bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Capacities and Thermodynamic Functions of YH2 and YD2 from 5° to 350°K and the Hydrogen Vibration Frequencies
Authors: Flotow Howard E. , Osborne Darrell W. , Otto Klaus
Published: January 2005

The heat capacities of pure YH2 and YD2 were measured by an adiabatic method from 5° to 350°K. The compounds were found by x-ray analyses to consist of a single phase, with the yttrium atoms in face-centered cubic positions. Below 16°K the heat capacities of the two compounds are equal within experimental error, between 16° and 90°K the heat capacity of the hydride is about 0.02 cal deg—1 mole—1 greater than that of the deuteride, and at higher temperatures that of the deuteride becomes appreciably greater. The difference in the heat capacities above 100°K is ascribed to a single optical vibration of the hydrogen atoms, whose frequency is shifted upon isotopic substitution. The difference in the heat capacities of YH2 and YD2 in the temperature range 100° to 350°K is fitted to ±0.02 cal deg—1 mole—1 with Einstein heat capacity functions and a frequency of 1030±30 cm—1 for YH2 and 1030/√2 for YD2. These results are compared with those obtained by inelastic neutron scattering experiments.

The values obtained for the heat capacity, entropy, enthalpy and Gibbs free-energy function for YH2 at 298.15°K are 8.243±0.016 cal deg—1 mole—1, 9.175±0.018 cal deg—1 mole—1, 1403±3 cal mole—1 and —4.470±0.009 cal deg—1 mole—1, respectively. The corresponding values for YD2 are 10.773±0.022, 10.294±0.021, 1659±3 and —4.729±0.010. The enthalpy of formation of YH2 minus the enthalpy of formation of YD2 is calculated to be 0.78±0.08 kcal mole—1 at 0°K and 0.55±0.08 kcal mole—1 at 298.15°K.
Photochemical Primary Process in Biacetyl Vapor at 4358 A
Authors: Noyes W. Albert , Mulac W. A. , Matheson Max S.
Published: January 2005

At 4358 A at room temperature the quantum yield for the primary dissociation of biacetyl increases with intensity. It is thus implied that the primary process is second order in some active species. By use of the rotating sector it is shown that the species responsible for this effect has a mean life close to that ascribed to an excited triplet state for biacetyl. At higher temperatures this intensity effect disappears and one of the products strongly inhibits both the phosphorescence and the primary dissociation. At these temperatures the data may best be treated by assuming that the triplet state of biacetyl undergoes a unimolecular dissociation with an activation energy of about 15 kcal.
Infrared Spectra in Polarized Light and Vibrational Assignment of the Infrared Active Modes of Anthracene and Anthracene-d10
Authors: Califano S.
Published: January 2005

Infrared spectra of anthracene and anthracene-d10 of high deuterium content are reported. The spectra were measured in the gas phase, in solution, in KBr pellets, and in single crystals with polarized radiation. The experimental dichroism of the observed bands has been used to furnish a vibrational assignment of the infrared active modes. This assignment shows striking similarities with the assignment given in the literature for naphthalene.
Second Virial Coefficient for the Spherical Shell Potential
Authors: De Rocco Andrew G. , Hoover William G.
Published: January 2005

Values of the second virial coefficient for the three-parameter spherical shell potential are tabulated over wide ranges of temperature and shell size. The potential, which is not new, results from the interaction of two spherical surfaces having uniform distributions of Lennard-Jones (6–12) sites.

An objective comparison is made between the tabulated values and the literature values for second virial coefficients, from which the potential parameters for twenty compounds are determined. Generally, the spherical shell potential generates a better fit than does the parent Lennard-Jones potential. The potential parameters found are in good agreement with expectations based upon density and interatomic distance data.
Hypervirial Theorems Applied to Molecular Quantum Mechanics
Authors: Hirschfelder Joseph O. , Coulson C. A.
Published: January 2005

Previous discussions of hypervirial theorems in wave mechanics have been extended in three ways. (1) A particular class of operators called compound hypervirial operators is introduced, and the particular point transformations which they may be said to generate are studied. (2) An example of these new operators is an electron-correlation hypervirial, which modifies a wave function when two electrons are near together but exerts little influence when they are a long way apart. (3) A study is made of possible wave functions for a diatomic molecule which satisfy the Hellmann-Feynman theorem and provide a means of deducing the shape of the potential energy curve, or its slope at a particular internuclear distance.
Microwave Structure Determinations on Tertiary Butyl Acetylene and Tertiary Butyl Cyanide
Authors: Nugent Leonard J. , Mann D. E. , Lide David R.
Published: January 2005

The microwave spectra of eight isotopic species of tertiary butyl acetylene and four isotopic species of tertiary butyl cyanide have been measured and analysed. Some transitions in excited vibrational states have been assigned. Measurements of the Stark effect lead to a dipole moment of 0.661±0.004 D for (CH3)3CCCH and 3.95±0.05 D for (CH3)3CCN. From the isotope shifts in the moments of inertia the following bond distances (rs) are obtained: r(C≡C) = 1.209±0.001 A and r(≡C–H) = 1.056±0.001 A in (CH3)3CCCH; r(C≡N) = 1.159±0.001 A in (CH3)3CCN. The tertiary butyl group appears to have very nearly the same dimensions in these two compounds as in (CH3)3CH and (CH3)3CF. The tertiary carbon atom cannot be located with high precision, but the best estimates lead to a C–C≡ distance of 1.495±0.015 A in both (CH3)3CCCH and (CH3)3CCN. This is 0.02–0.04 A longer than the normal value for this distance. There appears to be a consistent tendency for the (CH3)3C— group to lengthen the adjacent bond, but it is difficult to find an explanation in terms of existing theories.
Heat Capacity and Entropy of CoCl2 and MnCl2 from 11° to 300°K. Thermal Anomaly Associated with Antiferromagnetic Ordering in CoCl2
Authors: Chisholm R. C. , Stout J. W.
Published: January 2005

