bluuebunny/crossref_metadata_2025 huggingface dataset:
Mössbauer Effect in Iron (III) Acetylacetonate and Chemical Consequences of K Capture in Cobalt (III) Acetylacetonate
Authors: Wertheim G. K. , Kingston W. R. , Herber R. H.
Published: January 2005

The resonance absorption of 14.4 keV gamma rays in Fe57 (Mössbauer effect) has been observed in Fe(III) and Co(III) acetylacetonate, the former used as an absorber against a source of Co57 diffused into metallic chromium, the latter as a Co57 labeled source against an K4Fe(CN)6 (38%Fe57) absorber. The Fe(III) acetylacetonate absorber spectrum shows a single broad line (Γ½=1.83±0.09 mm sec—1) with an isomer shift of 0.50±0.09 mm sec—1. The Co(III) acetylacetonate source shows a complex spectrum which can be resolved into a single peak assigned to Fe(III) and a quadrupole split pair of lines assigned to Fe(II). These data are interpreted in terms of the chemical consequences following K capture in Co57, and suggest a twofold preference for the stabilization of the higher charge state in the Co(III) acetylacetonate matrix. No evidence for ionic charge states higher than 3+ is observed, and it is assumed that these species—if formed as a consequence of the prior nuclear event—have been reduced to the observed states in times short compared to 10—7 sec.
Theoretical Interpretation of Reactions Occurring in Photochlorination
Authors: Johnston Harold S. , Goldfinger Paul
Published: January 2005

The Arrhenius A and E factors of over 60 elementary reactions in photochlorination systems have recently been evaluated experimentally in this and other laboratories. In this article a uniform treatment of most of these reactions is given by activated complex theories. Two parameters are fit to the data from two activation energies. The other activation energies follow the expected trend for reactions of chlorine atoms with hydrocarbons, but the reactions of chlorine atoms with chlorinated hydrocarbons do not follow the expected trends. For reactions with activation energy, the theory accounts very well for the magnitudes and trends of the Arrhenius A factors. For reactions with no activation energy, the activated complex theory as used by Gorin accounts for the order of magnitude of the rate constants of the group as a whole, but it fails to account for several pronounced trends in the data and is judged to be of no predictive value. For certain limited types of chemical reactions and over restricted ranges of experimental conditions, activated-complex theory is judged capable of predicting some kinetic factors. The range of predictions is small, but is not zero.
Second-Order Splittings in the ESR Spectra of Organic Radicals
Authors: Fessenden Richard W.
Published: January 2005

More lines than can be explained by first-order theory have been observed in the ESR spectra of several alkyl radicals in solution. The additional structure is predicted if the usual treatment is extended to second order in the coupling constants. This extension has been made in such a way as to eliminate the necessity of explicitly considering the 2n nuclear-spin wave functions which occur with spin-½ nuclei. The spectrum of the ethyl radical is used to demonstrate the agreement of actual spectra with the treatment presented here. A table is included which facilitates calculation of the second-order structure in the spectra of radicals containing spin-½ nuclei.
Diffusional Contribution to the Total Flow from a Knudsen Cell
Authors: Winterbottom W. L. , Hirth J. P.
Published: January 2005

It has been recognized for sometime that the geometry of a Knudsen effusion cell influences the kinetics of the molecular effusion of the vapor from within the cell. However, no treatment has been reported of the contribution to the effusion current made by the surface diffusion out through the orifice of the effusate adsorbed on the walls within the cell. The applicable integro-differential equations which describe the steady-state kinetics for both surface diffusion and vapor effusion out through the orifice have been solved approximately. The derived relations predict that under specified conditions the diffusion flux for the orifice dimensions commonly employed may contribute an appreciable fraction of the total weight loss of the cell during an effusion experiment. If not taken into account, this diffusional contribution would yield equilibrium vapor pressures in excess of the actual values.
Low-Energy 5Σ+g States of the Nitrogen Molecule
Authors: Mulliken Robert S.
Published: January 2005

The wave functions of the two 5Σ+g states of N2 derivable from configurationally unexcited (s2p3) atoms, one from 4S+4S atomic states, the second from 4S+2D states, are examined. With the help of empirical data on the normal state of F2, to which the valence-bond structure of the lower of the two 5Σ+g states is closely related, estimated potential curves for the two states are constructed. It is shown that for the lower 5Σ+g state, the theoretically expected curve agrees rather well with that deduced from empirical evidence {see Carroll's accompanying paper [J. Chem. Phys. 37, 805 (1962) ]}. The wave function of the 5Σ—g state from 4S+2P atoms is also given.
Exchange Interaction with Electrolytically Generated Benzonitrile Negative Ion
Authors: Ludwig Peter , Adams Ralph N.
Published: January 2005

Benzonitrile negative ion prepared by the in situ electrolytic generation technique shows strong exchange interaction with the parent benzonitrile. In dimethylformamide as solvent system, the EPR spectrum varies between the expected 54-line pattern and a single narrow line depending on the benzonitrile concentration. A bimolecular rate constant of ∼108 liters mole—1 sec—1 can be estimated.
Color Centers in a Cerium-Containing Silicate Glass
Authors: Stroud Jackson S.
Published: January 2005

