bluuebunny/crossref_metadata_2025 huggingface dataset:
Color Centers and Luminescence in Single Crystals of Lanthanum Trichloride Containing Dipositive Europium
Authors: Gruen Dieter M. , Conway John G. , McLaughlin Ralph D.
Published: January 2005

The edge of the fundamental absorption band in pure LaCl3 is at about 2250 A. There is no change in the absorption spectrum of pure LaCl3 in the range 2250 to 25 000 A on exposure at room temperature to 107r of gamma rays from a Co60 source. The crystals do not luminesce after such treatment.

In contradistinction, LaCl3 containing small amounts of europium exhibits a blue luminescence and thermoluminescence when exposed to ultraviolet or gamma radiation. The luminescent properties are profoundly influenced by long continued gamma irradiation. In addition, color centers are formed which absorb visible radiation.

Chemical as well as paramagnetic resonance experiments show that all of these effects are due to the presence in the LaCl3 lattice of dispositive europium. There are at least three different color centers giving rise to three overlapping absorption bands which decay thermally with different rates. The maxima of the absorption bands are at 8000, 6500, and 5500 A. Studies with polarized light show that the color center transitions are all electric dipole in nature and are highly anisotropic. The most intense band has been tentatively identified with an F-center-like s→p transition.

Experiments on the thermal decay of the color bands and the glow curve of the crystal indicate that an intimate relationship exists between the color center and the luminescence phenomena.

It is suggested that when these crystals are irradiated, dipositive europium loses an electron to become tripositive, the electron being captured by an anion vacancy to form a color center. On thermal freeing of the electron, return to the ground state is accompanied by the emission of visible radiation.
Electronic Spectrum and Structure of Azulene
Authors: Pariser Rudolph
Published: January 2005

A previously given theoretical method is applied to the azulene molecule. π-electron energies, transtion moments, dipole moments, charge distributions, and bond orders are calculated for the ground state and for the lower singlet and triplet excited states.

The same detailed procedure which had previously given good results for the polyacenes is used here. Configuration interaction is included for all singly excited configurations. Two parallel calculations, one starting with conventional Hückel MOs and the other with perimeter MOs, are carried through.

Hückel MOs lead to numerical results in good agreement with available experimental spectral data. In this connection some previous assignments are confirmed and some new ones are proposed. For the π-electron dipole moment for the ground state, one calculates 1.88 D with Hückel MOs and 3.36 D with perimeter MOs; the experimental value is 1 D.

One may conclude that the present procedure gives results in substantial agreement with experiment provided that good MOs, e.g., Hückel MOs, are employed. For computation of excited state energies it is essential to include interaction among nearly degenerate configurations. More extensive configuration interaction, however, appears to improve the transition energies and especially the transition moments and dipole moments.
Infrared Spectrum of Hydrogen Sulfide
Authors: Allen Harry C. , Plyler Earle K.
Published: January 2005

The absorption of hydrogen sulfide has been investigated in the 8 μ region under high resolution. The absorption has been analyzed as a B-type band and assigned as the (n1,n2,n3)=(0,1,0) band. The resulting inertial constants agree well with those predicted from previously analyzed bands. The best values of the constants for this band are, v0=1182.68 cm—1, A=10.724, B=9.211, C=4.670. The knowledge of this band center, together with previously determined frequencies, enable the evaluation of the constants in the quadratic expression for the vibrational energy. A second-order resonance was found which arises from the near coincidence of the frequencies v1 and v3.
Hydrogen as a Donor in Zinc Oxide
Authors: Thomas D. G. , Lander J. J.
Published: January 2005

Hydrogen is found to diffuse into and increase the conductivity of single ZnO crystals. The diffusion rates have been obtained, as well as the temperature and pressure dependencies of the quantity of hydrogen in the crystal. This quantity is found to be influenced by the electrons already in the crystal. It is thought likely that hydroxyl groups are formed from the hydrogen and oxide ions. The donor center has an ionization energy of 0.04 ev.
Application of Probability Theory to Explosive-Ignition Phenomena
Authors: Parlin Ransom B. , Giddings J. Calvin
Published: January 2005

The problem of explosive ignition concerns itself both with the probability of occurrence of local energy fluctuations and with the transition of these disturbances into a combustion or detonation wave. The former concept does not appear to have been comprehensively discussed; a treatment of this process is presented here for the case of fluctuations due to frictional forces.

The theory is applied to several cases of impact ignition, both with and without grit particles and it is found to be in good agreement with experiment. Information is obtained through application of the theory concerning the nature and location of the local disturbances responsible for ignition.
Infrared Absorption of Lanthanum, Scandium, and Indium Borate and the Force Constants of Borate Ion
Authors: Steele W. C. , Decius J. C.
Published: January 2005

The infrared absorption spectra of LaBO3, InBO3, and ScBO3 have been observed as crystalline powders in the wavelength range from 7 to 20 microns. The borates had a B10/B11 ratio varying from the natural abundance (18/82) up to about 96/4. The four fundamental frequencies for B10 fell within the ranges, ω1 = 939, ω2 = 740–790, ω3 = 1265–1330, ω4 = 606–675, all in cm—1. The totally symmetric frequency, ω1 is observed only in LaBO3, which has less than threefold site symmetry, unlike the other two salts.

