bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Theory of Dense Fluid Mixtures. II. Solution to the Singlet Distribution Functions for the Rice—Allnatt Model
Authors: Wei Ching Cheng , Davis H. Ted 
Published: January 2005

The Rice—Allnatt theory of dense fluids has been extended to binary mixtures. It is shown that the linearized Rice—Allnatt equation for the singlet distribution function is a linear integral equation of the second kind. Moreover, it is shown that a simple modification of the Rice—Allnatt equation, the modification being of the same order of approximation as those utilized in deriving the equation, results in a linear equation admitting mass, momentum, and kinetic energy as homogeneous solutions, thus allowing the local hydrodynamic variables to be completely specified by the zero-order solution to the integral equation.
The singlet distribution functions are solved, and the binary diffusivity, thermal diffusion ratio, and kinetic contributions to thermal conductivity and viscosity are obtained.
Quantum Theory of Interference and Polarization of Stark—Zeeman Lines in Molecules
Authors: Chiu Ying-Nan 
Published: January 2005

With special emphasis on the application to transitions between the rovibronic states of molecules, general formulas for the polarization and for the intensity inclusive of interference of multipole emission between Stark—Zeeman levels are derived. The derivation makes use of angular momentum method for molecules and irreducible spherical tensor operators for the interaction of radiation and matter.
Results are made applicable to linearly polarized radiation with any arbitrary orientation (specified by three Euler angles) of the polarization and propagation vectors with respect to the space-fixed axes. These higher multipole interference effects in a resolved molecular Stark—Zeeman line serve as an extension of the pioneer works on atomic Zeeman transitions of Van Vleck and others. The formulas are tabulated in terms of their dependence on reduced rovibronic matrix elements and their rotational and angular dependence. For the latter dependence that involve products of Clebsch—Gordon coefficients and products of rotational matrices we give explicit examples up to electric and magnetic octopole radiation. Rotation matrices of the third rank, some of which are needed in transitions involving octopole, are computed and tabulated. For the former dependence, general line strengths of linear molecules and rovibronic matrix elements are given with all dependence on rotational wavefunction evaluated, for any Hund's Case a states inclusive of the hypothetical Σ2s+1Ω±(a) states, singlet Case b states, and doublet Σ±(b) states. For diatomic molecules of half-integral spin (even multiplicity), general Case a and b state wavefunctions are constructed, their symmetry under inversion and selection rules are derived. Specific examples are given of the magnetic-dipole—electric-quadrupole radiation in ∏2,412(a)−∏2,412(a) and ∑2±−∏2,434(a) transitions, and of the electric-dipole—magnetic-quadrupole—electric-octopole radiation in ∏2,4,632(a)−∏2,4,632(a) transitions. Attention is called to the existence of cross terms which make the formulas dependent on different Λ-doubling components and hence on the ``Kronig reflection'' symmetry specified by a (±) sign.
Ternary Excess Enthalpies in Simple Reciprocal Fused-Salt Mixtures. III. Effect of Ionic Size
Authors: Meschel S. V. , Toguri J. M. , Kleppa O. J. 
Published: January 2005

Calorimetric measurements are reported on the enthalpies of mixing in the reciprocal system Ag+–Cs+–NO3−–Cl− at 350° and in the systems Li+–Cs+–Cl−–Br−, Na+–Rb+–Cl−–Br, and Na+–Cs+–Cl−–Br− at more elevated temperatures. These results, when compared with data for the binary systems involved, permit an evaluation of the ternary excess enthalpies.
It is found that these excess enthalpies are all negative and of an order of magnitude consistent with the predictions of quasichemical theory. This suggests that they in the main are due to deviations from random mixing of the ions. The deviations from quasichemical theory show a nearly linear correlation with the difference in ionic size of interchangeable ions in the mixture.
Stress-Optical Coefficient of Poly-(dimethylsiloxane) Networks
Authors: Nagai Kazuo , Ishikawa Toshihide 
Published: January 2005

