bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption Spectra of the Solvated Electron in Polar Liquids: Dependence on Temperature and Composition of Mixtures
Authors: Arai Shigeyoshi , Sauer Myran C.
Published: January 2005

The effect of temperature on the absorption spectra of the solvated electron in various liquid alcohols is reported. From 25° to −78°C, the energy corresponding to the absorption maximum increases by 0.23, 0.35, 0.36, and 0.46 eV for methanol, ethanol, isopropanol, and n-butanol, respectively. Within experimental error there is no change in the width (in electron volts) of the absorption at half-maximum.

The absorption spectra of the solvated electron in several binary mixtures at room temperature are reported. In all mixtures examined the spectrum has only one peak at wavelengths intermediate to the absorption maxima of the pure components, and the exact position depends on the mixture composition. In 50:50 mixtures of many of the materials used, the absorption maxima and half-widths are closer to those of one pure component than of the other.

The fact that there is no evidence of two peaks in mixtures indicates that the solvation of the electron depends on the macroscopic properties of the solution in the sense that a particular electron interacts significantly with a large number of solvent molecules. However, the results indicate that at least in some mixtures the electron is associated on a microscopic scale preferentially with one component.

Partial spectra, at low temperature, of the solvated electron in the liquids diethyl ether, monomethylamine, and monoethylamine are also reported.
Optical Absorption of Cobalt in Manganese Fluoride
Authors: Blunt R. F.
Published: January 2005

The polarized crystal spectra of cobalt-doped MnF2 have been measured down to near 4.2°K. Three broad, anisotropic bands near 7200, 14 000, and 20 000 cm−1 are seen that are presumably due to the spin-allowed 4T1g(F)→4T2g(F), 4A2g(F), and 4T1g(P) transitions of substitutional Co2+, 3d7 ions. The D2h symmetry provided by the rutile structure of the MnF2 lattice produced marked orthorhombic splitting of about 3000 cm−1 in the 4T1g(P) band. Several weak spin-forbidden bands are also seen. The observed anisotropy indicates that the 4T2g(F) band is largely magnetic dipole while the other two are electric dipole. These latter parity-forbidden transitions are aided by coupling with odd lattice vibrations. Application of the appropriate selection rules allows tentative identification of several of the states involved.
Isotope Effects on Franck—Condon Factors. VI. Pressure-Broadened Absorption Intensities of the Schumann—Runge Bands of 16O2 and 18O2
Authors: Halmann M.
Published: January 2005

Integrated absorption intensities of the Schumann—Runge bands of gaseous 16O2 and 18O2 were measured, using pressure broadening by argon. For the (2, 0) to (6, 0) bands, the observed isotope effect on band intensities is equal to the calculated isotope effect on Franck—Condon factors. For the (7, 0) to (10, 0) bands, deviations of the observed isotope effect from that computed may be due to failure of the Morse potential function used in the computations, or to experimental difficulties caused by overlapping of bands.
Molecular Structures of Gaseous Hexachloro- and 1,2,4,5-Tetrachlorobenzene as Determined by Electron Diffraction
Authors: Strand T. G. , Cox H. L.
Published: January 2005

The molecular structures of hexachloro- and 1,2,4,5-tetrachlorobenzene have been determined by least-squares refinements based on gaseous electron-diffraction intensity data. The equilibrium configuration of hexachlorobenzene is found to be planar with D6h symmetry. The observed shrinkage for this molecule is compared with the shrinkage calculated from spectroscopic data for hexafluorobenzene. 1,2,4,5-Tetrachlorobenzene is planar with D2h symmetry; the repulsion between the neighboring chlorine atoms leads to an angle of 62.8°±0.4° between the ortho carbon—chlorine bonds. The most important molecular parameters and estimated standard deviations are listed.

Hartley's modification to the least-squares method was applied in refinements of the structure of 1,2,4,5-tetrachlorobenzene. It was found that the least-squares method modified in this fashion has a wider circle of convergence than the regular Gauss—Newton method, and that the regular method diverged even when the final parameters from the modified method were applied as a starting vector for the regular method.
Mössbauer Line Broadening in Trivalent Iron Compounds
Authors: Wignall J. W. G.
Published: January 2005

Line-broadening effects in Mössbauer spectra have been studied for a series of paramagnetic trivalent iron compounds. In general, the broadenings observed are temperature independent and are approximately correlated with the average spacing between neighboring iron atoms. The line broadening in these compounds is therefore attributed to magnetic hyperfine interactions which are partially narrowed by electron spin—spin relaxation. This interpretation is supported by the further observation that one of these compounds, ferric acetylacetonate, exhibits resolved magnetic hyperfine structure when it is diluted in a glassy matrix.
On the Interpretation of Ring Strain
Authors: Nelander Bengt , Sunner Stig
Published: January 2005

The effect of pressure—volume energy, nuclear motions, and reference system on estimated strain energies of mono and polycyclic ring compounds is discussed. Strain energies calculated by common procedures are shown to contain contributions not usually taken into consideration in discussions on ring strain. The dependence of strain-energy values on the choice of reference system is exemplified.
Ab Initio Calculation of Harmonic Force Constants
Authors: Bishop David M. , Randic̆ Milan
Published: January 2005

