bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal-Diffusion-Column Shape Factors for the Lennard-Jones (12–6) Potential
Authors: McInteer B. B. , Reisfeld M. J.
Published: January 2005

The theory of the hot-wire thermal-diffusion column as developed by Jones and Furry involves the shape factors h, kc, and kd, which are functions of the transport properties of the gas. The shape factors have been evaluated numerically for a gas whose molecules interact according to the Lennard-Jones (12–6) potential, given by V(r)=4ε[(σ/r)12−(σ/r)6]. The results are tabulated for a range of kT/ε from 0.8 to 30 for temperature ratios as great as 6 and for ratios of column radii up to 100. These values are more accurate than those previously computed for potentials varying as r—5 (Maxwellian) and for r—∞ (rigid spheres).

The values for the constants are found to give good agreement with experimental data on the system He3-He4.
On the Dynamical Theory of Diffusion in Crystals. V. Random-Walk Treatment of the Heat of Transport
Authors: Allnati Alan R. , Rice Stuart A.
Published: January 2005

The heat of transport in a crystalline medium is calculated from the flux of matter in a combined temperature and concentration gradient. The use of a random-walk model leads to the prediction that the heat of transport is exactly equal to the activation energy for motion. This prediction is in excellent agreement with the measurements of Patrick and Lawson of vacancy motion in AgBr. The dynamical interpretation of the theory presented is briefly discussed.
Infrared Spectra of Alkyldiboranes. III. 1,2-Dimethyl- and 1,2-Diethyldiboranes
Authors: Lehmann Walter J. , Wilson Charles O. , Shapiro I.
Published: January 2005

The infrared spectra of three isotopic variants of 1,2-dimethyldiborane—(CH3B10H2)2, (CH3BH2)2, (CH3BD2)2—and of five 1,2-diethyldiboranes—(C2H5B10H2)2, (C2H5BH2)2, (C2H5BD2)2, (C2D5BH2)2, (C2D5BD2)2—are reported and frequency assignments are made. 1,2-Dialkyldiboranes are very stable with respect to decomposition, but on prolonged standing rearrange to 1,1-dialkyldiboranes. Appearance of absorptions at ca 2100 and 1550 cm—1 is the first indication of the presence of 1,1-dialkyldiborane impurity. Although not conclusive, the evidence favors existence of predominantly cis configurations.
Microwave Spectrum, Structure, and Dipole Moment of Formyl Fluoride
Authors: LeBlanc Oliver H. , Laurie Victor W. , Gwinn William D.
Published: January 2005

The microwave spectra of several isotopic species of formyl fluoride have been investigated in the region 11–46 kMc. Both parallel and perpendicular transitions have been assigned. The effective rotational constants for HC12OF are (Mc) a=91153.6, b=11760.0, c=10396.8; for HC13OF, a=88475.3, b=11755.2, c=10357.3; for DC12OF, a=65090.1, b=11761.7, c=9941.7. From these constants the structural parameters are calculated to be rCF=1.341 A, rCO=1.183 A, rCH=1.100 A, ≰ FCO=122.7°, ≰ HCF≈108°, ≰ HCO≈129°. Measurements of the Stark effect lead to a value of 2.02±0.02 debyes for the dipole moment.
Paramagnetic-Resonance Absorption of Ions with Spin 5/2: Mn++ in Calcite
Authors: Kikuchi Chihiro , Matarrese L. M.
Published: January 2005

The theory of the paramagnetic-resonance absorption of ions with S=52 in crystalline fields of trigonal symmetry is presented. The case of manganous ions in calcite (CaCO3) is taken as an example. It is shown that the splitting of the fine-structure satellites into doublets first reported by Hurd, Sachs, and Hershberger [Phys. Rev. 93, 373 (1954)] can be accounted for by assuming that the manganous ions can occupy the two nonequivalent Ca++ sites at random. The maximum splitting was measured at X band and K band and found to be 19.3±0.5 gauss. The value computed from the theory, assuming an ionic model, is 23.8 gauss. In addition, five pairs of weak lines were found, each pair occurring midway between adjacent hyperfine groups. The origin of these lines is uncertain. The applicability of the present theory to Al2O3:Fe, a zero-field maser material, and to the photosensitive Fe+++ center in CdS is pointed out.
Valence-Bond Resonance Structures for a Triplet State
Authors: McLachlan A. D.
Published: January 2005

Pauling's rules for calculating the singlet ground state of a molecule by the valence-bond method are extended to deal with triplet states.
Continuum-Model Treatment of Long-Range Intermolecular Forces. I. Pure Substances
Authors: Linder Bruno
Published: January 2005

A theory is presented whereby the long-range intermolecular forces, including the London dispersion forces, of pure nonelectrolytes may be calculated from optical and dielectric data. The method is based on the continuum-model approach, where one molecule is treated explicitly while the others are replaced by a medium of uniform dielectric. The classical and quantum-mechanical oscillators are used as working models and expressions are derived for computing the cohesive energy appropriate for both types of oscillators. The potential energy based on the quantum-mechanical oscillator is calculated for a number of liquids and is shown to be in fair agreement with the experimental energy of vaporization.
Molecular Structure of Lithium Chloride Dimer. Thermodynamic Functions of Li2X2 (X = Cl, Br, I)
Authors: Bauer S. H. , Ino Tadashi , Porter Richard F.
Published: January 2005

Our electron diffraction apparatus has been suitably modified for the study of vapors at high temperatures. A furnace and auxiliary power supply have been constructed, and a serviceable design for a sample container, with a nozzle, has been developed.

