bluuebunny/crossref_metadata_2025 huggingface dataset:
Modifications of the Absorption Spectra of Anions Induced by Complex Formation
Authors: Katzin Leonard I.
Published: January 2005

The absorption of thiocyanate, chloride, bromide, and iodide ions are markedly altered on complexing with nickelous or cobaltous ions in isopropyl alcohol solution, new peaks appearing at longer wavelengths. In the case of iodide ion, the absorption spectra of the complexes with nickelous ion, cobaltous ion, and iodine (the ``tri-iodide'' complex) are practically distinguishable only by their extinction coefficients. A characteristic feature of the modified iodide spectrum is the pair of peaks, found at shorter wavelengths in the spectra of the free iodide ion, and in other forms. The cobaltous complexes with bromide and chloride ions show analogous splittings, but the absorption of the trihalide ions show single peaks which agree in wavelength with the longer-wavelength peak of the cobalt-complexed ion. The nickelous complexes absorb at shorter wavelengths.
Inter- and Intramolecular Energy Transfer Processes. I. Nitro-Compounds and Hydrocarbons
Authors: Reid C.
Published: January 2005

The addition compounds of aromatic nitro-compounds and hydrocarbons fluoresce appreciably only if the hydrocarbon component itself has a possible transition lying in the region where the nitro-complex might be expected from its absorption to emit. The resulting emission spectrum is very similar to that of the hydrocarbon component but much more strongly allowed. This is attributed to the breaking down of the S←T selection rule as the complex dissociates.
The X-Ray K Absorption Edges of Covalently Bonded Cr, Mn, Fe, and Ni
Authors: Mitchell G. , Beeman W. W.
Published: January 2005

We discuss some recently measured absorption edges of covalent nickel complexes and edges of Cr, Mn, and Fe in similar complexes already in the literature. Low energy absorption (generally resolved as a line) is observed in all complexes where empty 4p orbital is expected from chemical or magnetic data. From the position of the line it is concluded that the metal ion is near neutral in the covalent complex. Where the 4p orbital is completely used in bonding, no low energy absorption line is observed. The method may be useful as an additional experimental check on the assignment of bonding orbitals.
On the Calculation of Diffusion Coefficients from Sorption Data
Authors: Hwang Jenn Lin
Published: January 2005

The general equation of diffusion in which the diffusion coefficient D(c) is given by D0(1+αc+βc2+···), where α, β··· are small, can be solved by the method of successive approximation: The solution has the form c(ξ)=c0(1−Φ(ξ))+c02αψ(ξ)+c03[α2χ1(ξ)+βχ2(ξ)]+···,where Φ(ξ) is the error function and ψ(ξ), χ1(ξ)··· may be computed by numerical integrations. On the other hand, one knows from the sorption experiments the quantities defined by Kc0=2D0½∫0∞ c(ξ)dξ as a function of c0. Thus, by the above solution one may obtain a set of linear equations, from which the constants D0, α, β··· can be found with a reasonable amount of labor.

For practical purposes it would be necessary to tabulate the functions ψ(ξ), χ1(ξ), ···, because they are needed for all the problems of this kind.
The Vibrational Spectra of Molecules and Complex Ions in Crystals. VI. Carbon Dioxide
Authors: Osberg W. E. , Hornig D. F.
Published: January 2005

A previously reported discrepancy between the predicted and observed infrared spectrum of crystalline carbon dioxide is shown to arise from the presence of two peaks due to C13O2, a combination band involving a lattice frequency near 110 cm−1 and two reflection peaks. The infrared spectrum was studied at − 190°C and aside from the previous features shows one component from ν3 and two from ν2, shifted very little from the gas frequencies. The difficulties encountered in interpreting the spectrum of this simple crystal occur quite generally in the spectra of more complicated substances.
A Vibrational Analysis of the Fluorescence of Naphthalene Vapor
Authors: Schnepp O. , McClure D. S.
Published: January 2005

The fluorescence spectrum of naphthalene vapor has been photographed and found, under suitable conditions, to consist of a number of discrete bands. Thirty-nine bands were measured and a vibrational analysis was carried out making use of assignments of infrared and Raman fundamentals. The analysis indicates that the transition observed is forbidden by symmetry and made weakly allowed by a molecular vibration of frequency 478 cm−1 belonging to the representation b2u. This indicates that the wave function of the lowest excited singlet state of naphthalene belongs to the irreducible representation Ag or B1g of the point group D2h.
High Frequency Dispersion in n-Propanol
Authors: Cole R. H. , Davidson D. W.
Published: January 2005

Two dispersion regions in the liquid in addition to the primary dispersion have been measured at audio-and radiofrequencies below −120°C, which make small but significant contributions to the dielectric constant. Both move rapidly to lower frequencies with decreasing temperature and the relaxation times of the intermediate dispersion are 200 times smaller than for the primary one. The temperature and frequency dependences are those to be expected for orientation rather than induced polarization.
Hydrogen Bonding and the Interactions of Water Molecules
Authors: Campbell Edwin S.
Published: January 2005

A study of proposed explanations for the forces governing the interaction of hydrogen-bonded molecules has been made by investigating various models for the intermolecular potential function for H2O. Implications of the models concerning the known properties of H2O have been examined.

1. After a survey of existing views and data on hydrogen bonding, the electrostatic model is chosen for further study. The criterion selected to winnow the proposed models is their ability to correlate second virial data and the energy of sublimation of ice.