X-ray irradiation of glass with the weight percent composition 75% SiO2, 25% Na2O produces color centers which absorb visible light. Cerium in the glass prevents the formation of these centers. The nature of the centers and the mechanism by which cerium prevents their formation are studied by measuring the optical absorption changes caused by irradiation of glasses containing small concentrations of Ce3+ and Ce4+. The conclusions are: In cerium-free glass, trapped holes cause optical absorption bands with maxima near 4400 and 6200 Å. By capturing holes, Ce3+ inhibits the formation of these two bands. The probability that a hole escapes capture by Ce3+ is exp (—v3c3), where c3 is the Ce3+ concentration and v3=(9±2) × 104 Å3. Trapped electrons cause an optical absorption band that has a maximum in the uv and that extends to 6000 Å in the visible. Ce4+ inhibits the formation of this band by capturing electrons.
Luminescence of Solids Excited by Surface Recombination of Atoms. II. Recombination Coefficients
Authors: Sancier Kenneth M. , Fredericks William J. , Hatchett James L. , Wise Henry
Published: January 2005

The nitrogen atom recombination coefficients of the lumophors CaO and CaO:Mn for release of luminescence and heat by the lumophor were evaluated from an analysis of the atom concentration profile, established in a cylinder of finite length into which the atoms diffuse because of the catalytic activities of the walls and the lumophor surfaces. The kinetics of the recombination leading to luminescence and heat are found to be first order. The values of the recombination coefficients determined for heat appear to be slightly larger than those for luminescence, but this difference is probably no greater than the precision of the measurements. The possibility that the difference arises from the presence of more than one active species in the gas is discussed. The value of the recombination coefficient of Pyrex glass for nitrogen atoms was determined and found to be in good agreement with published values.
Luminescence of Solids Excited by Surface Recombination of Atoms. III. Measurement of Absolute Energies Released as Luminescence and Heat
Authors: Sancier Kenneth M. , Fredericks William J. , Wise Henry
Published: January 2005

The absolute energies of luminescence and heat produced by heterogeneous nitrogen atom recombination on CaO were measured by actinometry and calorimetry, respectively. The heat energy produced on MgO was also measured, and the luminescence energy was estimated from its luminescence intensity relative to CaO. The ratio of energy released as luminescence to that as heat is about 2×10—3 for CaO, and about 8×10—5 for MgO. The rate of heat production in CaO and MgO may be explained in terms of heterogeneous atom recombination.
4-Fluorotoluene: Chemical Thermodynamic Properties, Vibrational Assignment, and Internal Rotation
Authors: Scott D. W. , Messerly J. F. , Todd S. S. , Hossenlopp I. A. , Douslin D. R. , McCullough J. P.
Published: January 2005

Thermodynamic data were obtained for 4-fluorotoluene and correlated by methods of statistical mechanics to derive values of the chemical thermodynamic properties in the ideal-gas state from 0° to 1500°K. A vibrational assignment consistent with the calorimetric data was obtained. Internal rotation was shown to be essentially free. Experimental studies provided the following information: values of heat capacity for the solid (13°K to the triple point), the liquid (triple point to 361°K), and the vapor (377° to 500°K); the triple-point temperature; the heat of fusion; thermodynamic functions for the solid and liquid (0° to 390°K); heat of vaporization (347° to 390°K); parameters of the equation of state; and vapor pressure (341° to 428°K).
X-Ray Study of Pyrolytic Graphites
Authors: Guentert O. J.
Published: January 2005

A picture of the structure of pyrolytic graphites has been obtained from an x-ray study of several samples deposited under various conditions at temperatures ranging from 1700° to 2500°C. The structural features investigated include preferred orientation, layer order, and crystallite sizes and strains perpendicular and parallel to the basal layers. Deposits made at 1700°C show preferred orientation of the order of 10:1, crystallite dimensions below 100 Å, nearly random layer order, and high strains in the c direction. In materials deposited at 1900°C and higher, the preferred orientation is sharply increased to values between 103:1 and 104:1, and representative values for the crystallite dimensions L̄c and L̄a are 200 and 265 Å, respectively. The layer order remains nearly random, however, and the c-direction strains show only a slight reduction. The basal layers themselves are approximately strain-free.
Self-Diffusion Coefficients of Carbon Dioxide at 1180°—1680°K
Authors: Ember G. , Ferron J. R. , Wohl K.
Published: January 2005

Self-diffusivities of carbon dioxide at 1180°—1680°K have been determined by a new version of the continuous flow method. Results can be correlated with previous low-temperature data (mean error 1.5%) in terms of a single set of parameters of the Lennard-Jones (6–12) potential (σ=2.70 Å, ε/k=871°K) valid for the entire temperature range (195°—1680°K). Literature values of viscosity (200°—1500°K) may also be correlated by a single set of parameters (σ=3.94 Å, ε/k=200°K). It is suggested that one can include both viscosity and self-diffusivity data in the same correlation if the nonsphericity of the CO2 molecule, which may have the strongest effect at high temperatures, is accounted for. This can be done approximately by use of the nonsphericity factors calculated by Curtiss and co-workers for rigid, spherocylindrical molecules, if one assumes a temperature dependence for the factor such that it becomes about unity at room temperature.
Wave Functions for Anharmonic Oscillators by Perturbation Methods
Authors: Shorb A. M. , Schroeder R. , Lippincott E. R.
Published: January 2005

Approximate wave functions and the corresponding energies computed by perturbation methods to the second order are given in tabular form for anharmonic potentials which have been expanded in polynomial series up to the sixth power in the displacement x.
On the Analysis of Spectra in Transmission through Thin Films
Authors: Montgomery D. J. , Yeung K. F.
Published: January 2005

