bluuebunny/crossref_metadata_2025 huggingface dataset:
The Vapor Pressures and Critical Constants of Pure Ozone
Authors: Jenkins Arthur C. , Birdsall Clair M.
Published: January 2005

Vapor pressures of pure ozone have been measured over the range −183°C to −30°C with an estimated accuracy of ±3 percent and are represented by the equation logPmm=8.25313−814.941587T−0.001966943T.The normal boiling point is −111.9°C±0.3°C. The critical temperature has been determined experimentally and found to be −12.1°C±0.1°C. The critical pressure derived from this critical temperature and the vapor pressure equation is 54.6 atmospheres absolute. Results are, in general, in good agreement with the meager data in the literature. The precision of the vapor pressure data is limited by the unstable nature of ozone and the necessarily small samples which must be used for measurements in the interests in the interests of safety.
Self-Diffusion in Solid Sodium. II. The Effect of Pressure
Authors: Nachtrieb N. H. , Weil J. A. , Catalano E. , Lawson A. W.
Published: January 2005

Hydrostatic pressure is found to decrease the rate of self-diffusion in sodium. The free energy of activation is a linear function of the melting point, and the enthalpy of activation is proportional to the melting point. For sodium and for all cubic metals (except lead and tungsten) for which diffusion data exist the enthalpy of activation is related to the latent heat of fusion by the equation ΔH = 16.5 Lm. The change in D0 for sodium with pressure is expressible in terms of the compressibility and the activation entropy change.
Photochemistry of Ferrous Ions in Aqueous Solution
Authors: Rigg Tyson , Weiss Joseph
Published: January 2005

The photochemistry of ferrous ions in aqueous solutions has been investigated, and it has been confirmed that irradiation in the quartz ultraviolet, in the absence of oxygen, leads to the formation of ferric salt and molecular hydrogen. It has been concluded further that the primary absorption of a light quantum results in the formation of excited ions, (Fe2+·H2O)*, a considerable proportion of which undergo processes of deactivation, while the remaining (about one-tenth) dissociate according to (Fe2+·H2O)*→Fe3++OH−+H, leading to the formation of hydrogen atoms. The latter can undergo back reactions of the type Fe3++H→Fe2++H+. Investigation of the pH dependence of the quantum yield has led to the assumption that hydrogen atoms can also react according to H+H(hydr)+⇌H2(hydr)+, leading to the formation of hydrated hydrogen molecular ions which intervene in this process according to the reaction Fe2++H2+→Fe3++H2.

Other experimental evidence and some theoretical considerations which have led to the assumption of H2+ (hydr) in aqueous solution are referred to.
Theory of Ion Exchange for Polyelectrolytes Undergoing Electrolytic Transference
Authors: Wall Frederick T. , Grieger Philip F.
Published: January 2005

It has been observed experimentally that polymeric ions generally have associated with them a large number of small ions of opposite charge. These smaller ions, which are considered bound to the polymeric ions, are capable of exchanging with free ions in solution. The rate of this exchange can be determined by certain electrolytic transference experiments involving the use of radioactive tracers. The theory of such transference experiments is worked out by formulating and solving appropriate differential equations subject to certain boundary conditions. It is then shown how results of these transference studies can be used for evaluating ion rate exchange constants.
Rotational Isomerism and the Vibrational Spectrum of Sym-Dideuterodibromoethane
Authors: Bernstein H. J. , Pullin A. D. E. , Rabinovitch B. S. , Larson N. R.
Published: January 2005

Trans-ethylene-d2 was brominated by two methods, which involved different stereochemical paths, to give 95 percent meso-BrDHC-CHDBr as one product and a mixture of meso- and racemic-BrDHC-CHDBr as the other. Liquid phase Raman spectra and liquid and solid phase infrared spectra of these materials have been obtained and a tentative assignment of the vibrational frequencies of BrDHC-CHDBr to the trans and skew configurations of the meso and racemic compounds has been made.
Interdiffusion of Polyvinyl Acetate with a Series of Solvents
Authors: Hutcheon A. T. , Kokes R. J. , Hoard J. L. , Long F. A.
Published: January 2005

The Lamm scale method has been used to follow the interdiffusion of polyvinyl acetate with ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and triacetin at 30°C, and with acetone at 20°, 30°, and 40°C. For all these systems the mutual diffusion coefficient attains a maximum value at intermediate polymer concentrations. At a given concentration and temperature the D(c) values are largest with acetone and much the smallest with triacetin, although the relative variation in D(c) over the concentration range is actually largest with the latter. The general variation of D(c) with concentration can be plausibly interpreted in terms of the mass flow-intrinsic diffusion concept introduced by Hartley. For the system acetone—polyvinyl acetate the calculated energy of activation for the diffusion is nearly constant at 1 kcal in the concentration range 0 to 40 grams polymer per 100 cc of solution but then rises rapidly to 10 kcal at 90 grams polymer per 100 cc.
The Quantum-Mechanical Partition Function
Authors: Green H. S.
Published: January 2005

An exact evaluation is attempted of the quantum-mechanical partition function for an assembly of similar particles with central interaction. Quantum-mechanical analogs of the classical cluster integrals are derived and evaluated as far as required to determine the virial coefficients. It is shown that the results are particularly well adapted for computation at very low temperatures.
Viscosities of Some Lower Aliphatic Alcohols at Constant Volume
Authors: Jobling A. , Lawrence A. S. C.
Published: January 2005

