bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalyzed Dissociation of N2 in Microwave Discharges. I
Authors: Young Robert A. , Sharpless Robert L. , Stringham Roger
Published: January 2005

Atomic nitrogen, produced from very pure nitrogen in a microwave discharge and detected by means of electron paramagnetic resonance, was increased from 2.0×1013 atoms/cm3 to 1.2×1015 atoms/cm3 by the addition of ≈5×1012 molecules/cm3 of SF6 to the gas before the discharge; the pink glow intensity also is increased several orders of magnitude and its time duration extended by ≈10. Nitric oxide and oxygen increase the number of atoms leaving the discharge to the same extent as SF6, but much larger amounts must be added. When nitric oxide is added between the discharge and the subsequent pink glow, comparable increases in atomic nitrogen concentration (≈20 times) are observed without the production of oxygen atoms.
Shear and Structural Relaxation in Molten Zinc Chloride
Authors: Gruber G. J. , Litovitz T. A.
Published: January 2005

Longitudinal ultrasonic absorption and velocity measurements were made in molten zinc chloride in the frequency range 5–95 Mc/sec. Shear relaxation measurements were obtained in the frequency range 43–118 Mc/sec. A single relaxation time was observed for the absorption of longitudinal waves at each temperature investigated. The absorption data demonstrated the existence of a volume viscosity which was found attributable to a structural single-relaxation mechanism. Shear and structural relaxations were both present with the same single relaxation time. The activation energies for the shear and compressional flows are approximately equal. The variation of the relaxation time with temperature is in accordance with the rate theory. The shear modulus and the relaxational part of the compressional modulus increase exponentially with decreasing temperature. The temperature dependence of the former is predicted by the two-state model of the hole theory. From numerous physical properties of molten zinc chloride and from the known crystalline state, a structural model is proposed for the melt. Two points are emphasized: (1) that there exist large ion complexes and (2) that there is a lack of network character in liquid ZnCl2. Based on this model, an explanation of the existence of distribution of relaxation times, observed in the glass-forming network liquids, is offered which attributes the presence of a whole spectrum of relaxation times in these liquids to the cooperative nature of their flow process. The measured single relaxation time of molten zinc chloride owes its origin to its nonnetwork character.
On the Use of the WBK Method for Obtaining Energy Eigenvalues
Authors: Beckel Charles L. , Nakhleh Jamil , Chowdary Yalamanchili R.
Published: January 2005

A general method is proposed for evaluation of the second-order WBK energy integral. The domain of the potential is extended into the complex plane by expansion in Taylor's series about the classical turning points. The method is illustrated by application to the one-dimensional harmonic oscillator for which the second-order integral is exactly zero. Application is also made to a typical molecular potential, the Heitler—London potential for H2. In the latter problem ``exact'' eigenenergies, accurate to about 0.2 cm—1, are obtained by a Runge—Kutta integration of the Schrödinger equation. These are compared with first-order WBK energies obtained with and without use of the Langer—Kemble radial correction, and with second-order WBK energies obtained with and without use of the Langer—Kemble correction. The uncorrected first-order WBK energies are accurate to within 2 cm—1 and first differences to within 0.6 cm—1. Uncorrected second-order WBK energies agree with the Runge—Kutta values and, in fact, are probably more accurate than the latter. The first-order Langer—Kemble corrected energies are up to 9 cm—1 in error; corrected first differences, however, are more accurate than uncorrected values at low quantum numbers. The poorest set of energies and first differences are the corrected second-order values, indicating that the Langer—Kemble correction is not applicable when the second-order WBK approximation is employed. Computing time requirements and advantages of the WBK and Runge—Kutta methods are briefly discussed.
Statistical Treatment of Gadolinium and Thorium Hydrides
Authors: Schumacher David P.
Published: January 2005

An expression is derived for the hydrogen pressure over a metallic hydride which exhibits two plateau regions. The isotherms for the Gd–H2 and Th–H2 systems are calculated. Energy terms allow for vacancy—vacancy interactions and for the expansion or contraction of the lattice upon hydride formation. The calculated value for the expansion energy in GdH3 is —498±28 cal/mole and in ThH3.5 —269±66 cal/mole.
Microwave Spectrum of Lithium Chloride
Authors: Lide David R. , Cahill P. , Gold L. P.
Published: January 2005

The rotational transitions J=0→1 in the three lowest vibrational states of Li7Cl35 and the two lowest vibrational states of Li7Cl37 have been measured at a temperature of 600°—800°C. The molecular constants (in Mc/sec) for Li7Cl35 are: Be=21181.1±0.1, αe=240.2±0.2, γe=1.2±0.2; those for Li7Cl37 are: Be=20989.9±0.1, αe=236.9±0.2. The internuclear distance is re=2.02067±0.00006 Å. (The uncertainties represent maximum limits of error.) A combination of the present results with molecular beam electric resonance data yields a dipole moment μv=7.075+0.0885 (v+½) D for Li6Cl35. Two high-temperature microwave spectrometers of new design are described briefly. A tabulation of molecular constants for the complete series of alkali halide molecules is included.
Some Excited States of the Hydrogen Molecule. I. 1Πu(1s2pΠ) and 3Πu(1s2pΠ)
Authors: Browne J. C.
Published: January 2005