A technique to investigate the adequacy of the damped harmonic-oscillator model for infrared absorption in thin films is described, together with a simple procedure for extracting the material parameters and the film thickness from the transmission curve. The methods are illustrated by application to several ionic crystals.
Multiple Reaction Vapor Transport of Solids
Authors: Lever R. F.
Published: January 2005

A model is developed for one-dimensional steady-state diffusion-limited transport of solid in the presence of several chemical equilibria. The assumption that all the binary diffusion coefficients may be considered equal enables the flow to be expressed very simply in terms of the diffusion coefficient and a simple parameter describing the over-all gas composition, without reference to individual molecular species. Thermal diffusion is neglected.
Spin Densities in the Cyclohexadienyl Free Radical
Authors: Fischer Hanns
Published: January 2005

The spin densities in the cyclohexadienyl free radical are calculated using valence-bond and molecular-orbital approximations. The theoretically obtained values are in reasonable agreement with the spin densities derived from the electron spin resonance spectrum of this radical in irradiated benzene.
Continuum Radiation from Ionized Rare Gases in Reflected Shock Waves
Authors: Mies Frederick H.
Published: January 2005

Observations have been made of the temperature, pressure, and frequency dependences of the visible and ultraviolet continuum radiation emitted by the thermally ionized rare gases Ar, Kr, and Xe. The plasmas, whose continua generally are attributed to the radiative recombination of free electrons and ions, have been formed in reflected shock waves in which the equilibrium temperatures range from 7500° to 12 000°K and the electron densities range from 1015 to 1018 cm—3. Some distance behind the reflected shock wave a region is found which possesses the predicted shock properties and in which the intensity of the continuum radiation attains a steady-state value. This steady-state intensity has been examined at seven wavelengths from 2451 to 4800 Å; in addition, the ratio of the Kr continuum to the 4319.6 Å Kr line intensity was observed. The continuum intensity is shown to be proportional to the electron density squared and essentially independent of the ion involved. The observed e—hv/kT decay of the intensity in the ultraviolet, together with the total temperature dependence and the measured absolute intensity of the continuum, demonstrates that the continuum originates from radiative recombination. The expected temperature and pressure behavior also is found for the Kr line emission.
Microwave Spectrum and Barrier to Internal Rotation of cis-1-Fluoropropylene
Authors: Beaudet Robert A. , Wilson E. Bright
Published: January 2005

The microwave spectrum of cis CH3CF=CHF was investigated in the region 8–36 kMc. The rotational constants are 17 826.09, 5656.57, and 4406.91 Mc. The value of the inertial defect indicates a planar structure except for the two methyl hydrogen atoms. The barrier to internal rotation of the methyl group was determined to be 1057±50 cal from the splitting of the ground-state transitions. The dipole moment is 1.46 D. The sharp lowering of the barrier on introduction of the cis fluorine suggests a direct nonbonded interaction of the fluorine and methyl hydrogens.
Study of the Electron Density Distribution in the Simpler Hydrocarbons
Authors: Roux Monique , Cornille Marguerite , Burnelle Louis
Published: January 2005

The electronic charge distribution is calculated in the molecules of acetylene and ethylene, by making use of a function which characterizes the effect of bond formation on the electronic density. In agreement with earlier results on methane, the effect is found to consist in a charge removal from the vicinity of the nuclei and a build up of electron density in the regions of the bonds.

In acetylene, the calculation of the charge drifts subsequent to the bonding indicates that these are fairly small, as had been found earlier in simpler molecules. It is also observed that the electrons associated with the CC bond tend to accumulate, in ethylene, above and below the molecular plane, and in acetylene, at some distance from the CC axis. This point is in favor of the Pauling picture of bent multiple bonds.
Unimolecular Decomposition of Chemically Activated sec-Butyl and sec-Butyl-d1 Radicals. The Reaction of H and D Atoms with trans-Butene-2 and Butene-1
Authors: Kubin R. F. , Rabinovitch B. S. , Harrington R. E.
Published: January 2005

H and D atoms were reacted with trans-butene-2 to produce vibrationally excited sec-butyl and sec-butyl-d1 radicals with a range of excess energies with respect to C–C rupture. Previous work [R. E. Harrington, B. S. Rabinovitch, and H. M. Frey, J. Chem. Phys. 33, 1271 (1960)] on butene-1 has also been extended. Observed rate constants for the unimolecular decomposition of these sec-butyl radicals relative to collisional stabilization were obtained as a function of pressure. Possible competing side reactions are discussed and evaluated. Butenyl radical formed by H abstraction from butene-2 tends to retain the geometric configuration of the original butene; also, the ratio of the pentenes formed by methyl coupling, illustrative of the two principal resonance structures, is (3-methyl-butene-1) / (total pentene-2)∼0.4. An expected energy isotope effect for D atoms, which give sec-butyl-d1 radicals having ∼1.9 kcal/mole more vibrational energy than the corresponding sec-butyl radical formed from H atoms, was seen. With butene-1 or butene-2 reactant, no evidence was found for H-atom migration in the excited sec-butyl radical formed. The disproportionation/recombination ratio of sec-butyl radicals was found from all systems to be 0.63.
On the Kinetic Theory of Simple Dense Fluids. XI. Experimental and Theoretical Studies of Positive Ion Mobility in Liquid Ar, Kr, and Xe
Authors: Davis H. Ted , Rice Stuart A. , Meyer Lothar
Published: January 2005

We report in this paper measurements of the mobility of positive ions in liquid Ar, Kr, and Xe at various temperatures and pressures, and an extension of the theory of Rice and Allnatt to the description of ionic motion. It is found that

(a) The magnitude, the pressure dependence, and the temperature dependence of the positive ion mobility in liquid Ar, Kr, and Xe can be quantitatively accounted for by an extension of the theory of Rice and Allnatt [S. A. Rice and A. R. Allnatt, J. Chem. Phys. 34, 2144 (1961)]. As in our previous studies of self-diffusion in these same liquids [J. Naghizadeh and S. A. Rice, J. Chem. Phys. 36, 2709 (1962)], it is found that negative contributions to the momentum autocorrelation function are of dominant importance.

