxidation appeared to be dependent on the nature of the aromatic species. By using light with an energy below this threshold the photoreaction can be reversed. The ejected electrons give rise to (i) an optical-absorption band in the near infrared with ε=3–4×104 at the point of maximum absorption (7.7 kK) and (ii) an ESR signal at g=2.002 with a width of 4.5 G. It is shown that the ejected electrons are trapped by cavities in the rigid solvent. A lower limit of about 10−2M is found for the concentration of cavities suitable for trapping electrons.
Crystal Field of Some Monoclinic Rare-Earth Chlorides
Authors: Harrop Ian H.
Published: January 2005

The 15 crystal-field parameters Bkq=〈rk〉Akq for monoclinic ErCl3·6H2O were found to be B20=116,B22=158,B̄22=−262,B40=−88,B42=−193,B̄42=346,B44=332,B̄44=158,B60=−9.8,B62=−70,B̄62=141,B64=238,B64=−119,B66=238,B̄66=−11.When used together with Wybourne's free-ion wavefunctions, the field adequately explains most of the observed Stark and Zeeman splittings. The Bkq, modified by the calculated 〈rk〉 of Freeman and Watson, are appropriate for several ions and, in all, account for about 200 independent data. A possible systematic variation of the Akq for odd and even electron ions is pointed out. The Zeeman splittings of the 6P7/2 and 6P5/2 states of GdCl3·6H2O are explained, and the use of the Gd3+ ion as a crystal-field probe is discussed.
Ultrasonic Relaxation and Axial—Equatorial Isomerization in Methylcyclohexane. II
Authors: Piercy J. E. , Subrahmanyam S. V.
Published: January 2005

The ultrasonic absorption of pure liquid methylcyclohexane has been measured with a pulse technique over a frequency range of 0.6 to 10 Mc/sec from 60° to 120°C. These measurements together with those of the pure liquid previously recorded in the literature are consistent with a single relaxation process, the interchange of axial and equatorial isomers, with values of 2.9±0.5 kcal/mole and 3.2±0.6 cal/mole·°C for the difference in enthalpy and entropy, respectively, between axial and equatorial isomers, and 10.3±0.6 kcal/mole and 2.0±2.0 cal/mole·°C for the enthalpy and entropy of activation, respectively, for the conversion of axial into equatorial isomers. These results are in agreement with those derived from solution measurements with a streaming technique in Part I. They replace conflicting conclusions concerning the relaxation in methylcyclohexane recorded in the literature, which are shown to be without adequate foundation. The measurements are used to illustrate some common errors in the derivation of molecular parameters from ultrasonic measurement. The connection with conformational analysis and other physicochemical measurements is discussed.
Cross Sections for Dissociative Ionization of Molecules by Electron Impact
Authors: Rapp Donald , Englander-Golden Paula , Briglia Donald D.
Published: January 2005

Cross sections for dissociative ionization have been measured as a function of electron energy from threshold to 1000 eV in nine gases (H2, D2, N2, CO, NO, O2, CO2, N2O, and CH4) by collecting those ions reaching the ion collector after passing through a 0.25-V retarding potential in a total-ionization tube. Approximate correction is made for the effective solid angle subtended by the ion collector at the electron beam. The results are reported as the fraction of total ionization, and as absolute cross sections for dissociative ionization. At moderately high electron energies (>70 eV), the fraction of total ionization that is dissociated ions with kinetic energy in excess of 0.25 eV, ranges from ∼7% in H2 and D2 to ∼35% in N2O, with other gases intermediate.
Oscillator Strength of the CN Red System
Authors: Jeunehomme M.
Published: January 2005

The red system of CN is produced in emission by running a pulsed electrodeless discharge in acetonitrile. The extrapolation at zero acetonitrile pressure of the fluorescence decay time is accepted as the lifetime of the A 2Π state of CN. The lifetime values vary slightly from one vibronic level to another. The dependence of the electronic part of the transition moment over the nuclear coordinates is deduced from this variation. A value of 3.4×10−3 is recommended for the oscillator strength f(0, 0) of the CN red system.
Motion of the H2O Molecule in Barium Bromate Monohydrate
Authors: McGrath J. W.
Published: January 2005

