bluuebunny/crossref_metadata_2025 huggingface dataset:
Millimeter Wave Spectrum and Molecular Structure of Oxygen Difluoride
Authors: Hilton A. Ray , Jache Albert W. , Beal James B. , Henderson William D. , Robinson R. J.
Published: January 2005

The molecular structure of oxygen difluoride (OF2) has been studied by microwave spectroscopy techniques. A video microwave spectrometer was used to find 13 rotational absorption lines. Klystron-driven crystal harmonic generators were used as energy sources for the spectrometer. The frequencies of the lines were measured with a precise frequency standard. Nine of the lines were assigned to rotational transitions of OF2 using a graphical method. The three average rotational constants A, B, and C were determined from the exact energy solutions for the rotational transitions. The values for the rotational constants together with the effective moments of inertia calculated from them were A=61 567.71 Mc, IA=8.21096 amu, A2; B=11 066.54 Mc, IB=45.6809; C=9 343.85 Mc; IC=54.1088 amu, A2. The effective values for the oxygen fluorine interatomic distance and the apex angle 2θ calculated from IA and IB were r=1.3896 A, 2θ=104.163. The rotational inertial defect was found to be +0.217 amu, A2.
Microwave Spectrum, Structure, Dipole Moment, and Internal Barrier of Vinyl Silane
Authors: O'Reilly James M. , Pierce Louis
Published: January 2005

The structure of vinyl silane has been determined by studying the microwave spectra of each of its singly substituted isotopic species. Using Kraitchman's equations the following structural parameters were calculated: C=C1.347 ASi–C=C122∘53′   Si–H1.475H–Si–H108∘42′   C–H(cis)1.097C=C–H(cis)120∘18′C–H(trans)1.097 (assumed)C=C–H(trans)120∘38′C–H1.094C=C–H117∘59′Si–C1.853By studying the isotopic species containing an asymmetric silyl group the equilibrium conformation was found to be staggered, i.e., the silyl hydrogens are staggered with respect to the hydrogen on the central carbon. The symmetry axis of the silyl group was found to be tilted by an angle of 1°49′ from the Si–C bond axis towards the double bond. Comparison of the Si–C bond distance of vinyl silane with that of methyl silane indicates that recent estimates of the effect of changes in hybridization on the covalent radius of carbon are much too large. The barrier to internal rotation for vinyl silane has been calculated from splittings of groundstate rotational transitions of SiH3CHCH2 and splittings of first-excited state transitions of SiH3CHCH2 and SiD3CHCH2, and also from Stark effect measurements on the K = 1, J = 2←1 transitions of SiH3CHCH2. The various calculations are all in good agreement, and the best value for the barrier is found to be 1500±30 cal/mole. Quadratic Stark effect measurements on the J = 2←1 transitions gave μa = 0.648D, μb = 0.133D, and μ = 0.66D. The resultant dipole moment makes an angle of 11±2° with the a axis of SiH3CHCH2.
Analysis of the Absorption Spectrum and Zeeman Effect of Thulium Ethylsulphate
Authors: Wong Eugene Y. , Richman Isaac
Published: January 2005

The crystalline field interaction was calculated using first-order perturbation theory on intermediate coupling wave functions of Tm3+ in a D3h field. Good agreement with experimental data of Tm3+ diluted with La(C2H5SO4)3·9H2O was obtained. The following crystalline field parameters were chosen for best fit: A20〈r2〉=129.8 cm−1,A40〈r4〉=−71.0 cm−1,A60〈r6〉=−28.6 cm−1,A66〈r6〉=432.8 cm−1.
Three-Dimensional FE-MO Model. I. ΔH of Dissociation of Homonuclear Diatomic Molecules
Authors: Matlow Sheldon L.
Published: January 2005

By means of a three-dimensional FE—MO model, the ΔH's of dissociation for homonuclear diatomic molecules can be estimated. The atoms are represented by cubes, and the molecules by rectangular parallepipeds. The parameters involved are the sizes of the boxes and the effective mass of the electrons. The spectroscopic terms for the ground states of both the atoms and the molecules are obtained from the model.
The SPO (Split p-Orbital) Method and Its Application to Ethylene
Authors: Dewar Michael J. S. , Hojvat N. L.
Published: January 2005

Difficulties arise in the MO treatment of π-electron systems due to electron correlation. Current methods allow, explicitly to some extent, for horizontal correlation (i.e., correlation of electron motions parallel to the carbon skeleton) but not for vertical correlation, (i.e., correlation of electron interchange between the two π lobes). A method for doing this, first suggested by M. J. S. Dewar and C. E. Wulfman [J. Chem. Phys. 29, 158, (1958)], is outlined and applied to ethylene with satisfactory results.
Comparison of Theoretical Calculations on Diatomic Molecules with Experiment
Authors: Davidson Ernest R.
Published: January 2005

A method for the numerical computation of the vibrational-rotational term levels from an arbitrary potential curve is presented. In this method, the potential curve is approximated by a step function and the exact eigenvalues of this latter function are found by an iteration technique. The accuracy of this method is demonstrated by finding the term levels for a Morse potential and for the ground state of H2.
An Extended Hole Theory of Liquids
Authors: Blomgren George E.
Published: January 2005

