bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate Equation for Dissociation and Recombination of Diatomic Molecules
Authors: Snider Neil S.
Published: January 2005

Results have been obtained which indicate that a necessary condition for the phenomenological rate equation [Eq. (1)] to hold in dissociation—recombination of diatomic molecules A2 is that the concentration of Atoms A be sufficiently small. It is estimated that this condition is met for values of the atom concentration which have been obtained experimentally and that it would continue to be met for values of the atom concentration which are larger than the experimental values by several orders of magnitude.
Different Orbitals for Different Spins. Singlet S Ground State of Helium
Authors: Chong D. P.
Published: January 2005

The ``different-orbitals-for-different-spins'' (DODS) wavefunction for the ground state of He is expressed in terms of Shull and Löwdin basis orbitals. The energy and the occupation amplitudes of the two approximate natural orbitals have been obtained by solving two coupled pseudoeigenvalue matrix equations. The DODS wavefunction accounts for 94% of the radial correlation energy.
On the Eu3+ Fluorescence in Mixed Metal Oxides. V. The Eu3+ Fluorescence in the Rocksalt Lattice
Authors: Blasse G. , Bril A.
Published: January 2005

The fluorescence of phosphors ABO2:Eu(A=Li, Na; B=Sc, Y, In, La, Gd, and Lu) is reported and discussed. The Eu3+ emission is strongly influenced by the crystal surroundings: in the α-NaFeO2 structure the 5D0—7F1 transition dominates; in the α-LiFeO2 structure the 5D0—7F2 transition, although both structures can be derived from the rocksalt structure. The greater part of the phosphors is excited directly into the Eu3+ center by shortwave uv radiation. The strong excitation band in this region is ascribed to a charge-transfer process. It is shown that the position of this band is dependent on the cations in the lattice. A relation exists between the efficiency of the phosphors and the position of the charge-transfer band. A possible explanation is put forward. The concentration quenching of the fluorescence of NaGd1−xEuxO2 was studied. Quenching occurs at x=0.1, which agrees with Van Uitert's theory on this phenomenon.
Theory of Radiation Chemistry. VII. Structure and Reactions in Low LET Tracks
Authors: Mozumder A. , Magee J. L.
Published: January 2005

The low LET track of an electron is composed of a random sequence of more or less isolated entities called spurs, blobs, and short tracks. The distribution function for these track entities has been considered in detail by a Monte Carlo technique. In order to evaluate the effect of the more accurate structure on calculated chemical yields, as contrasted with the simpler spur model, the diffusion equations were solved numerically for the one radical case. The more elaborate track model introduced here has a kind of high LET component embedded in it through the ``short tracks.'' This investigation shows that for electron irradiations all LET effects result from the variation in fraction of energy deposited in short tracks. Effects of overlapping of various track entities during the diffusion and reaction phase are negligible.
d Orbitals in the Excited Sulfur Atom
Authors: Craig D. P. , Thirunamachandran T.
Published: January 2005

Sulfur 3d orbitals in the sp3d2 configuration are represented by a two-term Slater wavefunction. The energies of the 7F, 7P, 5H, 3I, 1I, and one of the 1S terms are minimized with respect to the two wavefunction exponents and the mixing coefficient. The core wavefunction is the same throughout. In the deeper terms the d orbitals have mean radii upwards from 1.85 Å (7F). In the highest term considered, the mean radius is 2.65 Å (1S). In a single-configuration valence state the mean radius is at 2.39 Å, and in the (multiconfiguration) valence state for equivalent octahedral hybrids it is 1.67 Å.
Temperature Dependence of the Nuclear Quadrupole Resonance Frequencies in Para-Dichlorobenzene
Authors: Moross George G. , Story Harold S.
Published: January 2005

The temperature dependence of the pure nuclear quadrupole resonance frequencies in three solid phases of para-dichlorobenzene has been measured in the range of 77° to 300°K and compared with the measurements of Babushkina and Baisa. Good agreement with the Bayer—Kushida theory is obtained.
Oscillatory Flow Birefringence of Polymer Molecules in Dilute Solutions
Authors: Thurston G. B. , Schrag J. L.
Published: January 2005

A theory for the behavior of dilute solutions of polymer molecules in oscillatory shear has been given by Zimm. Two variable parameters are contained in the theory, these being the number of statistical chain segments which are joined by bead joints and the degree of hydrodynamic interaction between the beads of the chain model. While previous experimental evaluations of the theory as applied to viscoelasticity have been restricted to the case of an infinite number of segments, the results obtained from oscillatory flow birefringence measurements show that a finite number of segments is essential to describing the behavior of the polymer. The analysis of birefringence measurements in terms of the Zimm theory yields values for the longest relaxation time τ1, the number of segments N, the reduction function aT, and the optical factor q′ characteristic of the subchain as well as the temperature dependence of the friction factor. Both oscillatory and steady-flow birefringence measurements for polystyrene S111 in Aroclor 1248 are compared with the theory for frequency and temperature dependence. For the solution tested, N lies between 40 and 100, τ1 is 0.00187 sec and the temperature dependence of the friction factor is approximately that of the solvent viscosity.
Vibration—Rotation Spectra of Monomeric HF in the Rare-Gas Lattices. II
Authors: Bowers M. T. , Kerley G. I. , Flygare W. H.
Published: January 2005