The GVF force constants have been calculated and are compared with those of BF3. A very strong specific coupling of the out-of-plane bending mode (ω2) is observed in LaBO3, but the fine structure is not well resolved, and only a rough estimate of the coupling constant and dipole derivative can be made.
Microwave Spectrum of β Propiolactone
Authors: Kwak Nowhan , Goldstein J. H. , Simmons J. W.
Published: January 2005

The microwave spectrum of propiolactone has been studied in the 18–34 kmc region. Analysis of the data obtained leads to the conclusion that the ring is planar and ∠HCH=112°. Satellite spectra are observed and attributed to the out-of-plane ring bending mode with a first excited state 120 cm—1 above ground. Quantitative Stark effect studies support the planarity assumption and lead to a dipole moment of 4.18±0.04 d. The possible orientations of the dipole are considered.
Structures of Toluene, Phenylsilane, and Diphenyldichlorosilane
Authors: Keidel F. A. , Bauer S. H.
Published: January 2005

Electron diffraction data taken with a ``sector'' apparatus are presented. Procedures for the reduction of such data are discussed. Theoreticasl backgrounds (the sum of atomic coherent plus incoherent scattering) based on Pauling-Sherman and on Hartree atom form factors are compared with the curves observed. Structural information was derived from the resolution of radial distribution curves, and the final molecular models were checked by comparing theoretical molecular scattering curves with the reduced microphotometer traces.
Rate Processes and Nuclear Magnetic Resonance Spectra. II. Hindered Internal Rotation of Amides
Authors: Gutowsky H. S. , Holm C. H.
Published: January 2005

Mathematical methods are presented for calculating rate constants of processes which narrow nuclear magnetic resonance absorption lines having discrete components. High resolution proton spectra show that the R1CO-NR2R3 skeletons of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) are planar and suggest that N-methylformamide, N-methylacetamide, N-methylformanilide and N-methylacetanilide exist predominantly in one configuration. The presence of a significant amount of double bond character in the C–N amide bond is proved by the temperature dependent coalescence observed for the chemically shifted proton doublet of the N(CH3)2 groups in DMF and DMA, which gives values of about 22 and 19 kcal respectively for the free energy of activation required for reorientations about the bond.
Configuration of a Polyelectrolyte Chain in Solution
Authors: Krieger Irvin M.
Published: January 2005

Starting with the Gibbs-Boltzmann relation between the probability of a configuration and its energy, an expression is derived for the probability of the configuration of a random chain having central interactions among its groups. By an approximate integration method suggested by Debye, a distribution function is derived for the vector between the chain ends. The result is applied to find the distribution and the mean square end-to-end distance of a polyelectrolyte ion.
Self-Diffusion of Silver in Silver—Palladium Alloys
Authors: Nachtrieb N. H. , Petit J. , Wehrenberg J.
Published: January 2005

The self-diffusion of silver has been studied in alloys containing 0.00, 1.49, 3.69, 9.87, and 21.84 atom percent palladium at four temperatures: 715.4, 799.4, 861.8, and 942.0°C. The rate decreases with increasing palladium atom fraction according to the relation: DAg=0.270e—8.20Xe—43, 700/RT. An alternative expression is DAg=0.270e—17.75T m/T. Within experimental error, the activation energy is independent of palladium content. The rate of self-diffusion of silver is related to the solidus line of the silver-palladium phase diagram, and a simple corresponding states explanation is given.
Numerical Solution to the Poisson-Boltzmann Equation for Spherical Polyelectrolyte Molecules
Authors: Wall F. T. , Berkowitz Joan
Published: January 2005

The Poisson-Boltzmann equation for a penetrable spherical polyelectrolyte ion in the presence of smaller ions has been solved precisely by numerical integration methods using a high-speed computer. The polyelectrolyte ion was assumed in one case to be immersed in a sea of simple electrolyte and in another case to be surrounded by an appropriate volume of solution containing only the polyelectrolyte's counter ions. Since the absolute value of the electrostatic potential energy of a small ion in the center of a polyelectrolyte ion is found to be several times kT, the nonlinear differential equation cannot justifiably be rendered linear by the Debye-Hückel type of approximation. The fraction of the counter ions held within the sphere of the polyelectrolyte ion is calculated from the solution to the differential equation. The extent of such ion association is found, for reasonable values of the molecular parameters, to range between 50 and 75% in substantial agreement with experimental observations based on transference studies. The results of the numerical computations are for the most part presented graphically.
Raman Spectrum and Vibrational Assignments of Gaseous Dimethyl Ether
Authors: Taylor Robert C. , Vidale Guido L.
Published: January 2005

The Raman spectrum of gaseous dimethyl ether has been obtained and that of the liquid reinvestigated. In the low-frequency region of the gas spectrum, two bands have been observed which are attributed to overtones of the torsional motions of the methyl groups. The assignment of vibrational frequencies is discussed on the basis of a C2v symmetry in the molecule.
Microwave Determination of the Structure of Fluorobenzene
Authors: Bak Bo/rge , Christensen Daniel , Hansen-Nygaard Lise , Tannenbaum Eileen
Published: January 2005