The hole theory of liquids has been extended to include the effect of all configurations of particles and holes on the partition function. The potential energy of a particle in a cell surrounded by a given number of particles and holes is approximated by a Lennard-Jones and Devonshire-type function appropriate to the given number of neighbors. The partition function is derived on the basis of the model and an expansion procedure is used to simplify the problem of the summation over all configurations of particles and holes. The equation of state is obtained from the partition function and expressed in terms of a reduced volume and temperature, a cell size parameter and known physical constants. Possible extensions of the present theory are discussed.
Energy Transfer and Quenching Processes in the System Cyclohexane-Benzene-Terphenyl-Oxygen
Authors: Weinreb A.
Published: January 2005

A quantitative explanation of the results of Berry and Burton is offered. Some additional results on the effect of oxygen on the fluorescence of terphenyl are included.
High-Temperature Absorption of Carbon Dioxide at 4.40 μ
Authors: Steinberg Martin , Davies William O.
Published: January 2005

The absorption of carbon dioxide-nitrogen mixtures at 4.40 μ was examined over a temperature range of 1200 to 2100°K for optical densities of 0.10 to 0.40 atm-cm. The test gas was elevated to desired temperatures by shock compression. Properties of the test gas were determined by measurement of initial concentrations and shock wave velocities. Absorption was observed as a diminution of source beam intensity monitored with a rapid response infrared detector and displayed on an oscilloscope. Beer's law was found to be applicable over the range of temperature and concentration studied. Absorption coefficients calculated from Beer's law plots reached a maximum of 3.0 atm—1 cm—1 at about 1400°K, and were independent of total pressure from 0.26 to 1.05 atm. The absorption was also measured over a wavelength interval of 4.37 to 4.6 μ. The results of this investigation are compared to the existing theoretical and experimentally determined absorption data.
Ionization Potentials of Multiply Charged Krypton, Xenon, and Mercury
Authors: Dorman F. H. , Morrison J. D.
Published: January 2005

The determination of threshold potentials for multiple ionization processes is shown to depend on the threshold law assumed for these processes. Further support has been obtained for the previously proposed nth power rule for n-fold ionization by electron impact, and limits have been set to the values of the thresholds for multiple ionization in the rare gases and mercury.
Transient Measurements of Photochemical Processes in Dyes. I. The Photosensitized Oxidation of Phenol by Eosin and Related Dyes
Authors: Grossweiner L. I. , Zwicker E. F.
Published: January 2005

Irradiation of the fluorescein dyes in their visible absorption bands excites metastable triplet states which decay by the bimolecular reaction of triplet molecules. A rapid reaction of phenol with triplet eosin is shown by the retardation of the rate of aerobic photobleaching and an acceleration of the rate of triplet disappearance. The primary photochemical reaction between phenol or phenolate ion with the triplet dye produces a phenoxy free radical and a reduced dye free radical, which disappear in second-order processes. Numerical values are given for the rate constants of several elementary reactions. The competition between physical quenching and charge-transfer chemical reaction can be explained by spin-conserving processes.
Extreme Pressures. II. Volume-Temperature Relationship for Gases
Authors: Levitt Leonard S.
Published: January 2005

It is found, using Bridgman's data for H2O, N2, and Ar, that the V-T isobars, though curved at medium pressures, become good straight lines at the same higher pressures for which the isothermal relation p = CeB/V begins to hold (above 1000 kg/cm2 for gases, and above 4000 for liquids). Aside from the surprising linear variation of V with T under these extreme conditions, the most remarkable feature of the V-T plots is the apparent convergence of all the isobars (for a given gas) to a common intercept on the V coordinate (at 0°K). The isobars for gases therefore can be represented by the equation, V=V0+apT, where V0 is the incompressible molar volume of the substance at 0°K. Eliminating ap for two different temperatures at constant pressure gives an exact V-T relation for high pressures comparable to Charles' law, V2=V1(T2/T1)+V0(1−T2/T1).The slope ap of the isobars decreases with increasing pressure, and it is found that ap≃R′/p, where R′ is a new gas constant for high pressures, which at first increases somewhat with pressure, and reaches the same limiting value of 32R at 6000 atm for both N2 and Ar.
Quantum Mechanics of Mobile Electrons in Conjugated Bond Systems. III. Topological Matrix as Generatrix of Bond Orders
Authors: Ruedenberg Klaus
Published: January 2005

It is shown that in homonuclear conjugated systems the various bond orders and similar quantities can be written as matrix functions of the topological incidence matrix. This entails the existence of a number of useful general relations between these various quantities. The relations include as special cases: Coulson and Rushbrooke's theorem on charge orders in alternants; G. G. Hall's theorem on bond orders in alternants; McWeeny's theorem on the formal charges; Ham and Ruedenberg's correlation between Coulson and Mulliken bond orders for neighbors in alternants; closely related is Ham-Ruedenberg-Platt's relation between valence-bond bond orders and molecular orbital theory. A number of new relations between bond orders are derived and discussed. The generalization from alternants to nonalternants is given particular attention.
Quantum Mechanics of Mobile Electrons in Conjugated Bond Systems. VI. Theoretical Evaluation of Energy Contributions
Authors: Ruedenberg Klaus
Published: January 2005

The general formulas of the first paper in the series [K. Ruedenberg, J. Chem. Phys. 34, 1861 (1961)] are used to analyze the energy contributions of the molecular framework for a π-electron system in detail, without use of additional assumptions. The valence-state potential of carbon, used in the framework potential, and the 2pπ atomic orbitals are determined by a minimum principle. The Coulomb integral and resonance integral are evaluated from their constituent integrals in the tight-binding approximation. The agreement with the empirical values [see K. Ruedenberg, J. Chem. Phys. 34, 1878 (1961)] is unsatisfactory for the Coulomb integral but very good for the resonance integral. The approximate proportionality between energy matrix elements and overlap integrals is proven for a variation of the internuclear distance between 1.26 and 1.54 A.
Effect of Configuration Interactions on the Dissociation Energy and Hyperfine Structure Constants of the NO Molecule
Authors: Yamazaki M. , Sakamoto M. , Hijikata K. , Lin Chun C.
Published: January 2005

