bluuebunny/crossref_metadata_2025 huggingface dataset:
Substituted Benzene Spectra
Authors: Goodman Lionel , Shull Harrison
Published: January 2005

The low-lying π-electron excited states of substituted benzenes are examined from a semiempirical point of view, by using molecular orbital theory together with first-order configuration interaction as a basis. Different semiempirical parameters are introduced for the perturbations by a substituent upon states of different symmetry. Substituents exerting conjugative, inductive, and mixed effects are considered. Comparisons with experiment show that the experimentally observed facts concerning the effect of substitution upon the energy and intensity of these transitions are well accounted for by the theory. The relationship of the present treatment to that of the perimeter model introduced by Moffitt is discussed. The present model breaks down for very ``strong'' substituents when a higher-order configuration interaction treatment becomes essential.
Electronic Structure of Diborane
Authors: Yamazaki Masatoshi
Published: January 2005

The electronic structure of the ground state of diborane is discussed in terms of linear combinations of atomic orbitals-molecular orbitals from a basis consisting of the twelve-electron system with 1s electrons on borons collapsed into the nucleus. Exact values for all one- and two-center integrals are used, but approximations are made for many three- and four-center integrals. The dissociation energy is calculated as 0.29 au in poor agreement with the experimental value 0.816 au. The net charge on bridge hydrogen, on terminal hydrogen, and on boron is slightly negative, nearly neutral, and slightly positive, respectively. This is supported by experiments. For the central bonding linkage comparisons with other descriptions are made.
Vibrational Matrix Elements of NO
Authors: Breene R. G. , Todd M. N.
Published: January 2005

A potential function meeting certain qualitative criteria is developed from the Lippencott potential, a seven term expansion of this function being actually utilized. A three-term expansion of the dipole moment is used within the framework of familiar perturbation theory to obtain the vibrational-matrix elements for the fundamental and first four overtone transitions arising from each of the first eleven levels. The results of this calculation are utilized for a further investigation of the potential function, and the approximations involved are considered. This calculation has been programmed and carried out on the IBM 650 electronic data processing machine, and is readily adaptable to other diatomic molecules for which the requisite empirical data are available.
Analysis of Dielectric Loss in Two Urea Addition Compounds : The Hindered Single Axis Polar Rotator
Authors: Lauritzen John I.
Published: January 2005

The dielectric behavior of two real substances is related to their molecular structure by the application of a theory of the general type proposed by Hoffman. The two real substances are the urea addition compounds of 12-bromotricosane and 16-hentriacontanone, where the polar long-chain molecules exhibit dielectric loss through rotation about their long molecular axes between orientational sites. This dielectric loss has been measured by Meakins, who proposed a qualitative theory similar to the one used here.

Smith has determined the crystal structure of the urea addition lattice. The orientational sites of the polar molecules are determined by the potential energy of the crystalline field, which is estimated from the geometrical configuration of the lattice by a Lennard-Jones (6–12) potential.

The dielectric loss is calculated in terms of the energy minima and maxima of the potential energy. The energy minima and the differences between the energy maxima are evaluated by a fit of the experimental dielectric loss of 12-bromotricosane in urea. These values are in good qualitative agreement with the potential energy obtained from the crystal structure.

The temperature dependence of the dielectric properties of 12-bromotricosane in urea are predicted under certain assumptions. The validity of these assumptions and the applicability of the theory are investigated by considering the dielectric loss of 16-hentriacontanone in urea over a wide temperature range.
Electrochemical Behavior of the Palladium-Hydrogen System. III. Gas-Charged Palladium Alloys
Authors: Hoare James P. , Schuldiner Sigmund , Castellan Gilbert W.
Published: January 2005

Experimental evidence is presented to support the proposed difference in electrochemical properties of the β- and β′-palladium-hydrogen alloys. It is shown that the β-palladium-hydrogen electrode is a true equilibrium hydrogen electrode. A consideration of the electrocapillary properties of pure palladium and the α-palladium alloys in solution provides an explanation of the cessation of spontaneous absorption of hydrogen before complete equilibrium is attained.
Chemical Determination of the Oscillator Strength of F Centers
Authors: Scott Allen B. , Hills Marian E.
Published: January 2005

The concentration of F centers in additively colored KCl was determined by measuring the amount of hydrogen evolved when the colored crystal is dissolved in water. This method avoids the uncertainties inherent in previous experiments on the change in acidity occurring upon dissolution. The use of this concentration in the Smakula absorption equation gives the optical oscillator strength f. The value of f, based upon 12 independent experiments, was 1.17±0.15, which disagrees with previously reported values.
Discussion of Slater Parameters for Elements of the First Long Period
Authors: Brown David A.
Published: January 2005

Slater-Condon parameters are calculated for elements of the first long period in terms of Slater functions. By comparison with the observed spectroscopic data it is found that the Slater rules predict reasonable values for the exponents of these functions, with certain important qualifications regarding the variation of the screening number with configuration. The exchange integral between the 3d and 4s functions is less satisfactory. By means of the derived results the reduction of Slater-Condon parameters within complexes is attributed in part to a polarization of the 3d functions so as to achieve near equality of Slater exponents with those of the ligands.
Millimeter-Wave Spectrum of Formic Acid
Authors: Erlandsson Gunnar
Published: January 2005

