bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption and Ionization Coefficients of Ethylene Oxide
Authors: Lowrey Austin , Watanabe K.
Published: January 2005

Total absorption coefficients of ethylene oxide vapor were obtained in the region from 1050 to 1850 A by a photoelectric method, and photoionization yields were measured in the region from 1050 to 1190 A. A reassignment of the absorption bands in the region from 1180 to 1480 A yielded a Rydberg series which converged to 10.565 ev, a value in agreement with the ionization potential obtained by photoionization measurements. A second Rydberg series was found to converge to a vibrationally excited ionic ground state.
Stress-Enhanced Diffusion in Glass. I. Glass under Tension and Compression
Authors: McAfee Kenneth B.
Published: January 2005

This paper describes a new technique for the determination of diffusion constants of gases in gas-solid systems. The method demands a careful analysis of the transient quantity of gas flowing after the gas pressure at the boundary is discontinuously changed. The exact quantity of gas flowing is recorded by a mass spectrometer. The method was used to study the effect of high tensile stress upon the diffusion constant of helium and other gases in glass.

The diffusion constant of helium was found to be a true constant with dilation of the glass until the stress became about one-half the breaking stress of the glass. Beyond this point the diffusion constant increased, and under very high stress was a factor of ten larger than its original value. No apparent change was produced in the glass, and reduced stress gave the same diffusion constant as previously, indicating reversibility of the effect with stress. It was further determined that equal and even larger compressional stresses on the same glass specimen had little or no effect upon the diffusion constant. The effect of shear stress upon the diffusion constant is dealt with in the following paper.

The magnitude of the observed increase in diffusion constant is larger by a considerable factor than can be explained by a straight-forward extension of prevalent theories of diffusion in glass. If it is assumed that the glass sample dilates on an atomic scale, i.e., each atom being isotropically displaced by the stress, then calculations show that the diffusion constant should not be strongly increased under stress. Observation of the large increase then points toward the opening of flaws or voids within the glass.

Diffusion of hydrogen, heavy water, oxygen, and nitrogen is discussed and upper limits for diffusion of the latter three under high stress are set.
Free Energy of a Nonuniform System. I. Interfacial Free Energy
Authors: Cahn John W. , Hilliard John E.
Published: January 2005

It is shown that the free energy of a volume V of an isotropic system of nonuniform composition or density is given by : NV∫V [f0(c)+κ(▿c)2]dV, where NV is the number of molecules per unit volume, ▿c the composition or density gradient, f0 the free energy per molecule of a homogeneous system, and κ a parameter which, in general, may be dependent on c and temperature, but for a regular solution is a constant which can be evaluated. This expression is used to determine the properties of a flat interface between two coexisting phases. In particular, we find that the thickness of the interface increases with increasing temperature and becomes infinite at the critical temperature Tc, and that at a temperature T just below Tc the interfacial free energy σ is proportional to (Tc−T)32.

The predicted interfacial free energy and its temperature dependence are found to be in agreement with existing experimental data. The possibility of using optical measurements of the interface thickness to provide an additional check of our treatment is briefly discussed.
Heat Capacity of Sodium Tungsten Bronzes from 1.8 to 4.2°K
Authors: Vest R. W. , Griffel M. , Smith J. F.
Published: January 2005

The heat capacity of sodium tungsten bronze (NaxWO3) has been measured over the temperature range 1.8–4.2°K for various concentrations of sodium. An approximation to the density of states curve for the conduction band was obtained from the experimental data. This may be correlated with the previously described maximum in the electrical conductivity. It was found that the lattice contribution to the heat capacity was appreciably affected by the thermal history of the sample while the electronic contribution was relatively unaffected.
Effect of Exchange Interaction on the Magnetic and Thermal Properties of Copper Salts and Copper Coordination Compounds
Authors: Eisenstein J. C.
Published: January 2005

This paper has two purposes. The first is to derive general formulas for the specific heat and the susceptibility of a compound in which there are two magnetically inequivalent ions with effective spin ½ in each unit cell. Dipole-dipole and anisotropic exchange interactions are taken into account in the derivations. The second purpose is to explore in a rather tentative way the possibility of applying the theory to a compound in which the magnetic ions are strongly coordinated to the surrounding anions. The compound selected for detailed study is copper tetrammine sulfate monohydrate. Experimental data on this compound are neither as extensive nor as accurate as one might wish, and the theory contains a large number of adjustable parameters. Consequently it is impossible to make sharp judgments about the values of the parameters. It is concluded, however, that exchange interactions have important effects on the magnetic and thermal properties of copper tetrammine sulfate. Other substances to which the theory might be applied are mentioned.
Lattice Dynamics of Hexagonal Close-Packed Metals. II. Frequency Spectrum
Authors: Garland C. W. , Slutsky L. J.
Published: January 2005

The frequency distribution spectrum of the normal modes of vibration for a hexagonal close-packed metal has been approximated by a root sampling technique applied to a central force model of the lattice. The calculation is made for magnesium with force constants obtained from the low temperature elastic constants. The calculated specific heat of magnesium from 0°K to 100°K is in quite good agreement with experiment. Other hexagonal metals are considered in terms of a reduced plot of θ (the equivalent Debye temperature) versus temperature.
Theory of Separated Electron Pairs
Authors: Parks Joe M. , Parr Robert G.
Published: January 2005

Electron pairs in a molecule are said to be separated if (i) the molecular electronic wave function is accurately expressible as an antisymmetrized product of individual pair wave functions, and (ii) the individual pair functions are mutually exclusive in the sense that if all pair functions are linearily expressed in terms of Slater determinants built from some orthogonal one-electron spin orbitals, no spin orbital enters the description of more than one pair function. It is shown that the electronic energy of a system of separated electron pairs may be written in a particularly simple form, and the problem of determining the best separated electron-pair description of a particular molecule is discussed.

