bluuebunny/crossref_metadata_2025 huggingface dataset:
Ozone and Ozonide Production and Stabilization in Water
Authors: Heidt Lawrence J. , Landi Vincent R.
Published: January 2005

Evidence is presented showing that ozone and ozonide are produced by the photochemical decomposition of hydrogen peroxide and sodium persulfate in water made alkaline with sodium hydroxide. Their yields and lifetimes are increased by increase in base and molecular oxygen, the increase with base being much greater in the case of ozone. Consideration is given to the reaction mechanism.
Perturbed Hartree—Fock Calculations. III. Polarizability and Magnetic Properties of the HF Molecule
Authors: Stevens Richard M. , Lipscomb William N.
Published: January 2005

Optimal basis sets within the perturbed Hartree—Fock theory have been found for the first-order wavefunction for the hydrogen fluoride molecule for the operators x, z, Mx (F), and Mx (H). These sets have yielded calculated values of the polarizability components, magnetic susceptibility, magnetic shielding at H and F, rotational magnetic moment and spin rotational constants of both H and F. Excellent agreement with experimental molecular-beam values is found for the rotational magnetic moment and the spin rotation constants. Good results were obtained for the magnetic properties only if the origin is chosen at the F atom. Maps are presented for the first-order change of the electron density in the presence of an electric field, but, owing to the asymmetry of the charge distribution, reliable maps of the first-order induced current density in the presence of a magnetic field could not be obtained.
Partial Pressures in Equilibrium with Group IV Tellurides. II. Tin Telluride
Authors: Brebrick R. F. , Strauss A. J.
Published: January 2005

The partial pressures of SnTe(g) and Te2(g) in equilibrium with SnTe(c) have been measured as a function of the temperature and composition of the solid phase by an optical absorption method. At 806°C, the maximum melting point of SnTe(c), the partial pressures of SnTe(g) and Te2(g) are 0.86 and 0.3 Torr, respectively. Between 727° and 806°C, the partial pressure of SnTe(g) is given by log p (Torr)=−[(10.19±0.26)×103]/T∘K+(9.38±0.26), independent of the composition of SnTe(c) within our experimental error of about 3%. The difference between the standard free energies of formation of SnTe(c) and SnTe(g) from Sn(g) and Te2(g) is therefore ΔG∘[12 SnTe (c)]−ΔG∘[12 SnTe (g)]=−23.31+14.87 (10−3)T kcal/g−atom. Combining this result with the value of ΔG°[½ SnTe(c)] obtained from the electrochemical data of McAteer and Seltz gives ΔG∘[12 SnTe (g)]=−27.34+6.81 (10−3)T kcal/g−atom. The partial pressure of Te2(g), which varies strongly with the composition of SnTe(c), has been determined for samples of seven different compositions within the SnTe(c) solidus field. Solidus temperatures in good agreement with those found by an independent method are obtained from the results. These results have also been used to obtain relative partial molal enthalpies of Sn and Te in SnTe(c) as a function of temperature and composition, and in addition they are discussed in terms of the disorder in SnTe(c).
Structure of the Aqueous Pertechnetate Ion by Raman and Infrared Spectroscopy. Raman and Infrared Spectra of Crystalline KTcO4, KReO4, Na2MoO4, Na2WO4, Na2MoO4·2H2O, and Na2WO4·2H2O
Authors: Busey R. H. , Keller O. L.
Published: January 2005

The Raman crystal spectra of KTcO4, KReO4, Na2MoO4, Na2WO4, Na2MoO4·2H2O, and Na2WO4·2H2O, and the Raman aqueous spectra of TcO4— and MoO42— have been observed. Infrared spectra of Nujol mulls of all the salts were measured in the rock salt region. Infrared spectra in the CsBr region were also obtained for Na2MoO4 and Na2WO4. For the tetrahedral ions (Td symmetry) of the latter two salts v2(e)>v4(f2), which represents an inversion of the usual order. Examination of all the spectra leads to the conclusion that the Raman spectrum of aqueous pertechnetate ion, which shows only two lines, represents the spectrum of tetrahedral TcO4— ion perturbed by the close association of water molecules. The appearance of two instead of four Raman lines in the spectrum is shown to result from the accidental degeneracy of v1(a1) and v3(f2) vibrations. The v2(e) line is not detected probably because of its low intensity and broadness. The observation of three rather than the expected four Raman lines for molybdate ion is similarly believed to be due to the low intensity and broadness of the v2(e) line. This explanation is also offered as an alternative explanation for the absence of the fourth line in the Raman spectrum of ReO4—(aq) and WO42—(aq) to that previously given, namely, that v2(e) and v4(f2) are sufficiently close together that they are unresolved.
Spectroscopy of Silicon Carbide and Silicon Vapors Trapped in Neon and Argon Matrices at 4° and 20°K
Authors: Weltner William , McLeod Donald
Published: January 2005

