bluuebunny/crossref_metadata_2025 huggingface dataset:
Applicability of Almost Strongly Orthogonal Geminals in Many-Electron Wavefunctions
Authors: Kapuy Ede
Published: January 2005

Assuming that truncated strongly orthogonal geminals for a system are already known, the possibility of using rij-dependent correction functions in the geminals is discussed with an emphasis on the violation of the strong orthogonality conditions. It is shown that for given truncated geminals there always exists at least one optimally decomposed complete set of one-electron functions, which makes it possible to pick out the configurations giving rise to strong orthogonality condition violating terms in the energy expression. The latter can be neglected, as compared with others which are of second order in the correction functions, when the system consists of spatially separated pairs in the sense that the one-electron functions contributing appreciably to one pair do not have significant differential overlap with the starting basis functions of other pairs. In this case interorbital effects are also small. For systems consisting of weakly localizable pairs, when the strong orthogonality condition violating terms are all omitted, the energy expression is correct only up to first order in the correction functions. It is shown that the same difficulties arise in the many-electron theory of Sinanoğlu.
Microwave Spectrum of Silver Bromide
Authors: Krisher Lawrence C. , Norris Wilfred G.
Published: January 2005

Microwave transitions have been observed for the four naturally abundant AgBr species at about 850°C. The pure rotational spectra of molecules in several vibrational states have been obtained. The internuclear distance is re = 2.392212±0.000004 Å. Quadrupole hyperfine splittings due to the 79Br and 81Br nuclei give coupling constants eqQ of 307 and 257±20 Mc/sec, respectively. The molecular constants for 107Ag79Br are found to be Be = 1943.687±0.003 Mc/sec, αe = 7.0742±0.0050 Mc/sec, γe = 5.02±0.45 kc/sec, De = 0.53±0.13 kc/sec. Values are given for the remaining three isotopic combinations.
Argon—Oxygen Phase Diagram
Authors: Barrett C. S. , Meyer L. , Wasserman J.
Published: January 2005

The phase diagram of Ar–O2 was determined by x-ray diffraction. On the Ar-rich side, a phase having hexagonal-close-packed structure exists under the solidus. This phase undergoes a strain-induced transformation at low temperatures to face-centered cubic in mixtures from 1% to 20% O2. From 20% to 50% O2, the hcp persists to 0°K. On the O2-rich side, γ-O2 dissolves Ar to 12½% Ar, and β-O2 to 21% O2. Both structures coexist with the hcp in wide two-phase regions. The α phase can accept up to 20% Ar. A new phase, designated δ, was discovered, which can exist between 55% and 90% O2. Transformation characteristics suggest that there is a structural relationship between the δ and γ phases, and between the α and β phases. The lattice constants of 20% and 45% O2 hcp mixtures, determined at 23°K, are nearly identical.
On the Calibration of the Mass Spectrometer for Measurement of Partial Vapor Pressures
Authors: Cater E. David , Thorn R. J.
Published: January 2005

A fundamental problem in the mass-spectrometric study of the vapors in equilibrium with condensed phases at high temperatures is the determination of the absolute instrumental sensitivities to the several species in the vapor. An analysis is presented which shows that calibration for all the individual species can be accomplished without additional information if the absolute total rate of effusion is obtained as a function of temperature and is combined with mass-spectrometric measurements of the relative intensities of the individual species. General equations are derived and two procedures for treating the case of two species are presented.
Microwave Spectrum, Dipole Moment, and Ring-Puckering Vibration of Vinylene Carbonate
Authors: Dorris Kenneth L. , Britt Chester O. , Boggs James E.
Published: January 2005

The microwave spectrum of vinylene carbonate has been studied in the frequency region between 12 000 and 26 500 Mc/sec. Rotational constants and moments of inertia have been derived for the vibrational ground state and for the first three excited states of the ring-puckering vibrational mode. The molecule is planar, with no barrier at the planar configuration in the ring-puckering potential function. Measured intensities of the vibrational satellites are fitted well by a purely quadratic potential function. The dipole moment, which lies exclusively along the a axis, is 4.57±0.05 D.
On the Macedo—Litovitz Hybrid Equation for Liquid Viscosity
Authors: Chung H. S.
Published: January 2005

The Macedo—Litovitz hybrid equation for the viscosity of liquids is derived using statistical-mechanical arguments. The formulation is based upon the assumption that diffusion in liquids is governed by (1) the presence of an adjacent free volume of certain size into which a molecule can jump and (2) the acquisition of sufficient energy by the diffusing molecule to escape from the force field of its neighbors.
High-Temperature Vapor-Pressure Studies of UO2 by the Effusion Method and Its Thermodynamic Interpretation
Authors: Ohse Roland W.
Published: January 2005

A high-temperature effusion investigation under vacuum of the vapor pressure of UO2 is presented over the temperature range from 2200° to 2800°K. A least-square analysis of the experimental results yielded the equation logp (mm)=12.426–3.318(104/T).The latent heat of sublimation ΔH°298=148.6 kcal/mole was determined by applying the third-law method of thermodynamics. Blackbody hole readings, corrected for both the transmissivity of interposed windows and the cavity temperature, were checked by measuring the spectral emissivity of the optically smooth polished tungsten surface at 0.65 μ, which decreased from 0.44 at 2300°K to 0.416 at 2850°K.

