bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear Relaxation Processes in Systems of Two Spins
Authors: Mackor E. L. , Maclean C. 
Published: January 2005

Nuclear relaxation in a system of molecules with two nonidentical spins (S and I) may originate from intra- or intermolecular interactions between like and unlike spins. An experiment is described which, in combination with the nuclear Overhauser effect, allows the determination of the contributions from the various interactions.
The spins (S=½, I=½) are supposed to be coupled by a small scalar interaction and four longitudinal magnetizations S+, S—, I+, I—, can be measured. The decay of the total magnetizations (S++S—) or (I++I—) was discussed by Solomon and Bloembergen.
The decay of the difference of the magnetizations (S+—S—) or (I+—I—) is a useful parameter as is shown in this paper. The relaxation time of (S+—S—) and (I+—I—) is related to the question whether the interactions are intra- or intermolecular. We have derived the appropriate equations for the time dependence of the difference magnetizations; the relaxation rate of the difference magnetization is larger for intermolecular dipolar interactions than in the intramolecular case when compared with the relaxation of the sum magnetizations.
Experiments on CHFCl2 at −142°, −115°, and at +20°C are reported. At temperatures just above the melting point both hydrogen and fluorine spins relax mainly by interactions between unlike spins; the contributions of intramolecular interactions are predominant. At 20°C it appears that the fluorine spin is relaxed by spin rotation and hydrogen by intermolecular dipole interactions.
Raman Spectral Studies of Alkaline Solutions of Germanium Dioxide
Authors: Walrafen G. E. 
Published: January 2005

Raman frequencies, polarizations, and infrared frequencies of nearly saturated aqueous solutions of KOH containing various amounts of GeO2 (0.5 to 6.0 mole liter−1) have been obtained at 25°C, and relative integrated Raman intensities of bands of the alkaline solutions at 529, 667, and 765 cm−1 were also obtained for various stoichiometric GeO2 molarities, CGeO2, under conditions of nearly constant, and of varying stoichiometric KOH molarity, CKOH.
In the concentration ranges 0&lt;CGeO2&lt;6M, and 10.53&lt;CKOH&lt;14.87M, the relative integrated Raman intensity of the 765-cm−1 band, I765, was observed to be nearly proportional to CGeO2, which suggests that much of the germanium is present in one form, e.g., as H2GeO42—. However, marked downward deviations from proportionality observed for another intensity of H2GeO42—, I667, evident in the range ∼2&lt;CGeO2&lt;6M, indicate that appreciable concentrations of a second species, e.g., Ge2O52—, must contribute to the 765-cm−1 band intensity to produce the observed near proportionality. The species Ge2O52— is also thought to give rise to another band at 529 cm−1, the intensity of which increases from very low to measurable values in the range 0&lt;CGeO2&lt;6M, and the presence of more than one germanium-containing species is given additional support by polarization data.
Raman and infrared frequencies of solid Na2GeO3 and of vitreous GeO2, and infrared frequencies of hexagonal GeO2, also obtained in this work, are included, as are viscosity and electrical conductivity data for alkaline solutions of germanium dioxide.
Line-Breadth Study of the 1.64-mm Absorption in Water Vapor
Authors: Rusk James R. 
Published: January 2005

The 2+2→3−2 rotational transition in water vapor has been carefully studied by using both a simple video and a double modulation millimeter wave spectrometer. The line center remeasured is ν0 = 183 310.12±0.10 Mc/sec. Self-broadening and foreign-gas broadening were investigated over the pressure range of 5 to 400 μ of Hg with the following results: Perturbing gasΔν/p (Mc/sec·mm)H2O19.06CO26.09N23.76O22.72Ar1.97.
These results, obtained by the double modulation spectrometer, have been compared with other line broadening studies, and for the first time linewidth calculations on asymmetric molecules appear to be valid.
Direct and Inert-Gas-Sensitized Radiolysis and Photolysis of Methane in the Solid Phase
Authors: Ausloos P. , Rebbert R. E. , Lias Sharon G. 
Published: January 2005

