bluuebunny/crossref_metadata_2025 huggingface dataset:
Discontinuous Change of Binding Type in the Series of Monohydrides. III. Regularities and Irregularities of Internuclear Distances and Force Constants
Authors: Fajans Kasimir
Published: January 2005

The recently attempted correlation of internuclear distances of the monohydrides of all elements by linear plots of logr vs logZ (atomic number) for each of the two octaves and of the three long periods is not satisfactory. The equations re=2.2240 n−0.426 and r0=2.7793 n−0.371 (n is the total number of valence electrons in the hydride) apply merely from HF to BH and from HCl to AlH, respectively. The marked deviations from these equations shown by the hydrides M (I) H and M (II) H are related to a discontinuous change of binding type. In the long periods, r increases for the hydrides of the heavy metals from M (I) H to M (III) H, due to the decrease of polarizability and penetrability of the cations with an 18-electron (s2p6d10) outer shell, e.g., from AgH to InH. It is emphasized that the knowledge of spectroscopic data for molecule ions of the hydrides of long period elements is necessary in order to decide at which places discontinuous changes of binding type occur.
X-Ray-Diffraction Study of Zinc Bromide Solutions
Authors: Wertz David L. , Lawrence Richard M. , Kruh R. F.
Published: January 2005

X-ray studies of solutions of zinc bromide show four coordination for the zinc ion. In concentrated water and acetone solution, zinc is coordinated by two bromines and two oxygens, on the average. If the bromine/water ratio is increased by adding hydrobromic acid, zinc becomes totally coordinated by halide. These solutions are too concentrated, however, to speak of the existence of discrete ZnBr4= ions. Crystal radii serve to interpret contacts between species in solution.
3Π Levels and Predissociations of N2 near the 12.135-eV Dissociation Limit
Authors: Carroll P. K. , Mulliken R. S.
Published: January 2005

The two predissociations in the second positive bands, C 3Πu→B 3Πg, have been re-examined in the light of recent spectroscopic studies of the N2 spectrum. It is concluded that the predissociation of Büttenbender and Herzberg is due to a 5Πu state and not to a 3Πu state as formerly believed. However, a few details of the predissociation are not yet clearly explained. The second, less well-known predissociation of Hori and Endo is interpreted as being in all probability due to the C′ 3Πu state (the upper state of the Goldstein—Kaplan bands). This explanation requires that the C′ state have a maximum in its potential curve at an internuclear distance of about 2.0 Å. The behavior of the C and C′ potential curves, which should apparently intersect at about 1.4 Å, is interpreted as a noncrossing rule interaction. The vibrational structure in the region of the interaction is discussed and in particular the level reported by Pannetier et al. and that reported by Tanaka and Jursa are attributed to a mixture of v=5 of C and v=1 of C′. The level formerly tentatively assigned to v=1 of C′ is now considered to be primarily v=2 of the same state. Some low-temperature afterglow mechanisms are discussed in terms of the new interpretations of the C and C′ states. The 5Πu and 3Πu states which are to be expected in the energy range of interest are discussed theoretically by the application of both the molecular orbital and the Heitler—London methods and the conclusions are found to be consistent with the present interpretation of the experimental results.
Cyanate Ion in Alkali Halides: New Vibrational Levels and Interpretation of Localized Lattice Modes
Authors: Decius J. C. , Jacobson J. L. , Sherman W. F. , Wilkinson G. R.
Published: January 2005

The infrared absorption of alkali halide single crystals containing NCO− impurity at concentrations up to about 1 mole % has yielded new information about the internal vibrational levels of the cyanate ion. Satellite lines near ν3 and its combinations have been shown to arise from neighbor pairs of cyanate ions in the host lattice. Absorptions of the type ν3±νk, where νk is of the order of 80 to 180 cm−1 and is strongly dependent upon the host lattice, have been observed; and the relation of νk to the impurity-induced localized lattice modes is discussed.
On the Ordered State of Nickelous Formate Dihydrate
Authors: Uryû Norikiyo
Published: January 2005

The behavior of the magnetic ions in nickelous formate dihydrate, Ni(HCOO)2·2H2O, below its transition temperature is discussed theoretically. Expectation values of the spins at the two inequivalent sites in this crystal are calculated and expressions for paramagnetic and antiferromagnetic susceptibilities are derived. Crystal-field parameters and the exchange integral which appear in the spin Hamiltonian for the present system are estimated from experimental data. If the same approximation as was used in the case of dihydrated formates of Mn++ and Fe++ is adopted, it is concluded that the spins for Ni(HCOO)2·2H2O at the two inequivalent sites in its antiferromagnetic state have different expectation values, 0.75 and 0.40. The coexistence of both paramagnetic and antiferromagnetic states is shown to be impossible.
Kinetics of the Thermal Decomposition of C2F6 in the Presence of H2 at 1300°—1600°K
Authors: Tschuikow-Roux E.
Published: January 2005

The thermal decomposition of hexafluoroethane in the presence of hydrogen has been studied in a single-pulse shock tube in the temperature range 1300° to 1600°K. The reactants were highly diluted with argon, the composition ratios being Ar:H2:C2F6≃7500:17.4:1. The principal reaction products containing carbon were fluoroform and tetrafluoroethylene. A reaction scheme which accounts for these products is proposed and the first-order rate constant for the primary step C2F6→2CF3 is deduced: k1=4.3×1017 exp(−94 400±4000)/RT sec−1.