The heat capacities of MnCl2 and CoCl2 have been measured between 11° and 300°K. By the use of the measurements of Murray on MnCl2 at lower temperatures the lattice and magnetic contributions to the heat capacity and entropy of MnCl2 have been evaluated. CoCl2 has a lambda peak in heat capacity at 24.71±0.05°K associated with the cooperative ordering of the magnetic moments of the cobaltous ions. The entropy change associated with this cooperative ordering is R ln2. Smooth values of the heat capacity, entropy, enthalpy, and free energy are tabulated at selected temperatures. The values of the entropy and enthalpy at 298.15°K are: MnCl2, S° = 28.26±0.05 cal deg—1 mole—1, H°–H0° = 3602±8 cal mole—1; CoCl2, S° = 26.09±0.05 cal deg—1 mole—1, H°–H0° = 3375±8 cal mole—1.
Structure and Dipole Moment for SF4
Authors: Tolles W. M. , Gwinn William D.
Published: January 2005

The microwave spectrum and structure of sulfur tetrafluoride has been determined. One FSF angle is 101°33′±30′, the opposite FSF angle is 186°56′±30′. The bond length for the nearly linear bonds is 1.646 A±0.003 A; for the other pair it is 1.545 A±0.003 A. The dipole moment was determined from the Stark effect to be 0.632±0.003 debye.
Studies in Molecular Structure. VII. Limited Configuration Interaction for Selected First-Row Diatomics
Authors: Fraga Serafin , Ransil Bernard J.
Published: January 2005

Calculations on selected first-row diatomic molecules using a limited configuration interaction with minimal LCAO MO SCF wave functions are described. Molecular energies, dipole moments, and population analyses are tabulated and discussed. These results provide an extensive foundation for a tentative evaluation of the value of limited configuration interaction for LiH, BH, NH (d1Σ+), HF, Li2, C2, N2, F2, LiF, CO, and BF within the limits of the approximations used.
Electron Coupling of Nuclear Spins. V. Vibrational Effects in CHX Groups
Authors: Gutowsky H. S. , Mochel V. D. , Somers B. G.
Published: January 2005

Previous calculations of the H–H coupling in CH2 groups assumed a static H–C–H bond angle. It is shown here that, because the predicted angular dependence of the coupling is nonlinear, the bond-bending vibrations should give an averaged value appreciably larger than that for the corresponding equilibrium, but static, angle. The contribution of excited vibrational states is very small and hence the averaged coupling constant is effectively temperature independent. There should be a small but detectable difference in the coupling constants for CH2 and CHD groups because of the isotopic differences in vibrational amplitude. The experimental coupling constants exhibit an apparent linear dependence upon the equilibrium H–C–H angle, and careful measurements of the isotope effects could be useful in establishing whether or not there is any explicit curvature in the angular dependence, and thus whether the observed linearity is real or due to the neglect of substituent effects in the calculations. In any case, comparison between experiment and the predicted angular dependence suggests that too low a value may have been used previously for one of the exchange integrals, K(C1, C2) in the calculations for both the CH2 and the HCCH groups. An attempt to detect an isotopic difference between the geminal H–F and D–F coupling in n—C3F7H and n—C3F7D gave negative results.
Theoretical Investigations on the Light Scattering of Spheres. XIII. The ``Wavelength Exponent'' of Differential Turbidity Spectra
Authors: Heller Wilfried , Bhatnagar Hari L. , Nakagaki Masayuki
Published: January 2005

The exact theory of the ``wavelength exponent'' of the turbidity is developed for Rayleigh scattering and ``Debye scattering'' and, particularly, for Mie scattering by nonabsorbing spheres. The basic exponent, n, defined by {α[∂ln(τ/c)0/∂α]+1} is computed from Mie turbidity data, reported previously, for α=0.40 (0.04) 0.68, 0.80 (0.2) 25.0 and m=1.05 (0.05) 1.20. For m=1.25 and 1.30, the smallest α values and the Δα intervals are the same, but the upper limiting α values are 14.0 and 11.6, respectively. In addition, α values<0.40 are considered for m=1.05. The actual exponent to be expected in a given dispersed system n0 is found to depend on three additional factors: (1) The rate of change of the turbidity with the relative refractive index of the spheres [this factor is evaluated for α=0.4, 1.0 (1.0) 7.0 and m=1.05 (0.05) 1.30 and approximating equations are given for purposes of interpolation]. (2) The dispersion of the relative refractive index of the spheres. (3) That of the refractive index of the medium. The advantages and limitations of an application of the wavelength exponent to particle size determinations are discussed and labor saving approximating n(α) relations, suitable for first approximation results on particle size, are given. The effect of heterodispersion upon the wave length exponent is briefly discussed.
Electronic Structure and Hyperfine Coupling Constants for NO2 and Related Molecules
Authors: Hijikata Katsunori , Lin Chun C. , Baird James C.
Published: January 2005

The electronic structure of NO2 and related molecules is discussed by means of a correlation diagram between the molecular orbitals of O3 and CO2. The general properties of the hyperfine structure constants for the different kinds of orbitals are discussed and compared with the experimental results of NO2 and ClO2. The hyperfine structure constants are used to identify the symmetry properties of the ground states of NO2 and ClO2 and also to estimate some coefficients of the atomic orbitals in the LCAO MO.
Vibrational Spectrum and Structure of Single Crystals of K3Co(CN)6
Authors: Jones Llewellyn H.
Published: January 2005

The polarized infrared absorption spectra of single crystals of K3Co(CN)6 have been observed from 5000 to 280 cm—1. By combining this data with Raman and crystal structure data of other authors, most of the fundamental frequencies have been assigned. Force constants have been calculated using the recently derived resonance interaction valence force potential function which reduces the number of interaction terms in accord with theories of bonding. The primary stretching force constants are: FCN=16.8 md/A and FCoC=1.8 md/A.