From an analysis of all the published experimental data for methyl, ethyl, n-propyl, isobutyl, and n-octadecyl alcohols, it is shown that, even for these compounds, at constant volume logη is a rectilinear function of 1/T and the general pattern of behavior is similar to that described previously. Ev, the energy of activation of viscous flow at constant volume, is plotted as a function of volume, and the curve for ethyl alcohol shows an apparently anomalous minimum.
Dielectric Properties of Ice and Solid D2O
Authors: Auty Robert P. , Cole Robert H.
Published: January 2005

Complex dielectric constants have been measured for ice from the melting point to −65°C, and for solid D2O to −35°C, by a combination of bridge and transient methods. For both, the dispersion is described by the simple Debye formula, and the relaxation times τ by the simple rate expression τ = A exp(B/RT). For ice, A = 5.3×10−16 sec, B = 13.2 kcal/mole; and for solid D2O, A = 7.7×10−16 sec, B = 13.4 kcal/mole. The equilibrium dielectric constant for ice is 91.5 at 0°C and increases at lower temperatures; the values for solid D2O are only slightly smaller. Measures taken to minimize errors from voids in the sample and direct current conductance are discussed.
Evaluation of the Zeta-Sums for Rotation-Vibration Interaction in Axially Symmetrical Molecules
Authors: Lord R. C. , Merrifield R. E.
Published: January 2005

It is shown that the contribution of a set of equivalent nuclei to the zeta-sum for the fundamental vibrations of any symmetry species in a molecule possessing only one multiple axis of symmetry is zero unless the nuclei are situated on the axis. In the latter case the contribution of the set of equivalent nuclei to the zeta-sum in any species is one unit for every degree of freedom the set contributes to that species. With the help of these theorems a table is worked out from which the zeta-sums can be determined immediately for any axially symmetrical molecule of known structure. Use of the table is illustrated with several simple examples.
An Electron Diffraction Study of Some Glasses
Authors: McClurg G. O.
Published: January 2005

The interatomic spacings as obtained from the radial distribution method of analysis of electron diffraction patterns are given for vitreous silica, Vycor, and Pyrex glasses. The results are in general agreement with the x-ray diffraction results published by others.
Theoretical View on ``Hot Atom Chemistry''
Authors: Capron P. C. , Oshima Y.
Published: January 2005

Considering only collisions of the ``billiard ball'' type the total retention is obtained as a sum of partial retentions for an infinite number of collisions. Expressions are derived which give the retention as a function of the initial energy of the recoil atom. The calculation shows that it is not possible to determine the initial recoil energy by the retention.
Elastic Scattering and Neutralization of Low Velocity Hydrogen Ions in Ethane and Propane
Authors: Simons J. H. , McAllister S. A.
Published: January 2005

The low velocity scattering of H+, H2+, and H3+ in both ethane and propane have been measured at ion velocities of less than 150 volts. Ion neutralization was detected and measured for all three ions in both hydrocarbons and elastic scattering potential functions evaluated for all six interactions. The scattering of hydrogen ions in the first four members of the series of straight chain saturated hydrocarbons can now be compared, and it is shown that they change in a systematic manner.
The Properties of the Interstitial Compounds of Graphite. II. The Structure and Stability of Graphite Residue Compounds
Authors: Hennig Gerhart
Published: January 2005

1. Controlled decomposition of lamellar compounds of graphite produces substances intermediate in composition between graphite and lamellar compounds. These intermediate compounds have been termed residue compounds. They are much more resistant to decomposition than the lamellar compounds.

2. The x-ray pattern of residue compounds shows a very slight increase in the c spacing of the graphite lattice. The increase is entirely insufficient to account for the trapped reactant. Consequently, the bulk of the trapped reactant is believed to be situated at crystal imperfections.

3. Quantitative studies of the composition of graphite bromide residue compounds have shown that their composition is strongly dependent on the type and subdivision of the graphite used and the temperature to which the compounds have been heated.
The Properties of the Interstitial Compounds of Graphite. III. The Electrical Properties of the Halogen Compounds of Graphite
Authors: Hennig Gerhart
Published: January 2005

The presence of lamellar or of residual bromine in artificial graphite reduces the resistance, the absolute magnitude of its temperature coefficient near room temperature, and the magneto resistance. The Hall coefficient increases and eventually changes from negative to positive values. The changes resemble very closely those obtained in the oxidation of graphite in sulfuric acid. This similarity in properties suggests that the electron acceptors in these compounds are only weak scattering centers for conduction electrons.

Since the electrical properties of graphite bisulfate and of graphite bromide are very similar, it may be assumed that both compounds are of a similar type. Since the bisulfate compound is ionic in nature, the bromine in graphite bromide is also probably ionized. On this assumption the graphite bromides have the formulas CnBr·3 Br2 for the lamellar and CnBr·2.25 Br2 for the residue compounds.

