bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic and Structural Characteristics of Lanthanide—Copper Compounds
Authors: Walline R. E. , Wallace W. E.
Published: January 2005

Magnetic characteristics and structures of 11 intermetallic compounds represented by the formula LnCu are reported. The compounds with Ln = Ce, Pr, Nd, and Sm occur in the FeB structure; those with Ln = Y, Gd, Tb, Dy, Ho, Er, and Tm have the CsCl structure. YCu is a Pauli paramagnet. The magnetic characteristics of PrCu and NdCu are anomalous and attempts to deduce the nature of the cooperative magnetic phases in these materials, if any, at low temperatures are unsuccessful. Results for the other compounds suggest that they are antiferromagnetic at low temperatures. TbCu and HoCu exhibit two magnetic transitions; the high-temperature transition is interpreted as the Nèel point and the one at the lower temperature as an order—order transition in the antiferromagnetic state. In the paramagnetic region effective moments in good agreement with the free tripositive ion values are observed in all cases except for GdCu and ErCu. A variable moment is observed for ErCu whereas for GdCu a moment of 8.46 μB is obtained.
Nuclear Magnetic Resonance in Molten Salts. II. Chemical Shifts in Thallium Halide—Alkali Halide Mixtures
Authors: Hafner Stefan , Nachtrieb Norman H.
Published: January 2005

The resonance frequency of the 205T1 nucleus in molten solutions of the thallous halides with the corresponding alkali metal halides varies linearly with the mole fraction of the added alkali halide. The direction of the chemical shift depends upon the radius of the alkali cation, being upfield for lithium and sodium halides and downfield for the halides of potassium, rubidium, and cesium relative to the pure thallous halide. For a given mole fraction of alkali halide, δT1 is a linear function of the alkali cation radius. The results provide information on the nature of the interactions between cations and anions in molten salts. The covalent interaction between T1+ and halide ions is decreased by alkali metal ions of small radius and increased by those of large radius.
Partial Wave Theory of Diatomic Molecules. II
Authors: Temkin A. , Bhatia A. K.
Published: January 2005

The method of expanding the wavefunction of diatomic molecules in a series of orbital angular momentum eigenfunctions (partial waves) is extended to two-electron homonuclear molecules. The angular momentum is a function of the Euler angles only; a symmetric choice of these angles is used which greatly facilitates the description of the exchange character of the wavefunction. As a result, explicit equations for the three-dimensional ``radial'' functions can be derived for all the different magnetic, parity, and exchange states. For Σ states the partial wave sums only go over alternate values of the angular momentum giving rise to the expectation of an even more rapidly convergent series in these cases.
Excitation of Methane, Ethane, Ethylene, Propylene, Acetylene, Propyne, and 1-Butyne by Low-Energy Electron Beams
Authors: Bowman C. R. , Miller W. D.
Published: January 2005

Low-energy inelastic collisions between electrons and hydrocarbon molecules are studied by means of a trapped-electron technique. Excitation spectra are obtained over the subionization energy range for methane, ethane, ethylene, propylene, acetylene, propyne, and 1-butyne. Molecular excitation potentials are measured, and relative cross sections are tabulated.
Rearrangement Kinetics of the Liquid—Liquid Immiscible Microphases in Alkali Borosilicate Melts
Authors: Haller Wolfgang
Published: January 2005

Probability calculations are presented which show the high degree of mutual intersection within a population of spheres grown from randomly placed nuclei. It is proposed that the observed networklike structures of the phases of certain liquid—liquid immiscible systems may be due to this statistical lumping. It is further proposed that interfaces of opposite curvature facilitated by this structure rather than polydispersisity give rise to transport phenomena resulting in observable rearrangements in these systems. Equations for a number of transport models are derived.

Liquid—liquid phase separation was induced in alkali borosilicate melts by cooling below immiscibility temperature. Progressive stages of the geometric rearrangements within the microdisperse phases were arrested by undercooling. The kinetics of the decrease in interfacial area between the phases was studied by gas adsorption on the isolated silica-rich phase. It is found that interfacial area is proportional to the reciprocal of the square root of time. Comparison of this result with the rate equations derived for various simplified transport models suggests an interface-controlled bulk diffusion process.

In spite of complications expected from the variety of possible temperature-dependent terms, the process was found to be Arrhenian, having an apparent activation energy of 40 kcal/mole. At present it cannot be decided which mechanism this value supports.
Simultaneous Determination of f Values and Vapor Pressures from Optical Absorption Measurements
Authors: Rice Philip A. , Ragone David V.
Published: January 2005

A method for determining both the f value of an absorption line and the vapor pressure of the absorbing atoms exclusively from optical absorption measurements is defined and discussed. The method depends on making absorption measurements in two regions. The first is at low optical densities, where absorption is linearly proportional to optical density. The second is at higher densities, where the center of the line is fully absorbed and the absorption is proportional to the square root of the optical density. A method for extrapolating measurements from one region to the other is also required. This is accomplished by maintaining a pure liquid in equilibrium with the absorbing vapor species over a temperature range. The method takes into account the effects of collision broadening. Measurements were made on the 3067-Å bismuth line.
Ionization and Excitation of Argon with Alpha Particles
Authors: Hurst G. S. , Bortner T. E. , Glick R. E.
Published: January 2005