The best orbital description of an electron-pair bond is defined to be the best wave function for the pair that can be built from two atomic orbitals, one on each of two atoms. Systematic adjustment of individual pair descriptions one at a time is shown to provide a rigorous yet practicable procedure for obtaining best orbital descriptions for several separated electron-pair bonds in a molecule.

The equations obtained are shown to simplify considerably when Mulliken approximations are introduced for certain electronic repulsion integrals. Under these approximations a single property of each bond is shown to dominate its effect on other bonds, the net charge transferred from one atom to the other in the bond. This charge is called the bond polarity parameter. The equations are rewritten in terms of polarity parameters, and a scheme is thereby obtained which is convenient for discussion of intrabond charge transfer effects in a molecule. Formulas are given for the terms to be added to the absolute electronegativity of an atom in a bond to correct for charge transfers in other bonds.

It is shown that the total molecular energy of a system of separated electron-pair bonds can be expressed quite rigorously as a sum of bond energies, and the approximate invariance of bond energy to molecular environment is verified.

Limitations of the assumption of separability and methods for transcending it are discussed.
Nature of the Glass Transition and the Glassy State
Authors: Gibbs Julian H. , DiMarzio Edmund A.
Published: January 2005

The thermodynamic properties of amorphous phases of linear molecular chains are obtained from statistical mechanics by means of a form of the quasi-lattice theory which allows for chain stiffness and the variation of volume with temperature. A second-order transition is predicted for these systems.

This second-order transition has all the qualitative features of the glass transition observed experimentally. It occurs at a temperature which is an increasing function of both chain stiffness and chain length and a decreasing function of free volume.

The molecular ``relaxation times'' are shown to increase rapidly as the second-order transition temperature is approached from above.

To permit quantitative application of the theory and determine the relationship between the second-order transition and the glass transition observed in ``slow'' experiments these two transitions are tentatively identified. By this means quantitative predictions are made concerning the variations of (1) glass temperature with molecular weight, (2) volume with temperature, (3) volume with molecular weight, (4) volume at the glass temperature with the glass temperature for various molecular weights of the same polymer, (5) specific heat vs temperature, and (6) glass temperature with mole fraction of low-molecular weight solvent, since extensive experimental results are available for these properties. These and other theoretical predictions are found to be in excellent agreement with the experimental results.
On Time Smoothing. A Model for Momentum Transport
Authors: Fixman Marshall
Published: January 2005

An investigation has been made of the time smoothing properties of the transport equations previously derived by the author [J. Chem. Phys. 26, 1421 (1957)]. A model is introduced, wherein momentum is transferred from one portion of a fluid medium to another via acoustical waves. This model is applied to the problem of viscous flow of a rare gas, and it is found that it is permissible and desirable to allow the time smoothing interval τ to become infinitely large. In practice this means that τ≫β—1, where β is a friction constant. The model incidentally yields a value for the viscosity coefficient in fair agreement with the Chapman-Enskog hard sphere value.
Anisotropic Color Centers in α-Quartz. II. Germanium-Doped Synthetic Quartz
Authors: Cohen Alvin J. , Smith Herbert L.
Published: January 2005

The color center at 275 mμ produced by x-irradiation in three specimens, two of Bell and one of Clevite synthetic quartz, depends on the presence of germanium impurity. It is absent in specimens free of germanium. The center is anisotropic with maximum absorption in the σ direction (electric vector perpendicular to the c axis). In the π direction (electric vector parallel to the c axis) the absorption is poorly resolved into two bands. The color center absorption is caused by an electric dipole transition. This center bleaches more rapidly than other color centers present in the specimens. This color center system is accompanied by the aluminum system which is in the 460 mμ region and by two other bands at 1900 and 2050 A. No relationships have been observed among these bands other than that they are found together in the three instances studied and the intensity increases with the energy of the given band. A question of a model for this center is discussed.
A One-Center Wave Function for the Hydrogen Molecule
Authors: Joy Hubert W. , Parr Robert G.
Published: January 2005

Slater atomic orbitals, s, p, d, etc., centered at the molecular midpoint and having variable orbital exponents and variable principal quantum numbers, are used to construct a seven-term wave function for the ground state of the hydrogen molecule of the form Ψ=C1(ssI)+C2(sIIsIII)+C3(sIVd0)+C4(sVg0)+C5(p0p0)+C6(p+1p−1)+C7(p0′f0). Values for the seven linear coefficients, the twelve orbital exponents and the twelve principal quantum numbers are determined by the variational method. The total molecular energy obtained is — 1.15883 a.u., or 31.53 ev (exptl. 31.96 ev), corresponding to a binding energy of 4.32 ev (exptl. 4.75 ev). A ten-term function of similar form is constructed which gives a binding energy of 4.34 ev.
Field Emission from Mercury Whiskers
Authors: Gomer Robert
Published: January 2005

