bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Frequency Vibrations of Crystalline Biphenyl
Authors: Krebs Karlheinz , Sandroni Santino , Zerbi Giuseppe
Published: January 2005

The spectrum of inelastically scattered slow neutrons has been obtained for polycrystalline biphenyl. Whereas translational modes account for the broad general features of the whole spectrum, the fine structure observed can be interpreted in terms of librational and q-independent internal modes. The six theoretically predicted librations have been assigned. Moreover, one has good reasons to believe that the torsional internal mode, practically inactive in infrared and Raman, occurs in the INS spectrum at about 70 cm—1.
Theory of Subexcitation Electron Scattering by Molecules. I. Formalism and the Compound Negative-Ion States
Authors: Chen Joseph C. Y.
Published: January 2005

The problem of slow-electron scattering by molecules is treated formally with explicit consideration of the possible effects of the compound negative-ion states. The formulation is based on the treatments for nuclear reactions and scattering, in particular the unified treatment recently advanced by Feshbach. The transition matrix for both direct and resonance scattering, describing the excitation of the nuclear motion of the target molecule, is obtained. The influence of the compound negative-ion states on the equivalent scattering potential for resonance scattering is investigated in some detail.
Mass Spectrometric Study of the Vaporization of Uranium Monophosphide
Authors: Gingerich Karl A. , Lee Peng Kei
Published: January 2005

The vaporization of uranium monophosphide, UP, and its mixtures with uranium oxide, UO2, have been investigated by Knudsen effusion techniques in combination with a mass spectrometer.

The vaporization of UP occurs by decomposition according to UP(s)=U(g)+(1/x)Px(g)      (x is either 1 or 2).If UO2 is present approximately in equimolar ratio with UP the principal reaction is according to UP(s)+UO2(s)=2UO(g)+(1/x)Px(g)    (x is either 1 or 2).The partial pressures of P, P2, and U over UP have been obtained from the silver calibration for the temperature range of 1750°—2250°K. The temperature dependence of logKp for Reaction (1), where x=1 was determined to be the following: logKp=−(54888/T)+14.6056±0.1392.From the second-law treatment, the heat of vaporization in kcal/mole of UP is obtained for Reaction (1) as 251.17±4.88 when x=1.

Vapor pressures derived from other methods, such as (a) from known dissociation energy of P2 and thermodynamic functions of P and P2, and (b) from the amounts of sample evaporated are discussed.
Excitation Migration in One-Dimensional Molecular Random Lattices
Authors: Katsuura Kanji
Published: January 2005

Migration of electronic excitation energy is studied in two types of one-dimensional random lattices, one whose chains consist of identically oriented but randomly spaced molecules, and one with equally spaced but randomly oriented molecules. Results of computer calculations show that the loss of periodicity suppresses migration of excitation and that the velocity of migration is not constant but a decreasing function of time.
Interaction Energies, Charge Exchange Cross Sections, and Diffusion Cross Sections For N+–N and O+–O Collisions
Authors: Knof Hans , Mason E. A. , Vanderslice J. T.
Published: January 2005

Potential energy curves for the lower electronic states of the N2+ and O2+ molecules have been obtained from a semiempirical valence bond method which makes use of available spectroscopic data. From these curves the probability of charge exchange has been calculated, and from this the charge-exchange and diffusion cross sections. The cross sections for the O+–O collisions are in good agreement with the experimental values of Stebbings, but differ by about a factor of 3 from earlier theoretical estimates. Some consequences of this are discussed.
Atomic Emission of the Helium Afterglow
Authors: Niles Franklin E. , Robertson W. W.
Published: January 2005

The spectral emission from a dc pulsed helium discharge for pressures from 5 to 20 Torr has been investigated during the early afterglow using interference filters with gated photomultiplier. The radiation transmitted by the filters consists generally of both atomic lines and molecular bands and after the termination of the active discharge shows characteristically an initial rapid decrease in intensity followed by a much slower rate. The rapid decrease is due to the atomic radiation, the slower to molecular. By subtracting the molecular emission from the total emission transmitted through an interference filter, the atomic emission is obtained. From the decay curves of the atomic emission, which is the result of collisional-radiative recombination of He+, and the known diffusion loss of He+, the rate of conversion of He+ into He2+ is found to be 109±6 sec—1·Torr—2.
Atomic-Beam Scattering from Epitaxially Grown Gold Films
Authors: Smith Joe N. , Saltsburg H.
Published: January 2005

The spatial distribution of beams of He and Ar scattered by gold-target films was examined mass spectrometrically during and after the formation of these films by evaporative deposition. By controlling the target temperature during the deposition of the metal, varying degrees of crystallographic orientation and surface smoothness were obtained. The metallic deposition rate was maintained high as compared with the impingement rate of background gas particles, resulting in approximate clean-surface conditions during deposition. For rough polycrystalline films, only cosine scattering of He and Ar was observed. For smooth, well-oriented films, specular scattering of He was observed during deposition. In this latter case, a gradual time-dependent dispersion in He scattering was seen after deposition and is shown to result from the formation of adsorbed gas layers. For Ar scattered from a smooth gold film during deposition, a broad directed beam, displaced from the specular angle, is obtained, and very little dispersion occurs after deposition. This latter result is interpreted as being due to the greater interaction between Ar and gold, compared with that between He and gold, which masks the effects of adsorbed gases upon Ar scattering.
Octopole Moment of Methane
Authors: Sinai John J.
Published: January 2005