A method is presented which allows one to obtain analytically the harmonic force constants of a molecule solely from the single-center wavefunctions for the molecule in its equilibrium nuclear configuration. The dependence of the nonlinear parameters of the wavefunction upon the nuclear coordinates is explicitly included. The method is applied to a simple single-determinantal wavefunction for water and an analysis of the terms contributing to the force constants is made. The extension of the method to more complex single-center wavefunctions is also discussed. Methods for obtaining the derivatives of the various one- and two-electron integrals which are required in this treatment are given in the Appendix.
Force Fields for Group IV Tetrafluorides and Group V Trifluorides
Authors: Levin Ira W. , Abramowitz Stanley
Published: January 2005

The Coriolis zeta constants of the degenerate modes of SiF4, GeF4, NF3, PF3, and AsF3 were obtained from infrared-band contour measurements. These Coriolis coupling data provided the necessary constraints for determining unique force fields for the F2 and E symmetry species of the XF4 and XF3 molecules, respectively. In an attempt to limit the force field for the A1 species of the XF3 molecules, the rotational distortion constants, which are functions of both the A1 and E species force constants, were calculated for a range of values of the F12 interaction force constant. For the purpose of this calculation, the E species force constants that were determined from Coriolis coupling data were held fixed. For NF3, a satisfactory value of F12 was obtained using the rotational distortion data. However, the rotational distortion data were not useful in fixing the A1 species force fields for PF3 and AsF3.
Rodlike Behavior of Poly(n-butyl)isocyanate from Dielectric Measurements
Authors: Yu Hyuk , Bur Anthony J. , Fetters Lewis J.
Published: January 2005

Dielectric measurements have been made on dilute benzene solutions of poly(n-butyl)isocyanate (  O  = –C–N–       –      R)n,where R = n-C4H9, at 22.5°C over a frequency range 10−1 to 2×106 Hz. Measurements of relaxation time τ on six samples which have molecular weights in the range 1.4×105 to 2.3×106 showed that τ depends on molecular weight to the 2.7 power. In addition, only one dispersion region was observed for each sample and the corresponding dielectric increments were very large. We conclude from these observations that (1) the poly(n-butyl)isocyanate molecule is a rigid rod whose relaxation time in dilute solution is associated with the end-over-end rotation of the entire rodlike molecule around its minor axis, and (2) the net dipole moments of the molecule have a direction parallel to the major axis of the molecule. Calculation of the length of the molecule from relaxation data indicates that the conformation of the polymeric chain appears to be nonplanar and possibly helical. The dipole moments calculated from the static dielectric constant were not directly proportional to the molecular weight as expected. To explain this a model of the polymerization growth step, in which dipole reversal takes place, was proposed. In this model chain element dipolar senses are not uniform throughout the chain but undergo reversal after a finite sequence length which is independent of the over-all length.
Low-Temperature Transport Properties of Gaseous H2, D2, and HD
Authors: Diller Dwain E. , Mason E. A.
Published: January 2005

A complete quantal phase-shift calculation of the transport properties of gaseous H2, D2, HD, and some of their mixtures is presented from 10° to 300°K, based on the Lennard-Jones (12–6) potential. It is found that H2 and D2 have slightly different intermolecular potentials, in agreement with evidence from other sources. Agreement between calculation and experiment is generally good, but there are some small but clear indications that the (12–6) potential model is oversimplified, such as the necessity to use slightly different potantial parameters for the transport properties than for the second virial coefficients.
Debye Relaxation in Symmetric-Top—Foreign-Gas Mixtures; Temperature Dependence of Collision Cross Sections
Authors: Frenkel L. , Kryder S. J. , Maryott A. A.
Published: January 2005

The Debye relaxation spectra of three symmetric-top gases, CH3Cl, CHF3, and SO2F2, in the pure state and in dilute mixtures with the foreign gases, He, H2, D2, Ar, N2, CH4, CO2, and C3F8, were obtained over the temperature range −20° to 145°C at a frequency of 1220 MHz. Relaxation-rate parameters and the corresponding collision cross sections are derived. The cross sections vary with the absolute temperature as T−m, where the value of m ranges from 0.3 to 0.9 for the different systems. The cross sections are considered from a classical kinetic veiwpoint and an empirical relation is obtained which accurately relates the dielectric cross section to the effective viscosity cross section (or the corresponding Lennard-Jones parameters), the internal-to-orbital-angular-momentum ratio, and one additional parameter related in some way to the shape (prolateness or oblateness) of the top. Deviations in the shape of these spectra from the simple Debye form, which are attributable to a distribution of relaxation rates, are examined in some detail and correlated with the effective collision number.
On a Derivation of a Quantum-Mechanical Linearized Boltzmann Equation
Authors: Hoffman David K.
Published: January 2005

Methods recently developed to derive the classical Boltzmann equation are extended to quantum mechanics.
Magnetic-Rotation Spectra of the 2–0 Vibration—Rotation Band of NO
Authors: Aubel J. L. , Hause C. D.
Published: January 2005

Magnetic-rotation spectra of the 2–0 bands of 14N16O and 15N16O in the 2.7-μ region were obtained and analyzed. A qualitative explanation of the observed spectra is given. Beginning with the predicted Zeeman patterns, a classical approach is used which takes into account the circular dichroism in the region of strong absorption as well as the Faraday rotation and the effects of finite resolution. These qualitative arguments are used to explain the major intensity irregularities which appear in these spectra.
Low-Lying Pi—Sigma Transition in the Spectrum of Norbornadiene
Authors: Robin M. B. , Kuebler N. A.
Published: January 2005

A vibrational analysis of the first electronic band of norbornadiene (NBD), with origin at 45 120 cm−1, shows that the band is electronically allowed, the accompanying vibrations being totally symmetric. This is contrary to earlier theoretical work which assigned the band as N→V1, forbidden. A comparison with the spectra of cyclopentene and norbornene (NBE) suggests that the first band of norbornadiene is to be associated with the weak band of uncertain assignment found at approximately 45 000–50 000 cm−1 in all olefinic substances.

