bluuebunny/crossref_metadata_2025 huggingface dataset:
The Variation of the Complex Dielectric Constant with Frequency
Authors: Bolton H. C.
Published: January 2005

The locus of the complex dielectric constant for the dispersion region of a polar dielectric is found in the ``complex dielectric constant plane'' following the equation of Onsager (1936), and is compared with the approximate solution of Cole (1938). The curve is plotted for the polar liquids, water, ethyl alcohol, and tertiary butyl alcohol, and compared with the curve deduced from Debye's equation. Calculations are made of the values of the relaxation times. The values of the molecular volume deduced from the Debye expression for the relaxation time are compared with those deduced from the van der Waals b coefficient.
On the Structure of a Catalyst Surface
Authors: Sips Robert
Published: January 2005

A method is described which makes it possible to calculate rigorously the distribution of the adsorption energies of the sites of a catalyst surface when the adsorption isotherms are known, if the adsorption is localized and there are no interactions. This method is applied to a Freundlich isotherm, and also to a new theoretical isotherm which reduces to the Freundlich type for small pressures, but exhibits saturation for large pressures. It is shown that this isotherm corresponds to a distribution function which differs very little from a Gaussian one. The case of atomic adsorption of gases is also considered.
Molecular Orbital Calculations of Vibrational Force Constants. I. Ethylene
Authors: Parr Robert G. , Crawford Bryce L.
Published: January 2005

As a preliminary to the theoretical evaluation of certain out-of-plane vibrational force constants of benzene, the energy levels and twisting frequency of ethylene are calculated by the method of antisymmetric molecular orbitals, no empirical data being used other than molecular dimensions. The problem is oversimplified to a two-electron one, and yet encouraging results are obtained.
The Average Boundaries of Statistical Chains
Authors: Hollingsworth C. A.
Published: January 2005

A general problem of determining what might be called the ``average boundaries'' of statistical chains is solved formally. As a specific example, the average distance between the first link and the link (or links) which is farthest from the first link is calculated approximately for the case of a random chain. This value is only a small fraction greater than the average distance between the end links.
Approximate Configurational Partition Functions for Certain Aggregates of Spherical Molecules
Authors: Morales Manuel F. , Botts Jean
Published: January 2005

There are calculated by two different methods the number of ways in which i sites out of a total of n sites may be filled in such a manner that among the filled sites there will be p nearest neighbor pairs when the sites form certain regular spherical surface lattices: the contact points on any sphere in the cubic and hexagonal closest packings of spheres, and in the simple cubic packing of spheres. The use of these results in the treatment of a model of antibody-antigen combination is briefly indicated.
Heats of Dissociation of Cyanogen
Authors: Glockler G.
Published: January 2005

Some arguments are presented which would indicate that the heat of dissociation of C2N2 into two CN radicals (D(C2N2 into 2CN)) is 5.52 ev and the heat of dissociation of CN radicals into atoms (D(CN)) is 6.52 ev.
Vibrational Frequency Assignments for Paraffin Hydrocarbons; Infra-Red Absorption Spectra of the Butanes and Pentanes
Authors: Rasmussen R. S.
Published: January 2005

The infra-red absorption spectra from 2 to 15μ are given for n-butane, isobutane, n-pentane, isopentane, and neopentane. Vibrational assignments for these molecules and for propane are deduced. The band positions correlatable with particular types of vibration of various hydrocarbon groupings are discussed.
Symmetry Matrices in Normal Coordinate Analysis
Authors: Kilpatrick John E.
Published: January 2005

A general symmetry matrix, Un, has been derived which may be used to combine n equivalent coordinates in a molecule having the symmetry of any cyclic or dihedral point group of multiplicity n. The direct products U2 × Un and U2 × U2 × Un may be used in the cases of 2n and 4n equivalent coordinates. The symmetry type of each row of the symmetry matrices used has been determined.
The Energy Levels and Thermodynamic Functions of the Fourth Power Oscillator
Authors: Kilpatrick John E. , Kilpatrick Myra Ferguson
Published: January 2005

The first six characteristic numbers of the reduced wave equation ψ″+(λ—ξ4)ψ=0 have been calculated by a method of numerical integration. These values have been compared with the corresponding values obtained from the first, second, and third Wentzel-Kramers-Brillouin approximations. For the fourth, fifth, and sixth characteristic numbers, the third W.K.B. approximation is correct within 0.0001. The four thermodynamic functions—(F—H0)/RT, (H—H0)/RT, S/R, and C/R have been calculated over the range hν0/kT=0 to 10. A previously reported maximum in the heat capacity function, C/R, does not exist.
Photo-Chemical Studies. XL. The Mechanism of the Photo-Chemical Decomposition of Acetone
Authors: Noyes W. Albert , Dorfman Leon M.
Published: January 2005

The data now available indicate quite strongly that the photo-chemical decomposition of acetone proceeds mainly if not entirely by a free radical mechanism. The various steps are reviewed and the evidence for them given. At high pressures where wall effects may be neglected certain definite conclusions are possible. In the region where some reactions are both homogeneous and heterogeneous the proof for all steps is not available and would be difficult to obtain. The analyses for some of the known products are not satisfactory for the small amounts formed. Nevertheless, it is believed that the steps proposed are adequately substantiated, and that the difficulties of obtaining further information are so great as probably not to warrant more effort along certain lines.
The Vapor Pressure and Heat of Sublimation of Graphite
Authors: Brewer Leo , Gilles Paul W. , Jenkins Francis A.
Published: January 2005

The heat of sublimation of graphite and the heats of dissociation of CO and C2, which have been the subject of much controversy in recent years, have been unambiguously established by the direct determination of the total vapor pressure of graphite by an equilibrium effusion method and by the determination of the partial pressure of C2(gas) in equilibrium with graphite.

