bluuebunny/crossref_metadata_2025 huggingface dataset:
Pure Rotational Spectrum of Nitric Oxide
Authors: Hall Richard T. , Dowling Jerome M.
Published: January 2005

The pure rotational spectrum of nitric oxide was measured over the frequency range 18–94 cm−1. The values of the effective rotational constants, B0, are in close agreement with microwave values. The values of the effective rotational constants, derived by least-squares analyses, are B0            D0H0Π122  1.671854±0.000081 cm−1(3.4±3.0)×10−7 cm−1(−1.42±0.29)×10−9 cm−1Π322  1.720178±0.000062 cm−1(10.24±0.23)×10−6 cm−1(+1.00±0.23)×10−9 cm−1.These constants reproduce the observed spectrum to an average deviation of approximately ±0.0012 cm−1. The unperturbed ground-state constants are also given. The spin—orbit coupling constant A0 is discussed.
Far-Infrared Spectra of Dimethylsulfide, Isobutylene, and Acetone Obtained with a Vacuum-Grating Spectrometer in the 240–10-cm−1 Spectral Region
Authors: Smith D. R. , McKenna B. K. , Möller K. D.
Published: January 2005

The far-infrared spectra of dimethylsulfide, isobutylene, and acetone in the 240–10-cm−1 spectral region are reported. Absorption bands were found at 185.5, 183.5, 180.9, 176.8, 173.0, 168.2, and 162.3 cm−1 for dimethylsulfide. For isobutylene bands were found at 214.0, 197.3, 196.3, 186.5, 181.8, 176.0, and 165.0 cm−1. The strongest bands observed for acetone were at 124.5 and 104.5 cm−1. In addition to these bands strong absorption in the 45–10-cm−1 region was found for all three compounds.
Thermodynamics of Shock Compression of Metals
Authors: Huang Y. K.
Published: January 2005

This paper presents an analytic method for evaluating the effect of shock compression on metals. A lattice potential of the Born—Mayer type is used for calculating the pressure, compressibility, Grüneisen coefficient, entropy, temperature, and energy. A general equation of state is determined in the form of p(v, T) =f(v)+T g(v). Except for the use of a few well-established thermodynamic properties of the metal, no experimental data from shock-wave measurements are required for the theoretical calculation in this paper. Comparison between the calculated and cited experimental results is made only to test the accuracy of the analysis, and agreement turns out to be fairly close. The analysis also establishes a validity range for shock compressibility of solids, and the material model considered is sensitive to its lattice structure as compared with a continuum model.
Spectroscopic Properties of the Lower-Lying Excited States of Fluorenone
Authors: Yoshihara Keitaro , Kearns David R.
Published: January 2005

The spectroscopic properties of the lower-lying electronically excited states of fluorenone have been investigated. A test for n—π* transitions, based upon the effect of oxime formation on the absorption spectra, is discussed. Application of the oxime test to fluorenone, in conjunction with an examination of the emission properties, the solvent effects on the absorption spectrum, the vibrational structure of the fluorescence spectrum, the absorption spectra of related molecules, and the results of MO calculations clearly establish that the lowest excited singlet state of fluorenone is a (π, π*) state, rather than an (n, π*) state, as previously assigned.

The principal emission observed from fluorenone in solution at room temperature and at 77°K, and from crystalline fluorenone, is demonstrated to be fluorescence. Both the fluorescence spectrum and the quantum yield for fluorescence were found to be solvent and temperature dependent. At room temperature in solution, the fluorescence quantum yield is about 1% and increases to about 12% upon cooling to 77°K. The fluorescence quantum yield from fluorenone crystals is nearly temperature independent, but decreases by a factor of 14 when the crystal is melted. The relation between the quenching of the fluorescence in fluid solutions and the concommitant shift of the emission spectra is discussed in terms of the interaction between excited state fluorenone molecules and polar solvent molecules.

Very weak delayed fluorescence is observed from concentrated rigid-glass solutions and zone-refined crystals of fluorenone. In fluorenone crystals doped with 3.7×10−2 mole/mole pyrene, the delayed fluorescence is considerably stronger than in the ``pure'' crystals, and strong pyrene phosphorescence is observed.

Normal phosphorescence from fluorenone could not be observed from thoroughly purified material, but estimates of the singlet—triplet splitting, combined with the pyrene-doping experiments and solution absorption spectra obtained using heavy-atom solvents, indicate that the lowest triplet state of fluorenone is located near 560 to 570 mμ. Anomalous phosphorescence (τ=3.6 sec, λ0–0=435 mμ, Φ≃0.01) has been observed, but only upon excitation of the fluorenone to a high-lying excited singlet state (<330 mμ). It is proposed that this anomalous phosphorescence originates from some new chemical species which is produced photochemically in its excited triplet state from fluorenone.
Selective Enhancement in Hydrogenlike Molecules with the Rare Gases. I. H2 with Ar and Kr
Authors: Takezawa S. , Innes F. R. , Tanaka Y.
Published: January 2005

The early work of Lyman on selective enhancement of the H2 spectrum in the vacuum-uv region when excited with Ar is studied further and extended to include some additional evidence with Kr as well as with Ar. The earlier interpretations are modified, and resonance fluorescence is seen to offer a generally satisfactory explanation, but here collisions of the second kind also offer a possible explanation as well. At the same time, it should be remarked that rather little evidence for such collisions involving metastables was observed in this work, as contrasted with collisions involving allowed levels. A rotation-forbidden process, thus necessarily collisional, can be advanced in a few of the observed cases.
Magnetic Moment, Magnetic Work, and Internal Energy of NiSiF6·6H2O in the Region 0.3°—4.2°K with Magnetic Fields 0–90 kG Parallel to the c Axis
Authors: Hornung E. W. , Fisher R. A. , Brodale G. E. , Giauque W. F.
Published: January 2005

