bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemistry of Ferrous Ions in Aqueous Solution
Authors: Rigg Tyson , Weiss Joseph 
Published: January 2005

The photochemistry of ferrous ions in aqueous solutions has been investigated, and it has been confirmed that irradiation in the quartz ultraviolet, in the absence of oxygen, leads to the formation of ferric salt and molecular hydrogen. It has been concluded further that the primary absorption of a light quantum results in the formation of excited ions, (Fe2+·H2O)*, a considerable proportion of which undergo processes of deactivation, while the remaining (about one-tenth) dissociate according to (Fe2+·H2O)*→Fe3++OH−+H, leading to the formation of hydrogen atoms. The latter can undergo back reactions of the type Fe3++H→Fe2++H+. Investigation of the pH dependence of the quantum yield has led to the assumption that hydrogen atoms can also react according to H+H(hydr)+⇌H2(hydr)+, leading to the formation of hydrated hydrogen molecular ions which intervene in this process according to the reaction Fe2++H2+→Fe3++H2.
Other experimental evidence and some theoretical considerations which have led to the assumption of H2+ (hydr) in aqueous solution are referred to.
The Properties of the Interstitial Compounds of Graphite. II. The Structure and Stability of Graphite Residue Compounds
Authors: Hennig Gerhart 
Published: January 2005

1. Controlled decomposition of lamellar compounds of graphite produces substances intermediate in composition between graphite and lamellar compounds. These intermediate compounds have been termed residue compounds. They are much more resistant to decomposition than the lamellar compounds.
2. The x-ray pattern of residue compounds shows a very slight increase in the c spacing of the graphite lattice. The increase is entirely insufficient to account for the trapped reactant. Consequently, the bulk of the trapped reactant is believed to be situated at crystal imperfections.
3. Quantitative studies of the composition of graphite bromide residue compounds have shown that their composition is strongly dependent on the type and subdivision of the graphite used and the temperature to which the compounds have been heated.
The Properties of the Interstitial Compounds of Graphite. III. The Electrical Properties of the Halogen Compounds of Graphite
Authors: Hennig Gerhart 
Published: January 2005

The presence of lamellar or of residual bromine in artificial graphite reduces the resistance, the absolute magnitude of its temperature coefficient near room temperature, and the magneto resistance. The Hall coefficient increases and eventually changes from negative to positive values. The changes resemble very closely those obtained in the oxidation of graphite in sulfuric acid. This similarity in properties suggests that the electron acceptors in these compounds are only weak scattering centers for conduction electrons.
Since the electrical properties of graphite bisulfate and of graphite bromide are very similar, it may be assumed that both compounds are of a similar type. Since the bisulfate compound is ionic in nature, the bromine in graphite bromide is also probably ionized. On this assumption the graphite bromides have the formulas CnBr·3 Br2 for the lamellar and CnBr·2.25 Br2 for the residue compounds.
Chlorine reacts with graphite at low temperatures only. The properties of the compounds of chlorine and graphite resemble in all respects those of the compounds of bromine and graphite. Attempts to react iodine and graphite have failed. Iodine chloride, however, reacts rapidly with graphite.
Electronegativity
Authors: Klopman G. 
Published: January 2005

The concept of ``electronegativity'' is discussed and reviewed in the light of recent observed relationships between successive ionization potentials. A differentiation is made between atomic and molecular electronegativity and particular reference is made to the principle of equalization of molecular electronegativities in the process of forming a bond.
The Rydberg equation for atoms is used as a basis for the quantitative calculation of the atomic spectra and electronegativity of systems in any valency state. The resulting equation can be used either to calculate atomic electronegativities or to determine quantitatively the diagonal matrix elements in SCF calculations for molecules involving heteroatoms.
Multicenter Integrals in Quantum Mechanics. I. Expansion of Slater-Type Orbitals about a New Origin
Authors: Harris F. E. , Michels H. H. 
Published: January 2005