Compatibility tests at 2800°K revealed no signs of a noticeable reaction between UO2 and the tungsten effusion cell.
Ionic Adsorption and Dissociation Cross Section for Nitrogen
Authors: Winters H. F.
Published: January 2005

The adsorption of energetic N2+ ions on nickel and molybdenum surfaces has been investigated. Comparison of the sticking probabilities of N2+ and Ar+ as a function of ion energy indicates that the binding mechanism for these two gases is different. The experimental evidence suggests that the mechanism causing adsorption of N2+ may be dissociation upon collision with the surface and the subsequent adsorption of the resulting atomic nitrogen.

The total absolute dissociation cross section has also been measured in nitrogen for electron energies from 0 to 300 eV. The cross section has a maximum value of 2. 10−16 cm2 at an electron energy of about 90 eV.
Adsorption Isotherms for Polymer Chains Adsorbed from Θ Solvents
Authors: Hoeve C. A. J.
Published: January 2005

In the case of interacting polymer chains near the interface, the first layer at the interface, corresponding to the thickness of segments, is treated as a polymer solution to which the Flory—Huggins theory is applied. Interaction in other layers is assumed to be absent for Θ solvents. On minimizing the free energy, adsorption isotherms are calculated. The amount of adsorbed polymer increases without limit and the fraction of segments in the first layer decreases to zero with increase in molecular weight and solution concentration. The root-mean-square distance of segments from the interface is also calculated and is found to vary approximately proportional to the square root of the molecular weight, in good agreement with experiment.
Electrical Conductivities of Molten Cadmium—Cadmium Halide Solutions
Authors: Grantham L. F.
Published: January 2005

The electrical conductivities of molten cadmium—cadmium halide solutions were determined as a function of composition and temperature to 1000°C. The composition ranges studied were 0–20, 0–30, and 0–15 mole % Cd for the chloride, bromide, and iodide systems, respectively. The specific conductivity increased with temperature in all systems at all compositions. In the chloride system, the conductivity decreased below 800°C but increased above 900°C as the cadmium concentration increased. In the bromide and iodide system the conductivity increased monotonically with composition at all temperatures. The conductivity and activation energy for conduction in the metal—salt solutions deviated only a small amount from that of the pure salt. Thus, electronic conduction does not appear to be a major conductivity mechanism in the Cd—CdX2 systems in the temperature and concentration range studied.
Polymorphism and Melting of Ammonium, Thallous, and Silver Nitrates to 45 kbar
Authors: Rapoport Eliezer , Pistorius Carl W. F. T.
Published: January 2005

The phase diagrams of NH4NO3 and TlNO3 were determined by means of differential thermal analysis to 40 kbar. The NH4NO3 I/VI, IV/VI, and I/IV transition lines meet at a triple point near 19.5 kbar, 256°C. The TlNO3 I/II transition line can be represented by t(degrees Centigrade) = 144.6+7.91P−0.062P2, and the melting curve of TlNO3 I is given by P (kilobars) = 5.00 [(T/479)3.531−1]. The phase diagram of AgNO3 was determined by means of DTA and volumetric methods to 45 kbar. In addition to the four phases previously known, metastable AgNO3 V can be obtained by suitable manipulation above 21 kbar at temperatures below 50°C. The metastable AgNO3 I/V transition is easily reversible. AgNO3 V reverts to stable AgNO3 II if left under pressure overnight. The melting curve of AgNO3 II is given by P (kilobars) = 9.17[(T/483)4.438−1].
Raman Spectral Studies of the Effects of Temperature on Water and Electrolyte Solutions
Authors: Walrafen G. E.
Published: January 2005

All known intermolecular Raman bands of water, viz., the hydrogen-bond bending and stretching bands, and the librational bands, decrease rapidly in intensity with temperature rise. In contrast, the librational intensities of water in electrolyte solutions exhibit very small variations with temperature. The intensity decreases observed for pure water indicate that hydrogen bonds are broken by increase of temperature, but the near constancy observed for solutions indicates that primary hydration is not greatly affected, even at temperatures near the normal boiling points of some of the solutions studied.

Integrated Raman intensities of the hydrogen-bond-stretching vibrations of pure water at 152–175 cm−1 were redetermined in the temperature range of −6.0° to 94.7°C. The new intensity data, which are more accurate than the old [cf., J. Chem. Phys. 40, 3249 (1964)], yield the values ΔH°=5.6 kcal/mole and ΔS°≈19 cal/deg·mole for the process B→U, where B refers to water molecules which contribute intensity to the 152–175-cm−1 Raman band, and U refers to molecules which make very little or no contribution. Interpreted in terms of non hydrogen-bonded monomeric defects in a tetrahedral liquid lattice, the above ΔH° yields a value of 2.8 kcal/mole H bond in resonable agreement with Scatchard's value of 3.41 kcal/mole H bond. The value of ΔS° for the process B→U also leads to interesting comparisons with known entropies, but the calculated heat capacity of water is only in fair agreement with accepted values.

The observed insensitivity of the solution librational intensities to changes of temperature indicates that primary hydration is involved almost exclusively. This conclusion complements the previous observations involving linearity of librational intensity with electrolyte concentration [cf., J. Chem. Phys. 36, 1035 (1962)], since both observations can be explained by primary hydration.