The PMR doublet splitting was measured for barium bromate monohydrate in the range 195° to 373°K. Two orientations of the crystal were used so as to observe the effects of torsional and rocking motions of the H2O molecule. Torsional vibrations caused a decrease of about 0.47 G in splitting from low to high temperatures. The reduction was about 0.14 G for rocking motion. The root-mean-square amplitudes of the motion at 0°K were computed to be about 11° and 8° for the torsional and rocking motions, respectively. The torque constants were found to be about 16 and 30 kcal/mole·rad2 for torsion and rocking, respectively. The value of the proton—proton separation is 1.54 Å when results are corrected for motional effects.
Diffusion of Zn2+ in Single-Crystal MgO
Authors: Wuensch B. J. , Vasilos T.
Published: January 2005

Diffusion coefficients for Zn2+ in single-crystal MgO have been determined in the temperature range 1000°—1650°C from concentration gradients obtained with the aid of electron microbeam probe spectroscopy. The variation of the diffusion coefficients with temperature yields an activation energy for diffusion of 1.85 eV, and D0=1.48 10−5 cm2/sec. The oxides display appreciable solid solubility in one another, but the range of solid solution of ZnO in MgO greatly exceeds that for MgO in ZnO.
Motions of Molecules in Condensed Systems. XIII. Polarized Infrared Spectrum of Single Crystals of Diacetylene
Authors: Freund Isaac , Halford Ralph S.
Published: January 2005

The polarized infrared spectra of single crystals of diacetylene, as well as those of the liquid and the vapor, are presented and analyzed. Modes forbidden activity in the vapor are observed in the spectra of the condensed phases, as are combinations of molecular fundamentals with lattice modes. The crystal and liquid spectra exhibit frequency shifts and band broadenings that are characteristic of hydrogen bonding. The crystal system is found to be either orthorhombic or monoclinic with two or more molecules in the primitive unit cell. The molecules are essentially coplanar and this plane is the only symmetry element that may be present at the site. An orthorhombic structure, of Space Group P22121 with four molecules on sites of no symmetry, is proposed for the crystal.
Composition Change of Binary Compounds Under Conditions of Equilibrium and Vacuum Vaporization
Authors: Somorjai G. A. , Lester J. E.
Published: January 2005

The composition of binary compounds changes as a function of temperature when in equilibrium with the vapor. This change, for the IIB—VIA and IA—VIIA compounds is small, within the limits of solubility. The equilibrium vacancy concentrations are controlled by their free energies of formation. The composition changes in a different manner when the solid is heated in vacuum. Vacuum evaporation rates are controlled by the activation free energy of a surface reaction which, under proper conditions, may also control the bulk concentration of vacancies. Experimental verification of this effect is proposed. It has been shown that closed system vapor-pressure measurements are extremely sensitive to minute changes of the solid composition. The measured apparent vapor pressure is a function of the reaction-chamber volume for composition changes ≥2×10−8 mole/cm3. In turn, the sensitivity of closed-system vapor-pressure measurements may be used for accurate determination of off stoichiometry.
Refractive Index and Lorentz—Lorenz Function for Saturated Argon, Methane, and Carbon Tetrafluoride
Authors: Abbiss C. P. , Knobler C. M. , Teague R. K. , Pings C. J.
Published: January 2005

By means of the principle of minimum deviation, the refractive index was determined for argon, methane, and carbon tetrafluoride as saturated liquids from the triple point to the critical point. For argon, some measurements were also made on the saturated gas. For argon and methane, known values of the densities were used to compute the Lorentz—Lorenz function over the entire range of the saturation curve. For carbon tetrafluoride these computations were made only up to 0.7 of the critical temperature due to the lack of density data at higher values. The Lorentz—Lorenz function varies little with density and temperature for the three liquid phases. The argon measurements indicate definite increases in the Lorentz—Lorenz function on isothermal condensation.
Liquid—Solid Phase Equilibria in the Hydrogen—Deuterium System
Authors: White David , Gaines J. R.
Published: January 2005