Gross changes in the vibrational spacing and shape of the vibronic envelope are observed on freezing the NBD and NBE molecules in low-temperature matrices. The spectral changes appear to be due to modifications of the upper-state potential surfaces as a consequence of the rigidity of the matrix.

There is some evidence in the NBD spectrum for weak vibronic coupling between the two halves of the diene molecule, and it is shown how the observed splitting pattern might be explained on such an assumption.
Transverse Relaxation in Systems of Two Nonidentical Spins
Authors: MacLean C. , Mackor E. L.
Published: January 2005

Nuclear relaxation in molecules with two nonidentical spins may originate from intra- and intermolecular interactions between like and unlike spins. The various contributions to the relaxation may be determined from the longitudinal relaxation combined with the Overhauser effect.

Transverse relaxation rates are likewise related to the contributions of the possible interactions. We have derived the appropriate equations for transverse relaxation in systems consisting of scalar-coupled nuclear spins. The expressions have been applied to CHFCl2, both neat and diluted in COS.

The results on the neat liquid are in agreement with those obtained previously from longitudinal relaxation: at −142°C hydrogen and fluorine relax mainly by interactions between unlike spins. Dilution in COS barely affects the ratio of intra- to intermolecular interactions under conditions where the relaxation is of dipolar nature. This surprising finding must be related to nonviscous rotational behaviour of molecules in liquids of low viscosity like COS. The moment of inertia of the molecule rather than the viscosity of the liquid determines rotational relaxation.
Heat Capacity and Other Thermodynamic Properties of MoF6 between 4° and 350°K
Authors: Osborne Darrell W. , Schreiner Felix , Malm John G. , Selig Henry , Rochester Leon
Published: January 2005

Thermodynamic properties of MoF6 have been measured between 4° and 350°K in order to obtain a third-law value of the entropy for comparison with the entropy calculated from molecular data. The enthalpy change for the solid—solid transition at 263.48°±0.02°K is 1953.3±2.0 cal mole−1, and the enthalpy of fusion at the triple point, 290.73°±0.02°K, is 1034.2±1.0 cal mole−1. The vapor pressure between 291° and 320°K is represented by the equation log10 Pmm=−2047.15/T−4.28004 log10T+20.19354. At 298.15°K the enthalpy of vaporization calculated from the vapor-pressure equation and the measured second virial coefficient, −923 cm3 mole−1, is 6630 cal mole−1. The standard entropy of the gas at 298.15°K obtained from the thermal data is 83.75±0.10 cal deg−1·mole−1. This agrees with the value of 83.77 cal deg−1·mole−1 calculated from Nazarian's electron-diffraction measurement of the Mo–F distance (1.840 Å) and from Weinstock and Goodman's vibrational assignment. Thermodynamic functions are tabulated at selected temperatures. At 298.15°K the values of CP°, S°, (H° − H0°)/T, and (G° − H0°)/T are 40.58±0.04, 62.06±0.06, 34.23±0.03, and −27.83±0.03 cal deg−1·mole−1, respectively, for liquid MoF6 and 28.82, 83.77, 19.25, and −64.51 cal deg−1·mole−1, respectively, for gaseous MoF6.
Structure of Sodium Aluminosilicate Melts Containing at Least 50 mole % SiO2 at 1500°C
Authors: Riebling E. F.
Published: January 2005

Viscosity and density data were obtained for several series of alkali aluminosilicate melts between 1200° and 1700°C with a counterbalanced sphere viscometer. Property comparisons are presented as functions of the SiO2 content, Na2O content, and constant Al/Na ratios at 1500° and 1700°C.

The viscosity and expansion information support the formation of three-dimensional cristobalitelike liquids on the Al/Na=1.0 line with some of the aluminum (III) in the form of AlO6 octahedra for Al/Na>1.0 melts.

The molar volume models that coincide with experiment for Al/Na≤1.0 melts involve AlO4 tetrahedra and v̄Na2O values that increase with increase of the Al2O3 content. The model that best agrees with experiment for melts with Al/Na>1.0 involves only some of the excess aluminum ions in octahedral coordination as well as a changing v̄Na2O. Melt molar volume dependencies on composition can resemble those observed for similar glasses, which suggests structural similarities. The present liquid structure picture differs somewhat from previous concepts of alumina-rich glass structures in this ternary system.
Vaporization Behavior of Europium Dicarbide
Authors: Gebelt Robert E. , Eick Harry A.
Published: January 2005

The temperature dependence of the vapor pressure of europium in equilibrium with solid europium dicarbide (EuC1.87±0.07) and graphite has been measured over the temperature range 1130° to 1600°K by both time-of-flight mass spectrometric and target collection techniques. From the vapor-pressure equation, the enthalpy of disproportionation of europium dicarbide is calculated to be 51.06±1.25 kcal/gfw by a second-law treatment of the data, and 51.24±2.0 kcal/gfw by the third-law method. The entropy of dissociation is calculated to be 18.43±1.70 eu/gfw. Combination of these data with the reported enthalpy and entropy of vaporization of elemental europium gives −9.17±1.15 kcal/gfw as the standard heat of formation and −7.47±1.87 kcal/gfw as the standard free energy of formation of europium dicarbide.
ESR of the Perinaphthenyl Radical in a Liquid Crystal
Authors: Glarum Sivert H. , Marshall James H.
Published: January 2005

The electron spin resonance spectrum of the perinaphthenyl radical has been studied in the isotropic and nematic phases of p-azoxyanisole. The g tensor and hyperfine splitting tensors for the two proton couplings and three of the four carbon−13 couplings have been determined, and were found to agree in most cases with theoretical estimates. Ordering of the radical was also deduced as a function of temperature in the liquid-crystal range, and corresponded to the ordering of the solvent molecules.