The investigation of the Ra branch of the formic acid rotational spectrum has been extended up to J = 9 around 1.5 mm wavelength. The centrifugal distortion corrections have been studied in some detail partly by means of sum rules and partly by power series expansions and other approximate methods.
Statistics of Polymer Molecular Size Distribution for an Invariant Number of Propagating Chains
Authors: Gold Louis
Published: January 2005

A detailed study of the polymer statistics for a reaction system resembling the ethylene oxide initiator case is made allowing for different rates of initiation ki and propagation kp. The modified Poisson distribution that results necessitates evaluation of rather complicated summations in order to characterize the number x̄n and weight average x̄w molecular weights. It is found that r = kp/ki as large as 106 still does not shift (x̄w/x̄n)max beyond the range 1.3 to 1.4. But under any circumstance, depletion of monomer assures homogeneous polymers, regardless of r.
Pure Quadrupole Resonance Determinations of Molecular Charge Distributions. I. Substituted Quinones, Quinolines, Pyridines, Pyrimidines, and Triazines
Authors: Bray P. J. , Moskowitz Saul , Hooper H. O. , Barnes R. G. , Segel S. L.
Published: January 2005

The charge distributions in quinone and several heterocyclics containing nitrogen in the ring have been determined from the pure quadrupole resonance frequencies of attached halogens. Agreement with values from molecular orbital calculations is good in quinone and pyridine but poor in quinoline.

Quantitative measurements are presented for the effect of ring nitrogens on the double bond character of carbon-halogen bonds.
Energy of Interaction between Two Excited Hydrogen Atoms in either 2s or 2p States
Authors: Linder Bruno , Hirschfelder Joseph O.
Published: January 2005

A complete set of potential energy curves arising from the interaction between two excited hydrogen atoms in either 2s or 2p states is given for intermediate and large internuclear separations. These include first- and second-order perturbation energies. The first-order perturbation energies are obtained by using exact integrals and properly symmetrized wave functions with an effective nuclear charge of unity. The possibility of occurrence of ionic states, which become important at small internuclear separations, is ignored. The first-order energies are essentially Coulombic in the long-range region and can be described in terms of simple electrostatic dipole-dipole, dipole-quadrupole and quadrupole-quadrupole interactions. Approximate values of the second-order perturbation energies are obtained by using nonsymmetrized wave functions and omitting in the expansion of the perturbation potential all terms beyond the leading one. For most states, the second-order perturbation energies are small compared to the first-order energies throughout the long-range region.
Separation of Boron Isotopes. II. The BF3 Anisole System
Authors: Palko A. A. , Healy R. M. , Landau L.
Published: January 2005

A new gas-liquid countercurrent system has been developed for the separation of boron isotopes. This system utilizes the exchange reaction between BF3 gas and the BF3·methyl phenyl ether (anisole) complex. Quantitative dissociation of the complex is attained by heating, and recombination by cooling. Half-time for the isotopic exchange has been shown to be less than three seconds. The single-stage separation factor [B10F3·anisole (liq.)/B11F3·anisole (liq.)/B10F3 (gas)/B11F3 (gas)]varies from 1.039 at 0°C to 1.028 at 30°C. Physical properties of the complex have been determined and solvent decomposition has been studied.
Influence of the Crystal-Field Potential on Interionic Separation in Salts of Divalent Iron-Group Ions
Authors: Hush N. S. , Pryce M. H. L.
Published: January 2005

The crystal energies of ionic lattices containing iron group ions with nonspherically symmetric electronic ground states are appreciably lowered as a result of crystal field splitting of the lowest energy levels. This gives rise to a characteristic periodic variation of the equilibrium cation-anion separation as the 3d shell is progressively filled. It is possible to estimate the contractions of interionic separation resulting from the crystal field effect by comparison with the distances in lattices containing only ions with S ground states. In the divalent oxides and halides, these contractions are of the order of 0.04–0.22 A. By treating the crystal-field stabilization as a small perturbation, the contractions can be calculated for simple lattice structures. Good agreement between theory and experiment is found for oxides crystallizing in the sodium chloride lattice, with the exception of VO. The lattice contractions of D3d3 iodides and D4h14 fluorides can also be consistently correlated with stabilization energy in these salts.
Exchange of Radiocobalt between the Hexammines of Cobalt(II) and Cobalt(III) in Liquid Ammonia
Authors: Grossman Jack J. , Garner Clifford S.
Published: January 2005

Exchange of radiocobalt between Co(NH3)6+2 and Co(NH3)6+3 nitrates in liquid ammonia has been studied at 25° and 45°C. Reactants were separated by distilling off the solvent ammonia and extracting the Co(II) as the thiocyanate complex into a mixture of ether and isoamyl alcohol. Runs were not accurately reproducible, probably because of catalytic effects from traces of oxygen in the system. Rate constants, calculated for an assumed bimolecular rate law, are 6×10—5 and 7×10—4 l·mole—1·sec—1 at 25° and 45°C, respectively. The rate in liquid ammonia is compared with published rates in aqueous ammonia solution and with the rate of exchange of labeled NH3 between solvent liquid ammonia and ligand ammonia in Co(NH3)6+3.
Exchange Broadening in Nuclear Magnetic Resonance
Authors: Kaplan Jerome
Published: January 2005