Convenient and accurate formulas have been found which implement the spherical-harmonic expansion of a Slater-type orbital about a point displaced from the orbital's center. These formulas include, as a special case, the expansion of spherically symmetric orbitals which has been reported previously. The results are presented in algebraic form, suitable for machine computation, and have been tested for the transformation of any Slater-type orbital with n≤7, l≤3, | m |≤l to an arbitrary space-fixed point.
By the use of this analysis, in conjunction with the properties of the rotation group, it is now possible to evaluate directly, the general multicenter electron-repulsion integral expressed in terms of Slater-type orbitals. The convenience of this direct approach suggests that previous analyses in terms of Gaussian orbitals or Gaussian approximations to Slater-type orbitals, replete with their poor radial dependence, may no longer offer any computational advantages.
Stability Conditions for the Solutions of the Hartree—Fock Equations for Atomic and Molecular Systems. Application to the Pi-Electron Model of Cyclic Polyenes
Authors: Čížek J. , Paldus J. 
Published: January 2005

The stability conditions which ensure that the Hartree—Fock determinant minimizes the energy expectation value are rederived using the language familiar in quantum chemistry. These stability conditions are then specified for the case of closed-shell electronic systems which allow additional simplification of the conditions as well as a certain classification of the instabilities.Examples of the instabilities of different types are presented and the case of the so-called singlet instabilities—most interesting from the physical point of view—is studied in detail for the pi-electron model of cyclic polyenes.
Partial Interference and Atomic Distribution Functions of Liquid Silver—Tin Alloys
Authors: Halder N. C. , Wagner C. N. J. 
Published: January 2005

The x-ray scatterings from liquid Ag–Sn alloys previously measured at temperatures 100°C above the respective liquidus temperatures have been reanalyzed. The total-interference functions (also called structure factors) I(K), where K=4π sinθ/λ, were first refined and then used to calculate the partial-interference functions Iij(K), assuming that they are approximately independent of the atomic concentrations. The least-squares analysis with five different atomic concentrations of Sn, i.e., 18.5, 25, 36.5, 50, and 68.5 at.%, yielded three Iij(K).
The Fourier transform of Iij(K) leads to the partial radial distribution function (RDF)=4πr2ρij(r)/cj, and the reduced distribution function Gij(r)=4πr[ρij(r)/cj—ρ0], where ρij(r) is the partial radial density, cj is the atomic concentration of the j-atoms and ρ0 is the average atomic density. Thus calculated Iij(K) and Gij(r) were used to reproduce the measured I(K) and their corresponding G(r), and a remarkably good agreement was found between the measured and calculated values. Judging from the observed agreement, it can be concluded that for liquid Ag–Sn alloys the partial ISnSn(K), IAgAg(K), and ISnAg(K) are not influenced by the relative abundance of the elements.
The resistivity of the alloys obtained with Iij(K) and the pseudopotential elements Ui(K) agrees well with those measured experimentally.
Surface Ionization. I. Desorption of U+ Ions from W and Re Surfaces
Authors: Hertel G. R. 
Published: January 2005

The mean residence times (τ) of U+ ions on polycrystalline W and Re surfaces have been measured as functions of the surface temperature. The U+ desorption parameters that were determined from the relationship 1/τ=ω0 exp[—Ei/kT] are       Surfaceω0(sec−1)Ei(eV)Clean W(3.2±1.5)×10157.50±0.09Contaminated W(1.9±1.5)×10136.29±0.17Clean Re(0.7±0.3)×10136.70±0.09Slightly contaminated Re(1.2±0.7)×10136.84±0.14.
The effect of oxygen contamination on the W surfaces was dramatic. The Re results were not as clear cut. In the temperature range where uranium oxide ions were abundant, the simple desorption mechanism is complicated by surface reactions. The resulting log(τ−1) vs T−1 relationship is complex and nonlinear.
Nonadiabatic Decomposition of N2O in the Deactivation of O(1D) by N2
Authors: Snelling David R. , Bair Edward J. 
Published: January 2005

An extension of a flash-photolysis method described previously was used to measure the following absolute rate constants (all in liter per mole·sec): O(1D)+O3→2O2k2=2.0±1.0×1011,O(1D)+N2→O(3P)+N2k4a=1.3±0.6×1010,O(1D)+Xe→O(3P)+Xek4b=3.5±1.7×1010,O(1D)+Ar→O(3P)+Ark4c∼5×107.
The efficiency with which the O(1D)→O(3P) transition is induced by collisions depends specifically on the added gas. The results for deactivation by nitrogen are discussed in terms of the formation of an N2O* intermediate in a high level of vibrational excitation. Dissociation to N2+O(3P) at this energy level (85.2 kcal) is compared with thermal decomposition of N2O where predissociation to a state which correlates with O(3P) occurs at a lower energy level (〈ε〉=61.8 kcal).
On the Stochastic Theory of Dissociation and Recombination of Diatomic Molecules in Inert Diluents
Authors: Brau Charles A. 
Published: January 2005