Accepting an activation energy of about 1 kcal/mole for the recombination of CF3 radicals leads to D(CF3–CF3)≃93±4 kcal/mole.
Dipole Moments in Relation to Configuration of n-Alkane Chains Bearing α, ω Dipolar Substituents
Authors: Leonard W. J. , Jernigan R. L. , Flory P. J.
Published: January 2005

The dipole moments of α,ω-dibromo-n-alkanes Br–(CH2)n−1–Br have been treated by exact methods applicable to a linear sequence of bonds each constrained to choice among several discrete rotational states, due account being taken of neighbor dependence in assignment of statistical weights to the various configurations. Computations have been carried out on the basis of threefold potentials with one trans and two gauche states (±120°) for each bond. Successive gauche states of opposite sign are excluded by steric overlaps. An energy of 500 cal mole−1 has been assigned to gauche relative to trans, in keeping with spectroscopic evidence for n-alkanes and the scheme successfully applied to the mean-square dimensions of polymethylene chains. Nonbonded interactions in which a Br atom is involved have been assigned statistical weights consistent with van der Waals radii and with evidence from Raman and infrared studies on n-alkyl bromides. The mean-square dipole moments averaged over all configurations are appreciably affected by the dipole—dipole interaction energy for n−1<6, but not for longer chains. Calculated values are in good accord with experimental results for n−1=3 to 10, inclusive. The applicability of the rotational-isomeric state-approximation to chains of comparatively short length is thus demonstrated.
Microwave Absorption and Molecular Structure in Liquids. LXV. A Precise Michelson Interferometer for Millimeter Wavelengths and the Dielectric Constants and Losses of Some Low-Loss Liquids at 2.1 mm
Authors: Garg S. K. , Kilp H. , Smyth C. P.
Published: January 2005

The theory and apparatus for a Michelson interferometer for the precise measurement of dielectric constant and loss of liquids at 2.1-mm wavelength are described. The probable error of the dielectric-constant measurements is 0.2%. The probable error of the loss measurements is 2% or ±0.0002, whichever is higher. The dielectric constants and losses of dilute solutions of chlorobenzene in benzene have been measured at 2.1-mm wavelength at 20° and compared in the light of existing lower-frequency data. The dielectric constants and losses of several nonpolar and slightly polar liquids have also been measured at 2.1-mm wavelength at 20°. The presence of appreciable losses in benzene and carbon tetrachloride has been confirmed. Measured losses in cyclohexane and n-heptane are considerably lower than those in benzene and carbon tetrachloride.
Measurement of the Density of Saturated Cesium Vapor by an Optical Method
Authors: Rozwadowski M. , Lipworth E.
Published: January 2005

The vapor pressure of cesium metal has been measured as a function of temperature using a scanning Fabry—Perot interferometer. The apparatus was constructed to measure cesium-vapor densities in optical pumping experiments. In clean, evacuated glass bulbs the vapor pressure of pure cesium metal is in close agreement with the results of Langmuir and Taylor. The vapor pressure is lowered considerably if rubidium metal is mixed with the cesium.
Adsorption and Oxidation of Carbon Monoxide on (100) Nickel
Authors: Park Robert L. , Farnsworth H. E.
Published: January 2005

Exposure of a clean (100) nickel surface to CO results in the formation of a structure designated as (100) Ni c2×2—CO whose unit mesh is twice as large as that of the clean surface. This is interpreted to mean that CO is adsorbed with one molecule to every two atoms of the (100) nickel surface, in contrast to the (110) surface on which one molecule adsorbs to each atomic site. The work function increase due to adsorbed CO was less than for (110) nickel, and a much higher temperature was required to remove the CO from the (100) surface. These results suggest that CO may be bound in a bridged structure on the (100) face rather than a linear bond as on the (110). Heating at temperatures below that required to remove the CO and then cooling to room temperature produced a large increase in the diffraction intensity, suggesting a possible reconstruction of the nickel substrate. Exposure of the CO covered surface to O2 extinguished the diffraction pattern and caused the work function to decrease. If the crystal was then heated, a pattern having the same unit mesh as the initial CO structure appeared, but was shown to be that of the (100) Ni c2×2—O structure, the preadsorbed CO having reacted to form CO2 which was desorbed by heating. CO did not react with a (100) nickel surface which had received prior exposure to O2.
Spectra of C3 in Solidified Gases at 4° and 20°K
Authors: Barger R. L. , Broida H. P.
Published: January 2005

Wavelength, linewidth, and intensity measurements have been made from 3000 to 4500 Å of the spectra of triatomic carbon molecules trapped in solid matrices of Ar, Kr, Xe, O2, N2, CO2, and SF6 at 4° and 20°K. The carbon source was a Knudsen cell, operated at temperatures up to 2900°K, from which effused a molecular beam with known densities of C3. Absorption transitions are assigned to vibrational levels of both upper and lower states of the 1Πu—X 1Σg+ 4050-Å group of C3. The fundamental vibrational frequencies ν1 and ν2 for the upper 1Πu state, ν2 for the ground 1Σg+ state, and Renner constants for ν2 of the 1Πu state in these matrices are given. Measurements of absorption intensities give an oscillator strength, averaged for all matrices, equal to 6×10−2 for the C3 group. Little or no matrix effect on the intensities is found. However, experimentally determined corrections to the intensities are necessary for effects caused by apparent diffusion of carbon in the matrices to form nonabsorbing carbon aggregates. C3 linewidths vary with matrix from 40 to 500 cm−1, and C3 line shifts vary from −410 to 1065 cm−1. All matrix shifts are to the red except in the case of the CO2 matrix. No definite effect of temperature on linewidths or shifts is found.
Spectra of C2 in Solidified Gases at 4° and 20°K
Authors: Barger R. L. , Broida H. P.
Published: January 2005