A general expression for the effective spin Hamiltonian of a radical in a liquid crystal is derived. Zeeman anisotropy and dipolar electron—nuclear couplings are shown to result in g shifts and changes in the hyperfine splitting coefficients.
Adsorption of Carbon Monoxide on a Tungsten (110) Surface
Authors: May J. W. , Germer L. H.
Published: January 2005

A clean (110) tungsten surface can adsorb CO molecules in two different ways. Those striking bare surface have high sticking probability and are held firmly with possible rearrangement of the surface-metal atoms. Molecules striking an already covered surface have a somewhat lower sticking probability and are held more weakly. Temperatures producing rapid desorption of the two components are 450° and 1100°K. The maximum coverage in the first layer is not pressure dependent. In the second layer the maximum coverage is about 0.8 of the first-layer coverage at 10−7 torr but decreases slightly at lower CO pressures. The structure of the first layer, as found by LEED observations, is very disorganized unless the crystal is heated; but a well-ordered structure is produced by heating at 925°K and poorer order by heating at lower temperatures. The ordered surface mesh is C(9×5). The detailed structure has not been determined. The intensities of various diffraction beams from a clean surface change in very complicated ways when the primary beam energy is altered; the variation with energy is much simpler when CO is adsorbed on the surface. A suggested distortion of the clean surface that accounts for these facts is presented.
Transients of Volume-Controlled Current and of Recombination Radiation in Anthracene
Authors: Helfrich W. , Schneider W. G.
Published: January 2005

The transients of volume-controlled doubly injected currents and of the accompanying recombination radiation were measured on anthracene crystals. By this method, which allows the trap-free case to be approximated, the carrier recombination rate constant K was determined in a more reliable way than is possible with steady-state currents. The result, K=(1.05±0.5)×10−6 cm3 sec−1, agrees well with the theoretical value predicted by a model in which the rate is a function of carrier mobility. The recombination fluorescence was found to consist of two components differing by their rise times. The fast component, Ifast, is due to singlet excitons generated directly by carrier recombination. The slow component, Islow, is proof that carrier recombination produces also triplet excitons (which can recombine to give singlets producing fluorescence). The ratio Islow/Ifast=0.65±0.1 indicates that two recombining triplet excitons do not always produce a singlet exciton but may also form an excited triplet exciton. In addition, the light transient measurements permitted the determination of the total rate constant, γtotal, of triplet—triplet recombination in a novel way. The result is γtotal=(4–8)×10−12 cm3 sec−1.
Low-Energy Electron-Diffraction Study of Molybdenum (110) Surfaces
Authors: Haas T. W. , Jackson A. G.
Published: January 2005

A study of the clean and oxygen-covered molybdenum (110) surface has been carried out using low-energy electron-diffraction techniques. The clean surface is found to be the same as an ideal (110) plane in the bulk. Oxygen structures corresponding to ¼, ½, and ¾ monolayer have been found. These structures are very similar to those found for the tungsten (110) surface. Experiments on nitrogen and hydrogen adsorption are inconclusive due to interference from other residual gases (primarily carbon monoxide).
Energy of Interaction between Two Molecules
Authors: Musher Jeremy I. , Salem Lionel
Published: January 2005

An expression for the energy of interaction between two molecules has been obtained by solving the secular equation using a double-iteration procedure based on the exact wavefunctions of the isolated molecules. This expression exhibits the intermolecular interaction energy explicitly and its leading terms agree with those recently obtained by Murrell et al. and Salem within the limits specified by these authors.
NMR Subspectral Analysis Applied to Polyfluorobenzenes C6HnF6—n. I. 1,2,3,5-Tetrafluorobenzene
Authors: Lustig E. , Diehl P.
Published: January 2005

The nuclear magnetic resonance spectrum (1H and 19F) of 1,2,3,5-tetrafluorobenzene is described. All coupling constants are obtained by subspectral analysis applicable to an AA′XX′MR system. A perturbation treatment for the AA′XX′MY case is outlined and illustrated by the R(Y) part of the spectra of 1,2,3,5-tetrafluorobenzene and pentafluorobenzene. The chemical shifts and the magnitude of coupling constants agree with values obtained for similar molecules. Also the result that the sign of JHF ortho is opposite to that of JHF para is in accord with earlier findings. It is emphasized that HF and FF coupling constants follow a monotonic sequence from J ortho through J meta to J para.
Electron Spin Resonance of a γ-Irradiated Single Crystal of a Hydrogen Peroxide—Urea Addition Compound at 77°K
Authors: Ichikawa Takahisa , Iwasaki Machio , Kuwata Keiji
Published: January 2005

The γ-irradiated single crystal of an addition compound H2O2·CO(NH2)2 at 77°K exhibited ESR spectra which were attributed to an O2− ion radical and an HO2· free radical. The measurements were made at 9.21 and 22.4 kMc/sec for various orientations of the crystal in the magnetic field. For most orientations, the spectra of O2− and HO2· were singlet and doublet, respectively. An isotropic component of the doublet was approximately 11 G. The g values were found to be anisotropic with the principal values: g1=2.0886, g2=2.0084, and g3=2.0009 for O2−; while g1=2.0495, g2=2.0081, and g3=2.0018 for HO2·. There seems to be no report about O2− trapped in a molecular crystal so far, and the results were compared with O2− in ionic crystal.
Quantum-Mechanical Potential-Energy Curve for the Lowest 1Σu+ State of He2
Authors: Scott D. R. , Greenawalt E. M. , Browne J. C. , Matsen F. A.
Published: January 2005

