bluuebunny/crossref_metadata_2025 huggingface dataset:
Intermolecular Potential Functions and the Second and Third Virial Coefficients
Authors: Sherwood A. E. , Prausnitz J. M.
Published: January 2005

Potential parameters are determined from second virial coefficient data for the Lennard-Jones, Kihara, square-well, exp-6, and Sutherland potentials. Using these parameters, third virial coefficients are calculated from theoretical tabulations and compared with experimental values. Substances considered are: Ar, N2, Kr, CH4, CO2, Xe, CF4, n-pentane, neopentane, and benzene. For the exp-6 potential, theoretical second virial coefficients are tabulated for the additional third parameter values necessary to represent the experimental data. Each of the three-parameter models, including the square-well, fit the second virial coefficient data within experimental accuracy, and considerably better than the two-parameter potentials. Calculated third virial coefficients form a characteristic family of curves for the various potential models. The contribution of nonadditive attractive forces to the third virial coefficient is significant, especially at low temperatures. The three-parameter potentials give reasonable agreement with experiment but no single potential is outstanding, possibly due to the neglect of nonadditive repulsive forces.
Force Constants and Normal Vibrations of the Propargyl Halides
Authors: Zerbi Giuseppe , Gussoni Mariangela
Published: January 2005

Several modifications of a Urey—Bradley field combined with a valence force field have been used for the calculation of the normal coordinates of the propargyl halides CH2X–C≡C–H (X=F, Cl, Br, I). The force constants obtained by a least-squares method have been compared in terms of the structural changes introduced by the halogen atom. A kinetic effect seems to account for the splitting of the –C≡C–H in-plane and out-of-plane bending modes.
Infrared Spectra of the Lithium Halide Monomers and Dimers in Inert Matrices at Low Temperature
Authors: Schlick S. , Schnepp O.
Published: January 2005

The infrared absorption spectra of lithium fluoride, chloride, and bromide vaporization products have been investigated between 2–37 μ in solid argon, krypton, xenon, and nitrogen matrices at liquid-hydrogen and liquid-helium temperatures. Both the natural lithium salts containing 93% 7Li and 6Li salts as well as equimolar isotopic mixtures were studied. The solvent shifts of the monomers were found to confirm the isotopic invariance of the ratio Δω/ω as predicted by Buckingham. Serious deviations from the Kirkwood—Bauer—Magat relation were, however, observed. These shifts have also been discussed in terms of specific solute—solvent interactions. Two dimer vibrational frequencies were definitely characterized by means of isotopic substitutions and these frequencies were assigned. They represent in-plane stretching modes of the planar rhombus, the higher energy vibration being of symmetry b3u (X—X axis polarized) and the lower energy vibration b2u, (Li–Li axis polarized).
Approximate Series Solutions of Nonseparable Schrödinger Equations. II. General Three-Particle System with Coulomb Interaction
Authors: Frost Arthur A. , Inokuti Mitio , Lowe John P.
Published: January 2005

The series solution method developed by Pekeris for the Schrödinger wave equation of two-electron atoms has been generalized to handle any three particles with Coulomb interaction. Calculations have been carried out with wavefunctions through the sixth degree which result in a linear combination of 84 terms for the unsymmetrical case. Systems for which numerical results are given are: the hydride ion with nuclear motion, the trielectron (e+e—e—) or positronium ion, the positron—hydrogen atom interaction (e+e—p+), and the mu-mesonic isotopic hydrogen molecule-ion (p+μ—d+).
Gaussian Wavefunctions for the 10-Electron Systems. I. Neon
Authors: Harrison Malcolm C.
Published: January 2005

Results of LCAO—MO—SCF calculations on neon are presented, using Gaussian AO's. Approximate optimum exponents are obtained for several different basis sizes.
Gaussian Wavefunctions for the 10-Electron Systems. II. Hydrogen Fluoride
Authors: Harrison Malcolm C.
Published: January 2005

SCF calculations on hydrogen fluoride are presented for four different bases of Gaussian functions. The results suggest that a Gaussian 58+3p basis may prove superior to a minimal STO basis in many respects, though giving a slightly worse total energy. For more accurate calculations, a Gaussian basis rather less than twice as large as the STO basis should give comparable results. Computationally, this implies that for larger diatomic and all polyatomic calculations, a Gaussian basis is to be preferred for many applications.
One-Electron Perturbations in Self-Consistent Field Theory
Authors: Wyatt Robert E. , Parr Robert G.
Published: January 2005

Self-consistent field equations perturbed by one-electron operators are examined, with the aim of justifying the use of uncoupled equations at the first-order level. The independent-orbital equations of Sternheimer for the first-order corrections are shown to differ from the exact first-order SCF equations by sums of pair-coupling functions Aij which bring perturbed orbital j into the differential equation determining the perturbed orbital i. It is shown that the off-diagonal Lagrangian multipliers εij0 and εij(1) that appear in the unperturbed and perturbed SCF equations can be chosen so that ∫ φi0Aijdv= ∫ φj0Ajidv=0and ∫ (Aij2+Aji2) dv=minimum,where the φi0 are the unperturbed SCF orbitals. Complete neglect of the functions Aij—the Sternheimer method—is thereby given a firm basis. Further analysis provides a perturbation—iteration method for determining residual coupling effects.