3D-, 4D-, and 2,4,6 D3-fluorobenzene have been prepared. Their microwave spectra have been recorded and analyzed. Values of their rotational constants together with known values of the rotational constants of ordinary fluorobenzene do not suffice for an unambiguous calculation of the 11 geometrical parameters of the molecule but by assistance from valence theory a small number of fairly probable models may be pointed out.
Short-Range Intermolecular Forces. I
Authors: Mason Edward A. , Hirschfelder Joseph O.
Published: January 2005

A method is given for accurately approximating most of the integrals which occur in calculations of intermolecular forces. Two types of integrals arise; those between orbital pairs which are separated by a considerable distance from each other, and those where the orbital pairs overlap. In the first case the orbital pairs are considered to be electrostatic charge distributions and their energy of interaction is given by a multipole expansion. From a practical standpoint it is necessary to consider only the first few terms (through quadrupoles) of such an expansion. When the orbital pairs overlap, the integral can be approximated by the Mulliken formula in terms of Coulombic type integrals which are then further approximated by the multipole expansion. The problem of calculating intermolecular forces is thereby reduced to the calculation of a number of classical electrostatic multipole interactions. The procedure can be applied to Coulombic as well as exchange forces. Examples are given for the interaction of two hydrogen atoms (in the triplet sigma state), first the repulsion energy alone, and then the combination of Coulombic and exchange energies showing the lack of additivity; the energy of repulsion between two helium atoms; and the energy of repulsion between a hydrogen and a helium atom.
Effect of Pressure on Dielectric Properties and Volume of 1-Propanol and Glycerol
Authors: Gilchrist A. , Earley J. E. , Cole R. H.
Published: January 2005

Dielectric constants and loss have been measured to pressures of 1000 kg/cm2 at audio- and radio-frequencies from 212 to 240°K for glycerol and 124 to 210°K for 1-propanol. Compressions to 1000 kg/cm2 have been measured to room temperature.

The increases in static dielectric constant are less than predicted from density increase alone, and the differences are discussed in terms of molecular compression and liquid structure effects. Larger increases of relaxation time with pressure are found at lower temperatures. Constant volume relaxation times do not conform to a simple rate law, and cannot be explained by activation energies depending only on volume. Glycerol shows small, temperature independent, percentage volume decrease with pressure over the whole range; 1-propanol becomes much less compressible at low temperatures.
Equations for a Lattice Gas. I. One-Component Systems
Authors: Levine Howard B. , Mayer Joseph E. , Aroeste Henry
Published: January 2005

An expression is developed for P/kT for a lattice gas with an arbitrary lattice as a power series in the nearest neighbor interaction parameter, λ, with the coefficients functions of the activity, z. This result is applied in some detail to the cubic close packed lattice, for which expressions for the number density, ρ, and the probability of finding a cell adjacent to a filled cell also filled, ρv, are also given. These results are also transformed so as to give P/kT, lnz, and v as power series in λ with the coefficients functions of ρ.

A development for P/kT for an arbitrary lattice with different interactions for different distances between lattice sites is also given. The equation permits numerical evaluation without too great difficulty.
Cell Method Computation for Liquids
Authors: Levine Howard B. , Mayer Joseph E. , Aroeste Henry
Published: January 2005

A numerical equation of state for heavy rare gases in the neighborhood of the critical point has been computed, using a cell model distribution function containing a parameter which correlates the probability of a distribution with the number of pairs of particles in adjacent cells for the distribution, as well as a variable mean number of particles per cell (range zero to one), a variable cell size, and a variable distribution of particles with respect to the cell centers. The energy was approximated by the sum of the interactions of pairs of particles in adjacent cells only, and the parameters of the distribution function were then chosen so as to minimize the Helmholtz free energy per particle at constant density and temperature. The critical constants were determined, and the vapor pressure and the molecular volumes of the liquid and gas phases in equilibrium with each other were determined as functions of the temperature near the critical temperature. An estimate was made of the improvement in the Helmholtz free energy to be expected from the inclusion of the interactions of nonadjacent particles in the calculation of the energy.
Displacement of the Maximum in the Concentration-Time Diagram of Uni-bi-, Bi-uni-, and Bi-bimolecular Consecutive Reactions
Authors: Talât-Erben M.
Published: January 2005

As an extension of the results previously reported for two first-order consecutive reactions, the expressions k1·tmax and [B]max/[A]0 are studied as functions of temperature and initial parent concentration for uni-bi-, bi-uni-, and bi-bimolecular consecutive reactions.
Spectroscopic Survey of Energy Distributions of OH, C2, and CH Radicals in Low Pressure Acetylene-Oxygen Flames
Authors: Broida Herbert P. , Heath Donald F.
Published: January 2005

Rotational and vibrational ``temperatures'' from electronic transitions of OH, C2, and CH radicals have been measured in detail as functions of position in low pressure acetylene-oxygen flames. Pressures were varied from 0.8 to 6.0 mm Hg. Trends of ``temperature'' are presented as functions of mixture, pressure, position, mass flow rate, and burner size. Abnormalities in ``temperature'' are discussed. Evidence is presented for the existence of a newly discovered region at the base of the flame. This region is about 110 the visible flame thickness and is characterized by strong emission of C2 and CH relative to OH and by relatively high ``temperatures'' of C2 and CH. Just above this region the OH rotational ``temperature'' is very high, about 9000°K, and is independent of pressure.
Effect of Irradiation on the Low-Temperature Specific Heat of Graphite
Authors: DeSorbo W. , Tyler W. W.
Published: January 2005