Absorption features attributed to C2 have been observed for carbon in solid Ar, Kr, Xe, N2, CO2, and SF6 matrices at 4° and 20°K. For the CO2 matrix, five well-defined bands of the A 3Πg—X 3Πu Swan system and four bands believed to be the forbidden A 3Πg—x 1Σg+ system were obtained. For other matrices the bands were weak, wide, and few in number, making identification difficult. Measured vibrational constants are given. Swan system f-values for C2 in these matrices were measured and are in agreement with measured values for the gas phase. Measurements of C2 emission and absorption in a Xe matrix showed that the first vibrational level of the ground electronic state was populated in the matrix at 4°K, and that the vibrational energy was not easily removed. Absorptions from excited vibrational levels of the ground state also were observed for other matrices.
Random-Walk Model of Chain-Polymer Adsorption at a Surface
Authors: Rubin Robert J.
Published: January 2005

A random-walk lattice model of adsorption of an isolated polymer chain at a solution surface is investigated. One-dimensional characteristics of the monomer-unit distribution are determined analytically in the limit of long polymer chains, neglecting the self-excluded volume. The mean number of monomer units adsorbed in the surface layer ν(θ, N) is determined, assuming that one end of the polymer chain lies in the surface layer. The parameter N is the number of monomer units in the chain, and θ is the adsorption energy of each monomer unit in the surface layer measured in units of kT. In addition, the mean distance of the free end of the chain from the surface z(θ, N) is determined. The lattice models considered include the simple-cubic, hexagonal-closepacked, face-centered-cubic, and body-centered-cubic lattices. In the limit in which N→∞, both ν(θ, N) and z(θ, N) exhibit a very interesting discontinuity at a lattice-dependent adsorption energy θc. For example for θ>θc, ν(θ, N) (which is also proportional to the average adsorption energy of a polymer chain) is proportional to N. For θ<θc, ν(θ, N) is proportional to a constant of order unity; and for θ=θc, ν(θ, N) is proportional to N½. It is shown that the probability distribution of the end of the chain decreases exponentially with increasing distance from the surface layer for θ>θc. In addition, the mean number of monomer units in the kth layer from the surface is determined for N≫1 and θ>θc and is found to decrease exponentially with increasing k. In effect, for θ>θc the polymer chain exists in an adsorbed state. An improvement in the model, which includes short-range correlation between successive steps in the random-walk description, is also considered.
Determination of Electronic Symmetry by Electric Deflection: LiO and LaO
Authors: Berg Robert A. , Wharton Lennard , Klemperer William , Büchler Alfred , Stauffer James L.
Published: January 2005

The focusing, by means of an electrostatic quadrupole, of polar molecules with first- or second-order Stark effects is discussed. Indications of molecular electronic symmetry may be obtained from quantitative measurements of the intensity of refocusing of beams of diatomic molecules. Such measurements indicate that the ground state of LiO is Π while that of LaO is Σ. It is suggested that the optical spectroscopic data of ScO, YO, and LaO are best explained by assigning the ground states of these three molecules as 2Σ. The observed low-lying electronic states of these molecules are interpreted in terms of a localized-orbital picture.
Radio-Frequency Spectrum of the a 3Π State of Carbon Monoxide
Authors: Freund Robert S. , Klemperer William
Published: January 2005

A preliminary investigation of the molecular-beam electric resonance spectrum of the metastable a 3Π state of 12C16O is reported. The electric dipole moment observed is 1.38±0.02 D. The variation of dipole moment with vibrational state appears to be less than 0.005 D per vibration. Lambda doubling values in the Ω=2 fine structure component are reported for J=2, 3, and 4. The population distribution among vibrational states resulting from excitation by 11-V electrons is in good agreement with calculated Franck—Condon factors.
Calculation of Inelastic Electron—Molecule Collision Cross Sections by Classical Methods
Authors: Bauer Ernest , Bartky Charlotte Decker
Published: January 2005

We have used Thomson's, Gryzinski's, and Ochkur's classical methods for energy transfer in electronic collisions together with the quantum-mechanical Franck—Condon factor for the overlap of nuclear wavefunctions to compute inelastic electron—molecule collision cross sections. Specific application is to ionization and to direct and exchange electronic excitation. After first extending previous applications of the classical energy-transfer methods to atoms, we make calculations for ionization, direct and exchange (spin-change) excitation involving air molecules (N2, N2+, NO, O2, also CO). The results are applied to the near-threshold domain as well as to the over-all behavior of the cross section. Agreement with the very few absolute experimental data available is to within better than a factor of 2 to 3. These methods must be regarded as useful when one considers that there exist hardly any experimental data on excitation and that quantum-mechanical calculations would be prohibitively lengthy to carry out while the present calculations are very simple to perform.
Electron Spin Resonance of Tetraphenylporphine Chelates
Authors: Assour Jacques M.
Published: January 2005

