bluuebunny/crossref_metadata_2025 huggingface dataset:
Multicomponent Polyelectrolyte Solutions. Part III. Determination of Activity of KCl in Potassium Polyvinylsulfonate Solutions by Use of a Cation-Sensitive Glass Electrode
Authors: Imai Nobuhise , Eisenberg Henryk
Published: January 2005

The activities of KCl in potassium polyvinylsulfonate solutions have been investigated in cells without liquid junction as a function of temperature, electrolyte, and polyelectrolyte concentrations. Potassium-sensitive glass electrodes in conjunction with Ag–AgCl electrodes were used. Results are expressed in terms of the ratio of the derivative of the emf with respect to polymer molality, at constant KCl molality, and the derivative of the emf with respect to KCl molality, at constant polymer molality. The relation of this quantity to membrane-distribution coefficients is established and the results are compared with polyelectrolyte theory.
ESR Linewidths in Solution. I. Experiments on Anisotropic and Spin—Rotational Effects
Authors: Wilson Raymond , Kivelson Daniel
Published: January 2005

The linewidths of the hyperfine components of the ESR spectra of vanadyl acetylacetonate in liquid toluene have been measured as a function of concentration, temperature, and applied field. The g-tensor and hyperfine-tensor components have been determined and used, along with the spectral data, to determine the Debye rotational correlation time τR. This analysis agrees very well with the experimental observations. A residual linewidth, not dependent upon the above mechanism, and independent of nuclear quantum number and applied field, has been studied and found to vary as T/η, where η is the viscosity. This residual linewidth is ascribed to a spin—rotational interaction.
Reactions of Bromine Activated by Bromine−82m Isomeric Transition and Radiative Neutron Capture in Liquid and Solid Carbon Tetrachloride and n-Hexane
Authors: Merrigan Joseph A. , Ellgren William K. , Rack Edward P.
Published: January 2005

New methods have been developed for obtaining 82Br and 82Brm organic retentions produced by 82Brm isomeric-transition reactions and radiative neutron capture by 81Br, respectively. No isotope effect was found for 80Brm and 82Brm reactions activated by the (n, γ) process. The 82Brm (I.T.) 82Br process was found to produce 82Br organic retentions nearly twice as high as the 80Brm and 82Brm organic retentions produced by the (n, γ) process. Effects of solidifying samples indicate a clumping of bromine molecules upon freezing. Product analyses indicate similar reaction mechanisms for the (n, γ) and (I.T.) activated reactions.
Neutron Scattering in Stretch-Oriented Polyethylene
Authors: Myers W. , Summerfield G. C. , King J. S.
Published: January 2005

Measurements on stretch-oriented polyethylene held at 100°K have been undertaken in an attempt to clearly identify the frequency limit of the calculated stretch—bend acoustic mode. A simplified ``constant-Q'' scattering technique was used in order to isolate the longitudinal C–C–C motion. A frequency limit was observed at 525±15 cm−1. The persistence of the torsional mode response in the longitudinal experiment is unexpectedly large.
Calculation of Chemical Reaction Probabilities from Elastic Scattering Data
Authors: Rosenfeld J. L. J. , Ross J.
Published: January 2005

We discuss the validity of the expression PR(E,b)=1−[σobs(E,χ)/σ0(E,χ)]previously used in reactive systems of the kind A+BC→AB+C to evaluate the probability of reaction PR for given relative kinetic energy E and impact parameter b. The nonreactive differential scattering cross section σobs(E, χ) is derived from measurements as a function of the relative scattering angle χ and the elastic scattering cross section σ0(E, χ) is obtained from an exp−6 potential made to fit the observed scattering in angular regions apparently unaffected by reaction, as the rainbow region in some examples.

By using an optical model and assuming the validity of a semiclassical description, we show that this expression holds whenever | dPR/db |≪2k(π−χ)[1−PR(E,b)];  E=12μk2ℏ2.

The simple expression for the probability of reaction is also shown to be approximately valid in a first-order distorted wave approximation and random phase approximation for σ0(E, χ).
Theory of Work-Function Change on Adsorption of Polarizable Ions
Authors: Macdonald J. Ross , Barlow C. A.
Published: January 2005

We first point out and correct an error which occurred in an earlier, more approximate theory of the work-function change accompanying ion adsorption. Next, certain of the approximations of this earlier work are lifted to produce a more accurate theory. In particular, the adsorbed ions and their images in the adsorbent are no longer approximated as ideal dipoles. We employ results of recent exact calculations to obtain quite accurate expressions for the electric fields due to these nonideal dipoles and thus for the induced polarization associated with these fields. Furthermore, the images of induced dipoles are explicitly taken into account in their effect upon the self-consistent depolarizing field. This approach leads to a new expression for the effective dielectric constant of the adsorbed phase which takes cognizance of discreteness effects. Theoretical predictions are found to be in agreement with data for Cs+ and K+ on tungsten for small θ and may apply well up to θ≲0.6. Finally we discuss possible explanations for the discrepancies near θ=1.
Some Aspects of the Coulomb Hole of the Ground State of H3+
Authors: Lester William A. , Krauss Morris
Published: January 2005