The potential-energy curve of the lowest 1Σu+ state of He2 is computed in a valence bond scheme using a 17-term wavefunction of Slater orbitals. A maximum in the potential curve occurs at 5.22 a0 with a computed height of 0.153 eV. A rigorous upper bound of 0.364 eV is found for the potential maximum. The rationalized dissociation energy for the best wavefunction is 1.719 eV at Re=2.11 a0, and a rigorous lower bound on the dissociation energy is 1.508 eV.
Conformational Analysis of Macromolecules. II. The Rotational Isomeric States of the Normal Hydrocarbons
Authors: Scott Roy A. , Scheraga Harold A.
Published: January 2005

The conformational potential energy of the normal hydrocarbon molecules is considered to be a function of the dihedral angles of internal rotation about the carbon—carbon single bonds, the bond lengths and valence angles being held fixed. The energy equation contains terms of two kinds, a sum over torsional or internal-rotation terms, one for each carbon—carbon bond, which are attributed to exchange interactions of electrons in bonds adjacent to the bond about which internal rotation occurs, and a sum over all the pairwise nonbonded interactions between all of the atoms in the molecule. The torsional terms are dependent on the dihedral angles of internal rotation and on the choice of fixed valence angles, but each torsional term reduces to the form ½U0(1+cos3ωi) when all the fixed valence angles are selected to be tetrahedral. The nonbonded-interaction terms are represented by Lennard-Jones ``6–12'' potential functions, Uij=(dij/rij12) − (eij/rij6), the parameters eij being calculated from the Slater—Kirkwood equation. The energy equation contains three adjustable parameters: U0, the barrier to internal rotation about a carbon—carbon single bond when the fixed valence angles are all tetrahedral, dHH, and dCC, dCH being taken as the geometric mean of dHH and dCC. These three parameters were selected to obtain agreement between the calculated and experimental values for the barriers to rotating a methyl group in ethane and propane, the difference in energy between the trans and the two gauche forms of butane, and the location of the gauche minima in butane. These parameters were then used, along with the known bond lengths and valence angles, to calculate the locations and energies of the various rotational isomeric states (potential-energy minima) for pentane, hexane, and heptane. A method of energy minimization was used which allowed all the dihedral angles of internal rotation to vary independently. These calculations demonstrate that the traditional procedure of assuming that each bond in a hydrocarbon molecule or a polyethylene molecule can exist in three rotational isomeric states, therefore T (180°), G+ (60°), and G− (300°), is an oversimplification and that more minima occur than is predicted by the traditional procedure. The implications of these results for formulating future statistical-mechanical theories of the normal hydrocarbons and of polyethylene are discussed.
Electron Spin Resonance of Cu2+ Ion in CdWO4, ZnWO4, and MgWO4 Single Crystals
Authors: Šroubek Z. , Žd̆ánský K.
Published: January 2005

Paramagnetic resonance measurements have been carried out at 78° and at 4°K on Cu2+ ions diluted in single crystals of CdWO4, ZnWO4, and MgWO4. The g factors and the hyperfine interaction with the copper nucleus have been determined. From this experimental data the ground-state wavefunction of the Cu2+ ion has been constructed. It has also been possible to calculate the relevant l=2 terms of the low-symmetry crystal-field components. Then in the framework of a simple g-factor theory the g-factor anisotropy has been calculated and compared with the measured anisotropy. The role of the distortion of the covalent π bonds has also been examined. In the case of MgWO4 and ZnWO4 a distinct temperature-dependent g-factor shift and a temperature-dependent change of hyperfine interaction constants have been observed.
ESR and Phosphorescence Spectra of the Triplet States of Phenyl s-Triazines and Phenyl Benzenes
Authors: Brinen J. S. , Koren J. G. , Hodgson W. G.
Published: January 2005

ESR and optical measurements have been made on the lowest triplet state of a series of phenyl s-triazines and polyphenyl benzenes. The features of the phosphorescence spectra and the value of the zero-field splitting parameters of these azines and their hydrocarbon analogs leads to the assignment of the lowest triplet state of the phenyl triazines as (π, π*). The effect of nitrogen substitution is discussed.
Uranium Monosulfide. III. Thermochemistry, Partial Pressures, and Dissociation Energies of US and US2
Authors: Cater E. David , Rauh E. G. , Thorn R. J.
Published: January 2005

A mass-spectrometric study of the sublimation of uranium monosulfide has been performed over the temperature range 1825° to 2400°K. The data are combined with the previous measurements of absolute rate of effusion by means of a new method of calculation which effects an absolute pressure calibration of the spectrometer and allows a determination of the partial pressures of U, US, and US2 in the vapor, the enthalpies and entropies of sublimation to atoms and molecules, and the dissociation energies of US and US2. The partial pressures of U, US, and US2 at 2020°K are in the ratios 1/0.27/0.001. The data for the several sublimation processes are as follows:     Reaction                  logP (atm)ΔH2020∘ kcal/moleΔS2020∘ cal/mole·degUS(s)=US(g)logPUS=(7.606±0.091)−(31 030±190)/T142.0±0.934.8±0.4US(s)=U(g)+S(g)logPU=(7.323±0.081)−(29 600±170)/T270.9±0.1665.0±0.72US(s)=US2(g)+U(g)logPUS2=(6.36±0.26)−(33 430±580)/T288.4±3.762.6±1.2The quoted uncertainties are standard deviations. The dissociation energies for US and US2 and the estimated uncertainties are D0(US)=133.8±2.3 kcal/mole or 5.80±0.10 eV,D0(US2)=252±4 kcal/mole or 10.9±0.2 eV.
Finite Nuclear Mass and Relativistic Effects on the Rotational Constant of Molecular Hydrogen
Authors: Tipping R. , Herman R. M.
Published: January 2005

