bluuebunny/crossref_metadata_2025 huggingface dataset:
ESR of X-Irradiated Silver Nitrate
Authors: Mosley W. C. , Moulton W. G.
Published: January 2005

Four paramagnetic species have been detected by ESR in single crystals of AgNO3 x irradiated at 77°K. The principal values and corresponding principal axes of the g tensors and hyperfine tensors have been determined. An eight-line spectrum, four doublets, is due to Ag++. A 24-line spectrum, four sextets, has been assigned to a species believed to be AgNO3−. A spectrum of four triplets characteristic of stationary NO2 molecules was observed in previously irradiated crystals and crystals doped with AgNO2. A spectrum consisting of two weak singlets is due to an unidentified species. This is the only species stable at room temperature. Discussions of the orientations, configurations, mechanisms for production, and annealing characteristics of the several species are given.
Spin States of Trivalent Chromium with Tetragonal Symmetry in MgO
Authors: Auzins Peteris V. , Wertz John E.
Published: January 2005

Spin transitions between nonadjacent energy levels of Cr3+ in tetragonal symmetry in MgO become allowed by the mixing of states which occurs when the applied magnetic field is not along the symmetry axis. The tetragonal electric field arises from association with a next-nearest-neighbor (nnn) cation vacancy. When the defect axis is perpendicular to the applied field, energy level and matrix element expressions for the −32→32 transition are closely related to those for the normally allowed transitions. Two other transitions between alternate levels (−32→12 and −12→32) become allowed for parallel microwave and static fields. The ESR lines corresponding to these transitions have been observed.
Crystal Vibrations and Intermolecular Forces of Polymethylene Crystals
Authors: Tasumi M. , Shimanouchi T.
Published: January 2005

Normal frequencies of crystalline polymethylene have been calculated for various phase differences along the c axis of the crystal. Intermolecular hydrogen—hydrogen force constants have been evaluated from the splitting of the spectroscopically active modes. The results of the calculations explain almost satisfactorily the splitting of the progression bands in the infrared spectra of long-chain n-paraffins as well as one lattice vibration band in the far-infrared spectrum of polyethylene.
On the Theory of Shifts and Broadening of Electronic Spectra of Polar Solutes in Polar Media
Authors: Marcus R. A.
Published: January 2005

When a polar-solute molecule undergoes an electronic transition and forms a state of different polarity, the Franck—Condon principle shows that the new system is first formed in a nonequilibrium thermodynamic state. An expression for the spectral shift and broadening by a series of solvents of differing polarity is derived in the present paper in terms of thermodynamic properties of certain equilibrium distribution systems. For this purpose use is made of a recent particle description of nonequilibrium and equilibrium polar media, which emphasizes functional dependence and avoids, thereby, the usual more specific assumptions. A relation between the broadening and the shift is then deduced under certain conditions. Expressions are also derived for the effect of pressure and temperature on the shift, in terms of the polar contribution to the volume and entropy of solvation, respectively, and for the influence of applied electrical fields. An expression is obtained for the solvent-reversal shift of Brooker in terms of the polarizability difference of the initial and final states of the solute. Introduction of more specific assumptions is then made for purposes of comparison with earlier works, which constitute special cases of the present one, and for estimation of dipole moments and polarizabilities of excited states from spectral and electrical shifts.
Optical Activity of Anisotropic Solutions. I
Authors: Gō Nobuhiro
Published: January 2005

General theory of optical rotation is developed for transparent solutions in which the orientational distribution of solute molecules is given arbitrary. The theory of Stephen and Hameka is generalized to derive a formula giving the rotation angle in terms of the orientational distribution function and matrix elements of the solute molecule. The rotation angle is a sum of molecular rotations (contribution from individual molecules), which depend on the orientation of the molecules relative to the incident light. The molecular rotation is given as a series, which converges very rapidly when the characteristic length of the molecule is small compared with the wavelength of the incident light. If we approximate the series by the first two terms, which is valid for most cases, the optical rotation α is given by the equation, α=A+ ∑ i=15biBi.Here, anisotropy parameters of the solution bi are defined by bi=18π2 ∫ sinθdθdφdψf(θ,φ,ψ)bi(θ,φ,ψ),  (i=1,2,···,5),where f(θ, φ, ψ) is the orientational distribution function of optically active solute molecules and bi (θ, φ, ψ) are certain functions of Eulerian angle. The value of the anisotropy parameters bi and the expressions Bi are dependent on the choice of the body fixed coordinate system and behave as five-dimensional irreducible tensors of Rank 3 for rotations of the system. When the solution is isotropic, the anisotropy parameters vanish and the formula reduces to α=A, which is identical with the formula derived by Rosenfeld. In cases of rotationally symmetric molecules the number of the anisotropy parameters reduces to one.
Polarized Absorption and Emission in an Octacoordinate Chelate of Eu3+
Authors: Blanc Joseph , Ross Daniel L.
Published: January 2005

Polarized absorption in the 5D2←7F0 transition and emission in the 5D0→7F2 transition of the Eu3+ ion have been obtained in monoclinic single crystals of the tetrahexylammonium salt of tetrakis diphenyl-propanedionoeuropium (III). Both sets of transitions consist of three lines, two polarizing strongly perpendicular to the crystallographic c axis, the third polarizing parallel to this axis. Assuming the propriety of electric-dipole selection rules, these results are consistent with S4 symmetry for the chelate anion.
Pyrolysis of Ethyl Iodide by the Toluene-Carrier Flow Technique
Authors: Yang Jae-Hyun , Conway D. C.
Published: January 2005