ESR studies of three paramagnetic tetraphenylporphine chelates: vanadyl, cobalt, and copper reveal distorted crystal-field surroundings which are more pronounced in the cobalt derivative. The spin-Hamiltonian parameters and the 3d energy levels of the cobalt derivative are greatly influenced by axial distortions. The bonding scheme in these complexes indicates strong in-plane σ bonding characteristic of organometallic square-bonded complexes, and little or no in-plane π bonding. Out-of-plane π bonding is more significant in the vanadyl and cobalt derivatives than in the copper complex. ESR of magnetically concentrated samples indicate a substantial reduction in the dipolar and exchange interactions between neighboring metal ions in comparison to those found in phthalocyanines. A tentative explanation for the reduction of the dipolar forces is that the crystallographic packing of the phenyl rings above and below the molecule might effectively shield the paramagnetic ion from its nearest metal-ion neighbors.
Absolute Infrared Intensities of the Fundamental Absorption Bands in Solid Carbonyl Sulfide
Authors: Yamada Haruka , Person Willis B.
Published: January 2005

Absolute infrared intensities for the fundamental absorption bands of COS have been measured in polycrystalline solid films. The path length has been measured by observing interference fringes. The results are in fair agreement with the intensities computed from the gas-phase values, corrected for the simple ``field effect,'' except for the very weak band, ν2. These results, together with those reported earlier for other linear triatomic molecules, are examined critically in a search for patterns of behavior. The ``intensity sum rule'' for crystals is restated. It is concluded that the spectra of these crystals are good examples of those to be expected for weak ``chemical'' interactions.
Polarization Effects in the Ionic Conductivity of Alkali Halide Crystals. II. Current—Time Dependence
Authors: Allnatt A. R. , Jacobs P. W. M. , Maycock J. N.
Published: January 2005

The dc polarization of KCl at high temperatures has been investigated for the first time. Current—time curves may be resolved as the sum of a steady-state current and the time-dependent polarization current: the latter may be represented as the sum of two exponential terms. The relaxation times for these two processes are of the order of 40 and 250 sec at around 850°K. The Jaffé (constant-field) theory has been extended to include the case of low fields and the resulting equations have been solved numerically. The calculated relaxation times are an order of magnitude larger than those found experimentally. The reason for this discrepancy is probably the severity of the constant-field approximation.

The polarization is attributed to the slowness of the electrode processes compared to the velocity of the carriers in the bulk crystal and numerical values of the discharge parameter are derived. These are consistent with an activation energy for the electrode process of about 2 eV.
Improved Free-Volume Theory of Liquids. VII. Radial Distribution Functions for the Worm Model
Authors: Chung Harold S. , Dahler John S.
Published: January 2005

Radial distribution functions have been calculated on the basis of the worm model. The calculations are specific to a system of molecules which interact according to the Lennard—Jones 12–6 potential. Comparisons are provided of our results with those of other theories and with Monte Carlo calculations and experiment. The agreement between theory and experiment (and/or Monte Carlo data) is found to be satisfactory only at very high pressures.
Study of the Properties of an Excess Electron in Liquid Helium. II. A Refined Description of Configuration Changes in the Liquid
Authors: Hiroike Kazuo , Kestner Neil R. , Rice Stuart A. , Jortner Joshua
Published: January 2005

In this paper we present a study of the structural changes in liquid helium in the vicinity of an excess electron. We have used the formal similarity between the pair distribution function of an N-boson system, with the wavefunction expressed as the product of pair wavefunctions, and the pair distribution function of a classical fluid. The present model leads to an interfacial surface energy term which is in good agreement with the observed surface tension of liquid helium at 0°K. An important contribution to the bubble energy arises from the volume kinetic energy arising from the excess kinetic energy of the fluid atoms removed from the boundary layer. The bubble radius of 12.4 Å calculated herein is found to be in excellent agreement with the available experimental data.
Additivity of Heats of Combustion, LCAO Resonance Energies, and Bond Orders of Conformal Sets of Conjugated Compounds
Authors: Marcus R. A.
Published: January 2005

The notion of ``conformal sets'' of aromatic and other conjugated compounds is introduced. To a good approximation, it is found that the sum of the heats of combustion of the compounds in one set equals the sum for the compounds in the other set. Similar additivity occurs for their LCAO-calculated total π-electron energies, LCAO bond orders and free valences. Bond lengths and dissociation energies are also considered. Conformal sets are defined in terms of their number and quality of self-returning random walks on the atoms of the conjugated compounds. Even-electron nonalternant and alternant compounds are included, as are, in certain cases, radicals. Some insight into the additivity for LCAO properties is obtained by relating the coefficients in LCAO secular equations to random walks and using contour integral formulas connecting LCAO properties with secular determinants.
Dissociation and Isomerization of Vibrationally Excited Species. III
Authors: Marcus R. A.
Published: January 2005

The equations of Part I for the specific and over-all unimolecular reaction-rate constants are extended slightly by including centrifugal effects in a more detailed way and by making explicit allowance for possible reaction-path degeneracy (optically or geometrically isomeric paths). The expression for reaction-path degeneracy can be applied to other types of reactions in discussions of statistical factors in reaction rates.
First and Second Triplets of Solid Benzene
Authors: Colson Steven D. , Bernstein Elliot R.
Published: January 2005