Chlorine reacts with graphite at low temperatures only. The properties of the compounds of chlorine and graphite resemble in all respects those of the compounds of bromine and graphite. Attempts to react iodine and graphite have failed. Iodine chloride, however, reacts rapidly with graphite.
A Note on the Detection of Free Radicals by Means of Paramagnetic Resonance Absorption. Biradicals
Authors: Hutchison Clyde A. , Kowalsky Arthur , Pastor Ricardo C. , Wheland G. W.
Published: January 2005

The application of paramagnetic resonance absorption to the detection of organic free radicals is discussed. The advantages of this method over conventional measurements of magnetic susceptibility are illustrated by the results of measurements on p,p′-biphenylene-bis-(diphenylmethyl).
Self-Consistent Group Calculations on Polyatomic Molecules. II. Hybridization and Optimum Orbitals in Water
Authors: Klessinger Martin
Published: January 2005

GF calculations for the ground state of the water molecule are reported for three sets of orbital exponents, and optimum valence hybrids, determined by systematic variation of the hybridization parameters until the total electronic energy was a minimum, are compared with hybrids obtained by other criteria. Different methods of constructing localized inner-shell groups are discussed.
Electronegativity
Authors: Klopman G.
Published: January 2005

The concept of ``electronegativity'' is discussed and reviewed in the light of recent observed relationships between successive ionization potentials. A differentiation is made between atomic and molecular electronegativity and particular reference is made to the principle of equalization of molecular electronegativities in the process of forming a bond.

The Rydberg equation for atoms is used as a basis for the quantitative calculation of the atomic spectra and electronegativity of systems in any valency state. The resulting equation can be used either to calculate atomic electronegativities or to determine quantitatively the diagonal matrix elements in SCF calculations for molecules involving heteroatoms.
Selection of Molecular Matrix Elements from Atomic Data
Authors: Cusachs Louis Chopin , Reynolds James Ward
Published: January 2005

A simple internally consistent recipe for obtaining atomic orbital matrix elements (Hii) from atomic spectral data agrees with values obtained from empirical molecular ionization potentials via molecular orbital calculation. Regularities observed lead to very simple expressions useful for adjustment of parameters for charge transfer. Various assumed relations between atomic valence-state quantities and orbital matrix elements are compared with the observed data for selected atoms. In the cases studied, valence-state ionization potentials depend quadratically on the degree of ionization, but can be satisfactorily approximated by linear functions for net charges between −1 and +1. In the linear approximation, the second term is the same for both occupancies of both s and p orbitals.
Multicenter Integrals in Quantum Mechanics. I. Expansion of Slater-Type Orbitals about a New Origin
Authors: Harris F. E. , Michels H. H.
Published: January 2005

Convenient and accurate formulas have been found which implement the spherical-harmonic expansion of a Slater-type orbital about a point displaced from the orbital's center. These formulas include, as a special case, the expansion of spherically symmetric orbitals which has been reported previously. The results are presented in algebraic form, suitable for machine computation, and have been tested for the transformation of any Slater-type orbital with n≤7, l≤3, | m |≤l to an arbitrary space-fixed point.

By the use of this analysis, in conjunction with the properties of the rotation group, it is now possible to evaluate directly, the general multicenter electron-repulsion integral expressed in terms of Slater-type orbitals. The convenience of this direct approach suggests that previous analyses in terms of Gaussian orbitals or Gaussian approximations to Slater-type orbitals, replete with their poor radial dependence, may no longer offer any computational advantages.
Determination of Intermolecular Forces
Authors: Hirschfelder Joseph O.
Published: January 2005

Some of the basic problems associated with the determination of intermolecular forces are considered.
Calculation of Expectation Values
Authors: Jones Leon L.
Published: January 2005

A method of optimizing approximate wavefunctions for the expectation value of operators other than the energy and a statement of limits on the exact values from the stationary values would be a valuable addition to quantum mechanics. Two methods which appear to have the above properties in simple systems are indicated and comments on the possible expansion to more complex systems.
Theory of the Origin of the Internal-Rotation Barrier in the Ethane Molecule. I
Authors: Wyatt Robert E. , Parr Robert G.
Published: January 2005

The energy barrier of 2.9 kcal/mole hindering internal rotation in the ethane molecule may be conveniently decomposed into a nuclear—nuclear term which favors the staggered conformer by 5.1 kcal/mole and an electronic energy term of 2.2 kcal/mole favoring the eclipsed form. Through use of the integral Hellmann—Feynman theorem, the electronic energy change may be expressed as ΔE= ∫ ρES(1)H′(1)dτ(1), where ρES(1) is the one-electron transition density between the eclipsed and staggered states and H′ (1) is the difference between the one-electron nuclear—electron attraction operators for the two forms. By expanding both ρES(1) and H′ (1) in Fourier series in terms of the azimuthal angle φ about the carbon—carbon axis, one may obtain the explicit dependence of the electronic energy change on the threefold component ρ3 of the transition density, ΔE≈π ∫ ρ3(r, θ)A3(r, θ)dτr,θ, where A3(r, θ) is the threefold component of the operator H′ (1). This formula shows precisely how the electronic component of the internal-rotation barrier arises from the fact that in both the staggered and eclipsed conformers the electron density is not cylindrically symmetric about the carbon—carbon axis, but contains appreciable threefold components. Analysis of the best available ethane wavefunctions confirms the idea that these threefold density components are most important near the protons.
Suggestions from Solid-State Theory Regarding Molecular Calculations
Authors: Slater J. C.
Published: January 2005

It is suggested that one can simplify Hartree—Fock calculations on polyatomic molecules by using the free-electron exchange correction, and by replacing the actual potential, Coulomb plus exchange, by a spherical potential for each atom, with a constant potential outside the spheres, as discussed by Eyges.
Quantum-Mechanical Interfacial ``Trigger'' Action in Macromolecular Replication
Authors: McMullen A. I.
Published: January 2005