Corrections to the rotational constant of molecular hydrogen associated with finite nuclear mass and relativistic effects are calculated. They are significantly smaller in magnitude than are the corresponding corrections previously employed. After these refinements are made, the values 60.8566±0.004, 45.6548±0.003, and 30.4527±0.002 cm−1 are obtained for the Dunham Be values of H2, HD, and D2. The present theoretical results show reasonably good agreement with Stoicheff's measurements on H2, HD, and D2, and with recent measurements on H2 by Fink, Wiggins, and Rank, while showing less good agreement with the measurements of Herzberg and Howe. The present agreement represents decided improvement over the results of previous analysis.
Spectroscopic Evidence for Rotation—Translation Coupling in the Liquid State: Infrared Absorption of HD in Liquid Argon
Authors: Holleman Gerald W. , Ewing George E.
Published: January 2005

The fundamental vibrational spectrum of HD in liquid argon has been studied. Features were observed which correspond approximately to vibration—rotation transitions of an isolated gas-phase molecule, indicating that HD rotates in this system. Other features in the spectrum have been assigned to vibration—translation combination bands, providing evidence for the existence of quantized translational energy levels for HD in its solvent cavity. The spectrum is unusual in that the rotational selection rules are relaxed and transitions corresponding to ΔJ=0, ±1, +2, +3, and +4 are present. Furthermore all the vibration—rotation absorption features are broad and their maxima are shifted from the gas-phase frequencies in an irregular pattern. Because of its asymmetrical mass distribution, rotational motion of HD is accompanied by a translation of the molecule in its solvent cavity. This rotation—translation interaction has been given quantitative form by a perturbation treatment by H. Friedmann and S. Kimel, and these results are consistent with the observed selection rules, frequency shifts, and linewidths in the spectrum of HD in liquid argon.
Comparison of Radical and Nonradical Processes in the Condensed-Phase Radiolysis of n-Hexadecane
Authors: Falconer W. E. , Salovey R.
Published: January 2005

The effects of state, temperature, and chemically reactive solutes on the radiolysis of n-hexadecane in condensed phases have been examined. All product yields are reduced by radical scavengers in liquid-state n-hexadecane, but only dotriacontane isomers are reduced in the solid. Iodine acts as a chemical scavenger and is more effective than 2-methylpentene−1. A hot-hydrogen-atom mechanism, together with molecular elimination, accounts for the formation of most of the hydrogen in the irradiation of n-hexadecane. Low-molecular-weight products are formed entirely by molecular reactions in the solid-state radiolysis and, about equally, via molecular and radical processes in the liquid. Intermediate-molecular-weight products in the liquid radiolysis are 80% from combinations of radicals from chain scission with various hexadecyl radicals. The remaining 20% in the liquid and the total intermediate yield in the solid are from nonradical processes. The combination of hexadecyl radicals yields at least 40% and 70% of the dotriacontane isomers in the radiolysis of pure n-hexadecane in the solid and liquid state, respectively. The remaining dimer may also be due to radicals which are formed in pairs, but ion—molecule reactions cannot be excluded. Temperature dependence of all products is small. Cage recombination of scission fragments and crosslinking of proximate radical pairs is enhanced in the solid state as compared with the liquid. Internal ···CH2–CH2··· rupture is equally probable at all positions, and seven times as likely as terminal CH3–CH2··· scission. Methyl C–H rupture is 40% as probable per bond as methylene C–H rupture.
Photoconductivity in Rigid Organic Solutions. II. Initial-Rate Studies of Charge-Carrier Production and the Two-Photon Requirement
Authors: Johnson G.E. , Albrecht A. C.
Published: January 2005

The initial rises of photocurrents in certain rigid organic solutions are examined both as a function of light intensity and wavelength. The quadratic nature of the intensity dependence is taken to signify a two-photon mechanism for charge-carrier production. The initial rate of charge-carrier production is linear in solute concentration and is not sensitive to O2 levels. Double-beam experiments allow the isolation of each of the two one-photon steps and the wavelength dependence of each step is studied. The first photon step shows specific vibronic activity for transfer into the intermediate state. The relative quantum yield rises sharply over the first absorption band of the solute molecule and then abruptly drops as the second absorption band is entered. The second step is relatively wavelength independent once its near-ultraviolet threshold is reached. A dark lifetime of 4.5 sec is observed for the intermediate state. The triplet state of the solute molecule cannot be implicated. Additional initial-rise studies reveal that of the two induced photocurrent signals one, the so-called ``365'' pseudostationary signal, arises from a state of the system which is one photon produced and one photon ionized; the other, referred to as the spike signal, arises from a state which is two photon produced and one photon ionized. The general problem of creating full charge separation in low-dielectric-constant media is briefly reviewed to show how the two-photon requirement is entirely to be expected. The results are treated within the framework of a straightforward kinetic scheme. Possible mechanisms, including a proton-transfer intermediate, are briefly but inconclusively examined.
Infrared Spectra of HCl in Pure and Impure Noble-Gas Matrices. Absolute Intensities
Authors: Verstegen J. M. P. J. , Goldring Hanna , Kimel S. , Katz B.
Published: January 2005

High-resolution spectra were taken of the 1–0 absorption band of HCl trapped in argon, krypton, and xenon matrices in the temperature range between 6° and 50°K. The influence of impurities on such spectra was studied by introducing small quantities of a different noble gas into the matrices.

