bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Chemiluminescence of Atomic-Oxygen—Hydrocarbon Reactions. Formation of the Vaidya Hydrocarbon Flame Band Emitter
Authors: Fontijn Arthur
Published: January 2005

A kinetic study of the Vaidya hydrocarbon flame bands emitted in the O–C2H2 reaction has been performed in a conventional fast-flow system at about 300°K. The effect of the free-radical scavengers NO and O2, as well as various other additives, has been studied. The emitter appears to have a direct precursor which is formed in the reaction sequence before the direct precursors of the other near-ultraviolet and visible-light emitters and the chemi-ions. Previously suggested mechanisms for formation of the Vaidya band emitter are critically evaluated. The reactions O+CH2(X3Σg−, vibrationally excited)→CHO*+H and/or O+C2H2O*→CHO*+CHO best explain the results.
Crystal Structure of O2PtF6: A Neutron-Diffraction Study
Authors: Ibers James A. , Hamilton Walter C.
Published: January 2005

The structure of O2PtF6 has been refined using neutron-diffraction data from a polycrystalline sample. The O–O bond length has not been determined with high precision owing to the probability of dynamic or static disorder of the O2 groups. O–O distances in the range 0.9 to 1.4 Å are compatible with the data if a suitable model is chosen for the disorder. Thus, although the data are compatible with the probable formulation as O2+PtF6−, other formulations cannot be eliminated. All models display interionic distances O···F of 2.5 Å or less. These distances are indicative of strong interionic attractions and may be responsible for the stability of the compound. The PtF6− ion is a regular octahedron with a Pt–F bond length of 1.82±0.03 Å.
Normal-Coordinate Analysis and Molecular Properties of Four CH2XY Halomethanes (X = F or I; Y = Cl or Br)
Authors: El-Sabban M. Zaki , Danti Alfred , Zwolinski Bruno J.
Published: January 2005

A normal-coordinate treatment for the series CH2XY halosubstituted methanes (X = F or I; Y = Cl or Br) was carried out with a 709 digital computer and a perturbation program supplied by Schachtschneider of the Shell Development Company. A reasonable set of potential constants was obtained for each molecule that reproduced exactly the observed fundamentals. Trends that were noticed among the potential constants of the obtained sets were demonstrated and discussed. The potential-energy distributions for each molecule were calculated. The effect of the redundancy on the quadratic potential constants as well as an estimate of the first-order potential energy constants were obtained according to the method of Crawford and Overend. In the present work, the assignments of the ν3 and ν8 fundamentals of the two iodinated compounds, as given by Pitzer and Gelles, were interchanged and the argument for this change was given. A new value for the unperturbed ν5 of the fluorobromomethane, which is undergoing a Fermi resonance with 2ν6, was adopted. This new value, higher than that adopted by Pitzer and Gelles, is backed by the results of the normal-coordinate treatment. Mean-square amplitudes of vibration for bonded and nonbonded atoms for the four molecules, as well as the Coriolis coupling coefficients were calculated. With the adopted values of the fundamentals, the usual ideal-gas thermodynamic properties were calculated for the four compounds based on the latest values of the physical constants and the carbon−12 atomic mass scale.
Nuclear Spin—Lattice Relaxation in Ferroelectric Triglycine Sulfate
Authors: Blinc R. , Lahajnar G. , Pintar M. , Zupančič I.
Published: January 2005

The temperature and frequency dependence of the 1H and 19F spin—lattice relaxation times in TGS, TGSe, and TGBe have been measured both in the ferroelectric and nonferroelectric phases, using a pulse technique. The results show that though a considerable slowing down of the proton motion occurs at the Curie points, the characteristic frequencies of internal motion are, in this range, still greater than the nuclear Larmor frequencies. The changes in the linewidth observed at certain orientations in the 1H and the additional splittings in the deuteron spectra on going to the ferroelectric phase are thus not due to a freezing in of internal motion but rather to a static rearrangement of the glycine units.
Vibrational Assignment of Anthracene-d10 from the Fluorescence and Absorption Spectra
Authors: Bree A. , Katagiri S. , Suart S. R.
Published: January 2005

The fluorescence and absorption spectra of anthracene-d10 in a fluorene matrix at 4.2°K have been measured and analyzed. In the ground electronic state seven ag and two b3g fundamentals have been assigned, while in the first-excited electronic state (1B1u) six ag and four b3g fundamentals were located. Other possible fundamentals are indicated. Earlier data concerning ag and b3g fundamentals of anthracene-h10 are critically reviewed and compared with the present results.
Observations on the Yellow Nitrogen Afterglow Bands at Low Pressure and the Radiative Lifetimes of the B 3Πg and A 3Σu+ States of Nitrogen
Authors: Brennen W.
Published: January 2005

The rotational profile of the (11, 7) first positive band in active nitrogen is shown to be pressure dependent in the range 0.05 to 1.0 torr. The effect is ascribed to rotational relaxation of nitrogen molecules in the B 3Π(v=11) level, and this interpretation leads to an estimation of tentative lower limits to the radiative lifetimes of B 3Π(v=11) and A 3Σ(v=0) of (2.4±0.5)×10−6 sec and 12±2.4 sec, respectively.
Assignment of the Ultraviolet Mystery Band of Olefins
Authors: Robin M. B. , Hart Robert R. , Kuebler N. A.
Published: January 2005