Theoretical potential curves, spectroscopic constants, and expectation values for some one-electron operators are given for the 3Πu(1s2pΠ) (metastable) and 1Πu(1s2pΠ) states of the hydrogen molecule. Total energies of 0.7145 and 0.7334 a.u. are obtained for 1Πu and 3Πu, respectively. The experimental total energies are 0.7186 and 0.7381 a.u. for 1Πu and 3Πu, respectively. The maximum in the potential curve of the 1Πu state is found to be much smaller and to occur at a larger internuclear separation (0.02 eV at R≈8.5 a.u.) than estimated by previous theoretical calculations (0.1 eV at R≈4.5 a.u.). Our 1Πu curve is reasonably consistent with the observed data of Herzberg and Monfils.
Compressibility of Pyrolytic Graphite
Authors: Coleburn N. L.
Published: January 2005

The compressibility of pyrolytic graphite has been dynamically measured at pressures up to 0.5 megabar by utilizing explosive-generated shock waves. Shock and free-surface velocities normal and parallel to the original plane of graphite deposition were measured optically. The Rankine—Hugoniot shock-wave equations were used to determine the compression points corresponding to the measured velocities. The measurements failed to distinguish statistically between the two major crystal directions in regard to dynamic compressibility characteristics. The measured pressure—volume data for pyrolytic graphite and the results of Alder and Christian on natural graphite differ significantly at pressures above 100 kilobars. Within the range of the present experiments no transition of pyrolytic graphite to diamond was found.
Pair Correlations in Closed-Shell Systems
Authors: Krauss M. , Weiss A. W.
Published: January 2005

Pair function equations have been derived exactly for a restricted class of trial functions containing only closed-orbital pair correlations. In a matrix representation, it is shown that they reduce to a homogeneous pseudo-eigenvalue equation. The results are equally applicable to any set of unitarily transformed set of Hartree—Fock orbitals. Comparisons are made with the Sinanoğlu scheme, and computational problems are discussed.
Spectrum of Trivalent Erbium Ion in the Matrix of Calcium Fluoride
Authors: Pollack S. A.
Published: January 2005

In the following article the absorption and emission spectra of CaF2:Er3+ are presented, discussed, and analyzed phenomenologically. The crystalline states are listed and identified with the free ion quantum numbers by comparison with the states of erbium chloride. The oscillator strengths are determined from the absorbance spectrum and compared with the oscillator strengths reported in the literature. The study of the emission properties of the erbium ion in CaF2 includes identification of transition schemes for the major emission groups from their excitation spectra, measurements of relative intensities, decay times of fluorescence, and quantum efficiencies. The natural lifetimes and fluorescence yields were calculated using data obtained from the absorbance spectrum. By combining data obtained from the absorption and emission spectra at 77° and 4°K, the crystalline field splitting of the ground 4I15/2 multiplet was determined. The wavelengths of all emission lines at 77°K are presented, including those whose origin could not be identified. The effects of temperature and ion concentration are discussed. All pertinent data are given in a table form. The important features of the absorption and emission spectra are amply illustrated by figures, graphs, and tables. In addition to the purely spectroscopic properties of CaF2:Er3+, its properties as a potential laser material are considered and discussed. The discussion is complemented by calculation of the threshold power requirements.
Optimization of Molecular Wavefunctions by Scaling
Authors: McLean A. D.
Published: January 2005

The conditions that a set of molecular electronic wavefunctions for different nuclear configurations be optimized by incorporation of scale factors, in general different for each wavefunction of the starting set, are derived. The relationship of these conditions to the quantum-mechanical virial theorem in Born—Oppenheimer approximation is pointed out. The quantitative effects of such optimization on a set of accurate wavefunctions for the hydrogen molecule and a partially optimized single-configuration molecular-orbital wavefunction for lithium fluoride are discussed. Expectation values and spectroscopic constants are investigated in detail. It is shown that as the total molecular energy decreases, the quantitative effects of scaling will become progressively smaller. A further conclusion is that, for sets of unscaled diatomic-molecule wavefunctions only partially optimized, curves for kinetic energy and potential energy of the system as a function of internuclear separation are more accurately obtained from the total molecular-energy curve by use of the virial theorem than by use of computed mean values.
Study of Water Vapor Condensation on Shock-Tube Walls
Authors: Goldstein Raymond
Published: January 2005

Optical techniques have been used to study the condensation of water vapor on the inside surface of a glass section of a shock tube. Because of the thermal boundary layer, the gas (pure water vapor) at the walls experienced essentially an isothermal compression. By adjusting the initial conditions of the experiments, supersaturation of the water vapor was obtainable. The use of a shock tube resulted in very rapid compressions, permitting measurements to be made on a time scale the order of microseconds. This is a much faster time scale than has been reported by other investigators of condensation processes. The results of these measurements showed that the condensation process was very sensitive to the nature of the surface. For clean hydrophilic surfaces it was found that condensation occurred in the form of discrete droplets having an average radius of the order of about 0.2 μ, until at least about 100 μsec after compression. Hydrophobic surfaces produced condensation in the form of a continuous film. After reaching a thickness of about 100 Å in about 10 μsec after compression, the film appeared to begin to break up into many small droplets. The thin films of condensate were studied by measuring their optical transmissivity. The droplets were studied by making use of their light-scattering properties. The results of the measurements are shown to be in agreement with mechanisms of the condensation process suggested by other authors.
Vibrational Energy Exchange for a Morse Potential Interaction
Authors: Allen R. T. , Feuer P.
Published: January 2005