Experimental data on alpha-particle ionization of binary mixtures of gases involving argon suggest that two states of electronic excitation persist long enough after the passage of the charged particle to allow collisions of the type Ar*+X→Ar+X++e— to occur. One of these states is near the metastable levels in argon, approximately 11.6 eV, and the other is at approximately 14 eV. Examination of electron energy loss data and spectroscopic data leads to a tentative identification of these states as resonance levels; thus, their lifetimes are due to the trapping of photons in the apparatus. Ionization yield data are fitted to a kinetic model representing the above suggested mechanism with good agreement between the model and the experimental data. Other evidence for the existence of excited states of long lifetimes is derived from light emission experiments with argon in which continuous emission spectra suggest Franck—Condon transitions in excited argon molecules.
Derivation of Interatomic Potentials for Inert-Gas Atoms from the Second Virial Coefficient
Authors: Kingston A. E.
Published: January 2005

The leading term in the series representation of the long-range interaction between two inert-gas atoms A and B has the form —Cab/r6, where r is the distance between the atoms. Accurate theoretical calculations of these C's show that there is a large discrepancy between the theoretically calculated C's and those usually derived from experimental data on viscosity, the second virial coefficient, and low-energy elastic scattering. Here we re-examine recent experimental data on the second virial coefficient and find that in general the Lennard-Jones (12–6) potential is not a good representation of the true interatomic potential. By considering a slightly more complicated potential we show that the theoretically calculated C's are not, in fact, inconsistent with the experimental second virial coefficient data.
Electron Capture by Protons Passing through Molecular Hydrogen
Authors: Sural D. P. , Sil N. C.
Published: January 2005

The cross section for the process p+H2=H+H2+ is calculated from low to moderate energies using the impact-parameter formulation with a two-state approximation. The experimentally measured cross section in this energy range shows a rise and fall with increasing energy of the incident proton; our theoretical calculation reproduces the same behavior with the maximum position slightly shifted towards the lower energy.
Conduction of Electricity in Insulating Liquids
Authors: Silver M.
Published: January 2005

A theoretical model for conduction of electricity in insulating liquids based on some calculations of J. J. Thomson is presented. The theory shows that from measurements of the potential distribution one can independently obtain values for formation and motion of the mobile charges.
High-Temperature Vaporization and Thermodynamic Properties of Titanium Monosulfide
Authors: Franzen Hugo F. , Gilles Paul W.
Published: January 2005

A high-temperature investigation of the vaporization of titanium monosulfide has been accomplished through the use of total collection Knudsen effusion measurements, mass spectrometric analysis of the vapor, and x-ray diffraction studies of the condensed phases. The vaporization of stoichiometric TiS has been shown to be congruent, and the products are TiS molecules and probably Ti and S atoms. Thirty-eight vapor pressure measurements over the temperature range 1804°—2186°K give second-law and third-law heats of sublimation ΔH298° as 127.8±3.0 and 132.6±3.0 kcal/mole, respectively, in good agreement with each other. Reliable values, for the vapor pressure calculated as if TiS(g) is the only species, and for the mass transport, can be obtained from the equation logPE(atm) = —(2.575±0.029)×104/T+7.21±0.14, or from the third-law heat of sublimation and tabulated free energy functions.

The melting point of the monosulfide is 2200±20°K. Two new crystalline phases in the Ti–S system have been found.
Temperature and Wavelength Dependence of the Thermal Emission and O–NO Recombination Spectra of NO2
Authors: Levitt B. P.
Published: January 2005

The thermal emission spectrum of shock-heated NO2 has been measured from 4000 to 9500 Å at 2000°K. The bulk of the emission lies in the near infrared rather than in the visible. NO2 is at least 15 times as efficient as Ar in quenching NO2* due to the step NO2*+NO2→NO+NO3, k≈(9×108) T½ liter mole−1·sec−1. N2 as diluent behaves like a monatomic gas (Ar) at a translational temperature corresponding to rotational but not vibrational relaxation behind the front; the excitation is uncoupled to the rotational and vibrational temperature of N2. The radiative lifetime of NO2 is approximately equal to 10−7 sec. In systems containing O, NO, and NO2 the total emission can be resolved into contributions from thermal and recombination emissions; combining literature values the ``rate'' for O+NO→NO2+hv can be written (1.1×1011) T−1.59 exp (670/RT) cc mole−1·sec−1. Thermal and recombination contributions to the equilibrium emissivity of hot air are estimated.
Infrared Spectra of Highly Compressed Gas Mixtures of the Type HCl+X. A Theoretical Study
Authors: Bratož S. , Martin M. L.
Published: January 2005

A theory is proposed to explain the ir spectra of highly compressed gas mixtures of the type HCl+X (or HBr, HF with X=He, Ar, Xe, N2, CO, etc.). This theory is based on the following three hypotheses: (1) The compressed mixture is formed of three molecular species, free HCl (or HBr, HF, etc.), free X, and bound van der Waals molecules (HCl···X). (2) In thermodynamic equilibrium, the system is subject to the law of mass action: HCl+X⇌(HCl···X). (3) The equilibrium constant is given by the standard formula K(T) = exp(—ΔF/RT). Using these hypotheses, the spectral perturbations are explained in terms of the calculated properties of the bound van der Waals molecules. The theory predicts that three limiting types of van der Waals molecules exist according to whether the energy of coupling between the rotation of HCl and the over-all rotation of the complex is (1) smaller than the energy of the over-all rotation of the complex [Coupling Case (1)], (2) larger than the energy of the over-all rotation of the complex but smaller than the energy of the rotation of HCl [Coupling Case (b)], (3) much larger than the energy of rotation of HCl [Coupling Case (c)]. The energy expressions are given for the three coupling cases, the equilibrium constants K (T) are calculated and the spectral perturbations are analyzed. In particular, the fine structure of the induced band is discussed.
Infrared Spectrum and Molecular Structure of B2O3
Authors: Hanst Philip L. , Early Vincent H. , Klemperer William
Published: January 2005