The pyrolysis of tagged ethyl iodide has been studied in the presence of the radical scavenger toluene in a flow system. The rate constants for the formation of C2H4(kD), C2H6(kS), and bibenzyl have been determined as a function of the contact time, toluene pressure (2–18 mm Hg), and C2H5I pressure PE(0.6–40×10−3 mm Hg) at 774°K. It is concluded that kD≈k1 and kS≈k2 at low kiPE, where C2H5I→ lim k1C2H4+HI,C2H5I→ lim k2C2H5+I.The first reaction appears to be first order at 14 mm Hg of toluene pressure with a high-pressure Arrhenius rate constant k1∞ of 1.27×1014 exp (−52.8×103/RT) sec−1. The second reaction is not first order at any pressure, but by extrapolation k2∞ was estimated to be 4.5×1013 exp (−50×103/RT) sec−1.

The RRKM theory was used to fit the pressure dependence of k1 and k2 in the approximation that the same degrees of freedom are active in the energized molecule A* for both reactions. The disagreement between theory and experiment could be the result of fewer of the rotational degrees of freedom of A* being active in the second reaction than in the first.
Pressure—Volume—Temperature Relations in Solid Parahydrogen
Authors: Cook Gerhard A. , Dwyer Robert F. , Berwaldt Oren E. , Nevins Hugh E.
Published: January 2005

Experimental data are presented for the molar volume of solid parahydrogen at five different temperatures over the range 11.49° to 19.97°K and at pressures from 0 to 350 atm. In making the density measurements, it was found that there is a fairly well-defined region of temperature and pressure in which solid hydrogen is viscoelastic. At higher pressures the solid is rather hard and rigid.

A diagram is included which gives an idea of the PVT relations for solid parahydrogen up to a pressure of about 400 atm. The accuracy with which the points on this diagram are known ranges from ±0.2% along the melting line to ±5% at points far from the melting line. A striking feature is the shape of the isobars in the neighborhood of the melting line; at pressures above about 150 atm, each isobar passes through a maximum at a molar volume which is greater than the corresponding molar volume along the melting line. It appears that the thermal coefficient of expansion of solid parahydrogen is negative in a narrow range of temperature and pressure.
Investigations of Hexanol-1 Multimers and Complexes by the Method of Dielectric Polarization in Weak and Strong Electric Fields
Authors: Mal/ecki J.
Published: January 2005

Results on dielectric polarization and its variations in strong electric fields are presented for solutions of hexanol-1 in hexane, benzene, 1,4-dioxane, and triethylamine. A method for calculating the dipole moments of multimers and complexes on the basis of experimental results is proposed. Also, the concentrations of molecular clusters versus that of the investigated compound in solution and their dipole moments in an ionized (when proton shifted) form of the hydrogen bridge are given.

The determined dipole moments of complexes are used for establishing the arrangement of the hydrogen-bond chain. The concentrations of cyclic structures of multimers and the changes in free energy involved by a transition from cyclic to open structure are estimated.
New Model for Classical Fluids. I
Authors: Wertheim M. S.
Published: January 2005

A simple new model for classical fluids is presented. Separate guesses are made at the form of the excess entropy and the excess internal energy. The two terms are made thermodynamically consistent by a minimization of the excess Helmholtz free energy. The two boundary conditions of yielding the exact equation of state of hard spheres and yielding an exact second virial coefficient for an arbitrary potential then completely determine the model, which does not contain any adjustable parameters. The model yields a critical point and van der Waals loops at subcritical temperatures for any potential containing an attractive region. Agreement with experimental data for argon and hydrogen is surprisingly good. Some predictions of this model for a Lennard-Jones 6–12 potential are compared with real gases.
Vibration—Vibration Energy Exchange between Carbon Monoxide and Methane
Authors: Millikan Roger C.
Published: January 2005

The quenching of the vibrational fluorescence of CO by CH4 has been measured between 303° and 363°K. The quenching arises from the vibration—vibration exchange: CO*+CH4=CO+CH4* where all molecules are in ground electronic states. The average number of collisions between CO* and CH4 required for a V–V transfer to occur varies from 33 000 at 303°K to 24 000 at 363°K.
Total Cross Sections for Ionization and Attachment in Gases by Electron Impact. I. Positive Ionization
Authors: Rapp Donald , Englander-Golden Paula
Published: January 2005

The total ionization cross sections of He, Ne, Ar, Kr, Xe, H2, D2, N2, O2, CO, NO, CO2, N2O, and CH4 have been measured from threshold to 1000 eV in a total ionization tube. More limited measurements were performed in C2H4 and SF6. Great care was taken to assure complete collection of electron and ion currents, and the absence of spurious instrumental errors. A new method was devised for obtaining absolute cross sections of gases relative to H2, and a McLeod gauge was used to obtain the absolute cross section in H2. The cross sections in NO and O2 could not be obtained by this method, and an approximate correction to direct McLeod-gauge readings was used for these gases. It is believed that the results are as accurate as is possible with the present method. It is difficult to explain the differences found between cross sections measured by various investigators. McLeod-gauge errors appear to account for most of the difference in absolute magnitude.
Luminescence from Transition-Metal Complexes: Tris(2,2′-bipyridine)- and Tris(1,10-phenanthroline)Ruthenium(II)
Authors: Crosby G. A. , Perkins W. G. , Klassen D. M.
Published: January 2005