The aggregation and association of macromolecules, particularly of polynucleotides, is considered from the point of view of equilibria between monomeric and micellar structures. The polynucleotide is considered as a ``fibrillar micelle'' in dynamic equilibrium with the biological membrane represented as a ``laminar micelle'' and a mechanism of triggering the upset of this equilibrium in the light of charge transfer reactions is discussed in order to point up possible applications of the quantum approach.
Quantum Characterization of Electronic Levels in Molecules
Authors: Asundi R. K.
Published: January 2005

It is now possible to deduce, in more than one way, the number, nature, quantum characterization, and energy order of electronic levels of diatomic molecules. Experimental verification and identification of these levels, based on vibrational structure of the bands are, in several cases, misleading. Rotational structure analysis and isotopic substitution can, however, in general, give a unique answer to this question. This paper gives a few such instances recently met with in our laboratory.
Convergence in One-Center Expansions. H2+
Authors: Joy Hubert W. , Handler George S.
Published: January 2005

Inter- and intrashell convergence in a one-center expansion of H2+ for the 1sσg and 2pσu states is examined and convergence laws deduced.
Theory of Vibration—Rotation Interactions in Overtone Bands of Tetrahedral XY4 Molecules
Authors: Fox Kenneth
Published: January 2005

The possibility of a new overtone band in the infrared absorption spectrum of tetrahedral XY4 molecules has been investigated theoretically. This band is associated with the E vibrational part of the first overtone of an infrared-active fundamental. The new band is active only through vibration—rotation interactions. Its intensity is very small compared to that of the F2 vibrational part of the same overtone. Calculations of energy levels and relative intensities have been applied to the infrared absorption spectrum of CD4 in the 4500-cm−1 region.
Perturbation Theory in Terms of Commutator Brackets
Authors: Goodman Gordon L.
Published: January 2005

Explicit formulas for changes produced by a perturbation of a quantum-mechanical system are given in terms of commutator brackets. Conditions that must be satisfied in order that these formulas be useful are discussed. Finally, it is shown how these new perturbation formulas are related to more usual ones in terms of energy denominators.
Some Ideas Concerning the Effects of Substituents on the Electronic Spectrum of Parabenzoquinone
Authors: Stevenson Philip E.
Published: January 2005

A description is given of the derivation of equations describing the changes in energy of the two lowest π—π transitions in parabenzoquinone as functions of substituent type and position. The derivation is adapted from the work of Petruska on cyclic polyenes. A full account is to be published elsewhere.
Self-Consistent-Field Wavefunctions and Computed Potential-Energy Curves for the NH3 and NH Molecules, in One-Center Approximation
Authors: Joshi Bhairav D.
Published: January 2005

Single-determinant self-consistent field wavefunctions calculated by the one-center expansion method are reported for the NH3 and NH molecules. The molecular orbitals were expanded in terms of symmetry adapted Slater-type orbitals centered at the heavy nucleus. To obtain the potential-energy curve for the NH3 molecule corresponding to the tunneling motion of the N atom through the H3 plane, the calculations were carried out for twelve different geometrical configurations. In the present work only those geometrical configurations of NH3 are considered for which all three N–H distances are the same, and are denoted by RNH(NH3). For each geometrical configuration of NH3, defined by a fixed value of the bond angle (or the apex angle), the optimum values of RNH(NH3) and basis function exponents were determined. For the NH molecule, the calculations were carried out at seven different internuclear distances, RNH. At each RNH, the best basis function exponents were determined. These seven points were used to construct the potential-energy curve of NH. For NH3 in the equilibrium configuration, the calculated values for the bond length, bond angle, total energy, dipole moment, and the first ionization potential, are 1.867 bohr, 109.342°, −56.084186 hartree, 0.5993 a.u. (1.5231 D) and 0.4155 hartree, respectively. For planar NH3, the calculated bond length, total energy, and the first ionization potential are 1.853 bohr, −56.043064 and 0.3836 hartree, respectively. For the NH molecule, the calculated equilibrium bond length, total energy, dipole moment, and the 1π orbital energy are 1.90 bohr, −54.90638 hartree, 0.7515 a.u. (1.9100 D), and 0.5281 hartree, respectively.
Heat Capacity and Entropy of Mn(NH4)2(SO4)2·6H2O from 1° to 4°K in Fields up to 24 000 Oe Perpendicular to the b Axis; Direct Observation of Magnetic Imperfection
Authors: Fritz J. J. , Davies R. Ll. , Bernard H. W. , Aston J. G.
Published: January 2005

The magnetization behavior of a spherical single crystal of Mn(NH4)2(SO4)2·6H2O has been investigated from 1° to 4°K in fields up to 24 000 Oe perpendicular to the 2̄01 crystal plane, along 15 (approximately) isentropic paths for entropies ranging from about 1.6 cal mole−1·deg−1 to 3.5 cal mole−1·deg−1. The heat capacity of the specimen has been measured at 0, 4360, 6450, 12 900, and 17 760 Oe. The two sets of measurements have been combined to obtain the entropy as a function of field and temperature over the range covered. The heat capacity and entropy are in all cases close to the values predicted by a Brillouin function with S=5/2, g=2.000 with small but significant deviations due to departures from ``ideal'' paramagnetic behavior. The deviations are shown clearly in the behavior of (H/T) along isentropes, which is presented for 10 particular values of the entropy. They correspond qualitatively to that predicted by the crystalline field obtained from other sources.
Thermal Diffusion in Multicomponent Gas Mixtures
Authors: Ghosh A. K. , Batabyal A. K. , Barua A. K.
Published: January 2005