The Coulomb hole for the linear and equilateral configurations of the ground state of H3+ is calculated using a Gaussian basis set. A modification of the method of Coulson and Neilson is used. The distribution function f(r12) of the vector r12 is determined instead of the distribution function of the scalar interelectronic distance f(r12). Curves of f(r12) and the Coulomb hole function are plotted for selected orientations of the electron pair to the nuclear arrangements. The method allows a graphic presentation of the dependence of the size of the Coulomb hole on the nuclear geometry of the polyatomic system.
Vapor Pressures of the Deuterated Ethanes
Authors: Van Hook W. Alexander
Published: January 2005

The vapor pressures of all 10 deutero—protio-ethane isomers C2HiD6—i (0≤i≤6) have been measured over the temperature range 115° to 200°K [∼1 mm C2H6 to 1600 mm C2H6] by direct manometry. The isotope effects are inverse and go through maxima between 125° and 140°K. At the maxima they are on the order of 1.2% per D atom. Deviations from the law of the mean are small, but for the three sets of equivalent isomers 1,1- and 1,2-C2H4D2; 1,1,1- and 1,1,2-C2H3D3; and 1,1,1,2- and 1,1,2,2-C2H2D4 significant differences in vapor pressure are observed. The more unsymmetrically substituted compound has the higher vapor pressure in all cases.

The data are interpreted in the light of the statistical theory of isotope effects in condensed systems. A model calculation is made within the framework of this theory in its harmonic-cell approximation using reasonable force fields. It is necessary to invoke temperature-dependent force constants for the low-energy (u=hv/kT<2π) modes in order to rationalize the temperature dependency below 140°K. The agreement between the model calculation and experiment is excellent.

The calculations reveal that the torsional motion, which must be blue shifted on condensation, is the single most important contributor to the isotope effects between equivalent isomers.

The results constitute the second independent confirmation of the statistical theory of isotope effects in condensed systems as applied to molecules exhibiting higher-order quantum effects.
Lattice Parameters Between 5° and 298°K and Crystal Structure at 5°K of Cobalt Chloride Dihydrate
Authors: Morosin Bruno
Published: January 2005

Lattice dimensions for CoCl2·2H2O as a function of temperature have been determined in the range between 4° and 298°K. A very small anomaly has been found in the b0 lattice parameter near the Neél temperature. The crystal structure at 5°K has been refined using single-crystal diffractometer Mo Kα x-ray intensity data from hk0 and h0l zones. The unit-cell dimensions contract anisotropically from values of a0=7.279, b0=8.553, c0=3.569, β=97.58° at 298°K to values of a0=7.206, b0=8.498, c0=3.564 Å, β=97.60° at 5°K. However, the fractional atomic coordinates of the 5°K structure differ only by a maximum of four standard deviations from those previously determined at room temperature.
Interaction Between Two Rotating Dipolar Systems and a Generalization to the Rotational Double-Temperature Potential
Authors: Linder Bruno
Published: January 2005

A field-theoretic approach is used to derive general expressions for the adiabatic interaction between two rotating dipolar systems. The treatment applies to systems having the same temperature as well as to systems having different temperatures. The results, which are expressed in terms of the dipole moments, moments of inertia, and temperatures of the two systems are valid, in second-order approximation, over the whole range of temperatures including the region where quantum effects are important. The classical limit reduces to the Keesom potential for equal temperatures. When the temperatures are different the classical potential can take on positive (repulsive) values as well as negative (attractive) values, depending on the temperature difference and ratio of temperature to moment of inertia of the two systems for large temperature differences the potential is always repulsive. The general equations are analyzed and the quantum-statistical implication underlying the theory is discussed.
Vacuum-Ultraviolet Photochemistry. IV. Primary Processes in the Photolysis of Water at 1470 Å
Authors: Stief L. J.
Published: January 2005

Water has been photolyzed at 1470 Å in the absence and presence of ethylene which acts as a scavenger for hydrogen atoms. Mixtures of D2O and C2H4 were used to distinguish between hydrogen from the photolysis of water and from the photolysis of ethylene.

In the presence of 5% and 20% C2H4, the rate of D2 production from the photolysis of D2O is 6% of that in the absence of C2H4. It is concluded that in the photolysis of D2O at 1470 Å, there are two primary processes occurring: D2O+hv1470Å→D+OD,D2O+hv1470Å→D2+O.Direct production of molecular hydrogen and atomic oxygen accounts for 6% of the primary processes.
Infrared Study of Adsorbed Molecules on Metal Surfaces by Reflection Techniques
Authors: Greenler Robert G.
Published: January 2005

The problem of obtaining the infrared spectrum of a molecular monolayer adsorbed on a bulk metal is discussed. The intensity of an infrared absorption band in radiation reflected from the surface is calculated for (a) various optical constants of the adsorbed layer and the metal, (b) various thicknesses of the adsorbed layer, (c) various angles of incidence, and (d) both states of polarization of the incident radiation. The absorption factor for infrared radiation polarized parallel to the plane of incidence typically has a peak at an incident angle of about 88°, where the absorption is 5000 times greater than at normal incidence. The absorption of a thin layer by the reflection technique, at optimum conditions, is calculated to be about 25 times greater than by transmission through the unsupported film at normal incidence.
Comparison of Approximate Translational—Vibrational Energy-Transfer Formulas with Exact Classical Calculations
Authors: Kelley J. Daniel , Wolfsberg Max
Published: January 2005

The Hamiltonian equations of motion for collinear-colliding diatomic-molecule—atom and diatomic-molecule—diatomic-molecule systems are numerically integrated to obtain vibrational energy-transfer data. The diatomic molecules are taken to be either harmonic or Morse-type oscillators, and the collision potential is either an exponentially repulsive potential or a Lennard-Jones 6–12 potential.

