bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibration Spectrum and Heat Capacity of a Chain Polymer Crystal
Authors: Genensky S. M. , Newell G. F. 
Published: January 2005

The Born-von Karman model for a chain polymer crystal previously studied by Stockmayer and Hecht is re-examined using only analytic approximations rather than numerical methods. The analytic approach brings out many peculiar properties of the chain polymer model that did not appear in the numerical treatment.
One branch of the frequency distribution g(v) is shown to be proportional to v2 for the smallest values of v, approximately proportional to v32 for slightly larger v, to v½ for still larger v and to v—½ in still a fourth range of small values of v. An accurate graph of g(v) is constructed for the entire range of frequencies using values of the force constants suggested by Stockmayer and Hecht. g(v) is shown to have approximate singularities of a type not anticipated by van Hove in his broad treatment of singularities for general systems. This anomalous behavior results from having strong valence forces resisting the bending of bond angles. A classification and description of various kinds of singularities that may arise for systems with strong valence forces are given in an appendix.
Electrolytic Hydrogen Evolution Kinetics and Its Relation to the Electronic and Adsorptive Properties of the Metal
Authors: Conway B. E. , Bockris J. O'M. 
Published: January 2005

A significant correlation between the logarithm of the exchange current density i0 of the electrolytic hydrogen evolution reaction and the electronic work function φ is found for one group of metals. Another group of metals probably having a different relationship is distinguished. The relationship between logi0 and φ is explained as arising from the dependence of heat of adsorption upon φ. The bond strength DMH of the adsorbed hydrogen calculated from Pauling's equation is less than the experimental value, owing to the neglect of the image potential of H at the metal, but parallels the experimental values. DMH is dependent on the work function since the parameters DMM (the metal-metal dissociation energy) and XM (the electronegativity of the metal) are statistically significant linear functions of φ. For the metals Ta, Mo, W, Cu, Ni, Fe, Rh, Pd, and Pt (at high current densities) logi0 increases as the heat of adsorption of H decreases.
The heats of adsorption of H at Hg, Cd, Pb and Tl are low compared with the values for other metals having respectively similar work functions and the distinct relation, having a different direction, between logi0 and φ for these metals is explained.
Logi0 increases linearly with increase of d character for the metals Mo, W, Cu, Ni, Fe, Pd, and Rh. The correlation coefficient is 0.62. The relation to d character arises since the d character determines the heat of adsorption of H.
The usually observed Tafel slope of 0.12 is consistent either with the rate determining reactionH3O·+e0−+M→MH+H2Oor H3O++MH+e0−→H2+M+H2O.If A is rate determining, i0 should increase with increase of the heat of adsorption of H; if B, the converse should occur. Hence, B is rate determining in acid solution for the metals, Cu, Ni, W, Mo, Ta, Fe, Pd, Rh, Pt (high current density) and A for the metals Hg, Tl, and Pb. The available stoichiometric number data support this conclusion, which implies that during steady evolution of hydrogen, a maximum coverage of the metal by adsorbed H occurs under the condition that the electrode is in contact with liquid water. A general theory of electrolytic reduction and electrode poisoning is given. A mathematical analysis of the dependence of the rate of the proton discharge reaction in terms of the heat of adsorption of H, MH bond force constants, and internuclear distance, is given.
Chemical Bond: A One-Dimensional, Square Well-Type Model
Authors: Barrow Gordon M. 
Published: January 2005

A suitable bonding atomic orbital is generated by a square well potential bounded by an infinite potential on one side and a constant finite potential on the other side. The bonding electrons of a σ bond are described in a similar double well potential. With a choice of the potential well dimensions and an electron repulsion term the electronic energy is calculated for various approximate wave functions.
For a heteronuclear bond the potential wells are given different depths. The additional energy and the ionic character are obtained. Comparison with the usual electronegativity scale and ionic character relations shows that this simple model reproduces the principal features of a σ bond.
Viscoelastic Theory of Branched and Cross-Linked Polymers
Authors: Ham Joe S. 
Published: January 2005