An expression in matrix form for the optical anisotropy ΔΓ of Kuhn's random link (an equivalent to the stress-optical coefficient) of two-repeat polymers is derived, based on the additivity principle of bond polarizabilities and the rotational-isomeric-state approximation. The interdependence of neighboring-bond rotations is taken into account.
Stress-optical data of poly-(dimethylsiloxane) networks are analyzed by assuming rotational states to be three in number, i.e., trans (T), gauche (G), and gauche prime (G′). It is found that semiquantitative agreement is achieved by assuming EG&gt;0 and Δαe&gt;0. Here EG is the energy of the gauche conformation relative to that of the trans, and Δαe=(α1−α2)Si–O−(α1−α2)C–Si+(α1−α2)C–H is the ``effective'' anisotropy of the Si–O bond. A harmonized choice of values of θ(G) the internal-rotational angle for the gauche conformation, and ω1, the supplement to ∠SiOSi, is needed for interpretation of two items of ΔΓ/Δαe and 〈r2〉/nb2, the latter being the characteristic ratio for the unperturbed dimension. Definite conclusion could not be obtained about to what extent the GG′ conformations for neighboring bonds are suppressed.
Far-Infrared Spectrum and Hindering Potential of Deuterium Peroxide
Authors: Hunt Robert H. , Leacock Robert A. 
Published: January 2005

The hindered-rotation motion in the deuterium peroxide molecule is investigated through a study of the far-infrared absorption of the vapor. A 1-m focal-length vacuum grating spectrometer was used to scan the region from 20 to 400 cm−1 with an average resolution of 0.4 cm−1. Seven perpendicular-type hindered-rotation bands characterized by prominent Q branches and unresolved P- and R-branch structure are observed in the spectrum. The band centers are located at 1.88, 42.3, 123.5, 136.8, 206.7, 250.9, and 302.6 cm−1. From these it is determined that, relative to the ground state, the first five excited hindered-rotation states are at 1.88, 208.6, 250.9, 387.7, and 511.2 cm−1.
A theory of internal rotation, developed for an earlier application to the far-infrared spectrum of hydrogen peroxide, is applied to the D2O2 spectrum. In this theory the only internal degree of freedom is the dihedral angle x defining the relative position of the two OD groups. The Hamiltonian is put in the form H (asymmetric top) +H (internal rotation), where the inertial coefficients are functions of the internal angle x. A three-parameter hindering potential is assumed, V(x)=V1cosx+V2cos2x+V3cos3x and the internal-rotation wave equation is solved numerically by computer to obtain the potential parameters which reproduce the internal-rotation energy eigenvalues. In the semirigid model adopted, the effective hindering potentials, bond lengths, and bond angles of H2O2 and D2O2 differ slightly. The data do not yield a complete set of effective bond lengths and angles for D2O2, but the product of the OD distance and the sine of the OOD angle is found to be 0.01 Å smaller than its H2O2 counterpart. As a result, the inertial parameter in the internal-rotation wave equation is 2% larger than is predicted from the H2O2 data. Using this adjusted inertial parameter, the hindering potential V(x)=994cosx+641cos2x+55cos3x provides a good fit to the D2O2 data. For this potential function the cis and trans potential barrier heights are 2470 and 377 cm−1, respectively, and the potential minima are 110.8° from the cis configuration. These parameter values are similar to the corresponding H2O2 values of 2460 cm−1, 386 cm−1, and 111.5°.
Mass-Spectrometric Studies at High Temperatures. XI. The Sublimation Pressure of NdF3 and the Stabilities of Gaseous NdF2 and NdF
Authors: Zmbov K. F. , Margrave J. L. 
Published: January 2005

A mass spectrometer has been used to study the sublimation of NdF3 and gaseous equilibria involving NdF3, NdF2, NdF, Nd, BaF, and Ba.
The sublimation pressure of NdF3 is given by the equation logPatm=[−(1.873±0.025)×104/T]+8.03±0.17,where 1383°&lt;T&lt;1520°K. The heat of sublimation of NdF3 at 1448°K is 85.7±1.1 kcal mole−1.
Studies of the equilibria among gaseous species over the mixtures Nd+BaF2 and Nd+NdF3 yielded the heats of atomization of NdF3(g) and NdF2(g) and the heat of dissociation of NdF(g). The standard heat of formation of NdF3(s) is −399±10 kcal mole−1.
Shape of the Coexistence Curve of an Analytical Fluid in the Critical Region
Authors: Barieau Robert E. 
Published: January 2005