The heat of sublimation of graphite to C(g) is found to be ΔH0=170.39±0.20 kilocalories per mole at 0°K. The heat of sublimation of graphite to C2(g) is found to be ΔH0=233.1±7 kilocalories per mole. The heats of dissociation of C2 and CO have been shown to be 4.7±0.3 and 11.109±0.01 electron volts, respectively. The accommodation coefficient of carbon gas on graphite at high temperatures is found to be about 0.3 and vaporized carbon gas is shown to be in the 3P ground electronic state.
On the Photo-Chemistry of Some Ions in Solution
Authors: Farkas L. , Klein F. S.
Published: January 2005

The absorption spectra of chlorate, bromate, iodate, and hypobromite ions and of hypobromous acid were measured.

The decomposition of bromate ion was investigated in the light of a mercury arc in the spectral region: 1900A to 2600A. The quantum yield of the decomposition is 0.19. The main decomposition reaction leads to the formation of hypobromite and molecular oxygen. The irradiation of hypobromite ions leads to the formation of bromide and bromate ions in a ratio of about 4 to 1 and to the evolution of oxygen. The decomposition of chlorate ion and iodate ion is analogous to that of bromate. It is assumed that in all these cases the primary process of light absorption consists of the transfer of an electron to the hydration layer. In the case of halate ions, the photo-chemical reaction can be formulated as a decomposition of the complex (XO3−·H2O) to XO−+H2O+O2; in the case of the hypobromite, as the decomposition of (XO−·H2O) to X−+H2O+O. In the latter case the oxygen atoms formed are responsible for the formation of bromate.
Countercurrent Gaseous Exchange Method for the Separation of Isotopes
Authors: Bernstein R. B. , Taylor T. I.
Published: January 2005

A method is described for isotope enrichment by countercurrent gaseous exchange in a thermal diffusion column. The theory is derived for two cases of interest: diffusion limited and reaction-rate limited. Solutions of the equations are presented for the over-all separation S at the steady state as a function of the following: single stage enrichment factor α; diffusion constant D or exchange rate constant k; length of column Z; and the convective flow L, which in turn depends on pressure, temperature, column dimensions, etc. The results may be expressed in the usual form S=αN. For the diffusion-limited case N=4πDc̄Z/L, where c̄=moles of gas per cc. For the reaction-rate limited case the number of theoretical plates per unit length is given by the expression N/Z=k/v, where v is the convective velocity.

Experiments are described in which C13 was concentrated by the exchange reaction C12O2+C13O⇌C13O2+C12O. The observed dependence of the over-all separation upon the operational variables is consistent with the theory.
Polarized Crystal Spectra of Optically Active Ions. I. trans-[Co(1-pn)2Cl2]+ and trans-[Coen2Cl2]+
Authors: Dingle R.
Published: January 2005

Polarized crystal spectra are reported for the trans-[Coen2Cl2]+ ion and the trans-[Co(1-pn2Cl2]+ ion in various crystals at temperatures down to 25°K. The spectra are analyzed in terms of several vibronic intensity gaining models. The optical activity of the latter compound has been used to establish the most appropriate analysis for that spectrum and this is then used in order to discuss the circular dichroism of that ion.
Temperature Dependence of the Rate of Termolecular Atomic Recombinations
Authors: Kim Shoon Kyung
Published: January 2005

The rate coefficient for the gas-phase recombination of atoms or free radicals in the presence of third-body molecules is calculated, based upon the radical—molecule complex mechanism. The rate coefficient, kr, is given by kr=Az24/3F2[1,1;(7/4),(9/4);z], z=εL/kT, where A is a constant factor depending on the molecular constants, εL is the energy depth of the Lennard-Jones (12–6) potential between the reactive atom and the third body, k is the Boltzmann constant, T is the absolute temperature, and 2F2(z) is a generalized hypergeometric function. The experimental temperature dependence of iodine atom recombination in the presence of argon atoms is accurately described by the theoretical expression with εL/k=700, A = 5.4×108 liters2 mole−2·sec−1.
Activation Energy for the Three-Body Reaction of Helium Triplet Atom with Normal Helium
Authors: Ludlum Kenneth H. , Larson Lewis P. , Caffrey James M.
Published: January 2005

From experimental determinations of the rate constants for the reaction He(3S1)+2 He→He2(3Σu)+He, an activation energy, Ea=0.067 eV, was calculated. At 77°K, no contribution from this reaction was found in the afterglow of a pulsed discharge in helium; rather at 77°K the decay was found to be second order with a reaction constant about 2×10−9 cm3 atom−1·sec−1.
Derivation of Molecular Relaxation Parameters of an Isomeric Relaxation
Authors: Singh R. P. , Darbari G. S. , Verma G. S.
Published: January 2005