By means of a 23-dimensional configuration interaction calculation the energy and eigenfunction of the ground 2II state are determined resulting in dissociation energy of 2.2 ev. The magnetic hyperfine and nuclear quadrupole coupling constants are calculated from this molecular function. The contact term | ψ(0) |2 is obtained as 0.71×10—24 cm—3 which agrees well with experiment. The values of 〈(3cos2χ−1)σ/r3〉Av,    〈sin2χ/r3〉Av,  and  〈r−3〉Avare not much affected by the configuration interactions.
Experimental Study of the Shape of the F Band Absorption in NaCl
Authors: Markham Jordan J. , Konitzer John D.
Published: January 2005

The possibility of extending the authors' study of the optical absorption band associated with F centers in KCl to KI, KBr, and NaCl is explored. Due to the relative sizes and positions of the K and F bands in KI and KBr, one cannot resolve the two. The situation in NaCl is unclear; hence, a detailed study has been made. A unique F center can be formed in this crystal by various techniques. The optical bleaching properties depend on the means of production. Smakula's equation applies to this center, and it seems to be Pekarian. Our ``best equation'' for the width at half-height H (in ev), has the form H2=0.075 coth (105.5/θ) — 0.01; where θ is the temperature. This study supports the general theory [J. J. Markham, Revs. Modern Phys. 31, 956 (1959)] although all the experimental problems have not been resolved.
Theory of the Surface Tension of Molten Salts
Authors: Reiss H. , Mayer S. W.
Published: January 2005

A theory of the surface tension of molten salts is presented, based on a result obtained by Reiss, Frisch, Helfand, and Lebowitz and a theory of corresponding states. This theory allows one to compute the surface tension of a salt if the diameters of the ionic hard cores are known along with the densities of the salts at a given temperature. Agreement with experiment is very good.
Gaseous Detonations. XV. Expansion Waves in Gaseous Detonations
Authors: Miyama Hajime , Kydd Paul
Published: January 2005

The ultraviolet absorption spectrum of OH and the visible light emission profile in the rarefaction wave following a detonation in C2H2+H2+2O2 have been measured. Analysis of the absorption spectrum at an initial pressure of 60 mm Hg gives an average rotational temperature of 3164°K during the first 310 μsec. after the detonation wave front. The gas temperature calculated by using detonation theory and necessary thermodynamic data is 392°K higher than the experimental rotational temperature. The difference is very close to the difference of 350°K which has been predicted by T. C. James theoretically.

The emission profiles demonstrated the presence of double waves at initial pressures higher than 90 mm and the appearance of these waves coincides with an increase in detonation velocity to that calculated using a ``frozen'' sound velocity.

In expansion waves produced by bursting a thin diaphragm with the detonation wave, the emission intensity was found to be far higher than predicted and the velocity of the expanding gas and the shock wave ahead of it to be somewhat lower than expected.
Effects of Diffusion in Nuclear Magnetic Resonance Spin-Echo Experiments
Authors: Woessner D. E.
Published: January 2005

The spin-echo attenuation by molecular self-diffusion in an inhomogeneous magnetic field has been calculated for three- and four-pulse sequences. The method employed avoids the question of an averaging procedure as discussed by Das and Saha. Experimental measurements yield confirmation of the three-pulse results.
Magnetic Properties of Uranium Tetrafluoride
Authors: Leask M. J. M. , Osborne Darrell W. , Wolf W. P.
Published: January 2005

The magnetic susceptibility of a number of UF4 samples has been measured in the temperature range 1.3°—20.4°K, using the mutual inductance method of McKim and Wolf. Although some of the samples were highly purified, initial measurements indicated appreciable differences between their susceptibilities below 4.2°K. These differences were eventually overcome by subjecting the specimens to the same heat treatment just before susceptibility measurement. The effect of the heat treatment is not entirely understood, but a number of possibilities have been investigated. Theoretically, the main features of the susceptibility variation have been explained on a simple crystal field model of noninteracting ions, and this also accounts for the recent specific heat measurements of Burns, Osborne, and Westrum. An even better theoretical fit has been obtained by introducing a small, adjustable interaction between neighboring uranium ions. Below 2°K the measured susceptibility was anomalous: Samples which at higher temperatures were very similar (±1%), showed considerable differences (∼25%), the susceptibility in some cases increasing rapidly with decreasing temperature, and becoming dependent on measuring field. This behavior is unexplained but it is probably not a property of ``pure'' UF4.
NMR Spectra of Some Halogenated Propenes
Authors: Swalen J. D. , Reilly C. A.
Published: January 2005

The 40-Mc/sec nuclear magnetic resonance (NMR) spectra of CF3CF=CF2, cis and trans isomers of CF3CCl=CFCl, and CF3CCl=CF2 have been analyzed in terms of the NMR parameters of the molecules; i.e., the magnetic shielding constants of the various fluorine nuclei and the spin-spin coupling constants between them.