The photolysis of CH4–CD4 mixtures has been briefly investigated at 20.4°K using the xenon and krypton resonance lines. From the isotopic composition of the hydrogen and ethane fractions, it could be derived that, in the solid phase, methylene and methyl radicals are produced. The methylene radicals, which are formed by the process CH4*→CH2+H2, insert into methane to form ethane.
In the argon-sensitized radiolysis at 20.4° and 77°K, the hydrogen-molecule elimination process predominates, indicating that neutral excited-methane molecules are formed nearly exclusively. In the xenon-sensitized radiolysis, however, mainly hydrogen atoms and methyl radicals are observed. In all inert gas-sensitized radiolyses, there is a gradual decrease in the efficiency of the energy transfer with increasing dilution.
In the direct radiolysis, hydrogen atoms play a more important role than in the photolysis at 1236 Å. Radiolysis of CD4−C2H4 (1:0.01) mixtures indicated that, at 77°K, hydrogen atoms react with ethylene and propylene to form higher saturated hydrocarbons while, at 20.4°K, hydrogen atoms disappear mainly by recombination with other free radicals. From the isotopic composition of the ethylene fraction formed in the radiolysis of Ar–CH4–CD4 mixtures, it is surmised that a fraction of the methylene recombines to form ethylene.
New Lattice Model for the Statistical Mechanics of Quantum Fluids. I. Liquid Hydrogen and Its Isotopes
Authors: Benson Sidney W. , Marchi Raymond P. 
Published: January 2005

A lattice-cell model for quantum fluids is proposed in which the thermal energy of the lattice is represented by the Debye equation for crystalline solids. The maximum Debye frequency vD is taken equal to the simulated frequency for a single hard-sphere molecule moving in an infinitely deep, cubic potential well. Lennard-Jones parameters from viscosity measurements on H2 are used to describe the van der Waals lattice energy. The only parameter in the theory is the equivalent hard-sphere diameter. This is determined from the molar volume of liquid H2 and is 2.79 Å, very close to the Lennard-Jones value of σ, 2.92 Å. Calculated values of the molar volumes of D2, T2, and the intermediate HD are in good agreement with observed values, as are the heats of vaporization and specific heats. Calculated values of the coefficients of compressibility and thermal expansion are too low, but the value of internal pressure (δP/δT)v is in excellent agreement with observed values.
The most interesting feature of the model is that it yields, for the first time, a lower free energy for the body-centered lattice than for the face-centered lattice. This reflects the importance of the increased free volume and hence lower zero point energy for the less compact lattices. The actual differences in free energy for different packings are small compared to RT near the boiling points and this suggests very large fluctuation in packing in the liquids. The relation to melting is discussed briefly.
Calculations show that the isotopic properties are very sensitive to the form of the repulsive potential.
Auto- and Cross-Correlation Functions Used as Tools for Information Retrieval in Electron Diffraction Structure Studies
Authors: Traetteberg M. , Bonham R. A. 
Published: January 2005

Three radial distribution functions [f(r)], the power spectrum, the diagonal power spectrum, and the sharpened radial distribution function have been introduced, and it is shown that these functions might be useful tools in extracting molecular information from a gas electron diffraction experiment. The two kinds of power spectra are based on short-interval auto- and cross-correlation functions of the molecular intensity function, while the sharpened radial distribution function is defined as the Fourier sine transform of the product of the molecular intensity function and the antidamping function exp[—α(smax—s)]. The similarity between the power spectrum and the sharpened radial distribution function has been pointed out.
By examples based on experimental data and numerical calculations based on theoretical data it is shown that the modified f(r) functions introduced here give better resolution between neighboring peaks than the radial distribution function that is normally applied in electron diffraction structure studies.
The errors introduced in rij values determined from the various f(r) functions, due to additive random errors in the molecular intensity function, have been studied by numerical analysis, and it has been shown that accurate structural parameters can be extracted from sharpened f(r) functions.
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.
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.
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.
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.
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.
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.
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.
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.