In addition, molar librational intensities (obtained from the temperature studies) confirm the large anionic effects reported previously, with Br−>Cl−, but they also indicate that the effects produced by NH4+ are much smaller than those arising from Li+, Na+, and K+. It is apparent, therefore, that at least some cationic effects can be observed in the Raman spectra.
Polarization Studies on Recombination Luminescence in a Rigid Organic Solution
Authors: McClain W. M. , Albrecht A. C.
Published: January 2005

Polarized photoselection techniques are applied to stimulated recombination luminescence in a rigid organic solution at 77°K. Ionization with polarized ultraviolet light leads to an oriented sample of solute cation and electrons trapped in the matrix. Infrared light stimulates the recombination of the electrons with the oriented population of cations giving a recombination luminescence whose polarization characterizes the orientation of the cations.

Two interpenetrating populations of cations are produced sequentially using perpendicular polarization directions for the ionizing light. Recombination emission from the two populations may be distinguished by their differing polarization, and it is found that the electrons ejected in the ionization of one population do not recombine with the cations of the other.

These results are examined in some detail. It is concluded that in the majority of ionization and recombination events, each electron remains highly correlated with its site of origin.
Spin Delocalization in the Allyl and Ethyl Radicals
Authors: Lazdins D. , Karplus M.
Published: January 2005

An analysis is made of pi-electron spin delocalization into the methyl-group hydrogen pseudo pi orbital of an ethyl radical. Configuration-interaction molecular orbital theory with semiempirical integral parameters is employed to achieve a separation of the exchange polarization and the electron-transfer contributions. A set of calculations for the allyl-type radical (Ċ3–C2=C1), which serves as a simpler model for the ethyl radical (Ċ3–C2=H31), shows that essentially equivalent results are obtained from treatments with and without overlap. In the ethyl calculation without overlap, as well as in the allyl studies, it is found that both pi-electron exchange polarization and electron transfer are important, with the former contributing ∼60% and the latter ∼40% to the spin delocalization. A perturbation treatment is introduced to evaluate the dependence of the results on values of the integral parameters; it is shown that the relative contributions of exchange polarization and electron transfer are rather insensitive to the parameter values, although the two types of electron-transfer terms (into and out of the methyl group) are individually dependent on the electronegativity difference between the carbon pi orbital and the methyl group. The results demonstrate that neither a simple valence bond treatment (which is based on an exchange polarization mechanism) nor a simple Hückel calculation (which is constructed from electron-transfer terms) provides by itself a completely satisfactory description of spin delocalization in these systems.
Space Charge in Growing Oxide Films. V. Perturbation Coefficients and Second-Order Treatment
Authors: Fromhold A. T. , Graf E. R.
Published: January 2005

The coefficients in a previously developed perturbation treatment of space-charge effects for growing oxide films are explicitly evaluated in terms of the boundary concentrations of the diffusing species. The quadratic forms for the coefficients in terms of concentrations of ions and electrons makes quantitative comparison of theory and experiment possible, and facilitates the development of analytical approximations for limiting cases. The perturbation treatment itself is extended to include higher-order terms. The resulting equations reduce to quadratures; numerical computations for a specific example are presented to compare first- and second-order results. An approximate equation L(t)=L∞′(1−exp{−(t/τ′)−[L(t)/L∞′]}) is thereby obtained relating film thickness L(t) to time t for the later stages of growth, with the parameters L′∞ and τ′ determined by the space-charge concentrations in the film. Dimensionless curves are presented which illustrate the relationship between this equation and the first-order equation L(t)2=L∞2[1−exp(−t/τ)].
Relationship Between Magnetic Curie Points and Cell Sizes of Solid Solutions with the Ordered Perovskite Structure
Authors: Galasso Francis S. , Douglas Frank C. , Kasper Robert J.
Published: January 2005

A study of Ba2xSr2–2xFeMoO6 solid solutions with the ordered perovskite structure showed that their Curie points increased nonlinearly as the amount of strontium increased while their cell sizes decreased with greater quantities of strontium. By substituting calcium for strontium in Sr2FeMoO6 a decrease in Curie point was observed as the cell size continued to decrease. Presented is the data observed and a consideration of the possibility that a maximum superexchange interaction energy exists between iron and molybdenum in Sr2FeMoO6 at a Fe–O–Mo bond distance of approximately 3.95 Å.
Kinetics of Desorption of the β-Nitrogen States Chemisorbed on Tungsten
Authors: Madey T. E. , Yates John T.
Published: January 2005

The kinetics of desorption of the strongly chemisorbed β1 and β2 nitrogen states on tungsten have been studied. Independent techniques of isotopic mixing and flash-filament desorption have been employed. The rate of production of 14N15N (g) from 14N2(g) and 15N2(g) in a steady-state flow experiment is completely accounted for by the kinetically determined rate of desorption from the chemisorbed layer. β1-nitrogen appears to desorb by first-order kinetics; β2-nitrogen desorbs in a complex manner with higher-order kinetics. The apparent β2 desorption order decreases markedly as temperature increases. A superposition of two or more unresolved substates in the β2 state is postulated. The temperature variation of desorption order can be accounted for by a lack of achievement of equilibrium between the spatially separate β2 substates during desorption at scan rates of 12.5°K/sec or greater.