The spectrum of perfluoropropylene, CF3CF=CF2, has been analyzed adequately by a first-order perturbation treatment. The spectrum of each of the isomers of CF3CCl=CFCl has been analyzed exactly as an AB3 system of spins by the use of the trace relations only. In a previous analysis of the cis-isomer, a small signal from the trans-isomer was not identified. This small signal has now been proved to arise from the trans-isomer. The spectrum of CF3CCl=CF2 has been analyzed by an interative scheme on an electronic computer. Here the nuclei were treated as an ABC3 system of spins.

The various magnetic parameters determined by these analyses have been compared with the molecular structures and have been briefly discussed in terms of the theories of the magnetic properties of molecules.
Distortable Double Well. A Prototype for the Analysis of Relaxation Spectra
Authors: Fuchs R. , von Hippel A.
Published: January 2005

The origin of dielectric relaxation spectra is frequently not the rotation of dipoles as visualized in the Debye and Onsager models but the reversible transfer of ions or electrons between equilibrium sites. The displacement of such charge carriers corresponds to a reversal of dipole moments and had been treated previously as a shifting of charges between fixed equal or unequal double wells. The reversal of dipole moments in condensed phases, however, frequently has decisive after effects: The electrical unbalance created leads to a compensating action of the surroundings, lowering the free energy and tending to freeze in the charge in the occupied well site. Thus the double well becomes unequal because of the reaction of the embedding medium. This model of a distortable double well is here treated, first in its stationary state with and without superposed dc field and then in its ac response, under the simplifying assumption that the surroundings react by an exponentially decaying distortion described by a time constant and final well depth. The characteristics of the model are that it incorporates the equal and unequal fixed double well as special cases but in addition shows an inherent distribution of relaxation times and—for long observation periods—an anomalously large polarizability, since eventually the wells can be turned with their deepened sites in the favorable field direction.
ESR Studies on the Bonding in Copper Complexes
Authors: Kivelson Daniel , Neiman Robert
Published: January 2005

ESR spectra of copper complexes have been interpreted by means of molecular orbital theory, and the ``covalent'' character of both σ and π bonds have been discussed for a variety of compounds. Overlap integrals have been considered in a consistent manner in treating σ bonds. Particular attention has been given to Cu phthalocyanine and several of its derivatives. The in-plane π bonding may be as important in determining the properties of a Cu complex as is the in-plane σ bonding.
Studies of Fused Salts. III. Heats of Mixing in Silver Nitrate-Alkali Nitrate Mixtures
Authors: Kleppa O. J. , Clarke R. B. , Hersh L. S.
Published: January 2005

The enthalpies of mixing in binary liquid mixtures of silver nitrate with lithium-, sodium-, potassium-, and rubidium nitrate have been measured. It is found that the molar enthalpy of mixing (ΔHM) changes in a regular fashion from positive values for lithium- and sodium- to negative values for potassium- and rubidium nitrate. Neglecting second-order effects, the mixing enthalpies may be represented by the following semiempirical relation, ΔHM≅−X(1−X)[140 δ2−24(δ−0.01)] kcal/mole.The parameter δ is (d1—d2) / (d1+d2), where d1 and d2 are the interionic distances characteristic of the two pure components, while X and (1 — X) are their mole fractions. In this expression the δ2 term has been taken from the equivalent expression for the binary alkali nitrates, which presumably are essentially ionic. The value of the numerical factor (140 kcal/mole) is of the order of the lattice energy of these salts. The term which is linear in δ takes into account departures from ionicity in silver nitrate, and is of magnitude comparable to the nonionic contribution to the lattice energy of this compound. It is shown by considering available emf data for the silver halide-alkali halide systems that expressions of this type may be quite useful in predicting the heats of mixing in as yet unexplored systems.
Microwave Spectrum of Methyl Nitrate
Authors: Dixon William B. , Wilson E. Bright
Published: January 2005

The ground-state rotational constants of methyl nitrate show that the five heavy nuclei of the molecule lie in the same plane. The hydrogen atoms of the methyl group are found to be staggered with respect to the nearest oxygen of the NO2 group. Stark effect measurements yield a dipole moment of 3.10±0.05 D.

Satellites arising from excited states of the torsion of the NO2 group were observed. Rough relative intensity measurements yield a frequency of 130±20 cm—1 for this normal mode and a barrier of 9100±2600 cal/mole. This would seem to indicate a significant amount of double-bond character in the CO–N bond.

The barrier to internal rotation of the methyl group, as determined from torsional satellite splittings, is 2321 cal/mole.

A large discrepancy exists between the experimental and statistical entropies, the reason for which is not clear.

Satellites arising from the combination first excited states of the methyl and NO2 torsions have an anomalous appearance on the basis of the single internal rotor theory. A qualitative explanation for this is obtained when the theory is extended to include the torsion of the NO2 group.
Effect of Chemisorbed Hydrogen on the Magnetization of Nickel
Authors: Dietz R. E. , Selwood P. W.
Published: January 2005

The effect of chemisorbed hydrogen on the saturation magnetization of nickel was investigated on fine particles of nickel. For certain preparations the saturation moment of the nickel was within 1 or 2% of that of massive nickel; this is considered evidence that the surfaces of the nickel in these samples were substantially free from chemisorbed impurities, and that the electronic state of the nickel was identical to that of massive nickel. For these preparations, hydrogen decreases the saturation moment of the nickel by about 0.7 Bohr magneton per average atom of hydrogen adsorbed. This effect appears independent of temperature up to 300°K (the highest temperature investigated) and of surface coverage over nearly the entire range.
Variation of the Intensity of the Methyl Symmetrical Bending Vibration in Paraffins
Authors: Basila Michael R. , Crable George F.
Published: January 2005