The results of the exact classical three-body calculations are compared to results predicted by classical and semiclassical approximations. The ratios of approximate to exact energy-transfer values are related to the value of a parameter which depends only upon the masses of the particles involved in the collision; this correlation is found to be relatively insensitive to the values of the collision energy and of the potential parameters over wide ranges.

The exact classical energy-transfer data for the four-body systems are compared to the approximate and exact three-body data. The validity of using three-body approximations in treating four-body collisions is discussed.
Resonances in the Elastic and Inelastic Electron Scattering from N2
Authors: Heideman H. G. M. , Kuyatt C. E. , Chamberlain G. E.
Published: January 2005

A sharp and isolated resonance of the ``helium-window'' type has been discovered in electron transmission measurements in N2 at 11.48 eV (believed accurate to within 0.05 eV). Additional resonance structure is observed at 11.75 and 11.87 eV. The E3Σg+ state is coincident in energy with the 11.87-eV structure and is found to exhibit an excitation probability sharply peaked near threshold. The series of resonances, previously known to exist between 1.8 and 3.5 eV as a consequence of an N2− state with vibrational structure, has been studied with improved resolution and by different procedures.
Gaussian Lobe Function Expansions of Hartree—Fock Solutions for the First-Row Atoms and Ethylene
Authors: Whitten J. L.
Published: January 2005

Gaussian expansions of ground-state Hartree—Fock solutions for the first-row atoms are determined by a self-consistent-field minimization of atomic energies. Wavefunctions are constructed from a basis set designed primarily for use in molecular calculations which consists only of functions of the form exp(—ar2). Angular dependence is achieved by defining origins for the basis functions at points in space determined in part by the symmetry of the orbital to be expanded.

A use of atomic information in molecular problems is discussed in a SCF treatment of the ethylene molecule.
Polynomial Radial Functions for Atomic Wavefunctions
Authors: Gimarc B. M.
Published: January 2005

Polynomial radial functions are proposed for the construction of atomic wavefunctions and motivation is presented for their use in the theory of separated electron pairs. The properties of these functions are elucidated through energy calculations for the hydrogen and helium atoms.
Quantum-Mechanical Study of Some Three-Center Two-Electron Systems. I. Energy Calculations
Authors: Banyard K. E. , Shull Harrison
Published: January 2005

Recent work on H3+ has been carried over to an investigation of a series of pseudomolecular ions of the form ZHZ+2Z−1. This was done in the hope of obtaining some understanding of the three-center, two-electron bonds of which the ``bridge'' bond in diborane is one possible example. The two-electron systems, studied here, may be regarded as an approximate representation of a fragment of a more complex molecule. Therefore, noninteger Z values were used in an attempt to make some allowance for the nuclear shielding caused by the presence of other electrons which were otherwise unaccounted for in the present calculations. The effective nuclear charge Z was allowed to take values of 0.8 (0.2) 2.2 and the optimum bond angle ZHZ was studied as a function of Z. For each Z, a study was also made of the angular dependence of the molecular energy for a fixed value of the bond length Z—H. Within a limited basis set the present treatment is a complete configuration-interaction calculation.

The study gave rise to several interesting features, two of which are the sizeable initial decrease in the bond angle as Z is increased and the occurrence of a double minimum in the molecular energy as a function of the bond angle for Z∼1.8. Therefore, for Z=1.8, the dependence of the molecular energy upon the bond angle ZHZ was also investigated for different values of the bond length. Although Part II contains a natural spin—orbital analysis of the wavefunction for each system, it was felt obligatory, at this stage, to offer a tentative interpretation of the present results. This was performed in terms of the movement of charge density components as a function of the bond angle and Z.
Crystal Structure and Optical Properties of (CH3)2NH2CuCl3
Authors: Willett Roger D.
Published: January 2005

The crystal structure of (CH3)2NH2CuCl3 has been determined by x-ray diffraction techniques. The compound contains approximately planar Cu2Cl6= dimers which contain two bridging chlorine atoms. All Cu–Cl bond distances in the dimer are approximately 2.3 Å and all bond angles approximately 90°. The crystals are pleochroic with maximum visible absorption when the electric vector is parallel to the [301] direction.
Infrared Spectra of Crystalline and Matrix-Isolated Carbonyl Sulfide
Authors: Verderame Frank D. , Nixon Eugene R.
Published: January 2005

The infrared spectrum of carbonyl sulfide has been examined as a polycrystalline film at 80°K and also in matrix-isolated form, using argon, nitrogen, and CS2 as the matrix materials. Particular attention has been given to the ν3 vibration, which appears as an abnormally broad and asymmetric band in solid OCS. The asymmetry of ν3 does not appear to be the result of any significant reflection effects nor is it due to disorder in the crystal. A study of the concentration dependence of the ν3 frequency in isotopic mixtures shows that a good part of the asymmetry can be attributed to the ν3 absorption of molecules containing 33S and 34S. Spectra of dilute mixtures of OCS in argon matrices display absorption by both isolated molecules and molecular pairs. The features of the spectrum are qualitatively accounted for in terms of a simple model of pairs interacting through transition-dipole coupling. In both N2 and CS2 matrices, the evidence suggests two different sites for the OCS molecule in the host lattice.
Extended Hartree—Fock Wavefunctions: Optimized Valence Configurations for H2 and Li2, Optimized Double Configurations for F2
Authors: Das G. , Wahl Arnold C.
Published: January 2005