The infrared spectra of HF, in the region of the HF fundamental, in the Ne, Ar, Kr, and Xe matrices are presented. Concentration and temperature-dependent studies enable assignment of the spectral lines due to the monomeric species. The monomeric HF spectra exhibit rotational—vibrational perturbations similar to the other hydrogen halides in the rare-gas lattices. Analysis of the spectra indicates that the barrier to rotation is small. The rotational splittings are interpreted on the basis of coupling between rotation and translation of the molecule.
7Li Nuclear Electric Quadrupole Interactions in Alkyllithium Compounds
Authors: Bernheim R. A. , Adler I. L. , Lavery B. J. , Lini D. C. , Scott B. A. , Dixon J. A.
Published: January 2005

The 7Li magnetic resonance in polycrystalline methyllithium-d3 and ethyllithium-d5 was examined at room temperature and at 77°K. The 7Li quadrupole coupling parameters were determined from the quadrupole fine structure of the 7Li magnetic resonance to be | e2qQ/h | = 48 kc/sec and η = 0 for methylithium-d3 and | e2qQ/h | = 83 kc/sec and η = 0.79 for ethyllithium-d5. The quadrupole coupling is independent of temperature for ethyllithium-d5, but the temperature dependence of the coupling is uncertain for methyllithium-d3 because of the difficulties in observing the resonance at 77°K. At room temperature the 7Li magnetic resonance of ethyllithium-d5 exhibits a narrow component, 87 cps broad, superimposed upon the broad, quadrupolar split line. This sharp component, which is similar to that observed in isopropyllithium, t-butyllithium, and neopentyllithium, is not observed at 77°K and is presumably due to motional narrowing. The 7Li resonance of methyllithium-d3 displayed no sharp component at room temperature, being like allyllithium, propynyllithium, phenyllithium, fluorenyllithium, and alkoxylithium compounds in this respect.
Chlorine Kβ X-Ray Emission Spectra from Several Chlorinated Hydrocarbon and Fluorocarbon Molecular Gases
Authors: LaVilla R. E. , Deslattes R. D.
Published: January 2005

Emission profiles have been obtained in x-ray fluorescence for the four chlorinated derivatives of methane (CH3Cl, CH2Cl2, CHCl3, CCl4), and five chlorinated fluoromethanes (CF3Cl, CF2Cl2, CFCl3, CHFCl2, and CHF2Cl) in the gas phase. The chloromethanes contain two prominent lines whereas the chlorofluoromethanes have multiplet structures of up to four lines. Evidence is presented which suggests that these structures may be interpreted in terms of the molecular orbital term energies.
Contribution of Surface Distortion to the Surface Energy of Alkali Halide Crystals
Authors: Benson G. C. , Balk P. , White P.
Published: January 2005

The distortion of the {100} face of the NaCl-type lattice and its influence on the surface energy have been considered using a model in which the ions of the first crystal layer are allowed to displace separately and to polarize. van der Waals terms have been included in the potential function in order to make the treatment consistent with existing classical calculations on the surface energy of the undistorted surface. The configurations of lowest energy and the corresponding surface energy corrections have been computed for all NaCl-type alkali halides except LiF, for which compound no stable minimum could be found. A short discussion on the approximational aspects of the calculations is given.
Activation Energy for Hole Motion in LixNiyCo1—x—yO
Authors: Miller R. C. , Heikes R. R. , Johnston W. D.
Published: January 2005

The electrical resistivity of LixNiyCo1—x—yO shows an anomalous increase at y=0.84, the composition at which the amount of Li is equal to the amount of Co. This increase, predominantly caused by a corresponding increase in activation energy, is interpreted as evidence that the electrical conduction mechanism may be represented as a thermally activated diffusion of positive holes having a mean free path or jump distance of one lattice distance.
On the Dynamical Theory of Diffusion in Crystals. II. Pressure Dependence of the Self-Diffusion Constant
Authors: Rice Stuart A. , Nachtrieb Norman H.
Published: January 2005

A dynamical theory of diffusion developed previously is extended to the study of the pressure dependence of the self-diffusion constant. It is shown that in the limit of low pressures there exists a law of corresponding states of the form lnD∝Tm/Twhere Tm is the melting temperature of the crystal. It is further shown that the temperature and pressure derivatives of the self-diffusion coefficient are related as ΔH†=(ΔHm/ΔVm)ΔV†with a dagger referring to activated quantities and a subscript m to fusion parameters. Application of the theory is made to Na and Pb. For Pb, the computed heat of activation is 24 300 cal to be compared with the experimental value of 24 210 cal.
Dynamic Stability of Frozen Radicals. I. Description and Application of the Model
Authors: Jackson J. L.
Published: January 2005

The dynamic stability of a mixture containing free radicals is considered. On the basis of a simplified model we estimate a critical free radical concentration, such that any greater concentrations will be able to ignite spontaneously. For nitrogen atoms in a nitrogen molecule lattice this number is of the order of 0.3% under typical conditions.
Free Radical Statistics
Authors: Chessin Paul Lawrence
Published: January 2005

On the basis of the Ising model, average concentrations of trapped free radicals condensed from a gas are obtained. The trapped free radical concentration is obtained as a function of various lattice configurations. Trapped free radical concentrations range from 16% for a one-dimensional lattice to 6.5% for a face-centered cubic lattice.
Thermodynamic Properties of Nitryl Chloride
Authors: Ray James D. , Ogg Richard A.
Published: January 2005