Data on two systems have been obtained. The diffraction pattern produced by cesium chloride vapor is that expected for a diatomic molecule; the interatomic distance determined in this experiment checks with the microwave value. In lithium chloride vapor, dimers predominate. Their structure is diamond shape (planar) with Li–Cl=2.23±0.03 ACl–Cl=3.61±0.03 A∠ClLiCl=108∘±4∘.

The dimensions of the lithium halide dimers are compared and their thermodynamic functions tabulated.
Infrared Spectra of Some Unstable Isomers of N2O4 and N2O3
Authors: Hisatsune I. C. , Devlin J. P. , Wada Yasuo
Published: January 2005

The temperature dependence of the infrared spectra of N2O4 and N2O3 in the solid phase at liquid-nitrogen temperatures has been investigated. From these spectra of both 14N and 15N isotopic molecules, absorption bands which may be assigned to unstable isomers of these nitrogen oxides have been identified. A reasonable interpretation of these absorption bands can be made by assuming the existence of two unstable forms of N2O4 and one of N2O3.
CN Stretching Bands in the Raman Spectra of Some Group Ib and Group IIb Complex Cyanides
Authors: Chantry G. W. , Plane R. A.
Published: January 2005

The Raman spectra of solutions containing cuprous, argentous, and mercuric ions together with cyanide ions indicate the presence of the di-, tri-, and tetra-coordinated complexes. The spectra from solutions containing zinc and cadmium ions, respectively, with cyanide ions could be investigated in concentrations where only the tetra-coordinated complex is observed.
Collisional Deactivation of Vibrationally Excited sec-Butyl-d1 Radicals Produced by Chemical Activation
Authors: Harrington R. E. , Rabinovitch B. S. , Hoare M. R.
Published: January 2005

Vibrationally excited sec-butyl-d1 radicals have been produced by addition of D atoms to cis-butene-2. The radicals, which have a narrow range of internal energy E, undergo either collisional stabilization (S) or decomposition (D) with specific rate kE. The ratio D/S has been studied as a function of pressure down to 0.005 mm at 25°. Using calculated values of kE, information is obtained about vibrational transitions upon collision of excited radicals with butene molecules, under different assumptions regarding the form of the transition probability function. It is shown that in these cases the average energy transferred is at least 8.5 kcal/mole, and quite probably much more, which supports the conventional Lindemann collisional activation-deactivation assumption of strong collisions in this case.
Secondary Positive Ion-Emission from Platinum
Authors: Bradley R. C. , Arking A. , Beers D. S.
Published: January 2005

Mass analysis of the secondary particles ejected from Pt surfaces by inert gas ion bombardment or by heating revealed species characteristic of the base metal, of certain bulk and surface impurities, and of the bombarding beam (so-called ``reflected'' ions). The Pt+ ions seemed to come directly from the substrate rather than from surface compounds. Their yield increased with temperature, bombarding ion energy, and bombarding ion mass. The ratio of sputtered Pt ions to sputtered neutrals is estimated to be of the order of 1 to 1000 at room temperature. The kinetics of the formation and desorption of a certain surface compound [possibly Pt(CO)2] was studied by secondary ion analysis. The compound formed spontaneously on the surface from the background gas in the instrument (CO at 10—8 mm Hg). Its formation rate was greatly enhanced by inert gas ion bombardment. It desorbed readily at 1000°C with an activation energy of 0.74±0.05 ev. The ``reflected'' ions appeared to be sputtered rather than reflected. Their energy was always extremely low (<1 ev) and the dependence of their yield on ambient gas pressure and target temperature is consistent with the notion that they originated from inert gas atoms trapped in the surface layers.
Streaming Birefringence of Rigid Macromolecules in General Two-Dimensional Laminar Flow
Authors: Wayland Harold
Published: January 2005

Quantitative expressions for the direction of the angle of isocline and for the amount of birefringence due to a dilute solution of rigid macromolecules in a general two-dimensional laminar flow are derived. If E is the principal strain rate and Λ0 is the angle between the streamline direction and the direction of the principal strain rate axis, the angle of isocline, measured from the first principal strain rate axis is χ=−(Esin2Λ0/6D){1−(E2/27D2)[sin22Λ0+(24b2/35)]+···],where b=[(a12—a22) / (a12+a22)] is a shape factor for an ellipsoid of revolution of semimajor axis a1 and semiminor axis a2 and D is the rotary diffusion constant for this ellipsoid. The amount of birefringence is Δn=(4π/15)(cGEb/nD) {1−(E2/18D2)[sin22Λ0+(6b2/35)]+···},where n is the mean index of refraction of the solution, c the volume concentration of the macromolecules, and G=g1—g2 is the optical anisotropy of the ellipsoids.

It is seen that if the principal strain rate is not at 45° to the streamline at the point of observation, this will make itself felt in the position of the angle of isocline before it influences the amount of birefringence.