2. The dipolar energy of ice is calculated after Ewald and Kornfeld. Although the dipole approximation fails to pass test No. 1, it is sufficient for interesting observations on some crystal properties of ice.

3. The consistency of the dipole model with Pauling's explanation of the entropy discrepancy is examined.

4. Point charge models are discussed and a multipole calculation made for the ice structure with the highest dipole-dipole energy.

5. Calculations made suggest that a properly chosen point charge model may suffice for the correlation of gas and crystal data.
The Potential Energy Curve of Mercury Hydride
Authors: Glockler George , Horst Helene Ven
Published: January 2005

A potential energy curve for the mercury hydride molecule is constructed which takes into account the fact that the molecule can change from a structure bonded by exchange forces below about 2.65A, to a quasi-molecule held together by London dispersion forces at larger distances. The breaking off of certain bands can be understood on the basis of maxima in vibrational-rotational energy curves.
Rotational Temperatures of OH in Several Flames
Authors: Broida H. P. , Lalos G. T.
Published: January 2005

The intensity of OH emission from various small regions of Bunsen-type flames of hydrogen, acetylene, methane, and propane, premixed with oxygen, has been observed spectroscopically and corresponding rotational temperatures have been determined by an iso-intensity method. An ultraviolet grating monochromator of high resolution was used; fuel to oxygen ratios were varied from about 0.5 to 2 times the stoichiometric value; and rotational temperatures were determined at several positions within each flame. The measured temperatures of the reaction zone varied little with mixture ratio for a given fuel and were greater than adiabatic, suggesting a lack of thermal equilibrium. In the hot gases beyond the reaction zone, however, evidence was found of both rotational and electronic equilibrium. The concentration of thermally produced OH in the burned gases was found to be so great that it tends to mask the emission from the reaction zone.
Photoconductivity of Violanthrone
Authors: Akamatu Hideo , Inokuchi Hiroo
Published: January 2005

Photoconductivity of violanthrone, iso-violanthrone, and pyranthrone, the organic semiconductors, has been investigated. From the threshold of spectral response of photoelectric current, the energy gap between the full ground band and the empty excited band was estimated as 0.84 ev, 0.93 ev, and 1.14 ev, respectively. These results are in good agreement with that estimated from the temperature dependence of resistivity, and furthermore with the optical absorption of crystals.
Electronic Barrier Layer Phenomena in Chemisorption and Catalysis
Authors: Weisz P. B.
Published: January 2005

Chemisorption processes lead to interactions between electrons in the chemisorbed molecules and the electronic structure of the solid. Resulting electronic boundary layer phenomena are closely analogous to those studied in rectifier theory. Analysis by the methods of rectifier theory explains the variation of heat of adsorption with the amount adsorbed, gives the temperature dependence of chemisorption, and yields the increase of activation energy with frequency factor commonly observed in catalysis.
Approximate Self-Consistent Molecular Orbital Theory. II. Calculations with Complete Neglect of Differential Overlap
Authors: Pople J. A. , Segal G. A.
Published: January 2005

The approximate self-consistent molecular orbital method with complete neglect of differential overlap (CNDO), described in Paper I, is used to calculate molecular orbitals for the valence electrons of diatomic and small polyatomic molecules. A small number of bonding parameters (β-resonance integrals) are chosen semiempirically so that the results are comparable to previous accurate LCAO—SCF wavefunctions for diatomic hydrides using a similar basis set. With this calibration, it is found that calculations on other diatomics and polyatomics lead to molecular orbitals and electron distributions in reasonable agreement with the full calculations where available. Although the new method is not yet successful in predicting bond lengths and dissociation energies, it does lead to the correct geometry, reasonable bond angles and bending force constants for the polyatomic molecules considered. It also gives calculated barriers to internal rotation for ethane, methylamine, and methanol which are in fair agreement with experiment.
Semirigorous LCAO—MO—SCF Methods for Three-Dimensional Molecular Calculations Including Electron Repulsion
Authors: Kaufman Joyce J.
Published: January 2005

A semirigorous LCAO—MO—SCF method including electron repulsion, for three-dimensional closed-shell molecular calculations has been derived. The method starts with the complete many-electron Hamiltonian (in which interelectronic interactions are included explicitly) and the self-consistent molecular orbital equations of Roothaan, then makes a series of systematic approximations for the integrals involved. There are several different levels of approximation which evolve depending on how restrictive one makes the conditions for neglecting a′(1)a″(1), where a′ and a″ are two orbitals on Atom A; and a′(1)b″(1), where a is an orbital on Atom A and b is an orbital on Atom B, A ≠ B, and for neglecting (a′c′′′| G | b″d′v), where a′ is an orbital on Atom A, b″ is an orbital on Atom B, c′′′ is an orbital on Atom C, d′v is an orbital on Atom D, and A, B, C, D are, in general, different atoms. The approximations for the core operators are defined and the core Hamiltonian matrix elements are presented in detail for several of the levels of approximation. The complete expressions for Fa′a′, Fa′a″, and Fa′b″ for closed-shell systems in the two simplest of the approximative schemes are included in the body of this paper. The salient details of the more complicated schemes (corresponding to lesser and lesser neglect of the interaction of charge distributions) are indicated.