Above 1500°K, where the steady-state coverage of nitrogen is very low, a sticking coefficient of less than 0.02 has been measured. The sticking coefficient is nearly constant in the range 1500°—1700°K and over a 25-fold pressure range.
Ag I and Ag III from Solvated Ag II by Radiation-Chemical Conversion in γ-Irradiated Solutions at 77°K
Authors: Shields L.
Published: January 2005

EPR evidence is advanced for the radiation-chemical production of silver I and silver III complexes from silver II salt solutions frozen in liquid nitrogen. The complexes are distorted from cubic symmetry by way of an extension along one polar axis.
Line Shape of 14N Pure Quadrupole Resonance by the Zeeman Modulation
Authors: Negita Hisao
Published: January 2005

The Zeeman patterns for 14N pure quadrupole resonances in powders have been deduced, calculating the relative intensities around the resonance frequencies. The shape of the resonance curve to be recorded can be found by the difference between the unperturbed and perturbed lines. When the asymmetry parameter η has a finite value, the recorded peak shifts from the unperturbed position. This effect is more evident for the weaker modulation field or the broader unperturbed line, and also for larger values of η. Furthermore, it is shown that the higher resonance line is much stronger than the lower, when η is large.
Optical and Paramagnetic Properties of Iron Centers in Quartz
Authors: Lehmann Gerhard , Moore Walter J.
Published: January 2005

Several different paramagnetic centers have been identified and studied in specimens of natural and synthetic α quartz. The dominant feature of the EPR spectrum of natural amethyst and citrine is a center S1, which was previously identified as substitutional Fe3+ with a charge-compensating alkali-metal ion on a neighboring interstitial site. Synthetic brown and green quartz also contain a small proportion of S1 centers, but the dominant feature of their EPR spectra is a center I which is identified as an interstitial Fe3+ lying in one of two possible interstitial sites in the structure, with a charge neutralizing ion in a neighboring substitutional site. This spectrum is fitted to a spin Hamiltonian with D=2.333 Gc/sec, E=0.63 Gc/sec, F=0.60 Gc/sec, the z axis of the center coinciding with the c axis of the crystal. Interconversion of S1 and I centers by heat treatment indicates that the latter are more stable. In a crystal of synthetic amethyst, a new EPR center, denoted S2, has been characterized, which is converted to S1 by annealing at 350° and obtained from S1 by irradiation with x rays. Citrine and heat-treated amethyst display a broad isotropic EPR absorption at g=2, believed to be caused by nuclei of precipitated Fe2O3. The brown color is partly due to these inclusions and partly to a shift of the charge-transfer band [Fe3++O2—→Fe2++O−] into the visible as S1 centers are converted to less constricted I centers.
Electron Traps in Deformed Alkali Halide Crystals
Authors: Hirai Masamitsu , Scott Allen B.
Published: January 2005

Additively colored KBr and KCl crystals were deformed at room temperature, illuminated with F light at −140° and −120°C, respectively, to produce F′ centers and then warmed from −186°C to room temperature. Absorption spectra were obtained at a series of temperatures during warming. Curves of absorption in the region of the F′ band vs temperature showed two temperature regions in which the absorbance decreased rapidly, corresponding to the decomposition of two sets of centers of differing thermal stability. Undeformed crystals displayed only one such temperature region, in which ordinary F′ centers were destroyed. The centers in deformed crystals may be F′ centers whose stability is either increased or decreased by the influence of neighboring dislocations. In deformed KCl a new center, absorbing near 1500 mμ and more stable thermally than F′ centers, was found.
On the Rotational Diffusion of Molecules
Authors: Gordon R. G.
Published: January 2005

The Debye model of rotational diffusion by small angular steps is generalized to allow molecular reorientation through angular steps of arbitrarily large size. The generalized diffusion models are found to give a rather accurate representation of molecular reorientation in liquids and gases, as observed in the infrared and Raman spectra of simple molecules. One interesting feature of both the theoretical and experimental correlation functions is that the approach to rotational equilibrium often takes the form of a damped oscillation, rather than the monotonic decay which is usually assumed.
Semiempirical Molecular Orbital Calculations. I. The Electronic Structure of H2O and H2S
Authors: Carroll D. G. , Armstrong A. T. , McGlynn S. P.
Published: January 2005

The results of calculations of the molecular orbitals of H2S and H2O are reported. The molecular orbital energies were obtained at the self-consistent charge distribution, from the secular equation |Hij−EGij|=0.An open-shell treatment of the oxygen and sulfur p orbitals was used, together with the relationship, Hij=(2−| Sij | )(Hii+Hjj)Gij/2 for the resonance integrals. The orbital energies agree very well with those from ab initio calculations and the method should prove useful with larger molecules where a more sophisticated treatment is not feasible.
Gas-Phase Radiolysis of Cyclopentane. Relative Rates of H2−-Transfer Reactions from Various Hydrocarbons to C3H6+
Authors: Doepker R. D. , Ausloos P.
Published: January 2005