An alternative analysis also is presented in which the Sternheimer equations are obtained directly from the perturbed SCF equations by treatment of the exchange operator, the change of the Coulomb-exchange operator, and the operator generating the off-diagonal εij as pseudoperturbations that act cojointly with the pure-field operator. Integrodifferential equations are given for both the pure-field corrections and the corrections evolved by the pseudoperturbations.
Interaction between Chlorophyll a and Fatty Alcohol Molecules in Mixed Monomolecular Films
Authors: Gaines G. L. , Bellamy W. D. , Tweet A. G.
Published: January 2005

Chlorophyll a and oleyl alcohol form nearly ideal two-dimensional solutions, up to chlorophyll mole fraction of at least 0.2. Chlorophyll is essentially insoluble, however, in stearyl alcohol monolayers at room temperature. Measurements of collapse pressure, area, absorption spectrum, and fluorescence spectrum of the monolayers confirm these conclusions. The fluorescence and absorption spectra of concentrated and diluted (in oleyl alcohol) chlorophyll films are compared. Measurable shifts in both absorption and emission demonstrate that chromophore—chromophore interactions are detectable in monolayers containing high chlorophyll concentrations.
Infrared Spectrum and Structure of Gaseous Al2O
Authors: Linevsky Milton J. , White David , Mann D. E.
Published: January 2005

The infrared absorption spectrum of Al2O trapped in solid argon and krypton matrices has been observed. It is possible from the observed spectra and isotope shifts for Al216O and Al218O to conclude that the molecular symmetry of Al2O is C2v and that the Al–O–Al angle is probably not far from 145°. Force constants and the bending frequency v2 have been calculated. Reanalysis of the ultraviolet spectra of exploding aluminum wires provides additional support both for the bent structure and for the calculated value of v2. The Al–O bond distance is estimated to be 1.66 Å. The three fundamental frequencies for Al216O in an argon matrix are (in cm—1): v1 = 715, v2 = [238]; v3 = 994.
Intermolecular Quenching of Higher Excited States
Authors: Murty N. R. , Rabinowitch E.
Published: January 2005

The influence of β carotene on the fluorescence yield of chlorophyll a in 3-methoxy- 1-butanol is investigated. β carotene does not affect the fluorescence yield when chlorophyll a is excited in the red absorption band at 660 nm. However, a quenching of the red fluorescence of chlorophyll a is observed when excited at 415 nm. This is suggested to be due to a quenching of the second excited state of chlorophyll a by β carotene.
Separation of Sets of Variables in Quantum Mechanics
Authors: Marcus R. A.
Published: January 2005

Separation of the Schrödinger equation for molecular dynamics into sets of variables can sometimes be performed when separation into individual variables is neither possible nor for certain purposes necesary. Sufficient conditions for such a separation are derived. They are the same as those found by Stäckel for the corresponding Hamilton—Jacobi problem, with an additional one which is the analog of the Robertson condition for one-dimensional sets.

Expressions are also derived for operators whose eigenvalues are the separation constants. They provide a variational property for these constants. For use in aperiodic problems an expression is obtained for the probability current in curvilinear coordinates in an invariant form. Application of these results to reaction rate theory is made elsewhere.
Local Approximation of Potential-Energy Surfaces by Surfaces Permitting Separation of Variables
Authors: Marcus R. A.
Published: January 2005

In the immediate vicinity of a potential-energy minimum or of a saddle point, it is shown that major topographical features of a ``nonseparable'' potential-energy surface can be imitated by those of a surface permitting separation of variables. For each extremal path of descent or ascent to the cited critical point of the surface, there is an exact match of the tangent, the first curvature vector in configuration space, and the force constant along that path provided that the known curvature vector satisfies an equation containing the metric tensor of the selected coordinate system and known force constants. Because of the wide choice of coordinate systems available for selection, it is anticipated that this relation may be fulfilled for each extremal path, partly by choice of the coordinate system and partly by subsequent choice of the curvilinear coordinates of the critical point.

There are several possible applications of this local approximation, including those to problems involving anharmonic coupling of normal modes and those involving n-dimensional tunneling and other calculations in reaction-rate theory. Use will be made of the formalism to extend the activated complex theory in chemical kinetics. As a preliminary test of the local-approximation concept, literature data on n- and one-dimensional tunneling rates are compared. They are found to be fairly similar when proper cognizance is taken of zero-point energies.
Hole Photoconductivity in Ferrocene, Triphenylamine, and Trans-Stilbene
Authors: Hoesterey D. C. , Letson G. M.
Published: January 2005

The drift mobility of holes in single crystals of ferrocene, triphenylamine, and trans-stilbene has been measured by the method of transient photoconductivity. At 20°C the mobilities are: ferrocene, 2.2×10—2 cm2/V·sec; triphenylamine, 2×10—2 cm2/V·sec; and trans-stilbene, 2.4 cm2/V·sec. In trans-stilbene, the hole mobility decreases slightly with increasing temperature in the range of 100° to —50°C. In ferrocene and triphenylamine, the mobility increases with increasing temperature, but not in a manner that suggests hole motion by a thermally activated, hopping-type motion. The photoconductive excitation spectra in these solids follow the optical absorption of the exciton states built from the π and π* states of the molecules.
Ionization-Efficiency Curves for Molecular and Fragment Ions from Methane and the Methyl Halides
Authors: Tsuda S. , Melton C. E. , Hamill W. H.
Published: January 2005

The retarding potential difference method has been used to measure ionization efficiency curves of CH3X+ (X=H, F, Cl, Br, I), CH3+, and X+ from methane and the methyl halides in a time-of-flight mass spectrometer. Discontinuities between linear segments of the ionization efficiency curves are interpreted as appearance potentials (A.P.) of electronic states or processes. For all CH3+, A.P.'s occur at 1.1, 1.7, 2.7, and about 3.4 eV above onset in the ion pair region. Empirical knowledge of this structure makes it possible to identify the A.P. for the ion—neutral pair, CH3+—X, in their ground states. Combining these data and the A.P.'s for X+/CH3X gives the ionization potential for CH3 and the bond dissociation energies, D(CH3—X).
Signs of the Isotropic Hyperfine Splittings in the Electron Spin Resonance Spectrum of the Dihydropyrazine Cation Radical
Authors: Barton B. L. , Fraenkel George K.
Published: January 2005