The vibrational energy transfer between an atom and an atomic oscillator is considered for a Morse potential interaction, from the point of view of thermal accommodation coefficient theory. An expression is obtained for the transition probabilities for the exchange of one quantum of energy. A comparison is made with the semiclassical theory. Inconsistencies in the literature are noted and discussed.
Photoelastic Property of Cross-Linked Amorphous Polyethylene
Authors: Nagai Kazuo
Published: January 2005

By assuming the additivity of bond polarizabilities, a formal expression is derived for the difference Δγ in principal polarizabilities of a real polymer chain having constant end-to-end distance r. The expression is given as a series in powers of r2, whose coefficients are functions of the differences α1κ—α2κ in principal polarizabilities of constituent bonds, 〈r2k〉, and 〈r2k cos2Φiκ〉, (k≥1). Here, Φiκ is the angle between the end-to-end vector and the unit vector along the κth bond of the ith structural unit, and the averages refer to those about a polymer chain in free state. It is shown that if r2 is in magnitude of the same order as 〈r2〉, at the limit of infinite chain length the expression reduces to Δγ=310〈r2〉*−2 ∑ i,κ(α1κ−α2κ)(3〈r2cosΦiκ〉−〈r2〉)r2,where 〈r2〉* is such a part of 〈r2〉 as proportional to chain length.

The difference in principal polarizabilities of the ``equivalent random link'' is shown to be ΔΓ=12〈r2〉*−1 ∑ i,κ(α1κ−α2κ)(3〈r2cos2Φiκ〉−〈r2〉).An expression in a matrix form is derived for ΔΓ of the polyethylene chain. Numerical computations are made by a digital computer, using two geometrical models for this molecule recently proposed by Hoeve and by Nagai and Ishikawa, and also using Denbigh's and Bunn and Daubeny's values for bond polarizabilities. It is found that a good agreement is obtained between predictions of the theory and experimental values if Denbigh's values are used.
``Improved'' Free-Volume Theory of Liquids. IV. Supercells, Worms, and Tunnels
Authors: Chung Harold S. , Dahler John S.
Published: January 2005

The formalism for a ``supercell'' theory of liquids is presented. Conceptually, it is analogous to the scheme employed by Kirkwood in ``justifying'' the single-occupancy cell theory of Lennard-Jones and Devonshire. The attractive feature of the theory lies in its ability to handle the large density fluctuations which the single-occupancy theory is unable to treat adequately. The derivation of the numerically successful tunnel theory of Barker from our generalized supercell formalism by means of a certain number of well-defined approximations is given.
Determination of Lattice Vacancies in Graphite
Authors: Hennig G. R.
Published: January 2005

Vacancies in graphite crystals can be rendered visible for electron microscopy by a technique which combines cleaving, etching, and decorating. The crystals are cleaved, and the vacant lattice sites in the exposed surface are attacked by a mixture of chlorine and oxygen, which expands these vacancies into monolayer loops of any desired diameter. These loops are decorated with gold to enhance their contrast. Numerous tests have established that the loop concentration is a quantitative measure of the vacancy concentration. The method is capable of determining vacancies at concentrations at least as low as 10—10 per carbon atom. The relative chemical reactivities of carbon atoms surrounding a vacancy, of carbon atoms at the edges of layers and of carbon atoms within layers have been measured.
Kinetics of Small Systems. II
Authors: McQuarrie D. A. , Jachimowski C. J. , Russell M. E.
Published: January 2005

The application of stochastic proceses to second-order reactions is considered. Stochastic models for the bimolecular reactions 2A→B and A+B→C are formulated and solved exactly. The results of the stochastic solutions are compared with the deterministic results. Approximate methods of solving stochastic equations are also discussed and applied to various reaction processes.
Calculation of Hard-Sphere Viscosity by Means of Correlation Functions
Authors: Wainwright T.
Published: January 2005

The viscosity of a system of hard-sphere molecules is calculated under the assumption that terms in the autocorrelation of the stress tensor are in the form of a decaying exponential. The results are in close agreement with those of Enskog.
Mass-Spectrometric Study of the Reaction of Water Vapor with Solid Barium Oxide
Authors: Stafford F. E. , Berkowitz J.
Published: January 2005

Barium oxide disks in a platinum Knudsen cell were reacted with water vapor at temperatures between 1485° and 1785°K and water pressures up to approximately 10—4 atm. The effusing molecules were identified and measured mass-spectrometrically. Although no Ba(OH)2+ ion was observed, the species BaOH+ was inferred to have come from both BaOH and Ba(OH)2 because of its dependence on the water pressure. From the observed equilibria, BaO(s)+H2O(g)→Ba(OH)2(g)ΔH0∘+ 50.0 kcal/mole,BaO(s)+BaO(g)+H2O(g)→2BaOH(g)+12O2(g)ΔH0∘=122.3 kcal/mole,2BaO(g)+H2O(g)→2BaOH(g)+O(g)ΔH0∘= 69.2 kcal/mole.These lead to a HOBa–OH bond energy of 99 kcal/mole and a Ba–OH bond energy of 107 kcal/mole. The latter number differs significantly from a value deduced from studies of flame spectra and implies that the concentration of hydroxide species in these flames has been underestimated by several orders of magnitude.
Semiconducting Organic Polymers Derived from Nitriles. Thermoelectric Power and Thermal Conductivity Measurements
Authors: Katon J. E. , Wildi B. S.
Published: January 2005