A method for growing metal whiskers in a modified field emission tube has been developed and applied to Hg. Emission patterns from whiskers show these to be 110 oriented single crystals when grown on a tungsten substrate. Their strength, estimated from the electric field necessary for emission is ∼1010 d/cm2. An electrical method of following length based on the relation between this quantity and the surface field, has been used to elucidate whisker growth kinetics. It is found that growth is positively exponential, indicating that it occurs by diffusion of impinging atoms to the growing end, where incorporation occurs. From the length where exponential growth ceases it is possible to find a limit for the diffusion coefficient of Hg on Hg and to estimate the activation energy of the surface diffusion as ∼1.1 kcal. Elastic twisting under tensile stress is sometimes found and ascribed to the presence of screw dislocations. Possible applications of the technique are pointed out.
Structure in Ionic Solutions. II
Authors: Brady George W.
Published: January 2005

The diffraction patterns of concentrated KOH and LiCl solutions have been analyzed. The results indicate that the hydration number for the OH— ion is 6. Previous work on less concentrated KOH solutions had indicated a hydration number of 4 for the K+ ion and a substitutional entry of the cation into the water lattice. The present work agrees with these findings. The dissolution process in LiCl appears to be of a different nature, in that there is a breakdown of the water structure, probably caused by the Li+ ion. The water molecules and the hydrated Li+ ions then pack around the large Cl— ion to give an apparent hydration member for Cl— of 8–9.
Paramagnetism in Diamagnetic Molecules
Authors: Weltner William
Published: January 2005

The experimental and theoretical determinations of the Van Vleck paramagnetic contribution (χhf) to the susceptibility of diamagnetic molecules are considered. The data on the hydrogen molecule are reviewed, and the mean square orbital angular momentum is recalculated by using Newell's wave function. The H2 calculations are interpreted as indicating that the main contributions to χhf are from energy levels directly adjacent to the double ionization limit (to H2++) at 51 ev. A corresponding calculation is made for methane by using approximate wave functions and it is found that, contrary to the H2 molecule work, L2 is quite insensitive to the wave function employed. An effective excitation energy of 30 ev is derived from an experimental value of χhf obtained from rotational magnetic moment data. Similar data for CH3F are considered and explained by the inductive effect of the F atom upon the C–H bond dipole moment. Approximate rigid-charge calculations of χhf and Pascal's rule are discussed, and the higher hydrocarbons are treated by the above procedures. It is conjectured that, in general, the energy levels near the various ionization limits in a molecule are the principal contributors to χhf, and also, that relatively low effective excitation levels (order of magnitude about 50 ev) might be expected.
Transitions in Adsorbed Monolayers. II. Theoretical
Authors: Fisher B. B. , McMillan W. G.
Published: January 2005

In anticipation of the experimental comparisons to be given in Part III, the grand partition function is employed to derive the isotherm and the two-dimensional equation of state corresponding to a model of localized monolayer adsorption similar to that of Rushbrooke, in which the lateral vibrational partition function is permitted to depend on the occupation number of neighboring sites. This treatment includes the Fowler ``crude'' isotherm as a special case. As a competing theory, a parallel development is given for the van der Waals model of mobile adsorption. Equations are presented for the critical parameters, and for the determination of the coexistence curves for these models. Finally, graphical comparisons are made which demonstrate the experimental distinguishability of the three theories on plots which rectilinearize one at a time.
Microwave Spectra of Molecules Exhibiting Internal Rotation. III. Trimethylamine
Authors: Lide David R. , Mann D. E.
Published: January 2005

The first two rotational transitions of trimethylamine have been studied. The spectrum of the ground vibrational state follows a symmetric-rotor pattern with the following constants: B0=8720.86 Mc,  DJ=5 kc,  eqQ(N14)=−5.47 Mc,  μ=0.612 D. If a reasonable structure is assumed for the CH3 groups, the framework structure is found to be: rCN=1.472 A, ≤CNC=108.7°. The satellite lines which surround each ground-state transition have been assigned to excited vibrational states. Relative intensity measurements on these satellites lead to frequencies of 263 cm—1 and 290 cm—1 for the torsional modes of species A2 and E, respectively. These frequencies are interpreted in terms of a simplified model for the torsional motions of the methyl groups. The implications of the results are discussed.
Proton Magnetic Resonance Chemical Shift of Free (Gaseous) and Associated (Liquid) Hydride Molecules
Authors: Schneider W. G. , Bernstein H. J. , Pople J. A.
Published: January 2005