The infrared spectra of B2O3 and HBO2 vapors have been re-examined by means of a long-path high-temperature absorption cell. The vibrational spectrum previously assigned to B2O3 now appears to be due to HBO2. Since the band near 2000 cm−1, indicating the presence of boron—oxygen double bonds, apparently belongs not to B2O3, but to HBO2, a V-shaped structure for the B2O3 molecule appears unacceptable. The absorption spectrum of B2O3 vapor has one broad feature near 1400 cm−1 which can be correlated with B2O3 bands observed in an inert gas matrix. The present spectra and a reanalysis of previously published matrix spectra are shown to be consistent with a bipyramidal B2O3 structure of symmetry D3h.
Triplet State ESR of Metal Chelate Compounds
Authors: Brown I. M. , Weissman S. I. , Snyder L. C.
Published: January 2005

The electron spin resonance spectra of a series of metal chelate compounds are reported. The metals are alkaline earths; the ligands are bidentate and tridentate derivatives of 2,2′-bipyridine and 1,10-phenanthroline and related compounds. The ESR spectra are interpreted as due to randomly oriented molecular triplets. Most spectra can be computer-simulated with a spin-Hamiltonian corresponding to a magnetic dipole—dipole interaction of the unpaired electrons of D≅0.01 cm−1 and E=0. The vanishing value of E is interpreted to mean that the complexes have S4 symmetry with the ligands on opposite sides of the cation and having mutually perpendicular planes. The simulation of some spectra requires a distribution of D and E values which we attribute to interaction with the glassy environment.

The spectra of some potassium chelate dimers are also reported. These characteristically appear to have nonvanishing E values.
Raman and Infrared Spectra of Crystalline Carbon Disulfide
Authors: Ito Mitsuo
Published: January 2005

The Raman and infrared spectra of crystalline CS2 have been observed at low temperatures. The Raman band 2ν2 and the infrared band ν3 have been found to split into two components, while no splitting has been seen for the Raman band ν1. That the rule of mutual exclusion holds for the Raman and infrared spectra of crystalline CS2 indicates the inversion symmetry of the molecule is preserved even in the crystal. A dipole—dipole coupling model for the intermolecular interactions in the crystal explains the band splitting.

Two low-frequency Raman bands have been observed and assigned to the lattice vibrations of rotational mode.
Effect of Translational Energy on Ion-Molecule Reaction Rates. I
Authors: Ryan Keith R. , Futrell Jean H.
Published: January 2005

The specific reaction rates for reactions between ions and molecules when both the reacting partners have thermal energy only have been determined for several systems. These rates have been determined by using a combination of a pulsed ionizing beam followed by a variable time-delay ion-extraction pulse. The results are compared with the field strength dependent values obtained in the same source operated in the conventional manner. The apparent thermal rate constant for the reaction CH4++CH4→CH5++CH3 is 9.6×10−10 cm3 molecule−1 sec−1, but after correction is made for detector discrimination, the value becomes 17.0×10−10 cm3 molecule−1 sec−1. For the field strength dependent values the magnitude of the ionizing current has a strong effect upon the observed specific reaction rate. Operation under conditions where the ionizing current is 0.1 μA led to reproducible values for the specific reaction rates.
Entropy, Internal Energy, and Heat Capacity of MnCl2 between 0° and 4.2°K in Magnetic Fields to 100 kG
Authors: Giauque W. F. , Hornung E. W. , Fisher R. A. , Brodale G. E.
Published: January 2005

The thermodynamically reversible isothermal change of entropy of MnCl2 with magnetic field directed along the b magnetic axis has been measured calorimetrically. At 1.498°K (∂S/∂H)T is positive below 7.5 kG, then negative to magnetic saturation. At 1.333°K, (∂S/∂H)T is negative below 4.5 kG, then positive to 9.25 kG, after which it is negative to saturation. The isothermal entropy change with field has also been measured by a two-step process, in which: (1) the internal-energy change was obtained by combining calorimetric measurements with irreversible magnetic work; (2) combining the internal-energy change with reversible measurements of magnetic work. Measurements of heat capacity in constant fields have been repeated to improve accuracy and to apply a severe test of magnetothermodynamic reversibility by series of measurements made after varied approaches to the starting conditions. The entropy, internal energy, and heat content have been given over the range 0–4.2°K and 0–100 kG, and there are evidently no transition points in the entire area investigated, although gradual changes in magnetic structural types undoubtedly occur. Some values of the heat capacity at constant magnetic moment have been calculated.
Infrared Spectrum of Matrix-Isolated NO2
Authors: St. Louis Robert V. , Crawford Bryce
Published: January 2005

The infrared spectrum of NO2, suspended in oxygen and argon matrices at helium temperature, is described. The spectra are similar to those previously reported, but many new absorptions are observed as well. The absorptions are assigned among the molecular species NO2, stable N2O4, and three unstable forms of N2O4.
Crystal Structures of Manganese(II) and Iron(II) Chloride Dihydrate
Authors: Morosin Bruno , Graeber Edward J.
Published: January 2005