A general theory of the nonsaturated NMR spectra of chemically exchanging molecules is formulated. As an example the case of a molecule with two nonequivalent protons exchanging with a molecule with one proton is worked out in detail. Connection is made with previous theories by taking limiting expressions of the general results. In the appendix it is shown how the method can be extended to include saturation and hindered rotation.
Drude-Model Calculation of Dispersion Forces. III. The Fourth-Order Contribution
Authors: Bade W. L.
Published: January 2005

The results of part I are applied in calculating the fourth-order dipole-dipole contribution to the dispersion interaction energy of a system containing N identical spherical molecules. This contribution to the energy consists of pair terms proportional to Rij-12, triplet terms proportional to (RijRjk)-6, and quadruplet terms proportional to (RijRjkRklRli)-3, where Rij is the separation of the ith and jth molecules. The expression for the fourth-order energy is summed approximately over the face-centered-cubic lattice. The result is E(4) ≃—100NV(α/R03)4, where α is the polarizability and V the characteristic dispersion energy of the molecules, R0 is the nearest-neighbor distance in the lattice, and N is the number of molecules in the crystal. The triplet terms are responsible for the main contribution to this sum. The fourth-order dipole-dipole dispersion energy of the lattice is negative and comparable in magnitude with the positive triple-dipole energy computed by Axilrod and others, in cases where the latter contribution is substantial.
Diffusion of Cobalt and Chromium in Chromite Spinel
Authors: Sun R.
Published: January 2005

The diffusion of cobalt and chromium in sintered samples of CoCr2O4 has been measured in the temperature region 1400°C—1600°C where it is believed that bulk diffusion predominates. The diffusion can be represented as DCo=(10—3) exp(—51 000/RT), DCr=(2) exp(—70 000/RT).
Kinetics of Gas Phase Halogenation Reactions
Authors: Benson Sidney W. , Buss Jerry H.
Published: January 2005

Making use of the independently measured rate constants for the reactions X+X+M⇌X2+M (where X=Br, I, etc.) it is possible to calculate the times needed to approach the stationary state for X atoms. On applying these results to the kinetic studies which have been made of halogenation reactions, it is found that for most thermal brominations, the times are in excess of 100 seconds. For thermal chlorinations, the times are in excess of 1000 seconds while for more strongly bonded diatomic molecules they are still higher. In photochemical systems the times are of the order of 0.1 to 1.0 second for absorbed intensities of 1012 quanta/cc sec which are quite usual. The implications of these values for many of the systems studied, are that heterogeneous initiation and termination of chains are contributing significantly to the kinetics of thermal halogenations at temperatures below 500°C.

An examination of the brominations of isobutane, toluene, and neopentane shows that the mechanisms proposed in each case may be suspect and that heterogeneities are of likely importance and may account for the anomalous rate constants reported for these systems.

Methods are employed for estimating to ±2 cal/mole °K the entropies of free radicals and molecules. The entropy of t-butyl bromide is estimated to be 86.6 eu at 400°K while neopentyl bromide is 105.3 eu at 470°K. These entropy estimates make possible an examination of the self-consistency of the rate data with the proposed rate laws. It is shown that for the systems mentioned above, the data lead to the conclusion that other termination processes must be important, in contradiction to the empirically observed rate laws.

Finally, arguments are presented to show that bimolecular Arrhenius frequency factors should be less than collision frequencies.
Far Ultraviolet Absorption Spectra of Small Ring Hydrocarbons
Authors: Loeffler Barbara B. , Eberlin Elspeth , Pickett Lucy W.
Published: January 2005

Molar extinction coefficients for the far ultraviolet absorption of cyclobutene, 1-methylcyclobutene, and methylenecyclobutane were measured between 40 000 cm—1 and 64 000 cm—1. These spectra show the characteristic absorption of π electrons with oscillator strengths of 0.3 and with band positions which are explicable on the basis of molecular structure. Photodecomposition to give ethylene was observed in the case of methylenecyclobutane and 1-methylcyclobutene.
Theoretical Derivation of Traube's Rule
Authors: Aranow Ruth H. , Witten Louis
Published: January 2005

A theoretical derivation of Traube's rule for the surface tension of dilute aqueous solutions of homologous series of long chain compounds is given. It is demonstrated that a quantitative interpretation of the rule requires that the molecules of the chain extend randomly upward out of the surface and permit hindered rotations of the CH2 groups about each carbon-carbon bond. It is shown that the old arguments for supposing that the molecules of the chain lie parallel to the surface for dilute solutions are unconvincing.
Absorption Spectra of Molten Salts
Authors: Sundheim Benson R. , Greenberg Jacob
Published: January 2005

The ultraviolet absorption spectra of a variety of molten salts have been determined. Generalizations about the character of such spectra are made and certain implications about the structure of the liquids are examined.
Gaseous Species in the Vaporization of Sodium Hydroxide
Authors: Schoonmaker Richard C. , Porter Richard F.
Published: January 2005