Values of the magnetic moment of a 3.5-cm-diam spherical single crystal of NiSiF6·6H2O have been determined over the range 0.3°—4.25°K and 0–90 kG. The field was parallel to the c crystallographic axis. The observations have been used to give values of the isothermal differential magnetic susceptibility, and the isothermal work of magnetization. The data have been combined with our previous measurements of the heat capacity and entropy in magnetic fields to give values of the internal energy and heat content. The above properties will, with later observations. serve as a basis for extending the determination of the magnetothermodynamic properties of NiSiF6·6H2O into the region below 0.3°K. All of the data refer to a spherical crystal without correction for the demagnetizing effect since this is unnecessary and inconvenient in a thermodynamic treatment. This substance is very completely saturated at the available magnetic fields and temperatures. The saturation value, corrected for diamagnetism, was found to be 12547 G·cm3/mole, corresponding to a g=2.246. Observations of the saturation moment at fields of 60–90 kG indicate that there is no appreciable ``temperature-independent'' paramagnetic component in the magnetic moment.
Millimeter-Wavelength Microwave Spectrum of Nitrogen Dioxide
Authors: Lees Ronald M. , Curl R. F. , Baker John G.
Published: January 2005

Two low-N millimeter-wavelength transitions of 14N16O2 were observed. The 19 additional hyperfine components were combined with previously reported data and hyperfine coupling constants of much greater reliability were obtained. Some improvement in the accuracy of rotational constants was made.
Energy Storage and Luminescence in KI:Tl at Low Temperatures
Authors: Hadley Wayne B. , Polick Stanley , Kaufman R. Gilbert , Hersh Herbert N.
Published: January 2005

X irradiation of KI:Tl at 78°K results in storage of energy which can later be released as light by thermal or by optical means. Observation of stimulation spectra, absorption spectra, and emission spectra together with light sum and bleaching experiments indicate that the storage centers are I2− and Tl+ + trapped holes and Tl0 trapped electrons. The first thermal glow results from the mobility of I2− holes, while the second thermal glow and stimulated emission result from the release of electrons from Tl0 centers.

Three distinct emission modes correspond to the three recombination processes. Stimulated electrons returning to I2− centers produce emission bands at 302 and 370 mμ. Electrons recombine with Tl+ + holes to give a 425-mμ emission identical with that from uv excited fluorescence. I2− holes migrating to Tl0 centers produce a broader emission at 425 mμ.

This material is compared to other alkali halide phosphors and also to phosphors in general.
Van der Waals Theory of Transport in Dense Fluids
Authors: Dymond J. H. , Alder B. J.
Published: January 2005

An accurate and simple theory of transport properties is developed on the basis of the van der Waals concept of a dense fluid. It is shown that the calculated values for the transport coefficients for the rare gases at temperatures and densities greater than the respective critical ones agree to within about 10% with the experimental results in both absolute value and temperature dependence, without invoking an activation barrier. In this a priori theory, the cross section, that is, the hard-sphere diameter, is determined as a function of temperature from the available equilibrium data, within the framework of the van der Waals theory.
Conformational Analysis of Macromolecules. III. Helical Structures of Polyglycine and Poly-L-Alanine
Authors: Scott Roy A. , Scheraga Harold A.
Published: January 2005

A theoretical study of the regular conformations of isolated helices (i.e., with no intermolecular interactions) of polyglycine and poly-L-alanine has been carried out. The energy of each helical conformation was calculated by using semiempirical potential functions for the barriers to internal rotation about single bonds, nonbonded interactions, dipole—dipole interactions between the amide groups, and hydrogen bonding between backbone NH and CO groups. All bondlengths and bond angles were held fixed, and the amide group was fixed in the planar trans conformation. Within the accuracy of the calculations, the right and left-handed α-helical conformations were found to be those of lowest energy for polyglycine. For poly-L-alanine, the right-handed α helix was found to be the most stable conformation. This conformation was stabilized not only by hydrogen bonding and dipole—dipole interactions, but also by the nonbonded interactions; in fact, it is the nonbonded energy which makes the right-handed α helix more stable than the left-handed one in poly-L-alanine, since dipole—dipole interactions and hydrogen bonding stabilize both structures about equally well. The effect of varying the parameters in the semiempirical potential functions was studied, and the results and conclusions of these calculations were compared with calculations made by other investigators and with experimentally determined polypeptide conformations.
Monte Carlo Studies of Lattice-Model Polymer Chains. I. Correlation Functions in the Statistical-Bead Model
Authors: Verdier Peter H.
Published: January 2005

A method is presented for obtaining correlation functions in the free-draining statistical-bead model (Rouse model) of a polymer chain. Autocorrelation functions for the squares of end-to-end length and radius of gyration are given as functions of the number of statistical segments in the chain.
Molecular-Beam Scattering from the (111) Plane of Silver
Authors: Saltsburg Howard , Smith Joe N.
Published: January 2005