Linewidth studies of the electron spin resonance spectrum of the dihydropyrazine cation radical have been employed to determine the signs of the isotropic hyperfine splittings. It was found that the nitrogen splitting aN is positive and the proton splitting aNHH of the protons bonded to the nitrogen atoms is negative. The sigma—pi parameter QNHH in McConnell's relation for NH bonds (aNHH=QNHHρNπ) was found to be negative.
Effect of Impurity on Excitation Migration in a Linear Chain of Molecules
Authors: Inokuti Mitio , Matsuzawa Michio
Published: January 2005

The effect of an impurity on the second moment of an exciton wave packet is studied in the case of a simple one-dinensional model of a molecular crystal with nearest-neighbor coupling. An expression is derived for the first-order correction, in the sense of perturbation theory, to the second moment and numerical evaluation is made.
Single-Crystal X-Ray Diffraction Study of β-Fluorine
Authors: Jordan Truman H. , Streib William E. , Lipscomb William N.
Published: January 2005

Three-dimensional x-ray diffraction data from a single crystal of β-F2 have yielded a crystal structure like that later found for the γ-O2 phase in which no dimers are present. The unit cell is cubic, contains eight molecules, and has a lattice dimension of a=6.67±0.07 Å. The two molecules at 000 and ½ ½ ½ are approximately spherically disordered, and the six molecules approximately at ¼ ½ 0, ¾ ½ 0, 0 ¼ ½, 0 ¾ ½, ½ 0 ¼, and ½ 0 ¾ are highly disordered, respectively, in the planes x=¼, x=¾, y=¼, y=¾, z=¼, and z=¾. The value of R=Σ ‖ Fo |−| Fc ‖/Σ | Fo | is 0.10 for the 28 observed reflections.
Electron Spin Resonance of Boron in Single—Crystal BeO
Authors: Reinberg A. R.
Published: January 2005

Single crystals of synthetic BeO which have been irradiated with 6-MeV electrons show an ESR spectrum at room temperature identified as being due to boron ions substituting for beryllium at normal lattice sites. The hyperfine tensor A is cylindrically symmetric with its principal axis pointing towards one of the near oxygen bonds. Six equivalent directions are observed corresponding to the positions of the nonaxial nearest-neighbor oxygen atoms. The constants of the spin Hamiltonian are: g∥ = 2.0035±0.0005, g⊥ = 2.0044±0.0005, A∥ = 122 Oe, A⊥ = 76.5 Oe. The spectrum is analyzed in terms of the paramagnetic electron occupying an antibonding orbital located along the direction of a B–O bond. Comparison of the observed hyperfine interaction with those expected for the free atom suggests deviations of the orbital from tetrahedral sp3 configuration to one in which the ratio of the p to s contribution increases from √3 to 2.64, implying that the B–O bond is lengthened along the direction in which the paramagnetic electron is stabilized, the bond angle decreasing from 109 to 105 deg.
Diffusion of Helium in Silicon, Germanium, and Diamond
Authors: Luther Lars C. , Moore Walter J.
Published: January 2005

The diffusion coefficients D of helium in silicon, germanium, and diamond were determined from the rate of evolution of helium upon heating boron-doped crystals after slow neutron irradiation:He in C:  DHeC=7.0×10−4exp (−23.4±4.9 kcal/RT),  1510∘<T<2470∘K;He in Si:  DHeSi=5.1×10−4exp (−13.4±1.8 kcal/RT),  740∘<T<1250∘K;He in Ge:  DHeGe=1.8×10−3exp (−14.0±1.8 kcal/RT),  800∘<T<1130∘K.The 90% confidence level for the activation energies is indicated. Experiments in which helium was introduced into silicon by ion bombardment from a discharge plasma gave values of D concordant with the above. The activation energies were calculated theoretically from the differences in interaction energies of the helium in the interstitial site and at the saddle point between two such sites. An exp-6 potential was used with parameters estimated from inert-gas interactions. The theoretical E values were C: 24.8, Si: 6.7, and Ge: 6.4 kcal. The pre-exponential factors D0 as calculated from the vibration frequencies of the interstitial helium were about 10 times higher than the observed.
Electron Spin Resonance Absorption in Recrystallized Free Radicals at Low Fields
Authors: Krishnaji  , Misra B. N.
Published: January 2005

The width and shape of the ESR lines of 1,1-diphenyl-2-picryl hydrazyl, picryl-N-amino carbazyl, and their recrystallized samples from the various solvents have been determined at different temperatures. It has been found that the ESR lines of recrystallized samples are wider than those of the original samples. The calculated linewidth on the basis of the Kubo and Tomita theory for DPPH agreed very well with the experimental value and hence this theory has been utilized to determine the asymptotic Curie temperature for all the other samples. The temperature variation of linewidth has been utilized to calculate the effective exchange frequency at different temperatures. An empirical formula has also been suggested for this type of variation.
Some Comments on the Photolysis of Saturated Hydrocarbons
Authors: Peters David
Published: January 2005