The specific heat of heavily irradiated Acheson-type graphite has been measured from 13° to 300°K. Throughout this temperature range, the specific heat of the irradiated graphite is appreciably larger than that of unirradiated graphite of similar type. This difference is explained by assuming that interplanar atoms or clusters of atoms, give rise to modes of low energy which contribute to the specific heat at lower temperatures than do the normal lattice modes. The entropy of the irradiated sample at 298.16°K is 1.492±0.009 cal/g-atom deg compared with 1.372±0.005 cal/g-atom deg for the unirradiated graphite.
Pseudostationary State Approximation in Chemical Kinetics
Authors: Hirschfelder Joseph O.
Published: January 2005

In chemical kinetics it is customary to determine the concentrations of each of the free radicals and chemically unstable intermediates by assuming that these intermediates are in pseudostationary equilibrium with the principal chemical components. The mathematical nature of the pseudostationary approximation is examined and a method is developed for testing its validity or improving its accuracy in specific cases. In those cases where the rates of destruction of the intermediate compounds are rapid, the pseudo-stationary solutions are accurate.
Thermodynamic and Transport Properties of the System Iso-Octane and Perfluoroheptane
Authors: Mueller Charles R. , Lewis James E.
Published: January 2005

While there are many experimental measurements on binary liquid systems, very few measurements have been designed specifically for statistical mechanical analysis. This paper describes an effort to design a series of experiments to secure all necessary information for theoretical analysis. The necessary measurements are those of vapor pressure, heats of mixing, variation of density with composition, and measurements of the viscosities of mixed vapors. This system of experiments is used on the system perfluoroheptane and iso-octane. The analysis of the data is discussed and calculations of the thermodynamic properties and intermolecular potential are carried out.
Role of Collision Transfer in Fluorescent Solutions
Authors: Hardwick R.
Published: January 2005

The importance of energy transfer by collision (used in the sense of diffusion together of an excited and an unexcited molecule) has been investigated by measuring the fluorescence of nearly identical solid and liquid solutions under like conditions. Since the solids seem to transfer as well as the liquids, the conclusion is made that the ``collision'' mechanism does not play a major part in this type of transfer.
Infrared and Raman Spectra of Vanadium Oxytrichloride
Authors: Miller Foil A. , Cousins Lauren R.
Published: January 2005

The infrared and Raman frequencies of liquid VOCl3 (of symmetry C3v) have been measured. The a1 fundamentals are 1035, 408, and 165 cm—1; those of species e are 504, 249, and 129 cm—1. Most of the fifteen remaining bands can be explained as combinations of these.
Equivalent Orbital Bond Moments: Applications to Carbon Dioxide and Water
Authors: Hamilton Walter C.
Published: January 2005

Self-consistent field molecular orbitals for CO2, H2O and the B2H4 skeleton of diborane have been transformed into equivalent orbital representations, and bond moments have been defined as the dipole moments of the corresponding equivalent orbitals. If a maximum localization criterion is imposed and if hybrid moments (atomic dipole terms) on central atoms are omitted, one obtains moments of 2.6D(C+O—) in CO2, 1.4D(O—H+) in water, and 2.03D(B2+H—) in a line perpendicular to the B–B bond in diborane. The treatment of water does not seem to allow a separation of well-localized bond and lone-pair moments with the proper directional properties. The bond moment of C–H in methane, according to these criteria, is 0.6D(C—H+). It is concluded that the method is a valid approach to the problem of nonempirical calculation of bond moments in polyatomic molecules.
Spectroscopic Studies of Rotational Isomerism in Fluorinated Ethanes. III. CF2Cl–CF2Cl and CF2Br–CF2Cl
Authors: Kagarise R. E.
Published: January 2005

The phenomenon of rotational isomerism has been studied in CF2Cl–CF2Cl and CF2Br–CF2Cl by observing the temperature and state dependence of their infrared absorption spectra in the 2–18 μ region. In CF2Cl–CF2Cl, the trans-isomer persists in the crystalline solid, and is also the more stable form in the liquid and vapor states. The energy difference between the trans (C2h) and gauche (C2) forms in the vapor was observed to be 500±200 calories/mole.

In CF2Br–CF2Cl, the selection rules for the two probable isomeric species (Cs and C1) are not sufficiently different to facilitate a direct determination of the symmetry of the form which persists in the solid state. However, a comparison of the infrared spectrum of CF2Br–CF2Cl with those of CF2Cl–CF2Cl and CF2Br–CF2Br indicates that the persistent isomer is the pseudo-trans-form (Cs symmetry). This trans-form is also the more stable isomer in both the liquid and vapor phases, the energy difference being 520±200 and 600±200 calories/mole, respectively.
Activation Energy of the Eyring Theory of Liquid Viscosity and Diffusion
Authors: Collins F. C.
Published: January 2005