As a step beyond the Hartree—Fock technique in the search for better energies, wavefunctions, and the general description of molecular formation and dissociation, a configuration-mixing method of the following nature is developed and illustrated for H2, Li2, and F2. The wavefunction Ψ= ∑ kAkΦkconsists of several optimized configurations obtained by replacing one of the σ-orbitals of the primary configuration (in our case the Hartree—Fock) by orbitals of different kinds. All the orbitals involved are orthonormalized, insuring orthonormalization of the configurations themselves. The present method determines energetically the optimum combination of both the mixing coefficients Ak and the linear orbital parameters by the solution of SCF-type equations and insures dissociation of the molecule to two Hartree—Fock atoms. A program based upon this formalism has been constructed by the authors for the IBM 7094 computer and is capable of handling homonuclear diatomic molecules using as many as ten configurations with up to 33 two-center symmetry basis functions. Results obtained are energetically better than conventional multiconfiguration studies and since our method is designed to account for added correlation energy associated with molecular formation, calculated potential curves much more realistic than the Hartree—Fock ones can be realized. Sample calculations which represent a partial-optimization procedure within the framework of the analysis are given for the molecules H2, Li2, and F2. We feel, however, that these results are quite close to the true solution. The binding energies obtained with these optimized configuration functions are 4.63, 0.93, and 0.54 eV for H2, Li2, and F2, respectively, as contrasted with the Hartree—Fock dissociation energies of 3.64, 0.17, and −1.37 eV.
Vibrational Analysis of Acetone, Acetaldehyde, and Formaldehyde
Authors: Cossee P. , Schachtschneider J. H.
Published: January 2005

Normal-coordinate calculations have been carried out for the molecules acetone, acetone-d6, acetaldehyde, acetaldehyde-d4, acetaldehyde-d1, formaldehyde, and formaldehyde-d2. Infrared and Raman spectra for acetone, acetone-d6, and acetaldehyde-d4 were measured and assigned. Together with experimental data and assignments taken from the literature for the other molecules, these yield an almost complete set of fundamental frequencies.

These frequencies were used to derive approximate force fields for these molecules and to investigate the transferability of the force constants. Calculations were carried out with both the Urey—Bradley force field (UBFF) and the valence-force field (VFF) with selected interaction constants. The Urey—Bradley force field is not satisfactory unless it is augmented with some valence-force interaction constants. In the valence-force approximation it is not possible to make an unambiguous choice of the nondiagonal constants. However, a most probable force field is indicated, which on the one hand reproduces the experimental frequencies and on the other hand shows reasonable values for diagonal and nondiagonal force constant.

The CO stretching constant, KCO, and the force constants around the CO group appear to be nontransferable among these molecules. The most probable force field indicates a decrease in the value of KCO in going from formaldehyde to acetaldehyde, to acetone. It is noted that the choice of interaction constants has a great influence on the values of the diagonal force constants and on the normal coordinates. Anharmonicity effects are also found to influence the values of the force constants and may affect the resulting conclusions.
Main-Chain Scission and ESR Spectra of Irradiated Polytetrafluoroethylene Oxide
Authors: Barnaba P. , Cordischi D. , Site A. Delle , Mele A.
Published: January 2005

The chief effect of ionizing radiation on polytetrafluoroethylene oxide (PTFEO) is to induce main-chain scission. The ESR spectrum of the irradiated polymer in vacuum consists of two components. The stable spectrum is attributed to the –CF2–CF2–O. and –O–ĊF–CF2–O– radicals. The former radical decays slowly at room temperature, the latter is unchanged even after several weeks. The unstable spectrum disappears in a few hours and its structure is uncertain. Tentatively this spectrum is assigned to the –O–CF2–CF2. radical. Admission of air to the irradiated polymer gives rise to a spectrum formed of a symmetric singlet assigned to –CF2CF2–OO. radical and an asymmetric signal to –CF–CF2–O–.  – O–O·A Gfracture=1.8 has been calculated from viscosity data.
Order—Disorder Phenomena. IV. Ultrasonic Attenuation near the Lambda Point in Ammonium Chloride
Authors: Garland C. W. , Yarnell C. F.
Published: January 2005

The attenuation coefficient α of longitudinal acoustic waves propagating along the [100] direction in ammonium chloride has been reinvestigated as a function of frequency from 10 to 60 Mc/sec and of temperature from 215° to 300°K. Special emphasis was given to 10-Mc/sec data at temperatures very close to the order—disorder transition, and hysteresis was observed. These attenuation data are consistent with the behavior expected from a compressible Ising model which predicts a mechanical instability in the immediate vicinity of the transition temperature.
Effects of Electron Correlation in X-Ray and Electron Diffraction. III. Experimental Electron—Electron Distribution Functions
Authors: Gavin R. M. , Bartell L. S.
Published: January 2005