The weak mystery band found in the mono-olefins at 5–6 eV is here reassigned as a symmetry-allowed π→CH*(1Ag→1B2u) transition in which the CH* sigma upper orbital has considerable ns Rydberg character. Evidence supporting this assignment and militating against the recent CH→π*(1Ag→1B3g) assignment of Berry [J. Chem. Phys. 38, 1934 (1963)], the only other plausible assignment, is drawn from (a) ab initio calculations of the electronic spectrum and orbital energies of ethylene in large Gaussian bases, (b) a study of the intensities and vibronic band shapes of the mystery bands of cis—trans pairs of dialkylethylenes, (c) the observed effect of ring strain on the mystery-band intensity, (d) a measurement of the Cotton effect and rotational strength of the mystery-band transition, and (e) the spectra of olefins in condensed phases which demonstrate the Rydberg nature of the mystery-band upper state. Evidence is also presented that shows that the first electron affinity of ethylene places an electron in the CH* orbital, rather than in the π* orbital, as previously assumed. The implication of this low-lying π→σ* transition for the common assumption of π—σ separability is mentioned, and the importance of the almost certain presence of relatively low-lying π→σ* transitions with out-of-plane polarization in hydrocarbons of all sizes is stressed.
Continuous Representations in the Statistical Theory of Electronic Energies. The H2+ Ion
Authors: Handler George S. , Golden Sidney
Published: January 2005

A version of the statistical theory of electronic energies, arising from a consideration of alternative partitionings of the Hamiltonian, has been applied to the H2+ ion, yielding electronic energies ∼6% greater in magnitude than the exact theoretical values at several values of the internuclear separation. The binding energy at the theoretical equilibrium separation was calculated to be 0.1024 a.u. compared to the experimental value of 0.1026 a.u.
Constrained-Variation Method in Molecular Quantum Mechanics. Comparison of Different Approaches
Authors: Chong D. P. , Rasiel Yecheskel
Published: January 2005

Numerical results are presented for the lithium hydride molecule, obtained by different techniques of the constrained-variation method. The constrained wavefunction, the degree to which the constraint is satisfied, and the sacrifice in energy are compared. The constraint operator used was the electronic dipole moment in one case and the total Hellmann—Feynman force in another. In both cases, the parametrization procedure in the direct solution approach (Method I B) was found to be superior.
LCAO–SCF Computations for Hydrogen Peroxide
Authors: Kaldor U. , Shavitt I.
Published: January 2005

SCF—LCAO wavefunction calculations with a minimal basis set were performed for H2O2 at a series of seven different dihedral angles, as well as for a modified form, H2–O–O. The multicenter integrals were computed to an accuracy of about 0.00002 a.u. The internal rotation barriers obtained were 2.2 kcal/mole through the trans position and 11.8 through cis, compared with the best experimental values of 1.1 and 7.0 kcal/mole, respectively. Dipole moments, ionization energies, and electron-distribution data were also obtained.
Coriolis Interaction in the ν1 and ν3 Fundamentals of Ozone
Authors: Clough Shepard A. , Kneizys Francis X.
Published: January 2005

The v1 and v3 vibration rotation spectrum of 16O3 in the 9.0-μ region has been analyzed. The two vibrational states are coupled through a Coriolis term, iY13Py, and a second-order distortion term, −X13(PxPz+PzPx), in the Hamiltonian. The interaction has been treated by numerically diagonalizing the secular determinant for the two states with the coupling included. The effect of the interaction on the intensities has been considered and absorption contours calculated in satisfactory agreement with experiment. With the distortion parameters fixed to the ground-state values the following constants have been obtained: ν1=1103.157, A1=3.5569, B1=0.44272, C1*=0.39262, ν3=1042.096, A3=3.5004, B3=0.44125, C3*=0.39097, Y13=−0.466, and X13=−0.0098 cm−1. The value of the dipole-moment ratio, (∂Mz∂Q3|0Q3)⧸(∂Mx∂Q1|0Q1),is 10.0±1.5.
Monte Carlo Calculations of Cross Sections of Electron—Positive-Molecular-Ion Dissociative Recombination
Authors: Wilkins Roger L.
Published: January 2005

In a recent paper Bauer and Wu proposed a model which was self-consistent for the application of perturbation theory to the problem of calculating the general order of magnitude of cross sections of electron—positive-molecular-ion dissociative recombination. In applying their model to the calculation on a hypothetical system of electron capture by molecular hydrogen ions it was necessary to make several approximations, without which it would have been exceedingly difficult to evaluate certain matrix elements. We show here that Monte Carlo methods can be used for evaluating these matrix elements without resorting to approximations other than the model itself. The Monte Carlo method of stratified sampling has been tested successfully on the problem of capture of electrons by molecular hydrogen ions. The dissociative recombination coefficient is found to be of the order of 3×10−8 cm3/sec at room temperature, which is in excellent agreement with reported experimental results.
Vibronic Coupling in ESR Spectra of Triplet States in Molecules: Temperature Effects
Authors: Marechal Yves
Published: January 2005

The vibronic coupling between triplet exciton and nuclear motions is studied in two limiting cases: (1) exciton localized on a part of a molecule (trimers, dimers) and (2) exciton ``delocalized'' over a molecule (such as coronene). In both cases, the effect of temperature upon ESR spectra is treated. This temperature dependence results from the trapping of the exciton, either in one component of the trimer (localized states), or in a deformed state of the molecule (delocalized state). In the latter case, the nuclear vibrations are also important in mixing different electronic states. The theoretical results obtained are compared to experimental data on the lifetime of an exciton on one component of a trimer, Case (1), and on the temperature dependence of D (zero-field splitting) in molecules such as coronene, Case (2).
Infrared Spectrum of Carbon Dioxide Anion Radical
Authors: Hartman K. O. , Hisatsune I. C.
Published: January 2005