The spatial distributions of molecular beams of CH4, NH3, He, Ne, Ar, and Xe scattered from the (111) plane of an epitaxially grown Ag single crystal have been examined both during growth of the Ag crystal and immediately afterward, and no distinction between these modes was observable. The scattering of Ne, CH4, and NH3 has been compared to illustrate the important role of the gas—metal interaction energy; NH3, the most strongly interacting gas, gives rise to nearly diffuse scattering, while Ne is nearly specularly directed. Although the scattering of He is essentially specularly directed at all incident angles and temperatures, the heavier gases (Ar and Xe) exhibit scattering maxima lying between the specular direction and the tangent to the surface (supraspecular scattering), with the location of the maxima depending in a complex manner on the angle of incidence of the beam and the beam energy. Since a necessary condition for supraspecularity is that the beam temperature be greater than the surface temperature, an energy-transfer step seems to be involved in determining the particle trajectory. Similar complexities in the intensity of the scattered-beam maxima are observed; however, no simple explanation seems to suffice in this case.
Transition Probabilities of Forbidden Oxygen Lines in a Discharge Tube
Authors: LeBlanc F. J. , Oldenberg O. , Carleton N. P.
Published: January 2005

We have studied emission of the four forbidden lines of atomic oxygen, λλ 6364, 6300, 5577, and 2972 Å from a discharge through flowing tank oxygen at pressures of a few torricelli, in a tube of 8 mm i.d., with 40–120 mA of current flowing. We found that under these discharge conditions none of the lines were perceptibly broadened or shifted (to within 0.2 Å), and that none showed any response to changes in conditions that would suggest collisional stimulation of emission. Hence we conclude that the emission of these lines is governed by their true radiative transition probabilities. Typical intensities were, for the four lines (in units of photons per cubic centimeter·second): 3.3×109, 1.0×1010, 4.0×1010, and 1.8×109, respectively. The ratio of intensities of 5577 and 2972 Å (which have the common upper level 1S) has a constant value of 22±2 within the range of conditions in which we can observe these lines, as compared with the theoretical value of 16 computed by Garstang. We discuss, in terms of molecular selection rules, the collisional stimulation of the line 5577 Å that is observed by others at high pressures.
Electronic Spectra of Phenanthrene in Mixed Crystals
Authors: Hochstrasser Robin M. , Small Gerald J.
Published: January 2005

The analyses of the 3500-Å polarized absorption, fluorescence (1A1⇄1A1) and phosphorescence (∼4500 Å, 3B2→1A1) spectra of phenanthrene —h10 and d10 (guests) substitutionally dissolved in a biphenyl-(host)-crystal lattice are reported. Considerable attention is given to the role of intramolecular vibronic coupling in the electronic transitions of phenanthrene and a number of vibronic coupling pathways have been elucidated. Several manifestations of guest—host interactions in the phenanthrene spectra have been observed and in particular, evidence is given to show that certain vibronic states of the first excited-singlet-state manifold crystal field mix with the states of the host (biphenyl, fluorene) more effectively than others. The multiplet structure of the vibronic bands in the electronic spectra of phenanthrene in biphenyl previously reported is shown in detail.
Photochemistry of Benzene Vapor at 1849 Å
Authors: Shindo Kotaro , Lipsky Sanford
Published: January 2005

The benzene-disappearance quantum yield at 1849 Å and 1 torr has been determined to be 0.25±0.02 and independent of the number of absorbed quanta to ∼15% conversion. Nitrogen pressures from 0.1 to 50 atm reduce the disappearance yield. At 1 atm N2, the yield is reduced approximately fourfold. Addition of 200 torr propane reduces the yield more than one order of magnitude. At 2 and 3 torr benzene, the quantum yield is reduced to 0.13 and 0.10, respectively, and extrapolates at zero pressure to ∼1.0. Only two major products are found. One is volatile with structured absorption in the region 2600 to 2100 Å. Seventeen peaks are resolved in the spectrum with constant separation of ∼500 cm−1. Assuming that the initial yield of the product is equal to the disappearance yield of benzene, an oscillator strength of 0.2 is calculated for the band with maximum absorptivity of 8300 liters/mole·cm at 2350 Å. The compound is tentatively identified as an isomer of benzene. The second product is of high molecular weight and arises by polymerization of the volatile compound.

It is suggested that the mechanism for benzene disappearance involves internal conversion to the ground electronic state with subsequent rearrangement to produce the benzene isomer.
Electron Spin Resonance Absorption Spectrum of the AsO32− Molecule Ion in γ-Irradiated Single-Crystal Calcite
Authors: Serway R. A. , Marshall S. A.
Published: January 2005

An axially symmetric ESR absorption spectrum consisting of four principal hyperfine-structure components has been observed in γ-irradiated calcite single crystals. The symmetry axis of the spectrum is found to coincide with the crystal [111] direction, and at 77°K the spin-Hamiltonian parameters are given by g∥=2.00162, g⊥=2.00195, A∥=2627.7 Mc/sec, A⊥=2108.8 Mc/sec, eqQ=−2.4 Mc/sec, and gnβn/gβ=−0.00028. From the hyperfine structure multiplicity and the ratio of moments, it is concluded that the paramagnetic center is associated with the 100% naturally abundant 75As nucleus. This spectrum is identified as being due to the AsO32− molecule ion which occurs as a substitution for the CO32− molecule ion in calcite.
Microwave Spectrum, Structure, and Quadrupole Coupling Constants of Spiropentyl Chloride
Authors: Woerner Lloyd M. , Harmony Marlin D.
Published: January 2005