A model of polymer chain motions is developed which in the limit of long, flexible chains can readily be applied to branched chain and cross-linked systems. The equation governing the motion of a chain takes the form of a differential equation rather than the form of the large set of difference equations that occur in most other treatments. The present model gives essentially the same distribution of relaxation times for linear polymers as previous treatments, and it also gives the same dependence of viscosity upon branching as the theories based on the effective radius of randomly coiled chains.
In addition to this information, the theory yields the distribution of relaxation times for branched chain polymers, permitting, for example, the calculation of the energy stored in steady state shear. The relaxation time distribution of several models of a cross-linked polymer is also calculated, and the relationship of this distribution function to that of the uncross-linked materials is discussed.
On the Theory of Oxidation-Reduction Reactions Involving Electron Transfer. II. Applications to Data on the Rates of Isotopic Exchange Reactions
Authors: Marcus R. A. 
Published: January 2005

The rates of some homogeneous isotopic exchange reactions in solution are considered in the light of a recently developed quantitative theory of redox processes (Part I). The relative importance of several factors influencing the rates of these reactions is discussed. These factors include the Coulombic repulsion between the ionic reactants and the extent of solvation of the ions. Free energies and entropies of activation of various reactions are calculated from the theory without the use of any adjustable parameters. The agreement with the experimental data is considered to be satisfactory.
On the basis of the theory and of earlier experiments in heavy water an experimental method is tentatively suggested for distinguishing electron and atom transfer mechanisms. This method applies to halide-catalyzed exchange reactions of metal aquo-ions, and to other anion-catalyzed reactions of this type not involving breakable OH bonds.
On the Theory of Oxidation-Reduction Reactions Involving Electron Transfer. III. Applications to Data on the Rates of Organic Redox Reactions
Authors: Marcus R. A. 
Published: January 2005

A recently developed theory of oxidation-reduction reactions (Part I) is used to calculate the rates of organic redox reactions whose mechanism involves the transfer of an electron from one reactant to the other. The theory can be used to discuss factors affecting the rates of these reactions. These factors include a standard free energy of reaction, the Coulombic interaction of the ionic charges of the reactants, and the solvation of the charged reactants. Attention is focused on the relation between the rate of the redox step in the over-all process and the standard free energy change, ΔF0, of this step, rather than on the more usual but less fundamental one between the corresponding quantities of the over-all process itself.
An approximate method is described for applying the theory to a molecule whose charge is not located at its center. Essentially all organic molecules lie in this category.
As an example of these considerations, several typical reactions are discussed. These reactions involve the oxidation of a series of hydroquinones by ferric ions and of a series of leucoindophenols by dissolved oxygen. They are assumed to possess electron transfer, rather than atom transfer, mechanisms. Free energies and entropies of activation of the redox step are calculated using the theoretical equation. The calculated results are considered to be in reasonable agreement with the experimental data, no adjustable parameters being employed.
Theory of Radiation Chemistry. IV. Chemical Reactions in the General Track Composed of N Particles
Authors: Monchick L. , Magee J. L. , Samuel A. H. 
Published: January 2005

The chemical reactions which occur in particle tracks are diffusion-controlled. In this paper a set of partial differential equations is presented which describes the dissipation of a track composed of N particles. These equations involve functions which can be interpreted as correlation functions for the relative distribution of the particles. A superposition approximation is introduced which greatly simplifies the equations and a method for obtaining the correlation functions is presented.
As an example of application of these equations a model for the action of ionizing radiation on water is discussed. It is shown that the radiation chemistry of water is adequately described for reasonable values of the parameters of the model.
Emission Band Spectra of Nitrogen. Kaplan's First and Second Systems
Authors: Lofthus Alf , Mulliken Robert S. 
Published: January 2005