These semirigorous LCAO—MO—SCF schemes outlined in this paper hold promise for less-than-rigorous yet better-than-empirical calculations for the whole gamut of three-dimensional molecules from simple inorganics through complicated organics. An analogous treatment with the same approximations for the neglect of certain integrals can also be applied to an open-shell LCAO—MO—SCF procedure.
Studies in Perturbation Theory. XI. Lower Bounds to Energy Eigenvalues, Ground State, and Excited States
Authors: Löwdin Per-Olov
Published: January 2005

The bracketing theorem in the partitioning technique for solving the Schrödinger equation may be used in principle to determine upper and lower bounds to energy eigenvalues. Practical lower bounds of any accuracy desired may be evaluated by utilizing the properties of ``inner projections'' on finite manifolds in the Hilbert space. The method is here applied to the ground state and excited states of a Hamiltonian H=H0+V having a positive definite perturbation V. Even if inspiration is derived from the method of intermediate Hamiltonians, the final results are of bracketing type and independent of this approach. The method is numerically illustrated in some accompanying papers.
Optimum-Multiconfiguration Self-Consistent-Field Equations
Authors: Gilbert T. L.
Published: January 2005

Starting from a multiconfiguration wavefunction of the form Ψ=Σ lim p=1NApΦp,where Φp are antisymmetrized products constructed from a set of nN independent orbitals φip(x), i=1,···,n, p=1,···,N, it is shown that the variational equations for an ``optimum'' set of orbitals can be reduced to the form Fpφip−Σ lim j=1nφjpfjip=0.The fijp are Lagrangian multipliers and Fp are one-electron operators which depend on the first order density and transition operators, the one- and two-particle operators in the Hamiltonian, and the coefficients Ap. Orbitals belonging to different products are, in general, neither orthogonal nor identical, and the anti-symmetrized products will not, in general, be orthogonal. The operators Fp are invariant under arbitrary nonsingular linear transformations of the orbitals on the manifold for each determinant. They are not Hermitian. In the limiting case of a single configuration, the optimum multiconfiguration (OMC) orbital equations reduce to the Hartree—Fock equations.
Recent Developments in the Method of Different Orbitals for Different Spins
Authors: Pauncz Ruben
Published: January 2005

The alternant molecular orbital method and the nonpaired spatial orbital method have been compared. Some recent applications of the AMO method have been reported.
Electronic Structure of the Nitrite Ion and Related Species
Authors: Hirst D. M. , Linnett J. W.
Published: January 2005

The performance of a number of wavefunctions based on the molecular orbital and valence bond methods and that of nonpaired spatial orbitals (NPSO) has been examined for the four electrons occupying the π orbitals of the nitrite ion. The related two and three π-electron systems of NO2+ and NO2 have been investigated for the same nuclear arrangement as in the NO2− ion. The performance was judged by calculating (a) the electronic energy; (b) the contributions to this energy from the interelectron repulsion energy and the electron-core energy; (c) the overlap with the corresponding full configuration-interaction function; (d) the charge distribution. It was found that the NPSO method produced the most successful functions. The results have been discussed.
Natural Orbitals and Geminals of the Beryllium Atom
Authors: Smith Darwin W. , Fogel Sidney J.
Published: January 2005

The first- and second-order density matrices for Watson's 37-configuration beryllium wavefunction have been studied. Particular attention has been given to the form of the second-order density matrix and the way it changes in passing from a Hartree—Fock to a separated electron pair to a configuration-interaction wavefunction. The effect of intershell correlation in beryllium is interpreted as causing a forced delocalization of the natural geminals, and a splitting of the singlet—triplet degeneracy which would otherwise be present in the geminal occupation numbers.
Floating Spherical Gaussian Orbital Model of Molecular Structure. II. One- and Two-Electron-Pair Systems
Authors: Frost Arthur A.
Published: January 2005

The floating spherical Gaussian orbital (FSGO) model is applied to the He and Be atom isoelectronic sequences and to the molecules and ions: H2, He2+ +, HeH+, H3+, H4+ +, HeH−, LiH, and BeH+. Bond lengths are predicted generally to within 5% of accurate values. The He–He repulsive interaction is also calculated.
ESR and Optical Spectroscopy of CrO43− in Chlorospodiosite, Ca2PO4Cl
Authors: Banks E. , Greenblatt M. , McGarvey B. R.
Published: January 2005

Studies of the spectral properties of CrO43− ion in Ca2PO4Cl (chlorospodiosite) single crystals confirm the structural results established by single-crystal x-ray structure analyses. Detailed electron spin resonance measurements of a single crystal of Ca2(PO4, CrO4)Cl are described and the appropriate spin-Hamiltonian parameters determined. It is shown that the unpaired electron (3d1) in its ground state occupies a dz2 orbital, which is largely concentrated on the chromium atom. The visible and ultraviolet absorption spectrum of a single crystal of Ca2PO4Cl containing CrO43− is described and shown to be similar to the spectrum of MnO42−, which had been interpreted on the basis of a Ballhausen and Liehr molecular-orbital level scheme. The infrared absorption spectra show more splitting of the vibrational bands of the chromate (V) compound (Ca2CrO4Cl) than of the phosphate (Ca2PO4Cl), in agreement with the structural results which indicated a greater distortion of the CrO43− than that of the PO43− tetrahedra. The infrared spectra of spodiosites and related compounds with apatite structure are compared.
Quenching of Hg*(3P1) Atoms by Hydrogen Molecules Investigated by Phase-Space Theory
Authors: Yang Kang , Paden J. D. , Hassell C. L.
Published: January 2005