The radiolysis of cyclo-C5D10 has been investigated in the presence of various saturated and unsaturated perprotonated hydrocarbons. On the basis of the isotopic analysis of the propanes formed in these mixtures and several other experimental observations it is concluded that the C3D6+ ion, which is the major ion produced in the fragmentation of C5D10+, reacts with various saturated hydrocarbons (AH2) as follows: C3D6++AH2→CD3CDHCD2H+A+.Rates of this process relative to that of the reference reactionC3D6++cyclo−C5D10→C3D8+C5D8+have been measured with an accuracy of better than 2%. It is suggested that the saturated hydrocarbons also transfer an H− ion to C3D6+ according to the following reaction: C3D6++AH2→C3D6H+AH+.Although in agreement with theory the total rate of reaction of C3D6+ with AH2 is generally seen to increase with an increase in molecular weight of AH2, there are appreciable variations in the rates of the H2− transfer reaction (a) versus that of the H−-transfer reaction (c) with a change in structure of the hydrocarbon molecule. Reaction (c) is usually favored when AH2 is a branched hydrocarbon, except for neopentane which is entirely unreactive toward C3D6+. Unsaturated hydrocarbons do not transfer an H2− ion to C3D6+ but probably undergo a condensation-type process. The radiolysis of cyclopentane has also been investigated in the presence of O2, NO, and (CH3)3N. It is demonstrated that the C3H6+ and C5H10+ ions transfer their charge to NO, or (CH3)3N and that at a pressure of 20 torr approximately 20% of the parent ions undergo ring opening prior to the charge-transfer process.
Molecular Rainbows for the 12–6 Potential in the Airy Approximation
Authors: Mason E. A. , Munn R. J. , Smith Francis J.
Published: January 2005

Numerical values are given for those quantities needed to describe molecular rainbow scattering in the Airy approximation, for the 12–6 potential. These are the value of the rainbow angle and the curvature of the deflection function at the rainbow angle; some values of the third derivative are also presented. An example is given of the determination of the potential parameters ε and σ from just the measured angular positions of the first maximum and minimum in the differential cross section.
Photoionization Mass Spectrometry of NO
Authors: Reese R. M. , Rosenstock H. M.
Published: January 2005

The photoionization efficiency curve of the NO molecule has been measured in the range 1360–600 Å, and the autoionization structure compared with the absorption spectrum. A number of plausible vibrational progressions are suggested in the 1130–900 Å range.
Kinetics of Unimolecular Breakdown. II. Time-Dependent Theory
Authors: Levine R. D.
Published: January 2005

The solution of the Schrödinger time-dependent equation is discussed in a form suitable for chemical kinetics. The evolution of the system is considered with respect to the simultaneous evolution of independent events and the sequence evolution of events.

The lifetime is defined as the average duration of an event. It is shown to be the inverse of the rate constant for the activated states. The distinction between unimolecular and bimolecular reactions is discussed and the realization of genuine termolecular processes is considered.
Transient Nutations in Nuclear Magnetic Double Resonance. Assignment of Transitions to an Energy-Level Diagram
Authors: Ferretti James A. , Freeman R.
Published: January 2005

A nuclear magnetic double resonance technique is described which permits the assignment of transitions of complex high-resolution spectra to the appropriate energy-level diagram. A monitoring radio frequency (H1 at ω1) is maintained at exact resonance for a chosen line in the spectrum with the level H1 set well above saturation, while a second radio frequency (H2 at ω2) of about the same strength is swept through the entire spectrum. A transient nutation of the type described by Torrey is detected whenever ω2 passes through a line that shares an energy level with the monitored transition. This is attributed to the sudden transfer of spin population to the common energy level as a result of population inversion across the connected transition caused by adiabatic passage through resonance. The new magnetization vector then precesses around H1 in the rotating frame of reference, giving the characteristic decaying oscillation first observed by Torrey. This transient oscillation is positive going when the two connected transitions span an interval Δm = 2 (the ``progressive'' configuration), and negative going when they span an interval Δm = 0 (the ``regressive'' configuration), thus making a clear distinction between these two possibilities. The technique is illustrated by transient double resonance experiments on 2-chlorothiophene.
Salt Effects in the Reaction of Peroxydisulfate with Thiosulfate
Authors: Indelli Antonio , Bartocci Vito , Ferranti Francesco , Lucarelli Maria G.
Published: January 2005

It can be deduced from a comparison of the salt effects in the reactions of persulfate with thiosulfate, of bromoacetate with thiosulfate, and of ethyl oxalate with hydroxide ions that the first of these reactions is subject to nonelectrostatic effects of great magnitude. The differences in the relative effects of the alkaline and of the alkaline-earth ions in the three reactions is attributed to the different hydration properties of the ion pairs in each case. In particular, it is concluded that the ion pairs with the hydroxide ion are formed without the intervention of water of hydration. The specific salt effects of various organic ions on the reaction between persulfate and thiosulfate are discussed on the basis of the mechanism of the nonelectrostatic effects.
Comparison of Experimentally Derived and Theoretically Calculated Derivatives of the Energy, Kinetic Energy, and Potential Energy for CO
Authors: Schwendeman R. H.
Published: January 2005