The expressions for molecular parameters ΔH° and ΔG° are obtained in the presence of volume changes ΔV/V between the isomeric states and the results are used in investigating the influence of the volume changes on the molecular parameters ΔH°, ΔG°, and ΔS°. The present calculations show that for those liquids for which Cp/αRT is large, the molecular parameters are influenced considerably by the volume changes.
Low-Lying Valence Levels of BN and C2. The Ground State of BN
Authors: Verhaegen G. , Richards W. G. , Moser C. M.
Published: January 2005

Some low-lying valence levels of BN and C2 are calculated by the LCAO MO SCF method. Variational calculations are performed on three different configurations for BN and two for C2. Term values are obtained from the minima of the computed potential curves together with estimates of pair correlation energy differences between the various configurations. The results obtained for C2 are in reasonably good agreement (error∼0.2 eV) with experiment. For BN the calculations indicate a 3Π ground state with low-lying 3Σ+, 1Σ+, and 1Π states.
Production and Reaction of Atomic Fluorine in Solids. Vibrational and Electronic Spectra of the Free Radical HNF
Authors: Jacox Marilyn E. , Milligan Dolphus E.
Published: January 2005

The species H14NF, H15NF, and D14NF have been produced in an argon matrix at 14°K by the reaction of photolytically produced atomic fluorine with NH. Sufficient concentrations of these species have been obtained for direct detection of two vibrational fundamentals, appearing at 1000 and 1432 cm−1 for H14NF, as well as of an electronic transition between 3900 and 5000 Å involving a progression in the upper-state bending frequency. Force constants and thermodynamic properties have been derived for HNF. Other species observed in these experiments include NF, NF2, and HNF2. Evidence is presented indicating that the hydrogen atom can be abstracted from HN3 by atomic fluorine.
Growth of Potassium Chloride Crystals from Aqueous Solutions. II. Growth in a Gamma-Radiation Field
Authors: Botsaris G. D. , Mason E. A. , Reid R. C.
Published: January 2005

Seed KCl crystals were grown from aqueous solution under conditions of constant temperature, supersaturation, and impurity Pb+ + level. Experiments were carried out both in-and-outside a gamma-irradiation field. The dislocation densities and absolute-growth rates of the (100) faces of the KCl crystals were measured.

With solutions containing about 10−7 moles PbCl2/mole KCl, irradiation had no measurable effect on dislocation density. At lower lead concentrations, irradiation reduced the number of dislocations and a dislocation climb process is suggested to explain the results.

The effect of irradiation on growth rates of KCl was insignificant when the Pb+ + concentrations were 10−8 and 10−6 moles/mole of KCl. At intermediate concentrations (around 10−7 moles Pb+ +/mole KCl), the effect of irradiation was such as to decrease the growth rate. A possible mechanism is suggested to explain these somewhat anomalous results.
Herschel Effect in Single Crystals of Silver Bromide
Authors: Saunders V. I. , Tyler R. W. , West W.
Published: January 2005

Observations on single crystals of AgBr exposed to long-wavelength visible or near-infrared radiation in the presence of applied electric fields show that the Herschel bleaching of latent-image centers at room temperature is caused by destruction of silver centers by photoemission of electrons. Silver can be regenerated at other sites by recombination of the liberated electrons with silver ions. Brominated crystals of AgBr exhibit an action spectrum for the production of mobile positive holes, unaccompanied by mobile electrons, extending from the edge of the intrinsic absorption band to about wavelength 630 mμ, attributed to photoliberation of deeply trapped holes.
Restricted Rotation in Solid Deuteromethanes
Authors: Hopkins Harry P. , Kasper Jerome V. V. , Pitzer Kenneth S.
Published: January 2005

The theory of Nagamiya for restricted rotation in solid methane is extended to all of the partially deuterated species and applied to the experimental heat-capacity data of Colwell, Gill, and Morrison, which show anomalously high values in the range below 4°K. Agreement with these data is obtained for reasonable values of the energy parameters; also the total entropy of each anomaly is predicted.
Methyl Radical in Irradiated Single Crystals of Sodium Acetate Trihydrate
Authors: Rogers Max T. , Kispert L. D.
Published: January 2005

The ESR spectra of irradiated single crystals of sodium acetate trihydrate and three isotopically substituted species have been examined at 77°K. The hyperfine proton and 13C splittings provide strong evidence for the presence of trapped methyl radicals and the anisotropic hyperfine splitting tensors have been evaluated and are discussed. The planar methyl radical is reorienting rapidly about its threefold axis.
Infrared-Emission Studies of Electronic-to-Vibrational Energy Transfer. III. Hg* + NO
Authors: Karl G. , Kruus P. , Polanyi J. C. , Smith I. W. M.
Published: January 2005

Electronic-to-vibrational transfer has been observed in the system Hg*(63P1,0)+NO. Both Hg*(63P1) and Hg*(63P0) have been found to be effective in bringing this about. A set of rate constants, kv (or cross sections σv2) for electronic-to-vibrational transfer were derived according to various models from an observed set of steady-state concentrations, Nv. The set of kv bear a qualitative resemblance to those for Hg*+CO (Part II). Hg*+NO exhibits a significant but slowly diminishing probability for vibrational excitation into vibrational levels up to v=16 or 17, and an insignificant probability for vibrational excitation into higher levels than v=16–17, corresponding to ⅔ of the electronic energy converted into vibration. The qualitative similarity of these results to those obtained for Hg*+CO suggests that a similar mechanism may be applicable here: Hg*+NO→HgNO*→HgNO→Hg+NO†. However, there exists in the present system an alternative mechanism which would involve electronic-to-electronic transfer: Hg*+NO(X 2Π)→Hg+NO*(4Π), followed by formation of NO† in the ground X 2Π state by collisional deactivation of NO*(4Π).

