bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal and Molecular Structure of C4B20H22, Bis (o-dodecacarborane)
Authors: Hall L. H. , Perloff A. , Mauer F. A. , Block S.
Published: January 2005

The molecular configuration of bis(o-dodecacarborane), C4B20H22, has been determined in a complete three-dimensional x-ray crystallographic study. It is demonstrated that the C2B10 unit in each half of the molecule corresponds to a slightly distorted icosahedron. The two halves of the molecule are joined by a carbon—carbon single bond (1.522 Å) and are related by a center of symmetry. The unit cell is monoclinic with a=7.014±0.001 Å, b=9.862±0.001 Å, c=12.360±0.002 Å, and β=90°31′±2′. Z=2 and the space group is P21/n. The R value for 1899 reflections is 6.8% and for the 1749 observed reflections it is 6.4%.
Overlap Interaction of Water Molecules
Authors: Kamb Barclay
Published: January 2005

The dense-phase ice VII has special features that enable its equilibrium lattice constant under pressure, internal energy relative to ice I, and compressibility to be calculated readily by means of the vibrational Mie—Grüneisen equation of state and the integral and derivative thereof. Experimental values or estimates for these quantities allow evaluation of the overlap energy between neighboring water molecules that are not hydrogen bonded to one another. The result is sensitive to the assumed strength of the van der Waals attraction, which cannot be evaluated independently, but in any case it conflicts with second-virial-coefficient interpretations in indicating a relatively greater overlap repulsion. Experimental evidence from ice VII (quenched) at atmospheric pressure, and from ice II, tends to support a van der Waals interaction at least 50% greater than given by a standard semiempirical version of the London formula. The results enable the stability of Ice VII at very high pressures (∼200 kbar) to be discussed.
Surface and Bulk States of Additives in Alumina Powder
Authors: Pastor R. C. , Kimura H. , Podoksik L. , Pearson M. A.
Published: January 2005

A significant fraction of the losses in the additive, in the crystal growth (conventional Verneuil process) of ruby, is traced to powder technology. Valence states of the additive in the powder are studied and correlated with their escaping tendencies. A working model is proposed and supported by kinetic studies on the powder. From this model is derived certain predictions which are significant to the Verneuil crystal growth of solid solutions.
Bis (3-phenyl-2,4-pentanedionato) Copper. I. Molecular and Crystal Structure
Authors: Carmichael J. W. , Steinrauf Larry K. , Belford R. Linn
Published: January 2005

The crystal structure of bis (3-phenyl-2,4-pentanedionato)copper(II) has been determined by the use of three-dimensional Fourier methods and accurate atomic coordinates obtained by three-dimensional least-squares refinements. The crystal belongs to the monoclinic space group P21/c with two molecules per unit cell. The cell parameters are a=10.250 Å; b=6.778 Å; c=13.763 Å; β=93.55°. The final reliability factor (R) is 0.0834. The acetyl carbon skeleton is seen to be tilted by 14° from the plane defined by the copper and oxygen atoms. The phenyl ring is bent slightly down from the acetyl carbon skeletonal plane, and is twisted through a torsional angle of 70° from the mean plane of the chelate ring.
Comparison of Two Methods for Calculating the Surface Tension of Alkali Halide Crystals
Authors: Yun K. S. , Benson G. C.
Published: January 2005

The difference between two methods of calculating the surface tension of alkali halide crystals, (i) from the surface stress and (ii) from the superficial derivative of the surface free energy, is examined. Emphasis is placed on the latter approach since Method (i) has recently been described in detail. The large discrepancies which previously existed between numerical values of the surface tension estimated from (i) and (ii) have been greatly reduced. In general the agreement between results obtained by the two approaches is quite close for undistorted crystals but the difference is increased when the effect of relaxation of the surface region is considered.
Temperature Dependence of Chlorine NQR Frequencies and Pi Bonding
Authors: Haas T. E. , Marram E. P.
Published: January 2005

A theory is presented for the anomalous temperature dependence of 35Cl NQR frequencies observed for certain transition-metal—chloride compounds. The basic feature of the theory is a break down of π bonding due to bending vibrations, and a consequent increase in the electron population in chlorine 2pπ orbitals, causing in turn an increase in the observed NQR frequency. An approximate separation of lattice-motion effects and intramolecular effects is made for the series of compounds K2MCl6, M = W, Re, Os, Ir, Pt, and it is shown that the predicted magnitude and behavior of the intramolecular effects agree well with the observed values.
Analysis of Nuclear Magnetic Resonance Spectra of Molecules in Liquid-Crystal Solvents
Authors: Snyder Lawrence C.
Published: January 2005

A convenient method to analyze the high-resolution nuclear magnetic resonance spectra of molecules dissolved in liquid-crystal solvents is described and related to basic theory of magnetic resonance. The method is applied to analyze the proton and fluorine NMR spectra of monofluorobenzene in a nematic liquid-crystal solvent. Parameters deduced from this analysis and describing the anisotropic molecular motion, the direct magnetic dipole—dipole interactions Dij, the indirect spin—spin couplings Jij, and the anisotropy of the diamagnetic shielding constant of F in the C–F bond are summarized and compared with the values for benzene and hexafluorobenzene in the same solvent. It is shown that agreement of experimental and computer-simulated theoretical spectra is probably limited by the accuracy of relative bond lengths in the assumed geometry for fluorobenzene. It is concluded that for many molecules having a large number (N≥3) of spin-½ nuclei, it is possible in the analysis of these spectra to reject incorrect hypothetical geometries and even to obtain refined relative positions for the magnetic nuclei.
Effect of a First-Order Phase Transition at High Pressure on Ligand-Field Spectra
Authors: Pagannone M. , Drickamer H. G.
Published: January 2005