Radial distribution functions of electrons with respect to the other electrons in neon and argon atoms are derived from Laurila's experimental x-ray intensities. The resulting distribution functions are used to calculate experimental electron—electron potential-energy values. In qualitative features the distributions compare favorably with those calculated from existing wavefunctions. Uncertainties in the distribution functions due to the scatter of experimental data points and to the restricted angular range of the data were large enough to obscure effects of electron correlation.
Surface Debye Temperatures of the (100), (111), and (110) Faces of Platinum
Authors: Lyon H. B. , Somorjai G. A.
Published: January 2005

The intensity of back-diffracted low-energy electrons (15–350 eV) from the clean (100), (111), and (110) surfaces of platinum single crystals was measured. From the temperature dependence of the (00) reflection in the range of 25°—700°C, the Debye—Waller factor and the root-mean-square displacements of surface atoms perpendicular to the surface planes were determined. The measured root-mean-square displacement 〈uz2〉½ was found to be a sensitive function of electron energy. The properties of the surface planes were determined from the intensity data taken at the lowest electron energy. Using the Debye model in the high-temperature approximation, the Debye temperatures and the frequencies of lattice vibration were calculated. The root-mean-square displacement of surface platinum atoms perpendicular to the surface plane is about twice as great as that in the bulk. This effect gives rise to surface Debye temperatures which are much smaller (107°—118°K) than the bulk value (234°K).
Excited-State Formation and Destruction in Mixtures of Atomic Oxygen and Nitrogen
Authors: Young Robert A. , Black Graham
Published: January 2005

Absolute measurements were made of the intensity of emission from atomic oxygen (5577 Å), molecular oxygen (the Herzberg bands below 4000 Å, the atmospheric band at 7618 Å), nitric oxide (the β bands below 4000 Å), and molecular nitrogen (the first positive bands from 5000 Å to 6000 Å) when excited in a low-pressure gas atmosphere containing atomic nitrogen and/or oxygen in absolutely measured quantities. The relationship between light emission and atomic concentration, pressure, gas mixture, and quenching gas concentration was obtained. With these data as bases, excitation and de-excitation processes are discussed and rate coefficients of several elementary processes deduced. These have been applied to nightglow phenomena of the earth's upper atmosphere.
Effect of Radiation Damping on Dispersion
Authors: Lin Sheng Hsien , Bersohn Richard
Published: January 2005

Optical observables such as the polarizability, optical rotation, the Kerr and Faraday effects, and the Cotton—Mouton effect will become infinite whenever the incident frequency coincides with any of the natural frequencies of the system. Consideration of the finite lifetime of the initial states removes the singularities. For a completely isolated molecule, radiation damping would suffice to limit the lifetime; for laboratory systems the vibrational and rotational relaxation accomplish the same purpose and radiation damping is negligible for practical applications. The main point of the calculation has been to show explicitly what was previously (by Condon and by Moscowitz) surmised.
Individual Efficiency Curves for the Excitation of 23S and 21S States of Helium by Electron Impact
Authors: Čermák V.
Published: January 2005

Measurement of kinetic energy of electrons released in ionization of argon by helium atoms in metastable 21S and 23S states was applied for the determination of separated efficiency curves for the two states. No quenching in electric field or deflection in an inhomogeneous magnetic field was necessary. The ratio of the cross sections for the 21S and 23S states, excited by electron impact, was found larger than that determined in experiments in which secondary electron emission was used for detecting metastable atoms. This seems to indicate that the Penning ionization cross section for argon by helium atoms in the 21S state is larger than that by the atoms in the 23S state.
Retarding-Potential Measurement of the Kinetic Energy of Electrons Released in Penning Ionization
Authors: Čermák V.
Published: January 2005

Kinetic energy of electrons released in ionization of N2, CO, NO, COS, CO2, C2H2, CH4, C2H6, C3H8, and n-C4H10 by means of helium atoms in metastable 21S and 23S states was measured and the energy of electronically excited ionic states determined. In N2, CO, COS, and CO2 all accessible excited states were populated probably by a Franck—Condon transition. Ionization of NO seems to proceed through pre-ionization of the HeNO complex in which a part of internal energy is converted into kinetic energy of He and NO+. In ionization of C2H2 and CH4, energy which can be effectively stored in the C2H2+ and CH4+ ions in the ground state was determined and the aspects of the dissociative ionization discussed. In ionization of C2H6, C3H8, and n-C4H10, more excitation energy is conferred on the ions than in ionization by charge transfer or electron impact.
Momentum Eigenfunction for the Ground State of H2+
Authors: Glaser Frederic M. , Lassettre Edwin N.
Published: January 2005

The nodes of the momentum eigenfunction for the ground state of the hydrogen molecule ion have been studied by calculating the momentum eigenfunction as a function of the momentum component Pz (z axis parallel to line of centers) with Px=Py=0. The existence of zeros in the ground-state eigenfunction is confirmed.
Mobilities of Electrons and Holes in Organic Molecular Solids. Comparison of Band and Hopping Models
Authors: Glaeser R. M. , Berry R. Stephen
Published: January 2005

A comparison is made of the applicability of two limiting models for describing the mobility of excess charges in molecular organic solids. Anthracene is the principal solid examined, but similar calculations are also given for naphthalene. A critical re-evaluation is made of the transfer integrals (which have been calculated from molecular orbital wavefunctions), and an approximate method is given by which one may include the effects of electronic polarization. These transfer integrals are then used to discuss mobilities (1) in terms of simple band theory, in which a delocalized, tight-binding representation is used and (2) in terms of a simple hopping theory, in which a one-site representation is used. The two models are tested for consistency with experiment and for internal, theoretical consistency. It is concluded that as a first approximation, the hopping model is superior to the band model, and gives a quantitatively accurate picture of the physical mechanism underlying charge mobility in molecular organic solids.
Delayed Luminescence of Organic Mixed Crystals
Authors: Misra T. N. , McGlynn S. P.
Published: January 2005