It is shown that the observed spectrum cannot be satisfactorily explained with a Urey-Bradley force field.
Nuclear Quadrupole Coupling Tensors for Na23 and Al27 in Natrolite, a Fibrous Zeolite
Authors: Petch H. E. , Pennington K. S.
Published: January 2005

The nuclear magnetic resonance spectra of Na23 and Al27 in a single crystal of natrolite (Na2Al2Si3O10·2H2O), a fibrous zeolite, have been investigated at room temperature in an external magnetic field of 7380 gauss. It was found that the sodium and aluminum atoms each occupy a single chemically unique site in the unit cell. The quadrupole coupling constants and asymmetry parameters of the electric field gradient tensors at these sites were determined to be       Na23      Al27eqQ/h1759.3±0.3 kc/sec1663.3±0.2 kc/secη0.6427±0.00040.5029±0.0005.The orientations of the principal axes of the electric field gradient tensors for the above sites and their symmetry-related sites have also been determined.
Microwave Spectrum, Structure, Quadrupole Coupling Constants, and Barrier to Internal Rotation of Chloromethylsilane
Authors: Schwendeman R. H. , Jacobs G. D.
Published: January 2005

Observations of the microwave spectra of seven ground-state species and three first excited torsional state species of CH2ClSiH3 are reported. From an analysis of the moments of inertia of the various species structural parameters are deduced as follows: bond distances; CCl=1.788 A, CSi=1.889 A, CH=1.096 A, SiH=1.477 A, and bond angles; SiCCl=109.3°, SiCH=109.3°, HSiH=110.6°, and HCH=107.5°. An analysis of the hyperfine splitting leads to quadrupole coupling parameters χCCl bond=—68.7 Mc, ηCCl bond=0.048, if it is assumed that the CCl bond direction forms one principal axis of the quadrupole tensor; and χCCl bond=—72.0 Mc if it is assumed that the quadrupole tensor is cylindrically symmetric. Analysis of splittings in the first excited torsional state indicate that the height of the potential barrier hindering internal rotation of the SiH3 group is 2.55 kcal/mole.
Pressure Dependence of Fluorescence Spectra. II. Transient Effects
Authors: Wilson David J.
Published: January 2005

The dependence of the transient fluorescence spectrum of a gas on pressure and time is investigated; vibrational relaxation effects are considered. Matrix methods are used to obtain a formal solution to the general problem, and the generating-function technique used by Montroll and Shuler is employed to solve a special model involving stepwise deactivation. Two strong collision models are also analyzed.
Third- and Fourth-Order Interactions of Argon with a Graphitized Carbon Black
Authors: Sams J. R. , Constabaris G. , Halsey G. D.
Published: January 2005

Data for the third- and fourth-order interactions of argon with the highly graphitized carbon black P33 (2700°) are presented. These data have been analyzed by means of a two-dimensional gas model to give an estimate of the interaction energy between the adsorbed atoms, and a new method for determining the surface area of the adsorbent. Relations between the two-dimensional gas model and a model which assumes pairwise additivity of potentials are discussed.
Kinetics of Excited Molecules. IV. Unimolecular Dissociation of Ketene
Authors: Taylor Gladstone A. , Porter Gerald B.
Published: January 2005

Careful quantum yield measurements of carbon monoxide in the photolysis of ketene indicate that collisional deactivation of excited molecules occurs by a strong collision mechanism. The data can be adequately fitted by classical unimolecular theory in which the rate of decomposition is a function of the vibrational energy of the molecule, essentially disregarding the electronic energy.
Configuration Interaction Study of the Lithium Hydride Molecule
Authors: Ebbing Darrell D.
Published: January 2005

A set of orbitals in elliptical coordinates has been used as basis in a self-consistent field configuration interaction (SCF–CI) study of the electronic structure of the ground state (1Σ+) of the lithium hydride molecule. The importance of various configurations is studied, and it is found that those configurations are most important which have either the inner-shell molecular orbital or the valence-shell molecular orbital doubly occupied. The results of each configuration interaction calculation have been analyzed into contributions to the inner-shell and outer-shell correlation energies, and in this way the importance of various orbitals is studied and related to correlation effects. It appears that LiH could be well described by a product of electron-pair wave functions.

A study of the numerical stability of the calculations shows that considerable care must be exercised in the choice of a basis in order for the results to be meaningful. Instability of a calculation is due to near linear dependency of the orbital basis.