The effect of pressure to 140 kbar has been measured on the 10Dq peak in [Ni(NH3)6]X2, where X is Cl−, Br−, or I−. At about 70 kbar there is a first-order phase transition which presumably rearranges the halide ions with respect to the Ni(NH3)6++ molecular ions. This rearrangement has a measurable effect on the ligand-field energy 10Dq. For the chloride there is a decrease of about 100 cm−1, for the bromide a decrease of about 30 cm−1, while for the iodide there is an increase of about 80 cm−1. Measurements on the A2g(F)→T1g(F) transition in the chloride and bromide indicate that B decreases with increasing pressure in the low-pressure phase, that there is little or no discontinuity in B at the transition, and that B is nearly independent of pressure in the high-pressure phase.
Ultrasonic Relaxation and the Barrier to Internal Rotation in 1,2-Dichloro- and 1,2-Dibromoethane
Authors: Piercy J. E.
Published: January 2005

The ultrasonic absorption of solutions of 1,2-dichloroethane in ether and acetone, and 1,2-dibromoethane in acetone, has been measured over the frequency range 24 to 55 Mc/sec at temperatures from −90° to +40°C. The measurements are consistent with the single relaxation process of internal rotation about the C–C bond with a barrier to the conversion from a gauche to a trans isomer of 3.2±0.5 kcal/mole for 1,2-dichloroethane and 4.2±0.6 kcal/mole for 1,2-dibromoethane. Together with spectroscopic torsional frequencies they indicate that the barrier has approximately a cosine form.
Theory of Chemical Exchange Effects in Magnetic Resonance
Authors: Gutowsky H. S. , Vold R. L. , Wells E. J.
Published: January 2005

The Anderson—Weiss formalism is used to develop a general theory for calculating the effects of chemical exchange and spin coupling on echo amplitudes in Carr—Purcell pulse sequences on spin systems in the liquid phase. The theory is shown to involve the matrix integral solution of the Hahn—Maxwell—McConnell equations, generalized to include spin coupling, and of Alexander's equations for the relevant density matrix elements, subject to the boundary conditions imposed by the pulses. Some specific systems are treated in detail, and closed formulas are given for the decay of the echo train in several situations, including the coupled and uncoupled AB systems, and the coupled ABX and ABXq systems.

We show that if the natural relaxation rates of nuclei in exchanging sites are identical, then in general effects of both exchange and spin coupling can be removed by pulsing sufficiently rapidly. Modulation of the echo train by spin coupling is removed by rapid exchange between the coupled sites. The Carr—Purcell experiment on an equivalent set of spins affords effective decoupling from another equivalent set unaffected by the pulses, in the absence of exchange between the sets. An analogy is drawn between chemical exchange and quadrupolar relaxation, and a method is outlined which in principle should provide an indirect determination of quadrupolar or other fast relaxation rates.

We illustrate the applicability of the theory to the calculation of line shapes in steady-state spectra by treating the exchanging coupled AB system in detail, and show that in the fast exchange limit the theory predicts weak broad resonances not previously described.
X-Ray Scattering by Triplet Excitons
Authors: Maréchal Yves , McConnell Harden M.
Published: January 2005

An experimental study of the temperature dependence of the intensities of x rays diffracted from ionic molecular crystals containing triplet excitons provides strong evidence for distortions associated with exciton—phonon interaction. The effects of thermally excited excitons, and thermally excited phonons, on diffracted x-ray intensities are distinguished by their different temperature dependences. The experimental accuracy of the observed diffracted intensities is not high enough to distinguish between ``localized'' or ``self-trapped'' excitons, and ``free'' or ``distributed'' excitons.
Inelastic Neutron Scattering from Pressurized Ethane
Authors: Straker E. A.
Published: January 2005

Motions of the ethane molecule have been investigated at room temperature by inelastic neutron scattering techniques. Ethane targets were observed both in the gas and liquid phases by means of pressure variation. The University of Michigan four-rotor mechanical monochromator was used to obtain data at scattering angles of 90 and 22 deg for neutron energies in the range 0.046 to 0.020 eV. Triple-axis-crystal spectrometer measurements were also made at 0.035 and 0.064 eV as verification. These data indicate that there is no significant difference in the scattering properties of ethane in the gas and liquid state. Effects of the torsional motion of the two methyl groups about the C–C bond can be seen in the forward-angle data. Comparison of experiment with theory indicates that a Krieger—Nelkin model which includes a harmonic-oscillator representation of the torsional motion approximately predicts the observed data. The influence of multiple scattering on the final energy distribution has been observed and is discussed.
Electron Spin Resonance of a Center in Fluorine-Doped Zinc Sulfide
Authors: Kasai Paul H.
Published: January 2005

Fluorine-doped cubic ZnS shows a photosensitive ESR center of spin ½. The signal exhibits three types of hyperfine structures; one ascribed to a fluorine nucleus, the second to four structurally equivalent Zn+ + ions, and the third to 12 structurally equivalent Zn+ + ions. The center is, therefore, assigned to an electron excess center due to F− ion incorporated substitutionally at sulfur sites. It sets forth a direct experimental evidence that in ZnS phosphors a substitutionally incorporated halide ion could trap an electron released by photoexcitation.
Status of Linear Relations Among Heats of Transport
Authors: Howard R. E. , Lidiard A. B.
Published: January 2005