An interpretation of the photolytic decomposition of saturated hydrocarbons is suggested. A set of postulates is proposed which, together with simple molecular orbital theory, gives a rationalization of the experimental facts which is consistent with general valence theory.
Electron Spin Resonance Spectrum of the Radical Anion of 1,3-Butadiene in Liquid Ammonia
Authors: Levy Donald H. , Myers Rollie J.
Published: January 2005

The electron spin resonance spectrum of the radical anion of 1,3-butadiene has been observed by means of continuous electrolysis in liquid ammonia. The proton coupling constants were observed to be A(CH)=2.791±0.007 Oe and A(CH2)=7.617±0.005 Oe. These values give a Q(av)=20.82±0.02 Oe. The source of this low Q value is discussed together with theoretical spin densities. Simple Hückel theory predicts a spin density ratio of 2.615 which can be compared with the observed coupling constant ratio of 2.729±0.007. The predictions of Parr and Mulliken's SCF theory are much less satisfactory and give a low spin-density ratio. Electrolysis in liquid ammonia appears to be an excellent method for the generation of radical anions.
Experimental Evidence for Localized Excitons in the Spectra of Charge-Transfer Complex Molecular Crystals
Authors: Hochstrasser Robin M. , Lower S. K. , Reid C.
Published: January 2005

The polarized absorption and emission of the anthracene—TNB complex crystal are shown to provide evidence for localization of low-energy excitation in this crystal. The absorption and fluorescence polarization ratios at 300°K are very different (5.6:1 and about 15:1, ‖c: ⊥c on 110) the former being close to an oriented gas value. The latter corresponds to a charge-transfer complex more closely aligned with the c axis of the crystal. The motion of the excited molecule is in accord with the behavior of a dipole in an electric field which is nearly along the c axis. Possible ramifications of this effect in photoconductive charge-transfer complexes are discussed.

The influence of temperature on the luminescence spectrum of anthracene—TNB crystals is discussed, and apart from some artifacts due to cracking of crystals, the expected increase of emission intensity with decreasing temperature is observed.
Geminal and Vicinal Spin—Spin Coupling Constants in Substituted Metadioxanes
Authors: Delmau Jean , Barbier Claudette
Published: January 2005

A study of 1,3-substituted dioxanes gave all the coupling constants between vicinal protons. These coupling constants are interesting because the valence angle is well determined in these compounds. The studied compounds also gave the magnitude of three coupling constants between geminal protons corresponding to different positions of the CH2 group in the molecule.
Temperature Dependence of the Nuclear Quadrupole Relaxation Time T1 in Para-Dichlorobenzene under Constant Pressure
Authors: Tokuhiro Tadashi
Published: January 2005

The temperature dependence of the 35Cl quadrupole spin—lattice relaxation time T1 in para-dichlorobenzene under constant pressure has been investigated in several treatments. If the temperature dependence of torsional frequency is included in Woessner and Gutowsky's approach, the agreement of the calculated values with the experimental is quite satisfactory. From these results, it may be concluded that the quadrupole relaxation arises from the two torsional oscillations, 47 cm—1 (25°C) and 53 cm—1 (25°C), and that energy transfer takes place simultaneously between spins and lattice motions.
Crystal Structure of Potassium Fluoride Tetrahydrate
Authors: Beurskens Gezina , Jeffrey G. A.
Published: January 2005

The crystal structure of KF·4H2O has been determined by x-ray diffraction using the phase determination method of Hauptman and Karle. It is monoclinic and consists of edge and corner sharing K+(H2O)6 and F—(H2O)6 octahedra. The similarity in the cation and anion coordination gives rise to pseudo-orthorhombic symmetry. The K+···O— distances are 2.79±0.02 Å. The F···(H)O distances range from 2.71 to 2.78 Å. The O(H)···O distances which link the octahedra are 2.82 and 2.85 Å.
Line Shapes in Electron Spin Resonance Spectra
Authors: Gendell Julien , Freed Jack H. , Fraenkel George K.
Published: January 2005

The theory of the linewidths in the electron spin resonance spectra of free radicals recently developed by Freed and Fraenkel predicts that, in general, composite lines arising from a set of degenerate nuclear spin states should not be Lorentzian in shape, and that the shapes of different lines in the same spectrum should be different. The earlier theory of Kivelson predicted that all the lines should be Lorentzian. To test the differences between the two theories, experimental studies of the line shape in the spectrum of the tetracyanoethylene anion have been made in a solvent consisting of a mixture of absolute ethanol and glycerine. Different lines were found to have different shapes, and the shapes were well represented by a sum of Lorentzian-shaped components, in agreement with the newer theory. Studies of dimethylsulfoxide solutions of the p-benzosemiquinone ion were also made. The spectra obtained in this system show only small linewidth variations and, in agreement with the theory, the variations in line shape are negligible. It was also possible to demonstrate that the nitrogen hyperfine splitting aN in the tetracyanoethylene radical is positive.
Molecular Orbital Description of the Lowest Excited 1Σg+ State of H2
Authors: Kato Yoshifumi , Hayes Edward F. , Duncan A. B. F.
Published: January 2005

Further calculations on the lowest excited 1Σg+ state of H2 are reported. A lower minimum energy is found with an excited orbital centered at the midpoint of the internuclear axis than with a two-centered orbital, with coordinates measured from the two nuclei. The electron density distribution of the one-centered orbital is also more in agreement with expectations.
Exciton Impurity Level and Its Implications to Radiation Chemistry
Authors: Katsuura Kanji , Inokuti Mitio
Published: January 2005