Absorption spectra have been taken of the O2-perturbed first (3B1u) and second (3E1u) triplets of solid benzene at 4.2°K. Spectra of both C6H6 and C6D6 were obtained. The (0–0) bands of the first triplet occur at 29 674±25 cm−1 for C6H6 and 29 851±25 cm−1 for C6D6. For the second triplet they lie at 36 560 cm−1±50 for C6H6 and 36 784±50 cm−1 for C6D6. The result for the first triplet of C6H6 compares very favorably with Evans' gas-phase O2-perturbed spectrum. It is also in satisfactory agreement with Nieman's accurate phosphorescence measurements on isotopic mixed crystals of benzene which place the C6H6 (0, 0) band position in the crystal at 29 657.1 cm−1. Many precautions were taken to eliminate the possibility of mis identification of the second triplet. The observation that the O2-enhanced first triplet and the O2-enhanced bands in the 36 600-cm−1 region always appear together and with approximately the same relative intensities is considered to be the best evidence for the assignment. However, the rather broad structure obtained by the O2-perturbation technique does not allow all the uncertainties in the identification to be completely removed, nor does it allow a detailed study of this interesting state.

A detailed evaluation of the purity of the benzene is made, and a method is described for the preparation of material having ultrahigh spectroscopic purity. Crystals, up to 5 cm in length, of this very highly purified C6H6 and C6D6 were studied at 4.2°K to ascertain if the singlet—triplet absorptions could be seen in the absence of a perturbation. The long crystals showed some sharp and some broad (Δν≈150 cm−1) absorptions starting at 36 947±50 cm−1 in C6H6 and at 37 147±50 cm−1 in C6D6. The broad absorptions correlate reasonably well with the features assigned to the second triplet in the O2-perturbation experiments. The first triplet is too weak to be observed in the long-crystal experiments. The position of the second triplet lies about 3000 cm−1 above that given by the Pariser—Parr calculation. This places the second triplet about nine-tenths rather than half of the distance from the lowest triplet to the lowest excited singlet.
Transposition of the Theories Describing Superconducting Systems to Molecular Systems. Method of Biorbitals
Authors: Bratož S. , Durand Ph.
Published: January 2005

A new theory of the electronic structure of molecules is proposed, based on a wavefunction of the following type: φSCF−BI=NAψ(1,2)ψ(3,4)···ψ(2N···1,2N).This wavefunction is called the self-consistent-field biorbital wavefunction, and the factors ψ(i, j) are called biorbitals. This function is discussed, the corresponding energy expression is derived, and the variational equations leading to the best possible φSCF–BI are presented. This theory is the molecular version of Blatt's theory of superconducting systems.
Velocity Distribution of a Dilute Chemically Reacting Gas
Authors: Kostin M. D.
Published: January 2005

From the Wigner—Wilkins integral equation for the velocity distribution of a dilute chemically reacting gas which exchanges energy with a Maxwellian diluent gas, a simple integral equation for the high-energy region is derived. For a constant reaction cross section σr, the velocity distribution of the reactive molecules in the high-energy region is n(x)=xp exp(—x2), where p=2(1−λp)/(1−λ2)(1+σr/σs), σs is the scattering cross section, λ=(1—μ)/(1+μ), μ is the ratio of the reactive to diluent molecule mass, and x is the normalized velocity of the reactive molecule. A modified form of the Wigner—Wilkins equation is then used to extend these results into the thermal region. Small changes in the reaction cross section can produce significant changes in the velocity distribution; the perturbations of the Maxwellian distribution become even more pronounced when scattering is anisotropic in the forward direction.
United-Atom Approximation Applied to Argonlike Molecules. II. PH2−, PH3, and PH4+
Authors: Banyard K. E. , Hake R. B.
Published: January 2005

The united-atom treatment has been applied to the systems PH2−, PH3, and PH4+. For PH3 and PH4+, satisfactory values are obtained for the total molecular energy and ``breathing'' force constants when compared with experiment. The model gives theoretical bond lengths which are in good agreement with the observed values. Coherent x-ray scattering factors are presented for PH3 and PH4+ along with a discussion of the molar diamagnetic susceptibilities. The value of the proton affinity derived here for PH3 is found to be in general agreement with the experimental results.

Except for the considerable improvement in the proton-affinity calculation, the results obtained here are in keeping with the conclusions derived from our earlier work concerning the united-atom study of H2S.
Infrared Spectra of Anhydrous Rare-Earth Nitrates from 4000–100 cm−1
Authors: Walker A. , Ferraro J. R.
Published: January 2005

The infrared spectra of the anhydrous rare-earth nitrates are presented in the region 4000–100 cm−1. Strong coordination of the nitrate groups to the metal atom occurs. Possible different types of metal—oxygen bonding in these compounds is discussed.
Relationships between Polymer Structure and Glass Temperature. I. The n-Alkanes
Authors: Lewis O. Griffin
Published: January 2005

The constants in the empirical equation log(η/d)=logA+B/(T−T0) were evaluated from published viscosities η and densities d for 23 n-alkanes. All three adjustable parameters A, B, and T0 were found to vary with chain length. The parameter T0 is predicted with good precision by the Gibbs—DiMarzio theory of the glass transition with a ``flex energy'' ε of 490.8 cal/mole. This value is in agreement with determinations by other methods.
Electron Spin Resonance of Radical Cations Produced by the Oxidation of Aromatic Hydrocarbons with SbCl5
Authors: Lewis I. C. , Singer L. S.
Published: January 2005