Phase-space theory is used to investigate product distribution and internal energy distribution among various products in the mercury-sensitized decomposition of hydrogen molecules. Calculated quantum yields at room temperature for H atoms, HgH, and undissociated hydrogen molecules are 0.52, 0.16, and 0.58, respectively. The H-atom yield is much lower than the possible maximum of 2.0 but agrees well with an experimental value of about 0.5. The majority of undissociated hydrogen molecules is produced in vibrationally excited states. In mercury-sensitized decompositions, these vibrationally hot H2 molecules may undergo reactions which were, in the past, attributed solely to H-atom reactions.
Valence-Bond Calculations of Triplet-State Energies and Spin Densities of Unsaturated Organic Molecules
Authors: Barfield Michael
Published: January 2005

A theoretical study of triplet-state organic molecules is given by means of the semiempirical valence-bond (VB) method. Triplet-state energies and spin densities are calculated by means of a VB bond-diagram method with integral parameters from studies of ground-state and spin-dependent properties. For the two- to eight-carbon polyenes reasonable agreement is obtained between the calculated ground to lowest triplet-state energy separations and the experimental absorption maxima. It is found that a reversal of the polyene single and double bond lengths significantly lowers the triplet-state energy because of effective correlation which tends to concentrate the positive spin density on the terminal carbons. A discussion is given of the various factors which influence dihedral twisting in the polyenes.
Calculations of Frequencies and Intensities of the Lattice Vibrations of Thiourea and Thiourea-d4
Authors: Takahashi Hiroaki , Schrader Bernhard , Meier Wilfried , Gottlieb Klaus
Published: January 2005

Frequencies of the lattice vibrations of the room-temperature modification of thiourea and deuterated thiourea have been calculated assuming a simple force field. The calculated frequencies are in good agreement with the observed frequencies in the Raman and far-infrared spectra. Approximate relative intensities of the lattice vibrations in both spectra have been calculated and used to check the assignments given by the frequency calculation. One of the intermolecular force constants, 0.173 mdyn/Å, seems to represent a fairly strong S···H–N hydrogen bond.
Thermal and Composition Expansion of Clathrates in the Ethylene Oxide—Water System
Authors: McIntyre J. A. , Petersen D. R.
Published: January 2005

Nonstoichiometric clathrate compounds of ethylene oxide and water form cubic phases of composition xC2H4O·46H2O, where the theoretical maximum x is 8. Through x-ray diffraction experiments, thermal expansion relations were established for several specific compositions (x = 1.08, 2.32, 3.72, 6.75) over the temperature range from −140° to −20°C. It was found that in each case, the relative thermal expansion of the clathrate was greater than that of normal ice over matching ranges. At any given temperature in the range studied, a sharp break was observed in the composition expansion curve at about x = 3, for which a reasonable explanation has been provided.
Crystalline Reflectance Spectra of Ion—Radical Salts at Room Temperature, at 77°, and at 4.2°K. I. Wurster's Blue Perchlorate
Authors: Anderson George R.
Published: January 2005

Polarized reflectance spectra of crystalline Wurster's blue (WB) perchlorate are reported at temperatures above and below the reported phase transition at 190°K of the ion—radical salt. The spectral evidence indicates the position of the first π—π* transition in the solid and uncovers an electronic band associated with the low-temperature phase of the solid in the near-infrared spectral range at approximately 11 000 cm−1. By comparing these spectra with the solution dimer spectrum of WB perchlorate of Hausser and Murrell and by observing the unique polarization of the band in the solid, arguments are advanced in favor of a ``dimer'' model for the solid in the low-temperature phase. Further implications of the observed polarization effects are discussed.
Emission from Organic Liquids Excited by Electron Impact
Authors: Carter J. G. , Christophorou L. G. , Abu-Zeid M-E. M.
Published: January 2005

Liquid benzene, toluene, and 2-ethyl naphthalene were excited at room temperature with intense electron beams (average energies, 4–36 keV) and in all cases the scintillation emission was a structureless band attributed to excimers. A comparison is made of the emission spectra obtained this way with the photofluorescence spectra and those obtained under x-ray excitation. Ion recombination is believed to be the origin of the excimeric emission under electron bombardment. The conclusion is drawn that the emission from organic liquids is strongly dependent upon the mode and intensity of excitation.
Frequency Factor for the Arrhenius Form of the Rate Constant for Cyclobutane
Authors: Retzloff D. , Coull J.
Published: January 2005

Slater's theory is developed starting from the solution to Lagrange's equations of motion and based on symmetry coordinates. From the fundamental frequencies of cyclobutane the potential constants for the Eu vibrations are calculated and a normal-coordinate analysis of cyclobutane is made. Using this analysis and Slater's theory, the frequency factor in the Arrhenius form of the rate constant is predicted for three different sets of critical coordinates. Using P1=ΔR12+ΔR34 as a critical coordinate, a value for the frequency factor two orders of magnitude less than the reported experimental values is predicted. When P2=ΔR12+ΔR23 is used as a critical coordinate, a frequency factor of an order of magnitude less than the experimental values is predicted. With P3=0.891124 ΔR12+0.761947 Δr2 as the critical coordinate, a frequency factor of ½ the experimental values is predicted. An examination of the activation energy which ranges between 61.8 and 65 kcal/g-mole shows that the degree of distortion of cyclobutane at the critical configuration is sufficiently large to warrant the consideration of anharmonic terms in the potential energy. Investigation of the pressure dependence of K/K∞ shows that a curve identical in shape to the experimental curve is obtained when P3 is the critical coordinate and the effective number of oscillators is 16.
High-Temperature Gas-Kinetic Study of Carbonyl Sulfide Pyrolysis Performed with a Shock Tube and Quadrupole Mass Filter
Authors: Hay Arthur J. , Belford R. Linn
Published: January 2005