(b) Modification of the simple Nernst—Einstein relationship between the charge mobility and the self-diffusion constant of the parent atom by inclusion of the effects of polarization leads to quantitative agreement between theory and experiment.

(c) The effect of the long-range Coulomb potential is to increase the local density about the ion and thereby to increase the frictional forces arising from the short range interaction potential. The rate of dissipation of energy directly by the long-range Coulomb potential is small compared to the rate of energy dissipation by the short range potential.

(d) The agreement between experiment and theory is very satisfactory if the positive ion is Ar2+, Kr2+, or Xe2+ and it is suggested that this is the ionic species present. Agreement is much poorer if a different ionic species (say Ar+) is postulated.

(e) If the ions are regarded as probes to alter and study the liquid structure it can be deduced that the current theory of liquids seriously miscalculates the change in the equilibrium pair correlation as a function of temperature and pressure. We believe the error to arise from either a premature truncation of a slowly convergent series used in the solution to an integral equation or, at worst, that the assumed series expansion is invalid [T. L. Hill, Statistical Mechanics (McGraw-Hill Book Company, Inc., New York, 1956)].
Exchange of Interacting Nuclear Spins in Nuclear Magnetic Resonance. I. Intramolecular Exchange
Authors: Alexander S.
Published: January 2005

The effect of internal-exchange processes in a molecule on high-resolution nuclear magnetic resonance spectra is investigated. A Boltzmann equation governing the behavior of the nuclear spin density matrix is derived. This equation is valid for arbitrary coupling strengths and exchange rates. The methods of solving this equation are discussed and, in particular, it is shown that the calculation of the steady-state (slow-passage) NMR spectrum can be reduced to the solution of a set of simultaneous linear algebraic equations. Explicit approximation formulas for the slow- and fast-exchange limits are derived and a number of examples discussed in detail.
Transport of Solid through the Gas Phase Using a Single Heterogeneous Equilibrium
Authors: Lever R. F.
Published: January 2005

A model is developed for one-dimensional steady-state diffusion-limited transport of solid between source and seed planes in the presence of a known chemical equilibrium. The transport depends on the reaction enthalpy, the separation and temperature difference between source and seed, and the departure from equilibrium at the crystal surfaces. A simple expression gives the dependence of transport on the gaseous binary diffusion coefficients, the reaction coefficients, and mean partial pressures of the various species present.
Spectral Solvent Shift. II. Interactions of Variously Substituted Hydrocarbons with Polynuclear Aromatic Hydrocarbons
Authors: Weigang O. E. , Wild D. D.
Published: January 2005

Nine electronic transitions in the chromophores naphthalene, azulene, and phenanthrene have been observed in 21 chlorinated hydrocarbons and chlorocarbons. The results support an interpretation of spectral shifts which considers interbond potentials between solvent and chromophore, involving bond polarizabilities and dipole moments. The results are generally in accord with the McRae solvent-shift theory. Exceptional behaviors of some of the transitions in azulene are attributable to changes in the magnitude of static dipole moment on excitation.

The 1La transition of naphthacene has been observed in some 64 substituted hydrocarbons, the substituents ranging over nine groups. The results are also interpreted by a statistical theory using interbond (or intergroup) potentials. They are compared to the McRae theory, especially with respect to variation of the weighted mean wavelength parameter L0 and the quadratic Stark effect. The effect of the latter seems considerable while no effect of the former can be detected.
Molecular-Orbital Study of the Geometry of HO2
Authors: Boyd Marjorie E.
Published: January 2005

Determination of the energy of HO2 as a function of the HO1O2 angle for fixed values of R(H–O1) and R(H–O2) has been carried out using LCAO—MO—SCF calculations on closed-shell ions. All one-electron and one- and two-center two-electron integrals used were evaluated accurately while three-center integrals were approximated. An isosceles-triangle configuration is favored by these calculations and gives a value of the ionization potential of 9.5 eV and dissociation energy of 4.4 eV, consonant with experimental results. Approximation by means of ionic calculations used here is shown to be valid for the purposes of this discussion.
Electron Spin Resonance of a γ-Irradiated Single Crystal of Trifluoroacetamide
Authors: Lontz Robert J. , Gordy Walter
Published: January 2005