In order to study the factors giving rise to proton resonance chemical shifts of free molecules, as well as the association shifts due to hydrogen bonding, proton resonance measurements were carried out for a variety of simple hydride molecules in both the liquid and gaseous states. It is found that the proton shifts in the gaseous state can be interpreted in terms of the combined effect of the electronegativity and magnetic anisotropy of the atom to which the proton is bonded. The proton signals measured in the liquid state near the melting point, which correspond to maximum association, show large shifts to lower magnetic field relative to the corresponding gas signals. It is suggested that the association, or hydrogen bond shifts, in a system Y ——— H — X can be interpreted largely in terms of the reduction of the diamagnetic circulation in the H — X bond by the electrostatic field of the Y donor. Further possible contributions in certain anomalous cases are also considered.
Higher Approximations for the Transport Properties of Binary Gas Mixtures. III. Isotopic Thermal Diffusion
Authors: Saxena S. C. , Mason E. A.
Published: January 2005

Tables of the reduced isotopic thermal diffusion factor as a function of a reduced temperature are given for the exp-six potential with potential parameter α=12, 13, 14, 15, and for the Lennard-Jones (n—6) potential with potential parameter n=12, ∞. These tables are based on recently derived higher approximations and are intended to supersede previous tabulations, which are of lower accuracy.
Stoichiometry, Spectra, and Mechanism of Light Emission for Diborane-Nitric Oxide Explosions
Authors: Roth Walter
Published: January 2005

Analysis of products, spectra, and peak light output measurements of spark ignited mixtures of B2H6 and NO indicate that NO probably reacts with B2H6 much more rapidly than with H2 and that thermal decomposition of NO is extensive. This leads to the prediction of multiple burning zones for B2H6–NO flames. Emission of a continuum in the visible and ultraviolet is ascribed to formation of electronically excited NO2 and some reactions probably involved in the mechanism are discussed.
Second-Order Sum Rule for the Vibrations of Isotopic Molecules and the Second Rule of the Mean
Authors: Bigeleisen Jacob
Published: January 2005

A second-order sum rule for the vibrational frequencies of isotopic molecules is derived. The rule relates the second power of the λ's, Σλi2 and Σi≠j λiλj, for isotopic molecules of the type X′Yz—rYr′ and XYz—rYr′ with the second power of the λ's for the symmetrical molecules X′Yz′, XYz′, X′Yz, and XYz. Special consideration is given to the case where X′ and X are in fact Y′ and Y in positions structurally equivalent to the z Y atoms in XYz. In the latter case, if z is greater than 2, the rule may involve isotopic isomers. Just as in the case of the first-order sum rule, the second-order rule can be applied separately to the individual symmetry classes common to all of the molecules.

It is shown that the second-order sum rules for a homologous series of isotopic molecules can be found easily by a simple tabulation of the interactions between the equivalent isotopic atoms. Interaction tables are given for the deutero-ethylenes and the deutero-benzenes.

The second-order sum rule is used to derive the second rule of the mean for isotopic exchange equilibria. Examples of the latter are given involving the carbon dioxide, ethylene, and benzene molecules.
Studies in Nonequilibrium Rate Processes. III. The Vibrational Relaxation of a System of Anharmonic Oscillators
Authors: Bazley Norman W. , Montroll Elliot W. , Rubin Robert J. , Shuler Kurt E.
Published: January 2005

The previous work on vibrational relaxation of a system of harmonic oscillators has been extended to a system of anharmonic (Morse) oscillators. Numerical solutions of the relevant relaxation equations have been obtained on the ILLIAC (University of Illinois electronic digital computer) for some particular cases of initial δ-function and Boltzmann distributions. The results of these calculations show that the deviations of the fractional level population from the harmonic oscillator values are very small, being of the order of the anharmonicity in the case of relaxation of the initial Boltzmann distribution, and about five times the anharmonicity for the relaxation of the δ-function distribution. A general analytical perturbation procedure for the solution of the relaxation equations has been outlined and analytical solutions for several special cases are discussed briefly.
Characteristic Frequencies of Trimethylborane
Authors: Lehmann Walter J. , Wilson Charles O. , Shapiro I.
Published: January 2005

Contrary to previously published values, the characteristic B–C asymmetric stretching mode in trialkylboranes is assigned to the 1116 to 1150 cm—1 range. The basis for the assignment of the various characteristic bond vibrations is the comparison of the infrared spectrum of trimethylborane-b10 with the infrared and Raman spectra of isotopically normal trimethylborane. The new values lead to better consistency with spectra of other trialkylboranes and alkyldiboranes.
Chain Stiffness and the Lattice Theory of Polymer Phases
Authors: DiMarzio E. A. , Gibbs J. H.
Published: January 2005

General formulas for the thermodynamic properties of amorphous polymer phases are obtained from statistical mechanics, with the aid of the lattice model, in a manner which avoids the use of restrictive assumptions concerning the nature of the individual polymer chains.

Certain results, such as prediction of a second-order transition for systems of semiflexible chains and the Flory-Huggins formula for the entropy of mixing with monomeric solvent, are thus shown to be independent of the precise nature of the model assumed for the polymer chains.