Pressed alkali halide disks of infrared spectroscopy have been used as matrices to trap and to stabilize the carbon dioxide anion free radical. The radical was generated by exposing disks containing the formate ion in solid solution to gamma rays from a cobalt source. The ESR, the ultraviolet, and the infrared spectra of the radical have been identified. From the carbon−12 and −13 isotopic frequencies of the antisymmetric CO-bond stretching infrared band, a valence angle of 127°±8° was calculated for this radical. The radical reacted with water to produce bicarbonate and formate ions.
Ultraviolet Absorption and Excitation Spectrum of Ruby and Sapphire
Authors: Loh Eugene
Published: January 2005

The absorption spectrum of thin samples of ruby with 0.5 to 0.005 wt. % of Cr2O3 has been measured up to 8.9 eV at room temperature with linearly polarized light. The spectrum shows an absorption peak at 7 eV followed by humps around 8 eV with absorption cross section and oscillator strength at the 7-eV peak ∼7×10−17 cm2 and ∼0.3, respectively. The absorption with E⊥c is generally larger than E| | c in the vacuum-uv region. The absorption between 6.8 and 8.6 eV is interpreted as a charge-transfer transition around the chromium ion because of its large oscillator strength and some similarity to the ultraviolet reflectance spectrum of Al2O3 crystal.

The excitation spectrum of ruby cubes with several chromium concentrations has been measured to 11 eV at room temperature with linearly polarized light. Structure and polarization effects corresponding to those of the absorption spectrum are observed. The quantum efficiency in the region 7 to 9 eV is comparable to that in the blue absorption band of ruby and is essentially concentration independent. Above 9 eV the relative quantum efficiency drops about two orders of magnitude and is concentration dependent, with low quantum efficiency for samples of low chromium concentration. Similar spectra on sapphire are also included for comparison.
Restricted Motion of β Protons of the HOOC–CH2–CH–COOH Radical Trapped in Urea Crystals
Authors: Corvaja Carlo
Published: January 2005

The ESR spectrum of the HOOC–CH2–CH–COOH radical, formed by γ-ray irradiation of a mixed crystal of urea—fumaric acid, was recorded at different temperatures. Analysis of the spectra shows that the radical undergoes some restricted torsion about the Cα–Cβ bond. A value of ∼2 kcal/mole was found for the energy barrier opposing this motion.
Unimolecular Decomposition of Negative Ions Formed from the Transition-Metal Carbonyls of Ni, Fe, Cr, Mo, and W
Authors: Winters Robert E. , Kiser Robert W.
Published: January 2005

Negative-ion mass spectra and dissociative electron-capture energetics for the principal metal-containing ions have been determined for nickel tetracarbonyl, iron pentacarbonyl, chromium hexacarbonyl, molybdenum hexacarbonyl, and tungsten hexacarbonyl. These data are utilized in the first application of the statistical theory of mass spectra to describe the unimolecular decompositions of negative ions. The mechanism proposed for the formation of the various M(CO)x− ions is an ion-pair production process followed by a series of consecutive ionic-unimolecular decomposition reactions involving the elimination of CO groups.
Electronic Structure of Diatomic Molecules. III. A. Hartree—Fock Wavefunctions and Energy Quantities for N2(X1Σg+) and N2+(X2Σg+, A2Πu, B2Σu+) Molecular Ions
Authors: Cade Paul E. , Sales K. D. , Wahl Arnold C.
Published: January 2005

The problem of the convergence of a sequence of Hartree—Fock—Roothaan wavefunctions and energy values to the true Hartree—Fock results is examined for N2(X1Σg+). This critical study is based on a hierarchy of Hartree—Fock—Roothaan wavefunctions which differ in the size and composition of the expansion basis set in terms of STO symmetry orbitals. The concluding basis set gives a total Hartree—Fock energy of −108.9956 hartree and Re(HF)=2.0132 bohr for N2(X1Σg+).

Results are also presented from direct calculations for three states of the N2+ molecular ion (X2Σg+, A2Πu, B2Σu+) which are also thought to be very close approximations to the true Hartree—Fock values. The results give EHF=−108.4079, −108.4320, and −108.2702 hartree and Re(HF)=2.0385, 2.134, and 1.934 bohr for the X2Σg+, A2Πu, and B2Σu+ states of N2+, respectively. Extensive calculations for various R values establish that the X2Σg+ and A2Πu states are reversed in order relative to experiment, a short-coming ascribed to the Hartree—Fock approximation.
Normal Vibrations and Intermolecular Forces of Crystalline Benzene and Naphthalene
Authors: Harada Issei , Shimanouchi Takehiko
Published: January 2005

The GF matrix method was applied to the analysis of band splittings and lattice vibrations of crystalline benzene. The far-infrared spectrum of crystalline naphthalene was measured in the region from 300 to 50 cm−1 and three infrared-active lattice vibrations were observed. A normal-coordinate treatment of the lattice vibrations of naphthalene was performed. Intermolecular force constants of nonbonded hydrogen—hydrogen pairs and hydrogen—carbon pairs were obtained.
Distribution of Charge on the Azide Ion in NaN3
Authors: Campbell I. D. , Coogan C. K.
Published: January 2005

The NMR spectrum of powdered NaN3 has been observed at room temperature and below. From this result the distribution of charge on the azide (N3−) ion, based on a simple point-charge model can be deduced to be −0.857e on the outer nitrogen atoms and +0.714e on the central nitrogen atom. This is to be compared with a previous theoretical estimate based on a molecular orbital approach of −0.83e on each of the outer nitrogen atoms. Using this ``experimental'' value for the charge distribution the lattice energy of NaN3 has been calculated on a term-by-term basis, yielding 178.2 kcal/mole, as compared with the experimental value of 175 kcal/mole, derived from the heat of hydration.
Low-Energy Atomic Collisions. I. The Schrödinger Equation for H+–H
Authors: Kouri Donald J. , Curtiss C. F.
Published: January 2005