The calorimetric heat of formation of gaseous nitryl chloride from the elements at 25° has been found from the heat of the reaction of gaseous nitryl chloride with nitric oxide as confirmed by the heat of the reaction between nitrosyl chloride and nitrogen pentoxide. The value is +3.12±0.16 kcal/mole (endothermic). From the equilibrium constants for the reactions 2NO2+Cl2=2ClNO2 and NO2+ClNO=NO+ClNO2 the entropy of nitryl chloride at 25° has been found to be 65.46±0.6 eu.
Paramagnetic Resonance Spectrum of the Fluoroferrate Ion, FeF6———
Authors: Helmholz Lindsay
Published: January 2005

The fluorine hyperfine structure in the paramagnetic resonance spectrum of the fluoro-ferrate ion, FeF6———, has been observed in a solid solution of the ion in K2NaGaF6. From the isotropic and anisotropic components of the spectrum the magnitudes of the coefficients of the fluorine atomic obitals in the molecular orbitals occupied by the unpaired electrons are estimated. The results are compared with results on Mn++ dissolved in other fluorides.

The antibonding eg orbitals are found to contain about 2.5% fluorine 2s orbital and approximately 10% fluorine 2p orbital.
Influence of Pressure on the Hammett Reaction Constant
Authors: Ellis A. J. , Fyfe W. S. , Rutherford R. I. , Fischer A. , Vaughan J.
Published: January 2005

The probable effect of pressure on the Hammett reaction constant is predicted for heterolytic and homolytic reactions in polar and nonpolar solvents. There are insufficient data in the literature to test the conclusions reached but some previously unpublished measurements appear to be in line with one prediction.
Open-Shell Ground-State Energy of the He2+ Molecule Ion
Authors: Csavinszky P.
Published: January 2005

``Open-shell'' calculations have been made for the He2+ molecule ion. Two different three-parameter wave functions have been tried and the results are compared with ``closed-shell'' calculations of other authors.
Electrochemistry of the Semiconductor-Electrolyte Electrode. I. The Electrical Double Layer
Authors: Green Mino
Published: January 2005

The thermodynamics of the semiconductor-electrolyte electrode (S/C—E electrode) are examined. The following is concluded about the distribution of the p.d. (potential difference) due to excess charge V in the interphase (assuming the dipole distribution to be invariant with semiconductor electron concentration): (i) For a semiconductor, with a nondegenerate free carrier distribution throughout and no surface states, in contact with a concentrated electrolyte solution (such that the Gouy layer p.d.→0), most of V occurs within the semiconductor phase and the p.d. across the compact Helmholtz layer is small (millivolts). Changes in p.d. across the S/C—E electrode caused by an externally applied p.d. will occur mainly in the S/C phase (if the electrolyte is concentrated); (ii) For a S/C—E electrode with a high concentration of ionized surface states of one kind, p.d. caused by excess charge in the Helmholtz layer, H will be large (∼1 volt) and the electrode behaves like a metal electrode. The Helmholtz layer p.d., H, is found to be essentially independent of bulk S/C electron concentration. An applied p.d. is mainly manifest across the Helmholtz layer (when the electrolyte solution is concentrated).
Isotope Enrichment Factors for Nitrogen-15 in the Nitric Oxide-Nitric Acid Exchange System
Authors: Kauder Lois Nash , Taylor T. I. , Spindel W.
Published: January 2005

Single stage enrichment factors, α, for the isotope exchange reaction of nitrogen-15 between oxides of nitrogen and solutions of nitric acid have been determined by two different methods. Single stage equilibrations resulted in values of α that decrease from 1.065 for approximately 1M HNO3 to 1.045 for 11.1M HNO3. At high acid concentrations, α decreases rapidly owing to high concentrations of NO2 and N2O4 in the gas phase. Steady-state over-all separations in an exchange column at several rates of product with-drawal gave an independent determination for the 10M HNO3 used in the preparation of highly enriched nitrogen-15. Data from the two methods result in a value for α of 1.055±0.005 for approximately 10M HNO3 at 25°C.
Concentration-Dependent Sedimentation in Two-Component Systems, with Reference to Differential Boundaries
Authors: Fujita Hiroshi
Published: January 2005

This paper shows that if a sedimentation velocity experiment is performed on a binary system using an initial boundary formed between solutions of slightly different concentrations, the observed data can be analyzed to evaluate s and D for any type of concentration dependence of s; here s is the sedimentation coefficient of the solute and D is the diffusion coefficient of the system. The Lamm differential equation for sedimentation of a single, homogeneous solute in the ultracentrifuge cell is solved in closed form by employing approximations which are appropriate under this initial condition. Equations for the movement of the boundary gradient curve and its height-area ratio are derived from the approximate solution obtained. From these equations, procedures are developed which permit determination of the values of s and D for the mean concentration of the two starting solutions and the first derivative of the dependence of s on concentration at this composition.
Carbon-Hydrogen-Acetylene Equilibrium at High Temperatures
Authors: Plooster Myron N. , Reed Thomas B.
Published: January 2005