The luminescence spectra of the following mixed-crystal systems have been investigated: naphthalene-h8 guest—biphenyl host; naphthalene-d8 guest—biphenyl host; phenanthrene guest—biphenyl host; chrysene guest—biphenyl host; naphthalene-h8 guest—durene host; naphthalene-d8 guest—durene host; phenanthrene guest—durene host; chrysene guest—phenanthrene host; dibenzanthracene guest—phenanthrene host; phenanthrene-d10 guest—biphenyl host. The quantities on which experimental information is provided are: temperature and excitation intensity dependence of phosphorescence and delayed fluorescence intensities; concentration dependence of phosphorescence and delayed fluorescence intensities; and decay data at different temperatures for delayed fluorescence. Delayed fluorescence of the guest is observed from all mixed-crystal systems for which S1H > S1G > T1H > T1G, where, for example, S1H denotes the first excited singlet state of the host as well as the energy of this state. If the gap T1H↔T1G is sufficiently large, the delayed fluorescence may be very weak, or absent. Two types of triplet—triplet annihilation processes have been substantiated: guest—guest annihilation which is of significance at temperatures above 100°K, and guest—trap annihilation which is dominant in the region 100°↔77°K. A third type of triplet—triplet annihilation, namely trap—trap annihilation, is probably causative of the delayed fluorescence of so-called ``pure'' or ``one-component'' crystals. The nature of the traps is not understood; they may be surface host species, defect host species or adventitious trace impurities.
Infrared Spectra of Some MH4 Molecules
Authors: Wilkinson George R. , Wilson M. Kent
Published: January 2005

Molecular constants have been obtained for a number of the fourth-group hydrides. The values of the M—H distances which have been obtained under the assumption of tetrahedral angles are: SiD3H, 1.480±0.001 Å; GeH3D, 1.525±0.001 Å; GeD3H, 1.532±0.001 Å; SnD3H, 1.701±0.001 Å.
Integral Equations for Distribution Functions of Classical Fluids. II
Authors: Allnatt A. R.
Published: January 2005

An exact integral equation is derived for FN+2/FN, where FN denotes the correlation function for a set N of molecules in a multicomponent fluid. The equation bears superficial resemblance in form and derivation by cluster theory to the Ornstein—Zernike equation derived by several workers recently. However, the equation is not closed since functions FN+1/FN appear, as well as a ``prototype sum'' which is similar to that in the equation for F2 but involves additional functions fn=exp(—wn/kT)−1, where wn is the n particle component of the potential of average force. The use of the equation to improve calculations of F2 is discussed for the one-component case and an approximate integral equation for f3, which would be zero were the Kirkwood superposition approximation exact, is explicitly stated.
Theory for the Plasticity of Glassy Polymers
Authors: Robertson Richard E.
Published: January 2005

We present a theory for how a shear stress alone can induce structural changes in a glassy polymer to break up the rigidity of the glass and allow flow. We consider a molecular model in which the shear-stress field is introduced as a bias on the rotational conformation of backbone bonds. It is argued that the fraction of flexed bonds is transiently increased from that in the glass and that this, additionally causing a volume increase, produces a polymer structure resembling the liquid at some temperature above the glass transition. Using these considerations along with several well-known empirical relations, we have calculated the plastic properties of polystyrene and polymethyl methacrylate. These calculated properties correspond reasonable well with the cold-drawing data available.
Crystal-Field Studies of Excited States of Trivalent Neodymium in Yttrium Gallium Garnet and Yttrium Aluminum Garnet
Authors: Koningstein J. A.
Published: January 2005

An analysis has been made of the position of Stark components of excited states of the trivalent neodymium ion in the aluminum garnet and gallium garnet host lattices. The crystal-field calculations reveal that not all crystal-field parameters for these states are equal. It has been found that for some states this change cannot be attributed to intermediate coupling effects or J mixing.
Vibrational Spectra of Vanadium Pentafluoride
Authors: Claassen Howard H. , Selig Henry
Published: January 2005

The infrared spectrum of VF5 vapor has been studied from 140 to 4000 cm−1. The Raman spectrum has been obtained for the vapor and for the liquid at various temperatures. The spectra indicate a D3h symmetry for the molecule. Fundamental vibrational frequencies observed are: a1′, 719 and 608; a2″, 784 and 331; e′, 810, 282, and (∼200); e″, 350; all in cm−1. Approximate bond-stretching force constants for a modified Urey—Bradley potential function are: Kr=5.51 Mdyn/Å, Kd(axial)=3.94 Mdyn/Å. The Raman spectra show that monomeric molecules are in low concentration in the room-temperature liquid but constitute the main component in the liquid at temperatures above 100°C.
Energy Levels and Crystal-Field Splittings of Nd3+ in Yttrium Oxide
Authors: Chang N. C.
Published: January 2005