Detailed expressions for the effect of polydispersity show that there is a simple relationship between the birefringence and angle of isocline measured in Couette flow and these quantities measured in general two-dimensional flow only if (a) Λ0=45° in the general flow or (b) the birefringence and angle of isocline values are linear with strain rate.
Dissociation of Methyl Bromide by Nuclear Isomeric Transition of 4.4-hr Br80m
Authors: Wexler S. , Anderson G. R.
Published: January 2005

The pattern of positively charged fragments from methyl bromide as a result of isomeric transition of 4.4-hr Br80m has been measured by mass spectrometric techniques. A peaked distribution of charge states of atomic bromine ranging from Br+1 to Br+13 was observed, the most probable being Br+7. The finding of singly, doubly, and triply charged carbon-containing fragments gives evidence that the CH3Br80 daughter ion breaks apart by Coulombic repulsion of redistributed charges following internal conversion and subsequent Auger electron transitions. Multiply charged polyatomic species produced by the nuclear transition are unstable.
Light-Induced cis-trans Isomerization of Nitrous Acid Formed by Photolysis of Hydrazoic Acid and Oxygen in Solid Nitrogen
Authors: Baldeschwieler John D. , Pimentel George C.
Published: January 2005

Photolysis of hydrazoic acid in solid nitrogen at 20°K with oxygen present yields both cis- and trans- nitrous acid. The identification is based on infrared detection of features of the isotopically substituted species HONO, DONO, and HO18NO18. The nitrous acid probably results from the reaction of imidogen with oxygen NH+O2=HONO.Isomerization of nitrous acid occurs in the matrix at 20°K under the influence of irradiation. Ultraviolet radiation causes the trans- to cis- reaction, probably by electronic excitation to give a random mixture of the two forms. Near-infrared radiation reverses the reaction but the role of the radiation is not known. Bulk heating of the sample is not involved and a broad range of near-infrared frequencies is effective. No isomerization of DONO could be detected and HO18NO18 seemed to isomerize more slowly than did HONO. Only speculative interpretations of this phenomenon can be made at this time.
Metal-Metal Bonding in Dicobalt Hexacarbonyl Diphenylacetylene
Authors: Brown David A.
Published: January 2005

The nature of the bonding between the two cobalt atoms in dicobalt hexacarbonyl diphenylacetylene is discussed in terms of simple molecular-orbital theory. It is shown that, in addition to bonding via the π orbitals of the acetylene residue, it is essential to consider direct overlap between the 4p orbitals of the cobalt atoms. Master formulas and numerical tables are derived for the integrals S(4pσ4pσ), S(4pπ4pπ).
New Solution of the Ising Problem for a Rectangular Lattice
Authors: Hurst C. A. , Green H. S.
Published: January 2005

A new solution of the Ising problem for a rectangular lattice is derived from first principles. The solution, which is obtained algebraically, can be presented in a determinantal form different from though related to that found by Kac and Ward. By connecting the algebraic approach with the combinatorial solution, the latter is freed from dependence on topological conjectures. The new solution is considered to be fundamentally simpler than the others.
Structure in Ionic Solutions. IV
Authors: Brady George W.
Published: January 2005

X-ray measurements in ErCl3 and ErI3 solutions indicate that there is a firmly held octahedral arrangement of H2O molecules around the Er3+ ion. In addition, there are present Er3+–Cl2— and Er3+–I2— ion-pair complexes. Finally there is a large amount of order introduced into the structure by the presence of the ions, with evidence for an ``icelike'' quasi-lattice.
Paramagnetic Relaxation in Solutions of VO++
Authors: Rogers R. N. , Pake G. E.
Published: January 2005

The ESR spectrum of vanadyl ion in solutions has the interesting feature that the linewidths of the individual hyperfine components depend on the nuclear spin orientation, mI. We have determined that the origin of the effect is the mechanism proposed by H. M. McConnell, namely, the existence of a ``microcrystal'' about the VO++ ion which gives rise to anisotropies in the g tensor and hyperfine interaction. By comparing the results of linewidth measurements made at 9.25 kMc and at 24.3 kMc with the results of calculations made by D. Kivelson, we were able to conclude the validity of the microcrystallite model.
Solubility of Hydrogen and Deuterium in Liquid Argon
Authors: Volk H. , Halsey G. D.
Published: January 2005

The solubility of hydrogen and deuterium in liquid argon at pressures from 10 to 100 atm is reported. Solubility isotherms have been measured between 87° and 140°K for hydrogen and between 87° and 120°K for deuterium. The dependence of Henry's constant on temperature, pressure, and concentration, the heats of solution, the partial molar volume of hydrogen in liquid argon, and the second virial coefficients of hydrogen and deuterium in the liquid solution are reported. The increase in the solubility of deuterium over hydrogen is 21.3%, 20.2%, and 18.5%, respectively, at 87, 100, and 120°K. This isotope effect is discussed as a quantum correction to the free volume. Comparison between theory and experiment indicates that the LJD free volume is too large by approximately a factor of five.
Transport Processes in Liquid Alloys. II. The Electrical Force on an Ion
Authors: Mangelsdorf Paul C.
Published: January 2005

The electrolytic migration velocities of impurity ions in liquid metals suggest the existence of strong net electrical forces on these ions, although other mechanisms are possible. On the basis of a detailed model of a liquid metal the early theory of Skaupy is revived and revised. In dilute solution a total electrical force, proportional to the conductivity increment produced by a solute, is exerted on the solute and on nearby solvent when the electric field is applied. The part of the force on the solute ion may be opposed to the part on the solvent. Implications for the resistivity of liquid alloys are discussed, including a possible effect in very dilute solutions when the solute ions are further apart than one mean free path. The effective number of free electrons in pure liquid mercury is provisionally estimated to be 0.3 per atom.
Polarized Absorption and Fluorescence Spectra of 2,6-Dimethylnaphthalene at Different Temperatures
Authors: Zmerli Adnan , Poulet Henri
Published: January 2005