The crystal structures at 298°K of MnCl2·2H2O and FeCl2·2H2O have been refined by means of three-dimensional differential syntheses using diffractometer single-crystal x-ray-intensity data. The crystal structures of these isomorphic compounds consist of polymeric chains of metal and chlorine ions arranged in a near-square planar configuration with each chlorine ion shared by two metal ions. The water molecules which fill the remaining octahedral positions about the metal ion link adjacent chains, paralleling the c axis, by hydrogen bonds.
Molecular Vibrations of Quinones. IV. Raman Spectra of p-Benzoquinone and Its Centrosymmetrically Substituted Isotopic Derivatives and Assignment of Observed Frequencies
Authors: Stammreich H. , Sans Th. Teixeira
Published: January 2005

The Raman spectra of p-benzoquinone, quinone-d4, quinone-18O2, quinone-d4-18O2, and quinone-2,5-d2, excited by the helium radiation 5875.6 Å, are reported, together with semiquantitative measurements of the intensities and qualitative observations on the state of polarization of the Raman shifts. The results are fully consistent with the D2h symmetry of the four molecular species mentioned first, the last one belonging to the point group C2h. A tentative assignment for all Raman-active fundamental vibrational modes of the investigated compounds is given.
Molecular Vibrations of Quinones. VI. A Vibrational Assignment for p-Benzoquinone and Six Isotopic Derivatives. Thermodynamic Functions of p-Benzoquinone
Authors: Becker Edwin D. , Charney Elliot , Anno Tosinobu
Published: January 2005

A complete assignment of the vibrational fundamentals of p-benzoquinone, Qu-d4, Qu-d1, Qu-2,5-d2, Qu-2,6-d2, Qu-18O2, and Qu-d4-18O2 is presented and discussed in detail. By using new infrared and Raman data, as well as a normal coordinate analysis, all for a number of isotopic derivatives, we have been able to substantiate some assignments previously made more speculatively for ordinary quinone itself (Anno and Sado, Davies and Prichard) and to modify other aspects of these previous assignments. Many independent product rule checks have been obtained and are generally quite satisfactory. The thermodynamic functions, CP°, S°, (H°–H0°)/T, and (F°–H0°)/T, are tabulated at various temperatures for Qu and Qu-d4.
Intermolecular Energy Transfer from Excited Organic Compounds to Rare-Earth Ions in Dilute Solutions
Authors: Heller Adam , Wasserman Edel
Published: January 2005

Population of luminescent levels of rare-earth ions in solution has been accomplished through energy transfer from excited, nonchelated organic molecules. Twenty-one aromatic aldehydes and ketones have been shown to be capable of transferring energy to Tb3+ or to Eu3+. It is suggested that a diffusion-controlled process is necessary for transfer and the lowest triplet state of the organic excites the ion. Possible applications as laser materials are briefly considered.
Determination of Pi-Electron Spin Densities in Aromatic Free Radicals by Linewidth Studies of Electron Spin Resonance Spectra: The 3,5-Difluoronitrobenzene Anion
Authors: Kaplan Michael , Bolton James R. , Fraenkel George K.
Published: January 2005

A method is proposed for the determination of pi-electron spin densities in aromatic free radicals which is independent of calculations of sigma—pi interactions. It employs linewidth studies of solution spectra of free radicals and is based on the line broadening arising from electron—nuclear anisotropic intramolecular magnetic—dipole interactions. The method is most readily applied to the hyperfine splittings from the nuclei of atoms which have electrons conjugated with the pi-electron system, such as carbon, nitrogen, or fluorine, rather than to proton splittings, and yields directly the ratios of spin densities on different atoms.

Application of the technique has been made to the determination of the spin density on the fluorine atoms in the 3,5-difluoronitrobenzene anion radical. The fluorine spin density is found to be 1—%2% of the spin density on the nitrogen atom of the nitro group, and within a factor of about two is given by |ρF|=0.003. Although the signs of the fluorine splitting aF and the fluorine spin density ρF were found to be the same experimentally, the data on this radical alone were not sufficient to determine the sign of either ρF or aF. An examination of the data from this and other investigations, however, indicates that ρF is probably negative. It was concluded that it is not yet possible to formulate a satisfactory account of the fluorine splittings in terms of the pi-electron spin densities, i.e., sufficient data are not available to evaluate reliably the sigma—pi parameters for fluorine.
Analysis of the Ionization of Cesium in Tungsten Capillaries
Authors: Forrester A. Theodore
Published: January 2005

The transport of cesium through a tungsten capillary occurs through two phases, an adsorbed layer and a vapor. In this analysis these two phases are connected by the experimentally observed relationship, rather than by any linearized approximation to it. The choice of allowed solutions is then made by a precise boundary matching to solutions computed for the surface onto which the capillary opens. This analysis leads naturally to the possible existence of three different states of the system over a range of capillary sizes, temperatures, and flow-rate conditions. These three states have been correlated with the front-surface emitting, pore emitting, and nonemitting states which have been observed to coexist for a porous ionizer. It is predicted that the coexistence of three different states will disappear when the capillaries become extremely fine.
Anisotropic Zeeman Effect in Erbium Ethylsulfate When the Magnetic Field is Perpendicular to the C Uniaxis of the Crystal
Authors: Spedding F. H. , Haas W. J. , Sutherland W. L. , Eckroth C. A.
Published: January 2005