The total cross section for electronic-to-vibrational transfer with Hg*(63P1) as the donor was estimated to be (σvib2)1=1–15 Å2, and that with Hg*0 as donor (σvib2)0=0.05–1.0 Å2.
Paramagnetic Susceptibilities and Temperature-Dependent Excitation Energies in Linear Organic Crystals
Authors: Soos Zoltán G. , Hughes Robert C.
Published: January 2005

The pseudospin solutions of the regular and the alternating Heisenberg antiferromagnet are shown to explain quantitatively the temperature dependence of the absolute paramagnetic susceptibilities of organic molecular crystals containing linear arrays of free radicals. The pseudospin solutions also reproduce, for a rigid lattice, the temperature dependence of the singlet—triplet energy gap in triplet exciton crystals. This effect, previously interpreted as evidence for exciton—phonon interactions, is again shown to be a many-body effect, which is found even in the absence of exciton—phonon coupling. Information about the structures of these organic crystals is obtained. It is shown that triethylammonium—(TCNQ)2 corresponds to a weakly alternating Heisenberg antiferromagnet rather than, as previously suggested, to a very strongly alternating antiferromagnet. The results for the absolute paramagnetic susceptibility of Wurster's blue perchlorate confirm the previously proposed dimerization below its phase transition at ∼190°K.
Determination of Molecular Quadrupole Moments from Viscosities and Second Virial Coefficients
Authors: Spurling T. H. , Mason E. A.
Published: January 2005

Gas viscosity data for nine quadrupolar molecules are analyzed using calculated collision integrals for the 12–6−5 potential. The parameters of the spherical component of the potential are obtained from the viscosity data, and then used in conjunction with second virial coefficient data to determine the quadrupole moments and ``shape'' parameters of the molecules. The quadrupole moments obtained are very reasonable, and further improvement along these lines will probably depend on a better understanding of the nonspherical components of the repulsive part of the potential.
Electronic Structure and Ground State of Scandium Monofluoride
Authors: Carlson K. Douglas , Moser Carl
Published: January 2005

Recent experiments have shown that the electronic ground state of ScF is 1Σ+, contrary to the 3Δr ground state known for the isoelectronic TiO molecule. Previous theoretical calculations have shown that the 1Σ+ state of TiO lies above 3Δr, in agreement with experiment. Truncated matrix Hartree—Fock wavefunctions for ScF have been calculated here to study the apparent ground-state term inversion of the 1Σ+ and 3Δr levels of this molecule. The ab initio calculations are based on the LCAO expansion method of Roothaan and employ an extended basis that contains the essential functions necessary to represent uncorrelated ground states reliably when there are close-lying valence states. The basis is larger than those used in previous calculations on related monoxides to ensure that the computed ground state and qualitative ordering of ther low-lying states are stationary to further improvements in the basis. For reference purposes, similar extended calculations have been carried out on the TiO molecule. It is found that 3Δr of configuration δσ is the symmetry restricted Hartree—Fock ground state of both ScF and TiO. A semiempirical estimate of the correlation energy contributions shows that correlation depresses the 1Σ+ state relatively more than 3Δr in both cases and suggests that 1Σ+ is the ground state of ScF, in agreement with experiment. This study provides additional information on the electronic structures of molecules of the transition metals and demonstrates the possibilities of term inversions in other monoxides of the titanium family.
Influence of Rotational Levels on Slow-Neutron Scattering by Linear Gases
Authors: Lurie Norman A.
Published: January 2005

Calculations of slow-neutron partial differential scattering cross sections are reported for molecules with linear symmetry in which the quantum-mechanical nature of the rotational levels is taken explicitly into account. The method used is an extension of Griffing's results to nonspherical molecules. The calculations for HF, HCl, N2, and HCN gases are compared to calculations based on the Krieger—Nelikn approximation, and the failure of the latter method to account correctly for rotational-energy transfers is pointed out.
Hartree—Fock Theory of Atomic Properties
Authors: Musher Jeremy I.
Published: January 2005

A procedure is presented for the calculation of atomic properties to any desired degree of accuracy using straightforward perturbation theory (PT). The ``uncoupled'' Hartree—Fock perturbation theory (UCPT) result is shown to agree with the first term of the PT expansion, while the ``coupled'' Hartree—Fock perturbation theory (CPT) result is shown to differ from the first two terms of the PT expansion only by higher-order terms. When the CPT result is improved upon using perturbation theory, all the ``coupling'' or ``self-consistency'' terms vanish identically and the result of the PT procedure is obtained. There is thus no advantage gained in performing the more difficult computations of CPT. The ``variants'' in UCPT discussed by Langhoff et al. are shown to be leading terms in the expansion of the UCPT result itself.
Raman and Infrared Spectral Studies of Aqueous Calcium Nitrate Solutions
Authors: Irish D. E. , Walrafen G. E.
Published: January 2005

Extensive Raman and infrared spectral data have been obtained from studies of aqueous solutions of Ca(NO3)2, as well as from mixtures involving high Ca2+–NO3− or NO3−–Ca2+ concentration ratios. The removal of the degeneracy of the E′ modes, even in dilute solution, and the activity of the A′ mode in the infrared spectrum suggest that the symmetry of the nitrate ion has been lowered by solvation with water. The perturbation is enhanced by ionic interaction with hydrated calcium ions. The implications of the model are discussed.
Molecular Vibrations of the Trigonal Bipyramidal Model MXY2Z2: Pentacoordinated Molecules. XI
Authors: Holmes Robert R.
Published: January 2005