It is shown that in situations where the fluxes of the various components of a system are not linearly independent, previously derived linear relations among the heats of transport contain no physical information, but serve only to complete the definition of these quantities. Other defining equations are possible but physical predictions are unaffected by the choice so presented. This resolves the paradox of the apparent inconsistency of these linear relations with kinetic theories of heats of transport.
Thermal Conductivity of Moderately Dense Gases
Authors: Kim S. K. , Flynn G. P. , Ross J.
Published: January 2005

A theory previously proposed for the viscosity of moderately dense gases is applied to a calculation of the coefficient bλ in the virial expansion in density of the thermal conductivity, λ=λ0+bλρ+···. The contribution of three-body collisions to bλ is approximated by two-body collisions between a monomer and a dimer, the latter being defined to include bound, metastable, and orbiting pairs. Collisional transfer in binary collisions is not taken into account. The calculation yields the temperature dependence of bλ as proportional to T−1 at high T but nearly invariant with T at moderate reduced temperatures; both trends are essentially consistent with experiment. Comparisons are made with several other theories.
Measurement of g Values in the Electron Spin Resonance Spectra of Free Radicals
Authors: Segal Bernice G. , Kaplan Michael , Fraenkel George K.
Published: January 2005

Measurements have been made of the g values in the electron spin resonance spectra of 20 aromatic free radicals with an accuracy which has not previously been attainable. The largest source of error for both absolute and relative measurements resulted from variations in the difference between the magnetic field at the ESR sample and at the proton NMR probe, located just outside the center of the microwave cavity, which was used to measure the field. Except for the p-benzosemiquinone radical, g values were not found to depend on temperature over the range from room temperature to −100°C. The dependence of the g value on solvent and counterion was also investigated to some extent, and the g value of the perinaphthenyl radical was found to vary markedly with solvent. Agreement with Stone's theory of the g values of aromatic radicals is excellent, except for those radicals in which molecular distortions are expected according to the Jahn—Teller theorem and for radicals in which the unpaired electron is in a nonbonding molecular orbital.
Force Fields for the Boron Trihalides
Authors: Levin Ira W. , Abramowitz Stanley
Published: January 2005

The method of Edgell and Moynihan for determining Coriolis zeta constants from the infrared band contours of degenerate vibrational modes was verified for selected molecules and was then applied toward computing the zeta values of the E symmetry vibrations of the boron-trihalide molecules. Since it is not feasible to define unique potential functions for the BX3 species from only frequency data, general force fields were determined for the series by combining both the Coriolis zeta constants and the observed isotopic frequency data in a least-squares refinement scheme. The final force fields indicate that the sensitive stretch—bend interaction constant is a significantly large negative quantity that decreases as the series progresses from BF3 to BI3.
Deuteron Magnetic Resonance of Ferroelectric Potassium Ferrocyanide Trihydrate
Authors: Tsang Tung , O'Reilly D. E.
Published: January 2005

The quadrupolar splittings and linewidths of the deuteron magnetic resonance of single crystals of ferroelectric K4Fe(CN)6·3D2O(KFCT) have been measured from −100° to 58°C. At low temperatures eight pairs of resonance lines are observed corresponding to four types of water molecules A, B, C, D, and their ac plane enantiomorphs A+, B+, C+, D+. The molecules are undergoing a fast 180° flip motion about the bisectrix of the DOD bond angle. At temperatures above the Curie temperature (−20°C) only two pairs of lines are observed which are shown to result from fast molecular reorientations within the sets A, C, A+, C+ and B, D, B+, D+. Molecular orientations are determined at low temperatures from rotation patterns and these become shifted for the C- and D-type molecules in the transition to the paraelectric phase.

A structure for ferroelectric KFCT is proposed based on the deuteron resonance data. Activation energies and frequency factors for the 180° flip, AC, and AA+ averaging motions are derived and discussed. The temperature dependence of proton resonance second-moment data and the single-crystal spectra at 25°C are interpreted in terms of the motions deduced from the deuteron resonance experiments and compared with the results of inelastic neuteron scattering experiments.
Cluster Theory of Polyelectrolyte Solutions. I. Activity Coefficients of the Mobile Ions
Authors: Manning Gerald S. , Zimm B. H.
Published: January 2005

In an effort to calculate thermodynamic properties of polyelectrolyte solutions with as few assumptions as possible, we have utilized the Mayer cluster theory of ionic solutions as our starting point rather than the Poisson—Boltzmann equation. We show that the use of the Debye—Hückel screened Coulomb potential between charged sites on the polyion is an adequate first approximation for the mean activity coefficient of mobile ions, although single-ion activity coefficients require additional terms for their description. Satisfactory agreement with experiment is obtained.
Determination of Electron-Capture Cross Sections with Swarm-Beam Techniques
Authors: Christophorou L. G. , Compton R. N. , Hurst G. S. , Reinhardt P. W.
Published: January 2005

A method is described which combines electron-swarm and electron-beam techniques to obtain absolute electron-capture cross sections as a function of electron energy. As examples of the method, data on Cl− from ortho-chlorotoluene (approximately 1 eV) and O− from oxygen (approximately 7 eV) are presented and discussed.
Far-Infrared Spectra of Gas Molecules Trapped in β-Quinol Clathrates
Authors: Burgiel J. C. , Meyer Horst , Richards P. L.
Published: January 2005