2,6-Dimethylnaphthalene melted between two silica disks crystallizes parallel to its cleavage plane σab. The polarized absorption spectra obtained at 300°K, 77°K, 20°K, and 4°K show no variation in the relative intensities of the a and b spectra, suggesting that there is no change of crystal phase between 300°K and 4°K. At 4°K three vibrational progressions were found in the a spectrum and only two in the b spectrum. The first bands of the strongest a and b progressions, i.e., the bands at 30 740 cm—1 and 30 675 cm—1, respectively, are interpreted as transitions to the exciton levels. The weak progression starting at 30 650 cm—1 appears in both polarization directions. The 30 634 cm—1 series, which is also weak, is a polarized. The origin of these weak bands is discussed. The polarized fluorescence spectra have been obtained at 20°K and interpreted. Possible locations of the c exciton transition are mentioned. The comparison of these experimental results and the theoretical predictions leads to the conclusion that the dipolar moment of the first transition of 2,6-dimethylnaphthalene is close to the short axis of the naphthalene ring.
Axial Crystal Fields in the Ionic Model
Authors: Piper T. S. , Carlin R. L.
Published: January 2005

Expressions for the axial components of crystal fields of tetragonal, trigonal, and cylindrical symmetry are developed in terms of the parameters Ds and Dt. These parameters are calculated in the ionic model using Hartree-Fock 3d radial wave functions. The calculated parameters are compared to experimental values obtained from the spectra of V(III) in Al2O3 and Co(II) in CoO. Tentative assignments of the bands in the spectrum of (C5H5)2Ni are made.
Inter- and Intra-Atomic Correlation Energies and Theory of Core-Polarization
Authors: Sinanoğlu Oktay
Published: January 2005

Atomic and molecular energies depend strongly on the correlation in the motions of electrons. Their complexity necessitates the treatment of a chemical system in terms of small groups of electrons and their interactions, but this must be done in a way consistent with the exclusion principle. To this end, a nondegenerate many-electron system is treated here by a generalized second-order perturbation method based on the classification of all the Slater determinants formed from a complete one-electron basis set. The correlation energy of the system is broken down into the energies of pairs of electrons including exchange. Also some nonpairwise additive terms arise which represent the effect of the other electrons on the energy of a correlating pair because of the Pauli exclusion principle. All energy components are written in approximate but closed forms involving only the initially occupied H.F. orbitals. Then each term acquires a simple physical interpretation and becomes adoptable for semiempirical usage. The treatment is applied in detail to two particular problems: (a) The correlation energy between an outer electron in any excited state and the core electrons, e.g., in the Li atom, is represented by a potential acting on the outer one. This potential can be regarded as the mean square fluctuation of the Hartree-Fock potential of the core, and applies even when the outer electron penetrates into the core. The magnitudes of some of the correlation effects are calculated for Li. (b) Starting from a complete one-electron basis set of SCF MO's, the energy of a molecule is separated into those of groups of electrons and of intra-molecular dispersion forces acting between the groups. The assumptions that are usually made in discussing dispersion forces at such short distances are then removed and generally applicable formulas are given. Some three or more electron-correlation effects and limitations in the use of ``many electron group functions'' for overlapping systems are also discussed.
Cl35 NMR Contact Shifts in Aqueous Cobaltous Chloride Solutions
Authors: Chesnut D. B.
Published: January 2005

The NMR shifts of the Cl35 nucleus in aqueous cobaltous chloride solutions have been measured relative to the free chloride ion. The displacement of the Cl35 resonance to lower applied fields at constant frequency becomes larger with both increasing cobaltous and chloride ion concentrations. The effect of added non-complexing salt indicates the significant role hydration plays in the complex equilibria taking place. The magnitudes of the observed shifts point to an isotropic electron-spin-nuclear-spin contact interaction in the complexed cobaltous chloride.
Cuprous Halide Films on Alkali Halide Crystals
Authors: Kraemer L. M.
Published: January 2005

Films of cuprous halides were formed by evaporation and condensation in a vacuum onto substrates of alkali halide crystals at room temperature. They were annealed for 15 min periods at temperatures between 60° and 150°C. Optical absorption spectra indicate that the annealing causes diffusion of CuCl and CuBr into KCl and KBr, but not into KI or NaCl, and of CuI into RbI, but not into KCl, KBr, KI, or NaCl. An interstitial mechanism for diffusion is consistent with the data but is not sufficient to account for the behavior of CuI.
Theory of the Diffuse Double Layer
Authors: Stillinger Frank H. , Kirkwood John G.
Published: January 2005

The charge moment expansion for potentials of mean force acting between the ions of an electrolyte is reviewed in a form applicable to surface phases. An integral equation is in this manner derived for approximate determination of the average charge distribution near a planar electrode. The solution of the linearized equation is constructed for an electrolyte consisting of charged hard spheres suspended in a dielectric continuum. For very dilute solutions, the predictions of the linearized Poisson-Boltzmann equation are verified; at higher concentrations, the average space charge in the neighborhood of the electrode tends to alternate in sign as a result of local latticelike ion arrangement imposed effectively by short range ion repulsions. Predicted values of the ζ potential relative to those of the linear Poisson-Boltzmann theory are reported.
Statistical Mechanics of Transport Processes. XIV. Linear Relations in Multicomponent Systems
Authors: Kirkwood John G. , Fitts Donald D.
Published: January 2005