A vibrational analysis of the trigonal bipyramidal model of C2v symmetry neglecting anharmonicity is given in terms of the FG matrix system. The angular dependence of the secular equations is derived in expanded form. A normal-coordinate analysis of CH3PF4, PClF4, and PCl2F3 based on recent vibrational data provides a partial description of the potential function for this symmetry. The resulting force constants show that equatorial P–F bonds are considerably ``stronger'' than axial P–F bonds in these molecules.
Test of Laplace Transform Technique for Energy-Level Density Calculations
Authors: Forst W. , Prášil Z. , St. Laurent P.
Published: January 2005

The series obtained by Haarhoff and Thiele for the density of vibrational states by the Laplace transform expansion technique has been generalized to obtain the density of vibration—rotation states. The resulting series expression is compared at several energies with the exact count and with a compact formula due to Haarhoff. Two cases are considered: a ``large'' molecule with many vibrations and rotations and a ``small'' molecule with few vibrations and rotations. The series expression gives a much better approximation than Haarhoff's formula for the ``large'' molecule, but there is little to choose between the two in the case of the ``small'' molecule.
Velocity Dependence of the Collisional Excitation Transfer Processes of a Resonant Type
Authors: Watanabe Tsutomu
Published: January 2005

The velocity dependence or the temperature dependence of the excitation transfer processes A*+A→A+A*,A*+B→A+B++e, were discussed within the limit of the straight-line trajectory and the impact-parameter method. It has been shown that the velocity dependence corresponds directly with the radial part of the interaction in some cases. In the discrete—discrete resonant case, the cross section σ is proportional to v−2/(n−1) and in the discrete—continuum case it is proportional to v−2/(2n−1), where v is the relative incident velocity of the atom and n is the inverse exponent of the radial part of the interaction.
Radio-Frequency Spectra of KF and KCl by the Molecular-Beam Electric-Resonance Method
Authors: van Wachem R. , Dymanus A.
Published: January 2005

The molecular-beam electric-resonance method has been used to obtain quadrupole-coupling constants eq(v)Q, spin—rotation constants c, and tensorial and scalar spin—spin interaction constants dT and dS for 39K19F, 39K35Cl, and 39K37Cl in several vibrational states. For 39K35Cl and 39K37Cl also the electric dipole moments have been determined. For the first five measured vibrational levels of 39K19F and 39K35Cl, the values of the quadrupole coupling constants and dipole moments can be written as a polynomial of second degree in (v+½).
Physical Properties of Aromatic Hydrocarbons. II. Solidification Behavior of 1,3,5-Tri-α-Naphthylbenzene
Authors: Magill J. H. , Plazek D. J.
Published: January 2005

The kinetics of solidification of 1,3,5-tri-α-naphthylbenzene have been studied from 25° above the glass temperature (69°C) almost to the crystal thermodynamic melting point (199°C). The crystal growth rate has been analyzed using current theories of crystallization and a mechanism for crystal growth has been proposed. It has been demonstrated that mass transport in crystal growth and viscous flow do not have the same temperature dependence. The morphology of the solid phase is discussed. Pertinent parameters pertaining to the glassy state of this material are also reported.
Radial Distributions of Ions for a Primitive Model of an Electrolyte Solution
Authors: Carley David D.
Published: January 2005

Radial distribution functions are computed for the primitive model of an electrolytic solution using the Percus—Yevick and convolution-hypernetted-chain integral equations. The results are compared with the Debye—Hückel theory. The Debye—Hückel approximation appears to be particularly bad when the density is great enough that the hard core plays a significant role in determining the radial distribution functions.
Adsorption of Barium on Tungsten: Measurements on Individual Crystal Planes
Authors: Schmidt L. D.
Published: January 2005

The adsorption of barium on the (110), (211), (100), (111), and (221) planes of a tungsten field emitter was studied for both thermally equilibrated and unequilibrated adsorbate layers. At low coverage the equilibrated atom densities on the (110) and (221) planes are ∼100 times greater than on the (211) and (100) planes, while for θ̄>0.2 equilibrated atom densities are essentially identical on all planes. Dipole moments are roughly the same on all planes, corresponding to q∼1.0 electron/atom. At high coverages (θ∼0.8) there is evidence for rearrangement on heating to produce pronounced work function minima on the close-packed crystal planes.