A new spectral line, believed to be due to the combination of a ΔJ=0 transition with the constrained translational mode, is reported. Absolute intensities of the 1–0 band were measured and found to be 15 000, 18 500, and 18 000 darks in argon, krypton, and xenon, respectively. The spectra of HCl polymers are discussed.
New Method in the Kinetics of Classical Dense Fluids
Authors: Futrelle R. P.
Published: January 2005

A systematic method is presented for calculating the kinetics of a fluid for small time intervals in terms of the motion of a small number of particles. The method is based on a ``cluster expansion'' of the time evolution operator. The theory applies equally well at gas or liquid densities. As an example, the two-particle form of the theory is used to estimate the self-diffusion coefficient of the argon and hard-sphere liquids and the viscosity and thermal conductivity of the hard-sphere liquid. One new result is the exact calculation of the delta-function singularity of the time-dependent correlation functions describing ``collisional'' transport in the hard-sphere liquid.
Magnetic Susceptibilities of Solutions of Potassium in Molten Potassium Chloride
Authors: Bettman Max
Published: January 2005

Volume magnetic susceptibilities have been measured by the Gouy method for molten potassium chloride and for 7 and 15 mole % solutions of potassium metal in molten potassium chloride, between 800° and 1000°C. All these liquids are diamagnetic, but the potassium solute appreciably reduces the diamagnetism of the solvent. Making some assumptions about the densities (unmeasured) of the solutions and about the additivity of the ionic diamagnetism, it is possible to compute molar paramagnetic susceptibilities for the potassium valence electrons. These values can be very roughly accounted for by the equation for conduction-band electrons, with the effective electron mass approximately equal to the free electron mass. Alternatively, one can account for the data by localized electron models. One such model, based on a number of assumptions, is presented in the discussions. It leads to the conclusion that there exists a slight energy of association, of the order of kT or less, of potassium solute atoms into nearest-neighbor clusters.
Electronic Ground State and Wavefunctions for Vanadium Monoxide
Authors: Carlson K. Douglas , Moser Carl
Published: January 2005

Wavefunctions for VO have been calculated by the method of Roothaan to establish the electronic ground-state symmetry. The methods and basis functions used here are similar to those employed in previous studies of ScO and TiO. The present ab initio calculations show that the ground state of VO is 4Σ−, or possibly 2Σ− if configuration interaction is very important. These term types are associated with the configuration σδ2 and are not in conflict with present experimental evidence. The band systems of the molecule have not been adequately classified, but they are suggested to involve quartet and doublet terms. These theoretical ground-state assignments are contrary, however, to the expected 2Δr(σ2δ) term based on analogy with experimental results for NbO and TaO. It is not surprising, however, that a reversal in ground-state configurations occurs in this family, because a similar reversal is known for the monoxides of the titanium family and for the ground-state atoms of the vanadium family.
Systematics of the Evaporation Coefficient Al2O3, Ga2O3, In2O3
Authors: Burns Richard P.
Published: January 2005

The rate of evaporation from surfaces of Al2O3, Ga2O3, and In2O3 has been studied through a combination of thermal-imaging and mass-spectrometric techniques.

A discontinuity is observed in the rate of evaporation of Al2O3 and Ga2O3 at the melting point TM. The evaporation coefficient αv of the solid at the melting point is equal to 0.3±0.05 for all gaseous species over Al2O3, Ga2O3, and In2O3. The rate of evaporation from the surface of the liquid at the melting point is the equilibrium rate (αv=1) for all gaseous species. The evaporation coefficient αv over the solid is very nearly temperature independent for monatomic vapor species but depends strongly on temperature for polyatomic species.

It is shown that the data for the different systems can be directly correlated when they are plotted as logαv vs TM/T, where TM is the melting temperature. This correlation also applies to other systems and appears to be useful in predicting evaporation behavior in related systems.

The equilibrium rates of evaporation are used to calculate: D0°(AlO) = 116.0±3.0 kcal mole−1, D0°(Al2O) = 241.6±7.0 kcal mole−1, ΔH°v,298(Ga) = 64.2±2.0 kcal mole−1, D0°(GaO) = 90.2±3.5 kcal mole−1, D0°(Ga2O) = 206.8±7.0 kcal mole−1, D0°(In2O) = 179.2±4.0 kcal mole−1.
Polymorphism of LiMO2 Compounds and High-Pressure Single-Crystal Synthesis of LiBO2
Authors: Marezio M. , Remeika J. P.
Published: January 2005

Single crystals of γ-LiBO2, which is the phase stable at high (P, T), have been grown at 15 kbar and at 950°C by using a flux technique. The crystals were retained metastably by quenching to room pressure and temperature.

γ-LiBO2 is tetragonal with four molecules per unit cell (a=4.1961±0.0004, c=6.5112±0.0007 Å), Space Group I4̄2d. The arrangement is that of a zinc-blende-like structure, with every atom tetrahedrally coordinated. The structure has been refined from single-crystal x-ray-diffraction data with a precision corresponding to an R factor of 0.028. The interatomic distances are B–O=1.483 Å and Li–O=1.957 Å.