A classical treatment of the time dependence of a phase-space distribution function for a system near equilibrium is presented. The nonequilibrium distribution function is expressed as a stationary zero-order function plus a perturbation term and is used to obtain the diffusion and heat fluxes by averaging the appropriate dynamical variables. When only terms linear in the gradients of the local temperature, the chemical potentials, and the velocity of the local centers of mass are retained, the usual linear relations result and explicit expressions for the phenomenological coefficients are obtained. These expressions agree with the results of Mori and of Green and are shown to obey the Onsager reciprocal relations.
Ensemble Method in the Theory of Irreversibility
Authors: Zwanzig Robert
Published: January 2005

We describe a new formulation of methods introduced in the theory of irreversibility by Van Hove and Prigogine, with the purpose of making their ideas easier to understand and to apply. The main tool in this reformulation is the use of projection operators in the Hilbert space of Gibbsian ensemble densities. Projection operators are used to separate an ensemble density into a ``relevant'' part, needed for the calculation of mean values of specified observables, and the remaining ``irrelevant'' part. The relevant part is shown to satisfy a kinetic equation which is a generalization of Van Hove's ``master equation to general order.'' Diagram summation methods are not used. The formalism is illustrated by a new derivation of the Prigogine-Brout master equation for a classical weakly interacting system.
Some Further Remarks on the Coefficient of Self-Diffusion in Simple Dense Fluids
Authors: Rice Stuart A.
Published: January 2005

The self-diffusion coefficient in a simple dense fluid is calculated from the autocorrelation function of the momenta. If the randomization of momentum is rapid, the resultant diffusion coefficient differs from that first suggested by Kirkwood, Buff and Green by only (2/π)½. The physical basis of this result is considered. A very simple method of demonstrating the necessity for molecular correlations in the approach to equilibrium is discussed.
Studies in Molecular Dynamics. II. Behavior of a Small Number of Elastic Spheres
Authors: Alder B. J. , Wainwright T. E.
Published: January 2005

The equation of state and the collision rate for systems ranging in size from four to 500 particles are described. The dependence of the results on the number of particles is qualitatively discussed and in this way insight is gained as to what is required of more accurate analytical theories. By comparing the results to various analytical theories now available their region of validity is established. The number of particles necessary at various densities to obtain a quantitative description of the equilibrium properties is delineated. Whether a first-order phase transition exists for hard spheres remains open until larger systems are investigated.
Surface Specific Heat of an Isotropic Solid at Low Temperatures
Authors: Dupuis Marc , Mazo Robert , Onsager Lars
Published: January 2005

The effect of realistic boundary conditions on the computation of the specific heat of an isotropic solid at low temperatures is investigated. Two cases are considered: the surface free of stress and the surface rigidly clamped. The first of these is the one of physical interest. For both cases a term in the specific heat arises which is proportional to the surface area and to T2 and appreciably higher than Montroll's result in the case of the free solid. The effect of approximations introduced during the computation is estimated. Available experimental data are not adequate for a critical test of the theory.
Classical and Quantum Mechanical Hypervirial Theorems
Authors: Hirschfelder Joseph O.
Published: January 2005

If W is a function of the coordinates and momenta, then in classical mechanics the time average of the Poisson bracket (H, W) is zero. In quantum mechanics it follows from the Heisenberg equation of motion that the expectation value of (WH — HW) for any wave function, corresponding to a stationary energy state of the system, is zero. For each selection of W there is a dynamical relationship, in a time-average or space-average sense, which the system must obey. Two classes of W's are considered in detail: W as a function only of the coordinates, and W as a function of the coordinates times the first power of a momentum. For the first class, neither the classical mechanical nor the quantum mechanical results provide useful information. The usual virial theorem of Clausius is a special case of the second class of relations. The classical treatment should be useful for the determination of the equation of state of liquids. The use of the quantum-mechanical relations for determining the constants in an approximate wave function is discussed.
On Temporal Evolution of Isolated Dynamical Systems
Authors: Golden S. , Longuet-Higgins H. C.
Published: January 2005

It is shown that if 〈 A (t) 〉 is the expectation value of a real observable A at time t, then for a finite closed dynamical system 〈 A (t) 〉 can converge to a limit as t→ ∞ only if 〈 A (t) 〉 is altogether independent of t. This conclusion is unaffected by time-smoothing or coarse-graining. On the other hand, for an infinite system whose energy levels form a purely continuous spectrum, 〈 A (t) 〉 tends to a limit as t→ ∞ under very general conditions. This conclusion does not depend on the introduction of either time-smoothing or coarse-graining.
Microwave Spectrum, Structure, and Dipole Moment of Propane
Authors: Lide David R.
Published: January 2005

The microwave spectrum of ordinary propane and five isotopic species have been measured and analyzed. The rotational constants of C3H8 are 29 207.36, 8446.07, and 7458.98 Mc, and the dipole moment is 0.083±0.001D. In its equilibrium configuration the molecule has C2v symmetry, with both CH3 groups staggered with respect to the CH2 group. The complete structure has been determined by the substitution method. Important parameters are: r(CC)=1.526±0.002 A, ≰CCC=112.4°±0.2°; in the CH2 group, r(CH)=1.096±0.002 A, ≰HCH=106.1°±0.2°; in the CH3 groups, r(CH)=1.091±0.010 A, ≰HCH=107.7°±1.0°. The influence of zero-point effects on the structure determination is discussed; these are found to be particularly bad for the CH3 group, probably because of its large vibrational amplitude.
Spectrum of ReF6
Authors: Eisenstein J. C.
Published: January 2005