The concentration of acetylene in equilibrium with carbon and hydrogen at temperatures up to 3000°K has been measured experimentally using water-cooled quenching probes in a carbon tube furnace. Previous calculations of the thermodynamic properties of acetylene have been extended to cover this temperature range. Also, the effects of free radical species present at these temperatures were estimated. The only ones deemed important in the temperature range of this investigation were H and C2H; an estimate was made of the free energy of C2H to predict its effect on the composition of the quenched gas samples from the furnace. The predicted quenched gas compositions are in good agreement with the experimental measurements.
Pressure Induced Shifts of HCl Absorption Lines in the Infrared
Authors: Kimel S. , Hirshfeld M. A. , Jaffe J. H.
Published: January 2005

The shift of infrared absorption lines due to pressure changes are small and they are difficult to measure. However it has been found possible to study this effect with the large spectrometer in Rehovoth which is particularly suited for the determination of small wavelength differences. Pressure induced shifts of the individual lines of the HCl 2–0 band at 1.76 μ have been measured over a range of pressures below atmospheric. A strong dependence of the shift on the rotational quantum numbers was found. For self-shifts the lines near the band center were shifted toward the blue and others toward the red. The results are discussed qualitatively. Measurements on shifts due to the addition of a foreign gas are also reported.
Molecular Transfer of Nonequilibrium Nuclear Spin Magnetization
Authors: McConnell Harden M. , Thompson Don D.
Published: January 2005

A new magnetic resonance technique has been developed to measure the rates of fast molecular processes. The method involves the experimental introduction of a nonequilibrium nuclear magnetization in one system A, and the subsequent measurement of the rate at which rapid molecular processes transfer this nonequilibrium magnetization to a second system B. Systems A and B may correspond to different chemical sites in a molecule that give rise to a chemical shift, or to sites that are distinct because of electron coupled spin-spin interaction. This technique has been applied to determinations of the rate of proton exchange between ammonium ions in aqueous solution.
Chemical Bond. III. A One-Dimensional Theory of the Energetics and Ionic Character of the Hydrogen Bond
Authors: McKinney Paul C. , Barrow Gordon M.
Published: January 2005

The bond properties of a first row element bonded to a hydrogen atom are calculated from one-dimensional counterparts of the atomic orbitals. The potential energy function and the ionic character are found to be correctly predicted.

The hydrogen bond system O–H···O is described by means of the same atomic wave functions. The potential energy of the system is obtained for various positions of the hydrogen atom. Predicted properties are in good agreement with experiment. The existence of a second potential minimum is indicated. The contributions of the resonating structures of the system are obtained and are shown to lead to the observed value of dμ/dr for the hydrogen bonded OH system.
Physically Meaningful Concepts
Authors: Redlich Otto
Published: January 2005

A statement on distillation lines, made by Schreinemakers and repeated by Korvezee and Meijering, lacks any physical meaning.
Theoretical Depolymerization Kinetics in Polymers Having an Initial ``Most Probable'' Molecular Weight Distribution
Authors: Boyd Richard H.
Published: January 2005

The kinetic equations describing a general chain mechanism of depolymerization are solved at steady state for a polymer having an initial ``most probable'' molecular weight distribution. Chain scission initiation, end group initiation, depropagation, intermolecular chain transfer, and several types of termination are considered.

In the past, solutions have been limited to special cases and approximations. Now general expressions for molecular weight change and rate of weight loss are available for polymers with an initial molecular weight distribution of wide interest. The relationships to the previously considered special cases are discussed.
Field Desorption
Authors: Gomer Robert
Published: January 2005

A theory of field desorption covering both covalent and ionic binding is presented. The mechanism corresponds to field ionization preceded by complete or partial ordinary desorption in the former and to direct ionic evaporation in the latter case. Comparison with experiment shows that field desorption of Ba can proceed via Ba+ or Ba+2. It is pointed out that field desorption could be used to investigate the shapes of potential curves in adsorption.
Electron Spin Resonance of Ultraviolet Irradiated Compounds. I. Unsaturated Hydrocarbons
Authors: Poole Charles P. , Anderson Roy S.
Published: January 2005

Trapped radicals, formed by ultraviolet irradiation of pure, unsaturated aliphatic hydrocarbons, maintained at 77°K, have been observed with a 3-cm electron spin resonance spectrometer at a g factor of two. Straight-chain alkene radicals were characterized by well-resolved hyperfine structure of four or more components. Branched-chain alkene radicals showed more but poorly resolved components. Only those hydrogen atoms attached to carbon atoms at or adjacent to the location of the unpaired electron are found to contribute appreciably to the observed hyperfine structure. Their hyperfine coupling constants are approximately equal.

Radical formation and stabilization is attributed to the separation from the parent molecule of highly mobile hydrogen and methyl radicals which diffuse away from the remaining radical fragments, and eventually react with their environment or recombine. Stabilization of remaining fragments then occurs because of immobility and structural resonance. The number of radical spins detected was of the order of 1016 to 1018 in 1-ml samples. Most radicals were stable for weeks at 77°K. Consideration is given to the existence of radicals resulting from secondary hydrogen addition reactions.
On the Use of Harmonic Oscillator Wave Functions in the Treatment of Anharmonic Crystals
Authors: Walnut Thomas H.
Published: January 2005

An analysis is made of the quantum-mechanical treatment of a crystal as a perturbed harmonic oscillator. The relative magnitudes of the elements of the Hamiltonian matrix with harmonic oscillator wave functions as a basis, are obtained for an anharmonic crystal. It is found that the harmonic oscillator wave functions are extremely poor approximations (in the ordinary sense) to the true wave functions.
Expected Square of the Length of a Hydrocarbon-Type Chain
Authors: Tobolsky Arthur V.
Published: January 2005