When single crystals of erbium ethylsulfate, possessing C26h symmetry, were placed in a magnetic field with the direction of the field, the direction of the incident light, and the crystalline c axis mutually perpendicular, the energy and intensity of certain of the absorption lines were found to exhibit a dependence on the angle φm between the direction of the magnetic field and a newly-defined crystalline x axis. Both the energy and intensity were periodic under 60° rotation about the c axis, but the maximum or minimum energy of every line occurred at φm=0°+n60°, while the maximum or minimum intensities of all the lines did not occur at a common angle. The energies of the levels, and their rotation coefficients and Zeeman splittings were determined for the ground term and for the line group at 27 500 cm−1. The spectral data were used in the measurement of the angle φ̄ between the usual crystallographic a axis and the x axis. This angle is a new observable which is a consequence of the C3h point symmetry at the rare-earth ion site and which is characteristic of the crystalline environment. The experimental findings are in qualitative agreement with the theoretical work of Murao, Spedding, and Good, and with the results of our extended calculations.
Approximate Formulas for the Viscosity and Thermal Conductivity of Gas Mixtures. II
Authors: Brokaw Richard S.
Published: January 2005

Approximate expressions for the viscosity and thermal conductivity of monatomic gas mixtures have been derived from the rigorous kinetic theory formulas for binary mixtures. The approximations, which are of the Sutherland—Wassiljewa form, are compared with rigorous calculations for binary and ternary mixtures of the noble gases. These approximations are very accurate: maximum errors are three parts in ten thousand for viscosity (He–Ne–Ar at 20°C) and seven parts in ten thousand for thermal conductivity (He–Kr–Xe at 29°C); the corresponding root-mean-square errors for all the calculations are 0.015% for viscosity and 0.036% for thermal conductivity. Thus, these approximations seem adequate for all practical applications; indeed, if greater accuracy is required, the higher Chapman—Enskog approximations should be considered as well.
Polymethylene Chains and Rings on a Diamond Lattice with Atom Overlap Excluded
Authors: Smith Richard P.
Published: January 2005

A study has been made of alkane-type chains of N bonds on a diamond lattice with atom overlap (both carbon and hydrogen) excluded. An exact enumeration of all allowed chains and their end-to-end distances and numbers of trans bonds has been made for chains of up to 18 bonds. The allowed polymethylene rings have also been determined through 18 bonds. The results have been compared with those for the simple model in which only gauche—gauche prime sequences are disallowed. The number of configurations and the fraction of trans bonds do not appear to differ significantly for the two models. Definite conclusions regarding the mean-square end-to-end distance cannot be drawn from the enumerations reported here, but the two models probably are not in serious disagreement if N is not more than a few thousand.
Absorption Spectra of the Pink and Lewis—Rayleigh Afterglows of Nitrogen in the Vacuum-uv Region
Authors: Tanaka Y. , Innes F. R. , Jursa A. S. , Nakamura M.
Published: January 2005

The absorption spectrum of the pink afterglow of nitrogen in the 1080–1900-Å region has been studied in an attempt to determine the active substances responsible for the production of the afterglow. The Lewis—Rayleigh afterglow, which appears in conjunction with the pink afterglow was also studied, and various features of the two afterglows are compared. The afterglows were studied at room temperature and at liquid-nitrogen temperature. Comparison was made between the emission spectra of an ordinary discharge of nitrogen and the absorption spectrum of the pink afterglow.

Most of the absorption bands observed in the pink afterglow were found to originate in the higher vibration levels of the ground state of N2, which indicates the presence of highly vibrating ground-state molecules in activated nitrogen. The upper states of the absorption bands were determined to be the b, b′, g, j, m, o, q, r, and possibly other states. Bass' results are discussed and compared with those of the present work.
Infrared and Raman Spectra of Krypton Difluoride
Authors: Claassen Howard H. , Goodman Gordon L. , Malm John G. , Schreiner Felix
Published: January 2005

The infrared and Raman spectra of KrF2 vapor have been obtained. They clearly indicate a linear and symmetric molecule with the symmetric stretching frequency at 449 cm−1, the asymmetric stretching frequency at 588 cm−1, and the bending frequency at 232.6 cm−1. The force constants are fr=2.46, frr=−0.20, and fα=0.21 mdyn/Å. The negative bond—bond interaction constant can be explained neither by valence bond models nor by a simple molecular orbital model.
Luminescence of Solids Excited by Surface Recombination of Atoms. IV. Mechanisms of Excitation and Luminescence
Authors: Sancier K. M. , Schott D. J. , Wise H.
Published: January 2005

This experimental study examines processes of excitation and luminescence of solids subjected to surface-catalyzed atom recombination and to photoexcitation. Fourteen lumophors were tested for their luminescence response to nitrogen atoms, to oxygen atoms, and to photoexcitation. The results indicate that photoexcitation processes provide inadequate criteria for atom-excited luminescence. For three of these lumophors, measurements were also made of the atom recombination coefficient and the heat flux due to atom recombination.

The greater response of CaO lumophors to atom excitation than to photoexcitation is attributed to luminescence centers at the surface which permit close coupling with surface-recombining atoms. The decrease in luminescence response of CaO caused by exposure to oxygen atoms is attributed to electron transfer from the luminescence centers to the adsorbed oxygen species, and to reaction of adsorbed oxygen species with oxygen-ion vacancies. Nitrogen atoms, however, cause no decrease in luminescence and are even able to restore the luminescence response of a lumophor previously exposed to oxygen atoms.