The microwave spectra of C5H735Cl and C5H737Cl have been observed and analyzed. If the spiropentane ring is assumed to be in the D2d configuration, with methylene-group parameters similar to cyclopropyl chloride, the following parameters are calculated from the observed moments of inertia: r(CCl)=1.74 Å, r(CC)=1.51 Å, and ∠RCCl=118°. The quadrupole coupling constants in the inertial axis system have been obtained for both isotopic species. For the 35Cl species, the values are χaa=−30.98 MHz, χbb=6.22 MHz, and χcc=24.76 MHz. Evidence is presented which indicates that the chemical bond linking the chlorine to the ring is not axially symmetric and does not lie along the C–Cl internuclear line.
On the Eu3+ Fluorescence in Mixed Metal Oxides. III. Energy Transfer in Eu3+-Activated Tungstates and Molybdates of the Type Ln2WO6 and Ln2MoO6
Authors: Blasse G. , Bril A.
Published: January 2005

The fluorescence of unactivated and rare-earth-activated materials of the type Ln2WO6, Ln2MoO6, and Y2W1−xMoxO6 (0≤x≤0.1) has been studied. From the experiments on unactivated materials it follows that energy transfer from tungstate to tungstate or mobyldate group takes place, whereas there is no transfer from molybdate to molybdate or tungstate group. Arguments in favor of exchange-regulated energy transfer from tungstate or molybdate group to rare-earth ion are put forward. The efficiencies of the rare-earth-activated tungstates and molybdates can be qualitatively understood assuming a strong dependence of the energy transfer on the angle tungsten (molybdenum)—oxygen—rare earth. In Y2W1−xMoxO6:Eu the molybdate group acts as a killer of the fluorescence under short-wave uv excitation and as a sensitizer under long-wave uv excitation.
Cell Theories for Hard Particles
Authors: Hoover William G. , Alder Berni J.
Published: January 2005

The consequences of each of the three approximations made by Kirkwood in deriving the Lennard-Jones—Devonshire cell theory are elucidated by a comparison with exact results in the one-dimensional case of hard rods. This comparison gives an explicit calculation of the one-dimensional communal entropy and shows that the single-occupancy approximation is exact at close packing, although it does not lead to thermodynamic properties which are analytic functions of density. For two- and three-dimensional systems, numerical results show that the cell-theory entropy predictions are more accurate than in one dimension because the particles are more localized. The more-than-one-particle-per-cell theories provide simple and rigorous lower bounds on the entropy, but the convergence to the thermodynamic limit by considering more and more particles is slow.
Coadsorption of Oxygen and Carbon Monoxide upon a (110) Tungsten Surface
Authors: May J. W. , Germer L. H. , Chang C. C.
Published: January 2005

A (110) surface of W that is covered by ½ a monolayer of O atoms will adsorb about ¼ monolayer of strongly held CO molecules and about half as many weakly held molecules. These are half the amounts that can be adsorbed on a clean (110) face. The CO is desorbed in its original form in two states at about 450° and 1100°K. No CO2 is formed. All the O is removable at 1950°K, apparently as oxides of W. The composite O–CO covered surface is a disordered structure if formed at room temperature, but if this is heated to about 1000°K a complex ordered surface is produced. This structure, having C (11×5) symmetry bears some resemblance to the C(9×5) structure produced in similar fashion without any oxygen. Experiments carried out in reverse order show that oxygen is not adsorbed at room temperature on a surface first saturated with CO, but if a CO saturated surface is held at 1000°K during exposure to O2, the same C(11×5) structure is formed as before. Exposure of a bare (110) surface to CO2 at a pressure below 10−7 torr results in negligible adsorption.
Two-State Theory of the Structure of D2O
Authors: Davis C. M. , Bradley D. L.
Published: January 2005

The two-state approach to the structure of water is applied to D2O. Over the temperature range 4° to 100°C, the molar volume of both the close and open-packed structures is estimated to be approximately the same in D2O as in H2O. The enthalpy difference between the two structures is found to be −2915 cal/mole in D2O compared to −2547 cal/mole in H2O, indicating an increase in the hydrogen-bond strength of D2O compared to that of H2O. Estimates of the relaxational thermodynamic parameters of D2O are obtained. Only those which depend on the enthalpy difference exhibit an appreciable change from the corresponding parameters in H2O.
Mössbauer Effect in the System Sr3Fe2O6–7
Authors: Gallagher P. K. , MacChesney J. B. , Buchanan D. N. E.
Published: January 2005

Previous studies of the Mössbauer effect for iron (IV) have been limited to the perovskitelike compounds SrFeO3 and BaFeO3. The structure of Sr3Fe2O7 is related, consisting of pairs of perovskite layers separated by a layer of strontium and oxygen ions. As in the previous studies of SrFeO3 and BaFeO3, samples of Sr3Fe2O6.9, Sr3Fe2O6.6, and Sr3Fe2O6.0 were prepared by equilibrating prereacted materials at various temperatures and oxygen pressures. Mössbauer spectra, measured at 298° and 4°K, indicated that the specimens of Sr3Fe2O6–7 are magnetically ordered at 4°K. The isomer shift of iron (IV) in Sr3Fe2O6.9 is −0.21 mm/sec at 298°K. The shift was more negative for the samples having a lower oxygen or iron (IV) content. Similarly at 4°K the magnetic hyperfine splitting went from 279 kOe for Sr3Fe2O6.9 to 232 kOe for Sr3Fe2O6.2. Quadrupole splitting was clearly evident in the trivalent component of these spectra and is attributed to the associated oxygen vacancy. The behavior is compared to that previously observed for systems containing iron (IV).
Theoretical Investigation of H3O and H4O+
Authors: Bishop David M.
Published: January 2005