The numerous molecules vaporizing from silicon carbide at 2600°K and from silicon at 2300°K have been trapped in neon and argon matrices at 4° and 20°K and studied spectroscopically in the infrared, visible, and near-ultraviolet regions. The Si2 and SiC2 molecules have been observed, and less definitely, also Si2C, Si2C3, Si3, and Si4. In the case of silicon carbide vaporization, the absorption spectrum of SiC2 appears strongly at 4963 Å in neon and 4993 Å in argon as compared with 4977 Å in the gas. The spectrum agrees with the gaseous observations of McKellar and Kleman, but with the addition of three weak but distinct bands. It is interpreted as a 1Πu←X1Σ+ transition where the vibrational assignments in these states are now as follows: 1Σ+, ν1″=853, ν2″=300, ν3″=1742 cm—1; 1Π, ν1′=1015, ν2′=230, ν3′=1461 cm—1. The vibrational structure in the upper state is anomalous in that it requires a large positive value for x13′. The spectrum of symmetrical Si2C is believed to occur at 5300 Å in argon with ν1′=500 cm—1. An extensive absorption spectrum between 6500 Å and 5300 Å is attributed to Si2C3 and has been partially analyzed. The infrared spectra of these matrices confirm the ground state frequencies of SiC2 and lead to a tentative assignment of the Si2C3 frequencies. In the case of silicon vaporization, 17 vibrational levels in the upper state of the 3Σu—←X3Σg— transition of Si2 at 4000 Å, formerly seen in the gas by Douglas and by Verma and Warsop, have been observed. Two other weak systems of bands at 4660 and 5700 Å have been tentatively attributed to Si3 and Si4, respectively. Other regularities in the carbon, silicon, and silicon—carbon molecular series are discussed.
Swarm Measurement of Cross Sections for Dissociative Electron Capture in Heavy Water, Chlorobenzene, and Bromobenzene
Authors: Stockdale J. A. , Hurst G. S.
Published: January 2005

One established method for the measurement of the cross section for electron capture involves the introduction of small quantities of the gas under study (sample gas) into a carrier gas, which determines the distribution of electron energies for specified values of E/P. A summary of the available information on the distribution of electron energies in ethylene, nitrogen, and argon shows that for E/P values ranging from 0 to 2.0 V cm—1 Torr—1 the three carrier gases can be used to cover the important range of electron energies between thermal energy and 10 eV. This method has been used to study dissociative electron capture in D2O, C6H5Cl, and C6H5Br. Measurements show that the values for the energy integrated dissociative capture cross sections are approximately 4.6×10—18 cm2 eV for D2O, 1.4×10—17 cm2 eV for C6H5Cl, and 5.7×10—17 cm2 eV for C6H5Br occurring at electron energies near 6.5, 0.76, and 0.70 eV, respectively. That the low-energy processes in C6H5Cl and C6H5Br correspond to dissociative capture has been confirmed by the appearance of Cl— and Br— in a negative-ion time-of-flight mass spectrometer.
Electronic Structure, Spectra, and Magnetic Properties of Oxycations. V. The Electronic Spectra of Some Vanadyl Complexes
Authors: Ortolano T. R. , Selbin J. , McGlynn S. P.
Published: January 2005

The observation of four low-intensity absorption bands below 20 000 cm—1 for the C2v molecule vanadyl bisacetylacetonate is verified and four such bands are reported for C4v vanadyl species. The likelihood of these four bands representing the whole of the d—d series and the plausibility of understanding the splitting of the crystal field levels in the C4v molecules in terms of a spin—orbit coupling mechanism is discussed. The time course of the oxidation V(iv) to V(v) has been followed spectrally; the results identify the d—d series of transitions and suggest that the ∼25 000 cm—1 transition is charge transfer in nature. The paper should be regarded as a critique of two alternative energy-level schemes of the vanadyl ion, that scheme which is proposed herein being heavily favored by the arguments presented.
Band Shape of the OH Stretching Vibration in Aliphatic Alcohols. Evidence for the Occurrence of an Intramolecular Interaction
Authors: Saier Eleanor L. , Cousins Lauren R. , Basila Michael R.
Published: January 2005

The band shape of the OH stretching vibration in a series of aliphatic alcohols has been investigated. The asymmetric shape which occurs in the majority of alcohols is due to an overlapping band on the low-frequency side of the major band. The asymmetry, which is concentration independent, is shown to occur in the deuterated species and in the first overtone vibration as well. The temperature dependence of the minor band has been investigated and a negative ΔH found which suggests that the minor band is due to an intramolecular interaction. A model is proposed in which the hydrogen of a CH group at the γ position interacts with the lone pair electrons at the hydroxyl oxygen atom. The model qualitatively predicts the correlation between the formation constant and the number of available γ-CH groups which is experimentally observed.
Osmotic Flows in Charged Membranes. II. Thermo-Osmosis
Authors: Kobatake Yonosuke , Fujita Hiroshi
Published: January 2005

Thermo-osmotic flow rates of an electrolyte solution through a porous charged membrane separating two solutions which are at different temperatures but have the same concentration is studied theoretically, using a capillary model for the membrane. The assumptions used are that the Debye-Hückel approximation is applicable for the ion distribution in the double layer formed near the fixed charges on the capillary wall, and that the thickness of the double layer is much smaller than the capillary radius. The steady-state solutions of a set of differential equations derived are obtained subject to appropriate external conditions. It is shown that plots for the flow rate of fluid against the logarithm of the concentration of the outer solution give a bell-shaped curve. This theoretical curve follows well the Carr—Sollner data of the thermo-osmosis for various electrolyte solutions.