Electron spin resonance measurements made on γ-irradiated single crystals of CF3CONH2 show that the irradiation breaks a CF bond to leave the detectable free radical CF2CONH2. Although the structure of the crystal is unknown, its form is approximately monoclinic. The present study indicates that there are two molecules in the unit cell. The free radicals formed from these appear to be planar with their planes parallel to the two crystal faces, ac and bc, which have relative orientations of 68°. Nuclear couplings of the two F atoms of the free radical are equivalent and are symmetric about an axis perpendicular to the plane of the free radical with principal elements parallel and perpendicular to the symmetry axis: A∥ = 178 G, A‖ = 24 G. The elements of g are also axially symmetric, and their principal axes have the same direction as those of A, with g∥ = 2.0025±0.0010 and g‖ = 2.0045±0.0010. It is concluded that the electron spin density is in a π orbital perpendicular to the plane of the free radical with approximately 11% of the density in a p orbital of each of the F atoms. The isotropic component in the F19 coupling can be attributed to spin polarization of the σ CF bonds, if it is assumed that the bonding orbital of the F has about 33% s character. Off-diagonal terms in the nuclear coupling give rise to satellite components which for some orientations at 24 kMc/sec are one-fifth as strong as the principal lines.
Crystal Structure of Copper Ammonium Oxalate Dihydrate, Cu(NH4)2(C2O4)2·2H2O
Authors: Viswamitra M. A.
Published: January 2005

The crystal structure of copper ammonium oxalate dihydrate (space group P1̄) has been derived from a refinement of the two-dimensional (hk0) and (0kl) x-ray data using the atomic coordinates of the isomorphous salt CuK2(C2O4)2·2H2O as the starting point of the analysis. In contrast to the chromium complexes of oxalic acid the C–C bonds in both the two nonequivalent oxalate ions in the unit cell are single bonds (1.58 and 1.61 Å) consistent with the conclusion of Jeffrey and Parry that the carboxyl groups of the oxalate ion are separated by a pure σ bond with little or no π conjugation across the molecule. Both the oxalate ions are slightly nonplanar. The copper ions occupy the special positions (0, 0, 0) and 0, ½, 0) and their coordination is of the distorted octahedral type with four nearest oxygen neighbors (≈2 Å) at the corners of a square and two more distant atoms along the octahedral bond direction. The environment of the NH4+ ions consists of eight nearest oxygen atoms at a mean distance of 3 Å.
Approximating Two-Electron Atomic Energies Using Scaled Eigenfunctions : Semiempirical Coulomb-Repulsion Integrals
Authors: Ellison Frank O.
Published: January 2005

If all electron coordinates in an exact atomic eigenfunction are multiplied by a scaling factor, the kinetic, potential and total energies are modified. Exact equations are derived for these changes. The one-electron energy for a two-electron atom is approximated using scaled one-electron eigenfunctions leading to a semiempirical estimate of the (1s1s:1s1s) Coulomb-repulsion integral. Finally, two-electron atomic energies are approximated using scaled eigenfunctions for the corresponding one-electron atom and a two-electron atom of different nuclear charge.
Sedimentation Constants of Broken Chains and Wormlike Coils
Authors: Hearst John E. , Stockmayer Walter H.
Published: January 2005

The sedimentation constant of two stiff-chain models has been calculated by the method of Kirkwood. The broken chain consists of straight rigid segments of equal length connected by universal joints. The wormlike chain is that described by Kratky and Porod. In the limit of large contour length, both models have the same slope in a plot of S against n½, where n is the number of straight segments in the one case and the number of Kuhn statistical lengths in the other. The intercept of this plot at n=0 is sensitive to the model chosen as well as to the chain diameter and the statistical segment length.
Classification of Rotational Energy Levels for Symmetric-Top Molecules
Authors: Hougen Jon T.
Published: January 2005

It is shown that the rotational energy levels of a symmetric-top molecule can be classified according to symmetry species of the full symmetry group of the molecule. Useful selection rules for electric-dipole transitions between rotational energy levels thus classified are presented. It is shown that the rotational energy levels can be labeled in addition by a convenient quantum number G, which is essentially a generalization of the +l, —l labels. Selection rules for this quantum number are presented, which, together with those for the symmetry species, allow one to determine easily the allowed branches for a transition between any two vibronic states in a symmetric-top molecule.
Application of Configuration Interaction to the 23S State of Helium
Authors: Davis H. L.
Published: January 2005

The method of configuration interaction is applied to the 23S state of the helium atom. The final set of 80 configurations gives an energy of —2.1752246 a.u. for this state without complete optimization of all the variational parameters. This value is to be compared with Pekeris' extrapolated value of —2.1752294 and his 125 function basis value of —2.1752210. Thus, it is concluded that hope still exists to obtain wave functions by the configuration interation method which would compare favorably with Pekeris' extrapolated values.
Reactions of Hydrogen Atoms with Hydrazine, Ammonia, and Nitrous Oxide
Authors: Schiavello M. , Volpi G. G.
Published: January 2005

Reactions of hydrogen atoms with hydrazine, ammonia, and nitrous oxide have been investigated in a flow system employing a mass spectrometer for the measurements of the steady-state concentrations of the gases. It is shown that reaction with hydrazine proceeds through the mechanism: N2H4+H=H2+N2H3,k1=3.5×1011e−2000/RTmole−1cc sec−1;2N2H3=2NH3+N2,k2⩾3×1012 mole−1cc sec−1 (at 150∘C).The mechanism of the reactions of hydrogen atoms with ammonia or nitrous oxide was not elucidated but the rate of the processes H+NH3 and H+N2O can be estimated to be about 107 mole—1cc sec—1 at 150°C.
Effect of Weak Coupling on the Absorption Spectrum of an Aggregate of Chromophores
Authors: DeVoe Howard
Published: January 2005