Dipole matrix elements corresponding to transitions to exciton states and other associated quantities are calculated for a simple one-dimensional model of a molecular crystal containing an impurity. Emphasis is placed on transitions to certain exciton levels, characteristic of the presence of an impurity. Absorption of radiation energy by molecular aggregates containing an impurity is discussed in view of the results of the calculation.
Ring Inversion in Cyclohexyl Radical
Authors: Ogawa Seiji , Fessenden Richard W.
Published: January 2005

The ESR spectrum of cyclohexyl radical in solid cyclohexane has been studied, during irradiation, between —85° and 0°C. Continuous electron irradiation is necessary because diffusion and recombination of the radicals occurs in this temperature interval. The broadening of certain of the lines as the temperature is raised has been interpreted in terms of an interconversion between two forms of the radical. The change of linewidth (or alternately, peak height) with temperature corresponds to an activation energy for the interconversion of 4.9±0.5 kcal/mole. The magnitude of the barrier, though smaller than that in cyclohexane itself, suggests that the interconversion is between the two chair forms of the radical. In the calculation of correlation times from the broadening, it was necessary to develop expressions which are applicable to spectra with Gaussian lines. This treatment is verified by the agreement of the data for C6H11· and C6D11·.
Elastic and Reactive Scattering of K by HCl and HI in Crossed Molecular Beams
Authors: Ackerman M. , Greene E. F. , Moursund A. L. , Ross J.
Published: January 2005

The elastic and reactive scattering of K by HCl and HI has been measured at several relative energies in experiments with crossed molecular beams. The interpretation follows that presented previously for K+HBr, with some improvements. For both systems the measurements on K show rainbow scattering, and from it parameters have been calculated for the exp-six potential. From the elastic scattering at large angles and a two-body model for it, the probability of reaction is deduced as a function of the potential energy at the distance of closest approach of the reactants.

For K+HCl the potential parameters are ε=0.45±0.02 kcal/mole and rm=3.2±0.3 Å for α=12 (assumed). The activation energy is 0.55±0.1 kcal/mole, as determined from the threshold of the probability of reaction, and is probably just the change in zero-point energy for this endothermic reaction. There are indications that the probability of reaction increases when the potential energy is sufficient for the product KCl to be formed in excited vibrational states. The application of the two-body model at the thresholds of formation of KCl allows another determination of rm which is in good agreement with the value obtained from the rainbow scattering. The total reaction cross section as obtained from the probability of reaction is 3.9 Å2 at Ē=2 kcal/mole. No measurements could be made on KCl.

For K+HI the potential parameters are ε=0.67±0.02 kcal/mole and rm=4.2±0.2 Å for α=12 (assumed). The activation energy of this exothermic reaction is 0.2±0.1 kcal/mole as determined from the threshold of the probability of reaction. The total reaction cross section as a function of relative energy has been obtained from measurements on KI and from the probability of reaction deduced from the elastic scattering. These two measures of the amount of KI produced agree within a factor of 2, which is the reproducibility of the measurements on KI. At a relative energy of 2 kcal/mole the total reaction cross section is 28 Å2.
Laser Phenomena in Europium Chelates. IV. Characteristics of the Europium Benzoylacetonate Laser
Authors: Lempicki A. , Samelson H. , Brecher C.
Published: January 2005

The properties of the europium benzoylacetonate laser are described in detail. The effect of an extremely high absorption constant is demonstrated by comparing outputs obtained from cells 0.47 cm and 0.10 cm in diameter. The outputs are quite different as revealed by a study of far- and near-field patterns, relaxation oscillation, and spectral output. Computed and measured thresholds are compared with those of ruby crystals. Measurements of the energy output of the laser and an estimate of the losses in the resonator are reported.
Effect of Electrical Fields in the Gamma Radiolysis of Propane
Authors: Ausloos P. , Gorden R.
Published: January 2005

The γ-ray radiolysis of C3H8–C3D8 mixtures and of CD3CH2CD3 has been investigated as a function of applied electrical field up to voltages necessary to cause secondary ionization. In the saturation current region, those products which in previous studies were ascribed to ethyl and vinyl ions remain constant with a change in field strength, while products which were originally attributed to the decomposition of neutral excited propane molecules are seen to increase about fivefold before the onset of secondary ionization. The inferred yields of C2H5+ and C2H3+ per ion pair at a propane pressure of 3 cm are 0.40 and 0.08, respectively. These values compare favorably with those deduced from the fragmentation of propane within 10—10 sec as calculated by Vestal, Wahrhaftig, and Johnston on the basis of the quasiequilibrium theory of mass spectra.

The modes of decomposition of the neutral excited propane molecules formed by electron impact are the same as those observed in the vacuum-ultraviolet photolysis at 1470 and 1237 Å. From the isotopic analysis of the products formed in the radiolysis of CD3CH2CD3 at high field strengths, it can be concluded that the average energy imparted to the neutral propane molecule by electron impact is larger than 10 eV, indicating that superexcited states of propane may be produced in the radiolysis. A value of 0.3±0.1 can be ascribed to the ratio of the number of neutral excited molecule decompositions to the number of ion pairs produced in the direct radiolysis of propane in the absence of an electrical field.
Shock-Tube Study of Nitrous Oxide Decomposition
Authors: Fishburne E. Stokes , Edse R.
Published: January 2005