The polymorphism of the LiMO2 compounds (M=B, Al, Ga, In, Tl) is discussed. It is shown that there is a common trend among these compounds. They tend to assume a NaCl-like structure. LiAlO2 and LiGaO2 have such an arrangement at high (P, T), while LiInO2 and LiTlO2 have a NaCl-like structure at room pressure and temperature. The only exception is LiBO2.
Two-State Model for the Free Volume of Vitreous B2O3
Authors: Macedo P. B. , Capps W. , Litovitz T. A.
Published: January 2005

New data on the density of B2O3 from 25° to 230°C are given. A two-state equation of state for the volume is presented which fits the volume data from 350° to 1400°C. A specific structure for the two states is suggested and shown to be consistent with Raman data. Below 350°C and at high pressures the data indicated that the two-state expressions for free volume still hold but the volume of the close-packed structure becomes temperature and pressure dependent.

The viscosity of B2O3 from the glass transition up to 1400°C and at high pressure is consistent with the equation of state and the hybrid equation of Macedo and Litovitz. The viscosity values above 1400°C indicate a breakup of the two-state structures and the beginning of multistate behavior which results in a temperature-dependent activation energy. The onset of this effect causes the ``apparent'' activation energy to increase above 1400°C.
Paramagnetic Resonance Studies of Bonding in [CrCl5(H2O)]2—
Authors: Garrett Barry B. , DeArmond Keith , Gutowsky H. S.
Published: January 2005

Single-crystal, room-temperature electron spin resonance spectra are reported for the complex ion [CrCl5(H2O)]2— in the host lattice (NH4)2[InCl5(H2O)]. The spectra are analyzed by means of a rhombic spin Hamiltonian and the spin-Hamiltonian parameters are related to an LCAO-MO description of the ligand—Cr3+ bonding. The complexity of the d3 system and the lack of sufficient experimental parameters prevented the direct evaluation of molecular orbital mixing coefficients from the ESR and optical data as was accomplished previously for tetragonal d1 complexes. However, an independent estimate of the spin—orbit coupling is used to establish interrelationships among the four molecular orbital mixing coefficients of interest and serves as a basis for discussing the bonding in [CrCl5(H2O)]2—. Evidence is found for pi bonding to the H2O. Also, as in the case of the d1 complexes, charge-transfer states are found to contribute significantly to g and to the zero-field splitting parameter D. The sign of their contribution to D is controlled by the mixing coefficients and can be either positive or negative; the contribution of doublet states appears to be small.
Radial Distribution Function of Hard Spheres
Authors: Ree Francis H. , Keeler R. Norris , McCarthy Shaun L.
Published: January 2005

The third-order density correction term g3(r) in the density series for the radical distribution function g(r) is evaluated for a system of hard spheres over all distances. Both the Monte Carlo method (r<2σ, σ=sphere diameter) and the analytic method (r≥2σ) are used to calculate the graph integrals appearing in g3(r). In carrying out the Monte Carlo integrations, calculations are simplified if gn(r) is represented by a sum of modified doubly rooted graph integrals instead of the Mayer—Montroll doubly rooted graphs. The modified doubly rooted graphs contain both Mayer f functions and f̃ functions (f̃=f+1). Advantages of this representation are twofold; (a) reduction in the number of graph integrals appearing in gn(r), and (b) the strong dependence of the graph integrals both on distance and dimension for the hard-core potentials. The analytic expression of g2(r) is obtained for r≤σ, by calculating the first-order density correction term of the triplet distribution function.

The above results are compared with the corresponding expressions derived by using three approximate integral equations for g(r): the Percus—Yevick equation, the convolution-hypernetted-chain equation, and the Born—Green—Yvon equation.

The fifth virial coefficient B5 for hard spheres is calculated from the g3(r) data. Use of the virial theorem and the Ornstein—Zernike relation gives the following values of B5: B5/(B2)4 (virial)=0.1105±0.0004,B5/(B2)4 (Ornstein−Zernike)=0.1106±0.0011.

We also compare the truncated density series of g(r) with the molecular-dynamics data of Alder and Wainwright and the g(r) obtained from the Percus—Yevick, the convolution-hypernetted-chain, and the Born—Green—Yvon integral equations at one-half the close-packed density.
Ionization of Liquids by Radiation. II. Dependence of the Zero-Field Ion Yield on Temperature and Dielectric Constant
Authors: Hummel Andries , Allen A. O. , Watson Freddie H.
Published: January 2005

The positive- and negative-ion mobilities and the yield of separated ion pairs have been determined for irradiated hexane over the temperature range 200°—300°K, and for carbon tetrachloride and 1,4-dioxane at room temperature. The effect of radiation quality on the ion yield in hexane was also studied. The ion mobilities were changed in hexane by small amounts of added foreign substances. The temperature coefficient of mobility is greater than that of the solvent viscosity for both positive and negative ions in hexane. Our data do not allow any firm conclusion regarding the nature of the negative ion in pure hexane. The data on ion yields in hexane are discussed in terms of the theoretical energy-loss spectrum of the primary fast electron which is responsible for the ionization, and Onsager's expression for the escape probability on an ion pair formed near to each other in a fluid medium. The number of high-energy secondaries (above 1000 eV) is much too small to account for the observed yields of separated charge. It is concluded that electrons, generated by ionization with kinetic energies below 100 eV, travel much farther on the average from their parent ions than would be expected by extrapolation of electron ranges measured at higher energies.