The thermo-osmosis is an electro-osmotic flow caused by the electric field which is set up in the membrane so that no net electric charge is allowed to be transported across the membrane. The dependence of the electro-osmotic coefficient on salt concentration is the primary cause for the characteristic behavior of the thermo-osmosis in charged membranes. It has been shown in Part I of this series that this effect is also responsible for the anomalous osmosis.
Photolysis of Nitric Oxide
Authors: McGee J. J. , Heicklen Julian
Published: January 2005

Electronically excited NO (A 2Σ) was produced by irradiation with the 2144- and 2265-Å lines of the cadmium arc at nitric oxide pressures from 20 to 600 mm. The products were nitrogen and nitrogen dioxide. A pressure drop accompanied the reaction equivalent to the nitrogen produced. The mechanism is given. The quantum yield of nitrogen formation was independent of irradiation time and incident intensity. Its falloff with pressure was less than a factor of two, even at 20 mm. These results, when combined with the radiative lifetime measurements of Callear and Smith, show that removal of NO (A 2Σ) occurs on nearly every collision.
Isotropic Shifts of Some Ionic Complexes of Cobalt(II) and Nickel(II) : Evidence for Ion Pairing
Authors: La Mar Gerd N.
Published: January 2005

Isotropic proton resonance shifts have been observed for the ionic complexes, [Bu4N][φ3P)CoI3] and [Bu4N][φ3P)NiI3]. In addition to the phenyl (φ) proton shifts for the complex anions, isotropic shifts were observed for the cation protons as well. These shifts for the tetra-n-butylammonium cations are interpreted as arising solely from a pseudocontact interaction with the metal in the complex anion through partial ion pairing in the deuterochloroform solutions. From the magnitudes of the shifts for the butyl protons, an estimate is made for the relative extent of g-tensor anisotropies for the two anionic complexes. The observed shifts for the phenyl protons are interpreted as arising from both contact and pseudocontact interactions. Based on the postulate that the unpaired spin will distribute itself in a like manner in a given ligand whether attached to cobalt or nickel, and using the estimate of the relative anisotropies of the two metals, the phenyl proton shifts are separated into their respective contact and pseudocontact contributions. The resulting unpaired spin densities on the phenyl rings compare well with those reported for the related bis(triphenylphosphine) complexes.
Formation of NH from Shock-Heated Ammonia
Authors: Cann M. W. P. , Kash S. W.
Published: January 2005

Mixtures of ammonia in xenon were shock heated to temperatures in the range 2900° to 9600°K and the radiation from NH was monitored at 3360 Å. It was found that the production of NH (A3II) was second order in initial ammonia concentration within experimental error, and could be described by a rate constant K=4×10—14 exp ( —54 000/T) cm3 molecule—1·sec—1. Significant changes in shape of the radiation profiles were observed at different temperatures; in particular it was found that NH normally decayed at two different rates, one being half as great as the other. The results are discussed and compared with recent measurements made by other authors, revealing some discrepancies that could not be explained.
Electronic Processes in Solutions of Alkali Metals in Liquid Ammonia. I. A Model Including Two Diamagnetic Species
Authors: Arnold Emil , Patterson Andrew
Published: January 2005

The various models which have been proposed for metal—ammonia solutions are reviewed in the light of the available experimental data. It is shown that, in order to account quantitatively for the electrical and magnetic properties of these solutions, it is necessary to assume two different species containing paired electrons. A new model postulated for metal—ammonia solutions consists of the following five species in equilibrium: metal ions, polarons or e centers, M centers, M2 centers, and M′ centers. An M′ center is assumed to consist of an electron trapped in the field of an M center. The equilibrium concentrations of the species which are assumed to be present in metal—ammonia solutions are calculated for different metal concentrations. The calculated values agree well with experimental transference numbers and magnetic susceptibilities. The expressions for the equilibrium constants are related to the binding energies of electrons trapped by the various centers, and the relative values of the trapping energies are estimated from the magnetic and transference data. It is concluded that the main contribution to the binding in all centers arises from the polarization of the dielectric. The estimate of the concentration at which a narrow conduction band may begin to form agrees with the experimental temperature coefficient of conductivity which has a sharp maximum at 0.8M.
Electronic Processes in Solutions of Alkali Metals in Liquid Ammonia. II. Electrical Conductivity
Authors: Arnold Emil , Patterson Andrew
Published: January 2005

An attempt has been made to account for the electrical conductivity in sodium/liquid-ammonia solutions throughout the entire range of concentrations. The conductivity in dilute solutions is calculated from the Onsager—Kim theory, adjusted for the effective concentrations of conducting species. In the intermediate concentration range a conduction mechanism is proposed, according to which the conduction proceeds by the jumping of electrons from M centers to metal ions. In order to obtain the mobility, the system of the two nuclei and the electron is treated like a hydrogen molecule-ion immersed in a dielectric medium, and the jump frequency is calculated from the exchange integral appropriate for such a system. No arbitrary parameters are used in the theory. The calculated conductivity agrees well with the experimental data, from dilute solutions up to about 1M. The conductivity in concentrated solutions is calculated by assuming scattering of conduction electrons by screened metal ions. It is estimated that, although a narrow conduction band begins to form at concentrations of about 1M, the new structure is not complete, except at the highest concentrations. In order to account quantitatively for the observed conductivity above 1M, it is assumed that the conduction proceeds via a band formed by the overlap of wavefunctions in an excited level.
Molecular Distributions at Equilibrium. I. Theory of Equilibria in Scrambling Reactions and Interpretation of NMR Spectra
Authors: Matula David W. , Groenweghe Leo C. D. , Van Wazer John R.
Published: January 2005