The thermal decomposition of nitrous oxide has been studied in the temperature region from 1500° to 2200°K. Shock-tube techniques, employing the region behind the initial shock waves, were used. Argon, nitric oxide, and oxygen were used as diluents with 2% nitrous oxide in order that the temperature may remain practically constant during the reaction. The nitric oxide—nitrous oxide reaction appears to be bimolecular with a rate constant k3=2.0×1014 exp[— (50 000/RT)]. The argon—nitrous oxide and oxygen—nitrous oxide reactions appear to be bimolecular at low concentrations but become unimolecular at higher concentrations. The maximum activation energy, 55 700 kcal, in the argon—nitrous oxide mixtures was obtained for the highest concentration, 1.50×10—4 mole/cc. It is shown that the decomposition occurs via the triplet states of nitrous oxide.
Relaxation of Optically Pumped Cesium Atoms by Different Buffer Gases
Authors: Legowski S.
Published: January 2005

The decay of spin polarization of optically pumped cesium atoms at room temperature in the inert buffer gases helium, neon, and argon, has been investigated at different buffer gas pressures. It has been found that the decay of the spin polarization is not a simple exponential but can be described as the sum of two exponentially decaying modes, which are interpreted as two diffusion modes. The diffusion coefficients for cesium in helium, neon, and argon are found to be 0.37, 0.24, and 0.19 cm2/sec, and the collision depolarization cross sections are 2.5×10—24, 8.4×10—24, and 26×10—24 cm2, respectively.
Thermodynamic Effects of Mixing Light and Heavy Water
Authors: Narten Alfred
Published: January 2005

The thermodynamic functions for the isotopic exchange reaction H2O+D2O=2HDO in the gas and liquid states are computed from recent experimental data. They differ from previously published values. Excess functions for liquid mixtures of the water isotopes are derived. For ideal solutions of the water isotopes, these functions can be evaluated numerically. The calculated excess enthalpy of mixing is in agreement with the experimental heat of mixing. The possibility of nonideal behavior of isotopic water solutions is discussed.
Molecular Schrödinger Equation. III. Calculation of Ground-State Energies by Extrapolation
Authors: Conroy Harold
Published: January 2005

The problem of optimization of the parameters in a trial wavefunction can be approached through the minimization of the energy variance function, a procedure which offers certain important advantages over the customary one where the energy function itself is minimized. The use of an energy variance calculation further permits extrapolation to a more accurate approximation to the true energy than can be attained solely from a knowledge of the ordinary upper and lower bounds. Specific computational procedures are discussed.
Molecular Schrödinger Equation. IV. Results for One- and Two-Electron Systems
Authors: Conroy Harold
Published: January 2005

A general form, based upon configuration interactions, but including correlation to hasten convergence, is proposed for two-electron wavefunctions. The advantages of the correlation treatment developed include the ability to remove the singularity in the interelectronic potential from the Schrödinger equation. The results of sample calculations for hydride ion and helium are presented.

In addition, the results obtained in the application of our one- and two-electron treatments to the systems HeH++, HeH+, and linear and triangular H3++ and H3+ are discussed in detail, the accurate potential energy surfaces for the latter molecules having been elucidated.
Deuteron Magnetic Resonance Study of Some Crystals Containing an O—D···O Bond
Authors: Chiba Takehiko
Published: January 2005

A deuteron magnetic resonance study was made on four compounds with an O—D···O hydrogen bond of different strengths. The deuteron quadrupole coupling constant eqQ, asymmetry parameter η, and the directions of the field gradient tensor were determined. The eqQ and η obtained are: KDCO3154.4±0.6 kc/sec,0.194±0.018,(COOD)22D2OD1(water)230.3±2.0 kc/sec,0.062±0.006,D2(water)219.1±2.0 kc/sec,0.16±0.03,}    (at−70∘C)   D1 and D2121±3 kc/sec,0.93±0.02,(at 67∘C)   D3(carboxyl)139.2±0.8 kc/sec,0.098±0.005,ND4D2PO4 (acid D)119.6±0.8 kc/sec,0.053±0.008,K, D−maleate 56.0±0.8 kc/sec,0.53±0.07.

The results are discussed in relation to the crystal structure in each case. It was found that the oxalic acid dihydrate crystal used was a new modification, different from the ordinary one. Reorientational motion of a water molecule similar to that in other hydrated crystals was observed in oxalic acid dihydrate from the measurement at different temperatures. A barrier to this motion of 10.0 kcal/mole was determined from the temperature dependence of the linewidth.

In each compound studied, correlation between the principal axis directions of the field-gradient tensor and the local atomic arrangement in the crystal can be readily observed. The direction of the largest principal component of the field gradient tensor is in good agreement with the O—D direction or the O—D···O direction. The direction of the second principal component is generally in good agreement with the normal to the plane defined by[Complex chemical formula]The deviation from the latter rule can be seen in D1 of oxalic acid dihydrate where O—D···O differs greatly from a straight bond.

A marked decrease of eqQ with increasing hydrogen-bond strength is observed. Both the field gradient and the square of the OH stretching frequency as a function of O···O distance are in fairly good agreement with each other, similar to the near equality of the field gradient and force constant in diatomic hydrides. The change in the electronic contribution to the field gradient with O–H distance in the hydrogen bonded system is estimated.
Studies in Irreversible Thermodynamics. I. Internal Equilibrium and the Reciprocal Relations
Authors: Hill Terrell L. , Plesner Igor W.
Published: January 2005

A simple lattice-gas model is studied (Sec. II) which serves to illustrate the following points. If a system approaches equilibrium with its surroundings through only such processes as involve exchange between system and surroundings (i.e., no internal processes are available to the system) and if the kinetic behavior of the system depends on internal parameters as well as on thermodynamic variables, then in general the system will not achieve internal equilibrium prior to the final state of equilibrium with the surroundings. The usual flux-force equations and reciprocal relations of irreversible thermodynamics for such a system are concerned explicitly with thermodynamic variables and assume internal equilibrium with respect to the internal parameters. Therefore, in general, systems of the type referred to will not obey conventional flux-force equations nor exhibit reciprocal relations. The same conclusions would be expected if internal processes exist but are no faster than the exchange processes.
Dipole—Quadrupole and Retardation Effects in Low-Energy Atom—Atom Scattering
Authors: Fontana Peter R. , Bernstein Richard B.
Published: January 2005