Seven bands of Kaplan's first system and eleven bands of Kaplan's second system have been photographed under high resolution. The two systems are definitely y1Π−a′1 Σ and y 1Π−w1Δ. It is very probable that they are y 1Πg−a′1Σu− and y 1Πg−w 1Δu and that the two lower states belong, along with A 3Σu+ and b′1Σu+, to the N2 configuration ··· πu3σg2πg. A clear breaking-off of the branches coming from the Π+ levels of the y 1Πg state above v′=0,J′=10 was observed. This is interpreted as an allowed predissociation by a Σg+1 state dissociating to two 2D atoms. Consequently lower limits probably close to the term values for the x, y, w, and a′ states could be determined; this locates the a′ and w states respectively probably about 2.2 and 2.7 ev above state A, in good agreement with theoretical expectations. Perturbation of the remaining Π— levels was also observed. Rotational and vibrational constants and term values of the various states are presented. The transitions a′↔a and w↔a should give rise to bands in the (mostly far) infrared.
It is noted that the constants of both the x and y states are close to those of the N2+ state ··· πu3σg2, and it is proposed that x1Σg— and y1Πg are respectively derived from the latter by the addition of an electron in a 3pπu and a σu (4pσu ?) Rydberg orbital. It is then proposed that the DΣu+3 and p′ Σu+1 states of N2, whose constants are close to those of the ground state ··· πu4σg of N2+, are derived from the latter by addition of an electron in the same σu Rydberg orbital as in the y state. The states p′ and e are the first two members of Worley's first Rydberg series.
Iodine Complexes in Inert Solvents. VI. Solvation Processes in Solutions of Oxygenated Solvents and Iodine, Bromine, or Sulfur Dioxide
Authors: de Maine P. A. D. 
Published: January 2005

A survey of recent literature on systems containing halogens or sulfur dioxide in aliphatic oxygenated solvents or inert solvents is given. It is shown that the classical concepts of solvation processes do not apply to these systems. It is concluded that the results are best understood with the new ``liquid-lattice penetration complex'' theory, if it is assumed that the stabilizing energy of the heterogeneous aggregates is provided by Mulliken's ``charge-transfer'' forces.
A new interpretation of the term ``activity coefficient'' is given. These coefficients are shown to arise from the neglect of lattice factors.
Use of Gaussian Wave Functions in Molecular Calculations
Authors: Kimball G. E. , Neumark G. F. 
Published: January 2005

Gaussian functions have been used in a simple variational approach to calculate the energy of a number of two-electron systems, namely the hydrogen molecule, the negatively charged hydrogen ion, and the (1s)2 1S, (1s) (2s) 3S, and (1s) (2p) 3P states of helium. The last two were included in order to test two different 2s and a 2p function. The error in the total energies varied from 14% to 33%, showing that these functions can give ``fairly good'' energy values. This, and some other evidence, seems to indicate that in such variational calculations the specific form of the starting wave function may not be too important.
Calculations were also carried out on one single electron system in order to further compare the two different 2s functions. Both here and in the case of the triplet helium both functions gave almost identical energies.
Effect of Pressure on the Isotope Effect in a Unimolecular Gaseous Reaction : Tritium and Carbon-13 Effects in the Isomerization of Cyclopropane
Authors: Weston Ralph E. 
Published: January 2005

As a new means of studying the effect of pressure on unimolecular gaseous reaction kinetics, the tritium isotope effect in the isomerization of cyclopropane to propylene has been measured. At a pressure of 200 mm, the ratio of rate constants for unlabeled and singly-labeled species is given by k/k′ = (0.86±0.06) exp (385±95/RT). The temperature range was 406–492°C. As the pressure decreases, the isotope effect is lowered and, within experimental error, disappears at 1 mm. Upon the addition of inert gas to cyclopropane at this pressure, the isotope effect is increased to a value corresponding to a higher pressure of reactant. The relation between these results and the calculations of N. B. Slater on the kinetics of this reaction is discussed.
The carbon-13 isotope effect was measured at 1 atmos and 492°, and was found to be k/k′=1.0072±0.0006. This may be explained on the basis of a change in either a carbon-carbon or a carbon-hydrogen bond in the transition state.
Susceptibility and Curie Point of Magnetically Dilute Crystals
Authors: Behringer Robert E. 
Published: January 2005