The thermal conductivities and thermoelectric powers of two previously reported polymeric organic semiconductive materials are reported. One system, thought to be a form of oxidized polyphthalocyanine, shows very complex behavior on heating in the presence of oxygen. The thermoelectric power is very sensitive to this treatment but the electrical resistivity, although changing slightly, is relatively insensitive. Two different oxygen—polymer effects, one reversible and one irreversible, appear to be superimposed in this system.
Ionization of Oxygen by ``Monoenergetic'' Electrons
Authors: Brion C. E.
Published: January 2005

A mass spectrometer equipped with an electron-velocity selector has been used to measure five ionization potentials of molecular oxygen. These results are in good agreement with the available spectroscopic data, and in addition are consistent with earlier work done by the indirect RPD method. The structural features of the ionization-efficiency curve are discussed in the light of recent theoretical studies. It is concluded that for oxygen the computed transition probabilities are generally incorrect, except for the ground state of O2+. Using a second apparatus with an electron selector of improved construction, but no mass analysis, the transitions to individual vibrational levels of the 2IIg ground state of O2+ have been observed. The transition probabilities are in reasonable agreement with theory.
Reactions of Photochemically Produced Hot Hydrogen Atoms. II. Reaction and Moderation Probabilities for 3-eV H Atoms in D2, CD4, and C2D6 and for 3-eV D Atoms in H2, CH4, and C2H6
Authors: Martin Richard M. , Willard John E.
Published: January 2005

Three-electron-volt H atoms produced in D2, CD4, or C2D6 by the photolysis of HBr may produce HD by hot-atom reaction with the deuterated species, or H2 by hot reaction with HBr, or may be thermalized by moderating collisions and scavenged by thermal reaction with HBr. Plots of the product ratios, H2/HD, vs the reactant ratios, HBr/RD, give straight lines. The values of the intercepts are equal to the ratio of the atoms moderated to those which undergo hot reaction with RD in pure RD. From the slopes and intercepts it is possible, with plausible assumptions, to deduce approximate values for the average probability of reaction per collision in the hot range and for the average fractional energy loss per moderating collision with the hydrocarbon. The latter value when compared with the calculated loss for elastic collisions gives an indication of the inelasticity of the collisions in the experimental system. These determinations have been made for the systems stated and for the isotopically reversed systems of DBr in H2, CH4, and C2H6. They indicate that the average probabilities of reaction per collision for the H atoms colliding with D2, CD4, and C2D6 are 0.18, 0.0034, and 0.019, respectively, while those for the reactions of the D atoms with the corresponding hydrogenated compounds are 0.35, 0.062, and 0.14. The ratio of actual energy loss per collision in this range to loss assuming elastic hard-sphere collisions is estimated to be about 1 for H+CD4, 4 for H+C2D6, 2 for D+CH4, and 4 for D+C2H6, based on the assumption that H+D2 and D+H2 moderating collisions are completely elastic. If these latter collisions are partially inelastic, both the estimated reaction probabilities and moderating efficiencies given above should be higher.
Two-Electron Atoms. IV. Some Sixth-Order Expectation Values
Authors: Scherr Charles W. , Knight Robert E.
Published: January 2005

The sixth-order perturbation ground-state wavefunction for two electrons about a nucleus of charge Z obtained in Paper III of this series is used to compute perturbation expectation expansion coefficients 〈Ω〉p for 34 operators Ω through p = 6 where the total expectation value of an operator 〈Ω〉 is given by 〈Ω〉 = ΣpZ—p〈Ω〉p in appropriate units. Estimates of the accuracy of the calculation are obtained by comparison with exactly known values, by comparison with total values obtained from the accurate variational calculations of Pekeris, and by comparison with calculations based on Eqs. (V.1) and (V.2) of Paper III of this series. The function of the higher order correction terms is discussed.
Kinetics of Diffusion-Controlled Processes in Liquids. Theoretical Consideration of Luminescent Systems: Quenching and Excitation Transfer in Collision
Authors: Yguerabide Juan , Dillon Michael A. , Burton Milton
Published: January 2005

The over-all behavior of reacting particles in solution is determined both by specific molecular properties and by probability of encounter. This paper presents an examination of the effect of the details of diffusion and locally inhomogeneous distributions on the over-all behavior of a system of reacting particles both for steady-state conditions and for the decay (or relaxation) phenomena subsequent to creation of an initial condition.

The problem is formulated for the quenching of excited molecules in solution in terms of diffusion equations for excited and quencher molecules with appropriate initial and boundary conditions. The diffusion equations are solved for a completely determined, but otherwise arbitrary, initial distribution of quencher molecules around an excited molecule and two sets of boundary conditions: the so-called Smoluchowski and ``radiation'' boundary conditions. The resultant equations give, in their turn, expressions for decay of excited molecules for initial random distributions following instantaneous excitation and, by the use of superposition integrals, for initial distributions following any form of excitation. Explicit expressions for the rise and fall of excited molecule concentrations result. The techniques are extendable in principle to a variety of essentially different processes.
Dielectric Constant of Hydrogen Bonded Liquids. III. Superheated Alcohols
Authors: Dannhauser Walter , Bahe Lowell W.
Published: January 2005