The octopole moment of methane is calculated using three different LCAO—MO—SCF wavefunctions. The numerical method of calculation is illustrated. Results are compared with the experimental value of James and Keenan, as well as the theoretically computed value of Turner et al. who used the one-center-expansion-method wavefunction of Saturno and Parr. A brief discussion of these different wavefunctions and the octopole moments obtained from them is given.
Rough Viscosities to 10 000 Bars
Authors: Babb Stanley E. , Scott Gene J.
Published: January 2005

The viscosities of six fluids have been measured to 10 000 bars at room temperature.
Relation between Self-Diffusion Coefficients and Quantum Equilibrium Properties
Authors: Friedmann H. , Steele W. A.
Published: January 2005

A number of approximate theoretical equations which give the molecular friction constant in terms of the average Laplacian of the intermolecular potential are compared with the experimental data of Naghizadeh and Rice. Values for the average Laplacian are obtained from experimental data on the changes in thermodynamic properties with isotopic substitution in nearly classical fluids. These experimental average Laplacians differ considerably from the values obtained previously by computation from the molecular properties. Although none of the approximate equations is capable of exactly reproducing the experimental data, it is concluded that one of them [Eq. (1) of this paper] gives reasonably accurate values for the friction constants and self-diffusion constants of simple dense fluids.
Partition Functions of Linear-Chain Molecules
Authors: Lifson Shneior
Published: January 2005

A new method is proposed for the derivation of partition functions of linear-chain molecules. It consists of defining sequences, sequence partition functions, and sequence-generating functions and using them to derive an equation for the contribution of each chain element to the partition function of the whole chain. The method has a more general applicability than the combinatorial and matrix methods. Several applications are discussed.
Hyperfine Interactions and Electron Spin Distribution in Triplet-State Naphthalene
Authors: Hirota Noboru , Hutchison Clyde A. , Palmer Patrick
Published: January 2005

The anisotropic proton hyperfine interaction of the triplet-state electrons of the naphthalene molecule have been measured at the boiling point of N2. The naphthalene molecules were oriented in single crystal solid solutions in durene. The effects of various substitutions of D for H were investigated. The spin density distribution deduced from these experiments was ρα=+0.219, ρβ=+0.062, ργ=—0.063. These results were compared with the results of theoretical calculations and with experimental results for the naphthalene negative ion.
Interface Shapes of Nonadiabatic, Steady-State Crystallization
Authors: Berlad A. L.
Published: January 2005

For the case of nonadiabatic, steady-state crystallization in a supercooled liquid, the class of possible interface shapes, consistent with the interface kinetic restrictions, is examined. For transformations obeying isotropic kinetics, the allowed class of crystal—liquid interfaces consists of denumerable combinations of dendrites and cells. For transformations obeying nonisotropic kinetics, certain classes of kinetic laws preclude the satisfaction of a steady-state process. However, other classes of nonisotropic kinetic laws permit a steady-state process. For the latter case, the allowed steady-state interface shapes are of the same class as those permitted for the case of isotropic kinetics.
Infrared and Raman Spectra of Digermane
Authors: Griffiths James E. , Walrafen George E.
Published: January 2005

Infrared spectra of gaseous digermane and of digermane-d6 were recorded under medium resolution from 4000–250 cm—1 and the Raman displacements were obtained photoelectrically from 100–2600 cm—1 for the liquid state. The 12 fundamental frequencies for each molecule were assigned to the normal modes and digermane was shown to have the D3d ethanelike structure.

The rotational structures of the eu fundamentals of Ge2H6 and the ν8 fundamental of Ge2D6 were resolved and analyzed. Results from the zeta sum rule confirmed the hindered rotator structure and four combination bands were used to estimate the barrier hindering internal rotation as 1490±200 cal/mole.
Infrared Spectra of Gaseous Diazomethane
Authors: Moore C. Bradley , Pimentel George C.
Published: January 2005

The gaseous infrared spectra of CH2N2, CHDN2, CD2N2, and CH2N15N have been examined between 230 and 4000 cm—1 under medium resolution. Band positions have been measured for all the distinguishable parallel features. Nearly all of the perpendicular fundamentals have been resolved and analyzed. The [A″—½(B″+C″)] rotational constants derived are: CH2N15N, 8.747±0.015 cm—1; CD2N2, 4.253±0.01 cm—1; CHDN2, 5.72±0.1 cm—1. These data combined with that given earlier for the CH2N2 isotope, show that the averaged distance of the hydrogen atoms from the molecular axis (in CH2N2 and in CH2N15N) is 0.9580±0.0006 Å and of the deuterium atoms (in CD2N2) is 0.9560±0.001 Å.