Three successive bonds along a hydrocarbon chain may be in a planar trans configuration or in two nonplanar gauche configurations. The energy of the trans configuration is taken as zero and the energies of the two gauche configurations are each taken as ε (per mole). The mean square length of a hydrocarbon-type chain of n links each of length l0 is shown to be r̄2=[(2+6a)/(3−3a)]nl02, where a=1/[1+2 exp(−ε/RT)]. The problem of excluded volume is not considered here.
Paramagnetic Resonance of Color Centers in Germanium-Doped Quartz
Authors: Anderson John H. , Weil John A.
Published: January 2005

Measurements of the paramagnetic resonances in single crystals of x-irradiated germanium-doped quartz have been carried out. The g tensors have been obtained and the hyperfine structure has been partially interpreted. Two radiation-damage centers are found with similar structures. A model for the centers is suggested, consisting of an unpaired electron located on an impurity center composed of a substitutional germanium atom surrounded by four oxygen atoms with an alkali ion in an adjacent interstitial position on a twofold axis.
Intermolecular Energy Transfer and Concentration Depolarization of Fluorescent Light
Authors: Ore Aadne
Published: January 2005

On the basis of Förster's general theory of energy transfer by resonance an expression has been derived which represents that fraction of the fluorescent light in a solution which is emitted by the same molecules that absorbed the incident photons. The formula applies up to about the critical concentration. It is founded on more complete considerations of nearest neighbors than those which lead to Förster's formula for the region of small concentrations. The relative merits of the two formulas are demonstrated by an application to the phenomenon of concentration depolarization of fluorescence.
Electron Diffraction Study of the Structure of Phosphine
Authors: Bartell L. S. , Hirst R. C.
Published: January 2005

The structure of gaseous phosphine was investigated by the sector-microphotometer method of electron diffraction. It was found that the length of the P–H bond was rg (0) = 1.437±0.004 A and the root-meansquare amplitude of vibration was 0.085±0.008 A where the quoted uncertainties represent standard errors. The asymmetry of the stretching vibration was estimated and used to deduce the approximate equilibrium bond length, re∼1.419 A. The H–H distance, while observed, was not sufficiently accurate to provide a useful value of the bond angle. The diffraction values are compared with spectroscopic values considering briefly the effect of the zero-point vibrations on each.
Laws of Corresponding States for the Thermal Conductivity of Molecular Solids
Authors: Keyes Robert W.
Published: January 2005

It is found that measured thermal conductivities of solid neon, argon, and krypton obey a law of corresponding states based on molecular units. Deviations from the law due to quantum mechanical effects are noted, and a modified law which takes account of the quantum mechanical phenomena and is also applicable to solid parahydrogen is given. A law of corresponding states for the thermal conductivity based on the critical constants is also found to give a good representation of the data for the solidified inert gases.
Spectroscopic Evidence for Long-Range Repulsive Intermolecular Forces
Authors: Robertson W. W. , King A. D.
Published: January 2005

Experimental results are presented on the shift of wavelength of absorption of benzene, naphthalene, pyrene, and phenanthrene with density of the diluents helium and nitrogen. Arguments are presented to show that the blue shift observed in the benzene 1Lb spectrum in helium is neither due to short-range repulsive forces nor to long-range dispersive forces. It is presumed that there are weak, long-range, nondispersive forces present in the benzene-helium interaction that have the character of repulsive forces.
Sequence and Spacing of n→π Transitions in s-Triazine
Authors: Brinen J. S. , Goodman Lionel
Published: January 2005

Calculations are made by the MO method, including zeroth-order configuration interaction of the lowest singlet and triplet (n, π*) state energies in s-triazine in three approximations: (1) including only one- and two-center integrals evaluated theoretically; (2) including three-center integrals evaluated semiempirically; (3) different overlap approximation, integrals evaluated empirically. Under all three approximations, the four lowest singlet-singlet excitations comprising one allowed and three forbidden transitions are predicted to be grouped within 1 ev and the lowest energy excitation is predicted to be forbidden. The assignment of the lowest energy transition is dependent upon 3-center integral values and is tentatively 1E″←1A′1. The lowest n→π* singlet-triplet excitation is predicted to be orbitally forbidden (3E″←1A1′) with a split of ∼0.8 ev from the corresponding singlet, and approximately degenerate with the lowest energy (π→π*) multiplicity-forbidden transition (3A1′←1A1′). The dependence of the energy levels upon the n-orbital hybridization is investigated.
Excess Ultrasonic Absorption in Diethylamine-Water Mixtures
Authors: Barfield R. N. , Schneider W. G.
Published: January 2005

The ultrasonic absorption and velocity as well as the density and shear viscosity of mixtures of diethylamine and water have been measured as a function of composition and temperature. The absorption, which is strongly temperature dependent, reaches a large peak value at a composition of approximately 10 mole percent diethylamine. Less pronounced maxima are observed in the sound velocity and shear viscosity. The system exhibits a pronounced volume contraction on mixing with evolution of heat. The origin of the large ``excess'' sound absorption can be accounted for in terms of a compressional relaxation and a simple molecular model based on the properties of the hydrogen bonds between like and unlike molecules in the binary solution. During compression an excess number of AB bonds are formed at the expense of AA and BB bonds leading to a relaxation process. The calculated absorption curves satisfactorily reproduce the main features of the experimental curves and yield approximate values of the mean relaxation frequency.
Electronic Structure of LiH Ion
Authors: Platas O. , Hurst R. P. , Matsen F. A.
Published: January 2005