Stochastic graph theory has been developed and applied to the interpretation of chemical equilibria resulting from scrambling reactions which lead to size distributions of molecules. By this means, deviations from random scrambling are treated in terms of the effect on any given site in a molecule of the environment of neighboring atoms within the molecule. This treatment is applied to molecular-distribution data on the glassy phosphates and to thermodynamic data on the aliphatic hydrocarbons. It is also shown to be the basis for interpretation of nuclear magnetic resonance data obtained on families of equilibrated compounds. A formal treatment of ring—chain equilibria is presented, and equilibrium constants for interactions between parts of molecules are related to the usual constants involving whole molecules. The concept of crowding of chain segments is employed in estimating the number of ring closures in infinite-network macromolecules (i.e., structures having as many branches as or more branches than correspond to the ``gel point'').
Electron Spin Resonance and Electronic Absorption Spectra of Rh II in ZnWO4
Authors: Townsend M. G.
Published: January 2005

The electron spin resonance (ESR) and electronic absorption spectra of Rh II in a single crystal of ZnWO4 have been recorded. Excited state energies determined from the electronic spectrum are used in an attempt to interpret the measured ESR g values. The orientation of the Rh II magnetic axes relative to the crystalline axes has been measured, and from the magnitude of the hyperfine splitting for 103Rh(I=½), determined along each each axis, values of P=2γββN〈r—3〉 and κ are calculated.
Magnetic and Electrical Properties of Small Diatomic Molecules. I. Diamagnetic Susceptibility, Proton-Shielding Constant, and Electric Polarizability of the Hydrogen Molecule
Authors: Hoyland James R.
Published: January 2005

An unambiguous exact variational procedure is given for the calculation of certain weak interaction energies starting from any given approximate ground-state wavefunction. The method is illustrated by numerous calculations on the hydrogen molecule using five different ground-state wavefunctions.
Thermoelectric Potentials in Molten Bi–BiI3 Solutions
Authors: Raleigh D. O. , Topol L. E.
Published: January 2005

The Seebeck coefficient of Bi–BiI3 melts was measured over the complete composition range from pure BiI3 to pure Bi. Results at 400°, 450°, 500°, and 550° are reported. Absolute Seebeck coefficients ranging from —53 to +125 μV/°C were encountered, the data exhibiting a maximum at about 40 mole % Bi and minima at approximately 10 and 85 mole % Bi. The results, interpreted in the framework of irreversible thermodynamics, are consistent with metallic electrical conduction in the metal-rich compositions and a mixture of conduction by ions and electron exchanges in the salt-rich and intermediate compositions.
Quantum Cell Model. I. The Uniform Potential Approximation
Authors: Hillier Ian H. , Walkley John
Published: January 2005

The equation of state and related thermodynamic properties are calculated for a uniform potential approximation to the Lennard-Jones cell theory model employing quantum statistical mechanics. The simple form of the cell potential for this model allows the energy eigenvalues to be readily computed. A comparison to the available experimental compressibility data for hydrogen and deuterium is made.
United-Atom Approximation Applied to Argonlike Molecules. I. Hydrogen Sulfide
Authors: Banyard K. E. , Hake R. B.
Published: January 2005

The united-atom approximation was applied to H2S and also to the systems HS— and S——. The wavefunction obtained for H2S was used to calculate the molar diamagnetic susceptibility and the coherent x-ray scattering factor for the gaseous form of the molecule. Values are also reported for the ``breathing'' force constant for H2S and for the theoretical bond length for both H2S and HS—.

Within the present approximation a calculation was made of the bond energy for H2S dissociating into HS and S. The proton affinities for HS— and S—— were also determined.

Where possible, a comparison was made with experiment. In general, except for the proton affinities and bond-energy calculation, the united-atom model applied to H2S was reasonably successful. A comparison was also made between the present radial density and the density of electrons for H2S provided by the model of ``floating'' hydrogen densities. This comparison helps to substantiate the claim made earlier, namely, that the model of ``floating'' hydrogen densities will provide a very reasonable radial distribution of electrons within molecules of the form XHn.
Spectra and Energy Levels of Eu3+ in Y2O3
Authors: Chang N. C. , Gruber J. B.
Published: January 2005

The absorption and fluorescence spectra of Eu3+ in single crystals of Y2O3 have been observed and analyzed. The intermediate-coupling free-ion energy levels for Eu3+, including the effects of the 46 singlet states of the 4f6 configuration, are presented for all levels appearing below 41 000 cm—1. The results obtained by including the singlet states in the free-ion energy level calculations are discussed. Values of E1=6217.84 cm—1, E2=38.94 cm—1, E3=630.15 cm—1, and ζ=1343.1 cm—1 are found to give the best over-all agreement between the observed and calculated energy levels.
Optical Properties of Multilayer Colloids
Authors: Morriss R. H. , Collins L. F.
Published: January 2005

The theory of Aden and Kerker on the scattering of electromagnetic waves from two concentric spheres has been applied to the interaction of light with two-layer metallic colloids. Starting with gold nuclei 59 Å in ``diameter,'' silver layers 5 to 220 Å in thickness have been grown epitaxially. The optical absorption spectra of these hydrosols containing two-layer particles are compared with the spectra calculated from the theory of Aden and Kerker. The calculated and experimentally observed spectra are in relatively good agreement in the wavelength range 380–700 mμ. Large discrepancies occur between 300 and 380 mμ for hydrosols containing particles with silver layers less than 15 Å. This is attributed to a deviation of the silver refractive index from that of bulk silver for these layer thicknesses. The experimental absorption peaks are generally found to be broader than the calculated results. This is due in part to size and shape anisotropy. Other possible factors are lattice imperfections and trapped ions at the gold—silver interface.
Studies of Hydrogen-Bonded Systems. I. The Electronic Structure and the Double Well Potential of the N–H···N Hydrogen Bond of the Guanine—Cytosine Base Pair
Authors: Rein Robert , Harris Frank E.
Published: January 2005