Mechanisms of excitation of CaO lumophors and of reduced luminescence response to oxygen atoms are discussed in terms of an energy-band model.
Infrared Intensities of the Fundamental Vibrations of GeH4 and GeD4
Authors: Levin Ira W.
Published: January 2005

The absolute infrared absorption intensities of the fundamental vibrations of GeH4 and GeD4 have been measured using nitrogen pressures of 900 psi to broaden the individual rotational lines. Alternative sets of the derivatives of the dipole moment with respect to designated stretching and bending symmetry coordinates are obtained. A least-squares analysis of the isotopic data indicates that the positive ratio of the two dipole-moment derivatives is the preferred solution.
Conversion of Ion Types in Nitrogen
Authors: Woo Shien-Biau
Published: January 2005

A single-shutter drift tube, together with a hot-filament-type ion source, was used to investigate the conversion and drift properties of ions in nitrogen. Three different species of ions, namely N+, N2+, and N3+, were detected, and their drift velocities in nitrogen were measured over a range of E/p0 (ratio of electric field strength to pressure) from 10 to 200 V/(cm·mm Hg). N2+ was found to undergo time-rate-controlled conversion to N3+. Theoretical solutions of such a drift transient have been obtained and were compared with experiment. The attachment frequency α was deduced from the transient form, and its dependence on pressure and E/p0 measured. It was found that α∝p02 exp[A (−E/p0) ].
Far-Infrared Spectra of Anhydrous Metallic Nitrates
Authors: Ferraro J. R. , Walker A.
Published: January 2005

The far-infrared spectra from 350 to 70 cm−1 of the anhydrous nitrates of Li, Na, K, Ca, Sr, Ba, Ag, Pb, Cu, Zn, Co, Mn, Nd, and Cd are reported. The possible nature of these absorptions is discussed.
Comparison of the Infrared Spectra (4000–70 cm−1) of Several Hydrated and Anhydrous Salts of Transition Metals
Authors: Ferraro J. R. , Walker A.
Published: January 2005

The infrared spectra from 4000 to 70 cm−1 of several hydrated and anhydrous salts of transition metals have been obtained. A comparison of the spectra of a hydrate with a full coordination shell of water, of a lower hydrate, and of the anhydrous salt is made. Differences in the spectra are discussed.
Enthalpies of Mixing in Some Binary Liquid Halide Mixtures
Authors: Hersh Leroy S. , Kleppa O. J.
Published: January 2005

The enthalpies of mixing in the binary liquid alkali chloride, bromide, and iodide mixtures in the mixtures of silver chloride with the alkali chlorides and thallium chloride and in the mixture of silver bromide with thallium bromide have been measured by means of high-temperature reaction calorimetry. The results are discussed in terms of the conformal solution theory for fused-salt mixtures of Reiss, Katz, and Kleppa and the recent perturbation theory of Davis and Rice.

For the binary alkali halides, the molar enthalpies of mixing are represented by the following approximate relation: HM=N1N2(U0++−340δ122) kcal/mole.

Here N1 and N2 are mole fractions and δ12=(d1−d2)/d1d2, where d1 and d2 are the sums of the ionic radii for the two salts. The positive term U0+ + differs from system to system. It represents a theoretical estimate of the contribution to the mixing enthalpy arising from the dispersion energy between next-nearest-neighbor cations, calculated by the method of Mayer.

The above relation does not hold for the silver halide mixtures, for which the corresponding semiempirical relation is: HM=N1N2(U0+++40δ12−340δ122) kcal/mole.

This expression is of the form predicted by the perturbation theory of Davis and Rice. However, a comparison of the silver chloride systems with the previously explored silver nitrate—alkali nitrate mixtures indicates that it is difficult to account for the results in terms of ionic and dispersion interactions alone without invoking also a small degree of covalent bonding in the silver salts.
Kinetic Study of the Decomposition of Cesium—Graphite Lamellar Compounds
Authors: Salzano F. J. , Aronson S.
Published: January 2005

A kinetic study of the decomposition of the cesium—graphite lamellar compounds in vacuo has been carried out over the temperature range 400° to 650°C. A tracer technique was used in which the concentration of cesium in the compounds was measured by a scintillation scanning probe which continuously monitored the activity of tracer 134Cs. The decomposition of the cesium—graphite compounds proceeds in distinct stages. Within each stage, a constant rate of decomposition is observed. Each stage corresponds to the transition of one cesium—graphite compound to a compound containing less cesium.

The observed rates of decomposition can be explained by assuming the rate-limiting process to be the evaporation of cesium from the external surface of the solid. The proposed mechanism correlates the kinetic data with the thermodynamic properties of the compounds.
Transport Collision Integrals for Gases Obeying 9–6 and 28–7 Potentials
Authors: Smith Francis J. , Mason E. A. , Munn R. J.
Published: January 2005

Collision integrals for the 9–6 and 28–7 potentials are tabulated over a range of reduced temperatures kT/ε from 0.01 to 100. The results are compared with previous results for the 12–6 and ∞−6 potentials, including a simultaneous analysis of second virial coefficients for all four potentials. The viscosities are rather similar over wide temperature ranges, but the isotopic thermal-diffusion factors differ markedly.
Infrared Spectrum and Vibrational Assignment for Chlorine Monoxide, Cl2O
Authors: Rochkind Mark M. , Pimentel George C.
Published: January 2005