Absorption and emission spectra and mean lifetimes (τm) of the luminescence of tris(2,2′-bipyridine)- and tris(1,10-phenanthroline)ruthenium(II) are reported. For the 2,2′-bipyridine complex, two weak absorption bands occurring at 15 050 and 18 550 cm−1 are assigned, respectively, to the 1A1→3T1 and 1A1→1T1 transitions of d—d type, and the intense luminescence with origin at 17 250 cm−1 (τm = 5.92 μsec) is assigned to 1T1→1A1 fluorescence. For the 1,10-phenanthroline complex, no intra-d transitions were observed in absorption, but the bright luminescence with origin at 17 700 cm−1 (τm = 9.93 μsec) was assigned to 1T1→1A1 fluorescence in analogy with the first compound. The energy levels are analyzed on the basis of an octahedral model, and empirical values for the Racah B and C parameters for Ru II and the crystal-field parameter Δ are evaluated. Possible uses of the compounds for laser applications are suggested.
Calculation of Matrix Elements for One-Dimensional Quantum-Mechanical Problems and the Application to Anharmonic Oscillators
Authors: Harris David O. , Engerholm Gail G. , Gwinn William D.
Published: January 2005

A simple method using the techniques of transformation theory for the generation of the matrix elements of unusual potential functions for one-dimensional quantum-mechanical problems is described. It is applicable both to functions which exist as a set of points, for example, a curve or table, as well as to those in explicit form. Some representative calculations have been made for anharmonic oscillators.
EPR Spectroscopic Study of Radicals Formed from Aliphatic Carboxylic Esters and Related Compounds
Authors: Smith P. , Pearson J. T. , Wood P. B. , Smith T. C.
Published: January 2005

A long-range coupling across the alkoxycarbonyl group of about 1.4–1.5 G has been observed in the EPR spectra of radicals formed in the hydroxyl-radical-initiated homopolymerization of methyl acrylate, ethyl acrylate, and methyl methacrylate within an aqueous flow system at 25°±1°C. This coupling has been further investigated by way of a comprehensive EPR study of a series of simpler, related radicals prepared under similar conditions from methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, and methyl isobutyrate by hydrogen-atom abstraction with hydroxyl radicals. For ester radicals other than those produced from the formates there was a long-range coupling of 1.4–1.5 G with protons δ to the unsaturated carbon atom when this unsaturated carbon atom was adjacent to the oxycarbonyl group, i.e., for radicals with the following functional structures, Ċ–CO–O–C and C–CO–O–Ċ. The two formates yielded only the radicals HCOOĊH2 and HCOOĊHCH3. These displayed a γ coupling with the formyl proton of 2.4–2.5 G. All these results are shown to be compatible with a simple model based on a delocalized π-bond system. Comparison of the observed proton coupling constants with the available data for similar unsubstituted aliphatic radicals suggests that the value of Qα in the McConnell equation aα=Qαρ is significantly lower in a conjugated radical than in a similar nonconjugated radical. In support of the data from this study of hydroxyl-radical attack on esters, the substrates formic, acetic, propionic, n-butyric, and isobutyric acids and methanol, ethanol, and acetone have been examined in a like fashion. Many of the esters and acids investigated underwent hydrogen-atom abstraction at more than one site. For those substrates, it was possible to estimate qualitatively the selectivity of hydroxyl-radical attack from the relative intensities of the EPR absorptions of the different reaction products. The results so obtained are reckoned to generally support the expected electrophilic character of the hydroxyl radical in these reactions.
Melting Curves of the Rubidium Halides at High Pressures
Authors: Pistorius Carl W. F. T.
Published: January 2005

The melting curves of the rubidium halides have been determined to 30–40 kbar. The present curve for RbCl is in good agreement with Clark's curve to 12 kbar. The pressures of the triple points between the low- and high-pressure solid phases and liquid for RbCl, RbBr, and RbI agree well with the values to be expected by extrapolation of earlier work at lower temperatures. The triple point on the melting curve of RbF is located near 32 kbar.
Van der Waals Forces in Solids
Authors: Mahan G. D.
Published: January 2005

The van der Waals interaction energy is calculated for a molecular solid of point dipoles. It is shown that the interaction energy may be expressed in a closed form considering either the Coulomb or the full retarded interaction.
Nuclear Magnetic Resonance Studies of Solvent Effects on the Hindered Internal Rotation in N,N-Disubstituted Amides. II. Higher Alkyl Amides
Authors: Whittaker A. Greenville , Siegel Seymour
Published: January 2005

The temperature dependence of the chemical shifts due to hindered internal rotation was measured for diethylformamide, diethylacetamide, diisopropylformamide, diisopropylacetamide, and for solutions of these molecules in various solvents. In all cases, the chemical shifts showed rather unusual behavior. Conventional methods, coupled with certain approximations, were used to calculate ``activation energies'' as estimates for the ``rotational barrier'' to the internal rotation about the N–CO bond. These values were found to lie in the range of 5 to 26 kcal/mole. However, it is difficult to determine the real significance of these numbers; indeed, the behavior of the chemical shifts were such that no underlying concepts could be developed that would correlate the observed results except for the conclusion that the solvent plays a dominant role in the relationship between chemical shift and temperature.
Concentration Dependence of the Thermal-Diffusion Factor for 3He–4He and H2—D2
Authors: Paul R. , Howard A. J. , Watson W. W.
Published: January 2005