The dielectric constants of the eight lowest aliphatic alcohols have been measured from room temperature to their respective critical temperatures. The densities were also measured if they were not previously available. The data were analyzed in terms of Kirkwood's correlation factor based on a model of linear, hydrogen-bonded chains with restricted rotation about the hydrogen bond and variable degree of polymerization. The equilibrium constants are strongly dependent on the size and shape of the alkyl group. —ΔF°298 (kcal/mole; mole fraction units), —ΔH°298 (kcal/mole), and —ΔS°298 (cal/mole·deg) for hydrogen-bond formation in the pure liquid are: MeOH, 3.95, 6.50, 8.56; EtOH, 4.10, 8.63, 15.2; n-PrOH, 3.42, 7.76, 14.6; iso-PrOH, 2.97, 8.64, 19.1; n-BuOH, 3.12, 7.70, 15.4; iso-BuOH, 2.87, 8.73, 19.7; sec-BuOH, 2.05, 7.97, 19.9; tert-BuOH, 0.98, 7.28, 21.2.
NMR Study of Rotational Barriers and Conformational Preferences. I. Cyclohexyl Fluoride
Authors: Bovey F. A. , Anderson E. W. , Hood F. P. , Kornegay R. L.
Published: January 2005

The equatorial:axial ratio and rate of conformational isomerization of cyclohexyl fluoride has been measured by observation of the 19F resonance as a function of temperature (—87.6° to +29.5°) for a 25 vol.% solution in CCl3F. Rate information is readily obtained over a wide temperature range, since the equatorial and axial fluorines differ in chemical shift by 20.5 ppm; the equatorial and axial α protons differ in chemical shift by only 0.46 ppm.

Interpretation of the spectra in terms of isomerization rates is complicated by the following: (a) the equatorial and axial conformers are present in unequal proportions; (b) their ratio changes with temperature; and (c) 19F–H coupling produces fine structure and/or peak broadening. The general expression for spectral line shape resulting from exchange between two unequal, chemically shifted spin populations is plotted (using the IBM 7090 computer), chemical shift and conformer ratio data being obtained from the low temperature 19F spectra. The observed spectra fit the calculated spectra very closely, and can be used with their aid to obtain the rates for axial-to-equatorial and equatorial-to-axial isomerization. Excess line broadening resulting from 19F–1H coupling was eliminated by double resonance.

Modifications to the rate expressions arising from the differing entropies and enthalpies of the axial and equatorial conformers are presented. Theoretical expectations for the activation entropies and enthalpies are discussed and compared to observed values.
Vibrational Spectrum of Sodium Azide Single Crystals
Authors: Bryant James I.
Published: January 2005

The infrared and Raman spectra of a single crystal of sodium azide have been intensively investigated at 298° and 90°K using grating spectrometers. Selection rules for internal and lattice vibrations are determined by application of the unit cell (factor group) method of Bhagavantam and Venkatarayudu. The unit cell modes of the crystal belonging to irreducible representations of the unit cell group have been constructed to within a good approximation. Spectra in the infrared are characterized by the occurence of medium-strength absorptions symmetrically spaced about the principal bands of the spectrum with a separation of 122 cm—1. The observation of the Raman-active rotatory lattice mode at this frequency confirms the assignment of the medium-strength bands as sum and difference frequencies involving rotational motion of the azide ion as a rigid unit. Tentative assignments were made for all bands observed in the spectra and deduced frequencies for unobserved infrared lattice modes are presented. The spectra were found to be in good agreement with the accepted structure as described by the space group D3d5−R3̄m.
Phase-Space Theory of Chemical Kinetics
Authors: Light John C.
Published: January 2005

A theory of the cross sections of three-body gas-phase reactions which proceed without activation energy is presented. It is based on the hypothesis that the decomposition of a collision complex is governed by the phase space available to each product under conservation of angular momentum and energy. Calculations on model ion—molecule systems show that the cross section is enhanced if the reaction is exothermic, the final reduced mass is large, and the final long-range attractive forces are large. The theory gives a consistent explanation for the cross sections of the reactions between He+ and H2, and He and H2+ which is in satisfactory agreement with experiment.
Partial Pressures in Equilibrium with Group IV Tellurides. I. Optical Absorption Method and Results for PbTe
Authors: Brebrick R. F. , Strauss A. J.
Published: January 2005

An optical-absorption method has been developed for measuring the partial pressures of Te2(g) and MTe(g) in equilibrium with MTe(c), where M is Pb, Sn, or Ge. The partial optical densities of Te2(g) at 4360 Å and of MTe(g) at 3650 or 3100 Å are obtained by a Beer's-law analysis of the data, which use optical constants for Te2(g) and MTe(g) found in calibration experiments. Published vapor-pressure data are then used to calculate the partial pressures of Te2(g) and MTe(g) from their respective partial optical densities.

This paper reports results obtained by the optical absorption method for the Pb–Te system. Between 725° and 924°C, the maximum melting point of PbTe, the partial pressure of PbTe(g) in equilibrium with solid PbTe is given by logp(Torr) = —11,430/T°K+10.612, corresponding to a heat of sublimation of 52.3±1.0 kcal/mole. The PbTe(g) partial pressure is independent of the composition of PbTe(c) within the limits of experimental error. The partial pressure of Te2(g) varies strongly with the composition of the solid phase, as shown by data for Pb-saturated and Te-saturated PbTe. The maximum partial pressure of Te2(g) in equilibrium with PbTe(c) is 12.5 Torr, which is attained between 796° and 832°C for Te-saturated PbTe. At these temperatures the partial pressures of Te2(g) in equilibrium with Pb-saturated Te are about two orders of magnitude smaller. The partial pressures of PbTe(g) and Te2(g) in equilibrium with PbTe(c) at its maximum melting point are 11.8 and 2.5 Torr, respectively.
On the Relaxation Effect in the Electrical Conductivity of Plasmas and Electrolytes
Authors: Davis H. T. , Résibois P.
Published: January 2005