A theory is developed for the absorption spectrum of chromophores in a molecular aggregate with weak coupling in which they interact through their vibronic transition moments while vibrating independently. The change upon aggregation of the oscillator strength of a vibronic line, due to interaction with other vibronic lines of the same electronic band or other bands, is treated by first-order perturbation theory. Equations are derived which relate the aggregate extinction coefficient of a band, as a function of wave-number, to the monomer chromophore spectra and certain factors for the interaction of electronic transition moments in the aggregate. The interaction of degenerate electronic transition moments can be evaluated from the experimental monomer and aggregate spectra, and used in cases of simple aggregate geometry to determine whether weak coupling applies to the aggregate. The effects of weak coupling upon the shapes and oscillator strengths of bands are illustrated by an example which shows that weak coupling of two overlapping bands in the spectrum of a planar dye molecule may explain the hypsochromic shift of the wave-number of maximum absorption observed upon aggregation of the dye.
Stable Steady State and the Thermokinetic Potential
Authors: Li James C. M.
Published: January 2005

The mathematical postulate of Carathéodory for the existence of the entropy function is shown to be a direct consequence of the physical postulate of the existence of a stable equilibrium state for any given set of state variables. Similarly, the existence of thermokinetic potential is shown to be a direct consequence of the physical postulate of the existence of a stable steady state for any given set of nonequilibrium state variables.
Isotopic Hydrogen-Ion—Molecule Reactions
Authors: Reuben B. G. , Friedman L.
Published: January 2005

The reactions of isotopic hydrogen-molecule ions with isotopic hydrogen molecules have been investigated using a mass spectrometer ion source as the reaction chamber. No significant differences were detected in a study of the velocity distributions of the product and reactant ions. Rate constants for the formation of H3+, D3+, and H2D++D2H+ were obtained from the reactions of H2+–H2, D2+—D2, and HD+—HD, respectively, which were in excellent agreement with theory. Isotopic fractionation was observed in the production of H2D+ and D2H+ from mixtures of H2 and D2, HD and H2, HD and D2. The isotope effects are qualitatively consistent with a more rapid formation of lower zero-point energy intermediates.
Mass Spectrometric Studies of Metastable Nitrogen Atoms and Molecules in Active Nitrogen
Authors: Foner S. N. , Hudson R. L.
Published: January 2005

Metastable nitrogen atoms and molecules produced by electrical discharges in N2 and He–N2 mixtures have been studied by mass spectrometry. N(2D) and N(2P) atoms in addition to ground-state N(4S) atoms were clearly identified in the products observed about 1 msec after leaving the discharge. The concentration of metastables was much higher for a discharge in a He–N2 mixture than for a discharge in pure N2. Assuming that the ionization cross sections for the atoms at corresponding excess energies were equal, the relative concentrations were: N(4S) = 1.00, N(2D) = 0.17, and N(2P) = 0.06 for the He–N2 discharge; and N(4S) = 1.00, N(2D) = 0.0068, and N(2P) = 0.0025 for the pure-N2 discharge. Metastable N2 molecules with excitation energies of up to several eV were also observed. Ionization processes involving the metastable molecules are discussed. To explain the experimentally obtained N2 ionization curves, it was found necessary to assume that, in addition to vibrationally excited ground-state molecules, an appreciable concentration of N2 molecules in various vibrational levels of the metastable A3Σu+ state were present. Metastable N atoms are very easily deactivated by wall collisions. Metastable molecules survive for longer times, indicating that they are less readily destroyed by wall collisions.
Influence of Vibrations on Molecular Structure Determinations. II. Average Structures Derived from Spectroscopic Data
Authors: Laurie Victor W. , Herschbach Dudley R.
Published: January 2005

Formulas are given which enable structural parameters for the average molecular configuration in the ground vibrational state to be calculated for some simple types of molecules. The data required are the observed effective moments of inertia and harmonic force constants. No knowledge of anharmonic constants is necessary. The average structural parameters have a well-defined physical meaning and are directly comparable with diffraction results. Polyatomic molecules for which explicit calculations are given are CO2, CS2, H2O, SO2, O3, NO2, CH4, HCN, and C2H2. It is found that the average bond lengths involving H are usually 0.003–0.005 Å longer than the corresponding D bond. For bonds involving heavier elements isotopic differences are smaller but nonetheless significant. Implications of the results for the general problem of structural determination are discussed.
Dielectric Relaxation in Associated Liquids
Authors: McDuffie G. E. , Litovitz T. A.
Published: January 2005

The dielectric properties of the associated liquids butanediol 1,3, 2-methyl pentanediol 2,4, glycerol, and hexanetriol 1,2,6 have been measured over the temperature range —20° to +10°C, and over a frequency range of 0.01 to 1200 Mc/sec. Dielectric relaxation times and their distributions have been determined and indicate the following: (a) All four liquids exhibit an asymmetric distribution of relaxation times of the Davidson—Cole form. (b) With the exception of hexanetriol 1,2,6, the distribution of relaxation times becomes narrower with increasing temperature. It is proposed that groups (regions of appreciable order) exist in these liquids, and that dielectric orientation is closely related to the structural breakup of these groups, this breakup being a necessary condition for dipole reorientation. It is further proposed that the structural breakup is a cooperative process which does not proceed exponentially, therefore giving rise to a nonexponential decay of dielectric polarization. This concept offers an explanation for the observed distribution of relaxation times. The temperature dependence of the width of the distribution is explained by assuming that the group-size decreases with increasing temperature, and that as the groups become smaller, the structural-decay process becomes more exponential.
Effect of Added Quenchers in Organic Scintillator Solutions: Aromatic Halides
Authors: Kropp John L. , Burton Milton
Published: January 2005