Theoretical values of the energy, kinetic energy, and potential energy obtained recently by approximate Hartree—Fock calculations by Nesbet for N2, CO, and BF have been used to obtain values of the derivatives of these quantities. Using equations obtained by differentiation of the virial-theorem expression for diatomic molecules and experimental values of Be, ωe, ωexe, and αe, experimental values of the derivatives of E, T, and V have also been obtained. The probable accuracy of the power-series expansions in internuclear separation which are used to represent the computed energy values is considered, as is the choice of the value of the internuclear separation at which the derivatives are evaluated. The experimentally derived and theoretically calculated derivatives are compared. A corresponding comparison of derivatives of the energy of CO and BF is made using the results of the more elaborate approximate Hartree—Fock calculations reported by Huo. It is shown from Nesbet's data that potential constants obtained from derivatives of the kinetic energy or potential energy are as precise as those obtained from derivatives of the energy.
Random-Walk Model of Adsorption of a Chain-Polymer Molecule on a Long Rigid-Rod Molecule
Authors: Rubin Robert J.
Published: January 2005

A lattice model of adsorption of a flexible chain molecule on a rodlike molecule is investigated. The rodlike molecule is represented by the lattice sites on the z axis of a simple-cubic lattice; sites which are nearest neighbors to the z axis are adsorbing sites. The dimensionless adsorption energy per monomer unit is θ = ε/kT. The problem of enumerating polymer-chain configurations taking into account the increased probability of occupying adsorbing sites and the zero probability of occupying z-axis sites is formulated and solved as a random-walk problem. This model is a natural generalization of a random-walk model of adsorption on a plane solution surface. The average fraction of monomer units in adsorbing sites fR(θ) is computed in the limit in which the number of monomer units in the polymer chain approaches infinity. There is a critical value of the adsorption energy θc = ln (6/5) such that for θ<θc, fR(θ) = 0. For θ>θc, fR(θ) is an increasing function of θ with all derivatives equal to zero at θc = ln (6/5). In the analogous simple-cubic model of adsorption of a polymer-chain molecule at a plane solution surface, the same value of the critical energy has been obtained. For θln (6/5), fS(θ) is an increasing function of θ whose right-hand slope is 25 at θ = ln (6/5).
14N Hyperfine Structure in ESR Spectra of Heterocyclic Anions
Authors: Henning J. C. M.
Published: January 2005

ESR spectra of the anions of several aromatic heterocyclics, containing nitrogen, have been recorded with the object of correlating the observed nitrogen hyperfine splittings with the π-electron spin-density distributions.

As a result of this analysis it is found that the 14N hfs splitting constant (AN) depends not only on the π spin density at the nitrogen site (ρNπ) but also on the π spin densities at the nearest-neighbor carbon atoms (ρC1π and ρC2π, respectively).

If, to a first approximation, the relationship is written as AN=QNNNρNπ+QCCN(ρC1π+ρC2π),where C1 and C2 are the two nearest neighbors of N, the coupling factors QNNN and QCCN are found to be +19.1±1.7 and +9.1±1.7 G, respectively.
On the Kinetic Theory of Dense Fluids
Authors: Hurt Norman , Rice Stuart A.
Published: January 2005

In this paper we analyze the Rice—Allnatt kinetic equations using a formal perturbation expansion in which the lifetime of dynamical coherence plays a fundamental role. It is shown that:

(a) In the limit of short dynamical coherence time, the Rice—Allnatt equations are a valid description of steady-state transport phenomena in a liquid,

(b) The Kirkwood time-smoothing hypothesis is a natural expression of the nature of the coherence time expansion,

(c) The use of a separable intermolecular potential, the instantaneous nature of rigid-core collisions, and the nature of time smoothing all have interesting consequences for the derivation of Markovian kinetic equations from the Liouville equation.
Chemisorption Studies of Nitrogen on Polycrystalline Tungsten
Authors: Hill M. P. , Lecchini S. M. A. , Pethica B. A.
Published: January 2005

The effect of nitrogen adsorption on the thermionic emission from a polycrystalline tungsten ribbon has been measured in the accelerating region both at high and low applied fields. The results have yielded information on the behavior of the work function of (100) and (111) planes towards nitrogen adsorption.

The thermionic-emission data have been compared with average work-function changes measured using a diode operating in the space-charge-limited region.

The work-function data combined with adsorption kinetics and with thermionic-emission changes during desorption have confirmed that on chemisorption:

(i) (100) planes show a decrease in the work function and have a higher sticking probability and lower heat of adsorption than (111) planes.

(ii) Conversely, (111) planes show an increase in the work function and have a lower sticking probability than (100) planes. At high temperatures nitrogen desorbs preferentially from (111) planes, and moreover the order of desorption from the two planes is different.

An initial adsorption at coverages less than 4×1013 atom/cm2, occurring on highly reactive sites tentatively associated with defects and crystallite edges has been found to increase the work function.
Three-Body Effects in Physical Adsorption
Authors: Wolfe Robert , Sams John R.
Published: January 2005

Third-order interaction data for argon, krypton, xenon, methane, and tetradeuteromethane on the highly graphitized carbon black P33(2700°) are analyzed by means of a two-dimensional model which specifically includes a term to account for three-body forces. The intermolecular pair potential in the gas phase is taken to have the Lennard-Jones (12, 6) form, and when the molecules are adsorbed in a monolayer we assume this potential to be modified by the addition of a repulsive three-body term proportional to r−3. For a given set of bulk-gas potential parameters the proportionality constant η in the r−3 term can be uniquely determined from the data, although η is found to be quite sensitive to the exact choice of bulk parameters. Three different theoretical formulas for η give only qualitative agreement with the empirical values. Surface areas determined from the data are insensitive both to the bulk-phase parameters and to the exact nature of the interaction model. Effective two-dimensional potential parameters for the (12, 6, 3) model differ by < 10% from the gas-phase parameters for all the systems studied, indicating that three-body effects in physical adsorption may be smaller than previously supposed.
Photolysis of Liquid Water at 1470 Å
Authors: Sokolov Uriel , Stein Gabriel
Published: January 2005