Mass spectrometric studies of the gaseous species in sodium hydroxide vapor have shown that in the temperature range 300°C to 450°C, NaOH (1) vaporizes mainly as gaseous dimers. A thermodynamic treatment of ion current data yields for the reactions: 2NaOH(l)=Na2(OH)2(g)ΔH660∘K0=28±3 kcal/mole of dimerNaOH(s)=NaOH(g)ΔH298∘K0=46.4±3 kcal/mole of NaOH2NaOH(g)=Na2(OH)2(g)ΔH660∘K0=−54±5 kcal/mole of dimer.Comparison with existing data on the gaseous alkali halides shows the trend in dimerization energies: NaOH(g)>NaCl(g)>NaF(g).
Light Scattering and Statistical Shape of Streaming Freely Flexible Linear Macromolecules
Authors: Peterlin Anton , Heller Wilfried , Nakagaki Masayuki
Published: January 2005

The angular distribution of the light scattered from an unpolarized beam by a solution of random coils subjected to shear is calculated. The molecular model considered is a freely draining coil and the light scattering is treated according to Debye. The theory shows that the probability distribution of the segments at finite shear has the symmetry of an ellipsoid whose axial ratio increases with shear. The results derived should allow one to determine the mean square end-to-end distance, its variation with the shear applied and, therefore, the statistical shape of flexible macromolecules and its change by flow.
Quantum Mechanics of the H3 Complex
Authors: Kimball George E. , Trulio John G.
Published: January 2005

A minimum energy and the associated nuclear configuration are given for linear symmetric H3 in the ground (2∑u+) state. An LCAO MO wave function with complete configuration interaction, is constructed from a set of five 1S hydrogen-like orbitals with centers equally spaced on the line of nuclei. Apart from symmetry, nuclear positions and orbital centers are unrelated but the screening constant is the same for each orbital. The nonlinear parameters which were varied are the screening constant, internuclear distance, and the distance between adjacent orbital centers. An energy of —72.4±0.5 kcal/mole (relative to three separated H-atoms) is obtained; the experimental value2 is ∼—103 kcal/mole.

Many difficult 3- and 4-center repulsion integrals were evaluated numerically, using the CPC at Watson Scientific Computing Laboratory. The chief advantage of this model is that all the difficult integrals belong to one family characterized by essentially three parameters. Thus, all of them were computed from a single numerical program.
Unlike Molecular Interactions and Properties of Gas Mixtures
Authors: Srivastava K. P.
Published: January 2005

Recently we have developed a set of semiempirical combination rules which may be utilized to calculate the intermolecular potentials for unlike pairs of molecules from the known potentials for like pairs on the modified Buckingham exp—six model. It is, therefore, necessary to see how far these combination rules can reproduce the transport properties of binary gaseous mixtures over large ranges of temperature and concentration. With this end in view various transport properties such as themal diffusion, interdiffusion, thermal conductivity, and viscosity have been calculated for a large number of binary mixtures and the computed values compared with the experimental data. It is found that the agreement between the theory and experiment is quite satisfactory. It is concluded that this set of combination rules can be used with success to predict the transport properties of gaseous mixtures within the limits of experimental error.
Transitions in Adsorbed Monolayers. III. Results and Comparisons
Authors: Fisher B. B. , McMillan W. G.
Published: January 2005

The experimental and theoretical results of the two preceding papers [B. B. Fisher and W. G. McMillan, J. Chem. Phys. 28, 549 and 555 (1958), hereafter referred to as Parts I and II] are combined to yield ``experimental'' values of the adsorption parameters for nitrogen, krypton, and methane on sodium bromide. These are compared with the results of extensive theoretical calculations of the adsorption energy χ, the lateral interaction energy w and the frequencies of various vibrational modes. Of the several parameters, the agreement between theory and experiment is best for χ; of the several gases, the agreement is best for krypton. An appendix gives fitted functions for inverse sixth power lattice sums, and for the electric field strength above the 100 surface of an fcc ionic lattice.
Bulk Viscosity and Shear Viscosity in Fluids According to the Theory of Irreversible Processes
Authors: Herzfeld Karl F.
Published: January 2005

M. Green has connected the shear and bulk viscosities with the fluctuations of the virial. It is shown here that the virial theorem is correct at every moment, including the fluctuations, if the integral of the pressure over the volume is taken. For monoatomic fluids the bulk viscosity is calculated after introducing an unknown correlation length; for fluids with internal degrees of freedom or with two-state structure, the usual equations follow very easily. For the shear viscosity one finds a formula similar to that of Eyring by making some assumptions about correlations.
Isotope Effect and Structure of the B2O3 and B4O6 Molecules
Authors: Taylor William J.
Published: January 2005

A systematic application of the Teller-Redlich product rule to the isotope effect has been carried out for several of the most likely structures of the B2O3 molecule, and tetrahedral B4O6. It is pointed out that an isotope effect of the magnitude reported by Dows and Porter in the infrared emission (2013 and 2114 cm—1 for B211O3 and B210O3, respectively) is incompatible with the bipyramidal (D3h) model they consider, as well as with the linear (D∞h) structure. Less symmetrical structures of B2O3 (C2, C2v, and C3v symmetries) are not excluded; neither is the tetrahedral B4O6 structure. These conclusions are reached by using in conjunction with the product rule the theorem that the frequency of each and every vibrational mode of a molecule is a monotonic function of each atomic mass. This makes it possible to set bounds on the isotope effect of individual modes of each symmetry type, and this procedure should be generally useful. A proof of the theorem stated is given in the Appendix.
Theory of Potentials of Average Force and Radial Distribution Functions in Ionic Solutions
Authors: Meeron Emmanuel
Published: January 2005