The Opechowski calculation of the apparent Curie point, TC, is extended to the case of magnetically dilute f.c.c. crystals. To first order in temperature the result is equivalent to a molecular field treatment. The calculation is carried to fourth order in temperature and a plot is made of TC vs p, the fractional concentration of magnetic atoms. The theoretical result is compared to some existing experimental data and values of the exchange interaction, J, are estimated.
The above calculation is found to be useful only for 0.8≤p≤1.0. For low concentrations a crude calculation is made based on clusters of magnetic atoms. To first order in temperature, a linear relationship is found between apparent Curie point and concentration.
Relationship between Relaxation Time and Viscosity for Water
Authors: Grant E. H. 
Published: January 2005

The Debye relationship connecting relaxation time, viscosity, molecular size, and absolute temperature appears to hold almost exactly in the case of water. The Debye equation was formulated on the basic assumption that each molecule can be considered as turning in a viscous continuum as it rotates in dielectric relaxation, and it is well known that this molecular picture is inapplicable to water.
It is shown that a similar relationship can be deduced directly from equations based on the hydrogen bonded structure of the liquid.
Study of the Electronic Ground State of the Ammonia Molecule
Authors: Kaplan Harvey 
Published: January 2005

The electronic structure of the ground state of the ammonia molecule has been calculated in the SCF LCAO MO approximation for two sets of internuclear separations: the experimentally observed values and a symmetric planar arrangement. The effect of limited configuration interaction on these results has also been investigated. The atomic orbitals used include 1s, 2s, and 2p nitrogen orbitals and 1s hydrogen orbitals, the nitrogen orbitals being the Hartree and Hartree solutions of the Hartree-Fock problem for the neutral nitrogen atom and the hydrogen orbitals being the standard free atom functions. All integrals were calculated using the method of Barnett and Coulson and Lundqvist and Löwdin, the only approximation involved being the mathematical one of terminating infinite series.
The significance of the results is discussed, and calculations of the binding energy, the dipole moment, and other molecular properties are compared with experiment.
Statistical Computation of Mean Dimensions of Polymer Molecules. IV
Authors: Wall F. T. , Hiller L. A. , Atchison W. F. 
Published: January 2005

In a further investigation of the nonintersecting random walk problem, two new types of random walks have been examined to determine the effect of the magnitude of the ``excluded volume'' on the limiting behavior of the ratio, 〈rn2〉n, where 〈rn2〉 is the mean square length of nonintersecting random walks of n steps. In two dimensions, 〈rn2〉/n normally diverges, but for walks in a right-left two-choice 90° lattice, for which exclusions are counted on odd steps only, the ``excluded area'' is reduced to such an extent that convergence of 〈rn2〉Av/n may occur. In three dimensions, 〈rn2〉/n may converge, but if random walks in a three-choice tetrahedral lattice are generated subject to the condition that walks cannot return to lattice points within unit distances from previously occupied sites, the ``excluded volume'' is sufficiently increased so that 〈rn2〉/n certainly diverges as n→∞.
In addition to the above, our process for selecting the random numbers used to generate random walks has been re-examined more fully and has been found to be satisfactory. We have also examined values for mean square lengths of failures which might result from backward steps. These distances agree with an empirical relationship found to hold for the other types of failures, thus providing further justification for an earlier theoretical interpretation of the nonintersecting random walk problem.
Internal Barrier of Propylene Oxide from the Microwave Spectrum. I
Authors: Swalen Jerome D. , Herschbach Dudley R. 
Published: January 2005

In order to study the effects of hindered internal rotation of a methyl group for a high barrier case, the microwave spectrum of propylene oxide has been observed. Rotational transitions have been assigned up to J=30 in the ground torsional state and to J=10 in the first excited torsional state. The structure of the molecule was partially determined by combining the rotational constants derived from the spectrum with the known structure of ethylene oxide. From Stark effect measurements, the dipole moment was determined to be 2.00±0.02 debye.
The theory of the interaction of internal rotation with over-all rotation is discussed, including the necessary extension of the theory of Wilson, Lin, and Lide for a molecule having no symmetry. Because the tunnel effect splits each torsional state into two levels, the rotational lines appear as doublets. The threefold barrier hindering internal rotation of the methyl group is fitted to the doublet separations. For the ground state, the splitting of the lines was observed only for high J rotational transitions. A barrier of 2710 cal/mole was obtained. For the first excited torsional state, the splittings are about fifty times larger, and are observable for low J transitions. These yield a barrier of 2560 cal/mole. The causes of this apparent difference in barrier height and the errors in the method are discussed.
Photoconductivity of Anthracene. III
Authors: Compton D. M. J. , Schneider W. G. , Waddington T. C. 
Published: January 2005