For hydrogen-bonded complexes we outline an LCAO—MO—SCF method which considers explicitly the σ electrons of the hydrogen-bond region and the π electrons of the surrounding ligands. The protonic potential function is obtained by solution of these SCF equations for a series of proton positions. The electronic structure and the potential function of the middle N–H···N hydrogen bond of the guanine—cytosine base pair have been calculated by this method. The integrals appearing in the problem have been approximated semiempirically and several alternative approximations have been tested. The calculated π electronic structure and orbital energies conform with the result of a previous SCF calculation treating the H bond parametrically. The calculated charge distribution in the H-bond region is in agreement with the mainly covalent character of the N–H bond and mainly electrostatic character of the H···N bond for equilibrium configuration. The empirical and electrostatic models agree well with our model with respect to the qualitative features of the double well potential characterizing a H bond. With respect to the magnitude there is a substantial decrease in the potential barrier calculated by us in comparison to that calculated from classical electrostatic interactions. This decrease can be partly related to the delocalization effect which is treated in our model and partly to the self-consistent charge distribution utilized for the calculation of electrostatic interactions, which in the simpler models are estimated with more arbitrariness.
NMR Determination of the Hydration Numbers of Cations in Aqueous Perchlorate Solution
Authors: Alei Mohammed , Jackson Jasper A.
Published: January 2005

In an aqueous solution of a paramagnetic ion which exchanges water rapidly between its first coordination sphere and the solvent, a single oxygen-17 NMR signal is observed shifted from its normal position in pure H2O. The magnitude of the shift is a measure of the ratio of the paramagnetic ion concentration to total (labile) water in the system. If a second ion for which the first coordination sphere water is sufficiently nonlabile (τ>∼10—4 sec) is added to the system, the decrease in the water available to interact with paramagnetic ions due to water retained in the nonlabile environment will produce an increase in the shift in the labile H217O resonance by the paramagnetic ion. The application of this ``molal shift'' method to the determination of the hydration numbers of certain diamagnetic and paramagnetic cations in aqueous solutions is demonstrated and discussed.
Heat of Formation of Be2O(g) by Mass Spectrometry
Authors: Theard Lowell P. , Hildenbrand Donald L.
Published: January 2005

Mass spectrometric Knudsen effusion experiments have provided evidence for the existence of the suboxide species Be2O(g) in the equilibrium vapor above crystalline beryllium oxide at temperatures around 2300°K. Be2O+ ions appear to be formed both by simple ionization of Be2O(g) and by fragmentation of a larger molecule. The relative importance of the two processes has been shown to be temperature dependent. An average value of —8±10 kcal/mole was obtained for ΔHf°298[Be2O(g)] from third-law calculations for three equilibria.

Mass spectral data are given for the equilibrium vapor above beryllium oxide at 2380°K in the presence of tungsten.
Franck—Condon Factors for Polyatomic Molecules
Authors: Sharp T. E. , Rosenstock H. M.
Published: January 2005

General expressions are derived for calculating Franck—Condon factors for most transitions of polyatomic molecules (excluding transitions between linear and bent configurations) in the harmonic oscillator approximation. The derivation employs the method of generating functions and also linear transformation of normal mode coordinates between initial and final states. Input data required in the general case are geometries, frequencies, and vibrational force fields for the initial and final states. Explicit algebraic expressions are presented for the transition between linear, symmetric, triatomic initial and final states. The results are used to show that fragmentation cannot result from direct vertical ionization to the ground electronic states of CS2+ and CO2+ or to the excited 2IIu state of CO2+. An attempt was made to fit the experimental photoionization data for C2H2 and C2D2. This resulted in an estimated increase of 0.05 Å in the equilibrium C–C bond distance and no change in the C–H bond distance in C2H2+ as compared to C2H2.
Nuclear Quadrupole Resonance in Paramagnetic PrCl3
Authors: Hughes W. E. , Montgomery Charles G. , Moulton W. G. , Carlson E. H.
Published: January 2005

The 35Cl and 37Cl pure quadrupole resonances have been observed in PrCl3. At 4.2°K the frequencies are 4.5667±0.0001 and 3.6001±0.0001 Mc/sec for 35Cl and 37Cl, respectively, and at 77°K they are correspondingly 4.5607±0.0001 and 3.5955±0.0002 Mc/sec. The orientation dependence of the Zeeman split quadrupole resonance frequencies has been measured at 4.2°K and the components of the field gradient tensor determined. The asymmetry parameter η is 0.58±0.02. No evidence of a transition to an ordered state was observed, and it is concluded that PrCl3 remains paramagnetic down to 1.7°K. A shift in the Zeeman frequencies with temperature was found and is attributed to the hyperfine interaction of the Cl nuclei with the Pr electronic ground state. The results are compared with the results of a calculation of the field gradient from a point charge model, and are also discussed in terms of covalent bonding.
Effects of Hydrostatic Pressure and Temperature on Spin Exchange between Free Radicals in Solution
Authors: Edelstein N. , Kwok A. , Maki A. H.
Published: January 2005