Simple approximation formulas are derived for the dipole—quadrupole and retardation effects upon the total elastic scattering cross section for atomic collisions in the thermal energy range. For a long-range potential containing both the dipole—dipole and dipole—quadrupole terms, i.e., V(r) = —(C(6)/r6)[1+(β/r2)], one finds ΔQ/QMM≈⅔π(β/QMM) where QMM is the Massey—Mohr cross section for an inverse sixth-power attraction. For a long-range potential including dipole—dipole and retardation effects, approximated by V(r) = —(C(6)/r6)[a/(a+r)], one obtains ΔQ/QMM≈−(π−32QMM12)/a. Since these deviations are small and opposite in sign, it is concluded that the contributions of the dipole—quadrupole and retardation effects to the total cross sections are not sufficient to account for any significant discrepancy between theoretical and experimental Q values.
Free-Electron Model and Doublet Splitting in Aromatic Hydrocarbon Ions
Authors: Basu Sadhan
Published: January 2005

Doublet splitting in hydrocarbon ions due to spin—orbit interaction arising from electron circulation around the ring has been calculated using a free electron model.
Electron Spin Resonance Spectra of Methyl-Substituted Dihydropyrazine Cations and Related Radicals
Authors: Barton B. L. , Fraenkel George K.
Published: January 2005

Electron spin resonance spectra have been obtained for the cation radicals of dihydropyrazine and its methyl-substituted derivatives, and of dihydroquinoxaline, 2,3-dimethyldihydroquinoxaline, dihydrophenazine, and N,N′-dihydro-4,4′-dipyridyl. It was found that the parameter which determines the effect on 14N splittings of the spin density on an adjacent carbon atom has the value QCNN=2.62 G. This result was obtained without making any assumptions about the magnitudes of the sigma—pi parameters and without using valence-theory calculations of pi-electron wavefunctions. The positive sign for QCNN is opposite to that expected from the analogous parameters QCHH and QC CC. The small value of QCNN, and the approximate constancy of the ratio (sum of the spin densities on atoms adjacent to the nitrogen atom) to the (spin density on the nitrogen atom) in most of the compounds for which data are available, makes it possible to represent the nitrogen splittings by the expression aN=—0.940 aNHH, where aNHH is the NH—proton splitting. In some radicals with a large adjacent spin density, however, QCNN may make a significant contribution to the nitrogen splitting. Values of the NH—proton parameter QNHH, and of the C–CH3 parameter QMeH, were obtained as a function of an assumed value of the parameter QCHH for CH protons. With QCHH=—23.7 G, it was found that QNHH=—33.7 G and QMeH=18.4 G. The latter value is considerably smaller than usually assumed for methyl-proton splittings. Molecular orbital calculations for the methyl-substituted pyrazines, as well as for the other cations studied, were in good agreement with experiment.
Coriolis Perturbations in the Infrared Spectrum of Diborane
Authors: Smith W. L. , Mills I. M.
Published: January 2005

High-resolution infrared spectra of B2H6 vapor are reported. The sample was prepared from the naturally occurring 11B–10B isotopic mixture. The rotational structure of the infrared bands has been analysed for Coriolis perturbations due to rotation about the axis of least moment of inertia (the B···B axis). The following results have been obtained: (a) interaction between the Type A fundamental ν18 and the inactive fundamental ν5 has been observed, thus confirming the assignment of ν5 at 833 cm—1, giving | ζ5,18Z |=0.55±0.05; (b) interaction observed between the Type A combination band (ν10+ν12) at 1283 cm—1 and the inactive combination (ν10+ν7) gives an estimate of the unobserved fundamental ν7 as 850±30 cm—1, and an estimate of | ζ7,12Z |=0.6±0.1; (c) the absence of any observed perturbation of the Type C fundamental ν14 at 973 cm—1, suggests, by negative arguments, that either the unobserved fundamental ν9 does not lie in the frequency range 900 to 1100 cm—1, or | ζ9,14Z |<0.2. The assignment of the unobserved fundamental vibrations of diborane is discussed in the light of this evidence.
Electron Spin Resonance of Mn2+ in the Ternary System NH4Cl–MnCl2–H2O
Authors: Seed T. J.
Published: January 2005

Solid solutions grown from the ternary system NH4Cl–MnCl2–H2O with Mn2+ concentrations up to 8% by weight show a change of structure from cubic to tetragonal in the vicinity of 4% Mn2+. Electron spin resonance at X band shows an extraordinarily complex spectrum for the series, and a change in hyperfine structure intensity with change of structure. Previous workers have shown by x-ray diffraction that the tetragonal phase, which occurs at high concentrations of manganese, is due to ordered arrangement of NH4Cl double cells in which the manganese ion is interstitial. It is deduced from the electron spin resonance results that the double cell structure also holds at low concentrations, the bcc phase shown by x-ray diffraction being due to a lack of order among such double cells. A Q-band spectrum yields an exceptionally large axial parameter D=0.150 cm—1, and a small cubic parameter a=2.8×10—4 cm—1 in the spin Hamiltonian.
Additional Observations of Chemiluminescence in Mixtures of Atomic Oxygen and Nitrogen
Authors: Young Robert A. , Sharpless Robert L. , Stringham Roger
Published: January 2005

