bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Transition Moments for the A → X, B→ X, and B→ A Transitions in CO+ and the A← X and B← X Moments for the CO→ CO+ Systems; Absolute Cross Sections for the Absorption Processes
Authors: Judge D. L. , Lee L. C.
Published: February 2004

The A→ X, B→ X, and B→ A bands of CO+ have been excited using monochromatic photons and the band intensities measured. Using such data the variation of the electronic transition moments for these above emission bands as well as for the absorption bands CO(X 1Σ+, v″=0) → CO+ (A 2πi, v′ = 0–8) and CO+ (B2Σ+, v′ = 0, 1) have been determined. Further, the specific cross sections for the absorption processes have been determined by measuring the total emission intensity in the band system through which the upper state decays. The band intensity measurements and the derived results are presented in the ensuing discussion.
Vibrational Energy Transfer Processes in Shock-Heated Binary Gas Mixtures of CO with CO2, N2O, and COS
Authors: Borrell Peter , Millward G. E.
Published: February 2004

The vibrational relaxation rates of binary mixtures of CO with the additives CO2, N2O and COS have been measured in incident shock waves over a temperature range 1200–2000°K. The fundamental vibration of CO was found to be closely coupled to the asymmetric stretching vibration in each additive and so the rate determining step was not V-V energy exchange between CO and the additive, but intramolecular energy transfer within the polyatomic species. For CO/CO2 this step is CO2(001)+CO lim →k4CO2(ν2/ν1)+CO,where the forward rate constant is given by CO(CO2) log10(k4/atm−1· sec−1)=8.69–28.1 T−1/3. For the other additives the rate constants for the analogous reactions are given by CO(N2O) log10(k4/atm−1· sec−1)=8.50–23.6 T−1/3 CO(COS) log10(k4/atm−1· sec−1)=7.56–8.40 T−1/3. These results are in accord with those from recent laser fluorescence measurements and can be reconciled with shock measurements on other systems.
Absolute Rate Constant for the Reaction H+H2CO
Authors: Ridley B. A. , Davenport J. A. , Stief L. J. , Welge K. H.
Published: February 2004

The photolysis of formaldehyde in the pronounced absorption region ∼1700–1760 Å has been investigated. The production of H atoms has been established by direct observation using pulsed photolysis and time dependent observation of the Lyman-α resonance fluorescence at 1216 Å. From the measurement of the H-atom decay under pseudo-first order conditions the rate constant for the reaction H+H2CO→ H2+HCOhas been obtained. The result is 5.4± 0.5× 10−14 cm3 molecule−1· sec−1 at 297°K.
Photophysical Processes in Polymers. IV. Excimer Formation in Vinylaromatic Polymers and Copolymers
Authors: Fox R. B. , Price T. R. , Cozzens R. F. , McDonald J. R.
Published: February 2004

Excimer formation has been investigated in polystyrene, poly(1-vinylnaphthalene), poly(2-vinylnaphthalene), and in copolymers of 1-vinylnaphthalene with styrene and with methyl methacrylate. Solid films as well as solutions were studied over the temperature range 77–298°K. In the solid polymers, interchain excimer formation is superimposed on the intrachain interaction observed in dilute solutions; intrachain excimer formation is essentially unaffected by the solvent in fluid solutions. Conformations that lead to excimer interaction in a solid solution are fixed by the temperature at which the solid is formed. Activation energies for intramolecular excimer formation for these polymers are somewhat less than those for the corresponding two-unit model compounds and much less than those for the single-unit model compounds. While excimer sites act as efficient singlet traps for intramolecularly migrating energy and act to decrease the triplet yield, they do not present a barrier to the transfer of energy to a deep trap within the polymer chain.
Effect of Configuration Interaction on Crystal Field Splitting of Fe2+ Ion
Authors: Basu C. , Majumdar D. , Ghosh U. S.
Published: February 2004

The effect of excited configurations 3d54p, 3d54d, and 3d54f on the crystal field levels Γ3 and Γ5 of tetrahedral and octahedral Fe2+ ion via crystal field interaction has been discussed. The shift of the Γ3 and Γ5 levels due to configuration interaction has been estimated in the two cases within the framework of crystal field model carrying out the perturbation calculation up to second order and using Slater functions for the radial integrals. Such calculation shows that in the case of tetrahedral Fe2+ ion in ZnS, the net effect of the excited configurations 3d54p, 3d54d, and 3d54f on the crystal field spectra is to close up the levels Γ5 and Γ3 by an appreciable amount of about 1000 cm−1 and the major part of the contribution comes from 3d54p. In the octahedral case also (Fe2+ in MgO), the effect arising from 3d44d only is not negligible although comparatively smaller, the separation (Γ3−Γ5) is narrowed by about 380 cm−1.
Magnetic Circular Dichroism of Cytochrome c
Authors: Sutherland J. C. , Klein M. P.
Published: February 2004