In contrast to earlier studies, we were able to find no evidence for the presence of a tautomeric form of diazomethane in the samples studied.
Relationship of Electron Spin Resonance and Semiconduction in Phthalocyanines
Authors: Harrison S. E. , Assour J. M.
Published: January 2005

The electron mobility of charge carriers in copper phthalocyanine has been determined to be approximately two orders of magnitude greater than that in metal-free phthalocyanine. This difference can be interpreted in terms of the electron spin resonance results and the intermolecular copper-nitrogen overlap. The electron spin resonance of copper phthalocyanine magnetically diluted in metal-free phthalocyanine has been measured in single crystals. The hyperfine structure of the nitrogen ligands, as well as that of the copper hyperfine structure, is clearly resolved. An analysis of the data in terms of molecular orbitals suggests a scheme of strong out-of-plane π bonding with the π orbitals of the phthalocyanine ring and almost no in-plane π bonding. This brings about an inversion of the usual positions of the copper Eg and B2g orbitals. This strong π bonding predicts that in metallo-organic compounds of this type, the organic π-electron delocalization is increased to include the central metal atom, and properties dependent on this delocalization should be altered when copper is used. The increased delocalization of the π-electron orbitals gives rise to larger intermolecular π wavefunction overlap resulting in a greater mobility for charge carriers in copper phthalocyanine.
Analysis of Calculations on Some Oxygen Hydrides
Authors: Rosenfeld J. L. J.
Published: January 2005

Wavefunctions for OH— and H4O++ are presented in the self-consistent field molecular orbital approximation, using a minimum basis set of Slater-type atomic orbitals. A wavefunction for H4O++ based on a one-center model is also included. A comparison is made, for the isoelectronic series OH—, H2O, H3O+, H4O++ of three methods of calculating molecular energies, namely the two methods already mentioned and a valence bond method.

The changing properties of the OH bond in the series are discussed within the self-consistent field approximation by an analysis of the electron distribution. A good correlation is found between the bond strength and the maximum in the bond of the δ function first introduced by Roux.
Origin of OH Chemiluminescence during the Induction Period of the H2–O2 Reaction behind Shock Waves
Authors: Belles F. E. , Lauver M. R.
Published: January 2005

The intensity and the rate of increase of light emitted by the OH* 2Σ+→2II(0–0) transition were studied during the induction period behind shock waves in 5% H2—95% air mixture. Induction-zone temperatures ranged from about 1000° to 1900°K, and the initial pressure was 10 Torr. A standard lamp was used to calibrate the optical system, so that photomultiplier signals could be transformed to OH* concentration. The results are interpreted in terms of radical-recombination reactions. It is found that OH* is formed in the reaction H+O2+H2→H2O+OH* and is effectively quenched, in these experiments, only by water. The excitation process is an inefficient reaction, with an average rate constant of 2×105 liter2/mole2·sec.
Mössbauer Isomer Shifts of Ferrous Phenanthroline and Related Complexes
Authors: Epstein L. M.
Published: January 2005

The center shifts at liquid-nitrogen temperature of a number of substituted phenanthroline complexes fell in a rather narrow range from about 0.50 to 0.53 mm/sec with a trend to larger values for the more electron-withdrawing substituents. Among the other ferroin-type complexes, the two with nonaromatic ligands had appreciably larger center shifts than the aromatics. The nonbridged aromatic ligands all gave smaller center shifts than the phenanthrolines suggesting greater covalency. In most cases the temperature dependence of the center shift was anomalously small, and several possible causes of this are suggested.
Neutron Diffraction Refinement of CaWO4
Authors: Kay M. I. , Frazer B. C. , Almodovar I.
Published: January 2005

The CaWO4 structure has been refined, starting with the parameters of Sillén and Nylander, using two zones of neutron diffraction data. The oxygen coordinates with the origin of the cell at the W atom (4̄) are x=0.2413 (σ=0.0005), y=0.1511 (σ=0.0006), z=0.0861 (σ=0.0001). The slightly distorted WO4 tetrahedron contains a W–O distance of 1.788 Å (σ=0.003) and angles of 113° 27′ (σ=14′) and 107° 56′ (σ=0.09′). Close nonbonded approaches are Ca–O=2.48 Å and O–O=2.77 Å. Anisotropic thermal vibration parameters were also determined.
Lattice Dynamics of α Mercury
Authors: Slutsky L. J. , Jelinek G. E.
Published: January 2005

The frequency distribution spectrum and constant-volume heat capacity are computed for a model of a monatomic rhombohedral crystal. Interactions between an atom and its nearest and second-nearest neighbors are considered. The interatomic force constant are evaluated from the elastic constants of mercury.
Resonance Interaction between Degenerate Electronic States: Derivation of the Vibronic Equation
Authors: Witkowski Andrezej
Published: January 2005

The vibronic Hamiltonian describing the resonance interaction between the doubly degenerate electronic states of two identical molecules is derived. The totally symmetric and Jahn—Teller active vibrations of each molecule are simultaneously coupled with electronic motions by the resonance interaction and are separable from each other only in limiting cases.
Initial Preparation and Metastable Transitions in Mass Spectra
Authors: Rosenstock H. M. , Dibeler V. H. , Harllee F. N.
Published: January 2005

By variation of initial preparation of the reacting species, the detection of nonequilibrium kinetic effects is discussed for unimolecular ionic decomposition processes occurring in the mass spectrometer. A particular example, dependence of the rates of competing metastable transitions of hexyl ions on mode of preparation is studied in detail. The hexyl ions were prepared by electron impact ionization and decomposition of a variety of normal alkanes, n-hexyl bromide and di-n-hexyl ether. At low electron energies (30 eV) the ratio of the competing metastable transitions is constant within experimental error. This supports the applicability of the quasiequilibrium theory of mass spectra to such processes. At higher electron energies there is a slight dependence of the ratio on parent ion mass.
Spin Properties of Pair-Correlated Atomic and Molecular Singlet Wavefunctions
Authors: Levine Howard B. , Geller Murray , Taylor Howard S.
Published: January 2005