The thermal-diffusion factors of 3He–4He and H2—D2 systems have been determined with high precision at several different compositions and at a fixed mean temperature, T̄ = 160°K, using a four-tube swing separator for 3He–4He mixtures, and a simple two-bulb apparatus in the case of H2—D2. The results indicate that the thermal-diffusion factor increases in magnitude with the increasing concentrations of the lighter component, as anticipated from theory. Detailed theoretical calculations on the Chapman—Cowling first approximation and the Kihara first and second approximations have been carried out, and comparisons made with the experimental results in both the cases. Good agreement between the Chapman—Cowling first approximation and the experimental results has been obtained, though Kihara approximations also could be fitted within the experimental uncertainty of the data in both the systems studied.
Magnetic Transitions in Ni[(NH2)2CS]6Br2
Authors: Forstat H. , Love N. D. , McElearney J.
Published: January 2005

Heat-capacity measurements have been made on single crystals of Ni[(NH2)2CS]6Br2 in the temperature range 1.3°—17.4°K. Two λ-type anomalies were observed at 1.96° and 2.25°K and are associated with paramagnetic—antiferromagnetic transitions. The total entropy change associated with these transitions is 2.24 cal/mol deg and differs by approximately 2% from the expected value of R log(2S+1), where S=1 for the Ni++ ion. Approximately 78% of this total entropy change occurs above 2.25°K. A calculation based on the simple molecular field theory provided an estimate of the exchange integral as well as the temperature dependence of the sublattice magnetization. These are compared with the results from the magnetic susceptibility and nuclear magnetic resonance.
Photoconductivity of α-Methylnaphthalene Alone and with an Incorporated Solute
Authors: Kallmann H. P. , Krasnansky V. J. , Orenstein A.
Published: January 2005

Exposure of α-methylnaphthalene to strongly absorbed uv light and externally applied voltage produced photocurrent in the range of 10−9 to 10−7 A/cm2; their magnitude depended on the polarity of the illuminated electrode. The illumination through the positive electrode gave a photocurrent 15 times greater than when the negative electrode was illuminated. The mobilities of the positive and negative carriers were determined to be 1.2×10−4 and 5×10−5 cm2/V·sec, respectively. The former value is of the same order of magnitude as the theoretical value calculated for a positively charged α-methylnaphthalene ion. The temperature dependence of the mobility of the positive carrier indicated that the carrier may be either an ion or a hole with a long hopping time. Current—voltage measurements show that saturation is not reached at the highest field strength employed, 40 000 V/cm, and most likely would not be reached below fields of 106 V/cm. On this basis a theoretical efficiency of 1% for charge production was estimated. A non-Ohmic behavior of the photocurrent was observed, which suggested the presence of either a potential well at the electrode or the influence of space charge effects. The incorporation of a solute, 9,10-diphenylanthracene, reduced the current to 25% of that for the solvent alone, indicating extensive energy transfer to the solute and not simply to differences in mobility. The mechanism of charge production was interpreted either as an exciton interacting with the electrode to produce holes or as ionization of the solvent near the electrode with differences in recombination rates of the charges with the electrode.
Pentacoordinated Molecules. VI. The Electric-Dipole Moment of PCl3F2 and PCl2F3 in the Gaseous State
Authors: Holmes Robert R. , Carter Richard P.
Published: January 2005

From a study of the temperature variation of the dielectric constant over the range from −30° to +19°, a value of 0.68±0.02 D was obtained for the vapor-state electric-dipole moment of PCl2F3 and 23.4±0.5 cc for the induced polarization. A similar study on PCl3F2 showed no detectable change in the molar polarization over the temperature interval extending from −13° to +30°. A zero dipole moment is assigned in agreement with previous structural information on this molecule. The induced polarization is 32.0±0.2 cc. The reliability of the measurements were determined by studying gaseous ammonia and dimethyl ether over the same temperature region. The high dipole moment of PCl2F3 compared to the gas-state value observed for PCl4F (0.21 D) is attributed primarily to differences in bonding between equatorial and axial positions of a trigonal biypramid with distortion acting as a secondary factor.
Nitrogen Isotope Effects in the Decomposition of Diazonium Salts
Authors: Brown L. L. , Drury J. S.
Published: January 2005

The nitrogen isotope effects produced upon fractionally decomposing C6H5NNCl, C6H5NNBF4, m-ClC6H4NNBF4, o-, m-, and p-CH3C6H4NNBF4 were measured as a function of temperature. Between 5° and 70°C the data are well represented by the least-squares equation, log(k14/k15)=6.949/T−0.002528. The experimental results agree well with those predicted from spectroscopic data. The data are consistent with the model in which decomposition occurs through the rupture of a single C–N bond. The observed isotope effect is insensitive to the nature and position of substituents on the aromatic ring and to the anion of the salt. The difference in the activation energy for the decomposition of the 14N- and 15N-labeled diazonium salts is 32 cal mole−1·deg−1.
Thermal Decomposition of Acetylene in Shock Waves
Authors: Gay I. D. , Kistiakowsky G. B. , Michael J. V. , Niki H.
Published: January 2005