The paramagnetic resonance linewidths of the di-tert-butyl nitroxide free radical have been measured as a function of hydrostatic pressure and of temperature in the pure hydrocarbon solvents methylcyclohexane, n-pentane, and propane. These data are reported at conditions under which intermolecular spin exchange gives the principal contribution to the linewidth. Deviations of the linewidth from a linear dependence on T/η, where η is the liquid viscosity, are attributed to a dropping off of p, the average exchange probability per radical—radical encounter, from unity at low values of η/T. The viscosity and temperature dependence of p is found to be p=1—exp(—aη/T), where a is a positive constant which depends upon the solvent. This form of p(η,T) is shown to arise from a theory which treats the exchange reaction as a unimolecular kinetic process which may occur, however, only during a radical—radical encounter in the liquid. Radical—oxygen exchange rates were also measured in methyl cyclohexane and the same theory explains the η and T dependence.
On the Kirkwood Superposition Approximation
Authors: Cochran Russell V. , Lund L. H.
Published: January 2005

When the Kirkwood superposition approximation for the triplet distribution function is used in the Born—Green equation for the molecular pair distribution function, the fourth virial coefficient of a gas is given incorrectly. In view of this, a suggestion for improving the approximation has been investigated. A suggestion, due to G. H. A. Cole, that better results could be obtained by using a second-order integrodifferential equation of the Born—Green type with the superposition approximation used for both the triplet and quadruplet distribution functions has been investigated, and results for hard-sphere model show that this method gives considerably less reliable results for the fourth virial coefficient than those obtained by simply using the superposition approximation in the first-order Born—Green equation.
Matrix Reaction of Methylene with Nitrogen to Form Diazomethane
Authors: Moore C. Bradley , Pimentel George C.
Published: January 2005

Isotopic labeling experiments show that the photolysis of either diazomethane or diazirine isolated in solid nitrogen produces CH2 molecules which subsequently react with neighboring N2 molecules to form diazomethane. Small frequency shifts and splittings in the spectra of diazomethane so produced provide evidence for three different matrix sites for diazomethane isolated in nitrogen.
Molecular Structure of CF3PCl4: Infrared and Raman Spectra
Authors: Griffiths James E.
Published: January 2005

The basic structure of the CF3PCl4 molecule has been established from a study of its vibrational spectrum. The CF3 group occupies an axial position in the trigonal bipyramidal structure but no information is obtained concerning the height of the barrier to internal rotation.

All of the active fundamentals are assigned in the Raman spectrum (Δv=50–1500 cm—1) and supplementary data were obtained from a pressure limited gas-phase study of the infrared spectrum (2000–280 cm—1). Fundamental frequencies are: a1=1145, 743, 493, 374, 324, 260; e=1168, 587, 543, 304, 239, 193, and 94 cm—1.

The compound is unstable thermally decomposing into CF3Cl, CF3PCl2, PCl3, and PCl5.
Optical Properties of Radiolytic Fragments in Pure and Silver-Doped NaNO3 and KNO3
Authors: Cunningham Joseph
Published: January 2005

Absorption bands attributed to nitrogen—oxygen radiolytic fragments in pure NaNO3 and KNO3, grew much more slowly when crystals containing 0.4 ion % of Ag+ were irradiated with x or γ rays at 77°K. Competition between Ag+ and other species for available low-energy electrons was indicated in the silver-doped crystals by growth of an absorption band attributable to silver atoms. Radiation-induced absorbance above 300 mμ in pure NaNO3 and KNO3, and its response to optical bleaching, is shown to be explicable in terms of Gaussian absorption bands arising from three radiation-produced electron-excess centers. Observed results, including correlations between the centers and their resistance to annealing at 300°K, can be accounted for by proposing NO22—, NO32—, and N2O32— as the identities of the electron-excess species.
Automatic Calculation of the Transport Collision Integrals with Tables for the Morse Potential
Authors: Smith Francis J. , Munn R. J.
Published: January 2005

A computer program is described for calculating the classical and quantal JWKB Chapman—Enskog collision integrals Ω(l,s) (T) for any reasonable interaction potential. With the program it was possible in about 10 or 15 min on a fast computer to calculate more than 500 collision integrals covering a complete range of values of l, s, and T to an accuracy of better than 1 part in 1000. This was made possible by the use of efficient numerical techniques such as weighted Gaussian quadratures and by the general optimization of all numerical and logical processes.

The program was checked against previous tables for the Lennard-Jones and Stockmayer potentials. It was also used to list values of the collision integrals and Kihara's corrections to the coefficients of viscosity, thermal conductivity, diffusion and thermal diffusion for the Morse potential.
Diffusion and Heterogeneous Reaction. VI. Surface Recombination in the Presence of Distributed Atom Sources
Authors: Wise Henry , Ablow Clarence M. , Sancier Kenneth M.
Published: January 2005

A theoretical analysis is made of the simultaneous removal of atoms by a first-order heterogeneous reaction and their generation by a second-order gas-phase reaction. Such a model is found applicable to a system in which hydrogen atoms recombine on the walls of a cylindrical vessel in the presence of hydroxyl radicals which may interact in the gas by reaction with hydrogen molecules. The perturbation of the hydrogen-atom-concentration profile in the cylinder due to OH as measured by electron spin resonance spectroscopy is employed to calculate the rate constant for the gas-phase reaction OH+H2→H2O+H.
Neutron-Diffraction Study of the Structure of Potassium Oxalate Monohydrate: Lone-Pair Coordination of the Hydrogen-Bonded Water Molecule in Crystals
Authors: Chidambaram R. , Sequeira A. , Sikka S. K.
Published: January 2005

