bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Radio-Frequency Fields on the Electrophoretic Mobility of Some Colloids
Authors: Wilkins David J. , Heller John H. 
Published: January 2005

Four sizes of polystyrene latex, starch grains, and gelatin-coated polystyrene showed a voltage-dependent, frequency-specific response to radio-frequency fields as a function of particle size.
This response was a loss of negative surface charge irrespective of whether the initial surface charge was negative or positive.
The charge returned to original values linearly with time over a period of hours, but returned to original values in 1 min if exposed to another frequency.
At high concentrations of colloid (mean interparticle distance greater than 20 diam) no change in surface charge was apparent after exposure to an rf field. But dilution of this concentrated colloid without further exposure to rf reduced the surface charge to the value which it would have had if the diluted material had been exposed to rf.
All these phenomena occurred irrespective of whether the colloids were in distilled water or in 10—3 M NaCl.
Monte Carlo Calculations. III. A General Study of Bimolecular Exchange Reactions
Authors: Blais Normand C. , Bunker Don L. 
Published: January 2005

About 10 000 planar trajectories were computed for the reaction A+BC→AB+C. Principal variables were the reactant masses, the type of interaction potential, and the exothermicity. The activation energy was assumed negligible. The results consist of distributions of product emission angle and vibrational and rotational energy.
For the simplified interaction potentials used, the following generalizations hold: a normal reaction is one in which AB is most likely to recoil backward along the approach line of A; the energy of reaction is predominantly converted to internal excitation of the product AB; and the final rotation of AB absorbs as large a fraction of the initial orbital angular momentum as is consistent with the reaction energy. If the moment of inertia of AB is too small to allow this fraction to be close to unity, unusual distributions of emission angle and rotational excitation occur. Independently, lowered values of the internal energy of AB are observed if A is much less massive than either B or C, or if the interaction potential is not of the type involving much reactant attraction and little product repulsion.
Tentative mechanical explanations of these phenomena are presented.
Gas-Phase Radiolysis of n-Butane
Authors: Borkowski R. P. , Ausloos P. J. 
Published: January 2005

The γ-ray radiolysis of n-C4D10–n-C4H10–I2 mixtures has been investigated in the presence and in the absence of inert gases. Benzene has been added in a few experiments. In the direct and in the inert gas sensitized radiolyses, more than 95% of the propane is formed via the hydride transfer reaction: sec−C3H7++C4H10→C3H8+C4H9+.
Part of the ethane, ethylene, and propylene can be ascribed to hydride transfer reactions involving C2H5+, C2H3+, and C3H5+, respectively. The yield of these fragments relative to that of the C3H7+ increases with the recombination energy of the added inert gas. A few photochemical and radiolytic experiments using CH3CH2CD2CD3 have been carried out in order to elucidate the mechanism of the molecular detachment processes.
It can be calculated from the results that the relative yields of the fragments produced in the direct radiolysis do not exactly agree with those deduced from the mass spectrometric cracking pattern obtained at 70 eV. The discrepancy is largest for the fragments produced at a high appearance potential. The data also indicate that, in the radiolysis, the contribution of neutral excited molecule decomposition may be considerably less important than recently reported by Beck and Niehaus for pressures around 10—5 mm Hg.
Infrared Spectra in Polarized Light and Vibrational Assignment of the Infrared-Active Modes of Pyrene and Pyrene-d10
Authors: Califano S. , Abbondanza G. 
Published: January 2005

The infrared spectra of pyrene and pyrene-d10 in the crystalline state and in solution of various solvents were measured between 4000 and 400 cm-1.
Spectra in polarized light with the electric vector of the incident light vibrating in the ab crystal plane were obtained from both single crystals and oriented polycrystalline samples. Spectra in polarized light with the electric vector in the ac crystal plane were also obtained from oriented films. The comparison of the experimental dichroism with the predictions based on the knowledge of the crystal structure allowed an almost complete assignment of the fundamental modes of vibrations active in the ir spectrum.
Simultaneous Measurement of HI Fundamental and Overtone Lines
Authors: Benesch William 
Published: January 2005