More complete information may be obtained by application of the general formulas to models descriptive of the molecular chains in question. As an example, the results of Flory for semiflexible linear chains whose stiffness arises exclusively from intramolecular nearest neighbors are obtained as a special case. (The conventional thermodynamic properties of polydisperse systems of chains of this type are shown to depend on the number average molecular weight.)
Vibrational Spectra of BBr3 and BI3
Authors: Wentink Tunis , Tiensuu Victor H.
Published: January 2005

The preparation and handling of high purity boron tribromide (BBr3) and boron triiodide (BI3) are described. The infrared absorption spectra of BBr3 in the gas, liquid, and CS2-solution phases and of BI3 in the gas, CS2-solution, and solid phases at room temperature are presented and analyzed. The observed BI3 spectrum is consistent with the expected planar configuration. The hitherto unpublished fundamental vibrational frequencies for BI3 are used along with those for BF3, BCl3, and BBr3 in a uniform force constant calculation based on a modified valence force potential. The fundamental frequencies for these four molecules should prove useful in testing various potential functions and the force constants should be valuable in predicting the vibrational fundamental frequencies in molecules such as BClI2 and BBr2I. The bond stretching force constant for the boron-iodine bond is 1.95×105 dynes/cm. The boron-iodine distance in BI3 is discussed and a tentative value of 2.10 A is proposed.
Theory of Solutions and the Reaction Kinetics in Nucleophilic Substitution
Authors: Mueller C. R.
Published: January 2005

The statistical mechanical theory of solutions is applied to reaction kinetics and the effect on reaction order is calculated. It is found that the rate constant is multiplied by an exponential function of the concentration of addend, solvent, product, or reactant. The theory is then applied to data obtained by Ingold and others from studies of nucleophilic substitution on saturated carbon atoms. The exponential dependence predicted by theory is observed.
Vibrational Intensities. IX. C2F6: Extension and Revision
Authors: Mills I. M. , Person W. B. , Scherer J. R. , Crawford Bryce
Published: January 2005

The intensity of the low fundamental of C2F6 at 219 cm—1 was measured using a CsI prism. This completed earlier studies on the other fundamentals, and permits extension and revision of the interpretation. Effective bond moments are compared with those of other fluorocarbons.
Restricted Rotation Parameters from the Dipole Moments of α,ω-Dibromoparaffins
Authors: Hayman H. J. G. , Eliezer I.
Published: January 2005

The theory of hindered rotation previously used for calculating the mean square length of polymer molecules has been combined with the Smith, Ree, Magee, and Eyring theory of the inductive effect to obtain a two-parameter expression for the dipole moment of α,ω-dibromoparaffins. The values which must be assigned to these parameters to give agreement with experiment indicate an intermediate degree of freedom of internal rotation in these molecules.
Degree of Advancement in Reactive Gas Mixtures
Authors: Potter Robert L.
Published: January 2005

The degree of advancement in reactive gas mixtures is discussed and it is shown how derivatives of these quantities with respect to temperature and pressure can be obtained in terms of the state variables at the given state point. It is shown how such derivatives can be used in hydrodynamic problems such as computing the shifting equilibrium sound velocity.
Spectral Comparison of Polyenes, Cumulenes, and Polyynes
Authors: Krauch Helmut
Published: January 2005

If a double bond is introduced between two double bonds of a conjugated polyene to form a cumulene the λ maximum shifts by 34 mμ to longer wavelength. The conjugation is much smaller in polyacetylenes than in polyenes. The formulation of a cumulene structure for the ground state of long polyacetylenes seems to be incorrect.
Liquid Pair Distribution
Authors: Cole G. H. A.
Published: January 2005

A second-order differential equation is derived which has for its solution the molecular pair distribution for a classical condensed system of particles. When applied to spherical particles interacting with central forces the equation becomes particularly simple and its solution procedure should prove more amenable than that for the equivalent integro-differential equations used by previous authors. This simpler situation will greatly facilitate the consideration of a range of thermodynamic conditions or different systems. The method should in addition lead to greater accuracy in the determination of the pair distribution.
Relaxation of the String Oscillator
Authors: Widom B.
Published: January 2005

As was pointed out by Herzfeld, a single collision between an oscillator and an impinging particle usually consists of a multiplicity of impacts. If the oscillator is a particle on an inextensible string (mechanically equivalent to a particle in a box), and if it interacts impulsively with particles of identical mass incident along its line of oscillation, then each collision either consists of a single impact, in which case momentum is exchanged, or of a double impact, in which case there is no net momentum exchange. The transition probability is calculated exactly, and the resulting integro-differential equation for the oscillator distribution function is solved explicitly. It is shown that the approach to equilibrium is not in general exponential in the time, even in its last stages, but that it may be made so with a special initial distribution. The effect of impact multiplicity on the time of relaxation is discussed.
Reactions of Alkoxy Radicals. IV. Photolysis of Methyl-d3 Acetate at High Temperatures
Authors: Wijnen M. H. J.
Published: January 2005

The photolysis of CH3COOCD3 has been investigated over the temperature range 145 to 350°C at varying initial pressures and light intensities.