A single-crystal neutron-diffraction study of the structure of potassium oxalate monohydrate has been made. The structure consists of oxalate ions hydrogen bonded by the water molecules into infinite linear chains which are held together by electrostatic interactions with the potassium ions. The oxalate ion is planar, and the H–O–H angle of the water molecule is 107.9°±4.3°. The O–H distance is 0.963±0.029 Å in a hydrogen bond of length 2.744±0.017 Å, and the O–H···O angle is 169.1°±2.6°. The coordination of the water molecule is unusual with the two hydrogen atoms and two potassium ions lying almost in a plane around the water oxygen atom. A classification of the hydrogen-bonded water molecules in hydrates with respect to their lone-pair coordination reveals that K2C2O4·H2O may be the only reported structure of the type in which neither of the lone pairs of the hydrogen-bonded water molecule is specifically directed despite the availability of metal ions in the structure.
Knight Shifts and Relaxation Times of Alkali-Metal and Nitrogen Nuclei in Metal—Ammonia Solutions
Authors: O'Reilly D. E.
Published: January 2005

Knight shifts of 7Li, 23Na, 87Rb, 133Cs, and 14N in alkali-metal—ammonia solutions have been measured at 300°K and in the concentration range 0.03 to 1 mole liter—1. 23Na NMR has been observed at Na concentrations down to 0.003 mole liter—1 at 300°K and in the range 0.03 to 4 mole liter—1 at 274° and 240°K. 14N shifts are reported for concentrations from 0.008 to 4 mole liter—1 at 300° and 240°K. Linewidths of 87Rb and 133Cs have been obtained at 300°K in the concentration range 0.03 to 0.8 mole liter—1. At 0.35 mole liter—1 and 300°K the shifts of Li, Na, Rb, and Cs are 9, 72, 450, and 900 ppm, respectively, to lower magnetic field. Shifts of 14N are nearly independent of metal at 300°K.

The concentration and temperature dependence of 23Na Knight shift data at concentrations up to 0.4 mole liter—1 may be quantitatively interpreted by the following reactions: M⇌M++e−,M+e−⇌M−,where M represents the ``monomer'' species and (2) is the spin-pairing reaction. The 14N spin density at unpaired electron is essentially independent of alkali metal and concentration up to 0.6 mole liter—1 and equal to 0.88±0.11 a0—3 at 300°K. The electron spin density at 23Na is calculated to be ≥8×10—3 a0—3 approximately independent of temperature and concentration.

The lifetimes of the Rb and Cs monomers at 300°K and 0.06 mole liter—1 are ≤3 and ≤4 μμsec, respectively, as determined from NMR linewidth measurements. The monomer lifetime decreases sharply with increase in metal concentration.
Angular Dependence of Long-Range Proton Coupling Constants Across Four Bonds
Authors: Barfield Michael
Published: January 2005

A theoretical treatment of long-range proton spin—spin coupling constants, 4JHH′, across four bonds in saturated and unsaturated hydrocarbons is presented. Using the valence bond formalism, explicit theoretical expressions for the `direct'' and ``indirect'' contributions to 4JHH′ are obtained. By introducing a semiempirical criterion for estimating the pertinent exchange integrals, the angular dependence of the ``indirect'' effect is evaluated. The calculated results correlate a wide range of coupling-constant data including those experimental results for which existing theoretical treatments are inadequate. The comparison of the calculated with the experimental data suggests that the ``direct'' contribution to long-range coupling constants in saturated systems is negative in sign and is most important in the vicinity of the eclipsed conformations.
Effect of Molecular Structure on the Ionization Probabilities of Aromatic Molecules
Authors: Deverse F. T. , King A. Bruce
Published: January 2005

The ion yield vs electron energy has been measured for the parent ions of a number of aromatic compounds immediately above the threshold. From the slopes of the linear portion of these curves, the relative ionization probability per molecule is determined. It is found that the ionization probabilities increase with the size of the π-electron system and correlate quantitatively with the electron-donating ability of the substituents. Disubstituted benzenes show an additivity of the effect of the substituents on the ionization probability with the meta isomer giving slightly higher values than the ortho and para isomers. Polyphenyl methanes and ethanes show considerably greater ionization probability than fused aromatic compounds with the same number of π electrons.
Analysis of NMR Spectra by Least Squares
Authors: Castellano S. , Bothner-By A. A.
Published: January 2005

An iterative method for the least-squares analysis of an observed high-resolution NMR spectrum is described. The method is applicable even if not all lines are assignable, is not affected by symmetry in the Hamiltonian, yields an estimate of the ellipsoid of error, and converges relatively rapidly to a predetermined assignment. A computer program based on this method is described. Effectively infinite chemical shift may be introduced permitting the analysis of ABXY, etc., spectra. An illustration of its application to the analysis of the proton spectrum of 2-benzoylpyridine is given.
Contribution of Interionic Forces to the Thermal Conductivity of Dilute Electrolyte Solutions
Authors: Bearman Richard J.
Published: January 2005

The contribution λion of interionic forces to the thermal conductivity of dilute electrolyte solutions is calculated on the basis of a model previously proposed and is found to vary as k3 or (concentration)3/2 according to the expression λion=13κ(e2/εT) ∑ βzβ2cβDβ, where k is the inverse Debye length, e is the electronic charge, ε is dielectric constant of solvent, z is charge number, cβ is concentration of dissolved ion β in units of number of ions per cubic centimeter, and Dβ is the self-diffusion coefficient of the ion.
Electron Spin Resonance Study of Radical Pairs Trapped in Irradiated Single Crystals of Dimethylglyoxime at Liquid-Nitrogen Temperature
Authors: Kurita Yukio
Published: January 2005