Using a shock tube and an improved T.O.F. mass spectrometer displaying spectra every 20 μsec, the pyrolysis of acetylene was shown to proceed through the sequence C2H2→C4H3→C4H2→C6H2→C8H2→···in the temperature range 1600°—2400°K. All these intermediates reach steady-state concentrations, that of the radical C4H3 being as large as that of diacetylene under favorable conditions. The primary bimolecular reaction of acetylene in which the radical C4H3 is formed must also yield hydrogen atoms. These catalyze an isotopic exchange in mixtures of C2H2+C2D2 that is about three orders of magnitude faster than the formation of C4H2. The initial yield of acetylene-d1 is given by the expression [C2HD]t=k[C2H2+C2D2]03t2,which is consistent with the proposed partial reaction mechanism. The mechanism of conversion of C4H3 into C4H2, etc., is uncertain but undoubtedly involves free radicals.
Effect of Substituents on the ESR Hyperfine Splittings in Copper Acetylacetonates
Authors: Kuska Henry A. , Rogers Max T.
Published: January 2005

The ESR hyperfine splittings and g values for several substituted copper acetylacetonates have been measured in chloroform solution, and the values for copper acetylacetonate have been determined in various solvents. The hyperfine splittings are found to decrease with the substitution of more electronegative groups on the ligand and also decrease for a given ligand on going to a more basic solvent. The results have been discussed in terms of the electronic structures of the complexes.
Kinetic Theory of Loaded Spheres. II
Authors: Sandler Stanley I. , Dahler John S.
Published: January 2005

The Chapman—Enskog method of solution is applied to the Boltzmann equation for a dilute gas of loaded spheres. It is shown that the anisotropy of the molecular spin distribution has almost no effect upon the numerical values for the thermal conductivity and viscosity.
ESR Study of Excited Rare-Gas-Initiated Reactions of Polystyrene and Polymethylmethacrylate
Authors: Ingalls R. B. , Young W. A.
Published: January 2005

ESR spectra have been obtained of free radicals produced in freeze-dried polymer ``fluffs'' by reaction with excited rare-gas atoms produced in an electrodeless discharge. These excited atoms survive numerous collisions with the quartz walls of the reaction cell but react very rapidly with the polymers. Polystyrene appears to protect polymethylmethacrylate from attack by the excited rare gases when it is coprecipitated with the latter in the ratio of 1:9.
Raman Spectrum of Molten Zinc Chloride
Authors: Irish D. E. , Young T. F.
Published: January 2005

Band contours and band intensities in the Raman spectrum of molten zinc chloride have been examined. Bands not previously detected by photographic techniques have been detected photoelectrically. Their intensities are temperature sensitive. The intensity of the band at 230 cm−1 decreases with the addition of water. A description of the constitution of the melt is proposed.
Detailed Balance in Optical Transitions in Molecules and Solids
Authors: Fowler W. Beall , Dexter D. L.
Published: January 2005

Recent theoretical and experimental work has shown that the simplest form of the Einstein equation relating induced absorption and spontaneous emission probabilities (characterized by Σ and τ−1) is not generally valid for impurities or color centers in solids, liquids, or molecules. Separate computations of these probabilities in systems exhibiting sizeable Stokes's shifts resolve some of the problems; they also disclose the difficulties involved in obtaining any connection between Σ and τ. Here we consider how the transition probabilities between a pair of electronic-vibrational states are related. Observable quantities, i.e., integrated absorption cross section and the radiative decay time, involve sums and averages over the vibrational states, and no definite theoretical information relates these quantities. However, there is a simple connection between induced and spontaneous emission probabilities. New experiments which could yield information about the rate of lattice relaxation are suggested from this point of view.
Theory of Selective Uptake of Ions of Different Size by Polyelectrolyte Gels—Experimental Results with Potassium and Quaternary Ammonium Ions and Methacrylic Acid Resins
Authors: Miller Irving F. , Bernstein Fabian , Gregor Harry P.
Published: January 2005

A model has been developed to predict the selectivity of polyion gels for one counterion over another of a different size. The model, essentially an extension of the Kagawa—Gregor model is based on purely electrostatic interactions between the gel and the counterions and takes into account their differing distances of closest approach. This model was tested against experimental data involving cross-linked polymethacrylic acid with Li+, Me4N+, and Et4N+ ions exchanging for K+; it was found to predict these selectivities to a good degree of accuracy, particularly with the unhydrated quaternary ammonium ions. The model correctly predicts the variation of selectivity with counterion size ratio and also correctly predicts the variation of selectivity with counterion concentration ratio. Discrepancies between theory and experiment attributable to pressure—volume effects were also evaluated and remaining differences were ascribed to adsorption phenomena.
Measurements of the Molecular Absorption Cross Section and the Photoionization of Sodium Vapor between 1600 and 3700 Å
Authors: Hudson R. D.
Published: January 2005

The absorption cross section of molecular sodium has been measured, using photoelectric techniques, from 1600 to 3700 Å. The bandwidth of the monochromator was 0.75 Å and values of the cross section were obtained at 2 Å or smaller intervals. The photoionization of sodium vapor was also investigated and the ionization potential of the molecule was found to be 4.90±0.01 eV. Ion peaks were observed at energies corresponding to the 3s1S0—np2P0 series lines. A discussion of this phenomenon is given with reference to results obtained by other workers for the alkali metals. The conclusion reached is that the ground states of the molecular ions are more stable than the corresponding neutral ground molecular states.
Mutual Interaction and Ionization of Excitons in Aromatic Molecular Crystals
Authors: Choi Sang-il
Published: January 2005