The Schrödinger equation for the system H+–H is considered. After the usual separation of the center-of-mass coordinates, group theoretic methods are used to eliminate three degrees of freedom associated with the rotational motion of the system. This is done in a manner which treats the protons symmetrically, thereby enabling one to easily establish the symmetry character of the wavefunctions. The result is in a form which is convenient in the study of scattering.
Ferromagnetic and Crystal Structure of Ludlamite, Fe3(PO4)2·4H2O, at 4.2°K
Authors: Abrahams S. C.
Published: January 2005

A neutron-diffraction study of Fe3(PO4)2·4H2O below the Curie temperature has determined both the crystal and the magnetic structure. At 4.2°K, the crystal remains monoclinic, with lattice constants a=10.541±0.010, b=4.638±0.008, c=9.285±0.010 Å, β=100°43.7′±4.0′ and two formula weights in the unit cell. The nuclear and Shubnikov space groups are both P21/a. The iron—oxygen octahedral distances range from 2.019±0.010 through 2.317±0.010 Å, with average distance 2.154 Å. The phosphate group is very nearly a regular tetrahedron, with the phosphorus—oxygen distance ranging from 1.521±0.008 through 1.553±0.007 Å. The average O–H distance is 1.00 Å, and the shortest O–H···O bond is 2.546±0.005 Å. The magnetic unit cell coincides with the nuclear cell. The spins on each linear triad of iron atoms, separated by 3.267±0.004 Å, are ferromagnetically coupled and are essentially parallel. Triad spin components in the ac plane, related by the screw-axis or glide-plane operators, are antiferromagnetically coupled. Spin components parallel to the b axis are ferromagnetically coupled. The spins are very nearly normal to the a axis and are inclined 10° out of the ac plane, always in the same sense, forming a canted spin array. The magnetic moment per iron atom is 4.5±0.2 μB. The effective ferromagnetic moment, based on this spin array, is 0.81 μB in excellent agreement with Mays' NMR measurement.
Ionic Reactions in Gaseous Monosilane
Authors: Hess G. G. , Lampe F. W.
Published: January 2005

The ions SiH3+, Si2H+, Si2H2+, Si2H3+, Si2H4+, and Si2H5+ appear as products in ionized SiH4. All are formed from the attack of SiH2+ ions on SiH4 molecules. The specific reaction rates for the formation of these ions are, in units of cubic centimeters per moleule·second×1010, respectively, 1.7, 0.13, 0.67, 0.39, 1.1, and 0.068.
Optical Properties of Polystyrene in the Vacuum Ultraviolet
Authors: Carter J. G. , Jelinek T. M. , Hamm R. N. , Birkhoff R. D.
Published: January 2005

Measurements are reported of the optical properties of polystyrene in the wavelength region from 400 to 3000 Å. The real (n) and imaginary (k) parts of the complex index of refraction were obtained from reflectance measured at 20° and 70° incidence. The complex dielectric constant and the energy-loss function were determined from these values of n and k. The energy-loss function Im (1/ε), was found to exhibit maxima at 4.6, 5.2, 6.5, 8.5, and 19.2 eV. Sum rule calculations of the effective number of electrons per monomeric unit participating in these losses have been carried out.
Observation of Conformational Isomers of the Tetraisopropylnitrobenzene Anion Radical by Electron Spin Resonance Spectroscopy
Authors: McKinney Ted M. , Geske David H.
Published: January 2005

The electron spin resonance spectrum of the anion radical obtained by electroreduction of 2,3,5,6-tetraisopropylnitrobenzene has been studied extensively. The spectrum is interpreted in terms of two discrete conformational isomers existing in thermodynamic equilibrium. The isomeric difference arises from concerted interaction of the ring substituents which allows the nitro group to assume two different angular orientations with respect to the plane of the ring. These orientations are manifested as two different 14N isotropic coupling constants. In acetonitrile solution these values are 23.6 and 22.0 G for the more- and less-twisted conformers, respectively. An apparent equilibrium constant for interconversion is defined and evaluated under a wide variety of solvent and temperature conditions. The free energy of conversion from the more- to the less-twisted conformation is estimated as ΔG298° = −5±1×102 cal mole−1 in acetonitrile. A necessary condition for the proposed equilibrium is that both species decay at the same rate and this condition is observed experimentally.

2,4,6-Tri-isopropylnitrobenzene anion radical was also studied. The nitrogen coupling constant was 20.6 G in acetonitrile, but no conformational isomerism was observed presumably because of the absence of buttressing 3,5-substituents.
Shock-Tube Study of the Hydrogen—Oxygen Reaction. II. Role of Exchange Initiation
Authors: Ripley Dennis L. , Gardiner W. C.
Published: January 2005

An extended analytical solution to the rate equations for the branching-chain reactions of the H2–O2 reaction under shock-tube conditions is presented. Together with an experimental determination of the detection threshold for OH of the Bi (3067) line-absorption method used in earlier experiments, this solution allows quantitative comparison of calculated and experimental ignition delays. It is shown that calculation and experiment can be brought into agreement with slight modification of chain-reaction rate coefficients deduced from the results of other studies of the H2–O2 reaction. The essential role of the rate of chain initiation by a path other than diatom dissociation in determining the ignition delays is brought to light. Rate-coefficient expressions for the chain reactions are suggested and supported.
Operator Form for the Linear and Quadratic Jahn—Teller Coupling in Octahedrally Coordinated Eg Electronic States
Authors: Coffman Robert E.
Published: January 2005

The operator form for the linear and quadratic Jahn—Teller effect in octahedrally coordinated Cu+ + is derived by consideration of the simultaneous effect of three tetragonal distortions. This leads to the same result as found by Liehr and Ballhausen, but in fewer steps. The final form of the operator is independent of the choice of phase of symmetrized distortion coordinates.
Adsorption and Oxidation of Carbon Monoxide on Clean Films of Palladium and Nickel
Authors: Kawasaki Koji , Sugita Toshio , Ebisawa Shigeo
Published: January 2005

The adsorption and surface reaction of carbon monoxide and oxygen on clean films of palladium and nickel at room temperature at pressures in the range of 10−9−10−2 torr were studied by means of mass spectrometer and by measuring simultaneously electrical resistance.