The ESR spectra of x-irradiated single crystals of dimethylglyoxime have been measured at 77°K. An analysis of the spectra reveals that two paramagnetic species are produced by the irradiation. One is an iminoxy radical C(CH3)NOH–C(CH3)NO(M). The other, unstable at room temperature and containing two coupling nitrogen nuclei, is a radical pair with the mean distance between the two unpaired electrons of 5.6 Å. The absorption corresponding to the ΔM=2 transition of the radical pair has been observed in polycrystalline samples. The radical pair is tentatively identified to be the one consisting of adjacent radicals M···M along the crystallographic a axis.
Long-Range Spin—Spin Interaction between Nuclei in the Saturated Compounds
Authors: Koide S. , Duval E.
Published: January 2005

The importance of the intra-atomic Hund coupling between electron spins is emphasized to account for the general features of the electron-coupled interaction between nuclear spins separated by several atoms. This seems to be quite consistent with the experimental results, especially with the appearance of the negative coupling constants in many of the long-range cases. By using the simple valence-bond method, the effect of the Hund couplings on the coupling constant between nuclear spins is expressed in terms of the various exchange integrals between adjacent electron orbitals for the cases of one, two, and three intervening atoms.
Photoionization and Absorption Cross Sections of O2 and N2 in the 600- to 1000-Å Region
Authors: Cook G. R. , Metzger P. H.
Published: January 2005

Absolute photoionization and absorption cross sections of O2 and N2 have been measured in the 600- to 1000-Å region using a 1-m Seya—Namioka scanning vacuum ultraviolet monochromator with a resolution of 0.5 Å in the first order and the Hopfield continuum background light source. A path length of 40.6 cm was used with simultaneous detection of ion current and photon flux. The absolute photon flux was determined by calibrating the ion chamber with the rare gases Ar, Kr, and Xe. In O2, the spectrum at longer wavelengths consisted of band absorption superimposed on a continuum, and, in the short wavelength region, by the continuum alone. Many of the O2 bands were broad, and absorption coefficients were independent of pressure. In N2, the spectrum showed many closely spaced narrow absorption bands down to about 750 Å, broad pre-ionized bands of the Hopfield Rydberg series to about 670 Å, and a smooth ionization continuum at shorter wavelengths. Pressure dependence of the coefficients in the region of the narrow bands was found to be a minimum if the measurements were made at absorption minima. Strong absorption continua were found underlying the band structure below 820 Å, and several weak continua were observed in the longer wavelength region. For each molecule, the photoionization cross section was similar to the absorption cross section but of different magnitudes, indicating an ionization efficiency of less than 100%. Strong gas fluorescence was observed in N2 when the wavelength of the incident radiation was decreased to 661 Å. The fluorescent radiation in O2 was weaker than in N2 and showed a gradual rise in intensity below 736.5 Å.
Emission Spectrum of NO in Solid Rare Gases: The Lifetime of the a 4Π State and the Spectrum of the a 4Π→X 2Π and B 2Π→X 2Π Transitions
Authors: Frosch R. P. , Robinson G. W.
Published: January 2005

The emission spectrum of NO molecules trapped in solid argon and krypton has been excited with x rays. Two series of bands have been observed, the well-known β bands (B 2Π→X 2Π) and a series with estimated origin near 38 000 cm—1 believed to be the a Π524 → X Π322 transition. The lifetime of the assumed quartet state has been measured in solid Ne, Ar, and Kr and found to be 156, 93, and 35 msec, respectively, in these solids. These lifetimes are compatible with the above assignment of the bands. A least-squares fit has been made of the spectral data to obtain the 0–0 band positions and the vibrational constants of the NO molecule in the solid. The doublet—quartet bands are believed to arise from a spin—orbit mixing of the a Π524 state with the B′ Δ522 state. The possibility of observing high resolution spectra of the a Π4 − X Π2 Π4 − X Π2 transition in either absorption or emission is considered. The role of the a 4Π state of NO in photochemical reactions and in auroral and airglow spectra is briefly discussed.
Viscosity of Hydrogen, Deuterium, Methane, and Carbon Monoxide from —50° to 150°C below 200 Atmospheres
Authors: Barua A. K. , Afzal M. , Flynn G. P. , Ross J.
Published: January 2005

The absolute viscosities of H2, D2, CH4, and CO have been determined from measurements in a capillary-flow viscometer in the temperature range from —50° to 150°C and at pressures below 200 atm with an average precision of 0.1%. The accuracy of the measurements, with some exceptions, is estimated to be about 0.2%. Comparison of the H2 and D2 viscosities appears to confirm a difference between their intermolecular potentials.
ESR of Substituted Cyclobutane Anions
Authors: Jones M. T. , LaLancette E. A. , Benson R. E.
Published: January 2005

Paramagnetic anions of dicyanomethylene-2,2,4,4-tetramethylcyclobutanone (I) and bis-(dicyanomethylene)-2,2,4,4-tetramethylcyclobutane (II) were produced by electrolytic and chemical reduction. The ESR spectrum of II— indicates fast electron transfer between the two dicyanomethylene groups. 1,3-π-interaction and hyperconjugation are considered to be the predominant means of effecting the electron transfer.
Quadrupole Moment of OCS from Self-Broadening of Microwave Spectrum
Authors: Krishnaji  , Chandra Suresh , Srivastava Shyam Lal
Published: January 2005

Self-broadening of the microwave absorption line of OCS (J=1→2 transition) has been explained by taking dipole—dipole, dipole—quadrupole, and quadrupole—quadrupole interactions simultaneously. The value of the quadrupole moment of OCS comes out to be 7.1×10—26 esu. The temperature dependence of the linewidth has also been explained on the basis of these mixed interactions taking this value of the quadrupole moment of OCS.