A simple formula for the rate of ionization of molecular excitons as a result of their mutual interaction in aromatic crystals is derived. It is shown that, under certain assumptions, the rate of ionization for vibronic as well as electronic excitons can be evaluated from the transition moments of electronic transitions of molecules and the geometric parameters of the crystal.
NMR Second Moment of Solid Cyclododecane
Authors: Arndt R.
Published: January 2005

The NMR second moment for the rigid lattice of cyclododecane has been measured and is compared with theoretical values calculated for models which have been derived from an x-ray analysis. The NMR data complement the other data such that the conformation of the molecule could be determined unambiguously.
Reinterpretation of the EPR Spectrum of N,N′-Tetramethylbenzidine Cation
Authors: Fritsch John M. , Adams Ralph N.
Published: January 2005

The EPR spectrum of N,N,N′,N′-tetramethylbenzidine monocation has been completely reanalyzed and has been found to have the following hyperfine coupling constants in acetonitrile: aN=4.86 G, aH methyl=4.74 G, aH3,5,3′,5′=1.63 G, and aH2,6,2′,6′=0.79 G.
Isotopic Thermal-Diffusion Factor for Xenon
Authors: Paul R. , Howard A. J. , Watson W. W.
Published: January 2005

The isotopic thermal-diffusion factor α0 for xenon has been determined over a mean temperature range of 245° to 543°K. An artificial mixture of xenon isotopes containing approximately 18% 129Xe and 15% 136Xe was subjected to thermal diffusion in a 10-tube swing separator; the isotopic thermal-diffusion factor was obtained from the change of concentrations of these two isotopes only. A best-fitting procedure yields potential parameters α=16 and ε/k=257°K for the exponential-six interaction-potential model, whereas the Lennard-Jones (12:6) model fails to reproduce the experimental results. This exp-6 potential was then used to calculate the values of diffusion, viscosity, thermal conductivity, and second virial coefficient, and a reasonably good agreement was obtained with rm=4.41 Å.

An intercomparison of the observed and the theoretically calculated isotopic thermal-diffusion factors for all the inert gases from T*=0.6 to 60 is also presented.
Correlation Functions in Nuclear Relaxation. I. Analysis of Random Motions from Field Dependence of Relaxation Times
Authors: Deutch J. M. , Waugh J. S.
Published: January 2005

The contributions to T1 in a fluid arising from spin—rotational interaction and chemical-shielding anisotropy are discussed in terms of their simultaneous use to analyze the detailed nature of random rotations without the need of a microscopic theory. This possibility often exists because of the involvement of different correlation functions of the lattice variables and the experimental distinguishability of the latter mechanism through its magnetic-field dependence. The method is illustrated by comparing the results to be expected for three different random processes: (1) rotational diffusion, (2) random walk among the mj states of a rotational manifold of fixed J with no selection rules, (3) the same with a rigorous Δmj=±1 selection rule. Possible favorable experimental cases are discussed.
Thermodynamic Properties of Thionyl Fluoride from 13°K to Its Boiling Point. Entropy from Molecular and Spectroscopic Data
Authors: Pace E. L. , Turnbull B. F.
Published: January 2005

The heat capacity of thionyl fluoride has been measured from 12° to 230°K for a sample of 99.976 mole% purity as determined by the melting-point method. The heat of fusion was 1505.9 cal/mole at the solid—liquid—vapor equilibrium temperature of 143.25°K. The heat of vaporization at the normal boiling point of 228.84°K was 5091 cal/mole. The vapor pressure of the liquid to the normal boiling point has been measured, and the data are represented by log10Pmm=24.41879–1719.074/T−5.94452 log10Twhich was obtained by minimizing the square of the residuals of the pressure.

The density of the liquid is represented by d(g/cc)=2.389–0.003398T.

The entropy of thionyl fluoride gas in the standard state at the normal boiling point calculated from the experimental data is 63.56 cal/(mole·°K). A spectroscopic entropy of 63.28 cal/(mole·°K) is calculated from the product of the moments of inertia, IAIBIC=1.6562×10−114 g3·cm6 from microwave data and the following frequency assignment: v1(a′)=1336 cm−1; v2(a′)=808 cm−1; v3(a′)=530 cm−1; v4(a′)=378 cm−1; v5(a″)=748 cm−1; and v6(a″)=396 cm−1. The discrepancy between the two entropies is accountable in terms of the experimental uncertainty and therefore, the molecular parameters and frequency assignment are confirmed.
Ferromagnets and Simple Fluids near the Critical Point: Some Thermodynamic Inequalities
Authors: Griffiths Robert B.
Published: January 2005

It is often assumed that thermodynamic variables have a simple power-law behavior near the liquid—vapor critical point of a simple fluid; for example, that the difference in density of saturated liquid and vapor decreases as (Tc—T)β as the temperature T approaches its critical value Tc. Thermodynamic arguments are used to derive several inequalities relating exponents which describe the behavior of the isothermal compressibility, specific heat at constant volume, and various other quantities near the critical point. Many of the inequalities apply equally to the analogous problem of a ferromagnet near its Curie point. They are based on the usual ``stability'' or ``convexity'' conditions on the thermodynamic potentials together with other plausible, but less general, hypotheses.
Ion—Molecule Reactions in Hydrogen—Rare-Gas Mixtures
Authors: Aquilanti V. , Galli A. , Giardini-Guidoni A. , Volpi G. G.
Published: January 2005