Measurements of absorption line intensities in the HI overtone band at 2.3 μ have been undertaken by a method of comparison with lines in the fundamental. The technique employed lends itself particularly well to the obtaining of consistent data from two bands, which is most important for the determination of the coefficients of the dipole-moment function. These considerations led to the selection of the six overtone lines P (2) through R (3) for measurement.
One interesting aspect of the overtone intensities and matrix elements is the similarity of their magnitudes to those of the fundamental. Thus, extrapolating from the measured data to obtain a total overtone band intensity, a value of 0.19±0.02 cm—2 atm—1 at 300°K is deduced. This is more than half the fundamental-band intensity. On the other hand, as contrasted with the fundamental, there is virtually no distortion of the overtone band arising from the interaction of vibration and rotation. Consideration of all the data thus far collected on HI leads to the conclusion that the fundamental matrix elements must be negative and the overtone matrix elements positive. Likewise, it may be inferred that the value of θ2=M2re/M1 is about —5.
Polymerization Kinetics of Biological Macromolecules on Templates
Authors: Simha Robert , Zimmerman J. M. , Moacanin J. 
Published: January 2005

A kinetics of formation of polymers on linear templates is developed which is applicable to the synthesis of biological macromolecules. Two extreme situations are given theoretical treatment. In both, monomer diffuses to the template surface where polymerization may occur if an adjacent site is suitable occupied. In addition the possibility of monomer desorption is included. In one model (``unrestricted'') the reaction is initiated on each template by the polymerization of two monomers and proceeds through the addition of monomer to growing ends or by the coupling of the growing chains. In the second (``restricted'') model the number of growing centers per template is zero or one and growth is achieved through monomer addition solely. In both cases the template is assumed to be of uniform size and either single stranded or, if double stranded, with an unwinding rate that is rapid in comparison with the polymerization processes. The number of template molecules is assumed constant during the synthesis, which disregards the function of new chains as sites for continued synthesis. All degradation mechanisms are omitted from consideration, which may restrict the present theories to low conversion processes.
The pronounced differences between the unrestricted and restricted formulations in respect to kinetics and product molecular weight are elaborated and discussed in relation to recent experimental results on DNA synthesis in vitro. Finally, from known replication times in vivo, estimates of the rate parameters in the two models are derived.
Radiation Decomposition of Aqueous Nitrite Solution Containing Mercuric Salts
Authors: Shinohara Kenichi , Shida Tadamasa , Saito Nobufusa 
Published: January 2005

Aqueous sodium nitrite solutions containing mercuric salts give mercurous salts when irradiated with Co60 γ rays. The G value of mercurous salt attains to such a high value over a wide range of solute concentration that the accepted radical yields cannot account for.
In order to settle the apparent contradiction it is suggested that in a spur several excited water molecules may be produced and that they can react with nitrite ions to form excited complexes which can reduce mercuric into mercurous salt.
A Variation-Perturbation Approach to the Interaction of Radiation with Atoms and Molecules
Authors: Karplus M. , Kolker H. J. 
Published: January 2005

A variation-perturbation formulation for time-dependent interactions is presented and applied to the interaction between atoms or molecules and a semiclassical radiation field. Details of the treatment through second order are given for the steady-state problem and are compared with the standard perturbation-theory results. It is demonstrated that the usual expression for the time-dependent perturbation solution, which consists of a sum over an infinite set of excited states (including any continuum), can be replaced by a small number of frequency-dependent functions that satisfy certain time-independent differential equations. Since an exact solution to these equations is very difficult for all but the simplest cases, an equivalent variational formulation of more general utility is introduced.
The induced time-dependent electric and magnetic moments of atoms and molecules in an oscillating electromagnetic field are evaluated in terms of the frequency-dependent functions. With the usual continuum medium assumptions, the macroscopic polarizations are determined from these moments, and simple formulas for the index of refraction and optical rotatory power are obtained. The method is illustrated by a simple application to the dynamic polarizability of the harmonic oscillator and by a more detailed examination of the dynamic polarizability and index of refraction of the nonrelativistic hydrogen atom. A comparison is made between an exact solution and a variational approximation for this problem. The excellent agreement between the two methods provides an indication of the power of the variational formulation. An indication of its utility for more general applications is given.
Hydrogen-Chloride-Catalyzed Pyrolysis of Dimethyl Ether and the Use of HCl Catalysis for Diagnosis of Complex Chains
Authors: Anderson Kenneth H. , Benson Sidney W. 
Published: January 2005