CO preadsorbed on clean films of palladium and nickel reacted readily with gaseous O2 and no induction period was observed. Oxygen preadsorbed on palladium film immediately reacted with CO, but on nickel never reacted.

Some discrepancies between the results and those in the literature were discussed.
Effect of Paramagnetic Impurities on Proton Spin—Lattice Relaxation Time in Methane
Authors: Sandhu H. S.
Published: January 2005

Measurements of the proton spin—lattice relaxation time T1 were carried out in samples of CH4 from 110°—90°K having an oxygen concentration of 1.08% and 2.54%, respectively. The results verify the inverse proportionality of T1 and oxygen concentration.
Molecular Structure of CCl3NO2 by Electron Diffraction
Authors: Knudsen R. E. , George C. F. , Karle J.
Published: January 2005

The structure of chloropicrin, an unstable compound, has been studied by electron diffraction, using the sector-microphotometer method. Final parameters have been obtained by means of a least-squares fit of a structural model to the experimental intensity curve. The structure is similar to those found previously for fluoropicrin and bromopicrin. The −CCl3 group and the N–O bond have the expected values for bond lengths and angles. However, the C–N distance is very long, 1.594 Å; the ONO angle is 131.7°; the −CNO2 group is not planar; and the molecule assumes a staggered conformation similar to that found in ethane compounds with one position vacant. On the basis of a potential function of the form V=12V0(1−Acos3φ−Bcos6φ), where 0.75≤A≤1.0 and A+B=1, a barrier of 2.70–3.35 kcal/mole hindering free rotation about the C–N bond has been found.
Thermal Decomposition of Azomethane. II. The Unimolecular Reaction on the Quantum Harmonic Model
Authors: Forst W.
Published: January 2005

The decomposition of azomethane is a complex process, but previous work has shown that the residual, fully NO-inhibited reaction has all the features of a unimolecular reaction. This residual reaction is now treated by the quantum harmonic version of the Marcus—Rice theory of unimolecular reactions. Extrapolation to infinite pressure gives log10k∞=17.32 — 55 500/2.303 RT. In accordance with the high pre-exponential factor (and hence high entropy of activation) a very loose activated complex is postulated involving free rotations of the two methyls and the central nitrogen. Two models of this complex are considered: one having a planar methyl and the other a tetrahedral methyl. From the pre-exponential factor there are deduced six more active rotations in the complex than in the molecule. Exact vibrational—rotational energy sums are evaluated on a computer, as is the rate constant integral itself. Within the relatively large experimental error, and subject to the uncertainty in collision diameter and collisional deactivation efficiency, good pressure fit between theory and experiment in the rate constant pressure fall-off is obtained for a theoretical model having nine or more active rotations in the complex and three or more in the molecule. It turns out that the vibrational frequency pattern of the complex is so much less important than the number of active rotations that both models for the complex, tetrahedral or planar, lead to identical fall-off behavior. Theory also predicts an activation energy fall-off with pressure that is, on the whole, in accord with the rather limited experimental data.
Infrared Spectrum, Structure, and Bonding of Lithium Nitroxide, LiON
Authors: Lester W. , Andrews S. , Pimentel George C.
Published: January 2005

Lithium nitroxide has been formed through reaction of lithium atoms and nitric oxide in solid argon at high dilution. Isotopic substitutions at all atomic positions verify the molecular identity and furnish an ample basis for normal-coordinate analysis. The data indicate the molecule is bent (100°±10°), and they favor the molecular formula LiON (rather than LiNO). Potential constants kNO=7.97 mdyn/Å, kLiO=1.33 mdyn/Å, kα=0.54 mdyn·Å/rad2, and kLiO,α=0.39 mdyn are obtained. The force constants can be correlated to those of other molecules with the aid of the electronegativity of lithium. The bonding is not readily explained; the NO bond has a bond order near 1.7, significantly weaker than that in HNO.
Ionic Processes in γ-Irradiated Organic Solids: Positive-Hole Migration in 3-Methylpentane
Authors: Gallivan James B. , Hamill William H.
Published: January 2005

The yields of positive and negative species trapped in γ-irradiated organic glasses at −196° have been measured as a function of glass composition. Increased yields of solvent-trapped electrons (e−) and biphenyl anions (φ2−), as well as decreased yields of various solute cations (A+), were noted when additives capable of undergoing charge-transfer or proton-transfer reactions were present in small amounts (<2 mole %) in 3-methylpentane (3MP). All results can be understood qualitatively in terms of the mobile positive hole being transferred from 3MP to these additives and trapped. A simple scheme of competition for the total available number of positive holes accounts for the decrease in A+ when a second solute (B) is added and relative cross sections to form A+ and B+ can be determined. Additives affect the optical absorption spectrum of (e−) in 3MP. The spectra of the biphenyl positive and negative ions are similar but displaced, while the anion and cation from benzene are anomalous in 3MP glass. The rates of decay of N,N,N′,N′-tetramethyl-phenylenediamine cation and of (e−) are compared following γ irradiation and photoionization of the amine in 3MP. Very efficient attachment of photoelectrons by φ2 indicates an average track volume >10−18 cc.
Intermolecular Obstruction in Rubber Elasticity Theory
Authors: Jackson Julius L. , Shen Mitchel C. , McQuarrie Donald A.
Published: January 2005

The leading term of the equation of state of rubber relating elongation to stress may be obtained by treating the polymer chains in the rubber as independent and distributed according to the laws of Brownian motion. A great deal of theoretical work has been done on corrections to this simple picture, particularly in consideration of the finite extensibility of the chains and the network character of their connections.