The phase behavior of mixtures of parahydrogen and normal deuterium, in the liquid and solid states, has been investigated. The calorimetric data show a continuous range of solid solutions from 8°K to the melting points. In the liquid—solid two-phase region the system can be characterized by a continuous series of liquid and solid solutions. The experimental data show no evidence of the phase separation in the solid state previously reported by Kogan, Lazarev, and Bulatova.
Self-Avoiding Random Walks. I. Simple Properties of Intermediate-Length Walks
Authors: Gans Paul J.
Published: January 2005

A new method is presented for the rapid detection of self-intersections in random walks generated by Monte Carlo processes. Reduction in required computer time made possible by this method allows the generation of walks containing significantly more steps than previously possible, thus corresponding to more realistic linear macromolecular dimensions. Results obtained by this method verify, for the tetrahedral lattice, a conjecture of Domb's that 〈Rn2〉, the mean-square end-to-end distance, increases essentially as the 6/5 power of n, the number of steps in a walk. In addition, a new parameter 〈xn〉 the average maximum x-axis extension of a walk, is calculated. The square of this parameter is found to have essentially the same exponential step dependence as 〈Rn2〉 and may be calculated more precisely than it. Further, 〈Dn2〉, the average maximum squared diameter of a walk estimated from 〈xn〉, having the property that essentially all of an average self-avoiding walk of n steps is contained within a sphere of squared diameter 〈Dn2〉, is shown to be approximately 2.2 times 〈Rn2〉. The results presented are valid to 1700 steps.
Polarization Effects in the Two-Photon Excitation of Anthracene Fluorescence
Authors: Peticolas Warner L. , Norris Robert , Rieckhoff Klaus E.
Published: January 2005

The polarization of the fluorescence of anthracene has been measured after two-photon excitation with ruby laser light. The anthracene molecules were rigidly held in a 2×10−3M solution in EPA glass at liquid-nitrogen temperatures. For comparison, the polarization of the fluorescence was measured from one-photon excitation at approximately twice the laser frequency. The measured polarization of the two-photon excited light is in satisfactory agreement with the polarization as calculated from the Goeppert-Mayer process involving a transition through an intermediate state. It is in disagreement with the polarization calculated in terms of the process recently suggested involving the A2 term in the Hamiltonian. Thus the measurement of the polarization of the two-photon fluorescent light appears to be one way of experimentally estimating the relative contribution of these two second-order processes.

The concentration and intensity independent quantity δ, which is the ratio of the cross section to the laser flux, was found experimentally to be 0.9×10−51 cm4·sec/atom·photon for anthracene molecules in a dilute glass.
Reaction of Atomic Hydrogen with Propylene at 77°K as Studied by Electron Spin Resonance
Authors: Hill Charles G. , Reid Robert C. , Strandberg Malcolm W. P.
Published: January 2005

Hydrogen-atom reaction rates with thin solid propylene films were studied at 77°K. Propylene was deposited on the walls of a quartz resonance cavity of an ESR spectrometer and hydrogen-atom concentrations were monitored during reaction. The hydrogen atoms were produced in a 2450 Mc/sec microwave discharge external to the cavity and either diffused into or were pumped through the reaction zone.

The products of the reaction were found to be propane and 2,3-dimethylbutane. The ratio of propane to 2,3-dimethylbutane in the products increased as the average hydrogen-atom concentration in the reactor increased. The product distribution and the variation of this distribution with hydrogen-atom concentration may be explained by the following sequence of reactions: CH3–CH=CH2+H→ lim k1CH3–ĊH–CH3,2 CH3–ĊH–CH3→ lim k2CH3–CH2–CH3+CH3–CH=CH2,[Complex chemical formula]CH3–ĊH–CH3+H→ lim k4CH3–CH2–CH3.