We have studied the far-infrared spectra of 12 different gases trapped in the cages of β-quinol clathrates. The data are most extensive for Ar, Kr, Xe, CO, N2, NO, and O2 in the frequency range from 15 to 85 cm−1. In these cases, monatomic and nonpolar diatomic gas molecules show a single absorption line, which we have assigned to translational motion of the molecule within its cage. Polar diatomic molecules show an additional line, which we have assigned to hindered rotation. These lines are an order of magnitude less intense than ordinary electric dipole transitions. The absorptions due to translational motion arise through dipole moments induced by interaction between the gas molecule and the clathrate cage. The frequencies and shapes of the infrared absorptions as a function of temperature from 1.2° to 170°K, as well as the frequencies of hindered rotation for N2 and O2 deduced from other experiments, were used to evaluate the parameters of potential-well models for these seven gases. The specific heats associated with the enclosed molecules were computed and found to be in excellent agreement with measured specific heats. Spectra of H2, CH4, CH3F, CHF3, and NF3 clathrates and of α-quinol are also discussed.
Ligand-Field Treatment of the Jahn—Teller Distortion in VCl4
Authors: Ballhausen C. J. , De Heer J.
Published: January 2005

A ligand-field treatment of the Jahn—Teller distortion in VCl4 is developed using perturbation methods. Several of the results are at variance with those obtained earlier by means of the electrostatic crystal field model, and are in substantial agreement with some recent molecular orbital calculations. It is found that distortions are of the same order of magnitude as the relevant zero-point vibrational energies so that no ``static'' effect can be expected. This is in accordance with the available experimental evidence. Our results suggest certain splittings in the infrared and Raman spectrum of VCl4. On the basis of the present experimental evidence the consequences of such a ``dynamic'' Jahn—Teller effect can neither be confirmed nor contradicted with certainty.
Polarization of CaF2:Sm3+ Fluorescence
Authors: Ewanizky T. F. , Caplan P. J. , Pastore J. R.
Published: January 2005

The particular environments which produce two different types of CaF2:Sm3+ fluorescence were deduced from study of the polarization of each spectrum. Either trigonal or tetragonal symmetry was observed and attributed to the local charge compensator associated with each spectral type. Depolarization mechanisms and the effects of secondary impurities on the activator ions are discussed.
On the Limiting Shape of the Distribution Function of Lengths of a Single Polymer Molecule with Excluded-Volume Effects
Authors: Mazur Jacob
Published: January 2005

The distribution of the lengths of the polymer molecule is estimated from the computed reduced moments with the excluded-volume effect being taken into consideration. It is found that the probability distribution function for chain ends can be fitted reasonably well by an exponentially decaying function, raised to the power of t, where t, the shape factor, exceeds its Gaussian value of 2. As a result of the excluded-volume effect, the distribution of the lengths of a single polymeric molecule results in the chain assuming a more uniform conformation, as compared with the Gaussian coil model.
Interaction Potentials of Simple Nonpolar Molecules with Boron Nitride
Authors: Crowell A. D. , Chang Chai Ok
Published: January 2005

The interaction energies of Ne, Ar, Kr, Xe, N2, and CH4 near a semi-infinite hexagonal boron nitride lattice at the potential minimum have been calculated using lattice sums of a (6–12) potential. Potential constants were obtained from empirical values corresponding to like-molecule interactions and by the use of combination rules. Literature values for the gas-molecule parameters were used, and the necessary constants for boron nitride were found from its solid-state physical properties. Comparisons are made with other calculations and with experimental results.
Theoretical Calculation of the Ortho—Para Hydrogen Transition Rate on a Paramagnetic Solid Surface
Authors: Leffler Amos J.
Published: January 2005

The theoretically expected conversion rate of the ortho—para hydrogen molecular transition on a solid surface was calculated on the basis of the difference of proton-spin flip rates caused by a paramagnetic ion in the surface. It is concluded that the electron-spin relaxation time of the paramagnetic ion greatly affects the conversion rate, with the ions having long relaxation times being better catalysts. The calculated conversion rates were found to be much greater than those experimentally observable and the causes for the discrepancy are discussed.
Dispersion of the Faraday Effect in CoCl4=
Authors: Stephens P. J.
Published: January 2005

The Faraday effect of the 15 000-cm−1 transition of CoCl4= is calculated using both crystal-field theory and a simple molecular orbital theory and is shown to provide a means of discriminating between the two models. The recent calculation of Lin and Eyring is criticized.
Mass-Spectrometric Study of the Yttrium—Carbon System
Authors: De Maria G. , Guido M. , Malaspina L. , Pesce B.
Published: January 2005

A high-temperature investigation of the vapor in thermodynamic equilibrium with Y–C condensed system was carried out in the temperature range 2075°—2340°K. Y and YC2 are shown to be important species in the vapor phase. Utilizing the pressure-independent reaction Y(g)+2C(s)→YC2(g), second- and third-law methods yielded D00=155±6 kcal mole−1 and D00=156±5 kcal mole−1, respectively, for the Y–C2 bond energy. An estimated heat of formation ΔH°f298=−27±6 kcal mole−1 for solid dicarbide is also obtained.