Studies of the absorption and fluorescence spectra of Nd3+ in yttrium oxide are reported in this paper. The three Racah parameters E1,2,3 and the spin—orbit parameter ζ giving the best over-all agreement between the observed and calculated spectrum are E1=4853.9, E2=24.20, E3=471.87, and ζ=877.59 cm−1. The Stark splittings of the four levels 4I9/2, 4I11/2, 4I13/2, and 4I15/2 are used in a first-order perturbation calculation to determine the crystal-field parameters for Nd3+ in the C2 sites of the Y2O3 lattice. The parameters are used to calculate the Stark splitting of 13 excited levels, and the results are compared with experimentally observed values. For 64 Stark components, the calculation predicts the splitting with an average of about 15 cm−1. For the components of the 2H11/2 and 2G7/2 levels, very large discrepancies are present.
Infrared Absorption of Ce3+ in LaF3 and of CeF3
Authors: Buchanan R. A. , Rast H. E. , Caspers H. H.
Published: January 2005

The infrared absorption spectra of Ce3+ in LaF3 and of CeF3 have been observed in the region of 3 to 6 μ. The four absorption lines for Ce3+ in LaF3 at 2160, 2240, 2635, and 2845 cm−1 that persist at liquid-helium temperature are identified as transitions originating on the ground Stark component of the 2F5/2 and terminating on the four Kramers-degenerate Stark levels of the 2F7/2. Observation of the temperature dependence of the spectrum has revealed two additional transitions beginning on a 2F5/2 Stark level 150 cm−1 above the ground state and ending on the two lowest levels of the 2F7/2. The results are essentially the same for CeF3 and are in substantial agreement with the results of temperature-dependent studies of the magnetic susceptibility and Faraday rotation of CeF3 and tysonite.
Intensity Variation with Scattering Angle of Electronic Transitions in H2O Excited by Electron Impact
Authors: Skerbele Ausma , Lassettre Edwin N.
Published: January 2005

Electron-impact spectra of water vapor have been investigated at 400- and 500-V electron kinetic energy. The relative intensities of the five peaks associated with the A and B Rydberg transitions have been studied as a function of the scattering angle. The results suggest a new method of identification of vibrational levels where a high-resolution study of rotational structure is not feasible.
Vibrational Intensities of the A1Π←X1Σ+ Transition in Carbon Monoxide
Authors: Skerbele Ausma , Meyer Vincent D. , Lassettre Edwin N.
Published: January 2005

The electron-impact spectrum of carbon monoxide has been investigated at electron energies of 400 and 200 V. The intensity distribution among vibrational levels of the A1Π←X1Σ+ transition has been studied as a function of the scattering angle and electron kinetic energy. The experimental data have been compared with theoretical predictions based on the Born approximation. The results indicate that in the range of the present measurements (θ<6°) the relative intensities are independent of the scattering angle. This observation agrees with the approximate theory of Craggs and Massey. The relative intensities agree fairly well with the Franck—Condon factors calculated by Nicholls except at high vibrational quantum numbers.
Numerical Evaluation of Barrier Penetration and Resonance Effects on Phase Shifts
Authors: Bernstein R. B. , Curtiss C. F. , Imam-Rahajoe S. , Wood H. T.
Published: January 2005

Quantum-mechanical calculations for a Lennard-Jones (12, 6) potential are presented showing the dependence of the reduced phase shift η* on the quantum parameter Λ* for a fixed reduced effective potential and various reduced energies E*. The observed oscillatory behavior of η* (Λ*) is due primarily to the inclusion of the physically unimportant contribution of Mπ to the phase shift, where M is the number of quasibound (virtual) states of energy less than E*. A modified reduced phase shift η*, defined by excluding this contribution, displays only the sharp inflections associated with barrier penetration under resonance conditions. Except for the resonance contribution, the phase shifts may be accurately reproduced by a second-order JWKB procedure. This method also accurately predicts the resonance energies (i.e., the energies of the quasibound states). In the region of a resonance, the scattering cross section varies rapidly with energy in a typical resonance manner. If they do not seriously overlap, the resonance ``lines'' should be observable as perturbations on an otherwise smooth background in low-energy beam-scattering experiments. The first-order JWKB treatment of the barrier penetration problem by Ford, Hill, Wakano, and Wheeler suffices for the purpose of estimating the level widths and lifetimes of the virtual states as well as the main features of the resonant phase shifts, but does not accurately reproduce the quantal calculations.
Spectroscopic Basis of Carbonyl Photochemistry. I. The Role of Excited-State Geometry in the Photodecomposition of Formaldehyde
Authors: Abrahamson E. W. , Littler J. G. F. , Vo Kim-Phan
Published: January 2005

The photochemistry of formaldehyde is correlated with its spectroscopy within a molecular orbital framework. According to the picture, photodecomposition arises from one electron population of a pair of C<H2 antibonding orbitals, one of which is H–H bonding and yields H2+CO and the other H–H antibonding yielding H+HCO or 2H+CO. These orbitals are populated in singlet states by radiationless transitions from the nonplanar 1(n, π*) state.
Niobium—Al2O3 Reactions Yielding Condensed and Volatile Products
Authors: Grossman L. N.
Published: January 2005