We have measured the magnetic circular dichroism of ferrocytochrome c from 350 to 1000 nm and the MCD of ferricytochrome c from 350 to 750 nm. We present expressions for the shapes of MCD and absorption spectra in the presence of a magnetic field of randomly oriented molecules for the general case in which the absorption band is split in zero field, and the two components of the split band have different intensities. After correcting for the effects of unresolved zero-field splitting, we find that the ``angular momentum'' of the Q00 band of Fe(II) cyt c is 7.9 μB. We show that the 23-fold decrease in the MCD of the Q00 band upon oxidation of Fe(II) to Fe(III) is due to about a fivefold increased bandwidth while the oscillator strength and angular momentum remain essentially unchanged. The increase in bandwidth may reflect greater mixing of the porphyrin orbitals with the d levels of the iron ion in the oxidized state. The MCD of Fe(II) cyt c in the near infrared (600–1000 nm) can be decomposed using essentially the same components previously used to decompose the CD if some components are presumed degenerate. The angular momenta of the degenerate components are in the range expected for d→ d transitions. The CD and MCD of the 695 nm band of Fe(III) cyt c are both relatively weak and suggest, respectively, that the transition is electric dipole allowed and nondegenerate.
Hyperfine Structure of Indium Fluoride
Authors: Hammerle Robert H. , Van Ausdal Ray , Zorn Jens C.
Published: February 2004

The radiofrequency spectrum of the indium fluoride molecule, 115In19F, has been measured with a high resolution molecular beam electric resonance spectrometer. We determined the hyperfine structure in the J=1 and the J=2 rotational states of several vibrational levels under conditions of very weak external electric and magnetic fields. The ∼700 MHz electric quadrupole interaction constant of the indium nucleus changes by 0.010(1) MHz between adjacent rotational states. We looked for, but did not find, an electric hexadecapole interaction of the indium nucleus; the upper limit for the (hexadecapole) interaction constant is 2 kHz.
Bounds on Solutions of the Poisson-Boltzmann Equation near Infinite Dilution-The Moderately Charged Case
Authors: MacGillivray A. D.
Published: February 2004

Upper and lower bounds on solutions of the nonlinear Poisson-Boltzmann equation are obtained for the case where the so-called surface charge parameter is less than unity (the moderately charged case). The relationship of these bounds with Manning's limiting law theory for polyelectrolytes is discussed. In particular, we are able to provide rigorous justification (different from Manning's own justification which is based on cluster theory) for Manning's use of the Debye-Hückel approximation.
Surface Structure of a Square-Well Fluid
Authors: Toxvaerd Soren
Published: February 2004

The perturbation expansion for fluids is formulated as an expansion of the chemical potential. The interface density profile between the uniform bulk phases of a square-well fluid is obtained by requiring that the chemical potential is constant in the interface. The profile is compared with the profile obtained from the Born-Green-Yvon-Bogolyubov integrodifferential equation in the density and with the profile obtained by minimizing the excess free energy of the interface. The density profiles obtained from the three different approaches are all in mutual agreement and show that the interface density decreases monotonically and rapidly for temperatures far from the critical point.
Reactions of H2O+ and D2O+ with Molecular Hydrogen. I. Proton Affinity of Hydrogen
Authors: Cotter R. J. , Rozett R. W. , Koski W. S.
Published: February 2004

The cross section of the ion molecule reaction H2O++H2→ H3++OH and its deuterium counterpart was studied over an energy range 2–100 eV using a tandem mass spectrometer. The measurements permitted a determination of the proton affinity of H2 of 4.37± 0.05 eV and 4.50± 0.05 eV for D2. The energy threshold values indicate that the reaction is proceeding by complex formation at low energies.
Density and Viscosity of Liquid ND3
Authors: Alei M. , Litchman W. M.
Published: February 2004

The density and viscosity of liquid ND3 have been measured over the temperature range from +30° to −25° and compared with the density and viscosity of liquid NH3. At any given temperature, the ratio of densities ρND3/ρNH3 is 1.187± 0.001 and the ratio of viscosities ηND3/ηNH3 is 1.20± 0.01. The fact that both ratios are independent of temperature suggests that the strengths of intermolecular interactions are essentially the same in the two liquids and that the density and viscosity differences are to be attributed to differences in molecular size and mass. The density ratio indicates that the molecular volume of NH3 in the liquid is ∼ 1% larger than that of ND3 while the viscosity ratio indicates that the viscosity varies directly as M/Vm (Vm=molar volume) for these two liquids.
Product Internal State Distributions from Interactions of Metastable Ar with N2
Authors: Cosby P. C. , Moran T. F.
Published: February 2004