Infrared studies of chlorine monoxide (16O and 18O) in the region 200–4000 cm−1 for both gas and condensed phases are presented. The spectra require reassignment of the stretching fundamentals and reveal the previously unknown bending fundamental. The new assignment (solid phase: v1=630.7, v2=296.4, v3=670.8 cm−1) results in a new value for the Cl–O bond stretching force constant, Kr=2.75 mdyn/Å, which is strikingly lower than values previously cited. The bond in chlorine monoxide is proposed as the prototype Cl–O single bond. The low stretching-force constant indicates little ionic character in the Cl–O bond, in disagreement with conclusions based on nuclear quadrupole coupling data.
Study of Collision Effects between the Constituents of a Mixture of Helium and Nitrogen Gases When Excited by a 10-keV Electron Beam
Authors: Sebacher Daniel I.
Published: January 2005

Measurements were made of the effects of collisions between nitrogen and helium excited by a 10-kV electron beam. The interaction between the excited particles was found to give rise to an afterglow of the 3914-Å band of N2+ on the order of 10−7 sec, which was observable at concentrations of helium greater than 75%. A departure from a Boltzmann distribution of rotational energies of the N2+ band was also measured.
Light Scattering in ``Pure'' and Impurity-Doped Potassium Chloride
Authors: Plint C. A. , Sibley W. A.
Published: January 2005

The angular dependence of the light scattering in samples of KCl:Pb and KCl:BO2 is strongly dependent on crystal orientation. The scattering units in these systems are shown to have the form of cylinders, length 50 000 Å, diameter <400 Å, lying parallel to the cubic crystal axes and composed of different scattering centers in the two systems, but both characterized by an anisotropic polarizability ellipsoid which has a specific orientation relative to the cylinder axis. Plausible estimates of the magnitude of the effective polarizabilities of the two types of centers are obtained and compared with theory. Samples of KCl:pure, KCl:Ca, and KCl:Sr did not show any orientation dependence of the scattering. The primary scattering units in KCl:pure are identified as small spherical voids. For KCl:Ca the units are spherical impurity precipitates and voids, radius∼800 Å. In KCl:Sr the scattering is almost entirely caused by spherical precipitates characterized by a randomly oriented anisotropic polarizability tensor having two of its principal values equal. The effects of heat treatment on the scattering by the systems KCl:BO2, KCl:pure, and KCl:Sr are consistent with the identifications of the scattering units and also provide corroboration of previous work on orientation-dependent samples.
Calculation of Electronic Energies in HCO2+, HCO2, and HCO2−
Authors: Kirchhoff W. H. , Farren J. , Linnett J. W.
Published: January 2005

The π-electron energies of the formyloxy cation, radical, and anion (formate ion) have been calculated using several methods. The use of wavefunctions in which the individual electrons were placed in nonpaired spatial orbitals gave a substantial improvement, as judged by comparison with a more accurate configuration-interaction function, over wavefunctions of the molecular orbital and valence bond types. All calculations were then duplicated using electron—electron repulsion integrals which were similar in magnitude to the empirical values of Pariser and Parr but which were derived from the split-p method of Dewar. In this case the use of nonpaired spatial orbitals also gave improvements over the other methods but the advantage was not so great. The implications of these results as well as the technical problems involved in the use of nonpaired spatial orbitals are discussed. Finally, a comparison is made between the results obtained here and those obtained for the isoelectronic allyl system.
Normal Vibrations of the Polymer Molecules of Helical Conformation. V. Isotactic Polypropylene and Its Deuteroderivatives
Authors: Tadokoro Hiroyuki , Kobayashi Masamichi , Ukita Minoru , Yasufuku Katsutoshi , Murahashi Shunsuke , Torii Tatsuo
Published: January 2005

Polarized infrared spectra of isotactic polypropylene (IPP),[Complex chemical formula]were measured in the region from 4000 to 80 cm−1. The normal vibrations of these three polymers were calculated for the infrared- and Raman-active A and E species, by the use of the GF-matrix method with the Urey—Bradley force field. The results show a fairly good agreement between the observed and calculated frequencies. The assignments of the absorption bands were given, and discussions were made on the vibrational modes of the bands characteristic of the isotactic helical structures. A computation program for calculating the characteristic values and vectors of a Hermitian matrix was presented.

From the normal coordinate treatment applied to the threo- and erythro- model of di-isotactic polypropylene-1-d,[Complex chemical formula]it was found that the polymers prepared from trans- and cis-propylene-1-d, CHD, CH–CH3, have threo- and erythro-di-isotactic structures, respectively, suggesting cis-opening mechanism in the coordinated anionic polymerization [α-TiCl3–Al(C2H5)3 catalyst].

The absorption bands characteristic of crystalline IPP are also observed in the 1:1 mole mixture of IPP and IPP-1,1,2-d3, while these bands disappear in the copolymer with the same chemical composition. This fact shows that these characteristic bands arise from the intramolecular interactions in a helical molecule, and the sequence of a certain number of the same monomeric units in the helix is necessary for appearance of these bands. The 1152 and 975 cm−1 bands, which appear also in molten IPP and an ether-soluble fraction of a commercial polypropylene, are ascribed to the chemical structure of head-to-tail sequence of –CH2–CH(CH3)– units.
Ultrasonic Relaxation and Cis—Trans Isomerization in Isopropyl Formate
Authors: Piercy J. E. , Subrahmanyam S. V.
Published: January 2005