The following reactions have been studied in detail: CD3O+CH3→CH3D+CD2O,CD3O+CH3→CH3OCD3,CD3O+CH3COOCD3→CD3OH+CH2COOCD3,CH3+CH3COOCD3→CH4+CH2COOCD3.A value of about 1.4 is obtained for k7/k6. The results indicate that the activation energy of reaction (7) is zero kcal. A value of 10±0.5 kcal is obtained for E12, while the data indicate a value of approximately 5 kcal for E16.
Out-of-Plane Vibrations of a Conjugated Hydrocarbon : trans-Butadiene
Authors: Anno Tosinobu
Published: January 2005

A method of obtaining some of the out-of-plane force constants in conjugated hydrocarbons from bond orders and of borrowing the other kinds of these constants from similar molecules is described. The method includes the assumptions that the force constant of torsion around the CC bond is proportional to the product of the π bond order and the overlap integral of the carbon 2pπ atomic orbital and that the interaction constant between wagging motion of a CH group and a torsion around a CC bond to which the CH group is attached is proportional to the diagonal constant of the torsion. The validity of these assumptions is discussed. As an application of the method the nonplanar frequencies of trans-butadiene are calculated and compared with experimental values. The results are found to be encouraging.
Adiabatic Rate Processes at Electrodes. I. Energy-Charge Relationships
Authors: Hush N. S.
Published: January 2005

The distinction between adiabatic and nonadiabatic reaction mechanisms at an electrode/solution interface is emphasized; in general, only adiabatic or near-adiabatic paths are important in thermally activated reactions. The role of the dielectric in determining the course of such reactions is discussed. A general interpretation of the transfer coefficient and an account of the activation process in simple systems are given in terms of the distribution of electron charge density in the transition state; these are shown to be in good accord with experiment. The conventional approach to these problems, in which an approximate potential-energy path for the reaction is calculated from intersecting potential-energy curves for the initial and final states of the system, is criticized, and an alternative representation in terms of charge variation is proposed.
Formal Hückel Theory
Authors: Simpson William T.
Published: January 2005

Using the nondiagonal potential energy operator Uν=− ∑ i(1/rνi)+ ∑ i[open phi]i(xν′)[open phi]i(xν)Xνi−(1/2) ∑ i≠j[open phi]i(xν′)[open phi]j(xν)(Xνi+Xνj)(Δν)ij,where Xνi= ∫ [open phi]i(xν) ∑ k≠i(1/rνk)[open phi]i(xν)dτand (Δν)ij= ∫ [open phi]i(xν)[open phi]j(xν)dτ(and the [open phi]'s are atomic orbitals) the Hückel theory may be formally stated. The formal theory is consonant with the idea of the Fermi hole. Since it is presented as the zeroth-order part of a perturbation theoretical treatment of the true Hamiltonian the perturbation is explicitly known by difference.
Electronic Structure of Some Diatomic Hydrides
Authors: Krauss Morris
Published: January 2005

The self-consistent field molecular orbital (SCF-MO) method is applied to the calculation of the ground states of the CH, CH+, NH, OH, and FH molecules. Results are reported for the ionization potentials, excitation energies, binding energies, and dipole moments. The relative behavior of the bonding in these molecules is exhibited by an electron distribution analysis and the importance of s-p promotion in a single configuration description of these molecules is emphasized.
Raman Spectroscopy in Liquid Ammonia Solutions. Vibrational Frequencies and Force Constants for Isotopic Species of the Borohydride Ion Having Tetrahedral Symmetry
Authors: Emery Allan R. , Taylor Robert C.
Published: January 2005

All fundamentals of the ions 11BH4—, 11BD4—, 10BH4—, and 10BD4— have been observed in the Raman spectra of some alkali metal salts dissolved in liquid NH3 or ND3 at —50°C. A complete assignment of all observed frequencies has been made and force constants have been calculated by the FG method of Wilson.
Viscous Flow of Liquids at Constant Volume and Constant Pressure
Authors: MacKenzie J. D.
Published: January 2005

The energy of activation for viscous flow at constant volume, Ev, is dependent on the volume of a liquid. For normal liquids at elevated temperatures, Ev is only a small fraction of the value of the activation energy at constant pressure, Ep. However, for associated liquids, on account of the presence of hydrogen bonds, Ev is almost equivalent to Ep. It is suggested that in highly associated liquids like liquid silica and some molten glasses where flow necessitates the rupture of bonds of even greater energy, the difference between Ev and Ep should be negligible.
Equation of State for Water at High Pressure
Authors: Knopoff L.
Published: January 2005

An equation of state for water at high pressures is derived by assuming water to be an amorphous mixture of Thomas-Fermi-Dirac oxygen atoms and Wigner-Huntington hydrogen atoms, the mixture having the correct proportion of atomic constituents. Comparison is made with more intricate models in which interaction of the fields among neighbors is assumed.
Correlation of Molecular Constants. II. Relation between Force Constant and Equilibrium Internuclear Distance
Authors: Varshni Yatendra Pal
Published: January 2005

A new relation between force constant and equilibrium internuclear distance has been suggested: ke(re−d)2=A,where d and A are constants for each molecular group. The relation has been examined for a number of molecular groups and found to be satisfactory.
Free Radical Statistics
Authors: Jackson Julius L. , Montroll Elliott W.
Published: January 2005