Comparison between Me—C2 and Me—O bond strengths is made for Group IIIA elements and for the first two elements of the lanthanide series.
Theoretical Investigation of H3O+
Authors: Bishop David M.
Published: January 2005

A single-center molecular wavefunction for H3O+ consisting of nine terms is obtained. Each term is a symmetry-adapted combination of Slater determinants and each determinant is composed of Slater-type orbitals having noninteger principal quantum numbers. Up to and including f orbitals are considered and in the final wavefunction there are nine linear and 24 nonlinear parameters in all; these are determined variationally. The molecule is predicted to be a rather flat pyramid (H–O–H angle: 114°26′) having a bond distance of 0.95 Å; this is in accord with experimental observation.
High-Frequency Elastic Moduli of Simple Fluids
Authors: Zwanzig Robert , Mountain Raymond D.
Published: January 2005

This article presents a calculation of the infinite-frequency elastic moduli of monatomic fluids. When the intermolecular potential has the standard Lennard-Jones form, the elastic moduli are shown to be related to the pressure and internal energy of the fluid. Numerical values of the elastic moduli at various densities and temperatures are presented in tabular and graphical form. An identity is derived relating the shear and bulk moduli of any isotropic material in which particles interact by means of two-body central forces; this is a generalization of the familiar Cauchy identity occurring in the theory of elasticity of solids. The approach is based on analysis of the high-frequency limit of exact time-correlation function expressions for shear and bulk viscosity.
Use of Relativistic Wavefunctions in Crystal-Field Theory
Authors: Wybourne B. G.
Published: January 2005

The purpose of this paper is to indicate some of the consequences of using relativistic wavefunctions in crystal-field calculations. Substitutional expressions are developed which permit the calculation of relativistic crystal-field matrix elements using LS basis states following the method of Sandars. In these expressions the angular parts of the matrix elements are evaluated using LS basis states while the radial part uses the radial integrals computed from relativistic Hartree—Fock-type wavefunctions. It is demonstrated that the crystal-field matrix elements are no longer diagonal in the spin quantum number S when relativistic wavefunctions are used. Recognition of this point leads to an important, and hitherto unnoticed, second-order contribution to the ground-state splitting of S-state ions.
Vibrational Relaxation of HI, 1400°—2300°K
Authors: Chow C. C. , Greene E. F.
Published: January 2005

The vibrational relaxation of HI in a mixture of 10% HI in Ar has been studied by following the populations of the four lowest vibrational states as they approach their equilibrium values after the abrupt heating produced by a shock wave. The states v=1, 2, and 3 all relax approximately exponentially with the same rate constant, kv≅1.0×10−13 cc molecule−1·sec−1 at 2000°K. As the temperature increases from 1400° to 2300°K, k1 approximately triples. This temperature dependence is very much smaller (a factor of ∼10−2) and the rate is very much faster (a factor of 102 to 103 at 2000°K if the relaxation is due to HI—Ar collisions) than the values predicted on the basis of the Schwartz—Slawsky—Herzfeld theory or the empirical correlation of Millikan and White.
EPR Study of the Biphotonic Nature of the Solute-Sensitized Photodecomposition of Polydimethylsiloxane
Authors: Siegel Seymour , Judeikis Henry
Published: January 2005

The photolysis of solutions of naphthalene in polymeric dimethylsiloxane (PDMS) has been examined by EPR (electron paramagnetic resonance) spectroscopy at 77°K. It was found that the naphthalene solute sensitizes the decomposition of the solvent by a stepwise two-photon absorption process involving the first triplet state of naphthalene as an intermediate. The absorption of the second photon within the naphthalene triplet manifold of states is followed by an energy transfer process to the polymer which then decomposes. Decomposition occurs via Si–C and C–H bond rupture. The stabilities of the resultant radicals, ≡Si·, CH3·, —CH2·, and H·, which are identified by means of their EPR spectra (except for H· which is not observed at 77°K) are also discussed. The latter species presumably reacts immediately, possibly by a hotatom reaction, with a polymer molecule to form H2 and —CH2·. It is shown that the CH3· radical is also unstable at 77°K and decays by a hydrogen abstraction reaction to form CH4 and the —CH2· radical with a half-life of approximately 80 min.
Heteronuclear Spin—Lattice Relaxation in Some Crystalline Aromatic Compounds
Authors: Anderson J. E. , Slichter W. P.
Published: January 2005

Nuclear spin—lattice relaxation has been studied in some crystalline aromatic compounds, the toluene derivative C6H5CF3, and the xylene derivates m- and p-CF3C6H4CF3, over the temperature interval between −185°C and the respective melting points. The decay of both the 1H and 19F nuclear polarization was investigated by pulse techniques. The relaxation data were supplemented by measurements of the proton and fluorine NMR second moments. Between −160°C and the melting point, the 1H second moment of each compound indicated that the protons were immobile. The 19F second moments indicated the effective reorientation of the CF3 group in all three compounds throughout the same temperature range. The relaxation of the 19F polarization was found to occur more rapidly than the corresponding 1H relaxation. Moreover, the relative rates of 1H and 19F relaxation also varied quite considerably with temperature. These results were analyzed by Solomon's treatment of heteronuclear relaxation. Semiquantitative agreement between theory and experiment was achieved for the C6H5CF3 relaxation data.
Approach to Simple Exponential Decay in Vibrational Relaxation
Authors: Carrington Tucker
Published: January 2005

When diatomic oscillators are dilutely dispersed in an inert heat bath, populations of the various vibrational levels in an initial nonequilibrium distribution relax toward thermal equilibrium with a time dependence that is a sum of terms like exp (λmt), where λ0=0, all other λm<0, and λm+1<λm. −1/λ1 ordinarily corresponds to the experimental relaxation time τ, since this term will dominate at long times. This work investigates cases in which the coefficient of the λ1 term, depending on the initial vibrational distribution and the heat-bath temperature, may vanish or be so small that the final simple exponential decay corresponding to λ1 is never reached under experimental conditions.