Single-center wavefunctions for H3O and H4O+ for a number of different nuclear configurations have been determined. The molecular energy results together with those of a previous calculation for H3O+ show that the electron affinity of H3O+ is 0.16 a.u. and the proton affinity of H3O is 0.18 a.u. These values lead to the prediction that H3O is unstable with respect to H2O+H and that H4O+ is unstable with respect to H3O++H.
Nonequilibrium Statistical Mechanics of a Multicomponent Fluid
Authors: Jordan P. C. , Jordan J. R.
Published: January 2005

A general theory of linear nonequilibrium statistical mechanics proposed by Baur, Jordan, Jordan, and Mayer is applied to a model system: the multicomponent, chemically nonreactive fluid. This theory centers on the determination of a set of conjugate intensive and extensive thermodynamic variables such that a displacement in any one of these variables relaxes to equilibrium without exciting any of the others. The matrix equations which govern the solution of this problem are determined both via thermodynamics and via statistical mechanics. A complete solution is given for one- and two-component systems and that displacement function corresponding to a sound wave determined for the n-component system. In order for thermodynamics and statistical mechanics to correspond, the Onsager matrix is identified with its microscopic analog. In this way, expressions for transport coefficients are found which are equivalent to those found using more conventional methods. Applications to the problem of light scattering are discussed and general formulas for the ratio of the intensities of the frequency shifted line to the nonfrequency shifted line are determined for multicomponent systems. Possible methods of direct observation of these independently decaying thermodynamic variables (other than the sound wave) are considered.
Electronic Structure and Isomerism in Allene
Authors: Borden Weston Thatcher
Published: January 2005

A Pariser—Parr—Pople-type calculation has been carried out to determine the energies of the electronic states in two conformations of allene, one where the hydrogens on the terminal carbons lie in orthogonal planes and the other where they are coplanar. Using group theory, correlation diagrams have been constructed; and it is predicted that, on excitation to the lowest triplet, the molecule should rotate to the planar isomer.
Dynamical Calculations of Hard-Sphere Packing in a Reflecting Spherical Cell
Authors: Levine Melvin M.
Published: January 2005

Dynamics calculations for hard spheres in a reflecting spherical cell have been carried out on a digital computer. The conditions are chosen so as to force random arrangements to be more stable than ordered ones. The results are compared with free-volume theory and with measurements of packing density in clusters of hard spheres.
Phase-Space Theory of Chemical Kinetics. III. Reactions with Activation Energy
Authors: Lin J. , Light J.
Published: January 2005

The phase-space (or statistical) theory of chemical kinetics has been applied to gas-phase three-body reactions with activation energies. The definition of a strong-coupling complex for reactions of this type has been modified to require the simultaneous satisfaction of an energy and a distance criterion similar to those of simple collision theory. The subsequent breakup of the complex is computed statistically. The theory is applied to reactions of K and HBr, H and Cl2, H and HX (X=Cl, Br, I), H+HD, etc., to determine rate constants, cross sections, isotope ratios, and product excitation (electronic as well as vibrational and rotational). The detailed results of the theory are, in general, consistent with experimental results. The thermal rate coefficients computed by the phase-space theory are usually in good agreement with experiment.
Natural Orbitals for Hydrogen-Molecule Excited States
Authors: Rothenberg Stephen , Davidson Ernest R.
Published: January 2005

The technique of analyzing a many-configuration wavefunction into natural orbitals has been extended to the excited states of H2. All of the low-lying singly excited electronic states up to a principal quantum number of 3 have been investigated and the natural orbitals are given. Plots of some of the orbitals are included to facilitate visualization of the results. From calculated singlet—triplet splittings, it is suggested that the spectroscopic assignment of the triplet levels is approximately 110–140 cm−1 too high for H2.
Mass-Spectrometric Studies of Corona Discharges in Air at Atmospheric Pressures
Authors: Shahin M. M.
Published: January 2005

Mass-spectrometric studies of the ionic species formed in corona discharges in nitrogen, oxygen, and air have been carried out at water concentrations from 1.7×10−2 to 0.65 mole % and total pressures up to one atmosphere. The importance of water in this system has been demonstrated by the dominant presence of (H2O)nH+ ion clusters at water concentrations as low as 4.1×10−2 mole %. Evidence is presented for the formation (HO2)+ and (N2H)+ ions as possible intermediates in the formation of these clusters. It is argued that hydride formation by the primary ions and possibly charge-exchange reaction with water molecules followed by proton-transfer reactions are the mechanisms by which these clusters are produced. Simple hydration of other ionic species of the discharge, e.g., O2+(H2O)n, NO+(H2O)n, and (NO2+) (H2O)n, at water concentrations below 5.5×10−2 mole % have also been observed.
On the Multiplicity of the Phosphorescent State of Organic Molecules
Authors: Azumi Tohru , O'Donnell C. M. , McGlynn S. P.
Published: January 2005

The value of the ``multiplicity'' gu for use in the equation kp=2πcν2n2(gl/gu) ∫ εdν̄ is discussed and shown to lie in the range 1 ≤gu≤∞. The value best suited to most organic compounds at 77°K is shown to be gu=3. The number of emitting triplet components is shown to be readily derivable for large classes of compounds and to correlate with experiment. The effects of magnetic-field strength on triplet component energies, on phosphorescence lifetime, on phosphorescence polarization, and on gu are calculated and shown to produce large effects in the specific case of naphthalene-d8.
Crystal Structure of the Transition-Metal Molybdates and Tungstates. II. Diamagnetic Sc2(WO4)3
Authors: Abrahams S. C. , Bernstein J. L.
Published: January 2005