The best total energy obtained, using 53 configurations formed from a basis of 7σ and 3π orbitals, is —8.04128H at an internuclear distance of 2.99B. This should be compared with the experimental energy of —8.0703H. The dipole moment was calculated to be 5.96D, and the ratio of dipole moment to dipole derivative is μe/(δμ/δr)ere=1.53 (experimental values are 5.88D and 1.8±0.3, respectively).
Unperturbed Dimensions of Linear Atactic Polymers
Authors: Yoo Sung J. , Kinsinger Jack B.
Published: January 2005

A formalism is developed for calculating the unperturbed dimensions of linear atactic polymers of repeating type (CHR)n and (CH2–CHR)n taking into consideration penultimate effects in the configurational propagation steps and first and second neighbor interactions in the conformational distribution. It is assumed that the configurational and conformational distributions are independent. The calculation has been formalized via the Ising model using a matrix method. The unperturbed dimensions of isotactic and syndiotactic chains are derived as special cases of atactic chains.
Electronic and Ionic Conductivity in Single Crystals of MgO
Authors: Mitoff S. P.
Published: January 2005

The electrical conductivity and relative fractions of ionic and electronic conductivity of single crystals of MgO were measured between 1000° and 1500°C. The results resolve conflicting observations of electronic and ionic conductivity of previous investigations in that MgO is shown to exhibit both kinds of conductivity in this temperature range. The nature of the charge carriers depends on temperature, the surrounding oxygen pressure, and the purity of the crystal.

The following conditions favor predominant electronic conductivity: (1) high temperatures (>1300°C), (2) high (1 atm) or very low (<10—6 atm) oxygen partial pressures, (3) contamination, specifically Li, was found to increase the relative electronic fraction. Conversely, low temperatures (<1300°C), intermediate (10—4 to 10—5) oxygen partial pressures, and probably high purity favor predominant ionic transport. The electronic conductivity observed at the higher temperatures most likely results from point defects created in thermodynamic equilibrium.
Interaction Energy of an Alkali Metal with a Rare Gas
Authors: Scheel Nivard , Griffing Virginia
Published: January 2005

A molecular orbital self-consistent field calculation is made for closed shell ions, LiHe+ and LiHe— as function of internuclear distance. The eigenfunctions obtained from these calculations were used to calculate the potential energy curves for the neutral Li–He. This system has some interesting properties. For example, these calculations suggest the probable quenching of certain excited states of an alkali metal when in close interaction with a rare-gas atom. All of the curves obtained are repulsive except for the LiHe+ curve which has a shallow minimum and follows an expected 1/r4 attractive potential. Fair values are obtained for the ionization energies of the Li and He atoms and the electron affinity of Li. These calculations indicate that open-shell systems with few electrons can be treated by making the simpler SCF calculation on a closely related closed-shell system and using the resulting eigenfunctions to calculate the energy of the closed shell system.
Hyperfine Structure of the Rotational Spectrum of HDO
Authors: Treacy E. B. , Beers Yardley
Published: January 2005

The hyperfine structure of the 32→33 and 52→53 rotational transitions of HDO, which fall at about 825 and 487 Mc, respectively, have been studied using microwave cavities as spectrometers. The experiments illustrated the usefulness of large Q cavities as spectrometers for this kind of work. The 32→33 transition was resolved into a symmetrical pattern consisting of a strong central line with six weak satellites on each side. The minimum full linewidth between half-power points that was achieved was about 10 or 12 kc. The spectrum was fitted with CH=—46.6±0.3 kc, CD=—1.66±0.3 kc, and (eqQ)OD=310.3±3 kc. The 52→53 transition was resolved into a symmetrical pattern also, with a strong central line and three weak satellites on each side. The minimum full linewidth between half-power points was about 6 kc. The spectrum was fitted with CH=—47.38±0.1 kc, CD=—2.42±0.1 kc, and (eqQ)OD=314.3±1.5 kc. A systematic comparison of the results with those obtained elsewhere on the 21→22 transition in HDO is made. The qualitative features of the spectra are consistent with what one would expect on the basis of existing theory, but the present state of the theory may be inadequate for explaining some of the quantitative details of the magnetic structure.
Electrostatic Energy Matrices of the f7 Configuration
Authors: Runciman W. A.
Published: January 2005

The f7 electrostatic matrices have been derived by the methods of Racah and are tabulated. A previous table of spin-orbit matrix elements has been corrected and extended, and then used in a further analysis of the spectra of gadolinium salts. Finally, a tentative calculation has been made of the energy levels for the corresponding curium salts.
Isotope Effects and Electronic Energy in Molecules
Authors: Fröman Anders
Published: January 2005

The definition of electronic energy in molecules is analyzed and, in its conventional form, it is shown to be in slight disagreement with experimental experience. By means of a proper treatment of the center-of-mass motion, a modified concept called reduced electronic energy is introduced and shown to give more satisfactory results. In particular, the hydrogen molecule and its isotopic analogues are used for a quantitative comparison of the two concepts with experimental results.
Approximate Hartree-Fock Calculations for the Hydrogen Fluoride Molecule
Authors: Nesbet R. K.
Published: January 2005

Approximate Hartree-Fock calculations have been carried out on the 1Σ+ ground state of hydrogen fluoride at three internuclear distances near equilibrium. Roothaan's method is used, with basis orbitals chosen to represent a reasonably good approximation to the atomic Hartree-Fock orbitals and to allow for the principal polarization and distortion effects that must be expected when two atoms approach to within a chemical bond distance of each other. Total energies are comparable to calculated total Hartree-Fock energies for the separated atoms, and the calculated binding energy is improved by a factor of nearly 3 over binding energy calculated with fixed atomic Hartree-Fock orbitals. Thus this improvement can be attributed to polarization and distortion effects systematically neglected in earlier LCAO calculations. Physical and spectroscopic properties of several electronic states of HF and HF+ are calculated, and are found to be in reasonable agreement with experiment. Localized ``exclusive'' self-consistent orbitals have been calculated. They give a chemical picture of the structure of the molecule and make it possible to analyse the various contributions to the dipole moment, which is mainly due to the lone pair orbitals on the fluorine atom.
Radiolysis of Methylcyclohexane. II. Liquid Phase Inhibition by Benzene
Authors: Freeman G. R.
Published: January 2005

The effect of benzene on the radiolysis of liquid methylcyclohexane (MCH) has been studied over the benzene concentration range from 0.25 to 100 mole %. The dominant effect of benzene at low concentrations appears to be one of hydrogen atom scavenging. At higher concentrations, the transfer of energy (excitation or ionization) from activated MCH to benzene also becomes important.