For harmonic oscillators, if the initial distribution has its first n moments equal to the corresponding moments of the equilibrium distribution, then the first n coefficients in the sum of exponentials will be zero. Furthermore, there will be one or more values of the heat-bath temperature, independent of the initial distribution, for which the normally dominant exponential decay will be missing in the expression for the time dependence of population in any particular level. Some of these results can be extended qualitatively to anharmonic oscillators and more general systems.
Raman Spectra of Molten Sulfates
Authors: Walrafen G. E.
Published: January 2005

Photoelectric Raman spectra of molten lithium and sodium sulfate have been obtained at 950°±10°C with a Cary Model 81 spectrophotometer modified for radio-frequency heating. Spectra of the corresponding aqueous solutions were also obtained. Comparisons of melt and solution spectra indicate differences in frequencies, in half-widths, and in ratios of integrated intensities. Explanations of the observed effects are advanced.
Triplet Excitons in Morpholinium TCNQ
Authors: Maréchal Marie-Antoinette , McConnell Harden M.
Published: January 2005

Certain coincidences are noted between (a) the magnetic axes of triplet excitons in morpholinium TCNQ and (b) crystallographic axes determined by x-ray diffraction. These coincidences can be understood quantitatively in terms of an assumed crystal structure in which pairs of TCNQ− molecules (``dimers'') have D2h point-group symmetry and dimer symmetry axes that (nearly) coincide with certain crystallographic axes of the triclinic crystal. Observed fine-structure splitting parameters, | D | = 450 Mc/sec, | E | = 53.8 Mc/sec are in excellent agreement with theoretical values D=−464 Mc/sec, E=44 Mc/sec calculated using Hückel spin densities on TCNQ molecules together with the assumption that there is no intermolecular charge (and spin) transfer in the triplet-exciton state.
Infrared Detection of Diimide, N2H2, and Imidogen, NH, by the Matrix Isolation Method
Authors: Rosengren Kjell , Pimentel George C.
Published: January 2005

Hydrazoic acid labeled with deuterium and 15N was photolyzed in solid nitrogen at 20°K. The 15N multiplet splitting positively identifies absorptions of photolysis products as those of trans-N2H2 (at 1286 cm−1), trans-HNND (at 1481 and 1058 cm−1), trans-N2D2 (at 946 cm−1), and cis-N2H2 (at 3074 and 1279 cm−1). The spectrum of trans-N2H2 is in agreement with a planar symmetric structure and the vibrational frequencies are quite close to corresponding vibrations of ethylene.

Imidogen, NH, was also observed in both solid argon and in solid nitrogen as another photolysis product. The 15N splitting in the ammonia absorptions shows that the ammonia dimer in solid nitrogen has a cyclic structure.
Mass-Spectrometric Study of Gaseous Oxides and Suboxides of Scandium, Yttrium, and Lanthanum
Authors: Smoes S. , Drowart J. , Verhaegen G.
Published: January 2005

The dissociation energy of the molecule ScO was determined: D0°(ScO) = 160.9±3.5 kcal/mole. The dissociation energies of the molecules YO and LaO, D0°(YO) = 168.6±2.8 and D0°(LaO) = 191.0±2.5 kcal/mole, are discussed. The molecules Sc2O, Y2O, Y2O2, La2O, and La2O2 were identified. Their atomization energies are: D0°(Sc2O) = 245±11, D0°(Y2O) = 258±8, D0°(Y2O2) = 445±12, D0°(La2O) = 266±8, D0°(La2O2) = 468±11 kcal/mole.
Nonadiabatic Transitions between Fine-Structure Components of Alkali Atoms upon Collision with Inert-Gas Atoms
Authors: Nikitin E. E.
Published: January 2005

The cross section for transition between fine-structure components of the 2Pj doublet of alkali atoms upon collisions with inert-gas atoms is calculated in strong coupling approximation. Various limiting coupling cases between momenta are discussed.
Emission Spectrum and Thermodynamic Properties of Ruthenium Monoxide
Authors: Raziunas Victor , Macur George , Katz Sidney
Published: January 2005

The band spectra attributed to the monoxides of ruthenium, rhodium, osmium, iridium, platinum, and rhenium were observed. A vibrational analysis of ruthenium monoxide and partial rotational analysis of the 0–0 band of ruthenium monoxide has been carried out. The band system has been tentatively attributed to a 3Σ+→X 3Σ+ electronic transition. The values of the vibrational constants are ω0′=878.1, ω0′x0′=22.4; ω0″=880.8 and ω0″x0″=13.1 cm−1. The values of the rotational constants are B0′=0.393 and B0″=0.422 cm−1, corresponding to internuclear distances r0′=1.76 Å and r0″=1.70 Å. The spectroscopic constants determined in this study were used to calculate the thermodynamic functions up to 3000°K.
Nuclear Spin Relaxation in Gases and Liquids. IV. Interpretation of Experiments in Gases
Authors: Bloom M. , Oppenheim I. , Lipsicas M. , Wade C. G. , Yarnell C. F.
Published: January 2005

The theory of nuclear spin relaxation in gases and liquids developed by Bloom and Oppenheim is used to interpret measurements of spin lattice relaxation times for various gaseous systems over wide ranges of temperature and density. The systems discussed include: molecular H2 with different ortho and para concentrations; mixtures of H2 with He, Ne, Ar, N2, CO2, O2, CO, NO, and N2O; and normal D2. The analysis leads to a determination of the form of the anisotropic intermolecular potentials providing that the form of the isotropic part of the intermolecular potentials are known. Values of quadrupole moments for H2, O2, N2, CO, NO, N2O, CO2, and D2 are obtained which are in good agreement with previous values. Thus, nuclear spin relaxation becomes a valuable tool for obtaining anisotropic intermolecular potentials.
Cohesive Energy of Copper
Authors: Prieto F. E. , Renero C.
Published: January 2005