The recent work of Sinanoğlu upon pair-correlated wavefunctions is considered. We derive the conditions required for his wavefunction to be a spin singlet, and then relate these conditions to his theory. In particular, we show them to be satisfied to an approximation consistent with those used in deriving his ``exact pair'' theory. An error in the original integral breakdown is also pointed out and shown to have little effect on the results of the theory.
Off—Diagonal Hypervirial Theorem and Its Applications
Authors: Chen Joseph C. Y.
Published: January 2005

A hypervirial operator, by definition, is a time-independent linear operator with an arbitrary functional structure expressed in terms of the dynamical variables of the system under consideration. In the energy representation, the diagonal matrix elements of the hypervirial operator are constant in time; this is known as the hypervirial theorem. The off-diagonal matrix elements of the hypervirial operator in the energy representation oscillate in time with frequencies related to the energy differences between their corresponding stationary states of the system. This is known as the off-diagonal hypervirial theorem.

The latter theorem is as powerful as the former for dealing with many quantum-mechanical problems. Several aspects of the possible applications of the theorem to the problem of construction and improvement of wavefunctions are considered. As a special example, the restricted fourth alternative expression for dipole transition matrix elements is derived for pair functions not belonging to states with zero orbital angular momentum. A scheme is also outlined for improving wavefunctions of the excited states. The statistical implications of the sum rule, which is expressed in terms of an appropriate hypervirial operator, are discussed in connection with uncertainty principles.
On the Relaxation of the Hard—Sphere Rayleigh and Lorentz Gas
Authors: Andersen Knud , Shuler Kurt E.
Published: January 2005

As part of a study of the relaxation of nonequilibrium systems, the (translational) relaxation of a hardsphere Rayleigh and Lorentz gas is investigated. From a detailed analysis of the collision dynamics an exact expression is derived for the kernel A (x | x′) of the collision integral which gives the probability per unit time for a change of the reduced kinetic energy from x′ to x during a binary collision between a subsystem and a heat bath particle. A master equation, i.e., a linearized Boltzmann equation, incorporating this kernel is then formulated to represent the time variation of the distribution function of the subsystem particles. Making use of the special property of this kernel that it is a strongly peaked function around x—x′=0 for both the Rayleigh and Lorentz gas, a technique is developed for transforming this integral master equation into differential Fokker—Planck equations consistent in the order of the expansion parameter λ, the ratio of the mass of the heat bath particles to the subsystem particles. The Fokker—Planck equation for the Rayleigh gas is solved analytically and explicit solutions are presented for the relaxation of initial Maxwell and initial δ-function distributions of the energy. It is shown that an initial Maxwell distribution of the energy (or speed) of the subsystem particles relaxes to the final equilibrium Maxwell distribution via a continuous sequence of Maxwell distributions. The mean energy of the subsystem particles is shown to relax exponentially to its equilibrium value independent of the form of the initial distribution. For the hard-sphere Lorentz gas the Fokker—Planck equation is not susceptible of an analytical solution. Machine solutions are presented for various initial distributions which show that the Maxwell distribution is not preserved in the relaxation of the hard sphere Lorentz gas. Finally, a brief discussion is given of the relation between the hard-sphere model (r—∞) considered here and the more general model of the Rayleigh and Lorentz gas with a r—8 repulsive central force law.
Surface-Limited Vapor Solvent Growth of Crystals
Authors: Mandel Gerald
Published: January 2005

A general analysis is presented of surface reaction limitations in a vapor solvent system. A previous treatment of a multicomponent multireaction vapor diffusion limited system is extended to include finite supersaturations in the neighborhoods of the growing deposit and the etching source. The appropriate natural definitions of supersaturations are found to be in agreement with the usual conventions of irreversible thermodynamics.

A more detailed connection between the supersaturations above a growing crystal and the growth rate of the crystal is developed by means of an extension of the crystal growth theory of Burton, Cabrera, and Frank to apply to a multiple species multireaction vapor solvent system. It is found, at least in the limit of low supersaturations, that the flux of any particular species to the surface may be treated in terms of the formalism developed by Burton, Cabrera, and Frank for a monatomic crystal—monatomic vapor system, except that some of the parameters which characterize the process, e.g., diffusion length on the surface, lifetime on the surface, etc., have more phenomenological character. Relationships between the fluxes of different species are developed in the same manner as in the previously treated vapor diffusion limited system.

Quantitative calculation of the important parameters is apparently impossible in our present state of knowledge of surface processes. Qualitatively, we expect surface diffusion effects to be far more important than in simple crystal—vapor systems. Other effects, however, are also expected to be important in vapor solvent systems, e.g., ``kink-reaction'' limitations, impurity effects, etc. Disentanglement of these several processes is an unsolved problem and it is concluded that detailed quantitative understanding of surface-limited crystal growth in a vapor solvent system is presently out of reach.
Solvation Approach* to Ion Solvent Interaction
Authors: Padova J.
Published: January 2005

From the hard-sphere model proposed, i.e., that the ion and its solvation layer are incompressible, and from density and compressibility data, the variation of solvation number with concentration, the intrinsic volume of ions, and the mean distance of approach are obtained. These properties of the ions, and the molar refractions, the dipole moment of the ion pair, and the viscosity, are correlated via the solvated molar volume φ8.
Spectra Excited in a Helium Afterglow
Authors: Collins C. B. , Robertson W. W.
Published: January 2005