A valence-bond calculation has been carried out for (LiH)+ with all twenty structures possible from Slater orbitals 1s, 2s, 2p on lithium and 1s(=1h) orbital on hydrogen. The total electronic energy computed for the ion at the equilibrium distance for the LiH molecule is — 209.50 ev with only the 1s21h structure making a significant contribution to the ground state. When this energy is combined with the corresponding calculated energy for the molecule, a vertical ionization energy of 7.52 ev is obtained. No experimental value has as yet been reported.

A technique is developed and is used to obtain the optimum orbital exponents for 1s21h over a wide range of internuclear distance. This calculated energy vs distance curve has no minimum suggesting that (LiH)+ is unstable with respect to dissociation.

At R=3.08 au the wave function is ``degenerate,'' that is, two different extremum sets of exponents yield the same energy. The principal difference is that the orbital exponent of the 1h function is 0.49 in one set and 1.04 in the other. At R>3.08 au the second set gives the lowest energy while the reverse is true for R<3.08 au. This is interpreted as representing the promotion 1s→2s as is required in approaching the united atom.
Molecular Diffusion Studies in Gases at High Temperature. III. Results and Interpretation of the He—A System
Authors: Walker R. E. , Westenberg A. A.
Published: January 2005

Experimental measurements of the binary diffusion coefficient of He—A obtained by the point-source technique over the temperature interval 300–1100°K are presented. The data include the extremes of the concentration dependence for DHe - A measured at 298°K. Interpretation is made in terms of a purely repulsive interaction between the atoms; the concentration dependence is included in the theoretical analysis. Comparison is made with the He—A interaction obtained from other sources. At the highest temperature, the measurements overlap the range of validity of diffusion coefficients predicted from the potential obtained by Amdur et al. from small-angle scattering experiments. Good agreement is shown to exist between the two types of experiments, which further substantiates the validity of predicting high-temperature transport properties from scattering potentials.
Interaction of Excitation Waves in a One-Dimensional Crystal
Authors: Merrifield R. E.
Published: January 2005

The problem of exciton-exciton interaction in molecular crystals is discussed in terms of the stationary two-quantum excited states of an idealized one-dimensional crystal. If only a single molecular excited state is considered, the wave functions and energy levels of the two-quantum states may be obtained directly from those of the corresponding one-quantum problem with the proviso that the two excitons have different wave numbers. If in addition, a second molecular excited state is included, there can exist states in which two excitons remain bound to each other as they propagate through the crystal.
Statistical Mechanical Theory of Transport Processes. XII. Dense Rigid Sphere Fluids
Authors: Rice Stuart A. , Kirkwood John G. , Ross John , Zwanzig Robert W.
Published: January 2005

The theory of transport in a dense fluid of rigid spheres is developed from classical statistical mechanics by the use of phase space transformation functions. A modified Maxwell-Boltzmann integro-differential equation for the distribution function in μ space is derived, and the difference between this equation and the Enskog equation is discussed. To obtain a formulation of the stress tensor and heat flux solely in terms of binary collisions, it is necessary to allow the time of coarse graining to be very short. The implications of this are discussed with relation to the general principles of the statistical mechanics of transport. The viscosity and thermal conductivity of the dense rigid sphere fluid are calculated. The viscosity is the same as that first computed by Enskog, but the thermal conductivity differs from his calculations.
Statistical Mechanical Theory of Transport Processes. XIII. Kinetic Theory of Dense Rigid Sphere Fluids
Authors: Rice Stuart A.
Published: January 2005

This paper discusses the details of the calculation of the coefficients of shear viscosity and thermal conductivity for a moderately dense fluid of rigid spheres based on a modified Boltzmann equation previously derived. The physical significance of short time smoothing and its effect on the computed transport co-efficients is briefly considered.
Elastic Scattering of Slow Ions in Gases
Authors: Mason Edward A. , Vanderslice Joseph T.
Published: January 2005

Differential cross sections for the elastic scattering of slow ions by neutral atoms or molecules have been calculated by numerical integration of the classical equations of motion. The model used for the ion-neutral potential energy function consists of three terms: an r—4 attraction, an r—6 attraction, and an r—12 repulsion. The attractive terms are theoretically sound, but the repulsive term is empirical. Quantum effects have been ignored, but an approximate formula indicates at what point the classical calculations begin to fail in any particular case. The results should be of most use in the very low energy region where experimentation is difficult.
Molecular Structure of B10H12(CH3CN)2
Authors: van der Maas Reddy Josina , Lipscomb William N.
Published: January 2005

An x-ray diffraction study of single crystals of B10H12 (CH3CN)2 has yielded the positions of all atoms, including hydrogen atoms. The structure is regarded as a substitution derivative of the B10H14—2 structure having C2v symmetry, two bridge hydrogens and two BH2 groups. A B–N single bond replaces a B–H of each BH2 group and the acetonitrile residue is linear with normal bond distances, except for C–CH3=1.45 A in agreement with C–CH3=1.46 in acetonitrile itself.