As in the liquid cyclohexane system, there seem to be two major reactive species in γ-irradiated MCH. One species, C7H14′, decomposes to produce ``cold'' hydrogen atoms that can be scavenged by benzene. The other species, C7H14″ or C7H14+, produces hydrogen by a mechanism that is not subject to atom scavenging but which can be inhibited by an energy transfer process. The 100-ev yields of the activated species in pure MCH are G(C7H14′) = 1.8±0.3 and G(C7H14″) = 3.0∓0.3. These compare with the cyclohexane yields G(C6H12′) = 2.4±0.3 and G(C6H12″) = 3.0∓0.3.

Reaction mechanisms have been proposed and tested against the experimental data.
Nitrogen on Nickel Surfaces
Authors: Germer L. H. , MacRae A. U.
Published: January 2005

In this paper we have shown that nitrogen is not adsorbed upon a (110) face of a nickel crystal at room temperature. In previous experiments it has been found that nitrogen is not adsorbed upon more densely packed crystal planes and upon polycrystalline surfaces. The new result extends the conclusion to the more open and chemically active (110) face.
Ultraviolet Bands of Magnesium Hydroxide and Oxide
Authors: Brewer Leo , Trajmar Sandor
Published: January 2005

The molecular species responsible for the ultraviolet bands of ``magnesium oxide'' have been shown to be MgOH and MgO. The 3Π states of BeO and MgO have been approximately fixed and are the major contributors to the thermodynamic functions of BeO and MgO gases at high temperatures. In addition to a 1Σ+—1Π transition of MgO other transitions of MgO may lie in the same spectral region.
Mechanism of Atom Recombination by Consecutive Vibrational Deactivations
Authors: Benson Sidney W. , Fueno Takayuki
Published: January 2005

The process of atom recombination in the presence of foreign gases, M, not forming complexes with the atoms, is considered in terms of a cascade model in which deactivation occurs by small increments, essentially by one quantum at a time. This leads to an equation for the termolecular recombination rate constant: kr=λZK*G(T), where K* is the equilibrium constant for species X2* in equilibrium with X atoms, Z is the collision frequency of these species with M, and λ, assumed to be unity, is the probability that such species will be de-excited in a collision with M to the top vibrational level of X2, the diatomic molecule. The quantity G(T) is essentially the reciprocal of the number of vibrational states within a range of kT of the dissociation threshold.

Methods are given for the calculation of K*, G(T), and Z from physical data for the X2 and M molecules without any undetermined parameters. The use of Morse functions yields values of kr in excellent agreement with available experimental data for H2, N2, O2, Br2, and I2 over the range 300° to 2000°K (6000°K for O2) with argon as M.

The temperature dependence of kr is not simple and varies between light and heavy molecules. On the average and almost independently of the potential function used, it is in the range of T—1.

It does not appear as though contributions from other electronic states beyond the ground state are significant in the recombination process.
Determination of the Assignment of Triplet States in Catacondensed Aromatic Hydrocarbons
Authors: Kearns David R.
Published: January 2005

The assignment of the triplet states in benzene plays a central role in the determination of the assignment of triplet states of all the catacondensed aromatic hydrocarbons. In this paper two tests of the assignment of triplet states, based on (i) the prediction of triplet state energies in catacondensed aromatic hydrocarbons calculated using a perimeter model developed by Moffitt, and (ii) the prediction of the lowest singlet-triplet transitions in substituted benzenes calculated using perturbation theory, are developed and applied to existing data. A number of possible benzene triplet state assignments were considered. However, the above tests are in agreement with the generally accepted assignment in which the lowest triplet state in benzene as well as the linear catacondensed aromatic hydrocarbons is assigned to 3La (in the Platt notation). The first test (i) virtually rules out all alternative assignments. The second test (ii) is consistent with the favored assignment (lowest triplet state in benzene assigned 3La) and provides fairly strong evidence against the assignment which, on theoretical grounds, is considered the next most likely assignment (lowest triplet state in benzene assigned 3Lb). More crucial experiments are proposed which should lead to an even more definitive selection of the correct assignment of the triplet states in the catacondensed aromated hydrocarbons.
ESR Spectrum and Structure of the Formyl Radical
Authors: Adrian Frank J. , Cochran Edward L. , Bowers Vernon A.
Published: January 2005