On the basis of a simplified statistical model, average concentrations of trapped free radicals condensed from a gaseous mixture are calculated. The trapped free radical concentration is obtained as a function of the free radical concentration in the gas and of the number of nearest neighbors in the solid. The mathematical problem presented by the model is solved rigorously in the one-dimensional case (two nearest neighbors) and approximately for arbitrary numbers of nearest neighbors. Typical calculated percentages of trapped free radicals range from 14% for a simple cubic lattice to 10% for a face-centered cubic lattice, when the solid is condensed from a completely dissociated gaseous mixture.
Determination of the Electronic Conductivity in Silver Halides by Means of Polarization Measurements
Authors: Ilschner Bernhard
Published: January 2005

The current passing through a cell, silver/silver halide/graphite, has been measured as a function of applied potential in the temperature range between 200 and 370°C, for potentials less than 0.5 volt. Under these conditions, the current for steady-state conditions is mainly electronic. Definite results were obtained for AgBr and AgI, but not for AgCl because of sluggish approach to steady-state conditions. From an analysis of the current-potential curves it is concluded that excess electron conduction prevails in AgBr, but hole conduction in AgI.
Theory of Detonations. I. Irreversible Unimolecular Reaction
Authors: Hirschfelder Joseph O. , Curtiss Charles F.
Published: January 2005

The composition, temperature, and pressure as functions of distance in a steady-state, plane gaseous detonation wave are studied. The effects of the coefficients of viscosity, diffusion, and thermal conductivity are included. The basic equations are set up for a gas in which the irreversible unimolecular reaction A→B takes place with the release of energy. The topological nature of the solutions is discussed and some detailed numerical solutions are given. The numerical calculations (obtained by a point-by-point integration of the detonation equations) indicate a strong probability that there is a highest ambient pressure above which a steady-state detonation cannot take place, and indicate a possibility that there is an ambient pressure below which a detonation cannot occur. In the examples considered, there is strong coupling between the reaction zone and the shock zone so that the solutions never come close to the von Neumann ``spike.'' If the Mach number is greater than unity, the solutions have an entirely different nature and exist for only a single ambient pressure rather than for a range of pressures. However, from hydrodynamical considerations, a detonation wave initiated from either a point or a fixed wall can become equivalent to the steady-state solutions only if the Mach number is greater than or equal to unity.
Theory of Detonations. II. Reversible Unimolecular Reaction
Authors: Linder B. , Curtiss C. F. , Hirschfelder J. O.
Published: January 2005

The effect of a back reaction on the chemical and thermal profiles in a steady-state plane gaseous detonation wave supported by an exothermic unimolecular reaction is considered. Just as in the irreversible case, considered in the previous paper, the character of the solutions of the detonation equations change when the Mach number becomes greater than unity. However, in agreement with the conclusions of Wood and Kirkwood, for the reversible reaction, this critical Mach number has the value of unity only when it is defined in terms of the equilibrium velocity of sound.
Streaming Dichroism in Polymer Solutions: The Calculation of Results
Authors: Bird George R.
Published: January 2005

Streaming dichroism of the infrared absorption bands of polymer solutions has been observed by flowing the solutions through a modified infrared cell. The calculation of orientation and dichroism as a function of streaming gradient resembles the calculation for streaming birefringence, but is not identical. This calculation is performed for ellipsoidal particles, and the results tabulated for the special case of rods with high axial ratio.
Paramagnetic Species Produced by γ Irradiation of Organic Compounds
Authors: Smaller B. , Matheson M. S.
Published: January 2005

Some alkanes, olefins, alcohols, ethers, and a few other organic compounds have been irradiated with Co60 γ rays at low temperatures. The frozen irradiated samples have been examined for paramagnetic resonance, and the observed spectra in several cases have been identified with specific radicals. The methyl, ethyl, and allyl radicals are among those identified. The results in each case have been considered in relation to the present knowledge of the radiation chemistry of the compound. The mode of radical formation in many cases appears to be quite specific. Thus, in normal alkanes the major process for radical formation is by loss of a specific H atom. Hyperconjugation is used to interpret the resonance spectra.
Spin Density Matrices for Paramagnetic Molecules
Authors: McConnell Harden M.
Published: January 2005

The density of electron-spin angular momentum (erg-sec/cm3) at a point x, y, z in a paramagnetic molecule is ℏ Szρ(x, y, z), where Sz is the z component of the total electron spin angular momentum in units of ℏ. If the exact wave function for the molecule Ψ is built up from one-electron basis functions ψi, then the normalized spin density function ρ(x, y, z) can be expressed in terms of the ψi and the spin density matrix ρijρ(x,y,z)= ∑ ijρijψj*ψi.If the ψi are molecular orbitals, then ρij is the molecular orbital spin density matrix; if the ψi are atomic orbitals, then ρij is an atomic orbital spin density matrix. The equation of conservation of spin is Tr(Sρ)=1 where S is the non-orthogonality matrix, Sij=〈ψi|ψj〉.

The elements of the spin density matrices are sensitive to overlap and electron correlation effects. This is illustrated by calculations of the spin density matrices of the ethylene positive ion radical, and of the allyl radical. The spin density matrix for the latter molecule is calculated using (a) the simple molecular orbital approximation, (b) the simple valence bond approximation, and (c) the complete π-electron interaction configurational treatment given by Chalvet and Daudel.