The determination of the activation energy of the Eyring viscosity and diffusion theory from the isobaric temperature coefficient of the transport property is shown to be inconsistent with the assumed mechanism of the process. An alternative form of the Eyring theory makes use of an activation energy determined from the constant volume temperature coefficient of the transport property. Here the calculated viscosities and their isobaric temperature coefficients turn out to be in moderately satisfactory agreement with experiment in the case of several simple liquids.
Infrared Spectrum of Carbonyl Sulfide
Authors: Allen Harry C. , Plyler Earle K. , Blaine L. R.
Published: January 2005

Fourteen bands of carbonyl sulfide have been observed between 1 and 5.5 μ. The rotational fine structure of the bands has been analyzed and the values of the molecular constants determined. From the average ΔF2 values of the 8 best bands, B0=0.20288±0.00002 cm—1 and D0=(4.08±0.52)×10—8 cm—1, in excellent agreement with the microwave determinations. Several constants in the quadratic expression for the vibrational energy are evaluated, but Fermi resonance between levels of the type (v1,v2l,v3) and (v1 — 1, v2l+2, v3) rule out a complete determination from the presently available bands. It is shown that the previously suggested Fermi resonance between v3 and 4v20 is so small that it is not detected in this work.
Microwave Dielectric Measurements in Liquid Crystals
Authors: Carr E. F.
Published: January 2005

The real and imaginary parts of the complex dielectric constant of the liquid crystal and normal liquid phases of anisaldazine and a mixture of p-azoxyanisole and p-azoxyphenetole have been measured at a frequency of 14 400 Mc. The presence of a static magnetic field produces large changes in the observed values of the complex dielectric constant, which depend on the orientation of the magnetic field and on the temperature.
Comparison of Methods for Computing Bond Orders and Electron Densities
Authors: Burr John G.
Published: January 2005

The molecular orbital energy levels, charge distributions, and mobile bond orders for o-, m-, and p-toluidine in the ground state have been evaluated by three procedures: (1) the simple semiempirical LCAO with neglect of overlap; (2) the semiempirical LCAO method with one cycle of self-consistency iteration; (3) the semiempirical LCAO with inclusion of overlap integrals. It is observed that all three methods give closely similar values for the bond orders and charge distribution, and it is thus concluded that the simple method is as adequate to obtain these quantities as any of the refined methods. The dependency on the nitrogen Coulomb parameter of the total pi-electron energy, of the energy of highest occupied orbital, of the charge distribution, and of the dipole moment for o-toluidine are reported and compared with the first-order perturbation predictions. These calculations were accomplished on the Oak Ridge electronic computer, ORACLE.
New Approach to the Quantum-Mechanical Analysis of the Electronic Structures of Molecules. The Method of Deformed Atoms in Molecules
Authors: Arai Tadashi
Published: January 2005

A modification of Moffit's method of atoms in molecules is here proposed. In this treatment, the modified atomic functions X are introduced, which are made up from the exact eigenfunctions of atoms modified by correction factors so as to take account of the deformation of atoms in molecules. The advantage of these basic functions X is as follows. Firstly, the difficulty caused by the correlation energy in atoms can be removed by the use of the experimental atomic term values just as in Moffitt's method. Secondly, the common effective charges for neutral and ionic structures can be applied for the convenience of calculating the interaction operators, which sometimes produces serious errors in Moffitt's method. Moreover the improvement on the original Heitler-London treatment—corresponding to Wang's or Weinbaum's work for the hydrogen molecule—can be expected. Then, it is discussed how to determine these modified atomic functions in order that the results appertain to the good range in spite of the rather simple calculation.

The energy loss of atoms in molecules, induced by the deformation, is corrected, and the interatomic interaction energy is calculated by the use of the approximate functions composed of the orbital functions, where the molecular orbital method can be utilized for saving the difficulty of the higher order permutations. Then the unsatisfactory results, obtained in the calculation of Li2 by utilizing the common effective charges in Moffitt's method, are improved.
Theory of Ultrasonic Thermal Relaxation Times in Liquids
Authors: Litovitz Theodore A.
Published: January 2005

The theory of thermal relaxation phenomena in liquids is considered from the standpoint that the mechanism of energy transfer in the liquid is the same as in a gas. This would mean that binary collisions and not cooperative action of the molecules are important. The data on ultrasonic relaxation in CS2 is considered. It is found that values predicted by use of the cell model, proposed for liquids and dense gases, in combination with binary collision theory give values for the pressure and temperature dependence of ultrasonic relaxation times which are in good agreement with experiment. Furthermore excellent agreement is found between the values of the probability of energy transfer per collision found in the liquid and gaseous CS2. It also appears that the Schwarz-Herzfeld theory which has been applied to gases can also be applied to liquids and dense gases. It is concluded that the mechanism of energy transfer in thermal relaxation is not affected by the change in state from gas to liquid.
Experimental Determinations of Charge Transfer Cross Sections and Secondary Electron Emission by Ion Bombardment
Authors: Ghosh S. N. , Sheridan W. F.
Published: January 2005

The method utilized by the authors for determining charge transfer cross sections has been improved and applied to symmetric and unsymmetric reactions involving the inert gases, N2, H2, CH4, C2H4, C2H6, and C3H8. The cross sections were found to be about 20% higher than the values previously reported. The discrepancy can be explained by the fact that in previous experiments cross sections were determined from net charge measurements without taking full account of the secondary electrons impinging on the plate where the charge transfer ions were collected.