The electron spin resonance (ESR) spectra of the formyl radical (HCO) and the deuterated radical (DCO) have been observed in solid carbon monoxide over the temperature range 4.2° to 30°K. The observed line shapes were temperature dependent, but the cause of the temperature dependence was not definitely determined. The radical was produced by the reaction of CO with hydrogen atoms produced by the photolytic decomposition of HI. The radical was also produced by the photolytic decomposition of formaldehyde in solid argon, and it was found to be one of the products of the photolysis of methyl alcohol in solid argon. The most striking feature of the ESR spectrum of HCO is the very large proton hyperfine splitting (137 oe). Also the lines were broad and unsymmetrical with the linewidth varying from one hyperfine component to the next. It was shown that the line shapes were due to the combination of a rather pronounced anisotropy in the electronic g factor with a smaller anisotropy in the proton hyperfine interaction. These characteristics of the radical gave a good deal of information about its structure which supported the conclusion of other workers that the formyl radical is not a π-electron radical.
Initial Stages of the Chlorine Atom Induced Polymerization of Acetylene
Authors: Wijnen M. H. J.
Published: January 2005

The initial stages of the chlorine atom induced polymerization of acetylene have been investigated. The photolysis of phosgene was used as a source of chlorine atoms. The following main reaction products were observed: carbon monoxide, vinyl chloride, 1-chloro-1,3-butadiene, benzene, and polymer. Small to trace amounts of monochloroacetylene and monochlorobenzene were also detected.

A qualitative examination of the formation and distribution of these products indicates that they are formed in the initial stages of the chlorine atom initiated polymerization of acetylene.

The data are compared with those obtained in other free radical induced polymerization reactions of acetylene.
Electron-Spin-Resonance Studies of DPPH Solutions
Authors: Ueda Hisashi , Kuri Zenichiro , Shida Shoji
Published: January 2005

The effects of impurities on the ESR of DPPH in various solutions were studied. The broad quintet spectrum usually obtained with DPPH solutions becomes well resolved after dissolved gases are removed. Addition of tertiary hydroperoxides to DPPH solutions gives a triplet spectrum, which further splits into 17 lines after subsequent degassing in the case of t-butyl hydroperoxide. From an analysis of this spectrum, a determination was made of the spin-density distribution of the unpaired electron in a species electronically analogous to biphenylaminium ion.

An aerated DPPH solution of xylene loses its paramagnetic nature in time, but regeneration of the quintet ESR spectrum of DPPH is observed if this solution is mixed with the so-called lophine-x compound solution kept in the dark, and then irradiated by sunlight. The interpretation of this phenomenon is that the lophine-x compound, when irradiated by sunlight, has an odd electron which shifts onto the nonparamagnetic DPPH—O2 reaction product regenerating DPPH as a result. This is, therefore, a radical transfer reaction and is one of the few chemical reactions giving evidence for the radical nature of the lopine-x compound when photochemically excited.
Photolysis of Nitrous Oxide. II. 1470 and 1830 A
Authors: Doering John P. , Mahan Bruce H.
Published: January 2005

The photolysis of N15NO and NN15O have been investigated using 1470- and 1830-A light. The products include small amounts of N230, as well as N229. The appearance of N230 shows that there are two primary processes occurring, one of which is the dissociation to a nitrogen atom and a nitric oxide molecule, the other dissociation to an oxygen atom and a nitrogen molecule. In addition, at 1470 A a photoexcited molecule is formed which is capable of dissociating another nitrous oxide molecule.
Heat Capacity of Critical Mixtures
Authors: Fixman Marshall
Published: January 2005

A theory is given of the heat capacity of liquid mixtures in the critical region. The entropy density is taken to be a function of the local composition and is expanded to quadratic terms in the composition fluctuation. The anomalous heat capacity computed from the average entropy fluctuation is very large because of the extreme sensitivity of the large composition fluctuations to the temperature. An application to a cubic lattice shows that the theory is equivalent to a ring diagram or random phase approximation in the theory of the Ising lattice. The heat capacity goes to infinity as (T—Tc)—½ in the critical region, for a mixture at the critical composition. Fair agreement with experiment is obtained; the one parameter which enters can be obtained, in principle, from x-ray or light scattering.
Double-Minimum Potentials in Hydrogen-Bonded Solids
Authors: Somorjai R. L. , Hornig D. F.
Published: January 2005

Using a simple one-dimensional model of H bonds, vibrational-energy eigenvalues, eigenfunctions, transition moments, and absorption intensities are calculated for a series of symmetric and asymmetric double-minimum (D.M.) potentials. On the basis of the results obtained, the necessary requirements for observing doublets in the infrared spectra of H-bonded solids are given. In most cases an asymmetric D.M. potential does not give rise to such doublets. Attention is drawn to the rapid ``switch-over'' from even-odd, odd-even to ``left-left,'' ``right-right'' selection rules when a slight asymmetry is introduced into a symmetric D.M. potential. Also, a very rapid uncoupling of resonance interaction between accidentally coincident ``left'' and ``right'' levels of strongly asymmetric D.M. potentials is predicted. The importance of obtaining accurate relative intensity values and of determining the infrared and Raman spectra of both the H-bonded solids and their deuterated analogs at several temperatures is emphasized.
Preparation of Semiconducting Cubic Boron Nitride
Authors: Wentorf R. H.
Published: January 2005

Semiconducting crystals of cubic BN may be prepared at high pressures and temperatures by adding small amounts of selected impurities to the synthesis mixture (hexagonal boron nitride plus lithium or magnesium nitride). P-type crystals, blue in color, can be prepared by adding Be; they may have resistivities of about 103 ohm-cm and activation energies for conduction of about 0.2 ev. N-type crystals can be prepared by adding S, Si, KCN, and other impurities; they were found to have resistivities of 103 ohm-cm or higher and activation energies for conduction of 0.05 to 0.20 v. The diffusion of impurities into cubic BN crystals was not found to proceed as rapidly as with diamond. Point-contact rectification effects have been observed among semiconducting cubic BN and diamond crystals.
Charge States of Molecular Fragments from CCl3Br Following Nuclear Decay of Br80m and Br82
Authors: Wexler S.
Published: January 2005