For an analytical fluid it is shown that the relationship between coexisting phases is given by a3=−a1(1+Ma1),where a3=(ρliq/ρc)−1,a1=(ρgas/ρc)−1,M=−4/15−13(paat/pat)+15(paaaa/paaa),p=(P/Pc)−1,and p with subscripts indicates partial derivatives of p evaluated at the critical point
Coexisting phases as a function of temperature are given by a1=(3Mpatt/paaa)−(−6patt/paaa)12,a3=(3Mpatt/paaa)+(−6patt/paaa)12,where t=(T/Tc)−1.
The reduced rectilinear diameter is given by [(a3+a1)/2]+1=1+(3Mpatt/paaa).
The reduced slope of the reduced rectilinear diameter is given by 12[d(a1+a3)/dt]=3Mpat/paaa.
Acceptor Action of Alkali Metals in II—VI Compounds as Detected by Electron Spin Resonance Techniques
Authors: Dieleman J. , de Jong J. W. , Meijer T. 
Published: January 2005

Experiments were performed to decide whether the introduction of alkali metals into II—VI compounds gives rise to the appearance of acceptor levels. In comparison with single crystals, powder samples are in most cases purer and it is much easier to dope powders rapidly and reproducibly. For that reason polycrystalline materials were used in this investigation. In order to obtain a quick and decisive answer to the above-mentioned question we used electron spin resonance techniques to study the influence of alkali metals on the Fermi level position in these samples. This requires at least one indicator, the presence of which can readily be detected by the employed techniques. For that purpose Fe was chosen since the valence change of divalent Fe to trivalent Fe, caused by the introduction of lower-lying acceptors, is easily detected at 77°K due to the appearance of the electron spin resonance signal of the trivalent Fe. The use of Fe as an indicator has the additional advantage of setting an upper limit to the depth of the acceptors introduced by the alkali metals, since the position of the Fe level is quite accurately known.
If no acceptors were introduced the Fe was found to be introduced in the divalent form under the preparation conditions chosen and no resonance of trivalent Fe was detected. The simultaneous introduction of the alkali metals Li or Na in ZnS, CdS or ZnSe caused the appearance of resonances due to trivalent Fe. These results unequivocally show that these alkali metals introduce acceptor levels into the lattices investigated. The upper limit to the acceptor depth (optically, with respect to the valence band) are 1.4 eV for cubic ZnS, 1.3 eV for hexagonal CdS, and 1.1 eV for cubic ZnSe. The increase in the amount of Fe that is converted to the trivalent form by the introduction of the alkali metals on going from ZnS to CdS or ZnSe is discussed and explained in terms of the decreasing energy needed to ionize the electron from Fe centers into the conduction band.
Appraisal of Some One-Center Calculations for the Neon- and Argonlike Series of Molecules
Authors: Hake R. B. , Banyard K. E. 
Published: January 2005

The united-atom (UA) method and the self-consistent-field one-center-expansion (OCE) treatment have been applied recently to the study of neonlike and argonlike molecules, namely, HF, H2O, NH3, NH4+, CH4, HCl, H2S, PH3, PH4+, and SiH4. In the present article, the values of physical properties predicted by each method are compared with the corresponding experimental quantities. For each molecule, comparisons with experiment have been made for the molecular energy, theoretical bond lengths, ``breathing'' force constants, and, for NH3 and PH3, the proton affinities. The radial density distribution of electrons, determined by us from the published OCE wavefunctions, has been used to calculate the coherent x-ray scattering factor for the gaseous state of each molecule. The electron densities were also used to determine the purely diamagnetic contribution χr to the total molar magnetic susceptibility. A comparison was made with the corresponding UA results and with the available experimental quantities. From the trend shown by the relationship between the theoretical and ``experimental'' values for χr, it was possible, for a molecule with Td symmetry, to suggest a range of values for the diagonal components (gjj″) of the electronic contribution (g″) to the molecular rotational gyromagnetic tensor (g). Hence, for SiH4, it was suggested that −1.48 &lt; gjj″ &lt; −1.31. No experimental value for this quantity is known by the authors.
Although it is seen that the OCE results are, in most instances, superior to the results obtained from the UA approximation, the latter method still provides very useful results with comparatively little computation.
Multiple-Scattering Treatment of Low-Energy Electron-Diffraction Intensities
Authors: McRae E. G. 
Published: January 2005