The thermal diffusion factor has been studied by an effective four-tube trennschaukel for a ternary and a quaternary system. The systems studied are, (1) H2–CO2 with He added as the third component and (2) H2–CO2 with the He–Ne mixture added as the third and the fourth components. A pronounced dip has been obtained in the thermal diffusion factor vs composition curves for both the ternary and the quaternary systems. Attempt has been made to interpret the data in terms of the recent theory for thermal diffusion in polynary gas mixtures.
Microwave Spectrum of Propylene Imine
Authors: Hayes Donald , Beeson E. L.
Published: January 2005

The microwave spectrum of propylene imine has been investigated in the range 9–40 GHz. The rotational constants associated with two species of molecules were found to be 16 893.00, 6533.71, and 5761.26 MHz for the trans isomer and 16 665.66, 6558.64, and 5812.36 MHz for what is probably the cis isomer. The dipole-moment components for the trans isomer were found to be μa = 0.21±0.06, μb = 0.81±0.03, and μc = 1.36±0.02 D, and for the other species of molecule, μa = 1.28±0.01, μb = 0.95±0.08, and μc = 0.78±0.08 D.
Semiclassical Theory of Inelastic Scattering
Authors: Cross R. J.
Published: January 2005

The Schiff approximation is applied to the problem of collisions of two asymmetric molecules. The treatment includes effects of energy interchange between translational and internal degrees of freedom, and it includes transitions to states not directly coupled by the intermolecular potential. The differential and partial scattering cross sections are obtained in terms of a phase-shift matrix which is a generalization of the WKB phase shift. This matrix may be obtained simply as an integral of the matrix of the intermolecular potential over the classical trajectory. Semiclassical approximations similar to those used in the case of elastic scattering are made, and the angular distribution reduces to the previously obtained classical expression. The approximations used in the derivation are that l and k (the orbital angular momentum quantum number and the wavenumber) must be large and Δk/k must be small. The calculations are reasonably simple for scattering below about 30° where the scattering may be considered as a perturbation on a straight-line trajectory.
Thermal Dependence of Fluorescence and Lifetimes of Sm2+ in Several Host Lattices
Authors: Alam A. S. M. Mahbub'ul , Di Bartolo Baldassare
Published: January 2005

Fluorescence spectra and lifetimes of Sm2+ in CaF2 and SrF2 were studied from 15° to 300°K and in BaClF from 15° to 650°K. A sharp line appears above a wide background at ∼100°K and 14 115 cm−1 for CaF2:Sm2+ and at 140°K and 14 350 cm−1 for SrF2:Sm2+. Lifetimes at 80°K are ∼2×10−6 and ∼10−3 secs, respectively, in agreement with previous workers' results. BaClF:Sm2+ presents several sharp lines corresponding to transitions from three metastable states 5D0 (14 542 cm−1), 5D1 (15 878 cm−1), and 5D2 (17 820 cm−1) to the ground-state multiplets 7F0 to 7F4. The most efficient states at 300°, 80°, and 15°K are, respectively, 5D0, 5D1, and 5D2; above 350°K, the 5D1 fluorescence increases relatively to the 5D0 fluorescence, contrary to what happens from 77° to 350°K. Several 5D0 lines persist and remain sharp (∼4 Å at 650°K) even at high temperatures with no observable background. Under pulsed excitation the decays of the fluorescence lines are consistent with an optical excitation in the 4f55d bands, which is transferred non-radiatively to the 5D2 state and then cascades to lower levels with rates slower with decreasing temperature and for the 5D1—5D0 energy gap. At 300°K the 5D1 fluorescence presents a double decay, but at higher temperatures the 5D1 decay is purely exponential with the same time constant of 5D0. The continuous and pulsed fluorescence data furnish evidence of pumping by phonon annihilation in the 5D1 state from the lower 5D0 state at temperatures greater than 300°K.
Rotatory Diffusion Constant of a Chain Molecule
Authors: Isihara A.
Published: January 2005

The rotatory diffusion constant of a chain molecule of spherical configuration is evaluated by the method which the author developed recently for the intrinsic viscosity. The theory is simpler than that given by Riseman and Kirkwood and yields a more general result in terms of the moment of the segment distribution function. The general result reduces to a simple expression for a flexible chain in terms of the molecular constants based on a pearl-necklace model. The relation between the intrinsic viscosity and the rotatory diffusion constant is proved to be the same as Riseman and Kirkwood's. This is due to the same flow mechanism underlying the viscosity and diffusion phenomena.
Methyl Hydroperoxide in Photo-oxidation of Acetone
Authors: Cohen A.
Published: January 2005

Acetone was photo-oxidized in a static system between 200° and 300°C. Its pressure was 100 mm while that of oxygen varied between 2 and 4 mm. This chain-type photo-oxidation reaction gave a considerable yield of methyl hydroperoxide. This was directly confirmed by polarography and paper chromatography. In the early stages of the work, the methyl hydroperoxide yield tended to decrease through identical successive photo-oxidations. When a photolysis was performed in the same cell in which a number of photo-oxidations had taken place, analysis showed the possibility of the presence of an oxidative species strongly absorbed to the silica walls. This difficulty was practically overcome. Among the main products were methanol, formaldehyde, water, acetic acid, and ethylene oxide. As the temperature rose the yield of methyl hydroperoxide decreased.
Study of the Electronic Structure of Molecules. VII. Inner and Outer Complex in the NH4Cl Formation from NH3 and HCl
Authors: Clementi Enrico , Gayles J. N.
Published: January 2005