The rate constant k1 was found to be 1.8×106 cc/mole·sec at 77°K assuming that the monitored hydrogen-atom concentration was equal to that in the reaction zone.
Monte Carlo Calculations of the Dimensions of Polymers in a Restrictive Subvolume of Solution
Authors: Bluestone Sydney , Vold Marjorie J.
Published: January 2005

A polymer molecule is allowed to ``wiggle'' on a cubic lattice in the presence of a uniform segment density, simulated by reflecting barrier walls of a cubic box, and the compression of polymer-chain dimensions is computed as a function of the volume fraction of occupied lattice points (i.e., polymer concentration).
Photoluminescence of Lanthanide Complexes. IV. Phosphorescence of Lanthanum Compounds
Authors: Brinen J. S. , Halverson F. , Leto J. R.
Published: January 2005

The phosphorescence spectra have been obtained for several lanthanum tris chelates, and these data have been used to locate the lowest triplet levels of the ligands. The triplet levels show a steady progression in energy, with differing singlet—triplet splittings for various ligands.
Diffuse Reflectance Spectra of Some Thiometallates and Oxides of the Chromium Family
Authors: Companion A. L. , Mackin Martha
Published: January 2005

The visible and near-ultraviolet absorption spectra of NaCrS2, Cr2O3, (NH4)2MoS4, (NH4)2WS4, MoO3, and WO3 have been measured by diffuse reflectance methods. Peaks at 2.06 and 2.66 eV in Cr2O3 and 1.76 and 2.34 eV in NaCrS2 are interpreted as octahedral strong-field d3 4T2g and 4T1g transitions from the 4A2g ground state, consistent with Dq values of 0.206 and 0.176 eV and nephelauxetic ratios of approximately 0.48 each. Absorption edges in MoS42—, WS42—, MoO3, and WO3 are interpreted as charge transfer to localized MO's in the tetrahedral thiometallates, comparable to those observed in the chromate ion, and as charge transfer to delocalized bands in the oxides.
Proton Magnetic Resonance Studies of Solid Tetramethyls of Silicon, Germanium, Tin, and Lead
Authors: Smith George W.
Published: January 2005

Forty-megacycle-per-second proton magnetic resonance studies of solid Si(CH3)4, Ge(CH3)4, Sn(CH3)4, and Pb(CH3)4 have shown that methyl group reorientation occurs in all four compounds at temperatures as low as 77°K. T1 measurements show that the energy barrier to methyl reorientation in the X(CH3)4 family goes roughly as the inverse sixth power of the methyl separation. From linewidth measurements we find general molecular reorientation only in solid Si(CH3)4 and Ge(CH3)4 and only at temperatures just below the melting point. The activation energies are 7 and 10 kcal/mole, respectively. Self-diffusion was found only in the metastable α phase of Si(CH3)4—an interesting result since the entropy of melting of α-phase Si(CH3)4 is 8.34 eu, somewhat high for a plastic crystal. The experimental energy barrier to self-diffusion in α-phase Si(CH3)4 is about 6.2 kcal/mole. Proton magnetic resonance and thermal studies indicate that the X(CH3)4 family obeys the qualitative features of the Pople—Karasz theory of melting. A number of methods for calculating rigid-lattice and methyl-reorientation second moments are considered. A means is given for estimating the intermolecular contribution to the rigid-lattice second moment when the crystal structure is unknown but the density of the solid is known. The method agrees well with other calculations.
Nuclear Relaxation Processes in Systems of Two Spins
Authors: Mackor E. L. , Maclean C.
Published: January 2005

Nuclear relaxation in a system of molecules with two nonidentical spins (S and I) may originate from intra- or intermolecular interactions between like and unlike spins. An experiment is described which, in combination with the nuclear Overhauser effect, allows the determination of the contributions from the various interactions.

The spins (S=½, I=½) are supposed to be coupled by a small scalar interaction and four longitudinal magnetizations S+, S—, I+, I—, can be measured. The decay of the total magnetizations (S++S—) or (I++I—) was discussed by Solomon and Bloembergen.