Sc2(WO4)3, diamagnetic above 30°K, crystallizes in the orthorhombic system, Space Group Pnca, with lattice constants a=9.596±0.004, b=13.330±0.003, and c=9.512±0.004 Å at 298°K. The complete x-ray scattering pattern within a reciprocal lattice hemisphere of radius (sinθ)/λ=1.02 Å−1 was measured with PEXRAD. The crystal structure was solved by use of three-dimen sional Patterson and Fourier series and refined by the method of least squares, using 1731 independent structure factors. The final agreement factor R is 0.0622. Scandium atoms occupy slightly distorted octahedra, with average Sc–O=2.063 Å and Sc–O distances ranging from 2.026±0.015 to 2.124±0.010 Å. Two crystallographically independent W atoms are surrounded by somewhat distorted tetrahedra: the W–O distances vary from 1.695±0.009 to 1.829±0.016 Å, the average being 1.761 Å. The thermal vibrations are significantly anisotropic. Sc2(WO4)3 forms the structure type for 23 trivalent metal tungstates and molybdates, including the nine smaller rare-earth tungstates. The larger rare-earth tungstates, crystallizing in the Eu2(WO4)3 structure type, have 8 coordination about the rare-earth ion; the smaller have 6 coordination. A simple correlation is found between the variation in radius ratio due to the lanthanide contraction and the change in coordination.
Flash Photolysis of Matrix-Isolated Cyanogen Azide in Solid Nitrogen
Authors: Schoen Louis J.
Published: January 2005

Flash photolysis combined with matrix-isolation spectroscopy has been employed to investigate the decomposition of a cyanogen azide—nitrogen solid at 20.4°K. Two primary processes have been observed leading to the formation of NCN radicals either in an electronically excited 1Δg level or in the 3Σg− ground state. The first-order decay of NCN (1Δg) has been studied and the mean lifetime in the solid found to be approximately 500 μsec.
Semiempirical Molecular Orbital Calculations. II. The Nonbonding Orbital, the Electronic Spectrum, and the Spin—Orbit Coupling in X2CO Molecules
Authors: Carroll D. G. , Vanquickenborne L. G. , McGlynn S. P.
Published: January 2005

Phosphorescence lifetimes have been calculated for the T1→S0(π*→n) transition in formaldehyde and some of its halogen substituents. The wavefunctions used were obtained by a charge self-consistent Wolfsberg—Helmholz method. The so-called n orbital on the oxygen atom is mixed with carbon and halogen p orbitals to a considerable extent. As a consequence, one-center terms on the halogens have to be considered in the evaluation of spin—orbit coupling matrix elements. The results indicate a considerable internal heavy-atom effect on the (π*→n) phosphorescence lifetimes of formaldehyde derivatives. The available experimental evidence agrees with this conclusion.
Interaction of Oxygen with Hot Tungsten
Authors: Singleton J. H.
Published: January 2005

The reaction of oxygen at a polycrystalline tungsten surface has been studied over a temperature range from 1300° to 2450°K and for oxygen pressures from ∼10−5 to ∼10−8 torr. A mass spectrometer was used to measure the oxygen pressure. In determining absolute pressures care was taken to avoid errors which may arise due to spurious currents in a Bayard—Alpert ion gauge. The efficiency of removal of carbon impurity from tungsten, by heating in oxygen, was determined. After obtaining a low carbon content, the rates of removal of oxygen at the tungsten surface were determined as a function of temperature. At temperatures below ∼2000°K evaporation of oxides of tungsten occurs at predictable rates. At higher temperatures atomic oxygen is produced and the observed rate of removal of oxygen is strongly influenced by the specific surfaces present in the entire system. For example, a silver surface efficiently reacts with oxygen atoms, without apparent saturation, to give a large apparent increase in the pumping speed at a tungsten surface enclosed in a glass system.
Electron Spin Resonance of Met-Myoglobin: Field Dependence of g⊥eff
Authors: Eisenberger P. , Pershan P. S.
Published: January 2005

The spin Hamiltonian for high-spin Fe3+ in single crystals of met-myoglobin has the form Hs=D(Sz2−25/4)+g| |βHzSz+g⊥β(HxSx+HySy). In view of the large value of D the only ESR signal that can be observed is the transition from the ms=—½ to ms=+½ states. The resonance condition for the ground doublet is described by geffβH=hν. When the magnetic field is applied along the z axis g∥eff=g∥ and when the magnetic field is applied perpendicular to the z axis g⊥eff=3g⊥[1–2(g⊥βH)2(2D)−2]. Through measurement of g⊥eff and g∥eff at 13 and 35 Gc/sec the spin-Hamiltonian parameters were found to be g∥=2.002±0.001, g⊥=1.985±0.002, and 2D=8.76±1.2, cm−1.

These results are interpreted by replacing the pure 3d wavefunctions from which the (3d)5 electronic configuration of Fe3+ is usually formed by covalent molecular orbitals which are only part 3d. The values for g∥, g⊥, and D can be explained in terms of a single low-lying pure antibonding state of 4A2 symmetry 2000 cm−1 above the 6A1 ground state and coupled to it by the spin—orbit interaction. Numerical agreement between theory and experiment requires molecular orbits which have an average 3d character of only 68%. These highly covalent orbitals are in very good agreement with the theoretical results of Zerner and Gouterman.
Excitation Energy in the Nuclear Spin—Spin Interaction
Authors: Duval Eugène
Published: January 2005