Electron spin resonance (ESR) studies have been made of radical cations prepared by the oxidation of 24 aromatic hydrocarbons with SbCl5 in CH2Cl2 solvent. The transfer of reagents, reactions, and ESR measurements were carried out at temperatures below −78°C in the absence of air. The stability of the radicals in solution, and the resolution of ESR hyperfine structure, depended critically on temperature and on the concentrations of hydrocarbon and SbCl5. The coupling constants for the ESR spectra of the radical cations of perylene, anthracene, 9,10-dimethylanthracene, and naphthacene were essentially identical to those for the respective ions in H2SO4. The ESR spectra for the radical cations of pyrene, naphthalene, dibenzo-(a,c)triphenylene,Δ9,9′-bifluorene, and tetraphenylethylene have also been reduced to coupling constants. The positive radical ion resulting from the oxidation of naphthalene is a symmetrical dimer with the unpaired electron divided equally between the two molecules. The generality of McConnell's relationship aH=Qρ was examined by comparing experimental coupling constants with Hückel spin densities for available radical anion and cation data. A least-squares fitting procedure yielded Q=28.6 for anions and Q=35.7 for cations. Quantitative comparisons were made between experimental coupling constants and those computed from the Colpa—Bolton and Giacometti—Nordio—Pavan theories. Both theories were found to account appropriately for the differences in magnitude between the coupling constants for aromatic negative and positive ions.
NF2 Decomposition Behind Shock Waves
Authors: Modica A. P. , Hornig D. F.
Published: January 2005

The decomposition of the NF2 radical in excess argon was studied behind incident shock waves over a temperature range from 1400° to 2000°K at total concentrations between 0.9×10−2 and 1.9×10−2 mole/liter. The NF2 radicals produced from shocked N2F4 were characterized by absorption spectra in the 2600-Å region, recorded with a Hilger medium quartz spectrograph. Kinetics were deduced from oscillogram histories of NF2 absorption at 2600 Å. The rate law for decomposition was first order in both NF2 and argon concentration, d[NF2]/dt=—kAr[Ar][NF2], with kAr=1.62×1010T½ exp (−47 838/RT) liter/mole·sec. The absorption-spectroscopy results are compared with shock-tube/TOF mass-spectrometer data obtained at higher temperatures.
Gas-Phase Radiolysis and Photolysis of Neopentane
Authors: Lias Sharon G. , Ausloos P.
Published: January 2005

The photolysis of neo-C5H12—neo-C5D12 mixtures has been investigated at 1470 and 1236 Å. From the products formed in the absence and presence of NO or H2S, the occurrence of the following fragmentation processes could be derived: neo−C5H12*→CH4+iso−C4H8CH3+H+iso−C4H8CH3+CH3+C3H6.These modes of decomposition also prevail when neopentane is excited by collision with electrons accelerated by an electrical field applied during radiolysis. At 1236 Å, the relative probabilities of occurrence of Processes (1), (2), and (3) are approximately 1.0, 4.5, and 1.1.

From the isotopic analysis of the products formed in the direct and inert-gas-sensitized radiolysis of neo-C5H12—neo-C5D12 mixtures in the presence of NO, O2, or I2 as free-radical scavengers, it could be derived that the fragment ions C2H3+, C2H5+, C3H5+, and C3H7+ are formed and undergo hydride-ion transfer reactions with neopentane to form C2H4, C2H6, C3H6, and C3H8, respectively. Assuming that this is the only mode of reaction of these ions in the system, ion-pair yields of 0.028, 0.068, 0.062, and 0.015 are obtained for the above listed ions at a pressure of 30 Torr.

The propyl ion, which has a secondary propyl structure, undergoes a hydride transfer reaction with neopentane at a rate which is slower by more than one order of magnitude than the analogous reactions of the ethyl or allyl ions. It is observed that this relatively slow ion—molecule reaction is inhibited when an electric field is applied to the system, probably because of the collection of propyl ions on the cathode. In agreement with mass-spectrometric results, it is suggested that propyl ions are formed mainly as a result of the decomposition of the C5H11+ ion which is formed in the hydride-ion transfer processes.

The C4H9+ ion does not react with neopentane but does, under certain conditions, yield isobutene by an unspecified process. The ion-pair yield of isobutene increases with increasing pressure and with diminishing recombination energy of added inert gas.