We apply the general formalism developed by Prigogine and co-workers to the problem of transport in plasmas and in electrolytes. Taking into account the collective effects due to the long range character of Coulomb forces, we obtain first an exact transport equation for a dilute plasma which we then generalize to an electrolyte, using a semiphenomenological description of the solvant. Special attention is given to the internal field effect which is shown to result from the interference between the external field and the collision processes. We show that, in very simple cases, good agreement is obtained with the Debye—Onsager limiting laws.
Electron Spin Resonance Study of the Pairing Theorem for Alternant Hydrocarbons : 13C Splittings in the Anthracene Positive and Negative Ions
Authors: Bolton James R. , Fraenkel George K.
Published: January 2005

The pairing theorem for alternant hydrocarbons predicts that the pi-electron spin densities at corresponding positions of the negative and positive ions of a hydrocarbon should be the same, but significant differences have been found previously for the proton hyperfine splittings in electron-spin resonance spectra. In order to examine the validity of the theorem more thoroughly, we have measured the 13C splittings in the ESR spectra of the anthracene negative and positive ions. These have been obtained by studying the satellites arising from 13C nuclei present in natural abundance and also by investigating anthracene labeled with 50% 13C in the 9-position. All of the four possible splittings were determined for the negative ion and assigned to the appropriate positions in the radical, and three of the splittings were obtained for the positive ion. The assignments of the splittings, and also their signs, were established by linewidth studies, counter-ion effects, and calculation. The negative ions were produced by reduction with lithium, sodium, and potassium, and also electrolytically. An apparatus for the electrolytic generation of radicals in vacuo is described. The positive ions were formed in concentrated sulfuric acid.

The 13C splittings in the positive and negative ions of anthracene were found to be almost identical. This result is most readily interpreted as implying that the pairing theorem is valid to a high degree of approximation for the spin densities and for those of the sigma—pi parameters (Q's) which govern the 13C splittings.
Electron Spin Resonance of Irradiated Single Crystals of Alanine: Proton—Deuteron Exchange Reaction of a Free Radical in the Solid State
Authors: Itoh Koichi , Miyagawa Ichiro
Published: January 2005

Proton—deuteron exchange reaction of radicals in irradiated crystals of deuterium substituted alanine CH3CHND2COOD was studied by ESR technique. It was shown that this exchange does not take place for the molecules in the crystal but only for the radicals. The exchange rate is very slow at room temperature: exchange is hardly detectable within one month after irradiation. As the temperature rises, however, the rate increases greatly: all the four protons of the radical CH3ĊHR are exchanged after about 10 h of heating at 150°C. The exchange rate for the earlier period of heating is independent of radiation dosage, whereas that for the later period depends on dosage. The activation energy and the frequency factor for the first step were found to be 24.6±1.5 kcal/mole and 1×1010∼4×1011/sec, respectively.
Intermolecular Potential in Solid Methane. I. Cohesive Energy and Crystal Structure
Authors: Kimel S. , Ron A. , Hornig D. F.
Published: January 2005

The cohesive energy of crystalline methane is calculated for various possible structures, using a potential function consisting of repulsive and attractive interactions between nonbonded atoms. The necessary parameters were taken without adjustment from independent studies of other systems. It was found that the tetragonal structures of symmetry D3d have the best packing. The cohesive energy was increased when the unit cell was distorted from the cubic dimensions, the volume remaining constant. The maximum contribution of this distortion (about 1% of the total energy) occurs when the c axis of the unit cell is elongated 12%. The calculated stability of the crystal is not affected by slight displacements of the molecules along the c axis. On the other hand, the calculated stability of the crystal decreases upon rotation or upon distortions from Td symmetry of the individual molecules in the lattice.
Estimation of Diffusion Coefficients from Viscosity Measurements: Polar and Polyatomic Gases
Authors: Weissman Stanley
Published: January 2005

Mutual diffusion coefficients for pairs of gases composed of polar and polyatomic molecules have been estimated from the experimental viscosities of binary mixtures. The derived diffusion coefficients fall within the scatter of the directly measured experimental diffusion coefficients. These results are consistent with the formal kinetic theory of polyatomic gas mixtures developed by Mason and Monchick where they have taken into consideration inelastic molecular collisions.
Electronic Absorption Spectrum and Structure of CuCl4=
Authors: Ferguson J.
Published: January 2005

Polarized crystal-absorption spectra in the near-infrared, visible, and ultraviolet regions are reported for Cs2CuCl4. The near-infrared bands are analyzed on the basis of the known structure of the CuCl4= ion with D2d symmetry. The positions and polarizations of the bands are accounted for and the minor effcets of spin—orbit coupling and the true-site symmetry (Cs) are discussed. The observations agree very well with the theoretical calculations of Lohr and Lipscomb and differ from the pure electrostatic crystal-field theory. An analysis of the electron-transfer bands has been made. It is concluded that the CuCl4= ion in solution has a structure which is close to that found in the crystal of Cs2CuCl4.
Quantum-Mechanical Formulation of a Strong Collision Theory of Unimolecular Rates
Authors: Wilson David J. , Thiele Everett
Published: January 2005

A wave-packet analysis is used to cast Slater's ``new approach'' to unimolecular rate theory into quantum form. Qualitative information about the pressure dependence of unimolecular rate constants is obtained, and the activation energy is found to be consistent with Tolman's interpretation.
Entropies of Some Gaseous Metal Dihalides
Authors: Hildenbrand D. L.
Published: January 2005