The unit cell is monoclinic, of symmetry I2/c, and has parameters a=7.81, b=11.31, c=14.18, and β=96°52′. Final values of R=0.15 and r=0.12 were obtained, as described in the text.
Thermodynamic and Spectroscopic Study of Pyrrolidine. I. Thermodynamic Properties in the Solid, Liquid, and Vapor States
Authors: Hildenbrand D. L. , Sinke G. C. , McDonald R. A. , Kramer W. R. , Stull D. R.
Published: January 2005

The low-temperature heat capacity, heat of combustion, heat of vaporization, and vapor pressure of pyrrolidine have been measured. Information obtained from these measurements is as follows: the heat capacity of the solid from 14 to 215°K; the liquid heat capacity from 215 to 312°K; a heat of transition of 127 cal mole—1 at 207.14°K; a heat of fusion of 2053 cal mole—1 at the melting point, 215.31°K; the entropy of the liquid at 298.15°K, 48.78 cal mole—1 deg—1; the standard heat of formation from the elements at 298.15°K, —9.81 kcal mole—1; the heat of vaporization at 298.15°K, 8990 cal mole—1; and the vapor pressure, log10P(mm) = 6.88816 — 1157.40/(t+202.332). From a comparison of the calorimetric entropy of the ideal gas with statistically calculated values based upon newly obtained spectroscopic data, pyrrolidine vapor appears to have the indefinitely puckered cyclopentane type structure. Thermodynamic properties of the solid, liquid, and ideal gas have been tabulated at selected temperatures.
Thermodynamic and Spectroscopic Study of Pyrrolidine. II. Vibrational Spectra and Configuration
Authors: Evans J. C. , Wahr J. C.
Published: January 2005

The Raman spectrum of pyrrolidine liquid at several temperatures and the infrared spectra of pyrrolidine in the vapor, liquid, and solid states, in the 320–3500 cm—1 region and over the temperature range +150°C to —120°C have been recorded. Similar but less extensive studies were made on pyrrolidine N–D. Evidence for the presence of several configurational isomers in the liquid and solid states was obtained. A vibrational assignment, complete except for one degree of freedom, has been made and used to calculate the entropy of the ideal vapor. Comparison with the measured entropy has shown that pyrrolidine in the vapor is a free or an almost free pseudorotator.
Oscillator Strengths in the Far Ultraviolet. II. Oxygen Schumann-Runge Bands
Authors: Bethke George W.
Published: January 2005

Absolute integrated absorption intensities have been measured for the oxygen Schumann-Runge band system. From these data the total band system absorption oscillator strength was found to be between 0.00027 and 0.00031 while from the band strengths the electronic absorption oscillator strength was calculated to be 0.163±10%. The experimental method involved the photometric detection of pressure-broadened oxygen spectra from 1750 to 2000 A.
Forbidden Band Systems in Nitrogen. II. The a′1Σu−←X1Σg+ System in Absorption
Authors: Wilkinson P. G. , Mulliken R. S.
Published: January 2005

Four bands of the a′1Σu−←X1Σg+ system in nitrogen have been observed in absorption at high resolution in a path of 3.4 meteratmospheres, at 1444 A (1–0), 1414 A (2–0), 1358 A (4–0), and 1331 A (5–0). They consist of Q branches only (ΔJ=0). The observation of these bands, highly forbidden by the usual selection rules, is explainable by perturbations with the nearest 1IIu states lying between about 98 000 cm—1 and 109 000 cm—1 above the ground state.

The rotational analysis of each of the bands resulted in rotational constants and vibrational intervals for a′1Σu— which agree very well with those obtained from the emission system x1Σg−→a′1Σu−. The electronic energy (T00) of state a′1Σu— is now precisely located at 67738.18 cm—1 (8.398 ev); this value combined with other data gives also the following electronic energies (T00): w1Δu, 71697.68 cm—1 (8.889 ev); x1Σg—, 113210.98 cm—1 (14.036 ev); and y1IIg, 114165.18 cm—1 (14.154 ev). T00 of a′1Σu— is close to that of a 1IIg: 68951.21 cm—1 (8.548 ev).

The new energy for y1IIg is 0.339 ev lower than the minimum value deemed possible by Lofthus and Mulliken on the basis of an observed predissociation at v=0, J=10 of state y. That predissociation is now reinterpreted as most probably an accidental one resulting in the formation of 2P+4S atoms instead of 2D+2D atoms as formerly assumed.

The intensity distribution in the a′1Σu−←X1Σg+ system is found to be approximately proportional to J(J+1)(2J+1) exp—[B0″J(J+1)hc/kT], where B0″=1.9898 cm—1 and T=300°K, in agreement with theory.