Valence bond theory, Dirac's vector model, and a perturbation calculation express the coupling constant between nuclear spins as a function of exchange integrals. The approximation of mean excitation energy is not utilized. The singlet states are represented by the product of singlet functions of two electrons in one bond, or singlet functions of four electrons in two bonds, while the triplet states are represented by the product of one triplet function of two electrons in one bond, and of the preceding singlet functions. The different transfer processes of the excitation from a nucleus to the other in the molecule are given.
Atomic and Molecular Calculations with the Pseudopotential Method. I. The Binding Energy and Equilibrium Internuclear Distance of the Na2 Molecule
Authors: Szasz Levente , McGinn George
Published: January 2005

The dissociation energy and equilibrium internuclear distance of the Na2 molecule is calculated with the pseudopotential method. It is assumed that the molecule consists of two closed-shell Na+ electron cores which do not participate in the binding plus two valence electrons which are responsible for the binding. The two valence electrons are moving in the potential field of the two Na+ cores. For the interaction potential of the two valence electrons with the two cores an expression is derived, which consists of two parts: (1) of the Hartree—Fock potentials of the cores, (2) of the so-called pseudopotentials. We are using the approximation in which the requirement that the wavefunction of the valence electrons must be orthogonal to the wavefunctions of the electrons in the cores is removed and replaced by the so-called pseudopotential. In the present calculations we use Hellmann's expression for the pseudopotential. The wavefunction of the valence electrons is a Heitler—London-type function plus an ionic term, both built from hydrogenic 1s-type functions. From the energy minimum principle we obtain for the dissociation energy and equilibrium internuclear distance the values D=0.232 eV and R=6.18 a.u. (experimental values: D=0.74 eV and R=5.80 a.u.).
Theoretical Interpretation of 31P NMR Chemical Shifts. II. Unsymmetrical Molecules
Authors: Letcher John H. , Van Wazer John R.
Published: January 2005

An ASP LCAO MO quantum-mechanical calculation of the 31P chemical shifts has been made for molecules of the form PZ2T and MPZ2T, where M is an electron-pair-acceptor atom or group, P is phosphorus, and Z and T are different substituents. The deviations from linearity of the chemical shifts of these mixed species from that predicted by linear interpolation from the shifts of PZ3 and PT3 or of MPZ3 and MPT3 is calculated and used to elucidate molecular parameters such as the extent of π interactions and bond-angle changes in the mixed as compared to the unmixed molecules.
Theoretical Interpretation of 31P NMR Chemical Shifts. III. Phosphorus with Five Like Substituents
Authors: Letcher John H. , Van Wazer John R.
Published: January 2005

Using the assumption that the valence orbital hybridization in compounds of the type PZ5 is such that all five fluorines in PF5 are instantaneously magnetically equivalent even though the two axial bond lengths are longer than the three equatorial ones in this trigonal bipyramidal structure, an ASP LCAO MO quantum-mechanical calculation has been made for the 31P chemical shifts of molecules of the form PZ5. As in the two previous papers of this series, π bonding to the phosphorus is included. On the assumption that the π orbitals of the phosphorus are vacant in the compound P (C6H5)5, the amount of π bonding is estimated for the symmetrically substituted compounds of the type PZ5 on which chemical-shift data are available.
Luminescence of Pyrimidines, Purines, Nucleosides, and Nucleotides at 77°K. The Effect of Ionization and Tautomerization
Authors: Longworth J. W. , Rahn R. O. , Shulman R. G.
Published: January 2005

The luminescence of purines and their corresponding nucleosides and nucleotides has been studied at 77°K for different states of ionization and for some alterations of tautomeric forms. To a first approximation, the excitation spectra always coincided with the absorption spectra. Furthermore the emission profiles were independent of the exciting wavelength and, except for the protonated forms of guanine and its derivatives, phosphorescence always consisted of a single exponential decay. The naturally occurring pyrimidines, uracil, thymine, and cytosine, fluoresced over a wide pH range but only phosphoresced at high pH where they have lost a proton. From a study of methylated pyrimidines it was shown that the lactim forms fluoresced at 300°K and phosphoresced at neutral pH at 77°K. In these two respects they differed from the natural pyrimidines and support the commonly accepted lactam structures for the natural pyrimidines.

The purines, adenine and guanine, and their derivatives fluoresced and phosphoresced in neutral and basic solutions at 77°K. Upon protonation at pH∼4 the emission of AMP was completely quenched, adenosine had its phosphorescence considerably reduced, while the luminescence of adenine was essentially unchanged. The quantum yields, luminescence spectra, and phosphorescence decay times were measured for all the compounds.
Luminescence and Electron Spin Resonance Studies of Adenine in Various Polynucleotides
Authors: Rahn R. O. , Yamane T. , Eisinger J. , Longworth J. W. , Shulman R. G.
Published: January 2005

The excited states of adenine in different polynucleotides dissolved in ethylene glycol: H2O glasses have been studied by optical emission and ESR at 77°K. In single-stranded poly A the optical properties were very similar to the constituent AMP monomers except for a red shift of the luminescence. The ESR Δm=1 transitions were observed with D=0.116 cm−1 and E=0.027 cm−1 for poly A and D=0.119 cm−1 and E=0.027 cm−1 (all ±0.002 cm−1) for AMP. This means that the triplet transfer time is longer than 2×10−10 sec since more rapid triplet—triplet jumping would give a time averaging of E. In the ordered double-helix form of poly A the excited states are completely quenched when one-half of the bases are protonated. In poly (A+2U) and poly (A+2I) ordered copolymers the excited states are also quenched. However in random distributions of U, C, and I in single strands of poly A no quenching was observed. This leads to the conclusion that the hydrogen bonding rather than energy transfer is responsible for the quenching observed in the ordered polymers.
Phosphorescence and Electron Spin Resonance Studies of the uv-Excited Triplet State of DNA
Authors: Rahn R. O. , Shulman R. G. , Longworth J. W.
Published: January 2005