Ion—molecule reactions in rare-gas—hydrogen systems have been studied by high-pressure mass spectrometry, using a specially designed ion source which employs the beta rays of tritium as ionizing medium. The rate constants for reactions of H3+ with rare gases and of rare-gas ions with hydrogen have been measured. The results are in qualitative agreement with radiolysis experiments on hydrogen—deuterium exchange, and if a quantitative comparison is attempted, it is possible to estimate the rate constant of the chain-propagation reaction. Experiments are also reported for N2–H2 and O2–H2 mixtures.
Kinetics of the Thermal Decomposition of Tetrafluoroethylene Oxide
Authors: Lenzi M. , Mele A.
Published: January 2005

The thermal stability of gaseous tetrafluoroethylene oxide has been examined between 40° and 140°C. In this range of temperatures two distinct modes of decomposition have been observed. At higher temperature a unimolecular process takes place with the formation of carbonyl fluoride, tetrafluoroethylene, and perfluorocyclopropane. Isomerization occurs through a heterogeneous reaction on the wall in the low-temperature range leading to trifluoroacetyl fluoride.

The unimolecular behavior is treated according to the Rice—Ramsperger—Kassel theory. A kinetic scheme, which is in agreement with the experimental results, is proposed for the formation of the products.
Theoretical Relationship between Surface Tension and Cohesive Energy Density
Authors: Schonhorn H.
Published: January 2005

The rigid-sphere theory of liquids is shown to yield an expression for the surface tension of a one-component liquid which is essentially identical to an expression previously derived by the author employing a qualitative approach. Such a correlation suggests that the rigid-sphere theory of liquids approach is applicable to a wide variety of nonpolar polymeric liquids.
Free-Ion and Crystalline Spectra of Pr3+ (Pr IV)
Authors: Crosswhite H. M. , Dieke G. H. , Carter Wm. J.
Published: January 2005

The spectrum of the free tripositive praseodymium ion (Pr IV) has been obtained under high resolution between 1200 Å and the infrared. The analysis has yielded all 49 levels of the four lowest configurations 4f2, 4f5d, 4f6s, 4f6p. A comparison with the crystal levels of Pr3+ in various lattices shows a depression of up to 5% in the anhydrous chlorides.
Neutral and Ionic Desorption of Cesium from Tungsten
Authors: Schmidt Lanny D. , Gomer Robert
Published: January 2005

Rates of neutral and ionic desorption of Cs from tungsten field emitters have been measured as functions of temperature and coverage, and the corresponding activation energies and frequency factors of desorption determined. The results for neutral desorption agree extremely well with the data of Taylor and Langmuir for coverages from near zero to 1.4×1014 atom/cm2, but fall below the heats of these authors at higher coverages. The combination of neutral and ionic heats yields a value of Φ=5.3 eV for the zero coverage work function of the regions from which ionic desorption occurs, in agreement with previous results for potassium. It is shown that surface equilibrium leads to a different averaging than independent evaporation, so that the above result is to be expected. The phenomenon of phase segregation observed by Taylor and Langmuir at very low coverages under steady-state conditions is discussed and shown to be a kinetic rather than a thermodynamic effect.
Energy Levels of Pr3+ in LaF3
Authors: Caspers H. H. , Rast H. E. , Buchanan R. A.
Published: January 2005

The absorption and fluorescence spectra of Pr3+(4f2) in LaF3 have been investigated in the spectral region 4000 to 60 000 Å. From the present study and previously published data, all of the 2J+1 Stark components of the 3H4,5,6, 3F2,3,4, 1G4, 1D2, 3P0,2, levels are identified. By means of a least-squares method, we have calculated the Slater and spin—orbit parameters that give a theoretical free-ion spectrum in close agreement with the observed spectrum of Pr3+(4f2) in LaF3 crystals. When the electrostatic interaction between 4f2 and 5d2 electronic configurations is taken into account, the average deviation between the calculated and the observed spectrum is 58 cm−1. The values of the parameters giving the best fit are F2=312.7 cm−1, F4=50.99 cm−1, F6=4.778 cm−1, and ζ=757.0 cm−1.
Microwave Spectrum, Structure, and Dipole Moment of 2,4-Dicarbaheptaborane (7)
Authors: Beaudet R. A. , Poynter R. L.
Published: January 2005

The microwave spectra of all monosubstituted carbon and boron isotopic forms, and one disubstituted boron isotopic form of 2,4-dicarbaheptaborane(7) have been analyzed. The skeletal boron and carbon atomic coordinates determined from the rotational constants show that the molecule is a pentagonal bipyramid. The two carbon atoms lie in the pentagonal base plane and are separated by one boron atom. The two apex boron atoms appear to lie on, or very near the C axis which is perpendicular to the pentagonal base. A molecular-dipole moment of 1.32±0.03 D is oriented along the planar symmetry axis.
Nuclear Magnetic Shielding of Alkali Ions in Crystals and Dilute Aqueous Solutions
Authors: Ikenberry Dennis , Das T. P.
Published: January 2005