The integrated infrared absorption coefficients of the methyl C–H symmetrical bending vibration of a number of normal and branched paraffins have been studied. Several approaches to the correlation of intensity variations with structure are discussed and evaluated in terms of the experimental data. The conclusions are (a) the intensities of the branched and normal paraffins must be treated as two distinct classes, and (b) the branched paraffin group intensities must be further broken down into three types: (1) methyl groups adjacent to a tertiary or quaternary carbon atom having no other methyl groups directly adjacent, (2) methyl groups adjacent to tertiary or quaternary carbon atoms having other adjacent methyl groups directly attached, and (3) methyl groups at the ends of branches or chains of two or more carbon atoms in length. Integrated absorption coefficients are given for each type of group and approximate C–H bond moments are calculated from these values.
Quantum Statistical Mechanics of Isotope Effects
Authors: Oppenheim I. , Friedman A. S.
Published: January 2005

Expansions in powers of Planck's constant are utilized in a discussion of isotope effects on the thermodynamic properties of fluid systems. Theoretical calculations of the differences in the equations of state of the hydrogen isotopes and of the helium isotopes are presented and comparison with experimental results are made. Agreement between theory and experiment is excellent.
Trapped Radicals in Irradiated n-Propanol at 77°K
Authors: Alger R. S. , Anderson T. H. , Webb L. A.
Published: January 2005

The free radicals formed in solid n-propanol by radiolysis were examined by electron paramagnetic resonance (EPR) techniques and compared to radicals in photolyzed propanol-hydrogen peroxide mixtures. Identification of the radicals is based on modifications in the EPR hfs introduced by substituting deuterium for hydrogen at selected positions in the molecules. Radiolysis leads to radical formation by removing a hydrogen atom from the α carbon while photolysis apparently favors hydrogen abstraction from the β carbons. Mass spectrographic analysis of the gas liberated during irradiation gave corroborative evidence regarding the hydrogen atoms; however, the analysis also showed that some hydrogen escaped from other than the α and β carbon positions. The experimental EPR hf spectra are compared to a series of constructed spectra obtained by summing Gaussian absorption curves according to the interactions indicated by the proposed models of the radicals.
Crystal Structure of Vanadyl Bisacetylacetonate. Geometry of Vanadium in Fivefold Coordination
Authors: Dodge Richard P. , Templeton David H. , Zalkin Allan
Published: January 2005

The structure of vanadyl bisacetylacetonate has been determined from three-dimensional x-ray diffraction data. The crystals are triclinic, space group P1̄, with a=7.53±0.02 A, b=8.23±0.03 A, c=11.24±0.04 A, α=73.0°, β=71.3°, γ=66.6°, Z=2. The structure consists of discrete molecules of VO(C5H7O2)2. Each vanadium atom has five oxygen neighbors at the corners of a rectangular (nearly square) pyramid, with vanadium near its center of gravity. The vanadium-oxygen distances are 1.56 A to the apex atom (vanadyl oxygen) and 1.96, 1.96, 1.97, and 1.98 A to the others. Other bond distances average 1.28 A for C–O, 1.40 A for C–C (ring), and 1.52 A for C–C (methyl). Standard deviations are 0.01 A for V–O bonds and 0.02 A for C–O and C–C bonds. Each acetylacetone skeleton is planar, and this plane makes an angle of 163° with the plane of the other acetylacetone skeleton of the same molecule.
Some Effects of Temperature and Viscosity on Fluorescence and Energy Transfer in Solutions
Authors: Weinreb A.
Published: January 2005

The transfer of excitation energy between molecules of different compounds in solutions is investigated as a function of temperature and viscosity of the solution. In all cases an increase in transfer efficiency with increasing diffusion is observed. The fluorescence of the donor molecules in the absence of acceptor molecules is studied as a function of temperature and the possible influence of the respective changes on the observed transfer efficiencies is discussed.
Nonresonant Dielectric Dispersion in Asymmetric Rotors
Authors: Boggs James E. , Deam A. P.
Published: January 2005

Dielectric dispersion measurements at 400 Mc and 40.0°C are reported for CH2=CHCl and CH2=CF2 in the gas phase. The results for these two molecules and earlier measurements on C2H5Cl are compared with theoretical expectations for nonresonant dispersion resulting from pressure-broadened transitions between asymmetry doublet levels.
Flame Propagation in Free-Radical-Containing Solids at Low Temperatures
Authors: Berlad A. L.
Published: January 2005

A nonadiabatic theory of flames is formulated which describes the features of flame propagation in free radical containing cryogenic solids. This ``cryogenic flame'' theory is an extension of nonadiabatic flame theory associated with gaseous flames. The general features of cryogenic flames prescribed by the theory include: the characteristic propagation velocity of the reaction wave, the spatial structure of the composition and temperature fields, and the extinction limits associated with flame existence-nonexistence. Application of the formulation is illustrated for the case of flame propagation in N-atom-containing solid N2.
First Excited Σg+1 State of the Hydrogen Molecule
Authors: Davidson Ernest R.
Published: January 2005

A variation calculation on the first excited Σg+1 state of H2 has been carried out using an expansion in elliptical coordinates. All results are reported in Hartree atomic units.

The potential function resulting from this calculation is characterized by having minima at R=1.9 and R=4.3 and a maximum at R=3.3.