These results are interpreted in terms of the previously suggested model of electropositive adsorption, with generally good agreement obtained. The influence of the small size of the substrate on the measurements is considered, and it is shown that these results should be identical to those on perfect macroscopic surfaces in most situations.
Study of the Electronic Structure of Molecules. II. Wavefunctions for the NH3+HCl→NH4Cl Reaction
Authors: Clementi Enrico
Published: January 2005

Ab initio computations are presented for the reaction NH3+HCl→NH4Cl. The two reactants are studied at a large number of positions and for each point an SCF LCAO MO wavefunction and the corresponding total energy are obtained. These results are then collected in an energy surface diagram. All the electrons of the system are considered and a contracted Gaussian basis set has been used in this work. This study considers the two reactants as one system and both charge transfer as well as hydrogen-bonding characteristics are analyzed within the molecular-orbitals framework instead of the valence-bond approximation as customary in the past. The reaction has been analyzed for the case where the HCl approaches the NH3 molecule in a path normal to the plane of the three hydrogens of NH3; the H atom of HCl is between the N atom and the Cl atom. The first stage of the reaction (NH3 and HCl at large distances) indicates mutual polarization of the two molecules. In this region the SCF LCAO MO approximation is rather poor since it can not take into consideration dispersive forces. With HCl closer to the ammonia molecule, there is first hydrogen bonding formation and partial charge transfer. When NH4Cl is formed the molecule is stable with respect to the NH3 and HCl components by about 19 kcal/mole. No activation energy has been found in the reaction, contrary to previous assumptions. The computed geometry of the NH4Cl molecule at the equilibrium configuration is discussed in this work.
Chemistry of Irradiation Induced Polytetrafluoroethylene Radicals: I. Re-examination of the EPR Spectra
Authors: Siegel Seymour , Hedgpeth Herbert
Published: January 2005

The electron paramagnetic resonance (EPR) spectra of the radicals formed during the γ irradiation of polytetrafluoroethylene (PTFE) are examined and assigned. It is shown that both chain radicals (e.g., RCF2CFCF2R) and propagating radicals (e.g., RCF2CF2·) are formed and stabilized when PTFE is irradiated in vacuum and at room temperature; the yield of the chain radical is 10 times that of the propagating radical. When PTFE is irradiated in air, the peroxide radicals RCF2CFOO·CF2R and RCF2CF2OO· are stabilized. The difference in yields of the two peroxide radicals is a function of total dosage, with the relative contribution of RCF2CF2OO· increasing with increasing dose. Both of the peroxide radicals are converted to the RCF2CF2· radical when they are irradiated with ultraviolet light (λ=280±20 mμ) in vacuum. Some chain radical is produced by the photolysis of its peroxide, but the yield of the propagating radical is 50 times that of the chain radical. The EPR spectrum of the RCF2CF2· radical consists of three sets of lines. The central set is a well-resolved triplet with a splitting between adjacent lines of 16±0.5 G. The wing lines are broadened by anisotropic nuclear hyperfine interactions, and the expected triplet structure is not resolved. From the room-temperature spectrum, it is estimated that the isotropic component of the α-fluorine interaction is ∼85 G. Also, from the 77°K spectrum, it is estimated that the maximum anisotropic component of the hyperfine interaction tensor is ∼140 G. The g value for this radical is 2.0038±0.0001.
Accurate Single-Center Expansions Using Slater-Type Orbitals: Hydrogen Molecule
Authors: Hayes Edward F.
Published: January 2005

Single-center wavefunctions are determined for the lowest 1Σg+ state of H2 for internuclear separations of 1.2, 1.4, and 1.6 bohrs. The calculated binding energy is 4.70 eV (exact, 4.75 eV). The equilibrium bond length, and the quadratic and cubic force constants are computed and are in excellent agreement with the very accurate calculations of Koℏos and Wolniewicz.
NMR Study of Ferroelectric LiNbO3 and LiTaO3. I
Authors: Peterson G. E. , Bridenbaugh P. M. , Green P.
Published: January 2005

A study of the 7Li nuclear magnetic resonance in a LiNbO3 single crystal is made and the electric field gradient at the lithium site is determined. Electric-field-gradient calculations indicate that the net charge on the niobium is +1.59 while that on the oxygens is −0.86. This shows that the niobate ion is predominately covalently bonded. The 93Nb resonance in a LiNbO3 single crystal and the 7Li resonance in powder samples of LiNbO3–LiTaO3 solid solutions are reported.
Radiation Damping of Exciton States in Molecular Crystals
Authors: Silbey Robert
Published: January 2005

Using the Heitler—Ma method, it is explicitly shown that there is no radiation damping of exciton states in molecular crystals when periodic boundary conditions are employed.
Contribution to the Friction Coefficient from Time Correlations between Hard and Soft Molecular Interactions
Authors: Davis H. Ted , Palyvos J. A.
Published: January 2005

The contribution to the friction coefficient arising from correlations between hard and soft forces is evaluated using the linear-trajectory approximation. This contribution, previously neglected in the theories of Helfand and Rice and Allnatt, is found to be of the same order of magnitude as the hard-core contribution, which, itself, is important for much of the liquid range of temperature and density.
Mass-Spectrometric Study of the Reactions of Deuterium and Hydrogen Atoms with Nitric Oxide
Authors: Kohout F. C. , Lampe F. W.
Published: January 2005

The details of the reactions of deuterium and hydrogen atoms with nitric oxide in D2—NO and H2–NO mixtures (less than 1% NO) have been studied by a mass-spectrometric method. Nitroxyl is produced as the primary product and rapidly attains a steady-state concentration. Further reaction of nitroxyl with nitroxyl produces nitrous oxide and water with a rate constant of 6.7±2.2×10−16 cm3 molecule−1·sec−1. The reaction of nitroxyl with hydrogen atoms produces small amounts of hydroxylamine, and proceeds, at the highest pressure employed (70 torr), with a rate about 1/70 of the rate of formation of nitrous oxide. From considerations of the effect of total pressure on the steady-state level of nitroxyl, the rate constant for the deuterium-atom abstraction of deuterium from DNO is estimated to lie between 10−13 and 10−12 cm3 molecule−1·sec−1. The vessel surfaces play no part in the reaction, other than to adsorb the products, water and hydroxylamine.
Ab Initio Studies of Small Molecules Using 1s Gaussian Basis Functions. I. Exploratory Calculations
Authors: Schwartz Maurice E. , Schaad L. J.
Published: January 2005