Luminescence-intensity measurements, as affected by quencher concentration, solvent and scintillator, yield information on quenching constants, on specific rates of quenching, on mechanism of quenching, on contrast between quenching of solvent and quenching of scintillator, and on contrast between quenching in benzene as solvent and quenching in cyclohexane as solvent. For a number of aromatic bromides (and for iodobenzene), excitation transfer appears to be involved in the quenching process; in those cases the specific rates are higher than may be expected for simple diffusion-controlled reactions. Typical specific rates (kq) are ≃ or >2.5×1010 M—1 sec—1 in benzene. The donor states from which excitation is transferred are not identified. In cyclohexane, calculated kq values are very much higher with an implication that the mechanism of the quenching process is quite different in such cases. Some of the results can be explained in terms of the theory of solvent domains; the data for cyclohexane suggest that the mechanism of deposition and localization of energy must also be carefully considered.
Theory of Torsion Vibrations of (CH3)2X-Type Molecules
Authors: Möller K. D. , Andresen H. G.
Published: January 2005

The torsion vibrations of (CH3)2X-type molecules having C2v and Cs point-group symmetry were analyzed by using a Hamiltonian that includes top—top interaction terms. The energy levels were calculated by first-order perturbation methods and the selection rules for the infrared-active transitions were analyzed by group theoretical arguments. Explicit expressions which have been derived for the high potential-barrier approximation were used to discuss the torsion vibration spectrum of the (CH3)2S molecule.
External Heavy-Atom Spin-Orbital Coupling Effect. I. The Nature of the Interaction
Authors: McGlynn S. P. , Sunseri R. , Christodouleas N.
Published: January 2005

The effect of external heavy-atom spin-orbital coupling perturbation has been studied in the lowest energy triplet←singlet absorption spectrum of various 1-halonaphthalenes in 1:1 molar 1-halonaphthalene: alkyl halide binary solutions. It is shown that the interaction prerequisite to the charge transfer which must occur in these systems is probably of a donor—acceptor nature, the alkyl halide functioning as the acceptor and the 1-halonaphthalene functioning as the donor. Steric effects are estimated using molar refraction data and are undoubtedly of importance, particularly when the alkyl halide contains more than one halogen atom.

The external heavy-atom effect is spin-orbital coupling in nature as may readily be seen by comparison of the enhancements induced in the T←S absorption of the 1-halonaphthalene by various alkyl halides; the order of enhancement is alkyl iodide>alkyl bromide>alkyl chloride and follows roughly the order of the atomic spin-orbital coupling factors squared. The external heavy-atom effect is greater the larger the internal heavy-atom effect, as is shown both experimentally and theoretically. In fact, an external bromine is more effective than an internal fluorine, while an external iodine is more effective than an internal chlorine, and roughly comparable in enhancement ability to an internal bromine. Simple theoretical considerations enable one to deduce the singlet—triplet mixing coefficients for both the external and internal effects, and to validate the spin-orbital coupling nature of the effect.
Mass-Spectrometric Study of the Magnesium Halides
Authors: Berkowitz J. , Marquart J. R.
Published: January 2005

The vapor composition of the four magnesium halides has been studied by mass analyzing the vapor effusing from a Knudsen cell. In each instance, ∼1% dimer and 0.01% trimer were observed. Heats of sublimation have been measured by second- and third-law methods. The discrepancy between the two methods varies from 2 kcal/mole for MgI2 to 5 kcal/mole for MgF2, with the third-law method giving consistently lower values. The experimental heats of ionization of the monomers are in fair agreement with calculations based on an ionic model. The fragmentation pattern of the fluoride is anomalous as it is with the alkali-halide systems. The measured relative ionization cross sections are in surprisingly good agreement with the relative electric polarizabilities of the anions.
Yield and Reactivity of Electrons and H Atoms in Irradiated Aqueous Solutions
Authors: Rabani Joseph , Stein Gabriel
Published: January 2005

Using specific scavengers of solvated electrons eaq—, and of atomic hydrogen H in aqueous solutions irradiated with x rays, evidence is obtained that the hydrogen yield Ghydrogen=3.7±0.1 between pH 2–4. It is shown that this yield corresponds to the sum of the yields of molecular hydrogen GH2=0.5, the primary yield of atomic hydrogen GH=0.55 and yield of solvated electrons Geaq—=2.65. Evidence is obtained showing that H atoms formed as such (GH=0.55) appear in the bulk of the solution even at neutral pH. The velocity constants of the reactions of H atoms with acetate, isopropanol, glucose, glycerol, and nitrite were obtained. The reactivity of eaq— with Haq+, acetone and ferricyanide was studied and relative velocity constants obtained. An upper limit, keaq—+H2O≤103 liter mole—1 sec—1 is found for the reaction of eaq— with water to yield hydrogen.
Szilard—Chalmers Chemistry and Radiation Chemistry of Solid Hexabromoethane. Thermal Annealing and Radiation Annealing Effects
Authors: Collins Kenneth E. , Willard John E.
Published: January 2005