A theory of intensities in the diffraction of low-energy (≲100-eV) electrons by crystals is formulated on the basis of Lax's multiple-scattering equations. The formulation is self-consistent and is thus applicable regardless of the magnitude of the atomic-scattering factor.
The qualitative conclusions of the theory are discussed in detail with reference to simplified model crystals. The theory predicts that the reflectivity curves (reflectivity associated with a given beam versus electron energy) should show two types of peaks in addition to the ordinary Bragg peaks: (a) a resonance peak in the specular reflectivity curve; (b) secondary Bragg peaks in all reflectivity curves. The resonance peak is predicted at an energy just below that of the first appearance of a nonspecular beam. It derives from multiple scattering in a single atom layer and is associated with a resonance (zero and phase discontinuity) in the effective field. The secondary Bragg peaks are predicted at energies given by conditions similar in form to the ordinary Bragg condition. They derive from multiple scattering between atom layers and are associated with the interference between four or more plane wave components of the effective field. Both types of peaks are prominent only when the atomic-scattering cross section is large. All qualitative results are illustrated by an exact numerical application to a model crystal of isotropic (s-wave) scatterers.
The relationship with existing theories is discussed. It is shown that the conventional modified kinematical approach to low-energy electron diffraction is a limiting case that is approached when inelastic scattering is dominant. It is also shown that when certain assumptions are introduced, the most important being that of neglecting intralayer multiple scattering and the ``two-beam'' assumption, the theory reduces to the Darwin dynamical theory.
Numerical Calculation of the Energy and Wavefunction of the Ground State of Beryllium
Authors: Kotchoubey A. , Thomas L. H. 
Published: January 2005

An algorithm for the numerical calculation of the energy and wavefunction of the lowest state of the beryllium atom has been developed and used on the IBM 7090/94 computer systems.
The method is variational in nature. Its object is to find the solution of proper symmetry of the time-independent, nonrelativistic Schrödinger equation for the beryllium atom, for which the energy is a minimum (most negative). The wavefunction in configuration space is expanded in terms of a sum of products of one-electron functions of a complete basis set. These basis functions are chosen to be hydrogenlike functions, all with the same exponential factor. The sum is truncated, and the coefficients are adjusted to minimize the energy, subject to the condition that the function has the symmetry required for a singlet state. Rotational symmetry conditions are also used, to restrict the function to correspond to an S state, thus decreasing the number of coefficients that must be evaluated. The coefficients of the expansion are determined by an iterative procedure rather than by direct solution of the variational equations. Two parameters are introduced in the algorithm. One is the result of transforming the Schrödinger equation to have a discrete spectrum, in which the eigenvalue of least magnitude corresponds to the lowest energy. The other parameter is introduced in order to shift the eigenvalue spectrum and increase the separation between the smallest eigenvalue and the next smallest, thus improving the convergence of the iteration process.
Using a 20-function basis, corresponding to eight s states and four p states, an energy of −14.6533 a.u. was found for the lowest state of beryllium. This value is an upper bound to the true eigenvalue of the Schrödinger equation, and has a relative error of about 0.10% with respect to the experimental estimate of the true eigenvalue.
Measurement of the Recombination of H and OH in γ-Irradiated Aqueous Systems
Authors: Hardwick Thomas J. 
Published: January 2005

Differences in radical and molecular yields in γ-irradiated light and heavy water solutions have been measured over the range of sulfuric acid concentration 0–0.8N.
Three new terms have been defined: GH* and GOH*, which represent the hydrogen atoms and hydroxyl radicals whose fate is to recombine to reform water; G—H2OI, which represents the gross number of water molecules decomposed into radicals. A model of radical formation and diffusion has been developed from which values of GH*, GOH*, and G—H2OI may be calculated from the experimental data.
Photoconduction and Cis-Trans Isomerism in β-Carotene
Authors: Rosenberg Barnett 
Published: January 2005