The selective excitation of spectra by collisions of the second kind with active helium species was examined in a flowing helium afterglow. Techniques for titrating for the active species in the afterglow are described. Conditions under which the metastable atom He(23S), the atomic ion He+, or the molecular ion He2+ predominate in the burner are found and the spectra excited by each are listed.
Use of Field-Sweep Double Resonance in the Unambiguous Analysis of Three-Spin Spectra
Authors: Whipple E. B. , Chiang Y.
Published: January 2005

A systematic procedure for uniquely determining NMR parameters from a spectrum is applied to the case of three coupled spins, and several examples are treated. The analysis involves three steps: (1) use of frequency sum rules to determine consistent assignments; (2) removal of ambiguities in assignment by field-sweep double resonance; and (3) iterative refinement of arbitrary initial parameters.
Effect of Light Molecules on Vibrational Relaxation in Oxygen
Authors: Shields F. D. , Lee K. P.
Published: January 2005

Sound absorption and velocity measurements have been made in O2 with added amounts of H2, D2, and He. The number of collisions Z10(AB) necessary to de-excite the first vibrational state of O2 has been calculated from the measured relaxation times. At 100°C: Z10(O2–H2)=2.0×104, Z10(O2—D2)=2.5×105. At 200°C: Z10(O2–H2)=1.1×104, Z10(O2—D2)=1.5×105, Z10(O2–He)=6.8×104. At 300°C: Z10(O2–He)=3.6×104. These values are in general agreement with values reported by Parker; by Holmes, Smith, and Tempest; and by White and Millikan. When logZ10(AB) is plotted vs the cube root of the reduced mass times the square of the vibrational frequency divided by the absolute temperature, a linear relationship is found between the O2–H2 and the O2–He data. However Z10(O2—D2) is unexpectedly larger than Z10(O2–He). When the collision numbers Z10, for pure O2 and N2, are plotted in this way they fall along a single curve.
Symmetry Coordinates and Lattice Vibrations of LaCl3
Authors: Murphy J. , Caspers H. H. , Buchanan R. A.
Published: January 2005

Symmetry coordinates for the 24k=0 modes of LaCl3 are derived. These symmetry coordinates form a basis in terms of which the normal modes are expanded. From a group theoretical analysis of the C6h2(p63/m) space group, it is determined that there are three infrared-active (1A1u and 2E1u), six Raman-active (2A1g, 1E1g, and 3E2g), and five nonactive (2Bg, 2Bu, and 1E2u) vibrational modes. Three infrared absorption bands were observed in evaporated LaCl3 films at 138, 165, and 210 cm—1. Three force parameters were determined using the wavenumbers of the infrared-active modes. The wavenumbers of the other modes were expressed as functions of the fourth force parameter. For one value of this parameter, agreement with the observed Raman lines was obtained with an average deviation of 6.6 cm—1.
Association in Biradical Solutions
Authors: Waring R. K. , Sloan G. J.
Published: January 2005

The effects of temperature and optical irradiation upon the intensity of the electron paramagnetic resonance of Chichibabin's hydrocarbon [4,4′-bis(diphenylmethyl)biphenyl] and related compounds have been studied. Relative intensities were determined by employing a field modulation amplitude sufficient to remove all structure and measuring first moments of the resultant derivative spectrum. It has been found that the room-temperature intensity can be maintained at low temperatures if the specimen is cooled rapidly enough. Further, the intensity can be enhanced by optical irradiation at —100°C. These effects are reversible, but a number of related irreversible effects also occur. The results suggest that the observable paramagnetic species in biradical solutions is a dimer or higher polymer of Chichibabin's hydrocarbon. As a result, the interaction between the unpaired electrons of the biradical is much smaller than would be expected for a monomer.
Energy Terms of ZnS:Tm and Ho
Authors: Ibuki S. , Langer D.
Published: January 2005

The absorption and emission spectra of ZnS:Tm3+ and Ho3+ were observed at 4.2°, 77°, and 290°K between 3400 and 9000 Å by using a high-dispersion spectrograph. The L—S coupling terms of Tm3+ and Ho3+ were determined and the spin—orbit interaction term ζ and the Slater integral F2 were estimated for Tm to be 2702 and 440 cm—1, respectively. Also the crystal field splitting terms and the pressure dependence of absorption and emission are discussed in this paper.
Anisotropic Hyperfine Interaction of Cr53 in Chromium (III) Acetylacetonate
Authors: McGarvey B. R.
Published: January 2005

The ESR spectra of chromium (III) acetylacetonate in single crystals of cobalt (III) acetylacetonate and aluminum acetylacetonate were studied. In cobalt (III) acetylacetonate the spin Hamiltonian constants were found to have the values: g=1.9802±0.0005; | D |=0.600±0.001 cm—1; and | E |=0.0085±0.0005 cm—1. In addition the outer two components of the hyperfine spectra due to Cr53 was observed giving the values: | A | = (16.2±0.1)×10—4 cm—1 and | B |=(16.9±0.1)×10—4 cm—1. The resonance lines in the aluminum acetylacetonate host crystal were found to be broader, yielding less reliable but similar values for the spin-Hamiltonian constants. It is shown that the anisotropy in the hyperfine interaction can be explained by assuming the molecule to be slightly compressed along the trigonal axis.
Dissociation Energy of the CH Radical
Authors: Brewer Richard G. , Kester Frank L.
Published: January 2005