The entropies of some gaseous metal dihalides have been derived from vapor pressure and condensed-phase entropy data where such information is available, and are compared with entropies calculated from molecular constant—spectroscopic data. In some cases, the experimental entropies are appreciably higher than those calculated from molecular constants. The discrepancies could result from the use of bending frequencies which are too high.
Geometry of the Transition-Metal Dihalides: The Fluorides of Manganese, Cobalt, Nickel, Copper, and Zinc
Authors: Büchler Alfred , Stauffer James L. , Klemperer William
Published: January 2005

The deflection of mass spectrometrically detected beams of CaF2, MnF2, MnCl2, CoF2, NiF2, CuF2, ZnF2, ZnCl2, and HgCl2 by an inhomogeneous electric field has been examined. As found previously, CaF2 deflects in the manner expected for a polar molecule. The remaining molecules listed were found to be nonpolar. These observations are interpreted to imply that while CaF2 has a nonlinear equilibrium geometry the remaining species are linear. The result for HgCl2 is in agreement with a number of previous electron diffraction and spectroscopic studies.
Convergence of Fugacity Expansion and Bounds on Molecular Distributions for Mixtures
Authors: Baer S. , Lebowitz J. L.
Published: January 2005

We have generalized the methods developed recently by Groeneveld and Penrose for a one-component system to obtain a lower bound on the domain of convergence of the Mayer fugacity expansion of the pressure, p=Σbl1,···, lωΠzαlα,where zα is the fugacity of the αth component, α=1,•••, ω. This series is convergent for ∑ α=1ω|zα|≤[exp(1+2Φ/kT)B]−1,where B={max(α,β)} ∫ |exp[−(kT)−1φαβ(r)]−1|drand where the interaction potential φαβ(r) of a pair of particles of Species α and β satisfies ∑ i<j≤sφαiαj(|xi−xj|)≥−sΦfor all α, x, and s. [For a positive interparticle potential, φαβ(r)≥0, Φ=0.] Consequently the system remains in a single phase in this region. We have also generalized the inequalities of Lieb, Penrose, Lebowitz, and Percus to this case. For positive potentials upper (lower) bounds are gotten for the pressure and the distribution functions by expanding in a Taylor series up to terms of even (odd) total order in the fugacities.
Infrared Spectrum of Diboron Tetrafluoride in the Gaseous and Solid States
Authors: Gayles J. N. , Self J.
Published: January 2005

Infrared spectra of B2F4 are reported over the range 2.5 to 50 μ at small grating resolution for both the gaseous and polycrystalline states. Examination of band envelopes for the gas and of differences between gas and solid spectra indicates that a structural difference exists between gaseous and solid B2F4. It is suggested that the alteration is analogous to that observed for B2Cl4 with the Vd or staggered configuration applying in gas and the Vh or planar configuration applying in the solid. Rough estimates are made for some of the principal potential constants.
Pariser—Parr Theory: Quantum Mechanical Integrals from the Benzene Spectrum
Authors: Simmons Howard E.
Published: January 2005

The integrals which occur in Pariser—Parr ASMO—CI theory for carbon atoms at short internuclear distances (≤2.40 Å) can be derived from the spectrum of benzene [R. Pariser, J. Chem. Phys. 24, 250 (1956)]. Previously, various workers have uniformly neglected the highest singly excited configuration in the configuration interaction on the grounds of its high energy and because its inclusion destroys the simple linear formulas for the state energies of benzene. The effect of inclusion of this configuration on the spectral matching method of determining nearest-neighbor βpq, γpq, and γpp, employing the 1B2u, 1B1u, 1E1u, and 3B1u states of benzene has been investigated. The major effect was lowering of [11 | 11] to a value near that expected theoretically when correlation effects are considered. The influence of the new parameters on spectral calculations was explored for benzene, cis- and trans-butadiene, naphthalene, and azulene, and the major effect observed was in the energies of excited triplets. It is suggested that this set of parameters, derived consistently and solely from electronic spectra, will be useful for spectral calculations.
Optical Absorption of the F and K Bands in Rubidium Chloride
Authors: Stungis G. E. , Markham J. J. , Noble G. A.
Published: January 2005

Detailed measurements on the optical absorption of the F center in rubidium chloride are reported. The F centers were produced by additive coloration and ionizing radiation. The photon energies for the point of maximum and points of half-maximum absorption are determined for temperatures between 4° and 373°K. A single effective phonon frequency of ω = (2π)×2.43×1012 sec—1 is obtained from the dependence of the half-width on temperature. The shape of the F band is independent of temperature and is not symmetrical. The moments are computed. The asymmetry is greater than that predicted by the Poisson distribution and the second moment is close to that of a Gaussian. The ratio of the maximum of the K band to that of the F band is 0.03 in vacuum distilled material. In unpurified material this value is not reproducible and may be three times as large.
Effects of Wavelength and Temperature on Primary Processes in the Photolysis of Nitrogen Dioxide and a Spectroscopic—Photochemical Determination of the Dissociation Energy
Authors: Pitts James N. , Sharp James H. , Chan Sunney I.
Published: January 2005