A quadrupole mass filter coupled to a shock tube, described in Part I, was used to study the chemical kinetics of the thermal decomposition of carbonyl sulfide in the temperature range 2000° to 3200°K at total densities of 2 to 3×10−6 mole/cc. The equipment previously described was unable to detect concentrations of carbonyl sulfide low enough to prevent clogging of the sampling leak by solid sulfur. This difficulty was eliminated by the design of a new rapid-pumping ion source, described here, which can detect 5×10−10 mole/cc OCS in the shock tube. Mixtures of 0.5%, 2%, and 4% OCS in argon were heated by reflected shocks. In the 0.5% mixtures the ion currents of all the principal species, OCS, CO, S, S2, CS, and SO, were monitored. For the 2% and 4% mixtures only the ion current of OCS was monitored. In each dynamic experiment, the mass filter was tuned to follow the concentration of a single species. A large number of experiments was performed at different temperatures for each species with the following results: (a) The mechanism between 2000° and 3200°K at low pressures involves a unimolecular, second-order rupture followed by two bimolecular atom abstractions: OCS+Ar→ lim k1CO+S+Ar,    ΔH00=71.5 kcal/mole,S+OCS→ lim k2CO+S2,        ΔH00=−29.5 kcal/mole,S+OCS→ lim k3CS+SO,        ΔH00=22.4 kcal/mole.(b) In the 0.5% mixtures, S atom did not approach a steady-state value in the available testing time. (c) For 0.5% mixtures of OCS, k1 is approximately half the apparent k1 for the 2% and 4% mixtures. This implies that for the high concentrations, k2 (S) rapidly approaches k1 (Ar). (d) The critical activation energy for the rate-determining step is not known. However, for 0.5% mixtures and an assumed critical activation energy of Ea=71.5 kcal/mole, k1 fit a quantum RRKM calculation with 1% collisional deactivation efficiency. This result is well represented by the following Kassel expression: k1=1.11×1011(T/deg)1/2[71.5(kcal/mole)/RT]1.87×exp[−71.5(kcal/mole)/RT]cc/mole·sec.Further arguments suggest Ea to lie between 71.5 and 82 kcal/mole. (e) An estimate of k2=6.0×1011 cc/mole·sec at 2570°K is consistent with all the behavior observed. From k2 an activation energy of 27±6 kcal/mole is estimated. (f) The difference in activation energy between Reactions (3) and (2) is ∼19 kcal/mole.
Determination of Accurate Single-Center Expansions with Slater-Type Orbitals: The H3 System
Authors: Hayes Edward F. , Parr Robert G.
Published: January 2005

Electronic wavefunctions are determined for the linear symmetric H3 system. The basis functions are Slater-type orbitals centered on the central proton. For separations of 1.6, 1.7, and 1.8 bohr between adjacent protons, total energies of −1.62648, −1.63074, and −1.62897 a.u. are found using 70-term configuration-interaction wavefunctions. These energies are each in error by about 15 kcal/mole. Detailed analysis is made of the convergence. It is concluded that the single-center Slater-type orbital basis set is not particularly suited for the simple configuration interaction method for determining many-electron wavefunctions. It is suggested that higher accuracy might be achieved by using groups of Slater-type orbitals, taken from off-center hydrogen-atom expansions.
Generalized Time-Dependent Hartree Theory and the Coupling between Sigma and Pi Electrons
Authors: Harris Robert A.
Published: January 2005

When the potential energy between sigma and pi electrons conserves both sigma and pi electrons, a generalization of time-dependent Hartree theory may be used to obtain all the properties of the coupled sigma—pi system. The susceptibilities of the coupled system are shown to satisfy equations identical to those found in the theory of the spectroscopy of dimers made up of nonequivalent monomers. Fredholm perturbation theory is used to obtain excitation energies and excitation strengths.
Relation between the Electronic Structure of Tin in Its Compounds and the Isomer Shifts in Mössbauer Spectra
Authors: Goldanskii V. I. , Makarov E. F. , Stukan R. A.
Published: January 2005

Expressions relating isomer shifts in Mössbauer spectra with the electronic structure of tin in its compounds are obtained. These expressions give a description of isomer shifts for chemical compounds of different types: tetravalent tin when there is π bonding (tin tetrahalogenides), tetravalent tin in the absence of π bonding (compounds where tin is bound with alkyl, aryl, and carbonyl metal radicals), bivalent tin, etc. The expressions obtained were used for analysis of the electronic structure of tin in compounds of these classes. For tetravalent tin compounds with π bonding the change of isomer shift δ towards negative values (with respect to α-Sn) is found to be accounted for by a decrease, and for compounds without π bonds by an increase in the number of valence 5s electrons (S) at S>1.
Spin—Lattice Relaxation in Dilute Gases. I. Proton Relaxation in HCl, HBr, and HI
Authors: Tward E. , Armstrong R. L.
Published: January 2005