The photoconductivity of anthracene has been studied using three types of crystals: large scintillation crystals, crystals grown from dimethylformamide, and sublimation flakes. The existence of a true bulk conductivity as well as a surface conductivity has been demonstrated. This bulk conductivity is not affected by oxygen. The space charge found by previous workers has been shown to be located at the electrodes and to be due to poor contacts. The dependence of both the surface and the bulk photocurrent on temperature, voltage, and wavelength and intensity of light, have been studied and found to be markedly different from each other. The surface photocurrent shows a non-ohmic voltage dependence.
It is concluded that the formation of charge carriers is not a primary process of light absorption, but a secondary process, competing with fluorescence and thermal degradation of the absorbed light energy, which is free to move through the crystal in the form of excitons. A mechanism for the migration of charge carriers has been put forward to explain the main features of the photoconduction. A much higher effective carrier mobility on the surface than in the bulk of the crystal is postulated. The behavior of the surface photocurrent is interpreted in terms of the formation of carriers in the bulk, those that diffuse to the surface playing the greater part in carrying the current. The bulk current is considered as a recombination-limited photocurrent. In agreement with previous workers, it is concluded that most of the current is carried by positive holes.
Crystal and Molecular Structure of B9H15
Authors: Dickerson Richard E. , Wheatley Peter J. , Howell Peter A. , Lipscomb William N. 
Published: January 2005

With only the information that B and H alone are present, and that the melting point is —20°, the molecular structure of B9H15, a new boron hydride, has been determined from single crystals by x-ray diffraction methods. There are four molecules in the unit cell, space group P21/n, with a=11.80 A, b=6.94 A, c=11.25 A, and β=109° 9′. The boron skeleton, solved by three-dimensional Patterson and trial and error methods, and refined by least squares methods, is a fragment of the icosahedron formed by removing three connected borons not forming an equilateral triangle. Hydrogen atoms, located from three-dimensional difference maps, agree with those expected from previously known boron hydrides. The over-all agreement factor is R=Σ∥F0| — |Fc∥/Σ|F0|=0.155.
Computations on the UNIVAC Scientific 1103 Computer are described briefly, with emphasis on the use of fractional shifts of parameters in the least squares method. A least squares normalized weighted sum of squares of residuals is proposed as a better criterion of agreement than R.
Nonideality of Liquid Ortho-Parahydrogen Solutions
Authors: Friedman Harold L. 
Published: January 2005

The thermodynamic properties of liquid ortho-parahydrogen solutions are calculated from the total pressure measurements of Woolley, Scott, and Brickwedde [J. Research Natl. Bur. Standards 41, 379 (1948)] by a method which is applicable to systems in which the fugacity coefficients of the vapors are independent of composition at given T and P, and in which the liquid solution obeys the law, Gex/x(1—x) =constant.
For ortho-parahydrogen solutions at 20°K, Hex=3.07x(1—x) cal/mole and Sex=0.097x(1—x) cal/mole deg. The asymmetry of the pair-wise intermolecular potentials noted by Woolley, Scott, and Brickwedde is confirmed.
Theory of Dilute Polymer Solutions
Authors: Koyama Ryuzo 
Published: January 2005

Assuming the pearl necklace model for a chain polymer molecule in a solution, the theoretical expressions for the mean intermolecular potential and the radial distribution function of polymer molecules are derived. The methods in the theory of Born and Green, which is based on the superposition approximation, are conveniently applied to the case of solution.
The results show that the mean intermolecular potential is nearly approximated by the Gaussian function, and it depends on the molecular weight and the temperature; the radial distribution function is also dependent on the molecular weight as well as on the temperature. At critical temperature where the second virial coefficient vanishes, the mean intermolecular potential vanishes and the radial distribution function assumes the constant value which is equal to unity. Theoretical expressions for the second and third virial coefficients are also given.