Reinvestigation of the nitrogen afterglow using specially purified nitrogen indicates that an intermediary or precursor in the reaction path leading from free nitrogen atoms to the emission state is quenched by N2 but not by He. The O2 atmospheric bands and the O I 5577-Å line were not detected at the NO null titration point. The O2 Herzberg bands are independent of pressure in both N2 and 1% N2 in He systems, indicating that equilibrium exists between the radiative state and free atomic oxygen.
Boundary Conditions at Infinity for a Single Blocking Electrode
Authors: Gatland Ian R. , Gold Louis , Moffat John W.
Published: January 2005

A mathematical appraisal is made of the boundary conditions at infinity for certain space-charge problems such as the single blocking electrode. Fulfillment of the boundary condition that the potential approach a limiting value at infinity resides in an appropriately devised theorem. The validity of approximate Poisson-type differential equations can be ascertained by invoking the Jacobian. Two separate situations are considered: (1) carriers of either sign mobile, (2) positive charges fixed. The latter corresponds to a problem (first) considered by MacDonald. A new formulation for the latter proves illuminating and an asymptotic solution is deduced for the spatial variation of the potential which reflects the essential exponential nature of its behavior.
Thermodynamic Functions of Morse Oscillators
Authors: Crecely Roger W. , Wilson David J.
Published: January 2005

Partition functions and thermodynamic functions are calculated for one-dimensional classical and quantal Morse and harmonic oscillators to investigate anharmonic and quantal effects. Results are shown graphically for oscillators corresponding to H2, D2, and N2; results on Br2 are described briefly.
Energy-Distribution Function for Hot Atoms Produced by Nuclear Transformations
Authors: Hsiung Chi-hua , Verosub Kenneth L. , Gordus Adon A.
Published: January 2005

The energy-distribution function for hot atoms produced by nuclear transformations is examined in terms of the fraction of the initial hot-atom energy. Energy dependent and independent asymmetric scattering is specifically considered. For gaseous tritium generated by the 3He(n, p) process, the asymptotic solution probably can serve as a reasonable approximation of the distribution function in the energy range 2–20 eV. For hot atoms produced with an initial distribution of energies, such as 79Br(n, γ)-produced 80Br, the asymptotic solution will be less valid than for tritium, but may still be a valid approximation.
Infrared Spectra in the Characterization of Some Molecular Complexes of the Dative Type
Authors: Matsunaga Yoshio
Published: January 2005

The infrared spectra of six diamine—quinone complexes and eight azine—quinone complexes were examined and compared with those of the component quinones and the semiquinone salts. The absence of the quinone but the presence of the semiquinone ion was proved in these complexes; therefore, the complexes may be characterized as essentially of the dative type. It is pointed out that most, if not all, of the known complexes having relatively low electrical resistivity are of this type.
Near-Infrared Emission Spectrum of NO
Authors: Horn Eugene F. , Dickey Fred P.
Published: January 2005

The emission spectrum of the vibration—rotation bands of the electronic ground state of nitric oxide has been observed in the 1.83–1.95- and 2.63–2.81-μ regions under moderately high resolution. The source of the spectrum was a high-tension discharge maintained through streaming nitric oxide gas at pressures of less than 1 atm. A detailed analysis of the 2–0, 3–;1, and 4–;2 bands, occurring at 2.69, 2.73, and 2.77 μ, respectively, has been carried out. Accurate values obtained for many of the rotational and vibrational constants associated with the 2II½ and Π322 substates of the electronic ground state are presented, including a value for the spin—orbit coupling constant A. Also, the effective rotational temperature of the emitting gas has been determined.
Relative Rates of Reaction of Bromine Atoms with Isotopic Hydrogen Molecules
Authors: Timmons Richard B. , Weston Ralph E.
Published: January 2005

Kinetic isotope effects in the reaction of bromine atoms with isotopic hydrogen molecules were measured in this investigation. Rate constant ratios were determined by isotopic analysis of H2–HD, H2–HT, or H2—D2 mixtures before and after reaction with bromine atoms. Over the temperature range of 438° to 623°K, the ratios of the second-order rate constants were kH2/ΣkHD = (1.14±0.01) exp(591±4/RT), kH2/ΣkHT = (1.22±0.02) exp(658±16/RT), kH2/kD2 = (1.32±0.04) exp(1253±37/RT).

A comparison of these results with the corresponding isotope effects obtained in the chlorine- and iodine-atom experiments reveals surprisingly little difference in kinetic isotope effects.

The theoretical calculation of the kinetic isotope effects was carried out using Bigeleisen's theory of isotope effects on reaction rates. The calculations were made using various methods of constructing the potential energy surface and it was found that none of the semiempirical methods used gave agreement to better than 40% to 80%.
Separation of Calcium Isotopes in an Amalgam System
Authors: Zucker Donald , Drury J. S.
Published: January 2005

Concentration of the heavy isotopes of calcium by means of the chemical exchange reaction Ca(Hg)46+Ca(solution)++40=Ca(Hg)40+Ca(solution)++46 was studied. The reaction was found to be technically feasible as a pre-enriching process for Calutron feed material; its economic attractiveness depends upon a sufficiently large scale of application. At 25°C, the single-stage separation factor for isotopes differing by one unit of mass was 1.0013±0.0003 (95% C.I.). The half-time of exchange of calcium was less than 7 sec. The solubility of calcium in mercury varied from 0.562M at 0°C to 0.908M at 36°C. The integral heat of solution of calcium in mercury was given by the least-squares equation, —ΔH±0.2(95% C.L.)=45.43–0.56M.