The decay of the difference of the magnetizations (S+—S—) or (I+—I—) is a useful parameter as is shown in this paper. The relaxation time of (S+—S—) and (I+—I—) is related to the question whether the interactions are intra- or intermolecular. We have derived the appropriate equations for the time dependence of the difference magnetizations; the relaxation rate of the difference magnetization is larger for intermolecular dipolar interactions than in the intramolecular case when compared with the relaxation of the sum magnetizations.

Experiments on CHFCl2 at −142°, −115°, and at +20°C are reported. At temperatures just above the melting point both hydrogen and fluorine spins relax mainly by interactions between unlike spins; the contributions of intramolecular interactions are predominant. At 20°C it appears that the fluorine spin is relaxed by spin rotation and hydrogen by intermolecular dipole interactions.
Vibrational Relaxation of O2 in O2−D2 Mixtures and of H2 and D2
Authors: White Donald R.
Published: January 2005

Shock-tube interferometry has been used to observe vibrational relaxation of O2 in O2+D2 mixtures. From 300° to 850°K the present shock tube and previous ultrasonic relaxation times in atmosphere seconds are given by log10(pτO2−D2)=27.3T−13−8.35. Above 1500°K the relaxation time of O2 is further shortened due to effects of chemical reaction or possibly to a resonant-energy exchange with the more rapidly excited D2. Hydrogen vibrational relaxation is too rapid to be resolved, yielding pτH2<2×10−6 atm·sec for T = 1400°K. The vibrational relaxation of deuterium appears to be more complex than other diatoms studied and is not yet understood. However, it is observed that pτD2<6×10−6atm·sec at T = 1400°K.
On the Use of Oseen's Velocity Field in the Calculation of Electrical Conductance in Solutions
Authors: Friedman Harold L.
Published: January 2005

The electrophoretic term of the limiting law for conductance is evaluated using Oseen's expression for the velocity field generated in a fluid medium by the motion of an immersed ball. This expression accounts for the nonzero inertia and kinetic energy of the fluid, unlike Stokes' velocity field which is usually used in conductance theory. The electrophoretic term calculated in the framework of the Debye—Hückel conductance theory reduces to the classical result in the usual range of experimental conditions and also makes a very small contribution to the Wien effect for electric fields in the accessible range.
Thermal Desorption of Sr from W
Authors: Madey T. E. , Petrauskas A. A. , Coomes E. A.
Published: January 2005

A study of the kinetics of the thermal desorption of Sr from W has been performed in which the field electron microscope was used to identify the state of adsorbate—substrate system. The activation energy for the thermal desorption of Sr from W falls from 4.21±0.22 eV/atom at zero Sr coverage to 1.78±0.13 eV/atom at ``monolayer'' coverage. This latter value approaches the heat of sublimation of bulk Sr (1.69 eV/atom). The desorption energies found using field-emission techniques deviate markedly from the extrapolated thermionic results of Moore and Allison near θ=0 and for θ>0.5. A linear relationship was found to exist between the activation energy for desorption and the logarithm of the pre-exponential factor in the rate equation κ(kT/h) exp(ΔS‡/R).
Raman Spectral Studies of Alkaline Solutions of Germanium Dioxide
Authors: Walrafen G. E.
Published: January 2005

Raman frequencies, polarizations, and infrared frequencies of nearly saturated aqueous solutions of KOH containing various amounts of GeO2 (0.5 to 6.0 mole liter−1) have been obtained at 25°C, and relative integrated Raman intensities of bands of the alkaline solutions at 529, 667, and 765 cm−1 were also obtained for various stoichiometric GeO2 molarities, CGeO2, under conditions of nearly constant, and of varying stoichiometric KOH molarity, CKOH.