A formal stochastic theory is developed to describe the dissociation and recombination of diatomic molecules by inert third bodies, and the manner in which this reaction is coupled with internal relaxation processes. Singular perturbation methods are used to obtain a uniformly valid asymptotic solution to the nonlinear master equation in the limit when the internal relaxation times are short compared with the dissociation time. The solution shows that the reaction begins with a short transient during which the internal distribution function relaxes from the initial state to a ``quasisteady'' state. Following this, the reaction obeys the usual phenomenological equations with well-defined rate coefficients. It is shown that to lowest order the observed rate coefficients are constants during the quasisteady period, and retain their nonequilibrium values as the reaction approaches equilibrium. In higher orders the dissociation and recombination rate coefficients depend on the instantaneous composition of the gas. However, the ratio of the instantaneous values of the dissociation and recombination rate coefficients remains equal to the equilibrium constant. It is also shown that the initial transient causes an observable ``incubation time'' to appear in the reaction. The formula for the incubation time is derived, and applied to the special cases of dissociation behind a shock wave and recombination following flash photolysis.
The results are applied to the dissociation and recombination of diatomic molecules possessing rotational, vibrational, and electronic degrees of freedom.
Factor Group Splitting and Zeeman Splitting of the Lowest Triplet State of Phenazine
Authors: Clarke Richard H. , Hochstrasser Robin M. 
Published: January 2005

The T1←S0 transition of the phenazine crystal is studied in polarized light, and in high magnetic fields, with the crystals at 4.2°K. A factor group splitting of 4 cm−1 is observed in the 0, 0 band. The two components have the same polarization—predominantly along the b axis. The polarization, relative intensity, and Zeeman spectra are used to assign the plus and minus factor group states in association with a crystal symmetry adapted spin—orbital coupling theory.
The lowest triplet state is assigned as 3B2u in agreement with theoretical predictions.
Elastic Electron Scattering Amplitudes for Neutral Atoms Calculated Using the Partial Wave Method at 10, 40, 70, and 100 kV for Z = 1 to Z = 54
Authors: Cox H. L. , Bonham R. A. 
Published: January 2005

Elastic electron scattering amplitudes for neutral atoms were calculated using the partial wave expansion method for 10-, 40-, 70-, and 100-kV incident electrons. The partial wave phase shifts were calculated by numerical intergration using the phase amplitude method until the results converged to values obtained using the WKBJ and first Born approxmations, which were then used in the remainder of the partial wave sum.
The static potential field of the target atoms was represented by an analytical expression involving a sum of Yukawa terms. Potential field parameters for the expression were obtained by a least-squares fit of the radial electron distribution function, D (r), using Hartree—Fock and relativistic wavefunctions for all the neutral atoms from Z=1 to Z=54. For the smaller atoms from Z=1 to Z=21, Clementi Hartree—Fock wavefunctions were used and for the atoms from Z=22 to 54 Liberman—Waber—Cromer D (r) curves calculated using the Dirac Hamiltonian incorporating a j—j coupling scheme and the Slater ⅔ approximation in the exchange potential were used.
Gas-Phase Photolysis of Ethyl Iodide at 2537 and 2288 Å. Reactions of Hot Ethyl Radicals with Added Hydrocarbons
Authors: Rebbert R. E. , Ausloos P. 
Published: January 2005