The effects of ionizing radiation and thermal treatment on the chemical fate of Br82 atoms produced in solid C2Br6 by the Br81 (n,γ)Br82 process have been investigated. Three chemically distinguishable forms of Br82 are found, using two methods of analysis. One method involves determination of the fraction of the Br82 which is extractable into aqueous solution when the irradiated C2Br6 is dissolved in CS2 and the other involves dissolution in liquid Br2 followed by evaporation of the solvent. The ``aqueous yield'' of Br82 in C2Br6 irradiated with neutrons at —196° and analyzed at 0° under the conditions of these investigations is 34%. This is lowered to about 24% by heating to 100° for an hour prior to analysis. Exposure of the crystals to 1020 eV g—1 of Co60 gamma radiation at —196° either before or after neutron irradiation does not affect the yield if analysis is made without thermal annealing but lowers it to 3.5% for samples annealed 1 h at 100°. Analyses of thermal annealing curves at several gamma doses and several temperatures indicate the existence of several processes by which gamma defects and Br82-containing defects are annealed. G(Br2) from the radiolysis of C2Br6 is reduced by thermal annealing in a manner having similarity to the annealing of Br82. Implications of the data are discussed.
Sedimentation in Chemically Reacting Systems. II. Numerical Calculations for Dimerization
Authors: Belford Geneva G. , Belford R. Linn
Published: January 2005

Results are given for some numerical calculations, carried out on a high-speed computer, for a simple model of sedimentation with concurrent dimerization. These results show that in a simple, dimerizing system anywhere from one to three concentration-gradient peaks may be simultaneously observable. The numerical techniques used involved some interesting aspects in themselves and are therefore discussed briefly. Finally, a simple analytic expression for theoretical concentration-gradient peak decay rates is presented.
Nature of the Visible Charge-Transfer Bands of K3Fe(CN)6
Authors: Basu Gobinda , Belford R. Linn
Published: January 2005

The temperature dependence of the 20–28 kK optical absorption in K3Fe(CN)6 crystal is negligible below room temperature. The inference is made that this charge-transfer absorption is electronically allowed (u←g). An alternate interpretation of Naiman that the band is of (g←g) type and thus activated by vibrations is not disproven, but it is restricted such that very stiff modes—i.e., those involving CN stretching— would have to be the only effective vibrational promoters. Arguments are made against this possibility.
Chemisorption of Oxygen on Ordered Tungsten Surfaces
Authors: George T. H. , Stier P. M.
Published: January 2005

Chemisorption of oxygen on highly ordered and relatively disordered tungsten surfaces at substrate temperatures of 20° and 300°K has been studied in the field-emission microscope. Evidence is presented for the chemisorption of a monolayer of gas with a sticking coefficient of unity and the adsorption of a second, initially mobile layer of oxygen, also with a sticking coefficient of unity when the substrate temperature is 20°K. These results are independent of the degree of surface order over the range considered. The second adsorbed layer is not observed at substrate temperatures of 300°K, and use of the Langmuir postulate that only the clean surface contributes to the adsorption allows the definition of a constant sticking coefficient of 0.8 for oxygen on tungsten at 300°K. Variations in the dipole moment per adatom with crystallographic orientation are also reported.
Molecular Friction in Dilute Gases. III. Rotational Relaxation in Polyatomic Fluids
Authors: Sather Norman F. , Dahler John S.
Published: January 2005

Formulas are derived for the rotational relaxation times of gases composed of molecules interacting with square well potentials with rough spherical and spherocylindrical cores. The temperature dependence of the relaxation times is discussed and compared with previous theoretical results.
Photolysis of the Phenoxy Radical in a Nitrogen Matrix
Authors: Roebber John L.
Published: January 2005

The photolysis of the phenoxy radical trapped in solid nitrogen at 4.2°K is studied by use of infrared and visible-ultraviolet absorption spectroscopy. The trapped phenoxy radicals are produced by the photolysis of a parent compound (phenol, anisole, or phenetole) suspended in the solid nitrogen. When light not absorbed by the parent compound is used to decompose the trapped phenoxy radical, product bands grow at 4.68 μ, 4.72 μ, and 2600 Å. The 4.68-μ band has been assigned to carbon monoxide. The 4.72-μ and 2600-Å bands are probably due to trapped 6-oxo-1,3,5-hexatrienyl-1 radicals. The mechanism proposed to account for these products is that absorption of a light quantum by a phenoxy radical breaks the bond between the 1 and 2 ring carbon atoms to produce an excited 6-oxo-1,3,5-hexatrienyl-1 radical. This excited radical may either decompose to yield carbon monoxide or be deactivated and trapped.
Velocity Dependence of the Differential Cross Sections for the Scattering of Atomic Beams of K and Cs by Hg
Authors: Morse Fred A. , Bernstein Richard B.
Published: January 2005

Measurements of the velocity dependence of the angular intensity distribution of potassium and cesium beams scattered by a crossed beam of mercury are presented. The alkali beam was velocity selected, with a triangular velocity distribution (half-intensity width 4.7% of peak velocity); the velocity was varied over the range 185–1000 m/sec. The Hg beam had a thermal distribution; the average Hg speed was ∼235 meters per second. The scattering data have been converted to the center-of-mass system. The angular distributions show the expected strong forward scattering and evidence the phenomenon of rainbow scattering. The energy dependence of the rainbow angle is used to evaluate the interatomic potential well depth, interpreted as the dissociation energy De of the 2Σ+ molecular ground state. Values (in erg×1014) thus obtained (±5%) are 7.46 for KHg and 7.72 for CsHg. Absolute values of differential cross sections could not be obtained; only relative cross sections D(θ) are reported. The observed low-angle behavior D(θ) ∝θ- 7/3 serves as direct experimental confirmation of the r—6 dependence of the long-range attractive potential for K–Hg and Cs–Hg systems.