The 4300-Å band of CH has been observed in emission using a carbon furnace above 2400°C which contains 1 atm of H2 gas. From the CH emission intensity variation with temperature and a thermochemical cycle involving the heat of sublimation of graphite, a CH dissociation energy of 80±5 kcal (3.5±0.2 eV) is derived for the 2Π state. The close agreement between this value and that obtained previously from a CH rotational predissociation, establishes not only that the CH dissociation energy is 80.0 kcal (3.47 eV) but further confirms that the heat of sublimation of graphite is 169.58 kcal. For this 2Π state the atomic dissociation products are identified experimentally as ground-state C(3P) and H(2S) atoms. In addition, for the process C2H2=2CH an acetylene dissociation energy of 228.1 kcal is derived.
Specific Ionic Effects on Reaction Rates. The Reaction between Persulfate and Iodide Ions in the Presence of High Concentrations of Added Salts
Authors: Perlmutter-Hayman B. , Stein Gabriel
Published: January 2005

The effect of added electrolytes (up to 2M) on the reaction between persulfate and iodide ions was reinvestigated, utilizing the absorption of I3— in the near ultraviolet to follow the reaction. The effect could be represented very well by the empirical relation logk=logk0+[Ac/(B+c)]+Dcover the entire range, where A, B, and D are constants specific for the cation (uni-, di-, or trivalent) employed, and k0 and k are the rate constants in the absence and in the presence of added electrolyte at concentration c.

The inapplicability of the concept of ionic strength to the reaction between two anions is discussed and contrasted with the behavior of reactions between ions of unlike sign.
Application of the Platt Electrostatic Model to Diatomic Hydride Ions
Authors: Moran T. F. , Friedman L.
Published: January 2005

The Platt electrostatic model for calculating equilibrium internuclear distances and force constants of diatomic hydride molecules has been used to calculate properties of diatomic hydride ions. An empirical approach to the scaling technique proposed by Hall and Rees was employed in order to render the model consistent with the quantum mechanical virial theorem. This has the additional advantage of improving the calculated equilibrium properties. For twelve known hydride ions there is satisfactory agreement between calculated and experimentally measured force constants and equilibrium internuclear distances. The applicability of the relation Kre/D0=const. to a sequence of similar diatomic ions was briefly examined. Calculated values of K and re were used in the above relation to estimate dissociation energies of the rare-gas hydride ions. Results are compared with experimental limits determined from mass spectrographic investigations. Equilibrium properties of the corresponding neutral species calculated by the Platt electrostatic model are consistent with the generally assumed instability of the rare gas hydride molecules.
Light Scattering by Linear Macromolecules Oriented in Laminar Flow. III. Perfectly Flexible Necklace Model with no Hydrodynamic Interaction
Authors: Peterlin A. , Reinhold Chr.
Published: January 2005

On the basis of the complete distribution function for the freely draining, ideal necklace model in laminar flow, the scattering intensity in the flow plane and in the plane perpendicular to the flow vector was calculated. The latter turns out to be independent of flow and the former shows a maximum and a minimum in the two directions of the main refractive index in the flow plane, respectively.
Transient Charge Transfer in Gaseous Rubidium—Benzene Collisions
Authors: Brewer Richard G.
Published: January 2005

The interaction that arises during gas-phase rubidium-atom—benzene-molecule collisions has been investigated through Rb87 hyperfine frequency measurements which utilize optical double resonance. An unusually large hyperfine-splitting shift of —137 000 cps/cm Hg of benzene vapor is observed. In contrast to previous studies with other buffer gases, the shift is too large to be explained by a mechanism involving either Pauli exclusion or van der Waals forces. When the shift is interpreted in terms of an adiabatic collision model following the theory of Foley for the pressure broadening of spectral lines, it is seen that the unpaired-electron density at the Rb nucleus is reduced about 8% during an average collision. This behavior is attributed to a partial and transient electron transfer to the benzene ring. A comparison with ESR studies of liquid media where the alkali valence electron resides dominantly on the aromatic ring illustrates the importance of the solvent in facilitating electron transfer.
Potential Energy Surface for H3
Authors: Porter R. N. , Karplus M.
Published: January 2005

An analytic semiempirical expression is developed for the ground-state potential-energy surface of the H3 system. Use is made of the valence-bond formulation with the inclusion of overlap and three-center terms. The diatomic Coulomb and exchange integrals are estimated from accurate values for the H2 molecule by a modified London—Eyring—Sato procedure, while the three-center integrals are approximated by simple formulas. A linear, symmetric saddle-point configuration of minimum energy is found that has properties in approximate agreement, though not identical, with other estimates from theory and experimental rate data. The details of the surface are presented in terms of contour maps for a variety of distances and angles. Because of the inclusion of overlap and three-center terms, a more realistic energy is expected for the nonlinear configurations than could be obtained from previous potential energy formulas. The utility of the present method for dynamical studies of reaction cross sections is indicated.
Hydride and Proton Transfer Reactions Involving Sec-Propyl Ions
Authors: Borkowski R. P. , Ausloos P.
Published: January 2005

The reactions of sec-propyl ions produced in the radiolysis of n-C4D10 and i-C4D10 with hydrocarbons has been investigated. When the additive (RH) is a saturated hydrocarbon, the hydride transfer reaction: C3D7++RH→C3D7H+R+is the major mode of reaction. For straight chain hydrocarbons, the cross section of this reaction, relative to that of the reference reaction C3D7++C4D10→C3D8+C4D9+is shown to increase with the molecular weight of RH. For different hydrocarbon isomers, the relative cross section of the hydride transfer reaction decreases with an increase in branching while the analogous reactions involving ethyl ions show no such discrimination.