In the concentration ranges 0<CGeO2<6M, and 10.53<CKOH<14.87M, the relative integrated Raman intensity of the 765-cm−1 band, I765, was observed to be nearly proportional to CGeO2, which suggests that much of the germanium is present in one form, e.g., as H2GeO42—. However, marked downward deviations from proportionality observed for another intensity of H2GeO42—, I667, evident in the range ∼2<CGeO2<6M, indicate that appreciable concentrations of a second species, e.g., Ge2O52—, must contribute to the 765-cm−1 band intensity to produce the observed near proportionality. The species Ge2O52— is also thought to give rise to another band at 529 cm−1, the intensity of which increases from very low to measurable values in the range 0<CGeO2<6M, and the presence of more than one germanium-containing species is given additional support by polarization data.

Raman and infrared frequencies of solid Na2GeO3 and of vitreous GeO2, and infrared frequencies of hexagonal GeO2, also obtained in this work, are included, as are viscosity and electrical conductivity data for alkaline solutions of germanium dioxide.
Line-Breadth Study of the 1.64-mm Absorption in Water Vapor
Authors: Rusk James R.
Published: January 2005

The 2+2→3−2 rotational transition in water vapor has been carefully studied by using both a simple video and a double modulation millimeter wave spectrometer. The line center remeasured is ν0 = 183 310.12±0.10 Mc/sec. Self-broadening and foreign-gas broadening were investigated over the pressure range of 5 to 400 μ of Hg with the following results: Perturbing gasΔν/p (Mc/sec·mm)H2O19.06CO26.09N23.76O22.72Ar1.97.

These results, obtained by the double modulation spectrometer, have been compared with other line broadening studies, and for the first time linewidth calculations on asymmetric molecules appear to be valid.
Temperature Dependence of the III—II Transition Rate of KNO3 at Atmospheric Pressure
Authors: Nolta J. P. , Schubring N. W. , Dork R. A.
Published: January 2005

The existence of ferroelectric behavior in the Phase III polymorph of potassium nitrate has permitted the direct recording of the rate of transition of the Phase III to the Phase II at temperatures far removed from the normal transformation temperature at atmospheric pressure. The data presented indicates that the III—II transition may be described by two first-order processes which may each be described by a single rate constant. These rate constants as a function of temperature are given.
Studies of Infrared Emission from Shock-Heated Nitric Oxide
Authors: Fukuda Kuniya
Published: January 2005

The infrared emission from nitric oxide mixed with argon was measured. The gas was shock heated to temperatures ranging from 1000° to 2500°K. At the same time the density variations in the heated sample were examined with a Mach—Zehnder interferometer. For varied concentrations of nitric oxide and the range of temperatures covered the observed relative emission intensity at vibration equilibrium is in good agreement with that calculated by using the measured density and the vibrational oscillator strengths derived from the experiments of Penner and Weber. The vibrational relaxation time of nitric oxide is less than 1 μsec, in laboratory time, over the above temperature range, and the corresponding minimum collision transition probability is approximately 10−3.
Numerical Evaluation of Quantum Effects on Transport Cross Sections
Authors: Imam-Rahajoe S. , Curtiss C. F. , Bernstein R. B.
Published: January 2005

Quantum-mechanical calculations of the transport cross sections Q(1)☆ and Q(2)☆ and the associated Ω(n,t)☆ integrals for a Lennard-Jones (12, 6) potential are discussed. The computations are made for three values of the quantum parameter Λ* (=1, 2, 3), and include the effect of statistics. The quantum effects become quite important at reduced temperatures T* below about unity. The quantum corrections to the integrals are negative at moderate temperatures, but become positive at higher temperatures.
Transport Collision Integrals for Quantum Gases Obeying a 12–6 Potential
Authors: Munn R. J. , Smith Francis J. , Mason E. A. , Monchick L.
Published: January 2005

The transport collision integrals for the 12–6 potential have been calculated with exact quantal phase shifts. Tables of the collision integrals, accurate to 1 or 2 parts in 1000 over most of the temperature range, have been prepared for reduced temperatures kT/ε from 0.01 to 100 and for a number of values of the reduced de Broglie wavelength up to a value of 3.5 in steps of 0.5. The effects of statistics are included.
Direct and Inert-Gas-Sensitized Radiolysis and Photolysis of Methane in the Solid Phase
Authors: Ausloos P. , Rebbert R. E. , Lias Sharon G.
Published: January 2005

The photolysis of CH4–CD4 mixtures has been briefly investigated at 20.4°K using the xenon and krypton resonance lines. From the isotopic composition of the hydrogen and ethane fractions, it could be derived that, in the solid phase, methylene and methyl radicals are produced. The methylene radicals, which are formed by the process CH4*→CH2+H2, insert into methane to form ethane.