A comparison of the positive ionic fragments from dissociation of trichlorobrommethane by β—, γ decay of 35.9-hr Br82 and from isomeric transition of 4.4-hr Br80m was made by mass spectrometric techniques. Virtually all the products following beta decay are singly charged, while distributions of multiply charged atomic species dominate the fragmentation pattern after the isomeric transition. The results indicate that negative beta decay affects the molecule rather mildly, while the effect is violent following isomeric transition with internal conversion. In the latter mode of nuclear decay the molecule apparently explodes as a result of multicenter Coulombic repulsion.
Molecular Dimensions in Crystalline Polymers
Authors: Tobolsky A. V. , Gupta V. D.
Published: January 2005

In this paper we calculate from theoretical considerations the molecular dimensions of polymer chains in partially crystalline polymers existing in any state of orientation. Our theory also applies to isolated molecules in solution which have helical and random coil regions within the same molecule.

The treatment is based on two probability parameters and the mathematical method of the Markoff chain.
Non-Steady-State Nucleation
Authors: Courtney Welby G.
Published: January 2005

The non-steady-state nucleation of water vapor is examined by an exact mathematical approach which solves on a computer the 100 or so simultaneous differential equations which describe nucleation. This approach avoids the numerous mathematical approximations of Kantrowitz, Probstein, and Collins. The customary kinetic and thermodynamic assumptions of the classical liquid-drop theory of steady-state nucleation were used. The times for the concentration of the nucleus of liquid water to reach 95% of steady state at —10°, —40°, and —60°C are 1.4, 19, and 27 μsec with supersaturations of 5, 10, and 20, respectively, and are only 10% longer than the ``time lags'' estimated by the approximate methods. Since the surface tensions of small clusters and the accommodations coefficients are unknown, the approximate methods, although incorrect by greater than 100%, are sufficiently accurate for most purposes. The results of Frisch are shown to be incorrect. The steady-state concentrations of water clusters are equal to their equilibrium concentrations for clusters which contain up to about 15 and 5 molecules less than the nucleus at —10° and —60°, respectively. Contrary to general opinion, the equilibrium concentrations of liquid-drop clusters do not decrease sharply in the vicinity of the nucleus.
Kinetics of Condensation of Water Vapor
Authors: Courtney Welby G.
Published: January 2005

The condensation of water vapor via steady-state nucleation is examined by an exact mathematical approach which solves the kinetic equations on a computer. This approach avoids the usual assumption that nucleation abruptly stops when the parent phase becomes slightly depleted. The corrected classical theory of steady-state liquid-drop homogeneous nucleation and the growth law used in the classical nucleation theory were assumed. Results gave no indication of a ``critical'' supersaturation for condensation and showed that condensation via classical homogeneous nucleation would be much slower than experimentally observed in cloud chambers. Condensation in 50 msec via homogeneous nucleation theoretically requires 13 particles/cc and an initial supersaturation of 5.2 at —5°C and 3.3×104 particles/cc and an initial supersaturation of 35 at —60°. Nucleation rates are sensitive to supersaturation but at —60° one-third of the particles are formed after a 4% decrease in supersaturation, contrary to the usual interpretation of condensation kinetics in a cloud chamber. The rapid condensation rates experimentally observed in a cloud chamber may be due either to heterogeneous nucleation or to homogeneous nucleation with the surface energy of an 80- or 90-molecule cluster being smaller than the macroscopic value, e.g., about 3 and 30% smaller at —5 and —60°, respectively. However, the liquid-drop theory of homogeneous nucleation as classically formulated in terms of the macroscopic surface energy apparently cannot explain the experimental results in a cloud chamber and thus remains to be verified.
Collision-Induced Microwave Absorption in Compressed Gases. II. Molecular Electric Quadrupole Moments
Authors: Birnbaum G. , Maryott A. A.
Published: January 2005

A search for dielectric loss in the nondipolar gases, He, Ar, CH4, SF6, H2, C2H6, N2, and C2H4 was made at a frequency near 24 kMc and for densities not exceeding 100 amagat. For the first six gases, the loss factor was immeasurably small, less than 2×10—7, at the maximum density. The loss observed in nitrogen and ethylene is attributed to transient dipoles induced by the molecular quadrupole fields during binary collisions. From the data on the quadrupolar gases, including previous results on CO2, values of the quadrupole moments (or upper limits where no loss was observed) are derived which are in reasonable agreement with other estimates.
Infrared Spectrum of CO Chemisorbed on Iron
Authors: Blyholder George
Published: January 2005

The infrared spectrum of CO chemisorbed on iron has been obtained in the 270 to 5000 cm—1 range. Two absorptions were found, one at 580 cm—1 and one at 1950 cm—1. From a vibrational analysis of five possible surface complexes, it is concluded that the observed spectra best fits the structure Fe=C=O, where the iron atom is part of the metal lattice. Force constants calculated for the Fe–C and C–O bonds, respectively, are 4.1 and 13.9 md/A. Comparison of these force constants with others suggests that both bonds are approximately double bonds. Use of empirical rules by Pauling and Badger both give an iron carbon bond length of about 1.67 A.
Double-Oven Experiments with Lithium Halide Vapors
Authors: Berkowitz J. , Tasman H. A. , Chupka W. A.
Published: January 2005