In this paper we attempt to take into account the fact that in the rubber there is a high density of chains which causes mutual obstruction among the chain Brownian motions. In the unstrained, symmetric state the obstruction is isotropic; however, when the rubber is stretched, the degree of obstruction will be different in different directions. An equation is obtained for the dependence of free energy on this anisotropic effect. The theoretically derived stress—strain equation is compared with experimental results.
Magnetic Resonance Studies on Copper(II) Complex Ions in Solution. I. Temperature Dependences of the 17O NMR and Copper(II) EPR Linewidths of Cu(H2O)62+
Authors: Lewis W. Burton , Alei Mohammed , Morgan L. O.
Published: January 2005

The temperature dependences of copper (II) EPR and 17O NMR spectra are analyzed in terms of a tetragonally distorted Cu(H2O)62+ ionic species in which only the equatorial water molecules form strong σ bonds to copper (II). By reconstructing the EPR spectra at temperatures in the range −10° to 100°C, the contributions to the linewidth from spin—lattice relaxation, tumbling of an ionic complex having an anisotropic g factor and an anisotropic hyperfine coupling constant, and from isotropic hyperfine splitting, are separated. It is found that the spin—lattice relaxation time T1e has components from both spin—rotational and Van Vleck processes. The 17O NMR linewidth is due to scalar hyperfine interaction with the copper (II) electron spin, and the spin-exchange correlation time τe for this mechanism is determined over the same temperature range. While T1e and τe have similar temperature dependences, τe is 6–8 times smaller than T1e, suggesting that it may be related to inversion of tetragonal distortion in the complex, rather than to electron relaxation.
Self-Diffusion in Dense Fluids
Authors: Stillinger Frank H. , Suplinskas Raymond J.
Published: January 2005

The time-dependent solutions to the low-order BBGKY hierarchy are examined for the case of inter-diffusion of two mechanically identical isotopes. In order to effect a closure directed at evaluation of the pair-distribution-function perturbations and the self-diffusion constant D, we invoke a dynamical superposition approximation, and a truncated expansion in inverse powers of the initial composition fluctuation wavelength. The potential feasibility of this general approach to calculation of dense-fluid transport properties is illustrated by explicit numerical calculations for the dense fluid of rigid spheres, using in addition a pair-space local equilibrium assumption. Although the resulting pair-distribution-function perturbations seem to be in accord with physical intuition, cumulative errors in the approximation sequence render the self-diffusion coefficients predicted at variance with other calculations. Systematic improvements of the present scheme are outlined.
High-Temperature Equilibrium in the Germanium—Nickel System and the Dissociation Energy of GeNi
Authors: Kant Arthur
Published: January 2005

The GeNi molecule has been shown to exist in the vapor phase over liquid solutions of germanium and nickel above 2000°K.

Using information derived from a combination of effusion and mass-spectrometric techniques, the energies and equilibrium constants of the gaseous reactions GeNi+Ge=Ge2+Ni and GeNi=Ge+Ni have been calculated. The values of the energy assuming a 1Σ ground state of GeNi are GeNi+Ge=Ge2+NiΔE0∘=1.6±4 kcal,GeNi=Ge+Ni  D0∘(GeNi)=66.4±4 kcal.

The dissociation energy of Ge2 was also determined and the value of D0°(Ge2) of 64.9±3 kcal confirms results obtained previously.
Application of the Franck—Condon Principle to Molecular Excitation by Collision with Excited Atoms and Molecules
Authors: Robertson W. W.
Published: January 2005

The intensity distribution has been observed in band spectra emitted by molecules selectively excited in collision with excited atoms and molecules in helium and argon afterglows for Penning-type reactions, charge-transfer, and resonance reactions. It was found that the distribution of intensity was generally attributable to a population distribution over the vibrational levels of the excited state that followed the Franck—Condon factors for excitation from the ground state of the molecule. No marked enhancement of population corresponding to close energy resonance was observed.
Neutron and Infrared Spectra of HCrO2 and DCrO2
Authors: Rush J. J. , Ferraro J. R.
Published: January 2005

The vibrational spectra of HCrO2 and DCrO2 have been investigated by the energy-gain scattering of cold neutrons, and by infrared absorption spectra from 4000–30 cm−1. The infrared measurements are in agreement with previous results above 300 cm−1. In addition, no absorptions are observed between 300 and 30 cm−1, a region not covered in previous measurements. These results appear to support previous evidence for asymmetric hydrogen bonds in DCrO2 and essentially symmetric bonds in HCrO2. The neutron spectra exhibit a number of maxima, including a band peaked at about 225 cm−1 in HCrO2 (and a less intense peak around 180 cm−1 in DCrO2), probably due to low-frequency optic lattice modes. A comparison of the neutron and infrared results appears to raise some uncertainty concerning the assumption of symmetric hydrogen bonds in HCrO2.
Structure of Cubic Ammonium Fluosilicate: Neutron-Diffraction and Neutron-Inelastic-Scattering Studies
Authors: Schlemper Elmer O. , Hamilton Walter C. , Rush J. J.
Published: January 2005

The motion of the ammonium ion in the cubic phase of (NH4)2SiF6 has been investigated by the inelastic scattering of slow neutrons. The prominent feature of the neutron energy-gain spectrum is a moderately broad band peaked at 168±8 cm−1 with a shoulder at 305±25 cm−1. These are assigned to the 1–0 and 2–0 transitions of a rotational motion of the ammonium ion.