The photolysis of C2H5I and C2D5I have been investigated at 2537 and 2288 Å in the presence of thermal alkyl radical scavengers such as O2 or I2. The ethane (quantum yields at 2537 Å: φC2H6=0.82×10−3, φC2D6=0.29×10−3) formed in such mixtures can be entirely ascribed to abstraction of an H (or D) atom by a ``hot'' ethyl radical formed in the primary dissociation of ethyl iodide. The differences in quantum yield between C2H6 and C2D6 are in part ascribed to a difference in the partitioning of the excess energy (∼30–40 kcal) carried over from the primary process into vibrational and translational modes. When C2D5I or C2H5I is photolyzed in the presence of a cyclo-C6H12–cyclo-C6D12–O2 mixture (1:1:0.1), or of a cyclohexane-1,1,2,2,3,3,-d6–O2 mixture, the relative probability for abstraction of an H atom vs that for abstraction of a D atom (πH/πD) is equal to 1.5±0.1. The latter value shows little dependence on a change in wavelength and is also not affected when unreactive gases are added to the reaction mixtures. The added gases do, however, reduce the probability of the abstraction process. For instance, the probability of reaction with cyclohexane by a ``hot'' C2D5* radical is reduced 50% after one collision with carbon dioxide, the most efficient quencher used. The relative quenching probability of the ``hot'' C2D5* radical by different additives is as follows: He−0.50; Ne−0.62; N2−1.00; and CO2−1.51.
When C2H5I is photolyzed at 2537 Å in the presence of CD3CH2CD3, CH3CD2CH3, or CD3CH2CH2CD3 it shows that the relative probability per atom for the abstraction of a primary compared to a secondary H atom in a hydrocrabon molecule by a hot ethyl radical is 1:4.5. Moreover, the quantum yield for ethane formation at 2537 Å per secondary hydrogen atom for a series of cycloalkanes and normal alkanes is 0.32±0.07×10−3.
Kinetics of the Homogeneous Exchange Reaction: 14–14N2+15–15N2⇋214— 15N2. Single-Pulse Shock-Tube Studies
Authors: Bar-Nun Akiva , Lifshitz Assa 
Published: January 2005

The kinetics of the homogeneous exchange reaction in molecular nitrogen highly diluted in argon was studied in a single-pulse shock tube over a wide range of temperatures, initial pressures, and compositions. The reaction order with respect to the total nitrogen, argon, and the over-all reaction order were determined. A rate law: Rate=kb[Ar][N214]+kb[Ar ][N215], which is a sum of two parallel reactions, was found to be compatible with the experimental results kb=1013.82±0.31 exp[−(116±5)×103/RT) cc mole−1·sec−1. It was shown that the exchange reaction does not proceed via a radical chain. A mechanism based on vibrational excitation of the nitrogen molecule to a critical vibrational level as a rate determining step is proposed. A rate constant, computed from available vibrational relaxation data in nitrogen agrees very well with the observed rate constant.
It was found that slight amounts of oxygen, up to O2/N2∼0.01, had very little effect on the reaction rate. In the presence of higher oxygen concentration, O2/N2∼0.5, the exchange proceeds mainly via an atom displacement mechanism. An approximate rate constant for the reactionN*+N2→ lim k3N+N2*, k3=3×1011 cc mole−1·sec−1at 3400°K was obtained.
The temperature range involved in this study, i.e., 3200°—3800°K, is the highest ever reported in a single-pulse shock-tube study. The gas-dynamic conditions and an innovation in the design of the shock tube are briefly described and discussed.
Capture Collisions between Ions and Polar Molecules
Authors: Dugan John V. , Magee John L. 
Published: January 2005

The manner in which a permanent dipole in a molecule affects capture collisions of the molecule with ions is investigated. Analytical capture cross sections are considered, and three cases are distinguished. None of these is strictly applicable to real collisions, but they are useful in establishment of the general magnitudes of cross sections. The Langevin cross section is somewhat of a lower limit. A strict upper limit to the cross section is derived; it depends on the magnitude of the dipole moment. A quantum-mechanical treatment at small relative velocity uses the effective potential of interaction determined by the Stark effect; cross sections for this case depend explicitly on the rotational energy of the polar molecule. Molecules which have a first-order Stark effect have a term ε−1 in their cross sections, whereas the second-order Stark effect only leads to the ε−1/2 term of the Langevin theory (ε is the relative translational energy).
Numerical cross sections are obtained by using a computer study of collisions. The classical equations of motion are solved. Spiraling collisions (predicted in the Langevin theory) are not obtained, but it is found to be possible to define ``capture'' adequately and to set up a procedure for calculation of capture cross sections. This procedure involves averaging initial conditions with proper weighting. The real molecule HCl has been used in the calculations, and the results are compared with experiment as far as possible. A hypothetical molecule with the same dipole moment and polarizability of HCl but with a moment of inertia 100 times larger is also considered.
Infrared Spectrum of the Methyl Radical in Solid Argon
Authors: Andrews Lester , Pimentel George C. 
Published: January 2005