A double-oven apparatus described here has been operated within a mass spectrometer. By independently controlling the pressure and temperature of the vapor in the oven, the fragmentation patterns and relative ionization cross sections of the components of a complex vapor phase may be distinguished. Superheating the vapor and thereby producing species of lower molecular weight simplifies the mass spectrum and minimizes confusion due to fragmentation effects. This technique has been applied to the lithium halide vapors. Fragmentation patterns, ionization cross sections of dimers relative to those of the monomers, and energies of dimerization are reported.
Photolysis of Acetone in the Presence of HI and the Decomposition of the Acetyl Radical
Authors: O'Neal Edward , Benson Sidney W.
Published: January 2005

Acetone over a range of pressures and temperatures (1.2–15 cm Hg; 126–295°C) was photolyzed with light of 3130 A in the presence of small amounts of hydrogen iodide. The primary process was found to be the C–C split to form acetyl and methyl radicals. Hydrogen iodide acted as an excellent radical ``trap'' for these radicals. No spontaneous decomposition of acetyl radicals was observed. Relative rates of methyl radical reactions with iodine and hydrogen iodide were measured. Complications due to surface effects in these reactions are considered.

Kinetic constants for the reactions CH3+HI→CH4+I(1); CH3+I2→CH3I+I(2) are E1—E2=1.3±0.5 kcal, A2/A1=2.4, and log(k1/k2) = —0.38–1300/4.575T.

Above 200°C the acetyl radical decomposition is measurable and the rate constant is observed to be pressure dependent. The pressure dependence is treated by an approximate method related to the Hinshelwood-Lindemann equation and the high- and low-pressure limiting rate constants are given by logk∞=10.3–15 000/4.575T sec—1, logk0=11.5–12 000/4.575T (l/mole-sec). The number of vibrational modes S contributing to the decomposition is 4.5 and the lifetime of the excited acetyl radical is t∼10—8 sec. The abnormally low frequency factor of the high-pressure rate constant implies a nonadiabatic decomposition of the acetyl radical. From the kinetic constants, the heat of formation of the acetyl radical is found to be ΔHf0 (CH3CO)—6.2 kcal and the values of the appropriate bond dissociation energies in a series of acetyl derivatives are tabulated.
Polarization of T→S Emission Spectra of Azines
Authors: Krishna V. G. , Goodman Lionel
Published: January 2005

Polarization of the n←π* triplet-singlet emission bands have been determined for pyrazine and pyrimidine relative to the n→π*(1A→1W) and the first π→π*(1A→1Lb) absorption. The method consists in exciting into each absorption band separately and measuring the polarization of the resulting emission. The pyrazine emission is found to be polarized along the N–N axis and the pyrimidine emission along the axis that cuts through the bonds (x, in Fig. 1). The agreement with the theory is in two respects. In the theory the general prediction of in-plane polarization for the n↔π* triplet-singlet transitions comes out of the difference of the symmetry properties of the singlet and triplet spin functions. The specific prediction along the N–N axis for the pyrazine n↔π* triplet-singlet transition comes from the symmetry properties of the spin-orbit coupling operator. These predictions are independent of the form of the MO's and the operator chosen. The agreement with these predictions constitutes, then, an experimental verification of spin-orbit coupling in phosphorescence spectra. The prediction of the polarization along the x axis (Fig. 1) for the pyrimidine emission comes from the molecular orbital theory. However, the basic reason for this prediction lies in the pyrimidine (π, π*) state wave functions retaining their benzene character. The agreement with this prediction shows the validity of such an approach.
Vibration-Rotation Spectra of BrCN
Authors: Maki Arthur G. , Gott C. Thomas
Published: January 2005

The vibration-rotation structure of the infrared absorption bands due to ν21+ν3, 2ν20+ν3, and ν1+ν3 have been observed and measured for Br79CN and Br81CN. The average value of α3 for these two isotopic molecules was found to be +0.000677 cm—1. The Fermi resonance constant for the resonance diad was calculated to be W12=35.41 cm—1 for Br79CN and W12=35.48 cm—1 for Br81CN. The positions of the Q branches of a number of other bands were also measured.
Structure of fn Configurations. I. Calculation of the Energy Levels
Authors: Wybourne B. G.
Published: January 2005

In the first of a series of papers on the structure of fn electron configurations the calculation of the energy matrices and the construction of the energy level schemes are discussed together with the approximations that such calculations involve. Several new calculations are reported.
Near-Ultraviolet Absorption Spectrum of Tetrolaldehyde
Authors: Muirhead J. S. , Howe J. A.
Published: January 2005

The near-ultraviolet absorption spectrum of tetrolaldehyde vapor has been examined. The weak absorption appearing in the 300–400-mμ region has been assigned as the n→π* transition, and a vibrational analysis places the 0–0 transition at 26 620 cm—1 and yields a value for the C=O stretch frequency in the π* state of 1036 cm—1.

Two other regions of absorption are observed in the 200–300-mμ range, and one of these with center at 47 333 cm—1 is tentatively assigned as the N→V transition. The second of these appears as weak structure on the long wavelength edge of the first and may arise from a space forbidden π→π* transition.
General One-Center Two-Electron Integrals for Laguerre Functions
Authors: Browne J. C. , Miller James
Published: January 2005

There is presented a general formula for all one-center electron repulsion integrals over the orbital functions ψn,l,m(r)=(2β)32(n+l+1)![(n−l−1)!(n+l+1)!]12×(2βr)lLn+l+12l+2(2βr)exp(−βr)Ylm(θ,φ).