The procedure employed by Mayer for the calculation of osmotic pressure and activity coefficients of ions in solution from the Fuchs expansion of the grand potential in multicomponent systems is applied to the recently obtained expansion of the potential of average force in these systems. The resulting multiply infinite series are summed to give a series analogous to the original expansion, involving the Debye-Hückel potential of average force in a remarkably simple way. A similar expansion for the radial distribution function is presented. Explicit expressions for both quantities, exact through terms of first order in the ionic concentration, are given. An expansion for the osmotic pressure, analogous to the virial expansion, is presented. The presence of the Debye-Hückel potential of average force in all these expansions is discussed, and the possibility of obtaining the potential of average force exact through terms of second order in the ionic charging parameters is indicated. Possible applications to ionic conductivity, diffusion, and viscosity are discussed. Additional applications to the theory of defects in ionic crystals, impurity conduction in semiconductors, etc., are suggested. The significance of the individual terms in the new expansions is discussed. Proof of an n-fold convolution theorem for Fourier transforms is presented.
Statistical Thermodynamics of Quantum Fluids
Authors: Mazo R. M. , Kirkwood J. G.
Published: January 2005

An approximate technique for determining the thermodynamic properties of quantum fluids by the method of molecular distribution functions is developed. It consists of a separation of the problem into two parts, the determination of the classical pair distribution function at an effective temperature τ, and the quantum-mechanical calculation of τ. It is further shown that all thermodynamic quantities of interest can be easily computed if τ is known.
On the Linear Phenomenological Equations
Authors: Bearman Richard J.
Published: January 2005

The transport processes of diffusion and heat flow in a nonreacting, nonelectrolyte fluid system are discussed in terms of the linear phenomenological equations without benefit of the Onsager reciprocal relations. The independent variables which determine the flow pattern, the operational significance of the phenomenological coefficients, and the inversion of the phenomenological equations are each considered.
Thermionic Emission of Thoriated Tungsten
Authors: Schneider Petr
Published: January 2005

Methods were developed for quantitative chemical analysis of those constituents of thoriated tungsten filaments, both uncarbonized and carbonized, which are significant for thermionic emission. Sensitivity was adequate for analysis of an individual filament; therefore the composition of each filament could be correlated with both its thermionic performance and the method of preparation. These correlations are given and the chemical constitution for favorable thermionic results is stated.
Determination of the Faradaic Impedance at Solid Electrodes and the Electrodeposition of Copper
Authors: Bockris J. O'M. , Conway B. E.
Published: January 2005

The techniques of pre-electrolytic purification of the solution and the maintenance of electrodes in glass sheaths until after immersion in the purified electrolytic solution have been applied for the determination of the properties of the ac impedance at the copper-solution interface. Measurements of double layer capacity and resistance at copper interfaces in H2SO4 and in CuSO4 solution over a considerable potential range have been made at frequencies from 10 to 2000 cps.

Significant results can only be obtained with careful elimination of screening and unsymmetry effects in the cell, and by the use of spherical electrodes. The double layer impedance varies with frequency in potential regions where trivial causes such as the dissolution of Cu are not effective. The limiting double layer capacity at high frequency is about 70 μf per apparent sq cm of the surface. Pre-electrolytic purification led to an apparent halving of the transfer coefficient and a considerable increase in exchange current density. The experimentally evaluated coefficients ∂Rdi/∂ω—½ (where Rdi is the diffusional resistance) are about double those theoretically evaluated on the assumption that the true area of the electrode is equal to the apparent area. The values of the experimental coefficients ∂Rdi/∂ω—½ and ∂1/ωCdi/∂ω—½ (where Cdi is the diffusional capacitance) agree well. ∂ lni0/∂ lnaCu++=0.75 when i0 is the exchange current density.

The variation of the double layer capacity with frequency is due to dielectric loss in the water molecules in the double layer. Application of the theory of dielectric loss taking into account the distribution of adsorption energies among the water molecules shows that the observed resistance and capacitance of the double layer in certain Hg-solution and Cu-solution systems can be reproduced with the assumption of relaxation times of about 10—8 and 10—7 sec, respectively. The effect is small on Hg, but much larger on solid metals where the heat of adsorption of water is greater than on Hg. The resistance and capacitance of the double layer on solid metals is intrinsically frequency dependent and this fact (and the existence of a significant double layer resistance) must be taken into account in the evaluation of Faradaic impedance. If the intrinsic frequency dependence of the double layer is taken into account, the Faradaic resistance and the diffusional capacitance behave theoretically; if a frequency-independent double layer impedance is utilized, irrational values of the Faradaic impedance and reaction resistance are obtained.