From the isotopic analysis of the propanes and propylenes produced in the radiolysis of C4D10 carried out in the presence of olefins, it was concluded that the proton transfer reactionC3D7++RH→C3D6+RHD+occurs.

Comparison of the data obtained, using C3D8, n-C4D10, and i-C4D10 as sources of ethyl or propyl ions, indicated that the relative cross sections of the hydride transfer reactions are independent of the origin of the carbonium ion.
Attempts to Observe the Far-Infrared Spectra of Adsorbed Molecules
Authors: Yates D. J. C.
Published: January 2005

The far-infrared transmission of high surface area silica and alumina has been measured between 300 and 30 cm—1. Although a series of gases was investigated, under conditions where it was known adsorbed molecules were present, no bands due to adsorbed molecules could be detected. The reasons for the absence of bands are discussed in detail.
Electrical Conduction of a High Polymerized Sample of Sodium Salt of Deoxyribonucleic Acid
Authors: Liang C. Y. , Scalco E. G.
Published: January 2005

The electrical conduction of pressed pellets of a high polymerized Na-DNA sample at various stages of drying has been studied. It has been found that in the early stages of drying, the resistance and activation energies are lower in comparison with those values obtained when the sample is further dried. The resistance of a Na-DNA film has been measured at various relative humidities. The activation energies for the film samples in the dry state were also measured. The conduction of Na-DNA is assumed to be due to electrons excited from impurity centers. The activation energy for photoconduction is interpreted as the barrier between neighboring DNA helices hindering the charge-carrier transport.
Lifetime of Excited States in Solution by the Quenching Method
Authors: Dubois Jean T. , Van Hemert Rudy L.
Published: January 2005

The fluorescence of naphthalene, benzene and twelve of its alkyl derivatives has been quenched by biacetyl in aerated normal hexane solution at 28°C. From the experimental quenching constants and the limiting rate constants computed for a diffusionally controlled quenching process, the lifetimes of the excited donors were obtained. These are shown to compare favorably with direct lifetime measurements (by phase shift) on the same materials.
Some Dielectric Properties of Tantalum Pentoxide
Authors: Pavlovic A. S.
Published: January 2005

The dielectric constant and dissipation factor of β- and α-Ta2O5 ceramics and of plates cut from a boule of α-Ta2O5 have been measured from 77° to 373° K over a frequency range from 100 cps to 100 kc/sec. β-Ta2O5 ceramics behave as typical dielectric materials. On the other hand, α-Ta2O5 ceramics exhibit large migrational losses, similar to those found in glasses, due to the migration of the tantalum ion through the structure. The activation energy Q of the process is estimated to be about 0.64 eV, in close agreement with 0.71 eV found from the formation of anodic films on tantalum. This and other facts suggest that anodic tantalum pentoxide is similar to that of the α form. A large relaxation peak is found in the data for boule α-Ta2O5 material having Q=0.2 ev and τ0=10—10 sec. This peak must arise from a large deformation of the structure to account for such a large relaxation time and large dielectric constant peak.
Attraction between Long Polyconjugated Chain Molecules
Authors: Sternlicht Himan
Published: January 2005

The attraction forces between large molecules having highly mobile electrons distributed over many atoms are not well understood. The Coulombic interaction between electrons within a molecule causes the motion of each mobile electron to be correlated with those of many other electrons of the molecule. These correlation effects modify the attraction forces. A proper assessment of these effects at present is extremely difficult, and usually impossible to do. In this paper we calculate the ``mobile electron'' attraction force between long, equal bond polyenes (one of the most simple examples of large molecules having mobile, distributed electrons), and use the Tomonaga method to assess the correlation effects. We compare our results with those of earlier investigators who used an ``independent electron'' model which ignored correlation effects. We find that correlation effects are very important—their neglect leads to significant overestimation of the attraction. We give a simple physical interpretation of our results. Many of our conclusions should be applicable to other large molecules, such as the polyacenes.
Vibronic Selection Rules at Special Points of the Brillouin Zone: Pr3+ in LaCl3
Authors: Satten Robert A.
Published: January 2005

The method of obtaining vibronic selection rules is described for an isolated impurity rare earth or actinidetype ion in a rare earth or actinide salt for various symmetry points of the Brillouin zone. The method is applied to Pr3+ in LaCl3 and the results used to further interpret the vibronic spectrum previously reported by Richman, Satten, and Wong. It is shown that in addition to the region around k=0, the region about the plane kz=0 is also probably the most important for the vibronic transitions. The points K and K′ are shown to lead to the same type of spectrum as the point at k=0.
Inelastic Scattering of 390-V Electrons by Helium, Hydrogen, Methane, Ethane, Cyclohexane, Ethylene, and Water
Authors: Lassettre Edwin N. , Francis Stanley A.
Published: January 2005