The method used by Benedek to calculate the cohesive energy of solids from shock-wave compression data is generalized in this paper to include the effect of the volumetric dependence of Grüneisen's parameter γ; this is done using for γ a series expansion in the relative compression. It is found that the effect of this correction is negligible, especially at low pressures. The results obtained by this method, when compared with those of the numerical calculation of the integral expressing the formal solution of the differential equation, show that the approximation method is slowly divergent. These results lead to the conclusion that, in all cases, it is preferable either to calculate numerically the integral expressing the formal solution of the differential equation for the cohesive energy, or to take only the lowest-order approximation in both the Grüneisen's parameter and in the solution.
Intensity Distribution in the Electron-Impact Spectrum of Carbon Monoxide at High-Resolution and Small Scattering Angles
Authors: Meyer Vincent D. , Skerbele Ausma , Lassettre Edwin N.
Published: January 2005

An electron spectrometer, which provides velocity selection before scattering, is described; and the results of a study of relative intensities in the carbon monoxide spectrum are reported. The vibrational levels of the fourth positive band system have been resolved and relative intensities determined for the first nine. The relative intensities are compared with calculated Franck—Condon factors. The agreement is good at low vibrational quantum numbers but noticeable discrepancies are found for high-vibrational levels.

The problem of calculating relative oscillator strengths from a fully resolved spectrum is considered and applied to data obtained in the present research. Relative oscillator strengths are compared with those obtained previously from unresolved spectra.

If the Born approximation is valid, then the electron-impact and ultraviolet absorption spectra should be closely similar. This is actually observed for most of the spectrum but the transition at 12.79 V is an outstanding exception. The relative oscillator strength obtained from the electron-impact spectrum exceeds that from the ultraviolet absorption spectrum by almost a factor of 3. The reason for this anomaly is not known.
1s3d 3Πg State of the Hydrogen Molecule
Authors: Wright Wayne M. , Davidson Ernest R.
Published: January 2005

The potential curve and vibrational—rotational levels for the 1s3d 3Πg state of H2 have been computed in the Born—Oppenheimer approximation. Energy levels about 50 cm−1 below the experimental levels have been found. A discussion of the nature of the wavefunction is given.
Vibrational Spectra of Solutions of Zinc Oxide in Potassium Hydroxide
Authors: Fordyce J. Stuart , Baum Ruth L.
Published: January 2005

Raman and infrared reflection spectral studies of solutions of zinc oxide in potassium hydroxide (7.5 and 15m) with OH/ZnO ratios of from 8 to 16 show that the predominant species in these solutions possesses tetrahedral symmetry (Point Group Td) and is presumably the Zn(OH)42− ion. The frequencies and assignments, neglecting the hydrogen atoms, are: ν1(a1)=484 cm−1, ν2(e)=285 cm−1, ν3(f2)=430 cm−1, ν4(f2)=322 cm−1.
Configuration-Interaction Effects on the ``Free-Ion'' Energy Levels of Nd3+ and Er3+
Authors: Rajnak K.
Published: January 2005

By the use of three or four parameters of configuration interaction, the experimental ``free-ion'' energy levels of Nd3+ and Er3+ have been fitted with an rms deviation of 45–55 cm−1. The significance of the various parameter values is discussed. It is also shown that assignments based purely on comparison with a calculation using only F2, F4, F6, and ζ may occasionally be in error. Several discrepancies in previous work are now cleared up.
Effects of Electron Correlation in X-Ray and Electron Diffraction. II. Influence of Nuclear Charge in Two-Electron Systems
Authors: Bartell L. S. , Gavin R. M.
Published: January 2005

The electron—electron and electron—nuclear radial distribution functions P(r12) and D(r) have been calculated for ground states of heliumlike systems (Z=2 to 8). Computations were based on the correlated and uncorrelated wavefunctions published by Roothaan et al. Elastic and inelastic scattering factors for calculating the intensities I([open phi]) of x rays scattered by two-electron systems were determined from the distribution functions. The correction functions ΔP(r12) and ΔI([open phi]) representing the differences between correlated and uncorrelated results were found to follow a simple dependency on atomic number. It was observed that universal functions could be established which closely approximated each of the functions D(r)/Z*, P(r12)/Z*, I([open phi]), ΔP(r12), and Z*ΔI([open phi]) for all of the systems studied if the functions were expressed in terms of the reduced variables r′=Z*r and [open phi]′=2 arcsin[Z*−1 sin([open phi]/2)]. The appropriate Z* was very nearly the Slater effective nuclear charge. The experimental determination of P(rij) from x-ray scattering and the magnitude of correlation effects to be expected are briefly discussed.
Experimental Study of Luminescence and Excitation Trapping in Vinyl Polymers, Paracyclophanes, and Related Compounds
Authors: Vala Martin T. , Haebig Jon , Rice Stuart A.
Published: January 2005