The pyrolysis of CH3OCH3, catalyzed by gaseous HCl (3 to 16 mole %) has been studied in the temperature range 452° to 483°C. The rate approaches independence of HCl at the higher concentrations and is 3/2 order in ether. The products are the same as in the uncatalyzed decomposition (CH4+CO+H2 and CH4+CH2O) and no HCl is consumed. From the observation that there is up to a tenfold acceleration in rate with HCl it is shown that the slow step in the uncatalyzed pyrolysis is the reactionCH3+CH3OCH3→ lim 2CH4+CH2OCH3.The hitherto-conceived slow step CH2OCH3→ lim 3CH2O+CH3resulting from the analysis of S. W. Benson and D. V. S. Jain [J. Chem. Phys. 31, 1008 (1959)] is instead very rapid, and thus CH2OCH3 cannot be an important chain breaker.
Recent data on the stability of HCO indicate that CH3 and CHO are the actual chain-breaking radicals, both being important in the uncatalyzed decomposition. The H2S catalyzed reaction is discussed briefly and shown to be similar to the HCl system. HCl catalysis as a diagnostic tool in analyzing complex chains is discussed.
On the Excess Electron and Hole Band Structures and Carrier Mobility in Naphthalene, Anthracene, and Several Polyphenyls
Authors: Katz Joseph L. , Rice Stuart A. , Choi Sang-il , Jortner Joshua 
Published: January 2005

The excess electron and hole band structures of naphthalene, anthracene, and several polyphenyls have been calculated in the tight binding approximation. In addition the anisotropy and the pressure dependence of the mobility tensor has been calculated in the constant-free-time and the constant-free-path approximations. The molecular wavefunctions were represented in the LCAO approximation using Hückel coefficients with the carbon atomic orbitals represented by the best available Hartree—Fock SCF carbon 2p ground-state function involving a linear combination of four Slater-type functions. By this choice of atomic orbitals, we hope to account properly for the behavior of the wavefunction at the large internuclear distances relevant to this problem. All of the above compounds are characterized by a crystal structure containing two molecules per unit cell. There are, therefore, two bands for both the electron and the hole cases. The bandwidths are calculated to be of the order of 0.1 eV. In the a—1 and b—1 directions, the symmetric and antisymmetric bands are degenerate at the zone edge. The electron bands are appreciably split in the c—1 direction.
Although there is no attempt to make absolute calculations of the mobility, the experimental data seem to be in adequate agreement with the scattering models considered. Inferences can be drawn which suggest that further understanding of the mobility will arise from a detailed investigation of the interaction of the charge carriers and the intermolecular and intramolecular vibrations.
Kinetics of Desorption. III. Rb+, K+, and Na+ on Rhenium
Authors: Scheer Milton D. , Fine Joseph 
Published: January 2005

The mean adsorption lifetimes (τ3) of Rb+, K+, and Na+ ions on a clean polycrystalline rhenium surface have been measured in the millisecond region as a function of temperature under conditions of very low surface coverage. The results of these measurements are given by: Rb+:τ3=(0.8±0.3)×10−13exp[(26 400±350)/T]sec,1000&lt;T&lt;1250∘K;K+:τ3=(1.0±0.3)×10−13exp[(27 000±350)/T]sec,1050&lt;T&lt;1260∘K;Na+:τ3=(0.2±0.1)×10−13exp[(31 900±300)/T]sec,1160&lt;T&lt;1400∘K.
The interaction of the alkali ion with the metal surface was described by a one-dimensional potential function of the form V(x)=l+[1+1n−1(rex)n−nn−1(rex)],where x is the perpendicular distance of the adsorbed ion from the surface and l+ is the observed desorption energy. By choosing the Pauling ionic radius ri as the distance of closest approach to the surface for an ion with energy l+, the parameters n and re were calculated for each alkali ion. It was found that the values of n increase and those of (re—ri) decrease as the atomic number of the alkali ion increases.
Theory of the Electronic Spectra and Structure of the Polyacenes and of Alternant Hydrocarbons
Authors: Pariser Rudolph 
Published: January 2005