Electron impact spectra obtained by the inelastic scattering of 390-V electrons from helium, hydrogen, methane, ethane, cyclohexane, ethylene, and water are given. It is shown experimentally that, at small scattering angles and a fixed velocity-analyzer setting, the scattered current as a function of pressure contains a maximum. The theory of this effect is discussed.
Determination of Generalized Oscillator Strengths for Molecular Hydrogen by Electron Impact
Authors: Lassettre Edwin N. , Jones Ernest A.
Published: January 2005

Inelastic electron collision cross sections at small scattering angles are determined for molecular hydrogen using electrons whose initial kinetic energies range from 324 to 461 V. Oscillator strengths have been calculated from the data and compared with values determined from ultraviolet absorption data by other investigators. The oscillator sum has been calculated and compared with theory and calculated refractive indices compared with experiment. Agreement is good.
Collision Cross-Section Study of Two Transitions in Nitrogen
Authors: Lassettre Edwin N. , Krasnow Marvin E.
Published: January 2005

Electron collision cross sections at three voltages have been determined for two transitions in nitrogen. One of these corresponds to the Lyman—Birge—Hopfield bands, a forbidden system, and it is shown that the collision cross sections are compatible with the term symbol assignment for the excited state.
Electronic Collision Cross Sections and Oscillator Strengths for Oxygen in the Schumann—Runge Region
Authors: Lassettre Edwin N. , Silverman S. M. , Krasnow Marvin E.
Published: January 2005

Electron collision cross sections have been determined for that transition in oxygen corresponding to the dissociation continuum of the Schumann—Runge bands. Generalized oscillator strengths have been calculated from the data and extrapolated to zero momentum change for the colliding electron. The extrapolated value obtained, when integrated over the transition, is 0.230. This value is compared with oscillator strengths obtained from ultraviolet absorption spectra by other investigators.
Spectroscopy of Carbon Vapor Condensed in Rare-Gas Matrices at 4° and 20°K. II
Authors: Weltner William , McLeod Donald
Published: January 2005

The vaporization of C13-substituted carbon has established the isolation of C3 molecules in the matrix and the assignment of the v3″ frequency observed in the infrared spectrum. A vibrational analysis of the near-ultraviolet spectrum (the well-known 4050-Å gas bands) of C3 trapped in a neon or argon matrix has been carried out. The presence of a large Renner effect (ε=+0.566) in the bending motion in the excited state of this 1Πu↔X1Σg+ transition has been confirmed. Infrared and fluorescence spectra also support the assignment of a low bending frequency (∼70 cm—1) in the ground state as recently proposed by Gausset, Herzberg, Lagerqvist, and Rosen. Then the following vibrational frequencies apply: Πu1 state:ν1′=1125 cm−1,ν2′=305 cm−1,ν3′=?;Σg+1 ground state:ν1′′=1235 cm−1,ν2′′≅70 cm−1(?),ν3′′=2040 cm−1.v2″ is still doubtful because it does not yield thermodynamic functions for C3 which agree with those derived by mass spectrometry. The f number (oscillator strength) of the 0–0 band has been found to be about 7×10—4 in a neon matrix. The properties of a long-lived emission (lifetime=0.02 sec in neon) at 5856 Å indicate that it is the 3Πu→1Σg+ transition of C3. Another, rather unpredictable, system of bands near 4200 Å has also been seen in absorption and emission, but the molecule producing these bands has not been identified. An attempt has been made, via a linear chain model, to assign the stretching frequencies of the larger carbon molecules, C4, ···, C12, which have been observed in the infrared after solid-state diffusion was allowed to occur.
On the Kinetic Theory of Dense Fluids. XVI. The Ideal Ionic Melt
Authors: Berne Bruce , Rice Stuart A.
Published: January 2005

In this paper a theory is constructed to describe to first order the properties of a fused salt. The Rice—Allnatt theory of simple dense fluids is used in conjunction with the following assumptions: (1) oppositely charged ions are of nearly equal size and have identical electronic properties, except for the sign of the charge; (2) a negative ion is, on the average, surrounded by positive ions and vice versa; (3) short-range repulsive interactions occur only between pairs of oppositely charged ions; (4) the role of the Coulomb potential is to determine the fluid density and local fluid structure, but the Coulomb potential makes an insignificant contribution to the direct dissipation of energy and momentum. These conditions are taken to define an ideal ionic melt, and integrodifferential equations for the singlet and pair distribution functions of this system are derived. From these there is obtained an expression for the ion mobility in a weak electric field. This expression predicts a deviation from the Nernst—Einstein relation. A recipe for calculating the thermal conductance and shear viscosity is outlined. Some comparisons of theory with experiment are made. In particular, the theory can account for the magnitude of the deviation of the mobility—diffusion relationship from the Nernst—Einstein relation.
Calculation of Electron Scattering Factors. I. Nonrelativistic Theory
Authors: Karle J. , Bonham R. A.
Published: January 2005

Scattering factors for the elastic scattering from uranium and argon of 40-kV electrons have been obtained by partial wave analysis. In the case of argon both Thomas—Fermi—Dirac and Hartree—Fock fields were used in the calculation. For uranium, only the Thomas—Fermi—Dirac field was utilized.

Various approximate techniques for obtaining the partial waves as well as direct numerical integration of the Schrödinger equation were employed. For the first time accurate numerical solutions of the electron scattering problem in the kilovolt energy range, within the framework of the usual nonrelativistic scattering theory, have been obtained. Uncertainties in the scattering factors and in the use of the various approximate techniques for obtaining partial waves are discussed.