Diffusion occurs to only about one-fifth of the true surface area.
Calculation of the Energy of Activation for Some Simple Reactions. I. Ortho-Para Hydrogen Reaction
Authors: Lippincott E. R. , Leifer Asa
Published: January 2005

A model is proposed from which energies of activation and potential energy surfaces of three atom reactions may be calculated. The method makes use of internuclear attractive and repulsive potential functions which have been derived from a quantum mechanical delta-function model. The energy of activation of the ortho-para hydrogen reaction was calculated and found to have a value of 8.5 kcal in agreement with the experimental value. The model predicts the presence of a slightly stable H3 complex. This complex, however, is asymmetric, located at a minimum in the potential curve just before the barrier, and is stable by an energy of about 1 kcal.

The method may be classified as semiempirical. However, all parameters used are obtained theoretically from the proposed model. One advantage of the method is that the main points of interest on the potential energy surface may be calculated without calculating a complete potential energy surface.
Experimental Determination of the Electron Affinity of Fluorine
Authors: Bailey T. L.
Published: January 2005

Two methods are described for mass spectrometric determination of the electron affinities E(X) of electronegative atoms X. Both methods were used to determine the electron affinity of fluorine, E(F), the best measured value being E(F)=82.1±2.1 kcal/mole. In the first method the ratio of numbers of X- negative ions to M+ positive ions emitted from a hot tungsten filament in MX salt vapor is measured. From this the equilibrium constant for the attachment reaction X+e-=X-, and hence E(X), may be calculated. In the second method, the difference in electron affinities, E(Y)-E(X), is calculated from a measurement of the ratio of numbers of Y- to X- ions emitted from a hot filament surrounded by XmYn gas. Measurements were also made for the other halogens; these gave E(Cl)=86.6±2.0 kcal/mole, E(Br)=80.9±1.5 kcal/mole, and E(I)=73.2±1.7 kcal/mole.
Triplet-Singlet Emission Spectra of Solid Toluene at 4°K and 77°K and in EPA Solution at 77°K
Authors: Kanda Yoshiya , Sponer H.
Published: January 2005

Phosphorescence of toluene has been studied at 4°K and 77°K in its solid phases (crystalline and amorphous) and in solid solution (EPA) at 77°K. The spectrum of the crystal at 4°K (3460-4530 A) consists of sharp bands, and weaker diffuse bands which resemble in arrangement the rigid glass spectrum at 77°K. This emission has a lifetime of about 8 sec. The spectrum of solid toluene at 77°K (3950-4900 A) has broad diffuse bands, and an estimated lifetime of ∼10-2-10-3 sec. Its vibrational structure differs from that of the spectra at 4°K and in EPA, but resembles much the structure of the phosphorescence spectrum of benzaldehyde. The origin of the various spectra and the differences between them are discussed. The suggestion is made that benzaldehyde is produced photochemically and that its spectrum appears by a process of sensitization.
Dependence of Force Constant on Electronegativity, Bond Strength, and Bond Order. VII
Authors: Somayajulu G. R.
Published: January 2005

The expression :kAB=(kAA·kBB)12+Δ where k′S are the force constants of the bonds AA, AB, and BB of given type and Δ, an ionic contribution term, has been suggested. For single bonds, the value for √Δ corresponds to the difference in the electronegativities of the atoms A and B in their valence states. In the case of multiple bonds the value for √Δ leads to proper value for the percentage ionic character of the bond. Force constant has been shown to be proportional to the product of the strengths of the bond orbitals, the magnitude of a bond orbital in its angular dependence being defined as the strength with value 1 for an s orbital and 1.732 for a p orbital. The value for the sp3 orbital has been found to be about 2 but for sp2 and sp orbitals, values differing from those suggested by Pauling have been obtained. Among s—p bonds, digonal bonds have been shown to be the strongest followed by trigonal and tetrahedral bonds. In alkali metals, the bonds have been shown to be s—p bonds with strength 1.732. Force constant has been shown to be linearly related to bond order. Finally, values for the force constants of various covalent bonds have been assigned.
On Covalent Bond Length and Bond Order. VIII
Authors: Somayajulu G. R.
Published: January 2005

Relationships between lengths of CC bonds and of bonds between other atoms have been shown and a method of estimation of fractional bond order from bond length has been presented.
Pyrolysis of Mercury Dimethyl Vapor
Authors: Srinivasan R.
Published: January 2005

A comparison of the published experimental results from three sources on the pyrolysis of mercury dimethyl vapor in a static system at about 615°K indicates that there is disagreement in the rate data although the nature of the decomposition is similar in all cases. Additional data are given to show that this discrepancy is presumably due to surface effects. The nature of the decomposition products is markedly different in the published studies of the pyrolysis in a flow system at about 800°K. In this instance, surface effects appear to be unimportant. It is suggested that the heterogeneous reactions: CH2HgCH3→CH3+product(s)followed by polymerization of the products to (CH2)n+Hg constitute the difference in mechanism between the two systems. The evidence for this proposal is examined. Some minor reactions of the methyl radical in this system are discussed on the basis of entropy changes in these reactions.
Ionization and Dissociation of NO2 and N2O by Electron Impact
Authors: Collin J. , Lossing F. P.
Published: January 2005

A comparison of values of the ionization potential of NO2 derived from direct electron impact, from dissociative ionization of CH3NO2, and from the ultraviolet spectrum of NO2, show large discrepancies. There is reason to believe that three different electronic states are involved. The ionization potential of N2O as measured by electron impact is in good agreement with spectroscopic data. The appearance potential of O+ ion from N2O gives D(NN–O)=39.7 kcal/M, in excellent agreement with the thermochemical value of 39.49 kcal/M.
Some Comments on the Strength of Single Coordinate Bonds
Authors: Fyfe W. S.
Published: January 2005