A previously given theory of the electronic spectra and structure of complex unsaturated molecules is further elucidated by listing specific formulas for the charge density, bond order, transition moment, and configuration interaction matrix elements.
The theory is then applied to give a number of simple rules for alternant hydrocarbons. These refer to the energies of the singly excited states and the effects of configuration interaction, the degeneracy between certain singlet and triplet states, the prohibition of certain electronic transitions which would be allowed from a group theoretical point of view, and the charge density distribution of the ground and singly excited states. A mechanism is proposed to explain some of the anomalously rapid singlet-triplet radiationless transitions which are observed in connection with studies of the lower triplet states of complex molecules.
Quantitative application of the theory is made to the spectra of the polyacenes, benzene through pentacene, and to the bond orders of naphthalene and anthracene, employing a high-speed digital computer. The calculated results are compared with experiment. Some previous assignments of electronic bands are confirmed, and some new assignments are suggested. The location of a number of excited states which have not, as yet, been observed is predicted.
Infrared Absorption Studies of Aqueous Complex Ions. II. Cyanide Complexes of Cu (I) in Aqueous Solution
Authors: Penneman Robert A. , Jones Llewellyn H. 
Published: January 2005

In the system CuCN–KCN–H2O, we have observed infrared absorption spectra of three distinct complex ions: Cu(CN)2−,ε=165±25 mole−1 liter cm−1 at 2125 cm−1;Cu(CN)3=,ε=1090±10 mole−1 liter cm−1 at 2094 cm−1;andCu(CN)4≡,ε=1657±15 mole−1 liter cm−1 at 2076 cm−1.At 29°C, the constants for the dissociation of Cu(CN)4≡ into Cu(CN)3=+CN— are: K4, 3c = 0.0076±0.0005 mole liter—1 [in terms of concentrations at 0.1—0.2f Cu(I)] and K4, 3a = 0.026 mole liter—1 (in terms of activities). Analogous values for the dissociation of Cu(CN)3= into Cu(CN)2—+CN— are K3, 2c = (2.44±0.36)×10—5 mole liter—1, and K3, 2a = 4.2×10—5. The above values are calculated from approximately 100 determinations. At 25°C, the corresponding values of these constants are approximately K4, 3c = 0.0057 and K3, 2c = 1.5×10—5.
Using the activity constants determined in this paper and a value of 1×10—24 for the constant: [Cu+][CN—]2/[Cu(CN)2—] we derive the following values: [Cu+][CN—]3/[Cu(CN)3=] = 2.6×10—29 and [Cu+][CN—]4/[Cu(CN)4≡] = 5×10—31. The free energies of formation of the complex ions are thus: Cu(CN)2—, ΔFf0 = 58.5 kcal/mole; Cu(CN)3=, ΔFf0 = 91.8 kcal/mole; and Cu(CN)4≡, ΔFf0 = 129 kcal/mole.
Chain Model for Polyelectrolytes. III. Equimolar Polyampholytes of Regularly Alternating Structure
Authors: Rice Stuart A. , Harris Frank E. 
Published: January 2005

The chain model for polyelectrolytes developed in the preceding papers of this series is extended to polyampholytes composed of a regular alternation of acidic and basic groups. Included in this model are the effects of counter ion binding, dissociation equilibria among the acidic and basic groups, and electrostatic interactions among the charges of the polymer. The electrostatic free energy of interaction between neighboring charges of the chain was computed including interactions between both nearest and next nearest neighboring charge sites by a simple extension of the methods previously employed. The equilibrium conditions are then expressible as a set of simultaneous equations which may be solved by a convenient iterative method.
The end-to-end extension may be calculated by previously described methods except in the vicinity of the isoelectric point (i.p.), near which point the effects of charge fluctuations become relatively more important. It is shown how both charge fluctuation and the distribution of monomer units along the polymer chain are related to its end-to-end extension. However, for a regularly alternating copolymer the skeletal distribution effect vanishes.
Calculations for a hypothetical polymer indicate that the expansion is nearly independent of ionic strength, and that the fluctuations produce a negligibly small contraction at the i.p. However, it is found that added salt acts, primarily by reducing the electrostatic forces, to alter the titration curves in the same manner as has been observed experimentally in dilute protein solutions.
Statistical Thermodynamics of Solutions
Authors: Prigogine I. , Bellemans A. , Englert-Chwoles A. 
Published: January 2005