The energy obtained at R=1.9 using a 20-term, open-shell, covalent-type wave function was —0.7162 as compared with the ``experimental'' value of —0.7181. Due to convergence difficulties, many more configurations are required to improve this result significantly. At R=4.3, on the other hand, the best result was obtained with an open-shell wave function including nine ionic terms and nine atomic terms. This result of —0.7007 is below the reported ``experimental'' value of —0.6935 because the two lowest (2pσ)2Σg+1 vibrational levels have not been found experimentally. The energy at the top of the barrier was computed to be —0.6844 and probably is as low as —0.6884.

The vibrational levels for this potential function have been computed by a numerical integration technique. The fact that these are in one-to-one correspondence with a combination of the experimental 1s2s and (2pσ)2 levels indicates that both of these sets of levels belong to the first excited state.
NMR Fluorine-Fluorine Coupling Constants in Saturated Organic Compounds
Authors: Petrakis L. , Sederholm C. H.
Published: January 2005

The spectra of several fluorine-substituted, saturated, organic compounds have been investigated. It has been found that the coupling constants between 1,2 fluorine atoms are usually near zero. The coupling constants between 1,3 fluorine atoms in a free chain are usually between 7 and 10 cps if all of the intermediate skeletal atoms are carbon atoms. If one of the intermediate skeletal atoms is a nitrogen atom, these coupling constants go up to between 10 and 17 cps. The coupling constants between 1,4 fluorine atoms are usually in the range 2–7 cps when a nitrogen atom is in the intermediate skeletal chain. Rings usually reduce all coupling constants below the above stated values.

Several exceptions are found to these generalizations. These generalizations with their exceptions lead the authors to believe that in the case of coupling between fluorine atoms, the main effect is not through-the-bonds, but rather a direct-through-space interaction. It is demonstrated that the restricted rotation about the carbon-carbon bonds has little to do with the near-zero coupling constants, but that these are readily explained on the basis of through-space coupling.
On the Parameters Used in Semiempirical Molecular Orbital Theory for Conjugated Hydrocarbons
Authors: Lykos Peter G.
Published: January 2005

Within the π-electron approximation, formulas are displayed for some of the properties of the benzene molecule. The integrals which enter the formulas are treated as empirical parameters. The one-electron integrals are interpreted as being over-orthogonalized atomic orbitals consistent with the use of zero differential overlap for the two-electron integrals. An attempt is made to find one set of parameters which will simultaneously account for several properties of the benzene molecule. The resolution of benzene integrals into empirically evaluated components in a quantum mechanically well-defined way firstly provides a more critical test of the level of the π-electron approximation and secondly renders more sure the use of these parameter values for other molecules.
Reversible Phase Transition of Phosphorus Pentoxide
Authors: Johns I. B. , Ulmer H. E. , Edwards J. W.
Published: January 2005

Measurements of volume change on compression of phosphorus pentoxide showed a reversible phase transition. Pressure-volume curves, obtained by a difference method, showed a marked hysteresis, the forward transition requiring from 1600 to 2700 kg/cm2 greater pressure than the reverse, depending on the temperature. X-ray diffraction studies at high pressure confirmed the findings. The crystal form of the new modification has not yet been determined.
Zeeman Effect of the Nuclear Quadrupole Resonance Spectrum in Crystalline Powder
Authors: Morino Yonezo , Toyama Masaharu
Published: January 2005

The Zeeman effect of the nuclear quadrupole resonance spectrum for spin I=32 in crystalline powder has been studied. Theoretical considerations have predicted that, in a nonaxial electric field gradient, the absorption line should be broadened with a characteristic envelope by a weak static magnetic field. When a radio-frequency (rf) field is applied parallel to the static field, one pair of sharp minima should be produced on the envelope at the frequencies shifted by ±γH/2π from the unperturbed quadrupole resonance line, and two pairs of sharp maxima at ±(1−η)γH/2π and at ±(1+η)γH/2π. Resonance spectra of Cl35 nuclei in p-dichlorobenzene and cyanuryl chloride have clearly displayed the predicted shape of envelopes on a recorder at room temperature. Analysis of them has resulted in determining the asymmetry parameters of electric field gradients with considerable accuracy; 0.070±0.01 for the α-modification of p-dichlorobenzene, and 0.22±0.03 for ν1 line, and 0.23±0.04 for ν2 line of cyanuryl chloride.
Molecular Structure of B9H13(CH3CN)
Authors: Wang Frederick E. , Simpson Paul G. , Lipscomb William N.
Published: January 2005

A three-dimensional x-ray diffraction study of a single crystal of B9H13(CH3CN) has yielded the complete structure, including hydrogen atom positions. The nine boron atoms form an icosahedral fragment, like the arrangement in B10H14 with one boron atom missing. The structure is consistent with the present form of the topological theory of boron hydrides and ions in that it has two BH2 groups, and is related to an anticipated B9H14— ion in the same way that B10H12(CH3CN)2 is related to B10H14—2 ion. The crystals are monoclinic, in the space group P21/m, and have two molecules in a unit cell having parameters a=5.64, b=9.22, c=9.81 A and β=90°±30 min.
Growth Rates of Zinc Crystals from the Vapor Phase
Authors: Parker Robert L. , Kushner Lawrence M.
Published: January 2005

The rate of growth of zinc crystals from the vapor phase has been studied as a function of the vapor supersaturation σ at a temperature of 390°C. The σ values ranged between 0.009 and 0.09. The rate R was found to vary approximately linearly with σ, permitting estimates to be made of the two parameters σ1 and βC0, appearing in the Burton, Cabrera, and Frank theory of crystal growth. The results indicate that surface nucleation was not operative in either the nucleation or the growth of these crystals.
Mean Lifetime of the Lowest Excited Singlet State of Benzene
Authors: Donovan J. W. , Duncan A. B. F.
Published: January 2005