The photolysis of water and of dilute aqueous solutions of O2, methanol, ethanol, and isopropanol was studied at 1470 Å. The results are consistent with the reaction scheme[Complex chemical formula]The limiting quantum yield for the formation of the geminate radical pair φ=0.7±0.1 at room temperature. Scavengers compete in an inhomogeneous kinetics with geminate recombination. The direct formation of molecular products other than by radical mechanisms is excluded. Results on D2O solutions of ethanol support the conclusions. The evidence does not favor direct interaction of scavengers with the excited water molecules H2O‡.
Gaseous Thermal Electron Reactions: Attachment to SF6 and C7F14
Authors: Mahan Bruce H. , Young Charles E.
Published: January 2005

The rates of attachment of thermal gaseous electrons to sulfur hexafluoride and perfluoromethylcyclohexane have been measured using a microwave cavity resonance technique. The measurements are compared to the results of recent electron-beam work. The rate constants for attachment to SF6 and C7F14 are, respectively, 3.1×10−7 and 9.8×10−8 cc/molecule·sec. The former rate constant decreases and the latter slightly increases as the electron temperature is raised.
Crystal Structure of Paramagnetic Ludlamite, Fe3(PO4)2·4H2O, at 298°K
Authors: Abrahams S. C. , Bernstein J. L.
Published: January 2005

Paramagnetic Fe3(PO4)2·4H2O is monoclinic, with lattice constants a=10.541±0.005, b=4.646±0.004, c=9.324±0.005 Å and β=100°25.8′±1.0′ at 298°K, with two formula weights in the unit cell. The space group is P21/a. The positions of the iron, phosphorus, and oxygen atoms, determined by Ito and Mori in 1951, together with those of the hydrogen atoms, have been refined by the method of least squares. The integrated intensities of 6212 reflections in a reciprocal lattice hemisphere of radius (sinθ)/λ=1.02 Å−1 were measured with PEXRAD; 1919 symmetry-independent F(hkl) were significantly above background. The final agreement factor between measured and calculated structure factors was 0.0336. There are two crystallographically unrelated iron atoms per unit cell, each occupying a distorted oxygen octahedron; the iron—oxygen distances range from 2.016±0.002 through 2.362±0.002 Å. The average distance is 2.156 Å. The phosphate group is very nearly a regular tetrahedron, the range in P–O distance being from 1.536±0.002 through 1.549±0.002 Å. The average O–H distance is 0.87 Å. The shortest O–H···O bond is 2.541±0.003 Å. One phosphate—oxygen atom forms no hydrogen bond, one forms two, and the remaining two oxygen atoms form one hydrogen bond each. The thermal vibrations are significantly anisotropic.
Correlation of the C–H Stretching Force Constant with the Nuclear 13C–H Coupling Constant
Authors: Brown Theodore L. , Puckett Janice C.
Published: January 2005

The characteristic CH3 stretching frequencies in a number of selected compounds in carbon tetrachloride solution have been measured and compared with the nuclear 13C–H scalar coupling constant, J. The correlation provides a basis for expressing the C–H stretching force constant Kr in terms of J. Using a modified valence-force-field potential function for the CH3 group, Kr=4.74+8.8×10−3 (J−125) mdyn/Å.

The orbital contributions to Kr have been examined theoretically. Variation in fractional s character in the carbon orbital to hydrogen does not, of itself, lead to a significant variation in Kr. The force constant increases with increasing ionic character in the C–H bond, rather than as a result of hybridization changes.
Effect of Volume Exclusion on the Dimensions of Polymer Chains
Authors: Flory Paul J. , Fisk Stephen
Published: January 2005

The effect of volume exclusion on the mean-square radius of gyration s2 is treated by use of the empirical expression W0(s)=const s6exp[−(7/2)〈s2〉0−1s2] for the statistical distribution of s for a system of linear chain molecules unperturbed by volume exclusion. Segment interactions within the perturbed molecule are treated in the smoothed-density approximation. The result is α5—α3=Azh(z/α3), where α2=〈s2〉/〈s2〉0, A is a numerical constant, z is the usual parameter proportional to the excluded volume for a segment pair and to the square root of the chain length, and h(ζ) is a function which decreases by almost one-half as ζ increases from 0 to ∞. Asymptotic dependence of α2 on the ⅕th power of the chain length is thus confirmed. Extremely long chains, exceeding 106 bonds, would be required however for realization of this limiting behavior.
Mixtures with Weak Long-Range Forces
Authors: Hauge Eivind Hiis
Published: January 2005

Mixtures with interactions consisting of a strong repulsion of short range and a weak long-range attraction are studied. Results to the first order in an expansion parameter defined essentially as the ratio between the volume of repulsion and the volume of attraction are given for the correlation function and the equation of state. The basis for a numerical treatment of the results is outlined.
Thermoluminescence in Vitreous Sodium Silicate
Authors: Bettinali C. , Ferraresso G.
Published: January 2005

Vitreous sodium silicate has two quite distinct thermoluminescence maxima between 20° and 250°C, each having its own spectral composition (about 420 and 515 mμ, respectively). The peaks have equal activation energies (about 0.8 eV). It seems likely that, between 20° and 250°C, the thermoluminescence emission model for vitreous sodium silicate is a recombination of electrons trapped in a single energy level, with centers that probably consist of positive holes having different capture cross sections.