The value of the spin-orbit coupling constant, ζ, for Re6+ in ReF6 is discussed in this paper. Moffitt et al. have tentatively assigned a value 3500 cm-1 to ζ for the series of compounds from ReF6 to PtF6. However, a detailed analysis of the OsF6 and IrF6 spectra indicates that ζ has values near 3200 and 3700 cm-1 for these two compounds. Since ζ increase in the sequence Re, Os, Ir, it is probably smaller than 3000 cm-1 in ReF6. If one assumes that there is a Jahn-Teller distortion of the fluorine octahedron, the optical absorption data on ReF6 can be reconciled with this smaller value of ζ.
Approximate Electronic Energy Surfaces from Cuspless Wave Functions
Authors: Wulfman Carl E.
Published: January 2005

The eigenfunctions of a molecular Hamiltonian in which all Coulomb potentials have been replaced by Hooke's law potentials are easily determined. Their electronic parts are essentially single-particle single-center harmonic oscillator, or Gaussian wave functions originating at the center of nuclear charge. An investigation is made to determine the feasibility of using these cuspless base functions in variational calculations of relative molecular electronic energies. It is found that:

A. Addition of Coulombic or delta-function singularities to the Hooke's law potentials leads to the formation of rigid molecular systems.

B. The Coulomb potentials in 21–26 electron triatomics can be treated as a perturbation upon quadratic potentials.

In agreement with experiment it is noted that:

C. Approximately homonuclear (i.e., nonhydride) 8-, 20-, and 40-electron polyatomics are configurationally unstable.

D. The molecules CO2+, CO2, N2O, NCO—, BO2—, N3—, and NO2+ should all be linear.

E. The molecules NO2—, O3, FNO, F2O, and a number of excited states of the molecules (D) should all be nonlinear.

F. The stable form of nitrous oxide should be N–N–O rather than N–O–N.

A number of general features of the treatment are discussed and several of its limitations are pointed out. A tabulation of coefficients required in Clebsch-Gordan expansions of products of Hermite polynomials is given.
Electron Spin Resonance of an Irradiated Single Crystal of N-Acetylglycine
Authors: Miyagawa Ichiro , Kurita Yukio , Gordy Walter
Published: January 2005

Electron spin resonance absorption of an irradiated single crystal of N-acetylglycine was observed at room temperature at 9 kMc and 12 kMc. From the analysis of the anisotropy in the spectroscopic splitting factor and in the nuclear hyperfine interaction constant, a chemical structure[Complex chemical formula]is deduced for the free radical. The C–H bond is in the NCC plane and approximately along the bisector of the NCC angle. The unpaired electron spin density is essentially in a π orbital, about 72% of which is the p orbital of the CH carbon directed perpendicular to the NCC plane.
Infrared Absorption Spectrum of NdCl3
Authors: Varsanyi F. , Dieke G. H.
Published: January 2005

The infrared absorption spectrum of NdCl3 is obtained under high resolution which show the transitions from the ground state to 4I13/2 and 4I15/2 the latter of which was hitherto unknown. The crystals were 5% and 50% NdCl3 in LaCl3 and the higher Nd concentration shows a decided frequency shift of the lines.
Physical Properties of Isotopically Substituted Classical Fluids
Authors: Steele W. A.
Published: January 2005

The observed differences in physical properties between isotopically substituted classical fluids are treated in terms of the theorem of corresponding states. It is shown that these differences are at least partially due to changes in the intermolecular potential energies of interaction. When the potential function of an isotopically substituted molecule is conformal with that of the unsubstituted molecule, the differences in the physical properties of the fluids can be quantitatively related to the differences in the depth and spatial extension of the potential functions, and to the changes in the internal degrees of freedom of the molecules. It is shown that the measured properties of perdeutero benzene-benzene and perdeutero cyclohexane-cyclohexane are consistent with these equations, and that the values of the parameters chosen to fit the theory to the data are reasonable. The limits of applicability of this treatment and its possible extension to less simple systems are discussed.
Ultraviolet and Structural Studies of Polythionates
Authors: Golding R. M.
Published: January 2005

The ultraviolet spectral results of the polythionates are discussed in light of various available theoretical approaches in evaluating inorganic complex spectral intensities and band positions. A semiempirical approach shows that the oscillator strengths of the polythionate electronic spectra are related to the π orbitals of the sulfur chain.
Infrared Spectra of Complexes of NO2F with BF3, PF5 and SbF5
Authors: Cook Denys , Kuhn Stephen J. , Olah George A.
Published: January 2005

The infrared spectra of complexes of NO2F with BF3, PF5, and SbF5 have been studied. In each case bands at about 2360 cm—1 were recorded and have been attributed to the nitronium ion NO2+. Bands consistent with a complex anion of the form MFn+1— have been observed, though with less accuracy. It is considered correct to designate these complexes as NO2+BF4—, NO2+PF6—, and NO2+SbF6—.
Generation of Free Carriers in Photoconducting Anthracene. I
Authors: Moore W. , Silver M.
Published: January 2005

The source of free carriers in photoconducting anthracene was determined from an investigation of the spatial distribution of trapped electrons. Free carriers are generated in the bulk in addition to electrons being injected into the anthracene at the negative electrode. The bulk generated carriers cannot come from an intrinsic process which simultaneously yields a free electron and a free hole. A tentative extrinsic model for the generation of free carriers is proposed in which electrons are injected at the negative electrode, free holes and trapped electrons are generated by the incident radiation in the bulk at impurities or other defects, and free holes are generated by the incident radiation at the positive illuminated electrode. On the basis of these results, one concludes that anthracene is an extrinsic rather than an intrinsic photoconductor.
Statistical Mechanics of Molecular Ions
Authors: Varney Robert N.
Published: January 2005