The lifetime of the first excited 1B2u state of benzene has been determined from measurement of decay of fluorescence in the vapor phase. High-frequency electrical excitation, rather then optical excitation was used. The pressure dependence of the lifetime has been studied under different conditions. The lifetime extrapolated to zero pressure is 0.59 μsec. The pressure dependence is interpreted by a mechanism of collisional deactivation.
Direct Field Effects in Electron Paramagnetic Resonance Hyperfine Spectra
Authors: Weil John A. , Anderson John H.
Published: January 2005

The electron paramagnetic resonance spectrum exhibiting hyperfine effects from one nucleus is discussed for the case when the nuclear spin interacts appreciably not only with the electron magnetic moment but also directly with the applied magnetic field. The predicted hyperfine structure consists, in general, of 2S (2I+1)2 lines. The angular dependence of the intensities and splittings is investigated; nodes in the splitting are found to be possible even when the eigenvalues of the hyperfine splitting tensor are nonzero. When the direct-field interaction is large, 2I+1 principal hyperfine lines occur, flanked by weaker ``outrider'' lines. Another mechanism for producing outrider lines in high direct fields, the nuclear quadrupole interaction with an electric field gradient, is discussed. Magnetic resonance studies of color centers in germanium-doped quartz demonstrate some of the predicted effects.
Calculations of the Lower Excited Energy Levels of the Cyclic Polyenes, Radicals, and Ions
Authors: Bouman Nicolaas
Published: January 2005

The lower excited energy levels of the cyclic polyenes, radicals, and ions with 3 to 8 carbon atoms are calculated with inclusion of all the interelectronic integrals and without empirical data, except the carbon-carbon distance.
Low-Temperature Heat Capacities and Thermodynamic Functions of Some Platinum and Palladium Group Chalcogenides. I. Monochalcogenides; PtS, PtTe, and PdTe
Authors: Grønvold Fredrik , Thurmann-Moe Torkild , Westrum Edgar F. , Chang Elfreda
Published: January 2005

Heat capacities of platinum monosulfide, platinum monotelluride, and palladium monotelluride were measured in the range 5–350°K. They show the normal sigmoidal temperature dependence with no evidence of transitions or other anomalies. The derived heat-capacity equations were integrated. Values of heat capacities, entropy and enthalpy increments, and of the free-energy function are tabulated for selected temperatures. At 298.15°K, the third-law entropies are 13.16 cal gfw—1 °K—1 for PtS, 19.41 cal gfw—1 °K—1 for PtTe, and 21.42 cal gfw—1 °K—1for PdTe. The new data on PtS have been correlated with existing decomposition-pressure data to evaluate ΔHf, ΔFf, and ΔSf298.15°K. Entropies for other platinum-metal monochalcogenides were estimated.
Ultraviolet Spectra of Carbon Monoxide
Authors: Lefebvre-Brion H. , Moser Carl , Nesbet R. K.
Published: January 2005

The vertical excitation energies for many of the known electronic transitions in carbon monoxide have been calculated from LCAO-MO SCF functions built on three different basis sets of functions: (a) 1s, 2s, 2s′, 2p, and 2p′ atomic functions on each center; (b) 1s, 2s, 2p, 3s, and 3p atomic functions on each center; (c) 1s, 2s, 2s′, 2p, 2p′, 3s, and 3p functions on each center. The excitation energies calculated from the functions built on set (a) are hardly different from those obtained from an earlier calculation where the SCF orbitals were constructed from the simplest possible basis set (1s, 2s and 2p functions on each center). Set (b) gives results which are in quite good agreement with experiment for all the transitions studied. Our calculations support the analysis made many years ago by Mulliken that the presently known electronic transitions in carbon monoxide can be divided into (1) transitions between molecular orbitals both of which are mainly made up of atomic L functions; (2) transitions between molecular orbitals the lower of which is mainly made up of atomic L functions and the upper is mainly atomic M functions. Set (c) gives the best energy for the ground state and moderately good agreement with experiment for both kinds of transitions.
Reactions of Methyl with Isopropyl Radicals
Authors: Heller Carl A.
Published: January 2005

The photolysis of methyl isopropyl ketone has been used to study the reaction of methyl and isopropyl radicals at 100° in the gas phase. The disproportionation/combination ratio is 0.17±0.03. The ratio, isobutane2/ethane×hexane is 3.5±0.33. Deuterated ketone was used to permit correction for abstraction reactions.
Effect of Temperature on the Intensity and Structure of Bands in the Infrared Spectrum of Rhombic Sulfur
Authors: Neff Vernon D. , Walnut Thomas H.
Published: January 2005

The infrared spectrum of rhombic sulfur was obtained in the region between 750 and 2000 cm—1. The relative intensities of the bands at 845, 936, 1298, and 1513 cm—1 were measured as a function of temperature and sample orientation from —190° to 85°C.

An expression is given that relates the temperature dependence for an overtone or combination band to the values of the component frequencies. The expression is used in conjunction with the measured temperature dependence to reject some previous assignments and to establish rough values of the component frequencies in the observed overtone and combination bands. A tentative assignment consistent with the rough values found for the component frequencies is made.