In the argon-sensitized radiolysis at 20.4° and 77°K, the hydrogen-molecule elimination process predominates, indicating that neutral excited-methane molecules are formed nearly exclusively. In the xenon-sensitized radiolysis, however, mainly hydrogen atoms and methyl radicals are observed. In all inert gas-sensitized radiolyses, there is a gradual decrease in the efficiency of the energy transfer with increasing dilution.

In the direct radiolysis, hydrogen atoms play a more important role than in the photolysis at 1236 Å. Radiolysis of CD4−C2H4 (1:0.01) mixtures indicated that, at 77°K, hydrogen atoms react with ethylene and propylene to form higher saturated hydrocarbons while, at 20.4°K, hydrogen atoms disappear mainly by recombination with other free radicals. From the isotopic composition of the ethylene fraction formed in the radiolysis of Ar–CH4–CD4 mixtures, it is surmised that a fraction of the methylene recombines to form ethylene.
Nonequilibrium Effects in the Kinetics of Isomerization Reactions and in the Kinetics of Dissociation and Recombination of Diatomic Molecules
Authors: Snider Neil S.
Published: January 2005

A study was made of the time evolution of a system of diatomic molecules undergoing dissociation and recombination and of a system of molecules undergoing isomerization. The starting point in each case was a master equation. The particular aims of the study were to determine the conditions under which the time evolution is describable by the appropriate phenomenological equation [Eq. (1) or (2)] and also to determine whether or not the phenomenological equations can hold under far from equilibrium conditions with forward and reverse rate constants whose ratio is not the equilibrium constant. In the isomerization it was found that the appropriate phenomenological equation [Eq. (2)] always holds after a sufficiently long time. In dissociation—recombination there exist systems in which the appropriate phenomenological equation [Eq. (1)] never holds. Certain necessary conditions involving rate constants for the elementary processes and the atom concentration must be fulfilled in order for this equation to ever hold. In both dissociation—recombination and isomerization the ratio of forward and reverse rate constants is always equal to the equilibrium constant when the phenomenological equations hold.
Atomic and Molecular Emission in the Negative Glow of a Helium Discharge
Authors: Hurt W. B. , Robertson W. W.
Published: January 2005

The spatial distribution of helium atomic and molecular radiation has been investigated in the negative glow of a dc discharge. The atomic radiation peaks sharply at the cathode edge of the negative glow, the molecular radiation less sharply at a greater distance from the cathode. Microwave quenching indicates that most of the atomic and all of the molecular radiation results from electron-ion recombination processes. The decrease in atomic radiation reflects the decrease in atomic ion concentration which is controlled primarily by diffusion away from the cathode and by three-body conversion to molecular ions. The molecular ions are lost by diffusion and by collisional—radiative recombination to the neutral molecule, with collisional processes predominating. The negative glow can be characterized as a plasma steady in time but with a one-dimensional spatial decay away from the cathode.
Sound Dispersion in Binary Mixtures of Halomethane Gases
Authors: Boade R. R. , Legvold Sam
Published: January 2005