Analysis of the variation of the internuclear distances and of the frequencies in the formation of NH4Cl from NH3 and HCl indicates that for the NH4Cl molecule there are two rather distinct regions for the molecular complex, both stable with respect to the component molecules NH3 and HCl. Contrary to previous assumptions, no outer complex was found. The potential surface of the two regions goes into one another smoothly since there is no activation barrier between the two complexes. From computations, estimates of the frequencies, and from the computed value of the dissociation energy of NH4Cl with respect to NH3 and HCl, it is found that at temperatures around 400°C and at one atmosphere of pressure the NH4Cl molecule dissociates almost totally into NH3 and HCl. This is in agreement with experimental data. It is, therefore, proved that the assumption of an outer complex and of an activation barrier is unnecessary for the explanation of the NH4Cl dissociation process into NH3 and HCl. Tables of the equilibrium constant at various temperatures and of other thermodynamic data are presented.
Fluorescence and Energy Transfer between Nd3+ and Yb3+ in LaF3
Authors: Rast H. E. , Caspers H. H. , Miller S. A.
Published: January 2005

Energy transfer has been observed in single crystals of LaF3 codoped with Nd3+ and Yb3+ resulting from the near resonance transitions between states of Nd3+ and the 2F7/2→2F5/2 states of Yb3+. From an analysis of the fluorescence and absorption spectra of Yb3+, all the crystalline field Stark components of the 2F7/2 and 2F5/2 state were determined. The four crystal sublevels of the 2F7/2 ground states are found at 0, 185, 401, and 870 cm−1. The three levels of the excited 2F5/2 states are determined at 10 260, 10 430, and 10 660 cm−1, respectively. Based on these values of the Stark levels, the spin—orbit coupling radial integral for Yb3+ in LaF3 is calculated to be 2882 cm−1.
Triple Resonance Method for Molecular hfs Spectroscopy: Measurements on 133Cs19F
Authors: Zorn Jens C. , Stephenson David A. , Dickinson J. Thomas , English Thomas C.
Published: January 2005

Three sequential oscillatory fields are employed in a molecular beam electric resonance spectrometer in order to observe molecular hfs transitions which do not obey the criteria for observability in the usual beam apparatus. The triple resonance method has been used to examine the hfs of CsF under conditions of very weak external fields. The method shows considerable promise for the detailed study of molecular hfs when more than one nucleus has a quadrupole moment, and for the observation of transitions at audio frequencies between closely spaced molecular energy levels.
Stability Conditions for the Solutions of the Hartree—Fock Equations for Atomic and Molecular Systems. Application to the Pi-Electron Model of Cyclic Polyenes
Authors: Čížek J. , Paldus J.
Published: January 2005

The stability conditions which ensure that the Hartree—Fock determinant minimizes the energy expectation value are rederived using the language familiar in quantum chemistry. These stability conditions are then specified for the case of closed-shell electronic systems which allow additional simplification of the conditions as well as a certain classification of the instabilities.

Examples of the instabilities of different types are presented and the case of the so-called singlet instabilities—most interesting from the physical point of view—is studied in detail for the pi-electron model of cyclic polyenes.
Magnetic Resonance Studies of Ion Solvation. The Hydration of the Cobaltous Ion
Authors: Chmelnick A. M. , Fiat D.
Published: January 2005

Evidence is presented that cobaltous ion in aqueous solution retains a coordination number of 6 in a temperature range of −10° to +183°C. The temperature dependence of the oxygen-17 NMR linewidths and chemical shifts of the noncoordinated water were measured. The parameters of water exchange between the first hydration sphere and the bulk were determined and found to be: (τm)27°C=4.2×10−7 sec, ΔH‡=10.4 kcal/mole, ΔS‡=5.3 e.u. The oxygen-17 hyperfine coupling constant with the unpaired electrons of the cobaltous ion was found to be A/h=—(1.70±0.02)×107 Hz. The relaxation time of the unpaired electrons of the cobaltous ion was calculated and found to be (T1e)183°C=4.6×10−13 sec, assuming T1e=T2e. Earlier observations relevant to those reported here are discussed and, in some cases, reinterpreted.
Zero-Field Splitting in Phosphorescent Triplet States of Aromatic Hydrocarbons. II. Polyphenyl Benzenes
Authors: Orloff M. K. , Brinen J. S.
Published: January 2005

The zero-field splitting parameters D, E, and D* are calculated theoretically for the lowest triplet states of five polyphenyl benzenes. The agreement between theory and experiment is good. The calculated values for D* are uniformly too high by about 5%-10%. The calculations indicate that the ring-ring bond in biphenyl has double-bond character in its lowest triplet state and, therefore, the molecule is planar in its phosphorescent state.
X-Ray Absorption in Molecules; SF6
Authors: Best P E.
Published: January 2005

Usually, the active-electron approximation, in which only one electron changes quantum numbers, gives an adequate description of the K x-ray absorption spectra of molecules. The K x-ray absorption spectrum of sulfur in SF6, recently reported by LaVilla and Deslattes, cannot be described by this model, however. There is evidence that a variety of ionic states of the residue are formed in the process of x-ray absorption. It appears that the reason for this unusual behavior is the large difference in configuration interaction occurring in the parent and residue molecules, respectively. Experiments to test some aspects of this model are suggested.
Exact Finite Method of Lattice Statistics. II. Honeycomb-Lattice Gas of Hard Molecules
Authors: Runnels L. K. , Combs L. L. , Salvant James P.
Published: January 2005