In addition, the structure of a band is considered to be the result of combination with acoustic lattice modes, and the temperature dependence of the structure is analyzed from this point of view. The temperature dependence of the intensity of the structure of the band at 845 cm—1 far from the peak agrees roughly with the expression obtained, but the dependence close to the peak does not.
Proton Magnetic Resonance Study of Ferroelectric Potassium Ferrocyanide Trihydrate
Authors: Blinc R. , Brenman M. , Waugh J. S.
Published: January 2005

Proton magnetic resonance and vibrational spectra of potassium ferrocyanide trihydrate have been studied between 77° and 300°K. From the observed two sets of O–H stretching frequencies it has been possible to suggest the probable positions of four previously undetermined water molecules in the unit cell. Changes in the vibrational spectra and in the proton resonance second moment in the neighborhood of the Curie point indicate that the onset of ferroelectric behavior is associated with a dynamical orientational ordering of the hydrogen-bonded water molecules. Apparently there is also a contribution to the spontaneous polarization and internal field from displacements and polarizability of the K+ and Fe(CN)6—4 ions.
Recombination of Atomic Oxygen on Surfaces
Authors: Hacker D. S. , Marshall S. A. , Steinberg M.
Published: January 2005

Catalytic surface recombination of atomic oxygen is studied in a flow system by paramagnetic resonance absorption and a comparison is made with platinum wire detectors for the same conditions of flow. Recombination of oxygen atoms on a fuzed quartz surface is found to follow first-order kinetics with a surface recombination efficiency of 4.0×10—5 per collision. Recombination on platinum wire detectors held at 200° and at 850°C is also found to be first order in oxygen atoms with surface recombination efficiencies of (0.01±0.002) and (0.1±0.02) per collision, respectively. Efficiencies for platinum are determined from the surface recombination heating and the strength of the oxygen-atom magnetic resonance. The atom-decay rate down the flow tube is found to be first order in oxygen atom with a dependence on the total pressure that suggests the homogeneous formation and subsequent reaction of ozone. The observed rates are consistent with the following scheme: O+O·S→ lim k1O2+S(S=surface).O+O2+M→ lim k2O3+M(M=third body).O+O3→ lim k32 O2.The three-body rate constant k2 is found to have a value of 2.5×1014 cc2 mole—2 sec—1.
Salt Effect in Metal-Ammonia Solutions: Sodium Chloride in Sodium-Ammonia Solution at —33°C
Authors: Berns Donald S. , Lepoutre Gerard , Bockelman Elizabeth A. , Patterson Andrew
Published: January 2005

Using the model of Becker, Lindquist, and Alder for the equilibria in a solution of sodium in liquid ammonia, the authors have assumed an additional equilibrium between sodium and chloride ions and dissociated sodium chloride to compute the concentrations of ionic species, atoms and dimers when the common-ion electrolyte sodium chloride is added. Estimates of the ionic activity coefficients are included in the calculation. The calculated concentrations of conducting species are employed in the Onsager-Kim theory for the conductance at low fields of a mixture of ions. Values of [Na]total ranging from 5×10—4 to 6×10—2 and of the ratio of sodium chloride to [Na]total ranging from zero to 28.5 are included in the calculations. All data are for —33°. The computed conductances are compared with some newly-reported experimental measurements. The calculations are described and the results analyzed and criticized in light of values of the equilibrium constants for the sodium-ammonia system available from a variety of measurements.
Potential Energy Curves for the X 1Σg+ and B 1Σu+ States of Hydrogen
Authors: Tobias Irwin , Vanderslice Joseph T.
Published: January 2005

The recently reported accurate data of Herzberg and Howe have been used to calculate the potential energy curves for the X 1Σg+ and B 1Σu+ states of hydrogen by the Rydberg-Klein-Rees (RKR) method. The results are compared with the results of the quantum calculations of Kolos and Roothaan and Dalgarno and Lynn. The agreement is good; in fact, the interaction energy obtained by Dalgarno and Lynn for the ground state agrees with the RKR values to within 2% in the region where the two curves overlap. The rotational predissociation observed in the ν″=14 level of the X 1Σg+ state is discussed. It appears as if there may exist here an unusual case of a sharp spectral line associated with a state which is very close in energy to the maximum of a potential barrier.
Absolute Infrared Intensities of the CS2 Fundamentals in CCl4 Solution and of the 768–797 cm—1 Fermi Doublet of CCl4 in Cyclohexane Solution
Authors: Kalman Otto F. , Decius J. C.
Published: January 2005

The absolute infrared intensities of two nonpolar solute molecules were determined in nonpolar solvents by extrapolating the apparent intensities to zero concentration. For CS2 the intensities were found to be 5.8×107 cm mole—1 in CCl4 in 5.2×107 cm mole—1 in C2Cl4 for the v3 (1523 cm—1) mode, and 9.5×105 cm mole—1 in CCl4 for the v2 (395 cm—1) mode. For CCl4 the intensity of the 768–797 cm—1 Fermi doublet was found to be 5.4×107 cm mole—1 in cyclohexane. The results are discussed in relation to the Polo-Wilson, Person, and Buckingham expressions for the gas to solution intensity ratio. Modifications of the dielectric expressions were investigated.
Effects of Anharmonicity of Molecular Vibrations on the Diffraction of Electrons. II. Interpretation of Experimental Structural Parameters
Authors: Kuchitsu Kozo , Bartell L. S.
Published: January 2005

The effects of anharmonic vibrations on the molecular intensity function M (s) of electron diffraction and on the radial distribution function f(r) considered in paper I, are treated more rigorously to meet current needs. More definitive general relations for interpreting experimental diffraction data in terms of molecular structure parameters of known absolute significance are presented.