The phosphorescence of native DNA at 77°K is characterized by a broad band peaked at (4480±30) Å, and a decay time of (0.28±0.03) sec. The phosphorescence quantum yield of 0.002 is considerably lower than the quantum yields of AMP and GMP at pH 7. Upon denaturing or degrading, the native DNA phosphorescence was partly replaced by the characteristic phosphorescence from the purines. The native DNA phosphorescence was efficiently quenched by Mn2+ ions bound to the DNA. Poly dAT had a phosphorescence with a decay time of (0.32±0.03) sec which was similar to thymidine at pH 11 but showed no contribution from the adenine residues. Because of the similarity between the DNA and poly dAT phosphorescence, we inferred that the phosphorescence of native DNA originates in the thymine bases. These inferences were confirmed by observations of the ``Δm=2'' transitions of the triplet-state ESR in DNA, poly dAT, and ionized thymidine. The values of Hmin were 1054, 1046, and 1067 G, respectively, all very different from the values of 1360 and 1425 G for GMP and AMP. The absence of a strong guanine phosphorescence and ESR signal was explained by the quenching observed of the guanine triplet in GMP—CMP gels and GMP—poly C complexes. A mechanism explaining the occurrence of ionized thymidine emission in DNA and poly dAT is discussed in terms of a proton being transferred across the N3–H···N1 hydrogen bond to adenine thereby quenching the adenine triplet and stabilizing the thymine triplet.
Pseudopotential Theory of Atomic and Molecular Rydberg States
Authors: Hazi Andrew U. , Rice Stuart A.
Published: January 2005

In this paper we present a description of atomic and molecular Rydberg states using an effective Hamiltonian in the one-electron Hartree—Fock approximation. A pseudopotential is introduced to ensure the orthogonality of the Rydberg orbitals to the core. The core is represented by the ground-state wavefunction of the corresponding positive ion. In order to incorporate the pseudopotential formalism in a description of Rydberg states, the original pseudopotential theory is extended to the case where the core and valence orbitals are eigenfunctions of different one-electron operators. The formalism is applied to the triplet S states of helium and beryllium atoms and the results of numerical calculations are given. Good agreement with experiment is found. Possible extensions of the theory to more complex systems are discussed.
Generalized Second-Order Macroscopic Transport Equations
Authors: Horne Frederick H.
Published: January 2005

A complete set of macroscopic transport equations suitable for application to experiment is obtained from nonequilibrium thermodynamics. Full account is taken of (i) bulk flow, (ii) conservative external fields (gravitational, centrifugal, and electrostatic), (iii) pressure gradients, and (iv) nonconstancy of thermodynamic and transport coefficients. There result 4(v+1) independent partial differential equations for a v-component system. Four of the equations involve only barycentric velocity, external fields, density, viscosity, and pressure. Independent second-order equations are obtained for the temperature distribution and v−1 mass fraction distributions. The remaining 3v equations can be used to calculate the vectorial heat and diffusion fluxes. In order to take account of nonconstancy of viscosities, diffusivities, etc., a Taylor's series expansion in the spatial coordinates is suggested. A perturbation—iteration scheme can then be used to solve the transport equations for the velocities, the fluxes, and the distributions of temperature, pressure, and v−1 mass fractions. The solutions are polynomials in thermodynamic derivatives of the thermodynamic and transport coefficients.
Spectroscopy of Carbon Vapor Condensed in Rare-Gas Matrices at 4°K. III
Authors: Weltner William , McLeod Donald
Published: January 2005

For C3, controlled warming of neon matrices containing carbon vapor caused the multiple sites for C3 molecules to disappear. The assignments of vibronic transitions in the 1IIu←X1Σg+ system could then be made more definite using the parameters of Gausset, Herzberg, Lagerqvist, and Rosen. Two unaccounted-for bands were attributed to transitions involving v3′≅840 cm−1. This low value was rationalized by comparison with other similar molecules. The 1Σu+←X1Σg+ transition of C3 in a neon matrix was not observed in the ultraviolet out to 1950 Å.

For C2, the spectrum of carbon—neon matrices, before and after warming to 12°K, indicated that the absorption bands in the region of 4000–6000 Å are probably not the C2 Swan system but may be due to a larger carbon molecule. A band at 2320 Å in neon was attributed to the (0, 0) band of the Mulliken system (1Σu+←x1Σg+ of C2. These and other observations indicate that the trapping of C2 in the excited 3IIu state in matrices is doubtful.

CNN is formed in neon matrices containing nitrogen by the reaction of C atoms in carbon vapor with N2. The proportion of C atoms in the vapor and the formation of CNN can be enhanced by vaporization of carbon from thin tungsten or tantalum cells because of the formation and vaporization of the solid carbide.

For Cn, carefully controlled diffusion of carbon molecules relatively concentrated in a neon matrix led to the appearance of many new vibrational bands. These were analyzed in terms of two extreme linear chain models. It is concluded, for example, that C4 is probably best written as ·C≡C–C≡C·, in agreement with theory.
On Polymer Dynamics. II
Authors: Hearst J. E. , Harris R. A. , Beals E.
Published: January 2005

The viscosity, storage and loss moduli, fluctuations in length, Lagrange multiplier, pair-correlation functions, and radius of gyration are evaluated for the model of Harris and Hearst.