Proton spin—lattice relaxation times have been measured in gaseous HCl, HBr, and HI as a function of temperature and pressure in the dilute-gas region. The observed temperature dependence is consistent with that expected for relaxation dominated by a spin—rotation interaction. Effective cross sections for the transfer of angular momentum to molecular rotation during collisions are deduced. The cross sections are large, indicating the importance of the long-range forces between the molecular dipole moments.
Collision Cross Sections of Hydrogen and Other Ions as Determined by Ion Cyclotron Resonance
Authors: Wobschall Darold , Fluegge Robert A. , Graham John R.
Published: January 2005

Through determinations of the widths of ion cyclotron resonance lines as a function of pressure and electric field strengths, the ion—molecule collision cross sections of H+, H2+, H3+, He+, Ar+, N2+, N+, O2+, O2−, and O− were obtained. Agreement with dc mobility data was found. In particular, the minimum in collision frequency for H3+ in H2 at E/P0=60 V/cm·torr was confirmed. The cross sections for H2+ in H2 are 275 and 68 Å2 at low and high E/P, respectively.
Theory of Electron Collisions with Homonuclear Diatomic Molecules
Authors: Rozsnyai Balasz F.
Published: January 2005

Electron scattering phenomena are investigated in the first Born approximation for homonuclear diatomic molecules. The two-center integrals that must be evaluated to find the scattering cross sections are calculated in an approximation which is accurate for small momentum transfer. Application is made to the elastic scattering in H2 and to some excitational scattering in H2+, H2, and N2.
Senftleben—Beenakker Effect for the Viscosity of a Dilute Gas of Diamagnetic Diatomic Molecules
Authors: McCourt F. R. , Snider R. F.
Published: January 2005

The effect of an external magnetic field on the viscosity of a dilute gas of rotating diamagnetic diatomic molecules is presented. A complete tensorial development in irreducible Cartesian tensors is given, the rotational states being treated quantum mechanically and the effect of inelastic collisions included. The magnetic-field dependence is given in terms of reduced square-bracket integrals and the variable H/p, where H is the magnetic-field strength and p, the equilibrium pressure of the gas. In this way it has been possible to include the cross effects existing between shear and bulk viscosities and which arise only in the presence of a magnetic field.
Interpretation of Quadrupole Splittings and Isomer Shifts in Hemoglobin
Authors: Weissbluth M. , Maling J. E.
Published: January 2005

It is shown that the major features of the quadrupole splitting observed in the Mössbauer spectra of several derivatives of hemoglobin are explainable on the basis of the molecular orbital calculations of Zerner, Gouterman, and Kobayashi [Theoret. Chim. Acta 6, 363 (1966)] on iron porphin complexes while attempts to use ligand-field theory for the same purpose have been unsuccessful. Difficulties in the interpretation of isomer shifts are discussed.
Low-Energy, Large-Angle Electron-Impact Spectra: Helium, Nitrogen, Ethylene, and Benzene
Authors: Doering John P. , Williams Albert J.
Published: January 2005

Electron-impact spectra taken at a fixed scattering angle of 90° and a variety of energies from 10 to 40 eV are reported for helium, nitrogen, ethylene, and benzene. Forbidden singlet—triplet transitions were observed in all the systems studied at all energies. In all cases, the scattering cross sections for various transitions undergo large relative changes near threshold. We find that singlet—triplet transitions become a very important part of the total inelastic scattering cross section below 20 eV. In helium, the spectrum changes radically near threshold. In nitrogen, singlet—triplet transitions dominate the spectrum at energies less than 20 eV. Previous results on the presence of a singlet—triplet transition in ethylene at 4.4 eV have been confirmed. The 6.5-eV ethylene ``mystery band'' transition was not observed at energies at low as 10.9 eV. In benzene, the lowest triplet state is observed near 3.9 eV as well as the three lowest singlet states. The general utility of the very large angle scattering method is discussed.
Classical Theory of Rotational Relaxation of Diatomic Molecules
Authors: Berend George C. , Benson Sidney W.
Published: January 2005

The classical equations of motion of colliding diatomic molecules are solved rigorously in two dimensions to obtain the energy transferred to the internal degrees of freedom during collision. The model considers up to four atoms bound by six atom-centered Morse potentials. The effect of varying range parameters is noted. The relaxation of H2 with He and H2 collision partners, D2 with He, and pure N2 and O2 is studied. The vibration—rotation energy exchange is evaluated and accounted for. The resulting relaxation times and average collision numbers agree well with empirical findings. In the temperature range 100°—700°K, except for N2 and O2, a negative temperature dependence was obtained. The contrary is expected at higher temperatures where the relaxation times are functions of the inverse collision frequency only.
Vacuum-Ultraviolet Absorption Spectrum of Polystyrene
Authors: Partridge Roger H.
Published: January 2005

The vacuum-uv absorption spectrum of atactic and isotactic polystyrene is reported from 584 Å to onset of absorption at 2800 Å, and is compared with previous data from reflection and electron-energy loss measurements. Three of the electronic transitions in this region are assigned to excitations of the benzenering π electrons and the fourth to excitation of all the σ- and π-bonding electrons of the material; previous assignments of some transitions as due to collective excitations of free electrons are rejected. The spectrum of the solid is essentially as would be expected from gas-phase measurements apart from strong evidence of exciton interaction in one of the π-electron transitions.
Anomalous Melting Transition in the Significant Structure Model of Liquids
Authors: Tuerpe Dieter R. , Keeler R. N.
Published: January 2005