The formulation for the Kondo—Yamashita overlap mechanism for the nuclear magnetic shielding in alkali halides developed earlier, is applied to the rubidium nucleus in RbCl, RbBr, and RbI crystals. The pertinent average energy denominators of perturbation theory are obtained using experimental pressure data on the magnetic shielding. Using these energy denominators, the calculated values of σRb, the chemical shifts for the rubidium nucleus in the crystal with respect to the free ion, are −2.17×10−4, −2.14×10−4, −2.11×10−4 for RbCl, RbBr, and RbI, respectively. When combined with Baron's experimental data on the chemical shifts with respect to dilute aqueous solutions, we obtain for σRbaq, which represents the chemical shift between the Rb+ ion in aqueous solution and the free ion, the values −0.88×10−4, −0.63×10−4, −0.60×10−4 from the RbCl, RbBr, and RbI data, respectively. These values are in fair agreement with the result σRbaq=−0.65×10−4 that we have derived using a model of six oriented water molecules around the Rb+ ion in dilute aqueous solutions.
Spin-Polarized Orbitals for Localized States in Crystals
Authors: Davison S. G. , Amos A. T.
Published: January 2005

Using the concept of different orbitals for different spins, in conjunction with the tight-binding approximation, it is possible to construct a set of spin-polarized orbitals (SPO's) in which electrons with different spins are localized on different crystal atoms. Thus, SPO's allow for the correlation between electrons with different spins and, for a pure crystal, are very similar to Löwdin's alternant crystal orbitals. For one-dimensional crystals, an analysis which resembles that for linear mixed crystals reveals that, for α- or β-spin electrons, the energy levels of the nonlocalized SPO's form two bands, while those of the localized SPO's lie either outside these bands or in the gap between them. Finally, Green's matrix method is employed to examine the effect on the SPO's of the perturbation produced by interior impurity atoms in the crystal, or chemisorbed atoms at the surface.
Two-Dimensional Second Virial Coefficients of Methane and Tetradeuteromethane on Graphitic Carbon
Authors: Sams John R.
Published: January 2005

Specific two-dimensional second virial coefficients are obtained from low-coverage adsorption isotherms for CH4 and CD4 on graphitic carbon between 220° and 290°K. These data are analyzed in terms of both classical and quantum-statistical models employing a Lennard-Jones potential, and corrections for non-planarity of the adsorbed phase are also included. The sign of the quantity [ε(H)—ε(D)]/ε(D) cannot be unambiguously determined, but this quantity is somewhat smaller than in the corresponding three-dimensional case. The measured nonadditivity of pair potentials amounts to about 15% of the gas-phase energy, and is in good agreement with independent theoretical predictions.
Effect of High Pressure on the Lattice Parameters of Al2O3
Authors: Hart H. V. , Drickamer H. G.
Published: January 2005

The effect of pressure to 300 kbar has been measured on the lattice parameters of Al2O3. Corundum has a rhombohedral unit cell and is relatively incompressible (∼9% in 300 kbar). Perhaps the most intersting feature involves an increase of the rhombohedral angle of about 0.5° over this pressure range.
Effect of High Pressure on the Compressibilities of NaI, LiF, and NaF
Authors: Pagannone M. , Drickamer H. G.
Published: January 2005

The effect of pressure to several hundred kilobars has been measured on the compressibilities of NaI, LiF, and NaF. For NaI and LiF the semiclassical Born—Mayer—Huggins theory gives a good fit over the entire pressure range. For NaI this is not necessarily expected as the large size of the I− ion relative to Na+ would indicate that next-nearest-neighbor interactions could be important. The equation is quite unsatisfactory for NaF, which is quite surprising as this should be a typical ionic crystal.
Transport Properties of Gases with Rotational States. II
Authors: McCourt F. R. , Snider R. F.
Published: January 2005

When a single-component gas possesses a nonzero but small local angular-momentum density, the left-hand side of the Boltzmann equation used for calculation of the transport coefficients must be modified in order to take into account the noncommutative properties of the internal angular-momentum pseudovector operator J. Such a modified Boltzmann equation is herein obtained and a tensorial expansion of the perturbation function φ in terms of irreducible Cartesian tensors is carried out. Expressions are obtained for the various transport coefficients connected with the pressure tensor, angular-momentum flux tensor, and heat-flux vector in terms of certain tensorial expansion coefficients. In particular, a nonzero local angular-momentum density is found to lead to a number of cross terms in the expressions for the macroscopic fluxes.
Diffusion Theory of Nonequilibrium Dissociation and Recombination
Authors: Keck James , Carrier George
Published: January 2005

The coupled vibration—dissociation—recombination process for molecules and atoms has been examined. Techniques for solving the appropriate master equations for both quantum (discrete) and classical (continuous) models are given. It is shown that the process is most easily treated classically and that in this case the master equation can be reduced to an equivalent diffusion equation. It is assumed that, after an initial vibration transient, during which reactions are negligible, the process may be treated using the steady-state approximation. During the steady-state phase, the usual phenomenological rate equations are valid and the ratio of the forward and reverse rate constants is the equilibrium constant, though the individual rate constants are depressed below their equilibrium values.

Comparison of the results with other theoretical work shows general agreement for similar models; comparison with shock-tube experiments on molecular dissociation and stellarator experiments on ionic recombination is encouraging.
Strong Coupling in Nuclear Resonance Spectra. V. Perturbation Theory for the Extreme Coupling Case
Authors: Waugh J. S. , Wei E. L.
Published: January 2005

The perturbation theory of NMR spectra is given for the case in which the relative chemical shift ν0δ between two groups is much smaller than the coupling constant J. Results are given for the systems AB, AB2, AB3, A2B2, and A2B3 from which it is possible to obtain the parameters from the appropriate spectra without detailed analysis. The proton spectra of methylacetylene is discussed as an example.