Exploratory studies of the ground states of H2+, H2, He2+ +, and HeH+ using a basis of 1s Gaussian orbitals are presented. The emphasis is on the direct calculation of molecular wavefunctions with complete optimization of all parameters including the position and size of all orbitals. For the two-electron systems both self-consistent-field molecular-orbital and many-configuration studies are done. Results for total energies, MO orbital energies, and equilibrium bond lengths are satisfactory when compared to other variational studies of various degrees of accuracy, including some nearly exact studies. As expected, the larger nuclear charge in He2+ + and the lower symmetry of HeH+ make convergence slower than for H2+ and H2. Further examination of the H2 results is made by calculation of the averages of the nonenergy quantities x2, z2, and 1/r12.
Molecular One-Center Two-Electron Integrals Containing a Function of the Interelectronic Distance
Authors: Grein Friedrich , Hawton Margaret H.
Published: January 2005

Two-electron integrals are solved for arbitrary one-center functions of r1, r2, and r12, combined with spherical harmonics of the angular coordinates.

All matrix elements are derived in detail for a configuration-interaction wavefunction, multiplied by the correlation factor 1+ar12, with complex a. Closed-form expressions of the matrix elements are given for a Shull—Löwdin basis set with a single scaling parameter.

Applications to ground state and lowest excited 1A1′ state of H3+, with equilateral-triangular structure show that the improvement in energy due to the correlation factor is from 0.01 to 0.03 a.u.
Numerical Determination of Chemical Equilibrium and the Partitioning of Free Energy
Authors: White W. B.
Published: January 2005

A simplified procedure is developed for the numerical determination of the equilibrium composition of complex mixtures. Computational steps have been simplified and numerical difficulties arising in previous methods are eliminated. A new concept leading to the allocation of free energy to the atoms or elementary particles comprising a molecule or other composite structure is suggested. Numerical values are derived for the free energy of hydrogen and oxygen atoms in a water molecule.
Microwave Spectrum of Allyl Alcohol
Authors: Murty A. Narasimha , Curl R. F.
Published: January 2005

The microwave spectrum of allyl alcohol has been investigated in the frequency range 8–35 Gc/sec, for the normal sample (CH2CHCH2OH), deuterated sample (CH2CHCH2OD), and 18O-substituted sample (CH2CHCH218OH). For the normal sample, 20 transitions, which can be attributed to rotational absorption by a gauche form of the molecule, are reported both for the ground vibrational state and the first excited vibrational state. The rotational constants of the deuterated sample and 18O-substituted sample indicate the assigned conformation is the gauche form which allows an H bond between the π electrons and the OH group. The molecular-dipole-moment components have been determined from the Stark-effect measurements, |μa|=1.41±0.02 D, |μb|=0+0.07 D, |μc|=0.65±0.01 D, and μtot=1.55±0.04 D.
Acetylene—Oxygen Reaction in Shock Waves. Origin of CO2
Authors: Homer J. B. , Kistiakowsky G. B.
Published: January 2005

The ir emissions from CO and CO2, formed in the C2H2–O2 reaction in a shock tube, have been observed as a function of time. By calibrating these emissions in terms of concentrations and by comparing them with the emission of CH* (A 2Δ→X 2π), produced in the same reaction, it has been possible to confirm that CO2 is formed in the early stages by a reaction other than CO+OH→CO2+H. This reaction involves a primary carbon-containing radical and an O2 molecule, and its rate at 1800°K is 5% of the rate of formation of CO, produced by a similar reaction.

The importance of the reaction CO+OH→CO2+H in the later stages of oxidation has been examined as a function of the initial O2/C2H2 ratio, and the growth of OH concentration during the reaction elucidated.

More decisive proof is given that CH* is produced by a reaction which is second order in reaction intermediates.
Absorption Spectra of Pr3+ and Nd3+ Doped in Lanthanum Sulfate
Authors: Viswanathan C. R. , Radisavljevis K. , Wong Eugene Y.
Published: January 2005

The crystal-field parameters of lanthanum sulfate are calculated by studying the absorption spectrum of Pr3+- and Nd3+-doped lanthanum sulfate. These values are compared with the previously obtained parameters for lanthanum ethyl sulfate. It is shown that A20〈r2〉 is quite large in the sulfate in comparison with the ethyl sulfate.
Electronic Excited States of Benzene and Ethylene
Authors: Clark P. A. , Ragle J. L.
Published: January 2005

Energies of low-lying excited electronic states of benzene have been calculated using the semiempirical SCF scheme of Pople, Santry, and Segal. Semiquantitatively transferable parameters are chosen by fitting the theory to the ionization potential and the position of the 3B1u state. The principal requisite modification of parameters concerns a reduction in scale of resonance integrals from those suggested by Pople et al.; subsidiary small adjustments are required in diagonal core parameters.

The theory predicts several interesting features which are at variance with the usual interpretation of the near-ultraviolet spectrum but which are not in irrevocable conflict with experiment. When these are taken into account, positions of other states, calculated without scaling of atomic-orbital Coulomb repulsion integrals, are in good agreement with experiment.