The significant structure theory of Eyring et al. has been used to predict the melting curve of argon at high pressure. Anomalous results were obtained, which indicate that the model may not be suitable to describe the phenomenon of melting. Possible reasons for these results are discussed.
Liquid—Vapor Interface Potential for Water
Authors: Stillinger F. H. , Ben-Naim A.
Published: January 2005

The water molecule has been idealized as a point dipole plus point quadrupole, encased in a spherical exclusion envelope. Classical electrostatics has been applied to the determination of the potential field surrounding such a molecule in the wide interfacial region between the liquid and vapor phases, just below the critical temperature. From this result, the mean torque on the molecule in this inhomogeneous region follows, and produces a spontaneous interfacial polarization. The consequent potential difference across the interface has thus been evaluated at several temperatures, and demonstrates the tendency for surface water molecules to orient their protons away from the vapor and into the liquid. A related optical experiment is suggested, involving electric-field dependence of reflected-light ellipsometry.
Generation and Trapping of Charge Carriers in a Localized Model for Dye Photoconductors
Authors: Nelson R. C.
Published: January 2005

In solid photoconductive dyes the energy of the conduction electron is appreciably greater than that of the excited ``optical electron.'' In favorable cases, the energy levels of the dye are almost unaffected by its state of aggregation, so that the ionization energy of the bulk dye is only slightly less than that of a single molecule. Both these facts argue for a localized-process model for photoconductivity in dyes. Some of the implications of such a model for quantum yields of charge carriers and for the kinetics of photoconductivity are discussed.
Optical Absorption and Fluorescence Spectra of EuF3
Authors: Caspers H. H. , Rast H. E. , Fry J. L.
Published: January 2005

The absorption spectrum of EuF3 powder has been obtained in the region from 1.8–10μm. By means of a diffuse reflection technique, the crystal sublevels of the 5D0,1,2 states were obtained at liquid-nitrogen temperature. Fluorescence from the 5D0 state and from some of the crystal sublevels of the 5D1,2 states to the 7FJ(J = 0, 1, 2, 3, 4, 5, 6) states has been observed. From an analysis of the observed transitions, it was possible to assign 2J+1 Stark components to the observed states, in agreement with the Cs site symmetry for Eu3+ in EuF3. The intermediate coupling free-ion energy levels for Eu3+ have been calculated, including the interactions of all the multiplets of the f6 configuration. Values of F2=351.5 cm−1, F4=57.64 cm−1, F6=5.625 cm−1, and ζ=1328 cm−1 are found to give the best over-all agreement between the observed and calculated energy levels.
Microwave Spectra of Nitrogen-Containing Molecules. III. Structure, Dipole Moment, Quadrupole Coupling Constants, and Barrier to Internal Rotation of trans-Propyleneimine
Authors: Li Ying Sing , Harmony Marlin D. , Hayes Donald , Beeson E. L.
Published: January 2005

The microwave spectrum of trans-propyleneimine has been studied in the ground state and the first excited state of the methyl torsion. Ground-state rotational constants for the normal isotopic species and for the C3H6N—D species are as follows: A = 16 892.59, B = 6533.63, C = 5761.37 and A = 16 082.31, B = 6338.70, C = 5537.81 MHz, respectively. The height of the barrier to internal rotation has been found to be 2608±26 cal/mole by analysis of splittings of ground-state and first excited-state lines. Measurements of the Stark effect have led to a total dipole moment of 1.57 D, and analysis of hyperfine structure has given the quadrupole coupling constants of the 14N nucleus: χaa=0.67±0.02, χbb=2.24±0.02, χcc=−2.91±0.01 MHz. An estimate has been given of the quadrupole coupling constants in the principal axis system of the electric-field-gradient tensor, and the molecular structure has been discussed.
Cancellations Occurring in the Calculation of Transition Energies by a Perturbation Development of Configuration Interaction Matrices
Authors: Malrieu J. P.
Published: January 2005

Two theorems are demonstrated: (1) The coefficients of most of the (2n+1) excited configurations in the nth- order correction to any well separated monoexcited state are [multiplied by a factor 2−½], equal to the coefficients of most of the 2n excited configurations in the nth order correction to the wavefunction of the ground state; (2) while the calculation of the nth-order correction to the energy of any state implies (2n)-uple summations over the molecular orbitals, the nth-order correction to the transition energy between the ground and a monoexcited state only implies (2n−1)-uple summations over the molecular orbitals. These two theorems are only valid when n is smaller than the number of particles in the system.
Ultrasonic Absorption in Propionic Acid
Authors: Tatsumoto Nobuhide
Published: January 2005

The ultrasonic relaxational absorption in methyl propionate solutions of propionic acid has been studied in the frequency range 0.5–95 Mc/sec at concentrations varying from 0 to 1 mole fraction. The relaxation frequencies are 1.8, 2.2, 2.8, and 3.4 Mc/sec independent of the concentration at 20°, 25°, 30°, and 35°C, respectively. The independence of fmax on the concentration indicates that the ultrasonic relaxational absorption is associated with the uni—unimolecular reaction. The kinetic values have been calculated for the uni—unimolecular reaction by Tabuchi's theoretical equations. The forward and backward rate constants are 2.3×105 and 1.06×107 sec−1 at 20°C for pure propionic acid, respectively, and the heat of reaction is 4.7 kcal/mole of dimer. The value of Cpr is equal to that of Cvr, since the volume change resulting from reaction is absent. The consideration for the type of reaction, the magnitude of heat of reaction, and no volume change associated with reaction have led us to the conclusion that the ultrasonic absorption in propionic acid is associated with a breakage of one of two hydrogen bonds. The solvent effect on the relaxation mechanism has also been studied in various solvent solutions of propionic acid. The relaxation frequency fmax does not change with increasing concentration in polar solvent solutions, whereas it decreases with increasing concentration in nonpolar solvent solutions.
Quantum Mechanics of the H2–H2 Interaction. IV. A Self-Consistent Group Calculation with Strong Orthogonal Group Functions
Authors: Magnasco V. , Musso G. F.
Published: January 2005