As expected from adiabatic hypothesis, the reactions involving mixtures of gases having nearly equal ionization potentials were found to have maximum cross sections for low-energy ions. The interaction distances were calculated from the observed ion energy for which the cross sections are a maximum.

The method described here can be utilized to determine the secondary electron emission from a metal surface due to ion bombardment. Such determination has been made for a brass surface. Relating the variation of emission with the ion mass and energy, it is found that the emission varies inversely as the square root of the ion mass.
Vibration Spectrum and Heat Capacity of a Chain Polymer Crystal
Authors: Genensky S. M. , Newell G. F.
Published: January 2005

The Born-von Karman model for a chain polymer crystal previously studied by Stockmayer and Hecht is re-examined using only analytic approximations rather than numerical methods. The analytic approach brings out many peculiar properties of the chain polymer model that did not appear in the numerical treatment.

One branch of the frequency distribution g(v) is shown to be proportional to v2 for the smallest values of v, approximately proportional to v32 for slightly larger v, to v½ for still larger v and to v—½ in still a fourth range of small values of v. An accurate graph of g(v) is constructed for the entire range of frequencies using values of the force constants suggested by Stockmayer and Hecht. g(v) is shown to have approximate singularities of a type not anticipated by van Hove in his broad treatment of singularities for general systems. This anomalous behavior results from having strong valence forces resisting the bending of bond angles. A classification and description of various kinds of singularities that may arise for systems with strong valence forces are given in an appendix.
Herzberg Oxygen Bands in ``Air'' Afterglows and the Night Airglow
Authors: Barth Charles A. , Kaplan Joseph
Published: January 2005

The ultraviolet A3Σu+—X3Σ g— oxygen bands have been observed in emission from greenish-white ``air'' afterglows containing 95–98% nitrogen and 2% to 5% oxygen. The afterglows were excited by an electrodeless rf oscillator and examined with a grating spectrograph having an f/2 camera and a dispersion of 30 A/mm. The mechanism of excitation of these bands in the afterglow may be either the reaction N+O3→NO+O2 or the reaction N+NO2→N2+O2. A comparison of the afterglow spectrogram with an ultraviolet night airglow spectrogram shows that bands arising from higher vibrational levels are more intense in the airglow than in the afterglow. Collisional de-excitation can account for the lower vibrational temperature in the laboratory. The atomic nitrogen-ozone reaction also may occur in the chemosphere between 60 and 90 km and may contribute to the excitation of the night airglow Herzberg bands. The atomic nitrogen at this level could come from daylight predissociation of NO and N2 and from the twilight dissociative recombination of ionized NO.
Experiments on the Polarization and Decay of Electrets
Authors: Wiseman G. G. , Feaster G. R.
Published: January 2005

Experiments have been performed to test implications of a two-charge theory of electrets. It was found that the persistent volume polarization of a number of dielectrics can be expressed by analytical functions which are linear in the applied field and exponential in time. The linear superposition of the effects of homocharge and heterocharge is demonstrated for some dielectrics and is shown to be violated for another, Lucite. The heterocharge and homocharge are demonstrated to be different but interacting entities, their interaction being given by the static field equations for a three-layer capacitor. A major cause of electret decay is shown to be the self-depolarization of the electret by its own electric field.
Electrolytic Hydrogen Evolution Kinetics and Its Relation to the Electronic and Adsorptive Properties of the Metal
Authors: Conway B. E. , Bockris J. O'M.
Published: January 2005

A significant correlation between the logarithm of the exchange current density i0 of the electrolytic hydrogen evolution reaction and the electronic work function φ is found for one group of metals. Another group of metals probably having a different relationship is distinguished. The relationship between logi0 and φ is explained as arising from the dependence of heat of adsorption upon φ. The bond strength DMH of the adsorbed hydrogen calculated from Pauling's equation is less than the experimental value, owing to the neglect of the image potential of H at the metal, but parallels the experimental values. DMH is dependent on the work function since the parameters DMM (the metal-metal dissociation energy) and XM (the electronegativity of the metal) are statistically significant linear functions of φ. For the metals Ta, Mo, W, Cu, Ni, Fe, Rh, Pd, and Pt (at high current densities) logi0 increases as the heat of adsorption of H decreases.

The heats of adsorption of H at Hg, Cd, Pb and Tl are low compared with the values for other metals having respectively similar work functions and the distinct relation, having a different direction, between logi0 and φ for these metals is explained.

Logi0 increases linearly with increase of d character for the metals Mo, W, Cu, Ni, Fe, Pd, and Rh. The correlation coefficient is 0.62. The relation to d character arises since the d character determines the heat of adsorption of H.

The usually observed Tafel slope of 0.12 is consistent either with the rate determining reactionH3O·+e0−+M→MH+H2Oor H3O++MH+e0−→H2+M+H2O.If A is rate determining, i0 should increase with increase of the heat of adsorption of H; if B, the converse should occur. Hence, B is rate determining in acid solution for the metals, Cu, Ni, W, Mo, Ta, Fe, Pd, Rh, Pt (high current density) and A for the metals Hg, Tl, and Pb. The available stoichiometric number data support this conclusion, which implies that during steady evolution of hydrogen, a maximum coverage of the metal by adsorbed H occurs under the condition that the electrode is in contact with liquid water. A general theory of electrolytic reduction and electrode poisoning is given. A mathematical analysis of the dependence of the rate of the proton discharge reaction in terms of the heat of adsorption of H, MH bond force constants, and internuclear distance, is given.
Chemical Bond: A One-Dimensional, Square Well-Type Model
Authors: Barrow Gordon M.
Published: January 2005

A suitable bonding atomic orbital is generated by a square well potential bounded by an infinite potential on one side and a constant finite potential on the other side. The bonding electrons of a σ bond are described in a similar double well potential. With a choice of the potential well dimensions and an electron repulsion term the electronic energy is calculated for various approximate wave functions.