A discussion is given of some theoretical and experimental aspects of photoconductivity in β-carotene. It is shown that re-solidification of crystalline β-carotene results in the formation of a glass state which is photoconductive. The original all trans form is converted into a mixture of stereoisomers in the glass, and the appearance of the ``cis peak'' at 3500 A in the optical absorption spectrum is noted.
The photoconductive action spectrum of a sandwich-type cell of the β-carotene glass has a maximum in this cis peak region when the electrodes are biased in the forward rectifying direction. The interpretation given to this in terms of the triplet state theory of photoconduction is that intersystem crossing is more probable from the cis peak than from the first excited state. Some evidence exists from semiconduction and phosphorescence measurements that the active triplet state lies 3.0 ev above the ground state and thus falls in the region between the two singlet excited states. Thus, the temperature dependent Boltzmann factor may be largely responsible for the increase in intersystem crossing from the cis peak state.
The photocurrent in the back rectification direction is shown to be due to the light which is mostly transmitted through the glass and absorbed at the positive rear electrode. For strongly absorbed wavelengths the rectification ratio is 1.6×105.
The voltage dependence is described by the sum of a linear term and a three halves power term, the former of which dominates at low field strengths and low absorption of the exciting light. There is a linear dependence of the photocurrent upon intensity.
The similarity of the effects of cis-trans isomerization in phosphorescence and photoconductive studies strongly suggests that the intersystem crossing to the triplet state is the dominant element in common and is considered as strong corroborating evidence for the triplet state theory of photoconduction in organic materials.
Magnetic Properties of Water Molecule
Authors: Das T. P. , Ghose T. 
Published: January 2005

The mass susceptibility χ and proton magnetic shielding factor σ for H2O molecule are calculated using a localized electron pair LCAO MO wave function. The paramagnetic part of the susceptibility and a portion of the paramagnetic part of σ are calculated by a variational method used earlier for the H2 molecule. The relation of the present variational method to the methods employed by McGarvey and by Stephen is discussed in some detail.
The calculated value of χ is found to be —0.687×10—6 in very good agreement with the experimental value of —0.699×10—6. (In an earlier report [Bull. Am. Phys. Soc. Ser. II, 3, 372 (1958)] we stated the calculated value of χ erroneously as —0.692×10—6.) The calculated value of σ is, however, found to be only —0.85×10—5 in rather poor agreement with the experimental value of —2.97×10—5. The causes for this poor agreement are analyzed, and it is concluded that the main reasons are (1) use of a rather large ionic character (66%) for the OH bond obtained from a curve of electronegativity difference versus ionic character and (2) use of undistorted H-atom orbitals in the LCAO MO function. It is suggested that the calculated value of σ would improve in the right direction if the effective charge for the H-atom orbital were taken as greater than unity. The value of σ is recalculated with Ellison and Shull's ``approximate treatment'' wave function and found to be —1.31×10—5. The disagreement with experiment in this case is ascribed to cause (2).
Arguments are presented to show that more accurate values of σ for protons in a molecule can be obtained if in the Hamiltonian for the electrons the origin for the first-order perturbation term due to the magnetic field is taken at the centroid of the electronic charge rather than at any other point.
Hydrogen Bond: An Experimental Verification of the Double Minimum Potential
Authors: Bell Charles L. , Barrow Gordon M. 
Published: January 2005

The spectra of alcohols in the region of the first and second OH stretching overtone in solvents of various bonding strengths reveal a pair of solvent dependent absorption bands. These bands are shown to arise from an energy level splitting resulting from a double minimum in the potential energy curve for the proton. The form that the potential energy curve must assume to yield the observed spectra is such that the second minimum lies in the region of the v=2 vibrational energy level for ordinary hydrogen bonding situations. The higher overtone bands, particularly in strongly basic solvents, are characteristic of the broad potential well.
This observed splitting of the absorption bands of hydrogen bonded alcohols confirms the theoretical predictions of a double minimum potential energy function for the proton.