In the direct radiolysis, the ion-pair yields of the fragment ions formed with appearance potentials above that of C4H9+ are seen to diminish when the pressure is increased, while, in the inert-gas-sensitized radiolysis, most of these ions increase with an increase of the recombination energy of the inert-gas ions, Xe+, Kr+, Ar+, Ne+.
Structure of Cyclopentadiene
Authors: Scharpen LeRoy H. , Laurie Victor W.
Published: January 2005

The microwave spectra of the three monosubstituted 13C species of cyclopentadiene have been investigated. The effective rotational constants of these species together with those of the main isotopic species give the structural parameters for the ring. Labeling the methylene carbon as C1 and numbering the other carbons sequentially we obtain: r(C1C2)=1.509 Å, r(C2C3)=1.342 Å, r(C3C4)=1.469 Å, ∠C1C2C3=109.3°, ∠C2C3C4=109.4°, ∠C2C1C5=102.8°.
On the Theory of the Concentration Dependence of the Self-Diffusion Coefficient of Micelles
Authors: Mazo Robert M.
Published: January 2005

A theory is given for the ratio of initial slope to intercept in a plot of 1/D versus concentration of colloid particles; D is the self-diffusion coefficient of the charged colloid particles (micelles). The theory starts from the Einstein relation, and the autocorrelation function expression for the friction constant. The main approximation is the use of Brownian motion theory to describe the effect of the solvent on micelle motion. There is good agreement with experiment in salt solutions, but the agreement is poor when there is no added salt. It is concluded that the theory is probably appropriate for solutions of high ionic strength, but the possibility that the data in salt-free solution have not been interpreted properly, i.e., that the theory has a wider validity, is also discussed.
Quantum-Mechanical Boltzmann Equation
Authors: Hoffman David K. , Mueller John J. , Curtiss C. F.
Published: January 2005

A Boltzmann equation is derived from the N-particle Schrödinger equation. The development is based on the solution of the two-particle quantum-mechanical Liouville equation due to Green. The various approximations involved in the derivation are discussed and the collision integral and corrections are compared to their classical analogs. Further development of the collision integral yields the standard result, the usual Boltzmann collision integral in which the classical differential cross section is replaced by its quantum-mechanical counterpart.
Infrared Lattice Spectra of α-Al2O3 and Cr2O3
Authors: Marshall R. , Mitra S. S. , Gielisse P. J. , Plendl J. N. , Mansur L. C.
Published: January 2005

Infrared-active lattice vibrational spectra of α-Al2O3 and Cr2O3 have been investigated by reflection and transmission measurements on single crystal samples and also by transmission on Nujol mulled Cr2O3. Single-crystal transmission data above 700 cm−1 have been assigned to combinations and overtones.
On Singularities in Eigenfunctions
Authors: Lakin W.
Published: January 2005

The relationship between some singularities of the eigenfunction and convergence of the Legendre expansion is studied for the ground state of the helium atom.
Microwave Absorption and Molecular Structure in Liquids. LXVI. The Dielectric Relaxation of the Water—Dioxane System and the Structure of Water
Authors: Garg S. K. , Smyth C. P.
Published: January 2005

The dielectric constants and losses of a series of mixtures of water and dioxane (0.2–0.8 mole fraction) have been measured at wavelengths of 0.217, 1.223, 3.193, and 10.09 cm, and 575 m and temperatures of 1°,10°,25°,40°, and 55°C. The results show that the mixtures have two dielectric relaxation times in contrast to the single time found for water. The results are interpreted as indicating a very rapidly fluctuating structure for pure water in which the molecules are constantly forming, breaking, and reforming hydrogen bonds to their neighbors. At any given instant there are unbonded molecules, as well as singly, doubly, triply, and quadruply bonded molecules, and molecules in all intermediate stages of bonding. However, the fluctuations of structure are so rapid that, averaged over the extremely short time required for dielectric relaxation, the molecules and their immediate environments are approximately the same. In the water—dioxane mixtures, the dioxane molecules alter the environments of some of the water molecules and thereby introduce a second relaxation time.
Vibration—Rotation Energy Transfer
Authors: Moore C. Bradley
Published: January 2005

A simple two-parameter model for vibration→rotation energy transfer fits the vibrational relaxation data for 25 different molecules with small moments of inertia. Thirty-five data are fit within a factor of 3. The model is limited to molecules in which the rotational velocities of the atoms are greater than the translational velocity of the molecule and in which the rotational level spacings are small compared to kT. The successful correlation of nearly all of the data available on these molecules leads to the conclusion that vibration→rotation energy transfer is a real and important effect. The theory provides an explanation of vibrational relaxation in a number of mixtures.
Absorption Spectrum of Na and K in Rare-Gas Matrices
Authors: Meyer Beat
Published: January 2005

The absorption spectrum of Na and K in Ar, Kr, and Xe matrices in the region from 2000 to 8000 Å has been studied as a function of temperature and, at 4°K, as a function of concentration. Observations on some spectra of Na in Ne are also included. The first member of the principal series, P212,12∘←S212, can be observed in all matrices. Higher members are weak and can, in most matrices, not be assigned. At alkali concentrations≥0.5%, strong additional absorptions are observed which seem to be due to alkali—alkali interaction.

Most transitions appear blue shifted and have triplet structure. The spectra are sharp in xenon but become increasingly diffuse in lighter rare-gas hosts. The line shape indicates fine structure in most absorption features. During the warm-up, the 2P←2S absorption broadens and shifts to the red. For a given ratio of observation temperature to melting point of host lattice, atomic absorption of the alkali metals seems to have the same linewidth in all of the observed matrices.
Eigenparameters for the 1sσg and 2pσu Orbitals of H2+
Authors: Peek James M.
Published: January 2005

Eigenparameters for the 1sσg and 2pσu electronic orbitals of the hydrogen molecule ion are investigated. The appropriate parameters are tabulated for the internuclear separations R=1.0(0.5)30.0 a0, and more extensive tabulations, available elsewhere, are described.
Density Distribution of Polymer Segments in the Vicinity of an Adsorbing Interface
Authors: Hoeve C. A. J.
Published: January 2005