It is shown that the general connection between σ-proton hyperfine splittings aN and the π-electron atomic orbital spin density matrix ρNN′, involves a (hyperfine interaction)-(exchange interaction) matrix QN′N″″N such that aN=Tr(QNρ).However, for practical calculations, observed hyperfine splittings may be used to estimate the diagonal elements of the spin density matrix, aN≈QρNN,where Q has the semiempirical value of —63 Mc or —23 gauss
An Electrostatic Model for Prediction of Shapes of Covalent Molecules and Ions
Authors: Searcy Alan W.
Published: January 2005

For covalently bonded molecules and ions containing a central atom and one or more lone electron pairs, oxygen atoms, or sulfur atoms, bond angles can be predicted to within a few degrees by means of an electrostatic model. The parameters required are an electrostatic repulsion number (ERN) for each substituent atom. These ERN's (except for that of fluorine) depend only on the chemical family of the substituent atom and on the period of the central atom. The model emphasizes the strong influence of lone pair electrons on molecular shapes, dipole moments, and other chemical and physical properties.
Electronic Structure of LiH. III. The Knipp Wave Function
Authors: Ormand Fred T. , Matsen F. A.
Published: January 2005

The electronic energy and dipole moment of lithium hydride have been computed from a 10-term wave function which used orbitals of the James and Coolidge type (excluding terms containing interelectronic distances) for the valence electrons. The best energy obtained was —217.133 ev. The dipole moment was computed to be —5.574D (hydrogen negative), significantly close to the —6.04D obtained previously from a 6 structure valence-bond calculation based on Slater orbitals.
Bond Rupture of HBr80m Following Nuclear Isomeric Transition
Authors: Luebbe Ray H. , Willard John E.
Published: January 2005

When the Br80m in HBr80m undergoes isomeric transition the HBr80 bond is broken in 93% or more of the events rather than only 75% as indicated by earlier work. In gaseous mixtures of HBr, CH3Br, and 1,2-dibromethylene containing either HBr80m or CH3Br80m, the distribution of the Br80 daughter between organic and inorganic combination is dependent upon the HBr/C2H2Br2 ratio, indicating that C2H2Br2 does not compete as effectively with HBr for the Br80 atoms as formerly thought.
On the Theorem of Corresponding States and Its Application to Mixtures
Authors: Rice Stuart A.
Published: January 2005

The theorem of corresponding states as applied to mixtures is studied. It is shown that for a solution in which random mixing obtains, it is possible to define reduced temperatures and volumes for each cluster in the cell cluster expansion of the partition function. The relationship of this result to the corresponding states theories of Brown and Kirkwood et al. is considered. In addition the additivity hypothesis of Prigogine is examined and the comments of Salsburg discussed.
Ligand Field Theory of Ni(II) Complexes. II. Electronic Spectra and Structure of Some Paramagnetic Chelates
Authors: Maki Gilda
Published: January 2005

An assignment of the observed absorption spectra is made for each of six paramagnetic Ni(II) chelates studied, based on the energy levels calculated for the Ni(II) ion from an electrostatic model of the complex. The best assignments, in each case, give reasonably good qualitative and quantitative agreement, explaining the number and relative intensities of the triplet-triplet and triplet-singlet transitions and giving maximum error of 30% when compared with the observed positions of maximum intensity. The consistency and relative significance of the values of the effective dipole moments used for the different coordinating oxygen and nitrogen atoms is demonstrated in several specific assignments. For the chelates of unknown structure and coordination, a comparison of various possible assignments enables structural predictions, while the chelates of known structures are given reasonable assignments with their appropriate configurations. The sensitivity of the assignments to the assumed structures allowed the general conclusion to be drawn that significantly better results are obtained if unequal effective dipole moments of different ligands are used, rather than one average value. For example, all six coordinated chelates with mixed ligands were given better assignments in tetragonal or trans-planar symmetry than octahedral symmetry. It is felt that this study demonstrates the scope of the electrostatic model of the complex ion and justifies its use to explain and predict properties of the complex molecule associated with the central ion.
Fluorescence Spectra, Term Assignments, and Crystal Field Splittings of Rare Earth Activated Phosphors
Authors: Keller Seymour P.
Published: January 2005

The visible fluorescent emissions, excited by 280-mμ radiation, of SrS phosphors, singly activated with rare earth ions, have been determined. These spectra are correlated with atomic term signature designations and with spectra of rare earth salt compounds. Crystal field splittings of certain energy levels are observed.
Evaluation of Quantum Yields for Polymer Crosslinking and Scission by Light
Authors: Shultz Allan R.
Published: January 2005

Elementary mathematical relations are formulated to permit calculation of quantum yields for polymer crosslinking and scission by exponentially attenuated radiations. The data required are such readily observable quantities as polymer molecular weight, solution viscosity, insolubles (gel) content, film thickness, radiation absorption coefficient, and incident surface radiation dose. The derived equations are illustrated graphically to facilitate visualization of the interplay of the various factors influencing polymer film modification by radiation.