The N4+ ion is shown to be able to be in equilibrium against dissociation into N2+ and N2 under specified experimental conditions only if it possesses a considerable degree of vibrational excitation. The A2+ ion, lacking the numbers of modes of vibrational freedom possessed by the N4+, is therefore unstable under the same conditions. It would become stable in much weaker electric fields and simultaneously higher pressures. Experimentally, the A2+ ion is known to exist in contradiction to this prediction, but theoretical and experimental evidence is advanced that it is metastable and subject to dissociation with sufficient numbers of collisions in the gas.
Helium Atom Wave Functions from Slater Orbitals of Nonintegral Principal Quantum Number
Authors: Snyder Lawrence C.
Published: January 2005

Slater orbitals of nonintegral principal quantum number have been used to construct a He ground-state wave function of the form Ψ=c1(ns,n′s)+c2(n′′p)2+c3(n′′′d)2+c4(n′′′′f)2.The variation method has been employed to determine the five orbital exponents, the five principal quantum numbers n, and the four linear coefficients. The minimized energy is 0.0058 a.u. above the nonrelativistic limit of —2.9037 a.u. computed by Pekeris. This may be compared with a difference of 0.0063 a.u. obtained by Taylor and Parr upon minimizing the energy of the same wave function constrained to have integral principal quantum numbers.
First-Order Phase Transitions of Six Normal Paraffins at Elevated Pressures
Authors: Nelson R. R. , Webb W. , Dixon J. A.
Published: January 2005

First order phase transitions were investigated for n-nonane, n-dodecane, n-tridecane, n-pentadecane, n-octadecane, and n-tetracosane, at pressures up to 10 kilobars and temperatures up to 135°C. By a modification of standard piezometric techniques, phase transition pressures, as well as the associated isothermal isobaric volume changes were determined at approximately 25°C intervals. Correlations established between the melting temperatures and the specific volume changes associated with phase transitions and the n-paraffin chain lengths show a strong dependence upon whether the n-paraffin is of odd or even species. This dependence becomes more pronounced at higher pressures. The specific volume, enthalpy, and entropy changes showed no dependence upon chain length at the same melting temperature.
Vapor Pressures and Related Thermodynamic Properties of the Isotopic Nitric Oxide Molecules
Authors: Bigeleisen Jacob
Published: January 2005

The large differences in thermodynamic properties of the isotopic NO molecules are interpreted in terms of the known structure of interacting dimers. It is shown that structural considerations alone suffice to calculate the relative O18 to N15 isotope effects on vapor pressure, heats of vaporization, and triple points. The calculated relative quantities are in excellent agreement with experiment. The properties of N15O18 are shown to be completely determined by those of N14O16, N15O16, and N14O18. The absolute value of the vapor pressure ratio of N14O16/N15O16 is calculated from spectral data in good agreement with experiment.
Proton Magnetic Resonance Study of Barium Bromate Monohydrate
Authors: Silvidi A. A. , McGrath J. W.
Published: January 2005

The proton magnetic resonance absorption spectrum of barium bromate monohydrate was obtained using a Pound-Watkins spectrometer. Results indicate that there is only one orientation of the water molecule in the crystal. The p—p distance is 1.61±0.01 A and direction angles of the p—p vector are α0=30°, β0=95°, and γ0=122°. The experimental errors in these angles were ±3°. Apparently the water molecule is oriented so as to form the complex, OII Br——H–O–H——OII Br, where OBr are neighboring bromate oxygens. Results obtained for barium chlorate monohydrate were consistent with those for barium bromate monohydrate.
Compression of Flexible Chain Molecules in Solution
Authors: Simha Robert , Zakin J. L.
Published: January 2005

The compression of coiling molecules in good solvents at finite concentrations has been previously treated. However, the expressions were evaluated earlier by means of an expansion in the effective pressure acting on a coil. They are now presented in a form appropriate to include the range of reduced concentrations c/c0≥1. As an example volume ratios for polystyrene solutions in toluene are computed. They depend only slightly on molecular weight and amount to a reduction of about 30% in the most probable encompassed volume, at c/c0=1.
Nuclear Magnetic Resonance Spectra of the ABX3 Type: Field Dependence and Relative Signs of Spin-Spin Coupling Constants
Authors: Kowalewski Valdemar J. , deKowalewski Dora G.
Published: January 2005

The ABX3 spin system is studied as a function of applied magnetic field. A method for the determination of the relative signs of JAX and JBX, together with the relative chemical shifts and coupling constants is described. The results are applied to the cis crotonic acid, the trans crotonic acid, its methyl ester, and N-methylformamide. In the latter case it is shown that the relative chemical shift of the A and B protons can be estimated from the field behavior of the X3 group of lines.
Molecular Orbital Treatment of Hydrogen with Central Potentials and Modified Boundary Conditions
Authors: Peek James M. , Lassettre Edwin N.
Published: January 2005

A model is proposed for a homonuclear diatomic molecule in which each electron is treated as moving in the field which would prevail for an isolated atom but with boundary conditions which require that either the one electron eigenfunction, or its normal derivative, vanishes along a plane perpendicular to the line of centers and passing through the midpoint. The model is tested by applying it to molecular hydrogen. The assumed potential is compared to that computed from a Heitler-London function, using a suggestion of Slater, and the energy of the ground state of hydrogen is computed as a function of internuclear distance. Employing the model throughout (i.e., without averaging the exact Hamiltonian) a dissociation energy of 5.65 ev is obtained and an equilibrium internuclear distance of 1.7 a.u. is predicted.
Relation between the Proton Hyperfine Interaction and the C13–H1 Spin-Spin Coupling in Free Radicals
Authors: Bernheim R. A. , Das T. P.
Published: January 2005