A mass-spectrometric and thermogravimetric study of the equilibrium interaction between Al2O3 and Nb between 1800° and 2200°K has been conducted. The reaction proceeds principally as Al2O3+3Nb=2Al(g)+3NbO(s); two secondary reactions of about equal importance under neutral conditions are Al2O3+Nb=Al2O(g)+NbO2(g) and Al2O3+2Nb+12O2=Al2O(g)+NbO2(g)+NbO(s). The latter reaction can dominate under oxidizing conditions. The weight loss caused by the gaseous reaction products is about one hundred times the weight loss caused by the evaporation of alumina under neutral conditions. Calculations show that yttria and some other oxides can be used with Nb at high temperatures with no significant reaction.
Homogeneous Nucleation Measurements of Water Vapor in Helium
Authors: Kassner James L. , Schmitt Raymond J.
Published: January 2005

A determination of the homogeneous nucleation rate of water vapor in helium is made. A procedure is established for determining an ``effective'' adiabatic index which may be used to find the final temperature obtained in an isentropic expansion of a real gas. A numerical integration technique is employed in analyzing experimental data. Results for supersaturations near 5 agree closely with the Becker and Doring theory.
Electron Spin Resonance Spectra of the Radical Anions of Several 1,3-Dienes
Authors: Levy Donald H. , Myers Rollie J.
Published: January 2005

The ESR spectra of the radical anions of 2,3-dimethyl−1,3-butadiene, 1,3-cyclohexadiene, and isoprene have been examined in liquid ammonia. The proton hyperfine interaction can be readily assigned except for the case of isoprene where there is a small discrepancy between our assignment and the observed spectrum. In the case of 2,3-dimethyl−1,3-butadiene two distinct CH2 coupling constants are observed as might be possible for the radical anion in either a s-cis, s-trans, or skew conformation. Hückel theory with the inclusion of hyperconjugation is in good agreement with the observed proton coupling constants.
Torsional Coordinates in Vibrational Anharmonicity; Application to Ethylene
Authors: Machida Katsunosuke
Published: January 2005

Formulas for the first through third derivatives of torsional coordinates with respect to difference Cartesian coordinates are given. These formulas may also be used for out-of-plane bending coordinates. A sample calculation of an anharmonic potential function involving these coordinates has been made for ethylene and ethylene-d4. The procedure of anharmonicity calculation for polyatomic molecules is formulated by the use of matrix direct product notation and is discussed.
Vibrational Spectrum of Hydrazine-d4 and a Raman Study of Hydrogen Bonding in Hydrazine
Authors: Durig J. R. , Bush S. F. , Mercer E. E.
Published: January 2005

The infrared spectra of liquid, solid, and gaseous tetradeuterated hydrazine have been measured from 250 to 4000 cm−1. Fine structure was resolved for three of the perpendicular fundamental bands of the assumed symmetric top. The Raman spectra of liquid hydrazine and tetradeuterated hydrazine have been recorded and depolarization values measured. A complete vibrational analysis based on band type, position, and depolarization values is given which satisfies the product rule for both the a and b vibrational symmetry species. The intensity of the 3189-cm−1 band of hydrazine has been studied as a function of temperature. ΔH° for H-bond formation in hydrazine is found to be − 1450 cal/mole. The relative intensity of the 3189-cm−1 band to that of the 3260-cm−1 band has been studied as a function of concentration in dimethylsulfoxide and indicates that part of the intensity of the 3189-cm−1 band arises from a vibrational mode of the hydrazine monomer.
Oscillator Strengths of the Negative Systems of Oxygen
Authors: Jeunehomme M.
Published: January 2005

The first and second negative systems of the oxygen molecular ion were excited in a modulated or sharply interrupted pulsed rf discharge. Lifetimes for both excited levels were deduced from the observed fluorescence decay times. Relative values were calculated from the phases of the emission in a number of vibronic bands of the second negative system. Oscillator-strength values are presented for both systems, and the variation of the transition moments with internuclear separation was investigated.
Conformation of an Isolated Polymer Molecule at an Interface. III. Distributions of Segment Densities near the Interface and of Other Shape Parameters
Authors: Roe Ryong-Joon
Published: January 2005

A detailed study of the conformation of an isolated polymer molecule adsorbed at a solution interface is given. It is an extension of the similar work, previously published, in which average values of the fraction θ of adsorbed segments, the number 〈r〉 of adsorbed sequences per polymer chain, and the number of segments 〈a〉 in an adsorbed sequence, 〈d〉 in a loop, and 〈d0〉 in a terminal desorbed sequence were derived. In this work probability distributions of these shape parameters are given. In addition, we consider here the segment density distributions in the solution near the interface. The number q(z) of desorbed segments, belonging to loops, which are expected to be at distance z from the interface is derived separately from the number q0(z) of desorbed segments belonging to terminal dangling sequences. For evaluation of these quantities, extensive use is made of the generating function method by extending the summation procedure proposed by Lifson. The contour integral appearing in Cauchy's theorem is evaluated by the steepest descent method which was shown in the previous work to give numerical values to a good approximation. The results show, among others, that the density distribution q(z) of loop segments is exponential, while the distribution q0(z) of the segments belonging to terminal sequences is given by a difference of two exponential functions and has a maximum at an intermediate z. As the value of the segmental adsorption constant s varies past the critical value sc, the relative numbers of desorbed segments belonging to loops and to terminal sequences vary drastically, and consequently either q(z) or q0(z) predominates except when s is very near sc. It is shown that the treatment can be readily extended to cases where either one or both of the polymer-chain ends is much more strongly adsorbed than the rest, and also where the interface consists of a mixture of sites having different affinities for adsorption of polymer segments.