Reaction between lithium atoms and methyl halides during condensation in solid argon at 15°K produces absorptions at 730.3 and 1383 cm−1 that can be attributed to the methyl radical CH3. Isotopic substitutions (CH3, CH2D, CHD2, CD3, 13CH3) and behavior on warming, during which ethane absorptions replace the methyl features, furnish convincing evidence for the assignment.
Normal-coordinate analysis shows that the 730-cm−1 band is due to ν2, the out-of-plane bending mode of CH3 with a force constant of 0.25 mdyn/Å. These calculations favor the planar structure and they exclude an equilibrium deviation from planarity in excess of 5°. The absorption at 1383 cm−1 is due to ν4, the in-plane bending mode, with a force constant of 0.34 mdyn/Å. The asymmetric stretching mode, ν3, was not detected.
The out-of-plane bending force constants of D3h molecules can be correlated by separating the force constant into sigma- and pi-bonding parts. This correlation leads to a prediction of the out-of-plane frequency of BH3, 590 ±50 cm−1. Thermodynamic functions for both CH3 and BH3 are presented.
Thermodynamics of Dilute Solutions of High Polymers
Authors: Flory Paul J. 
Published: January 2005

Whereas extensive efforts have been directed recently toward improving the mathematical exactness of the statistical mechanical theory of polymer solutions, fundamental limitations set by the nature of the physical approximations have not received adequate attention. A careful comparison between theory and experiment in dilute solutions reveals a large discrepancy between the calculated and the observed departures from the ideal entropy of dilution. The assumption of random occupancy of lattice sites by polymer segments, which is employed in previous treatments, is at fault. In very dilute solutions of high polymers the solution is microscopically discontinuous. Two regions of the volume can be distinguished: one is totally unoccupied by segments of polymer molecules; the other consists of regions encompassed by the irregularly coiled polymer molecules. In the latter the concentration of lattice cells occupied by polymer segments is determined by the configuration of the polymer molecule, being independent of the over-all average concentration.
The above concepts have been employed in the formulation of a new statistical mechanical theory of the thermodynamic properties of very dilute high polymer solutions. The deviation from ideality, e.g., the slope of the osmotic pressure: concentration ratio plotted against concentration, is related to the ``effective volume ratio'' of the irregularly coiled solute molecule. This ratio, or ``swelling factor,'' can be estimated from the intrinsic viscosity of the polymer. Satisfactory agreement between theory and experiment is obtained in this way. The comparatively small deviations from ideality which are observed for protein molecules, not extremely dissymmetric in shape, receive semi-quantitative interpretation under the present theory. The failure, of the van Laar expression to account for heats of mixing in polymer solutions at all concentrations is a necessary consequence of the discontinuities in the dilute region.
Osmotic Flows in Charged Membranes. II. Thermo-Osmosis
Authors: Kobatake Yonosuke , Fujita Hiroshi 
Published: January 2005

Thermo-osmotic flow rates of an electrolyte solution through a porous charged membrane separating two solutions which are at different temperatures but have the same concentration is studied theoretically, using a capillary model for the membrane. The assumptions used are that the Debye-Hückel approximation is applicable for the ion distribution in the double layer formed near the fixed charges on the capillary wall, and that the thickness of the double layer is much smaller than the capillary radius. The steady-state solutions of a set of differential equations derived are obtained subject to appropriate external conditions. It is shown that plots for the flow rate of fluid against the logarithm of the concentration of the outer solution give a bell-shaped curve. This theoretical curve follows well the Carr—Sollner data of the thermo-osmosis for various electrolyte solutions.
The thermo-osmosis is an electro-osmotic flow caused by the electric field which is set up in the membrane so that no net electric charge is allowed to be transported across the membrane. The dependence of the electro-osmotic coefficient on salt concentration is the primary cause for the characteristic behavior of the thermo-osmosis in charged membranes. It has been shown in Part I of this series that this effect is also responsible for the anomalous osmosis.