It is shown that the C13–H1 spin-spin coupling constant J(C13–H1) and the proton hyperfine constant Q(H1) in a free radical can be considered as interdependent, and that they both can be estimated by calculating the perturbation produced in the electronic wave functions by the magnetic moment of the proton. For a C–H fragment with an unpaired π electron on the carbon atom an approximate relation is established between Q(H1) and J(C13–H1). Using the experimental value of J(C13–H1) for the benzene molecule, Q(H1) is found to have a negative sign and order of magnitude agreement with experiment.
Electron Spin Resonance Line Shape of a Polycrystalline CH Radical
Authors: Lefebvre Roland
Published: January 2005

A formula is derived for the electron spin resonance line shape of a polycrystalline sample containing the CH π-electron radical. The assumption is made in this derivation that the spectrum of the radical in a specific orientation is made up of Gaussians. The line shapes are calculated at the X, K, and J bands, and shown to be rather different for a sufficiently small component line width.
Nuclear Spin Conservation in Ortho-Para Hydrogen Conversion
Authors: Britton Doyle , Hugus Z Z.
Published: January 2005

The details of statistics of the nuclear spin states in the ortho-para hydrogen conversion by hydrogen atoms are considered. It is shown that the observed rate of conversion is 5/6 the rate of formation of the transition state if H3 is linear. The factor is 8/9 is H3 if an equilateral triangle.
Proton Spin Coupling by Pi Electrons
Authors: Karplus Martin
Published: January 2005

A theoretical formulation is developed for the pi-electron contribution, AHH′(π), to the spin coupling between pairs of protons in hydrocarbon molecules. By means of the correspondence between the σ—π interaction in unsaturated molecules and related free radicals, the proton spin coupling is expressed in terms of hyperfine constants and triplet state energies. With known values for these quantities, AHH′(π) is found to be in agreement with experimental measurements available for molecules in which the pi electrons are expected to dominate the coupling. Of particular interest are the large couplings (1.3–8 cps) calculated for certain systems with protons separated by three or four carbon atoms. Also absolute signs are predicted by the theory, with AHH′(π) equal to —6.7 cps for allene and +7.8 cps for butatriene.
Self-Diffusion of Nearly Spherical Molecules. Neopentane and Tetramethyl Silane
Authors: Douglass Dean C. , McCall David W. , Anderson Ernest W.
Published: January 2005

Self-diffusion coefficients have been measured for neopentane and tetramethyl silane by means of the nuclear magnetic resonance spin-echo technique. Both pressure and temperature dependences have been determined, thus allowing evaluation of energies and volumes of activation; neopentane, ED=3.5 kcal/mole and ΔVΔ=31 cm3/mole tetramethyl silane, ED=1.16 kcal/mole and ΔVΔ=22 cm3/mole. The numbers given for neopentane are average values as the lnD vs 1/T and lnD vs p plots were not straight lines. Kirkwood's theoretical relation for the self-diffusion coefficient of spherical molecules has been tested for the quasi-spherical neopentane. At 0°C the theoretical value is 6×10—5 cm2/sec while the experimental value is 2.6×10—5 cm2/sec. The Kirkwood equation for the self-diffusion coefficient is discussed in detail.
Potential Energy Curves for OH
Authors: Fallon Robert J. , Tobias Irwin , Vanderslice Joseph T.
Published: January 2005

Potential energy curves for four of the bound states of OH have been calculated by the Rydberg-Klein-Rees method. Various mechanisms to explain the anomalously high population of the v′=2 and 3 levels of the A 2Σ+ state are discussed.
Diffusion Coefficients of Helium in Fused Quartz
Authors: Swets D. E. , Lee R. W. , Frank R. C.
Published: January 2005

The diffusion of helium through the walls of high-purity fused quartz hollow cylinders was studied using a mass spectrometer as a detecting device. By surrounding the outside of the hollow cylinder with helium and observing it diffuse through into the mass spectrometer, permeation rates and diffusion coefficients were measured in the temperature range of 24° to 1034°C. The diffusion process appeared to be relatively simple with only small deviations from Fick's laws occurring. The activation energy was found to be different in the temperature range of 24° to 300°C than in the range of 300° to 1034°C. In the low-temperature range the diffusion coefficients are expressed by D=3.04×10−4exp(−5580±56 cal/g atomRT)cm2/sec,and in the high-temperature range they are expressed by D=7.40×10−4 exp(−6613±40 cal/g atomRT)cm2/sec.The solubility was also determined by dividing the permeability by the diffusion coefficients. This was expressed by S=1.99×1017 exp(−−680±60 cal/g atomRT)atoms/cm3in the temperature range of 24° to 300°C and by S=1.28×1017 exp(−−1174±120 cal/g atomRT)atoms/cm3in the range 300° to 1034°C.
On the Fluorine Molecule. Part I. The Pilot Calculation
Authors: Hijikata Katsunori
Published: January 2005

The energy levels of the fluorine molecules F2 are calculated by ASMO method. First and second quantum orbitals and configurations therefrom are all taken into account, resulting in D0=1.99 ev and Re=1.41 A. Vertical excitation energies of 1Σg+—1Πu and 1Σg+—3Πg are 5.21 ev and 3.93 ev, respectively. The importance of the configurations and of the inner-shell electrons to the ground state is discussed. Finally, the ionicities of the states are evaluated.