Thermodynamic properties have been obtained using the matrix method for a two-dimensional honeycomb-lattice gas of hard molecules which prevent simultaneous occupancy of nearest-neighbor sites. Exact results have been obtained for cylinders of infinite length and finite circumference from 6 to 18 sites. Uniform trends with increasing circumference lend confidence to extrapolations used to infer the behavior of systems of infinite width. We find a great similarity with the corresponding square-lattice gas and a second-order phase transition at activity z=7.92±0.08, reduced pressure p/kT=1.12±0.05, and relative density ρ/ρ0=0.845±0.02. The compressibility appears to be infinite at the transition.
Kinetics and Mechanism of Hydrogenolyses. The Addition of Hydrogen Atoms to Propylene, Toluene, and Xylene
Authors: Benson S. W. , Shaw R.
Published: January 2005

Previously measured rates of hydrogenolysis of propylene, toluene, and xylene fit −d[RCH3]/dt=10(11.5±1)−(55±3)/θ[RCH3][H2]1/2 mole liter−1·sec−1 (where θ is 2.3RT kcal mole−1) over an unusually wide range of conditions. In the case of toluene, for example, the range is 107 in rate, 105 in hydrogen pressure, and 500°C in temperature. We propose the mechanism H2⇄2H,H+RCH3⇄RH+CH3,CH3+H2⇄CH4+H,giving −d[RCH3]/dt=K11/2k2[RCH3][H2]1/2. Substitution of values for K1 and k2 gives rate constants and Arrhenius parameters in excellent agreement with all reliable data.
Propagation of Density Disturbances in a Dense Hard-Sphere Gas
Authors: Ranganathan S. , Nelkin Mark
Published: January 2005

Approximate calculations of S(K, ω)—the double Fourier transform of the density—density correlation function—for the linearized Enskog equation for hard spheres are presented. The interaction terms are the usual Boltzmann collision integral and the collisional transfer terms. The former is replaced by a single relaxation-time kinetic model, while the collisional transfer terms are evaluated, as a first approximation, with a local Maxwellian for the distribution function. The numerical results at small K exhibit the expected peak at ω=cK due to sound propagation, in agreement with the predictions of the linearized hydrodynamic calculations. A peak is found to persist at large wavenumbers corresponding to a modified form of collective excitation. However, this peak disappears when first-order corrections to the local Maxwellian approximation in the collisional transfer terms are made. The feasibility of light- and neutron-scattering experiments to investigate the regions of interest is discussed.
Proton Relaxation Times and Translational Diffusion in Ferroelectric Potassium Ferrocyanide Trihydrate
Authors: O'Reilly D. E. , Tsang Tung
Published: January 2005

Proton spin—lattice relaxation times (T1) and relaxation times along the rf field (T1ρ) have been measured from 120° to 330°K in ferroelectric K4Fe(CN)6·3H2O(KFCT). The T1 data show a single minimum at 220°K which is to ascribed a 180° flip motion of the water molecules detected in a previous study of deuteron magnetic resonance. The T1ρ data exhibit two minima: one at 140°K associated with the 180° flip motion and another at 285°K which is ascribed to an exchange of water molecules due to translational diffusion. The presence of translational diffusion was confirmed by measurement of the exchange of heavy water with KFCT particles using a direct weighing method. The previously proposed model for the water molecule positions in KFCT is revised to agree with a recent neutron-diffraction structural determination. Deuteron and proton resonance data are reinterpreted in terms of the new structure which agrees with a previous proposal by Kiriyama et al., and in terms of two types of water molecular motions, the translational diffusion and 180° flip.
Mass Spectrometric Observations of Argon Clusters in Nozzle Beams. I. General Behavior and Equilibrium Dimer Concentrations
Authors: Milne Thomas A. , Greene Frank T.
Published: January 2005

Nucleation phenomena in nozzle beams were studied mass spectrometrically. The effect of pressure and orifice size on argon cluster distributions is presented together with a discussion of the factors affecting the interpretation of the cluster ion intensities. An extrapolation to zero orifice size for argon dimer mole fractions yields results in agreement with calculated equilibrium concentrations of Ar2.
Shock Compression of Argon. III. The Thomas—Fermi—Dirac Theory
Authors: Ross M. , Alder B. J.
Published: January 2005

The Thomas—Fermi—Dirac theory is shown to be remarkably accurate in predicting the experimentally available Hugoniot of argon. Furthermore, the theory predicts equally well both the 0°K isotherm and the Hugoniot of xenon. For the xenon Hugoniot it is shown that electronic excitations contribute significantly at the higher pressures.
Magnetic Resonance Study of Molecular Motion in Cubic (NH4)2SiF6
Authors: Blinc R. , Lahajnar G.
Published: January 2005