From appearance pressures of the five forbidden systems of nitrogen now known in absorption, it is possible to estimate the transition probabilities. From these, together with a recent molecular beam determination of the mean lifetime of the state a1IIg, it is possible to estimate the lifetimes of the metastable states: A3Σu+, 2.6×10—2 sec, a′1Σu—, 4.0×10—2 sec. By comparison of the transition probability of the atmospheric oxygen bands (b1Σg+←X3Σu−) with that of the Vegard-Kaplan bands of nitrogen (A3Σu+←X1Σg+), together with the known lifetime of b1Σg+, the value 6.5×10—3 sec is found for the lifetime of A3Σu+, in fair agreement with the value given above.
Angular Dissymmetry of the Critical Opalescence in Liquid Mixtures
Authors: Debye P.
Published: January 2005

Visible light scattered by a one-component homogeneous liquid in the vicinity of its critical point or by a homogeneous mixture of two liquids in the vicinity of their critical mixing temperature shows angular dissymmetry which becomes the more pronounced the nearer the temperature comes to the critical temperature. It is shown how this dissymmetry can be used as a measure for the range of molecular forces in the case of ordinary molecules. In the case of polymer molecules, observation of the dissymmetry provides a method for measuring the size of polymer coils in a size range too small to be measured by the usual dissymmetry method applied to diluted solutions.
Dynamic Stability of Frozen Radicals. II. The Formal Theory of the Model
Authors: Jackson J. L.
Published: January 2005

In Part I, a model for frozen radical chain reactions of nitrogen atoms in a nitrogen molecule lattice was described. Here, a formal mathematical theory of these reactions is developed and applied. The results of the model are used to discuss the stability of frozen radical mixtures as a function of size. The theory also is used to obtain curves of free radical concentrations as a function of time, when radicals are produced by irradiation of the solid at low temperatures. The formulas obtained are compared with most recent experimental results.
Electronic Wave Functions for Polyatomic Molecules
Authors: Allen Leland C.
Published: January 2005

A one-electron basis set made from functions with exponential and Gaussian radial dependence is proposed for constructing many-electron, many-center, electronic wave functions. Appropriate mixtures of these two types may greatly simplify the evaluation of many-center, two electron integrals and in addition make possible an improved description of the molecular bond. Plane waves may also be added to the basis set thus making an application to solids appear feasible.
On the Velocity Distribution in a Chemically Reacting Gas
Authors: Present R. D.
Published: January 2005

The departure of the velocity distribution function from the Maxwellian form and the corresponding correction to the reaction-rate formula have been calculated for a gas undergoing a slow bimolecular reaction. Kinetic theory methods based on the Boltzmann transport equation have been used. This work differs from a previous calculation by Prigogine and Xhrouet in two respects: (1) the energy dependence of the reaction cross section is taken in a form that is consistent with the conventional simple collision theory (in the previous work this was not the case and the results are sensitive to this choice), and (2) a simplified derivation of the important formulas is given, in which we follow the original methods of Chapman based on the equations of change instead of the integral-equation techniques of Enskog. The calculations take into account the effect of the reaction in depleting the tail of the Maxwell distribution, but do not take into account the effects of the heat of reaction. It is found that when kT is one-fifth the activation energy, the reaction rate is 8% less than that predicted by the conventional simple collision theory.
On the Linear Phenomenological Equations. II. The Linear Statistical Mechanical Theory
Authors: Bearman Richard J.
Published: January 2005

The phenomenological equations, including inertial and viscous terms, are derived from statistical mechanical theory. The influence of the additional terms is evaluated with reference to their effect on the operational significance of the phenomenological coefficients and on the interpretation of diffusion data.
Variation of Appearance Potentials of Alkane Fragment Ions with the Repeller Voltage of the Mass Spectrometer Ion Source
Authors: Friedman L. , Long F. A. , Wolfsberg M.
Published: January 2005

The differences in the mass spectrometric appearance potentials for parent molecule ions and the ion fragments which are formed from the parent by hydrogen abstraction have been measured for propane, n-butane, and n-pentane as a function of the repeller voltage in the ion source. With pentane, the potential difference varies from close to zero for no repeller voltage to 1.1 volts for 0.5 volt repeller voltage or higher. There is a similar but smaller increase of 0.6 volt with n butane, while with propane the changes in appearance potentials are well within the experimental error. Of the various explanations considered, the most likely is that zero repeller voltage leads to relatively longer ion residence times in the source and that, as a result, some low-probability de-excitation processes have time to occur. This implies that appearance potentials which are obtained for this type of process with use of the usual repeller voltages can be considerably in excess of the minimum threshold energies.
C13 Splittings in Proton Magnetic Resonance Spectra. I. Hydrocarbons
Authors: Muller Norbert , Pritchard Donald E.
Published: January 2005

Indirect spin-spin couplings between protons and C13 nuclei have been measured for a number of hydrocarbons. The results are interpreted on the basis of a simple semiempirical equation relating the coupling constants with the amounts of s character of the carbon-atomic orbitals involved in the bonds. No evidence is found for a dependence of the coupling constants on supposed changes in ionic character of the bonds.

An equation is also presented relating the coupling constants and the C–H internuclear distances. This provides a new indirect means of evaluating C–H distances, with a reliability apparently at least comparable with that of methods in current use.
Statistical Thermodynamics of Polymer Solutions. II. Excluded Volume Effect and Second Virial Coefficient
Authors: Casassa Edward F.
Published: January 2005

A recently published theory of the second virial coefficient in polymer solutions is modified to take account of the fact that in a good solvent the mean dimensions of two interacting linear molecules are increased beyond random-flight size through both intermolecular and intramolecular mutual volume exclusion among chain segments. Since the model for a bimolecular cluster bears a formal resemblance to a cruciform branched chain, a method for calculating the dimensions of such polymers can be applied to the two-molecule problem. This treatment improves the agreement of calculated virial coefficients with experiment as compared with the simpler assumption, made in the original formulation of the theory, that each molecule of an interacting pair is expanded independently in consequence of intramolecular interactions alone.