Representative results are also presented for ethylene.
Chlorine and Deuteron Relaxation Time Measurements in Liquid HCl and DCl
Authors: Boehme H. , Eisner M.
Published: January 2005

Measurements of chlorine T2 in liquid HCl and DCl have been made over the temperature range of −40° to 60°C. Estimates of the reorientational correlation time made possible by the chlorine measurements were used to evaluate the proton intramolecular dipole contribution which was subtracted from the total intramolecular contribution to obtain the proton spin—rotational contribution. The magnitude of the spin—rotational contribution thus obtained compares with that estimated by Krynicki and Powles.

Deuteron T1 times in liquid DCl were measured over the temperature range of −75° to 25°C and found to differ considerably both in magnitude and temperature dependence from deuteron T2 times. Estimates of the quadrupole contribution to the deuteron (1/T1) and, thus, a value of 2.0×1017 V/cm2 for the electric-field gradient at the deuteron site in DCl were made by use of the reorientational correlation time from chlorine measurements.
Photoelectron Spectra of the Halogens and the Hydrogen Halides
Authors: Frost D. C. , McDowell C. A. , Vroom D. A.
Published: January 2005

A spherical-grid photoelectron spectrometer has been used to measure the ionization potentials of HF, HCl, HBr, HI, F2, Cl2, Br2, and I2. The relative transition probabilities to several of the ionic states are given. There is evidence that the 2Σ+ ionic states in HI+, Cl2+, Br2+, and I2+ are unstable.
NMR Studies of a Series of Aliphatic Nitroxide Radicals
Authors: Kreilick Robert W.
Published: January 2005

We have examined the NMR and ESR spectra of a series of aliphatic nitroxide radicals. Isotropic coupling constants were calculated from the shifts of the NMR lines. The NMR shifts were investigated as a function of solvent and temperature. Coupling constants determined from NMR spectra were used to calculate ESR spectra. The experimental and theoretical ESR spectra were in good agreement.
Structure of the Triplet Distribution Function
Authors: Henderson Douglas
Published: January 2005

In the Born, Green, and Yvon (BGY) theory of fluids it is necessary to postulate a relation connecting the pair distribution function g12 and the triplet distribution function g123. The most famous relation is the superposition approximation which asserts that the triplet distribution function is equal to the product of the pair distribution functions of the three constituent pairs of molecules. If the resulting expression for g123 is expanded in powers of the density it is found that the lowest-order term is exact and that the higher-order terms are approximated with fair success. In addition, the superposition approximation gives good values for g123 at high densities. However, the BGY theory is very sensitive to errors in g123 and, as a result, poor values for the equation of state are obtained when the BGY theory is used in conjunction with the superposition approximation. In this investigation two improvements to the superposition approximation are examined. These approximations are a considerable improvement over the superposition approximation. Both yield an expression for g123 which is exact in the lowest- and first-order terms in the density and yield good approximations to the second-order term in the density. Numerical results are given for Gaussian molecules and for hard spheres.
Lifetime Measurements on CH(A 2Δ), CH(B 2Σ−), and C2(A 3Πg) by the Phase-Shift Method
Authors: Fink E. H. , Welge K. H.
Published: January 2005

The radiative lifetimes of CH(A 2Δ), CH(B 2Σ−), and C2(A 3Πg) are measured applying the phase-shift method. The excitation of the radicals is performed by electron bombardment of CH4 and C2H2 at low pressures. The following lifetimes are obtained: τ(A 2Δ) = (5.4±0.4)×10−7 sec, τ(B 2Σ−) = (4.0±0.6)×10−7 sec, τ(A 3Πg) = (2.0±0.5)×10−7 sec. As far as possible oscillator strengths are deduced.
Phonon Effects in the uv Spectrum of Crystalline Hexamethylbenzene
Authors: Maria H. J. , Zahlan A. B.
Published: January 2005

The intensity and linewidth of the 0–0 transition and some vibronic bands of crystalline hexamethylbenzene have been measured in the temperature range 4.2° to 70°K. It is found that the two components of the 0–0 transition polarized along the a′ and c′ axes, respectively, have different temperature dependence. The effect of phonons on the oscillator strength of very weak transitions is discussed.
EPR Study of NO Adsorbed on Magnesium Oxide
Authors: Lunsford Jack H.
Published: January 2005

The EPR spectra of two paramagnetic species were observed when nitric oxide was adsorbed on high-surface-area magnesium oxide. The spectrum of one species which is interpreted as NO22− was observed at room temperature on MgO that had been degassed at 800°C. It was characterized by gxx=gyy=2.0068, gzz=2.0025, and axx≃ayy≃0 G; for 14NO adsorbed azz=43 G while for 15NO adsorbed azz=61 G. The other radical is identified as the adsorbed NO molecule in a strong field at the surface such that the spin—orbit coupling is partially quenched. Its spectrum was observed only at low temperatures (−180°), and was characterized by gxx=gyy=1.995 with gzz=1.90 for MgO degassed at 800° or at 300°C. For 14NO, axx=33 G and azz<10 G while for 15NO, axx=47 G and azz<10 G. Theoretical predictions as well as the spectra of the isoelectronic N2− molecule—ion are in accord with the assignment of this spectrum. Both paramagnetic species could be partially removed by degassing the sample at room temperature, notwithstanding the rather strong electronic interactions which are indicated by the spectra.