The ultrasonic absorption of dilute solutions of isopropyl formate has been measured over the frequency range 0.6 to 45 Mc/sec at temperatures from 30° to 80°C. The frequency dependence of the absorption is that of a single relaxation process. The concentration dependence of the relaxation parameters is consistent with the mechanism being the interconversion of trans and cis isomers by rotation about the carboxyl C–O bond, while the temperature dependence yields a difference in enthalpy and entropy between the isomers of 3.7±0.5 kcal/mole and 1.5±0.6 cal/mole/deg, respectively, and an activation enthalpy of 5.8±0.4 kcal/mole. It is suggested that a large effect in addition to dipolar interaction and steric repulsion is necessary to explain the differences in enthalpy between formate isomers. The ultrasonic absorption in pure isopropyl formate was also measured at 45 Mc/sec over the temperature range −60° to +60°C, and the results have been interpreted in terms of a second relaxation caused by internal rotation about the methoxyl C–O bond.
On the Singlet-Exciton States of Crystalline Anthracene
Authors: Silbey Robert , Jortner Joshua , Rice Stuart A.
Published: January 2005

In this paper we present a detailed analysis of the lower excited states of crystalline anthracene. Starting with zero-order product wavefunctions, the treatment differs from standard formulations in that interactions between molecules are computed directly by the use of π-electron theory, by the inclusion of the effects of extensive configuration mixing, and by the inclusion of long-range interactions out to the convergence limit. It is found that:

(1) The computation of interaction energies cannot be reduced to dipole—dipole terms alone. By the use of π-electron theory it is shown that short-range high-order multipole (greater than dipole) interactions make important contributions to both the diagonal and off-diagonal elements of the energy matrix.

(2) Long-range interactions of the dipole—dipole type are of importance for distances of the order of the wavelength of light. By application of momentum-conservation conditions, it is shown that the long-range dipole—dipole interactions, including the effects of retardation of the potential, are absolutely convergent. Major contributions to the Davydov splitting arise from molecular separations ranging from 50 Å to the convergence limit.

(3) For the case of allowed singlet—singlet transitions, electron-exchange interactions are small relative to other contributions to the interaction energy.

(4) Under the experimental conditions used to date, the Davydov splitting should be independent of crystal thickness.

(5) In anthracene, crystal-field mixing of the p and β molecular states has a large effect on the Davydov splitting. Inclusion of mixing with higher excited π states has little effect on the Davydov splitting, but is required in the calculation of the polarization ratios in the vibronic components of the p band.

(6) Charge-transfer exciton states play only a minor role in altering the properties of singlet exciton states arising from allowed transitions.

(7) The detailed calculations reported herein yield good agreement with the observed Davydov splitting (ΔE) and polarization (P) ratios in anthracene, e.g., for the 1A1g→1B2u band: Vibronic bandΔE(calc.)(cm−1)ΔE(obs.)(cm−1)P(calc.)P(obs.)0–02072303.550–11021452.54.50–254801.93
Radio-Frequency and Microwave Spectra of 6Li127I by the Molecular-Beam Electric-Resonance Method
Authors: Breivogel F. W. , Hebert A. J. , Street K.
Published: January 2005

The radio-frequency and microwave spectra of 6Li127I have been observed by the molecular-beam electric-resonance method of molecular spectroscopy. Spectra of 6Li127I in the first two vibrational states were obtained. From the J=1 radio frequency, Stark spectra values were obtained for the electric dipole moment μ, the iodine nuclear quadrupole interaction eqQI, and the iodine spin-rotation constant cI. The values of these constants are v=0v=1μ (debye)7.4285±0.0017.5120±0.001eqQI (Mc/sec)−198.780 ±0.005−207.453 ±0.010cI (kc/sec)7.7  ±0.47.8  ±0.6.

The observation of J=1→J=0 microwave transitions yielded the following rotational constants: B0=15 304.895±0.005 Mc/sec,B1=15 153.316±0.009 Mc/sec.
Molecular Magnetic Moments and Susceptibility in Formaldehyde
Authors: Flygare W. H.
Published: January 2005

High-resolution microwave spectroscopy has been used to measure the molecular Zeeman effect in formaldehyde where both ΔM = 0 and ΔM = ±1 transitions were observed. The magnitudes and signs of the diagonal elements of the g tensor were determined.

The results for OCH2 are | gbb—gcc | = 0.08±0.03, gaa = −2.935±0.03, gbb = −0.17±0.05, and gcc = −0.11±0.05. These results combined with the value of the bulk susceptibility yield the following value depending on the ground-state wavefunction for OCH2: 〈ψ0 | Σiri2 |ψ0〉 = 14.61×10−16 cm2, where the sum is over all electrons.

The average value of the diamagnetic susceptibility in OCH2 is χd = −41.3×10−6. The average value of the paramagnetic susceptibility is χp = 40.8×10−6. The anisotropy in the paramagnetic susceptibility along the O–C bond is χ⊥p—χ∥p = 5.6×10−6 where χ⊥p is perpendicular to the CH2 plane.
Behavior of Thirteen Charge-Transfer Complexes at High Pressures
Authors: Bentley W. H. , Drickamer H. G.
Published: January 2005

The effect of pressure to several hundred kilobars has been measured on the properties of 13 complexes containing aromatic molecules. These complexes are classified in four groups: those containing tetracyanoethylene (TCNE), those containing iodine, those involving p-phenylenediamine, and halogenated p-benzoquinones, and those involving the halogenated p-benzoquinones and other materials.

In all cases the resistance decreased rapidly with increasing pressure at low pressures. A number of complexes exhibited minima in resistance at pressures from 60 to 200 kbar and an irreversible rise at higher pressures. The nature of the irreversible process could in several cases be postulated from difference in the visible and infrared spectra between the transformed and untransformed complexes.