Sound dispersion has been experimentally examined in all binary combinations of the halomethane gases, CH2F2, CHF3, CF4, CCl2F2, and CHCl2F. Concentrations of 25%, 50%, and 75% were examined in each combination. The experimentally determined vibrational relaxation time of each mixture was related to the equation τ−1=X2τAA−1+(1—X )2τBB−1+X(1—X) (τAB−1+τBA−1). A single relaxation time was observed in all the mixtures, and the above equation was found to be valid when the relaxation times of the individual gases in the mixture were similar and when their vibrational specific heats were similar. Values of (τAB−1+τBA−1) were deduced from the data and compared with values calculated from an extended version of the Schwartz, Slawsky, and Herzfeld theory. A Lennard-Jones 7–28 interaction potential was used for the calculations and appears to be an appropriate potential for these molecules.
New Lattice Model for the Statistical Mechanics of Quantum Fluids. I. Liquid Hydrogen and Its Isotopes
Authors: Benson Sidney W. , Marchi Raymond P.
Published: January 2005

A lattice-cell model for quantum fluids is proposed in which the thermal energy of the lattice is represented by the Debye equation for crystalline solids. The maximum Debye frequency vD is taken equal to the simulated frequency for a single hard-sphere molecule moving in an infinitely deep, cubic potential well. Lennard-Jones parameters from viscosity measurements on H2 are used to describe the van der Waals lattice energy. The only parameter in the theory is the equivalent hard-sphere diameter. This is determined from the molar volume of liquid H2 and is 2.79 Å, very close to the Lennard-Jones value of σ, 2.92 Å. Calculated values of the molar volumes of D2, T2, and the intermediate HD are in good agreement with observed values, as are the heats of vaporization and specific heats. Calculated values of the coefficients of compressibility and thermal expansion are too low, but the value of internal pressure (δP/δT)v is in excellent agreement with observed values.

The most interesting feature of the model is that it yields, for the first time, a lower free energy for the body-centered lattice than for the face-centered lattice. This reflects the importance of the increased free volume and hence lower zero point energy for the less compact lattices. The actual differences in free energy for different packings are small compared to RT near the boiling points and this suggests very large fluctuation in packing in the liquids. The relation to melting is discussed briefly.

Calculations show that the isotopic properties are very sensitive to the form of the repulsive potential.
Auto- and Cross-Correlation Functions Used as Tools for Information Retrieval in Electron Diffraction Structure Studies
Authors: Traetteberg M. , Bonham R. A.
Published: January 2005

Three radial distribution functions [f(r)], the power spectrum, the diagonal power spectrum, and the sharpened radial distribution function have been introduced, and it is shown that these functions might be useful tools in extracting molecular information from a gas electron diffraction experiment. The two kinds of power spectra are based on short-interval auto- and cross-correlation functions of the molecular intensity function, while the sharpened radial distribution function is defined as the Fourier sine transform of the product of the molecular intensity function and the antidamping function exp[—α(smax—s)]. The similarity between the power spectrum and the sharpened radial distribution function has been pointed out.

By examples based on experimental data and numerical calculations based on theoretical data it is shown that the modified f(r) functions introduced here give better resolution between neighboring peaks than the radial distribution function that is normally applied in electron diffraction structure studies.

The errors introduced in rij values determined from the various f(r) functions, due to additive random errors in the molecular intensity function, have been studied by numerical analysis, and it has been shown that accurate structural parameters can be extracted from sharpened f(r) functions.
Molecular Binding in the Limit of Very Large Spin—Orbit Interaction
Authors: Halley J. Woods , Shore H.
Published: January 2005

Binding energies and electronic wavefunctions are found for diatomic and methanelike molecules under the restriction that the electronic configuration contains only j = l—½ states. Two models for a diatomic molecule are treated. In the first, the electronic configuration is a p state on one atom and the effect of the other atom is included by a crystal field. In the second model the configuration is an s state on one atom and a p state on the other. The magnitude of the spin—orbit interaction required to make the restriction to j = l—½ states a good approximation is found in each case. In the second case, the binding is reduced by a factor of 3 by the restriction. In the methane molecule the restriction to j = l—½ states requires the inclusion of d states in the configuration. The binding of the methane can be increased by a distortion and experimental evidence for such a distortion in GeH4 and SiH4 is pointed out. Application of this approximation to the electronic structure of actinide complexes is briefly discussed.