The results of an experimental investigation of luminescence and energy trapping in the polymeric systems atactic and isotactic polystyrene and atactic polyvinylnaphthalene are presented. It is shown that the anomalous emission bands observed at 3350 Å in the polystyrenes and at 4100 Å in atactic polyvinylnaphthalene are transitions from an excimer state formed by the interaction of nearby chromophores on the same polymer chain. In support of this interpretation, the spectra of a number of model compounds in the diphenylalkane and paracyclophane series are presented and analyzed. The role of charge-transfer-state contribution to the splitting in rigidly helical isotactic polystyrene is investigated and conclusions concerning the microscopic conformations of the polymer chromophores are drawn. In addition, the possibility of excitation energy trapping due to conformational changes of the chromophore groups is discussed.
Light Scattering by Pure Water
Authors: Kratohvil J. P. , Kerker M. , Oppenheimer L. E.
Published: January 2005

The Rayleigh ratio and depolarization of water have been measured under a variety of experimental conditions at two wavelengths and the same data from the literature critically discussed. These experimental results are compared with the Rayleigh ratios calculated from the Einstein equation corrected for depolarization. We find that the best experimental results agree closely with the theoretical values. The possibility of obtaining information on the structure of water from light scattering is discussed.
Analysis of the NMR Spectrum of Tetraborane
Authors: Hopkins Robert C. , Baldeschwieler John D. , Schaeffer Riley , Tebbe Fred N. , Norman Arlan
Published: January 2005

The 11B NMR spectrum of B4H10 consists of a low-field triplet exhibiting secondary triplet splitting and a high-field doublet having extensive fine structure. A reinterpretation of this spectrum is proposed. The triplet structure arises from coupling of 11B in the BH2 groups to the two terminal protons and to the two adjacent bridge protons. The doublet can not be assigned from first-order considerations. 11B–{1H} double resonance and 10B and 11B substitution studies indicate that the doublet fine structure arises from strong 11B–1H coupling interactions. The signs of JBH and JBBH are shown to be opposite from a comparison of the observed and calculated 11B spectra of tetraborane samples with various 10B/11B isotopic ratios. The proton spectrum of B4H10 consists of a quartet on which is superimposed a broad feature plus several smaller peaks. The spectra calculated for the 11BH2, 10BH2, and BH terminal protons and the bridge protons account for all the peaks in the 1H spectrum. A difference in the ease of rf saturation of the triplet and doublet in the 11B spectrum is attributed to differences in the electric-field gradients at the BH and BH2 boron sites.
Conduction in Paraffinic Polymers
Authors: McCubbin W. L. , Gurney I. D. C.
Published: January 2005

A band scheme is developed for the linear paraffinic polymer. It is found that the valence band is 10 eV wide and that the hole effective mass is 0.1 m. Consistency with experiments on dc conductivity is invoked to decide the identity of the thermal and optical transitions which generate holes. The results are at best semiquantitative and are intended as a preliminary to more rigorous calculations. The proposed band structure is shown to be capable of explaining the thermoluminescence emission spectrum, although more data would be required for a detailed analysis.

Since there is evidence that certain types of substitution may be treated as a perturbation of the paraffinic system, the band model is extended to polymers of type (—CH2—CHR—)n. It is concluded that the resistivity may be lowered by the substitution, but that no choice of R will yield a greater resistivity than that of the paraffinic polymer.
Kinetics of the Hydrofluorination of Thorium Dioxide
Authors: Lindstrom R. M. , Ellis W. P.
Published: January 2005

Uniformly colored and optically isotropic interference films of thorium tetrafluoride were formed on the polished trigonal faces of single crystals of thorium dioxide by reaction with gaseous hydrogen fluoride. The kinetics were determined spectrophotometrically at six temperatures in the interval 218°—327°C. The reaction is diffusion controlled with the film thickness proportional to the square roots of pressure of HF(g) and time corrected for an incubation period. The rate constant is β=7.0×102exp(−6630/RT)Å/(sec·Torr)12 within an error (75% confidence) of ±280 cal/mole for the heat of activation.
Perturbation Treatment of the Ground State of HeH+ +
Authors: Matcha Robert L. , Lyon William D. , Hirschfelder Joseph O.
Published: January 2005

Rayleigh—Schrödinger perturbation calculations are carried out for the ground state of the HeH+ + molecular ion. The zeroth-order wavefunction is ψ=Nexp(−αZArA−βZBrB).The expectation value of the Hamiltonian calculated with the wavefunction accurate through first order, E(1), is compared with the accurate series calculations of Bates and Carson and found to agree up to five places. Also the values of the normalized wavefunction accurate through the first order agree quite well with Bates and Carson, particularly for small values of the internuclear separation.
Multiple Elastic Intramolecular Scattering in Gas Electron Diffraction
Authors: Bonham R. A.
Published: January 2005

The effects of multiple elastic intramolecular scattering on gas-electron-diffraction patterns are calculated in the second Born approximation. Expressions for the first-order double- and triple-scattering contributions are obtained. An approximate expression convenient for computation, for the first-order triple-scattering term is also given. The relationships of the magnitude of the multiple scattering to atomic number, atomic size, and molecular structure are investigated. It is shown that corrections to the reduced molecular-intensity function of the order of several percent can occur in the case of triple scattering from three or more heavy atoms in close proximity.
Crystal Structure of Tellurium at High Pressures
Authors: Jamieson J. C. , McWhan D. B.
Published: January 2005

Powder x-ray-diffraction studies on tellurium up to 150 kbar show only two structural transitions at 40 and 70 kbar in agreement with Bridgman's work. The structure of the 40–70-kbar phase is unsolved. Above 70 kbar, it is proposed that tellurium is isomorphous with β-polonium and is rhombohedral with a=3.002±15 Å, α=103.3°±3° (P=115 kbar), space group R3̄m with an atom in 1a (0, 0, 0).