A new approach to the statistical problem of solutions is presented, which combines the main ideas of the cell method and of the theorem of corresponding states. The basic assumption is that the cell partition function of a molecule in the solution may be formally expressed by the same function as in pure liquid, but with other well-defined values of the reduced temperature and volume.
For pure liquids this theory reduces to the usual theorem of corresponding states. The excess properties of the mixture are expressed in terms of molecular parameters related to the interaction energies between pairs of molecules. All the macroscopic coefficients appearing in the excess functions are expressed by experimental properties of the pure compounds, just as in the theory of conformal solutions of Longuet-Higgins. The present model correctly gives the ``first-order contributions'' to the excess functions like the theory of conformal solutions; it gives also an approximative estimate of the higher order terms. Explicit expressions for the excess functions have been calculated up to the second-order terms. The relations between intermolecular forces and excess functions is discussed in detail for some typical cases.
All the conclusions drawn from this model confirm those obtained previously by Prigogine and his collaborators; however the present model permits a much more direct derivation of the main results without the introduction of subsidiary simplifying hypotheses (like simplified cell models).
Kinetic Study of the Reaction of Diborane with Phosphine
Authors: Brumberger H. , Marcus R. A. 
Published: January 2005

The homogeneous gas phase reaction between diborane and phosphine at 0°C, yielding a solid product of composition BH3PH3, has been observed to give a linear relation between the initial rate of reaction and the pressure of either reactant, provided a certain pressure of each reactant, determined by the equilibrium constant and the pressure of the other gas, is exceeded. The reaction rate is independent of the amount of surface of the solid product or of the wall. When either reagent is in appreciable excess, the rate-time data obey a pseudo first-order equation.
These facts are consistent with a rate-controlling reaction of diborane with phosphine to give BH3PH3 and BH3, the borine reacting further with phosphine, and the BH3PH3 condensing rapidly to a solid. This mechanism leads to a rate equation which is in good agreement with the experimental evidence. The activation energy of the rate-controlling step is 11.4±2.0 kcal mole—1.
Kinetics of Activation Controlled Consecutive Electrochemical Reactions: Anodic Evolution of Oxygen
Authors: Bockris J. O'M. 
Published: January 2005

The kinetics of activation controlled electrode reactions differ from those of chemical kinetics by the potential dependence of the rate constant of a step involving charge transfer and the constancy of concentration of reactants in the initial state. A method is proposed whereby an expression for the kinetics of an electrode reaction containing any number of intermediate steps may be obtained.
The method is applied to five paths for the electrolytic evolution of oxygen at anodes and yields limiting expressions for the dependence of the current density (or rate) of the reaction upon electrode potential which are diagnostic of the various rate controlling steps assumed. If discharge of OH′ or H2O molecules is rate determining, the Tafel slope is 2RT/F at overpotentials &gt; 50 mv. If some other reaction involving charge transfer is rate determining, two possible Tafel slopes, each independent of potential in its range of applicability, occur, depending upon degree of coverage of the electrode with intermediate products. If a reaction involving no charge transfer is rate determining, a number of Tafel slopes is indicated, each characteristic of the rate controlling reaction, and an activation controlled limiting current density is possible.
Quantitative conditions for change of mechanism with current density are evaluated. For the initial reaction of a consecutive series to be rate determining it suffices that the rate constant for the backward partial reaction of this step be limitingly small compared with other rate constants in the series; for the last reaction to be rate controlling, the rate constant of its forward partial reaction must be limitingly small; for any other reaction in the series, both backward and forward rate constants of the rate determining reaction must be limitingly small.
The rate of the anodic oxygen evolution reaction as a function of pH is evaluated, taking into account concentration and foreign electrolyte effects on the electrokinetic potential at the electrode-solution interface. The results enable the discharging entity in solution to be distinguished.
Former data are reinterpreted from the criteria of mechanism deduced.