For a heteronuclear bond the potential wells are given different depths. The additional energy and the ionic character are obtained. Comparison with the usual electronegativity scale and ionic character relations shows that this simple model reproduces the principal features of a σ bond.
Proton Magnetic Resonance of Solid Sym-Tetrachloro and Tetrabromoethane
Authors: Takeda M. , Gutowsky H. S.
Published: January 2005

The proton magnetic resonance line shapes have been observed in solid sym-tetrachloroethane and sym-tetrabromoethane. The second moments of the absorption lines provide unambiguous assignments of the molecular forms. The results confirm the formation by CHBr2CHBr2 of crystals of either trans- or of gauche-molecules, depending upon thermal treatment, with the trans-crystals stabler at low temperatures. Only the gauche-form of solid CHCl2CHCl2 could be prepared.
Raman and Infrared Spectra of 2-Thiabutane
Authors: Hayashi Michiro , Shimanouchi Takehiko , Mizushima San-ichiro
Published: January 2005

Raman spectra of 2-thiabutane have been measured in the liquid and crystalline states. Infrared spectra of these substances have been recorded in the vapor, liquid, and crystalline states. The skeletal frequencies for different rotational isomers have been calculated by the use of a potential function of the Urey-Bradley type. It was concluded that in the gaseous and liquid states there exist both the trans and gauche isomers, of which only the former persists in the crystalline state. These two rotational isomers have been found to have nearly the same energy in the gaseous and liquid states.
Viscoelastic Theory of Branched and Cross-Linked Polymers
Authors: Ham Joe S.
Published: January 2005

A model of polymer chain motions is developed which in the limit of long, flexible chains can readily be applied to branched chain and cross-linked systems. The equation governing the motion of a chain takes the form of a differential equation rather than the form of the large set of difference equations that occur in most other treatments. The present model gives essentially the same distribution of relaxation times for linear polymers as previous treatments, and it also gives the same dependence of viscosity upon branching as the theories based on the effective radius of randomly coiled chains.

In addition to this information, the theory yields the distribution of relaxation times for branched chain polymers, permitting, for example, the calculation of the energy stored in steady state shear. The relaxation time distribution of several models of a cross-linked polymer is also calculated, and the relationship of this distribution function to that of the uncross-linked materials is discussed.
Dissociation Energies of Carbon Monoxide and Nitrogen from Reflected Shock Wave Studies
Authors: Toennies J. P. , Greene E. F.
Published: January 2005

Reflected shock velocities have been measured in pure nitrogen, pure carbon monoxide, dilute mixtures of these gases in argon, and in pure argon. The results agree well with the calculations based on the dissociation energies, D(N2) = 9.76 ev and D(CO) = 11.1 ev; but not with D(N2) = 7.38 ev and D(CO) = 9.14 ev. An acceleration of the reflected shock in nitrogen and carbon monoxide is attributed to vibrational relaxation in the incident shock. Although some deviations from ideal behavior due to energy and momentum losses are shown to be present, the results indicate that equilibrium is very nearly attained, and that shock tube measurements can provide useful high-temperature thermodynamic information.
Lattice Dynamics of Body-Centered and Face-Centered Cubic Metallic Elements. III. Cubic Invariant Polynomials
Authors: de Launay Jules
Published: January 2005

When the frequencies obtained from the secular equations of lattice dynamics are expressed as power series in the magnitude of the propagation vector, the coefficients of the series terms are polynomials in the direction cosines of the vector. These polynomials are invariant under the symmetry operations of the cube. A number of their properties which have proved to be of value in computations of the lattice spectrum are presented.
Microwave Spectrum and Structure of Propionitrile
Authors: Lerner R. G. , Dailey B. P.
Published: January 2005

Rotational transitions of several isotopic species of propionitrile have been observed. This has permitted a determination of the structural parameters of the molecule. For C2H5C12N, B=4714.00 Mc, C=4235.07 Mc and for C2H5C13N, B=4689.77 Mc and C=4214.87 Mc. For CD3CHDC12N, B=4169.43 Mc and C=3736.83 Mc. The following model reproduces these constants to within 1.5 Mc : rC–C=1.5479 A (ethyl), rC–C=1.4735 A (nitrile), rC=N=1.1566 A, rC–H=1.0914 A, ∠CCC=110°32′, ∠HCH=109°19′. The height of the barrier to internal rotation has been estimated to be 1150±100 cm—1 or 3280±290 cal/mole for a torsional frequency of 226 cm—1.
Equation of State for Water at Extreme Pressures
Authors: Rosenbaum J. H.
Published: January 2005