The strength of simple coordinate bonds has previously been discussed emphasizing the importance of ionization potentials of donor and acceptor species. This treatment neglects an important term in the thermodynamic cycle, the homolytic dissociation energy which in many cases dominates. Some anomalies following neglect of this term have been attributed to multiple bonding and it is considered that the extent of such bonding may have been overestimated.
Phase Changes and Spectral Shifts
Authors: Robertson W. W. , Babb S. E.
Published: January 2005

The absorption spectrum of benzene has been obtained in the diluents carbon dioxide, ethylene, and ethane over a wide range of densities both above and below the critical temperatures. The red spectral shifts are linear functions of the density throughout the density range for ethylene and ethane and are independent of the state of the diluent. A break in the linear wavelength-density curve occurs at high densities of carbon dioxide. These results support the view that gases and liquids are essentially the same thing in those cases where specific interactions are not involved and suggest further that the radial distribution function remains constant from low to high densities of gas and into the liquid state.
Gaseous Detonations. X. Study of Reaction Zones
Authors: Chesick John P. , Kistiakowsky G. B.
Published: January 2005

The resolution time of the apparatus for rapid measurements of gas densities in shock and detonation waves by the absorption of x-rays was evaluated by studies of shock waves and found to be largely determined by the slit width. The rotational relaxation of N2, O2, H2, and CH4 in mixtures with xenon and the vibrational relaxation of O2, H2, and CH4 were too fast for observation. The dissociation rate constants were determined for hydrogen : kD = 2.5 and 4.2×10—16 cc/sec at 2850 (?) and 3250°K and for oxygen : kD = 2.3 and 6.8×10—16 cc/sec at 3100 and 3500°K. The initial (shock front) densities in 2H2+O2+½Xe detonating mixtures were found to be consistent with calculations based on full rotational but no vibrational relaxation, when it was assumed that the rates of exothermic reactions rise to a maximum within less than one μsec and then decrease somewhat faster than in a second order reaction. The pre-exposure of the cold gases to x-rays for a few seconds results in faster initial reaction rates, while a pre-exposure of only a few milliseconds has no measurable effect. No effect of pre-exposure on the rates after about 50% completion of the reaction is evident. These findings indicate a highly branched mechanism of chain carrier generation. The effects of total pressure and gas composition on the duration of the reaction zone were investigated with several mixtures. Substitution of deuterium for hydrogen reduces the rate by about 30%. The retarding effect of water vapor on the rate of the hydrogen-oxygen reaction is not pronounced.
Kinetics of the Triiodide Equilibrium
Authors: Myers Orlo E.
Published: January 2005

The I127 NMR absorption line of iodide ion in aqueous solution is broadened by the presence of iodine molecules. The broadening is consistent with the diminution of phase-memory time caused by strong quadrupole coupling in triiodide ion, which occurs in dynamic equilibrium. On the basis of a simple bimolecular mechanism, the rate constants for the forward and reverse reactions of the triiodide equilibrium at ca 35°C are (4.1±0.4) × 1010 l/mole-sec and (7.6±0.8) × 107 sec—1 in the concentration ranges which have been investigated.
Relative Detection Efficiency of LiBr and (LiBr)2
Authors: Kusch P.
Published: January 2005

The relative efficiency for the production of positive ions when LiBr and (LiBr)2 are incident on a hot oxidized tungsten wire has been determined. It is found that the ratio of the number of ions produced for the molecule (LiBr)2 and the molecule (LiBr) is 2.0±0.1. The result is consistent with the heretofore unverified assumption that has been made in the study of the thermochemistry of the vapors of the alkali halides. Effects arising from the long mean free paths of molecules in ovens used for such studies have been observed and are discussed.
Correlation of Molecular Constants. I. Deduction of Relations
Authors: Varshni Yatendra Pal
Published: January 2005

Making certain assumptions regarding constants in Sutherland's potential energy function, a number of relations have been derived between the molecular constants; viz., ke, re, De, ωe, etc. The relations will be examined in succeeding papers.
Magnetic Properties of Certain Rare Earth Double Nitrates
Authors: Judd B. R. , Wong Eugene
Published: January 2005

Paramagnetic resonance experiments have been performed with crystals of diluted erbium magnesium nitrate and diluted holmium magnesium nitrate. Resonance was observed in the first case but not in the second. These experimental results and in addition the Zeeman effects in neodymium magnesium nitrate are interpeted in terms of a crystalline electric field of predominantly icosahedral symmetry.
Dynamical Stability Criteria for Molecular Motions
Authors: Liehr Andrew D. , Frisch Harry L.
Published: January 2005