The quantum yields of oxygen production in the photolysis of nitrogen dioxide have been determined at a series of wavelengths at room temperature and as a function of temperature at 3660, 4047, and 4358 Å. These values were satisfactorily correlated with the extent of dissociation into NO and O atoms by means of 18–18O2 tracer techniques. On the basis of the above correlation and inert gas experiments, a general mechanism is proposed for the photolysis of NO2 from 3130 to 4047 Å. Temperature effects are discussed in terms of a theoretical calculation based on the population of the rotational energy levels of NO2. This leads to a spectroscopic—photochemical determination of the dissociation energy of NO2 in good agreement with that calculated from thermodynamic data.
Gaseous Ion Recombination Rates. III
Authors: Carlton Terry S. , Mahan Bruce H.
Published: January 2005

The rate constants for the bimolecular recombination of gaseous ions in three different systems have been determined. The results suggest that the recombination rate constant is not particularly sensitive to the chemical identity of the ions, and that complexes between ions and neutral atoms are important even at pressures below 10 mm Hg.
Forbidden Absorption-Band Systems of N2 in the Vacuum-Ultraviolet Region
Authors: Tanaka Y. , Ogawa M. , Jursa A. S.
Published: January 2005

Five systems of absorption bands of N2, whose upper states are a 1IIg, a′ 1Σu—, B′ 3Σu—, w 1Δu, and C 3IIu, were investigated in the 1070–1600-Å region. A 2-m and a 3-m vacuum spectrograph, both of normal-incidence-type, were used in this work. The observations were extended to high vibration levels for four of the systems, a(v=13), a′(v=15), B′(v=20), w(v=11), while in the C—X system only two bands were analyzed. The progression which was previously ascribed as belonging to the w—X system was studied in detail, and an alternate possibility of this progression being the v″=1 progression of the a—X system was definitely removed. However, a final designation of the upper electronic state must come from a rotational analysis, because the observed T00 of the state differed from that of the w state by approximately 40 cm—1.

The potential energy curves of the low-lying N2 states prepared by Mulliken are compared with those calculated by using the presently determined constants.
Lattice Energy of Ionic Crystals
Authors: Negrete P. , Prieto F. E.
Published: January 2005

Some recent data on the shock-wave compression of sodium chloride are used to obtain the equation of state and the volume dependence of some thermodynamical functions in the pressure range from 50 to 800 kilobars. Various possible expressions for the free energy are assumed and the results are discussed and compared between themselves and with the available experimental data. It is found that the data are not sufficient to make a decision in favor of any of the assumptions, because in all the cases the agreement with the available data is very good.
Hyperfine Structure in the Microwave Spectrum of HDO, HDS, CH2O, and CHDO : Beam-Maser Spectroscopy on Asymmetric-Top Molecules
Authors: Thaddeus P. , Krisher L. C. , Loubser J. H. N.
Published: January 2005

Hyperfine structure in the 220→221 rotational transition of HDO at 10 278.2 Mc/sec and HDS at 11 283.8 Mc/sec, and in the 211→212 rotational transition of CH2O at 14 488.6 Mc/sec and CHDO at 16 038.1 Mc/sec, has been investigated with a high-resolution beam maser microwave spectrometer. Linewidths of 5 kc/sec have been obtained. The hyperfine Hamiltonian for an arbitrary number of nuclei with quadrupole, spin—rotation, and spin—spin interactions is discussed, and the matrix elements of the Hamiltonian and the intensities of hyperfine transitions calculated in terms of the tabulated 6j coefficients. Quadrupole and spin—rotation constants and bond lengths which have been determined are, for the 220 state of HDO: (eqJQ)D = 79.3±0.3 kc/sec, CH = —43.47±0.11 kc/sec, CD = —2.33±0.02 kc/sec; for the 221 state of HDO: (eqJQ)D = 79.6±0.3 kc/sec, CH = —43.63±0.13 kc/sec, CD = —2.20±0.02 kc/sec; for the 220 state of HDS: (eqJQ)D = 42.9±0.4 kc/sec, CH = —25.03±0.13 kc/sec, CD = —0.47±0.02 kc/sec; for the 221 state of HDS: (eqJQ)D = 43.3±0.4 kc/sec, CH = —25.45±0.13 kc/sec, CD = —0.22±0.02 kc/sec; for CH2O: CH (211) — CH (212) = 2.26±0.13 kc/sec, CH (211) = 0.65±0.50 kc/sec, 〈1/rHH3〉—⅓ = 1.898±0.017 Å; for CHDO: (eVξξQ)D = 170.0±2.0 kc/sec (where Vξξ is the second derivative of the electrostatic potential along the CD bond), CH (211) — CH (212) = 2.42±0.50 kc/sec, CD (211) — CD (212) = 0.25±0.10 kc/sec, CH (211) = 0.2±1.0 kc/sec, CD (211) = 0.13±0.20 kc/sec, and 〈1/rHD3〉—⅓ = 1.88±0.10 Å. The Vξξ calculated from the deuteron quadrupole coupling constants are, for HDO: 1.56×1015 statvolt/cm2; for HDS: 0.76×1015 statvolt/cm2; and for CHDO: 0.83×1015 statvolt/cm2.
Intercombination Spectra of Chromium Acetylacetonate Crystals at Low Temperatures
Authors: Armendarez Peter X. , Forster Leslie S.
Published: January 2005

The spectra of chromium acetylacetonate and several derivatives have been recorded at 77° and 4°K. The structure in the 12 000–15 000 cm—1 region has been assigned to vibronic components of 2E←4A2 and the 2T1 state located. The effect of ligand halogenation on the trigonal field splitting is small.