A new equation of state for water is derived from theoretical considerations. This is used to obtain a smoothed extrapolation of Bridgman's P-V data to extremely high pressures.
Microwave Spectrum and Structure of Sulfuryl Fluoride
Authors: Lide David R. , Mann D. E. , Fristrom R. M.
Published: January 2005

The microwave spectrum of sulfuryl fluoride, SO2F2, has been reinvestigated. The spectra of the S32 and S34 species in natural abundance have been analyzed, and the structure has been determined with the aid of the S34 isotope shift. The correction for zero-point vibration was shown to be small. The structural parameters are: rSO=1.405±0.003 A, rSF=1.530±0.003 A, <OSO=123°58′±12′, and <FSF=96°7′±10′. The molecular dipole moment is 1.110±0.015 Debye units. A number of satellite lines were observed and assigned to excited vibrational states. Some anomalies in the measured rotational constants for the excited states have been interpreted in terms of a Coriolis-type interaction between the fundamentals ν4(A1) and ν5(A2). From an analysis of this interaction the frequency of the hitherto unobserved ν4(A1) fundamental was found to be 388±15 cm—1.
Infrared Spectrum of Solid Nitrous Oxide
Authors: Dows David A.
Published: January 2005

The infrared spectrum of solid nitrous oxide has been obtained at 80°K. Several bands due to isotopic species are seen. In contrast with CO2, no evidence is observed for splitting due to intermolecular coupling or for reflection peaks in the spectrum. Spectral features assigned to torsional lattice motions (with fundamentals at 80 and 91 cm—1) and to translational lattice motions (as broadening of v3) are present.
Solubility of Hydrogen and Deuterium in Nonpolar Solvents
Authors: Cook M. W. , Hanson D. N. , Alder B. J.
Published: January 2005

Data are presented for the solubility of hydrogen and deuterium in eight nonpolar solvents from —25°C to 35°C, and show that deuterium is about 2.5% more soluble. The data are accurate to 0.1% and correlate successfully with the solubility parameter of the solvent. The various thermodynamic functions are calculated.
Lattice Dynamics of Hexagonal Close-Packed Metals
Authors: Slutsky L. J. , Garland C. W.
Published: January 2005

The lattice dynamics of hexagonal close-packed metals has been investigated, the assumption being made that the atoms interact with central forces. Atomic force constants are related to the elastic constants by the method of homogeneous deformation in which the contribution of the electron gas to the elastic constants is assumed to arise from an isotropic volume-dependent term in the energy. Relations are given for the propagation of acoustical waves in hexagonal crystals which permit calculation of the elastic constants from ultrasonic pulse velocity measurements.
Mayer's Treatment of Ionic Solutions
Authors: Meeron Emmanuel
Published: January 2005

Mayer's expressions for the ionic activity coefficient and osmotic pressure of an electrolyte solution are shown to involve known and accurately tabulated functions. Mayer's infinite series of integrals is summed to give a single integral involving the Debye-Huckel potential of average force. With the help of the new form, the use of the single cut-off parameter for binary electrolytes is discussed from a quantitative standpoint.
Relationship between Atomic and Ionic Radii
Authors: Somayajulu G. R. , Palit Santi R.
Published: January 2005

It has been found that the van der Waals volume (Rv3) is directly proportional to the atomic surface area (Rc2) for electronegative elements. The volumes of the negative ions have also been found to be similarly related to the square of their atomic radii, but the relation is restricted to the same group of the periodic table. The positive ion radii of the alkali and the alkaline earth metals have also been found to be linearly related to their metallic radii.
Interrelations of Quantum-Mechanical Quantities Concerning Chemical Reactivity of Conjugated Molecules
Authors: Fukui Kenichi , Yonezawa Teijiro , Nagata Chikayoshi
Published: January 2005

It is attempted here to disclose the interrelations underlying the parallelism found in several quantum-mechanical methods previously proposed to explain chemical reactivity in conjugated molecules. This is carried out mathematically in alternant hydrocarbons and hetero-alternant molecules mainly by the use of Coulson's integral formulas. In an alternant hydrocarbon, provided a condition is satisfied between minors of the secular determinant, the orders of reactivity of each position predicted by the self-polarizability, free valence, superdelocalizability, Wheland's localization energy, and Dewar's approximate localization energy by NBMO are shown to be in complete agreement with one another. The relation of the frontier electron density and superdelocalizability is discussed. It is also demonstrated that a nonperturbation treatment for the so-called static method leads us to the same conclusion as the perturbation treatment. The parallelism of various quantities is discussed in their relation to the effect of heteroatom in heteroalternant molecules.
Polymeric Gaseous Species in the Sublimation of Molybdenum Trioxide
Authors: Berkowitz J. , Inghram Mark G. , Chupka W. A.
Published: January 2005

Mass spectometric analysis of the vapor in thermodynamic equilibrium with powdered molybdenum trioxide, as sampled from a Knudsen effusion cell, has shown that the vapor phase consists predominantly of Mo3O9, Mo4O12 and Mo5O15 molecules. Utilizing the Clausius-Clapeyron equation, individual heats of sublimation have been determined to be 80.5±1.5, 93.6±1.6 and 105.6±3.5 kcal/mole respectively at 850° K. The heats of formation and third law entropies have been evaluated for each of these molecules.