The Poincaré classification theory of the singularities of the equations of motion of a classical mechanical system are suitably modified to describe the singularities in the motion of an arbitrary quantum-mechanical system, derivable from a time-independent Hamiltonian. Dynamical quantum-mechanical stability criteria are derived starting with the appropriate equations of motion satisfied by the Heisenberg position and momentum matrices of the system. These stability criteria are used to discuss and classify certain singular nuclear motions of molecular systems which are of some interest in the context of prevalent theories of chemical stability and chemical reaction kinetics. In particular we show that the singular nuclear motions of a molecular system whose electronic and nuclear motions can be assumed to be separable, reduce to the rolling motion of dynamically equivalent classical spheres on the electronic potential energy surface.
Intermolecular Potentials of Argon, Methane, and Ethane
Authors: De Rocco Andrew G. , Halford J. O.
Published: January 2005

The viscosities of argon, methane, and ethane are reported over a temperature range from ∼210°K to ∼475°K. In conjunction with second virial coefficient data, the viscosities have been employed to estimate the potential parameters for an Exp:6 potential. For the spherically symmetric molecules a single set of parameters served to reproduce the equilibrium and transport properties with serviceable accuracy. For ethane the procedure failed, and this failure was taken as further evidence for the fundamental inadequacy of the assumptions of central forces and elastic collisions.
Holes and Cells in Liquids
Authors: Hill Terrell L.
Published: January 2005

A certain amount of exact information about cells and holes in liquids can be deduced from the radial distribution function. For example, for cells small enough so that they cannot contain more than one molecule, we can find the radial distribution function around an occupied cell or around a hole (empty cell), the probability that a cell near a molecule will be occupied, and the probabilities for occupancy or nonoccupancy of pairs of cells near each other. Also, the probability that a cell of arbitrary size will be empty can be calculated. Examples are given using an experimental radial distribution function for liquid argon.
Quadrupole Coupling of Solid Cyanogen Chloride
Authors: Casabella P. A. , Bray P. J.
Published: January 2005

The nuclear quadrupole resonances of N14 and Cl35 have been observed in solid ClCN. In the course of study of the N14 resonances a detailed study was made of the shape of the negative wings which occur when Zeeman modulation and phase sensitive detection are used. The shape of these wings can reveal whether two resonances are due to two nonequivalent positions of the N14 nuclei, or one position with a nonzero asymmetry parameter. A theoretical expression has been derived for the shape of the wings which agrees with the experimental results. The coupling constants of the Cl35 and N14 nuclei have been interpreted in terms of a set of hybrid structures.
High-Temperature Gas Viscosities. I. Nitrous Oxide and Oxygen
Authors: Raw C. J. G. , Ellis C. P.
Published: January 2005

The viscosity of nitrous oxide has been measured in the temperature range of 100 to 1000°C. A specially constructed transpiration apparatus of fused silica was used. Results at the lower temperatures show very close agreement with those of other workers, the viscosity behaving normally up to about 550°C, above which the thermal decomposition of nitrous oxide becomes significantly large. Experimental data on the viscosity of dissociating nitrous oxide at high temperatures up to 1000°C are discussed. Viscosity results for oxygen at temperatures higher than those previously reported (i.e., above 800°C) are also included. The molecular interaction parameters for both nitrous oxide and oxygen have been calculated in the higher temperature ranges.
Kinetics of the High-Temperature Heterogeneous Reaction of Chlorine and Nickel between 1200 and 1700°K
Authors: McKinley John D. , Shuler Kurt E.
Published: January 2005

The kinetics of the reaction of gaseous chlorine with metallic nickel has been investigated in a constant pressure flow system in the temperature range from 1200° to 1700°K, and at chlorine pressures between 0.08 and 0.4 mm Hg. Nickel chloride produced in the over-all reaction, Ni(s)+Cl2(g)→NiCl2(g), is highly volatile at these temperatures, and the reaction thus takes place on the exposed metal surface. The process whereby nickel is removed from the surface is first order in chlorine pressure, very rapid with a collision efficiency between 0.5 and 0.2, and is temperature independent, i.e., Eact<2 kcal. The rate constant for the removal of nickel is found to be 1.85 × 103 cm sec—1, the units corresponding to moles of nickel per cm2of surface per unit density (M/cm3) of chlorine. An experimental technique employing time lapse photography is described which is particularly well suited to the study of the kinetics of high temperature surface reactions with volatile reaction products.
Vibrational Spectrum of Nickel Carbonyl
Authors: Jones Llewellyn H.
Published: January 2005

The infrared absorption spectrum of Ni(CO)4 has been studied in the liquid and gaseous states. As a result of the observations certain frequency assignment changes have been made. The most probable assignment of fundamental frequencies appears to be 2128 and 381 for the A1 species; 461 and 79 for the E species; 2057, 459, 422, and 79 for the F2 species; and 300 cm—1 for the F1 species. Using these values a normal coordinate treatment was carried out. Though the solution is not unique we can report FCO = 17.3±0.4 md/A and FNiC≈2.1 md/A.
Absorption and Dispersion of Sound in Chemically Reacting Fluids
Authors: Mazo R. M.
Published: January 2005

The hydrodynamic equations for a reacting fluid mixture, in the form given by Kirkwood and Crawford, are used to find the dispersion and absorption of plane infinitesimal sound waves. Only the case of no internal relaxations is treated. The equation for the absorption and dispersion is simplified for commonly occurring special cases, and it is shown that the viscothermal and chemical absorptions and dispersions are additive to first order. The effects of diffusion currents are estimated in the appendix and found to be negligible.