A self-consistent group calculation of the orientation dependence of short-range intermolecular forces in the H2–H2 system has been carried out using strong orthogonal Weinbaum-like functions constructed from a set of four symmetrically orthogonalized 1s orbitals. The one-configuration approximation to the wavefunction describing the electronic ground state of the composite system has been improved by admitting localized excitations on the two molecules. The resulting intermolecular energy is for some relative orientations slightly better and for others worse than that obtained in the corresponding nonorthogonal calculation, but the orientation dependence of the interaction proves to be definitely worst in the orthogonal case. Only about 60%of the ``barrier'' obtained with the one-configuration nonorthogonal SCF—GF calculation is accounted for by the corresponding strong orthogonal wavefunction. The resolution of the one-configuration interaction into Coulomb and penetration components after the distortion effects resulting from the forced orthogonalization of the orbital basis have been removed by means of a proper matrix technique shows that the largest error is embodied in the one-electron contribution to the penetration term. The strong orthogonal SCF—GF—CI approach in its current formulation proves therefore not to be adequate in giving a satisfactory description of the orientation dependence of short-range intermolecular forces, at least when the penetration interaction is the largest contribution.
Electrochemical Oxidation of Nitrosobenzene and Derivatives in Organic Medium. Electron Spin Resonance of the Cation—Radicals
Authors: Cauquis G. , Genies M. , Lemaire H. , Rassat A. , Ravet J. P.
Published: January 2005

The ESR spectra of the radical cations of nitrosobenzene, 2,4,6,d-3-nitrosobenzene, and 2,4,6,-tri-t-butyl-nitrosobenzene have been observed by means of continuous electrolysis in organic media. Strong couplings with nitrogen (aN=37.0 Oe) and one meta proton (aH=3.8 Oe) are observed, leading us to propose that they are σ-radicals; by contrast, the radical—anion of nitrosobenzene is a π radical. The difference is explained on the basis of the electronic structure of the neutral parent compound.
Thermal Diffusion in a Loaded Sphere—Smooth Sphere Mixture: A Model for 4He–HT and 3He–HD
Authors: Sandler Stanley I. , Mason E. A.
Published: January 2005

The kinetic theory of a mixture of loaded spheres and smooth spheres of equal mass is developed as a model for thermal diffusion in the systems 3He–HD, 4He–HT, and 4He—D2. The inelastic effects in the loaded-sphere collisions are sufficient to explain the experimental ``anomalies'' observed in thermal diffusion involving the asymmetric hydrogen isotopes. The effects of spin polarization, though not dominant, are not negligible.
Electron-Impact Ionization Cross Sections. IV. Group IVb Atoms
Authors: Lin Sin-Shong , Stafford Fred E.
Published: January 2005

The electron-impact ionization cross sections for Ag, Ge, Sn, and Pb have been measured relative to one another by quantitatively vaporizing known amounts of material in a mass spectrometer. For 60-eV impacting electrons, the relative single ionization cross sections are found to be (1.00), 1.46±0.3, 1.46±0.16, and 1.43±0.1, respectively. The corresponding secondary-electron multiplier gains for 6.4-keV ions are (1.00), 1.04, 1.03, and 0.79, all ±5%. These experimental cross-section ratios are compared to the best available calculated values. From the absolute cross section for Pb of Beilina et al., that for Ag is 5.6×10−16 cm2.
Electron-Impact Ionization Cross Sections for Silver
Authors: Crawford C. K. , Wang K. I.
Published: January 2005

Absolute electron ionization cross sections have been measured for silver using a single-crossed-beam method. A silver beam was generated by vaporizing silver shot in a small high-temperature Knudsen cell, and passed through an ionization chamber where it intersected an electron beam at right angles. By applying suitable potentials to the chamber, ions could be accelerated either into a Faraday-cup total-ion collector, or into a large quadrupole mass spectrometer. After passing through the chamber, the silver beam was condensed in a weighable atomic-beam trap. Absolute cross sections were obtained by integrating the total-ion collector current, and calculating the silver beam intensity from the weight increase of the trap. The measured values at 75 eV are (4.65±1.0)×10−16cm2 for the formation of Ag+ and (4.75±3.0)×10−17cm2 for the formation of Ag++. The value for Ag+ agrees within experimental error with the extrapolated experimental values of other workers, but disagrees with theoretical predictions.
Luminescent Properties of Hexafluoroacetone. I. Fluorescent Lifetime and Fluorescent Enhancement in the Gas Phase
Authors: Ware William R. , Dutton Melvyn L.
Published: January 2005

The fluorescence lifetime of hexafluoroacetone has been measured as a function of temperature and pressure by the direct stroboscopic technique. In addition, fluorescence enhancement was confirmed by steady-state measurements. In both the transient and steady-state experiments, the excitation wavelength was 3130 Å. The extent to which these results are consistent with the known photochemistry of hexafluoroacetone is discussed.