A precision refinement of single-crystal neuron-diffraction data has also been completed. There is a well-defined disorder of the ammonium groups. Although a model with a static threefold disorder, with each ⅓ hydrogen atom undergoing harmonic vibration gives a very satisfactory fit to the data, such a model is probably unrealistic in view of the fact that the disordered positions are only 0.75 Å apart. A more realistic model is one involving an ordered hydrogen atom undergoing thermal motion in a very anharmonic potential well. We propose a model in which the hydrogen atom is relatively free to move over a region of about 1 Å2 by small rotations of the ammonium ion but with a very high barrier toward a reorientation which involves an interchange of two hydrogen atoms. Such a model is an agreement with both the neutron-diffraction and the inelastic-scattering data.

The hydrogen-atom positions found in the diffraction study do not agree with those reported by Vainshtein on the basis of an analysis of the electron-diffraction data. The N–H bond length is not well defined because of the uncertainties regarding the thermal motion. An uncorrected mean atomic separation of 0.985 (σ=0.007) is obtained; the actual bond length is about 0.08 Å longer. The SiF62— ion is a regular octahedron with a corrected bond length Si–F=1.696 (σ=0.003).
Covalency Parameters and the g Factor for Ni2+: KMgF3
Authors: Li Huang Nai , Šimánek E.
Published: January 2005

The covalency parameter λπ in the excited state of Ni2+:KMgF3(d8,t25eg3) is determined from the experimental EPR values for the g shift, λσ, and λs in the ground level (d8,t26eg2). The procedure involves evaluation of small terms in the orbital reduction factor kσπ, which have hitherto been neglected and which can contribute significantly in more covalently bonded salts. The contribution to the g shift coming from an electron-transfer process is given for Ni2+:KMgF3 and included in the calculation of λπ. The value of λπ=0.35 obtained by this method is close to the EPR value for λσ=0.31 and indirectly supports the argument for cancellation of the spin densities in the σ and π orbitals of the fluorine ions in manganese salts. It is suggested that the large π bonding arises from the anion crystal-field splitting, which is important when the promotion energy for the electron transfer is sufficiently small.
Calculation of the Surface Tension of a Simple-Cubic Crystal According to Two Different Methods
Authors: Yun K. S. , Benson G. C.
Published: January 2005

A comparison is made of the surface tension of a simple-cubic crystal calculated according to two different methods: (i) from the variation of the surface free energy with surface area and (ii) from the surface-stress tensor.

A Lennard-Jones 12–6 potential is employed for the interaction between pairs of atoms and the effects of surface relaxation are investigated extensively. The numerical results show that the two surface tensions approach one another as the relaxation of the surface region of the crystal is extended further into the crystal.
Reduction of the Fourth-Order Asymmetric-Rotor Hamiltonian
Authors: Kneizys F. X. , Freedman J. N. , Clough S. A.
Published: January 2005

By use of the angular-momentum commutation relations, the fourth-order asymmetric-rotor Hamiltonian for molecules of orthorhombic symmetry has been considerably simplified. The number of rotational coefficients has been reduced to 19: three coefficients of second power, six coefficients of the fourth power, and 10 coefficients of sixth power in the angular momentum.
Franck—Condon Factors for the Ionization of H2 and D2
Authors: Dunn Gordon H.
Published: January 2005

Franck—Condon factors for ionization of H2(1Σg+) and D2(1Σg+) are presented for 19 levels in H2+(2Σg+) and for 27 levels in D2+(2Σg+). Comparisons are made with calculations, using less accurate potential functions for the molecular ion. Vibrational eigenenergies are given for D2+.
Microwave Spectrum of Germylacetylene
Authors: Thomas E. C. , Laurie Victor W.
Published: January 2005

The microwave spectrum of germylacetylene has been investigated in the region 7–36 Gc/sec. The rotational constants for the isotopic species 76GeH312C≡12CH, 74GeH312C≡12CH, 73GeH312C≡12CH, 72GeH312C≡12CH, 70GeH312C≡12CH, 74GeH313C≡12CH, 74GeH312C≡13CH, 72GeH313C≡12CH, 72GeH312C≡13CH have been determined to be 3553.78, 3572.40, 3582.04, 3591.97, 3612.55, 3531.69, 3423.48, 3551.60, 3442.89 Mc/sec, respectively. From these data the structural parameters rGeC=1.896 Å and rCC=1.208 Å are determined. If rCH is assumed to be 1.056 Å, then rGeH=1.521 Å and ∠HGeH=109.9°. Measurement of the Stark effect leads to a dipole moment of 0.136 D. Analysis of the hyperfine components of 73Ge transitions leads to a nuclear quadrupole coupling constant eQq of +32.5 Mc/sec.
Microwave Spectrum, Internal Barrier, Molecular Structure, and Dipole Moment of Disilanyl Fluoride
Authors: Cox A. Peter , Varma Ravi
Published: January 2005

The microwave spectra of five isotopic species of disilanyl fluoride (Si2H5F) have been studied in the region 12–38 Gc/sec. Several of the ground-state transitions are split into doublets, some into triplets, due to the coupling of internal and over-all rotation. Analysis of the splittings gives a barrier value V3 = 1048±40 cal/mole.

Rotational constants have been determined for molecules containing silicon−28, −29, and −30 isotopes in each position and have been used to calculate the following structure:  Si–F=1.598±0.008 Å, Si–Si=2.332±0.005 Å, Si–H=1.483 (assumed), Si–H(F)=1.477 Å (assumed),∠HSiH=180∘20′ (assumed),  ∠HSiH(F)=110∘2′  (assumed),∠SiSiF=109∘30′±30′,∠SiSiH(F)=110∘22′±2∘.