Proton, fluorine, and deuteron magnetic resonance absorption line shapes, as well as 1H and 19F spin—lattice relaxation times, have been measured in polycrystalline cubic (NH4)2SiF6 and (ND4)2SiF6 from −170° to +100°C. The results demonstrate that the threefold proton disorder in the NH4 groups is indeed dynamic and not static, and suggest the following mode of reorientation: The NH4 tetrahedron is first excited from the ground torsional—vibrational state to nearly continuous levels above the potential barrier, and after a short interval of nearly free rotation again drops to one of the three possible equilibrium orientations in the ground state. On the average, each proton spends the same amount of time in each of the 12 equilibrium sites. Large-amplitude rotational oscilations in the ground state are also consistent with the experimental data. The existence of a 19F linewidth transition, as well as spin—lattice relaxation data, demonstrate the onset of hindered rotation of the SiF6 ions above room temperature.
Far-Infrared Matrix and Solution Spectra and Solid-State Vibrational Spectra of Niobiumpentachloride
Authors: Werder R. D. , Frey R. A. , Günthard Hs. H.
Published: January 2005

Far-infrared spectra of niobiumpentachloride in the solid state, in several organic solvents, and in matrices of nitrogen (5°K) and cyclohexane (77°K) have been measured between 650 and 40 cm−1. Furthermore the Raman spectrum of single-crystal NbCl5 has been studied. Assignments for both the monomer and the dimer molecule vibrational spectra are given, based on observed spectra and normal-coordinate analyses. Explanation is presented for apparent coincidences observed in vibrational spectra of the solid. Thermodynamic functions of the monomeric NbCl5 are calculated from the vibrational spectra.
Paramagnetic Resonance Study of Liquids during Photolysis. V. Acid Amides and an Imide
Authors: Livingston Ralph , Zeldes Henry
Published: January 2005

Paramagnetic resonance spectra of free radicals formed by abstracting hydrogen from simple and N-methyl substituted formamides and acetamides and from succinimide have been studied. The hydrogen abstraction was brought about by ultraviolet irradiation of a solution of the amide containing either hydrogen peroxide or acetone. Deuterium substitution showed that the hydrogen bonded to carbon is abstracted from formamide resulting in a ``non-π'' radical. A methyl hydrogen is abstracted from N-methylformamide and from N,N-dimethylformamide. The former gives a single radical while the latter gives a pair of rotational isomers. These results are discussed in relation to early NMR studies. A methyl hydrogen is abstracted from acetamide. A relaxation-time measurement on acetamide indicated that linewidths are limited by the thermal relaxation time which is consistent with a number of observations for other radicals that are discussed. The hydrogen abstracted from N-methylacetamide appears to be from the N-methyl group, and a hydrogen bonded to carbon is abstracted from succinimide. Hyperfine couplings and g values are given for all of the above radicals. N,N-dimethylacetamide gives a mixture of radicals which are probably rotational isomers.
Microwave Spectrum, Molecular Structure, and Dipole Moment of Cyclic H2B2O3
Authors: Brooks W. V. F. , Costain C. C. , Porter R. F.
Published: January 2005

The molecular structure of H2B2O3(g) has been determined from its microwave spectrum. Six isotopic species, the normal H211B2O3, H211B10BO3, HD11B2O3, D211B2O3, and the two monosubstituted 18O species were studied. The molecule has C2v symmetry, with the boron and oxygen atoms forming a five-membered ring[Complex chemical formula]. The inertial defect lies in the range Δ = 0.0746±0.0025 u·Å2 for all isotopic species, and is consistent with a strictly planar structure. The rs bond lengths determined are: rs(B–H) = 1.182±0.003 Å, rs(BOapex) = 1.380±0.003 Å, rs(BObase) = 1.365±0.004 Å and rs(OO) = 1.470±0.002 Å. The angles are ≰BOB = 104°0′, ≰OBO = 113°3′, ≰BOO = 104°57′, and ≰HBOapex = 126°16′, with uncertainties of ±15′. The dipole moment was determined to be μ = 0.95±0.01 D.
Thermal Activation Energy of Organic Photoconducting Dyes
Authors: Petruzzella N. , Takeda S. , Nelson R. C.
Published: January 2005

The thermal activation energy of steady-state photoconductivity has been measured for solid dye films at constant illuminance. For those cases where energy-level data were available the activation energy was equal to the energy difference between the conductive state and the optically excited state. For these dyes it can be shown that the observed effect of temperature is on the quantum yield, and the energy difference between the conductive and the excited state is an activation energy for charge carrier production. These data support a localized model where charge carrier separation is a combined optical and thermal process involving electron tunneling of intermolecular boundaries.
Asymptotic Behavior for the Particle Distribution Functions of Simple Fluids near the Critical Point. II
Authors: Choy Teresa Ree
Published: January 2005

The main purpose of this paper is to investigate the asymptotic behavior of the reduced probability density, ρp+q+s ({p}, {q}, {s}), of p+q+s molecules when the molecules within each of the three subsets {p}, {q}, and {s}, are close together but there are large separations between the sets of p, q, and s particles. The interest is in the case where p, q, and s are unity or two. One may use the asymptotic long-range correlation function to understand the critical singularity of the thermodynamic quantities at the critical point.
Vibrations and Thermodynamic Properties of Hexasulfur
Authors: Berkowitz Joseph , Chupka W. A. , Bromels Edward , Belford R. Linn
Published: January 2005

Infrared and Raman spectra of Engel's sulfur S6, including complete polarization data for solutions of S6, provide assignments for the fundamental modes. Force fields that have been successful for S8 provide good agreement with the S6 spectra. A force model previously used for S8 is shown to be incorrect. Thermodynamic properties (HT°—H0°, FT°—H0°, ST°—S0°) for gaseous S6 are tabulated from 100° to 3000°K. The spectroscopic values S400° (92.8 eu) and S298° (84.6 eu) are in excellent agreement with those derived from thermodynamic measurements.