For the low-temperature thermoluminescence, Kikuchi's suggestion appears to have been confirmed.
Ion—Molecule Reactions between H3+ and Saturated Hydrocarbons
Authors: Aquilanti V. , Volpi G. G.
Published: January 2005

The ion—molecule reactions of H3+ and D3+ with methane, ethane, propane, isobutane, and n-butane have been studied by high-pressure mass spectrometry, using an ion source which employs the beta rays of tritium as the ionizing medium.

The rate constants have been measured, and proton transfer has been shown to be the major mode of interaction. If not stabilized by collision, protonated methane and protonated ethane decompose by elimination of hydrogen, with a lifetime of the order of 1 and 10−1 μsec, respectively. Protonated propane and protonated butanes, which have not been detected as stable species at pressures as high as 0.3 torr, decompose by elimination of hydrogen or a smaller saturated hydrocarbon to give an alkyl carbonium ion. Some results concerning the reactivity of these alkyl ions with deuterium and the hydrocarbons are also reported.
Gas—Gas Equilibria
Authors: de Swaan Arons J. , Diepen G. A. M.
Published: January 2005

This article deals with a remarkable phenomenon in chemical-phase theory, i.e., the limited mutual solubility of gases, which was predicted by van der Waals and first demonstrated by Krichevskii in the nitrogen—ammonia system. The phase behavior in question is characterized by a peculiar course of the critical locus in some systems for which the components have a considerable difference in volatility. Under special conditions such a system showing limited miscibility may also exhibit the barotropic phenomenon, i.e., the equilibrium phases change position in the gravitational field.

Using the conditions Temkin derived from van der Waals' applications of Korteweg's fold theory, we could predict that the helium—xenon system probably exhibits gas—gas equilibria. We have confirmed the predicted behavior by visual observations of phase transitions in helium—xenon up to 2000 atm and 65°C.
Stress Relaxation and Creep in Dilute Polymer Solutions
Authors: Tschoegl N. W.
Published: January 2005

From the Rouse—Zimm theory for the viscoelastic properties of dilute polymer solutions, stress relaxation curves were computed for vanishing and for dominant hydrodynamic interaction. The results were converted numerically to creep data by the method of Hopkins and Hamming. Since the steady-state compliances and steady-flow viscosities can be calculated separately, computation of the creep curves afforded a check on the accuracy obtainable with the Hopkins—Hamming method. The primary interest of this work lies in its relevance to the stress relaxation and creep behavior of undiluted bulk polymers.
Conformations of the Free Radical in Irradiated α-Aminoisobutyric Acid
Authors: Box Harold C. , Freund Harold G.
Published: January 2005

The electron paramagnetic resonance spectrum of x-irradiated α-aminoisobutyric acid was studied in single crystals irradiated at 77°K and allowed to warm up gradually. Different conformations of the free-radical (CH3)2CCOOH were observed. The g tensor and the hyperfine splitting tensor were determined for each conformation.
Reduction Parameters for an Unspecified Intermolecular Potential. A Harmonic-Oscillator Approximation
Authors: Walkley John
Published: January 2005

The reduction parameters for an unspecified pair interaction potential have been calculated for argon and krypton. The method used is a sphericalized equivalent of the method first proposed by Corner. It is similarly limited, but only in the present harmonic version, to systems for which the zero-point energy is very small. The parameters obtained from solid-state data allow an extremely accurate corresponding states comparison of second virial coefficient data. Third virial and also viscosity data similarly appear to be reduced to single classical curves. This suggests that any nonadditivity of potential present in the multiparticle-interaction situation of the solid phase must be very small.
Fluorescence and Internal Conversion in Naphthalene Vapor
Authors: Watts Richard J. , Strickler S. J.
Published: January 2005

The fluorescence spectrum of naphthalene vapor has been investigated upon excitation in the second excited singlet state. Although no collisions occur during the lifetime of the second excited state, fluorescence is observed to originate in the first excited state, indicating that internal conversion is an intramolecular process in this case. The intensity of fluorescence from the second excited state is established to be not more than 0.002 of that from the first state. Some comments are made on the theory of radiationless transitions.
Some Applications of the R-Matrix Theory to Reactive and Elastic Molecular Scattering
Authors: Eu Byung Chan , Ross John
Published: January 2005

Wigner's R-matrix theory of collisions is applied to three topics in molecular scattering. We present sufficient conditions for a derivation of an activated-complex theory of chemical reaction rates, and of a statistical theory of reactive collisions. In the statistical theory we find that the natural choice of the probability of decay of the collision complex into a given channel of the reaction product is a quantity proportional to the rate of production in that channel. Different assumptions have been made in the literature on the removal of the dynamics from the probability of decay, and a brief comparison is presented. A connection is noted between the activated-complex and the statistical theory. Last, we discuss resonances in the total cross section for elastic scattering at low relative kinetic energy. Some illustrative calculations are made with the Breit—Wigner one-level formula and the WKB approximation for the eigenstates of the collision complex.