Stark-effect measurements yield μA = 0.934 D, μB = 0.850 D, and a total dipole moment μ = 1.26±0.01 D inclined at an angle of 10° to the SiF bond.
Nonstoichiometry in Uranium Dioxide
Authors: Thorn R. J. , Winslow G. H.
Published: January 2005

An extension of Anderson's formulation of the defect theory of nonstoichiometry is used with an oxygen—interstitial oxygen-vacancy model to calculate the composition of the uranium dioxide phase at the lower phase boundary and the relative partial molar thermodynamic functions for oxygen at compositions ranging from the lower phase boundary to UO2.08. The model is used as a basis on which to argue that differing experimental results near UO2.00 are more likely due to differing, nonequilibrium, concentrations of uranium vacancies than to failure to reach oxygen equilibrium. The present form of the model, with an interstitial site density of one per uranium site fails sharply at about UO2.08 rather than gradually as the oxygen content is increased from UO2.00. Discussion of the effects of alternate site densities is used to explain the observed values of the partial molar entropy of the oxygen in the range from UO2.02 to UO2.24.
Absorption of Sound Near the Critical Point of the Nitrobenzene—Iso-octane System
Authors: Anantaraman A. V. , Walters A. B. , Edmonds P. D. , Pings C. J.
Published: January 2005

Measurements by the pulse technique were made of the absorption of sound in the nitrobenzene—iso-octane system (Tc=30.2°C) over the full composition range, at temperatures of 30.5°C, 34.8°, and 44.8° for five frequencies between 4.5 and 16.5 Mc/sec. At the lowest frequency and at 0.3°C above the critical temperature, the absorption is anomalously large by a factor of 47; 14.6°C above Tc, the absorption is still in excess of classical predictions by a factor of 11. The data cannot be represented by a model involving only a single relaxation frequency. The Fixman theory is in reasonable, but not exact, agreement with the data with regard to functional conformity in temperature and frequency; in particular, the predicted frequency dependence, α/f2∝f−5/4, at the critical state is verified within experimental error. The Fixman theory and the data preclude anything but a simple pole at the critical temperature for the reciprocal square of κ, the exponential decay constant in the long-range correlation function. However, if it is assumed that κ2=6l−2(T/Tc−1)[1+a1(T/Tc−1)],the theory and experiment are in agreement over the full range of temperature and frequency, with a value of a1=0.0296.
Molecular Structure of (CF3)2PCl3: Infrared and Raman Spectra
Authors: Griffiths James E. , Beach Alexander L.
Published: January 2005

The basic structure of (CF3)2PCl3 has been established from a study of its vibrational spectrum (D3h point group). The CF3 groups occupy axial positions in a trigonal bipyramidal framework, but no direct information is obtained concerning the heights of the barrier to internal rotation. Molecular models indicate strong F···Cl steric interference and suggest a high barrier, however.

All of the active fundamentals are assigned in the Raman (Δν=50–1500 cm−1) and infrared (ν=33–2000 cm−1) spectra. Gas, liquid, and solution spectra were recorded. Fundamental frequencies are: a1′=1173, 739, 366, 237; a2″=1184, 748, 447, 254; e′=1150, 589, 534, 335, 186, 89; e″=1193, 539, 304, and 202 cm−1.

Unlike CF3PCl4, the trichloro compound, (CF3)2PCl3, is quite stable at 40°C and to irradiation by 4358-Å Hg light.
Reactions of Metal Carbonyls with Active Nitrogen
Authors: Brennen W. R. , Kistiakowsky G. B.
Published: January 2005

Ni(CO)4, Fe(CO)5, Cr(CO)6, W(CO)6, Mn2(CO)10, and Co(NO) (CO)3 were found to react very rapidly with active nitrogen, forming metal atoms. The reaction is accompanied by intense flames due to neutral metal atom emission spectra. The mechanism of the reaction is interpreted as a stepwise degradation: Me(CO)n+N→Me(CO)n−1+NCO. The excitation of emission spectra is shown to be most likely due to collisions of metal atoms (as they diffuse to the walls) with metastable A 3Σ nitrogen molecules. These are formed in the three-body atomic recombination reaction and have only short lifetimes due to destruction on the walls of the tubular flow reactor. Quantitative intensity measurements of Fe(I) and Ni(I) flame spectra yielded rates of excitation of numerous levels of these atoms. The relative rates are found to depend only on the excitation energy, decreasing monotonously as the energy increases. Atomic mercury emission in active nitrogen was also observed and measured, as well as its quenching by ammonia. The dependence of the excitation rates on energy is experimentally the same for nickel, iron and mercury, except that the excitation of the 7s1S0 mercury state, which conflicts with the spin conservation rule if the nitrogen molecules undergo the A 3Σ→X 1Σ transition, occurs about 10−2 as frequently as the energy relationship would predict. It is inferred that this relationship is largely determined by the relative populations of the successive vibrational levels of the A 3Σ nitrogen molecules as these cascade down due to inelastic collisions from the highest levels resulting from the three-body recombination processes.
Energy-Partition Parameters in Radiation Studies of Molecular Gases
Authors: Klots Cornelius E.
Published: January 2005

Ion-yield measurements in binary mixtures of 18 molecular gases are reported. They may be analyzed so as to yield a series of apparent molecular parameters, most generally interpreted as weighting coefficients for calculating dose partition in radiation chemistry studies of mixtures. The existence of a Jesse effect in an occasional molecular gas mixture is noted.