At a small distance from the interface corresponding to the effective thickness of the segments, the density drops suddenly by an amount that is the greater, the stiffer the chain. Beyond this distance the density is exponential in the distance from the interface for long chains and relatively weak adsorption.
Effect of Translational Energy on Ion—Molecule Reaction Rates. II
Authors: Ryan Keith R. , Futrell Jean H.
Published: January 2005

A number of ion—molecule reactions have been studied by a method which allows considerable ion energy resolution in the region below 1 eV. The experiments show clearly that both the proton or hydrogen-atom transfer reactions as well as the condensation reactions studied can readily be explained in terms of the slow-ion theory of Gioumousis and Stevenson. Results for the three permanent dipole molecules studied, NH3, H2O, and HCl, indicate that the protonated molecular-ion formation can be explained using the energy-dependent cross section developed by Moran and Hamill. The application of this collision cross section expression leads to the conclusion that one collision in three produces the protonated parent for both NH3 and H2O and one collision in five for HCl.
Temperature Dependence of Vibronic Transitions in Crystals and Spectroscopic Observation of a Phase Transition
Authors: Satten Robert A. , Wong Eugene Y.
Published: January 2005

The temperature dependence of vibronic absorption bands, corresponding to either one phonon absorbed or emitted simultaneously with an electronic transition in a crystal having an octahedral UCl62− complex was measured and found to agree with the theoretically expected results. A phase transition was observed by the weak appearance of the pure electronic transition above a transition temperature. The latter exhibits hysteresis favoring a first-order transition. Selection rules and general symmetry arguments show that the distortion must be one of D2, D3, S4, D2d (special) about the uranium site. The particular arrangement of atoms enables a further reduction in the possible distortions to D2d or D3. From the relative intensity of pure electronic to vibronic transitions one can estimate the size of the distortion to be of the order of 2×10−3 times the lattice constant.
Partial Pressure of Se2 and Optical Density of Selenium Vapor in the Visible and Ultraviolet
Authors: Brebrick R. F.
Published: January 2005

The optical density of selenium vapor Dλ has been measured between 1900 Å and 2.0 μ at T0=860°, 700°, 500°, 400°, and 330°C and for total pressures (determined by the temperature of a liquid selenium appendage) between 7×10−5 and 1.0 atm. Previously observed vibronic bands of Se2 are seen and have a maximum value of Dλ near 3405 Å. Between 1900 and 2700 Å, Dλ is not linearly dependent upon the partial pressure of Se2, p2. The densities in this range bear a constant ratio to one another for fixed T0 over as many as two orders of magnitude in D2100 and appear to be due to a single species, Sen, n>2. Assuming D3405 is the sum of partial densities due to Se2 and Sen, each of which obeys Beers law, and that D2100 is proportional to pn then p2=r(D3405—kD2100)/L, where L is the optical path length. The value of k, which is the ratio D3405/D2100 for pure Sen, is chosen to be 0.18 so that log D2100 varies linearly with log(D3405−0.18D2100). The Beers-law constant r is obtained from measurements at sufficiently low total pressures that the vapor is all Se2 in the optical cell and from published total-vapor-pressure measurements. The values of p2 obtained agree to within 8% or better with those calculated from the Se2–Se4–Se6–Se8 equilibrium constants of Illarionov and Lapina and are significantly lower than those calculated from the standard tabulation of Stull and Sinke. For λ≥5000 Å, Dλ varies as the square of p2 and appears to be due to pressure broadening of the Se2 transition. The number of atoms in Sen is 4 at T0=860°C and 5 at lower temperatures. The latter number is interpreted as an average arising from the near equality of the partial pressures of Se4 and Se6 over the range of our measurements of D2100.
Nitride and Oxide Bands of Molybdenum
Authors: Howard John C. , Conway John G.
Published: January 2005

Investigation of the orange system bands (5990–6300 Å) produced by a molybdenum arc in air shows that they are a nitride system, and not an oxide as previously reported. Isotope shifts using nitrogen-14 and -15 are given. Evidence is presented that other bands, less conspicuous and hitherto unidentified, occurring in the red are an oxide of molybdenum, together with confirmation that the near-infrared bands formerly attributed to an oxide are such.
Collision Density of Hot Atoms
Authors: Felder R. M. , Kostin M. D.
Published: January 2005

The energy-dependent collision density of hot atoms is discussed and evaluated for several cases. A model is considered in which hot atoms collide with a single species of thermal atoms at energies where the asymptotic solutions of the Boltzmann equation are valid. Elastic nonreactive collisions between unlike species are treated in detail. It is shown that the assumption made by Wolfgang and other workers that the collision density is given by 1/Eα(E), where α is the mean logarithmic energy decrement of the hot atoms, is generally reasonable, but that error may be introduced if the energy dependence of α is not explicitly taken into account. Results are obtained for a class of interaction potentials which includes the inverse power potential, V = K/rs. The degree of scattering anisotropy is directly related to the exponent s of this potential: s = ∞ corresponds to isotropic (hard-sphere) scattering, and s = 1 represents the limiting anisotropic case of pure Coulombic scattering. A quantitative estimate of the influence of anisotropy on the collision density is thus provided by the results obtained. An example is then given to illustrate the application of the techniques shown to systems in which reactions occur.