Internal energy state distributions of the products from reactions of metastable Ar(3P2.0) atoms with N2(X 1Σg+) molecules have been computed from a statistical phase space treatment of the interactions. Calculated rotational and vibrational distributions have been compared with those measured in recent spectroscopic experiments involving metastable Ar atoms. For strongly exothermic reactions producing N2(B 3Πg, v′, J′) molecules, the computed vibrational distribution is significantly broader than that measured experimentally. The corresponding vibrational and rotational distributions calculated for slightly exothermic N2(C 3Πu, v′, J′) channels are in qualitative accord with experimental distributions; however, some features present in the experimental product distributions are not reproduced by the statistical model.
Valence Electron Studies with Gaussian-Based Model Potentials and Gaussian Basis Functions. I. General Discussion and Applications to the Lowest s and p States of Li and Na
Authors: Schwartz Maurice E. , Switalski Jurgen D.
Published: February 2004

A new model potential for one-valence-electron atoms is introduced. It consists [Eq. (6)] of a core Coulomb potential modified by the addition of a Gaussian screened Coulomb potential. This potential has the desired features outlined for a model potential, and it has particularly convenient and simple mathematical properties when used with Gaussian basis functions. Since the smooth valence orbitals are sought, Gaussian functions are a good basis set because their deficiencies in nuclear regions do not enter the problem. The potential is calibrated to experimental energies for the 2s and 2p states of Li and 3s and 3p states of Na, using extended basis sets. The model Hamiltonians so defined are used with a variety of more modest basis sets to determine pseudowavefunctions. Based on comparisons with ab initio orbitals, energy analyses, radial density calculations, and overlap and expectation value calculations, the conclusion is that good valence pseudowavefunctions can be obtained by this approach with relatively small basis sets. The approach looks promising for valence-only molecular studies.
Theoretical Approach to Potential Energy Functions for Linear AB2 and ABC and Bent AB2 Triatomic Molecules
Authors: Anderson Alfred B.
Published: February 2004

Let the coordinate system for a linear AB2 triatomic molecule have its origin on the A nucleus with R1 the distance to one B nucleus, R2 the distance to the other, and θ the apex angle. Then a working formula for the Born-Oppenheimer potential energy near equilibrium, W(R1, R2, θ), is W(R1, R2, θ) =WD(R1)+WD(R2)+A/|R3|N−B/(R1+R2)N,where W D(R1) and W D(R2) are potential functions for the ground state diatomic molecule AB, R3 is the vector sum R1+R2, A and B are constants and N is an integer. The potential energy for linear ABC tri-atomic molecules is given by Eq. (i) with R2 [or R1] scaled: R2→ η R2. Equation (i) is tested for CO2, CS2, OCS, HCN, and N2O by predicting all force constants up to fourth order except for the harmonic bending constant which is used in the parameterization. For bent AB2 molecules the working formula for the potential energy is W(R1, R2, θ) = WD(R1)+WD(R2)+A/|R3|N−B/(R1+R2)N+C/|R3|M−Aθ cos(θ − θe), (M≠ N),where θe is the equilibrium angle. Equation (ii) is tested for H2O, SO2, and O3 by predicting all force constants up to fourth order except for the harmonic bending and stretch-bend interaction constants which are used in the parameterization. A theory is presented for the presence of the W D(R) components in Eqs. (i) and (ii). It is suggested that the inverse |R3| terms partially represent averaged multipole interaction energies while the inverse (R1+R2) terms and angular term in Eq. (ii) partially represent valence orbital effects. The formulas for the parameters in Eqs. (i) and (ii) are given. Suggestions for writing down potential functions for larger molecules are included.
Monte Carlo Classical Trajectory Calculation of the Rates of F-Atom Vibrational Relaxation of HF and DF
Authors: Thompson Donald L.
Published: February 2004

Rates of F-atom vibrational relaxation of HF and DF have been calculated for the temperature range 600–2000°K using Monte Carlo classical trajectory methods. The processes F+(D)HF(v)→ F+(D)HF(v−1), where v=1, 3, and 5 and F+HF(0)→ F+HF(1) were investigated. Agreement with available experimental data is excellent. The calculations show that vibrational de-excitation is due to vibration-rotation transfer and that excitation is due to translation-vibration transfer. Multiple-quantum transfers are found to occur in de-excitation of higher vibrational levels. A semiempirical valence-bond potential-energy surface was used. No adjustments were made to the surface to cause agreement between calculated and experimental energy-transfer results.
Laser Induced Infrared Fluorescence: Thermal Heating, Mass Diffusion, and Collisional Relaxation in SF6
Authors: Bates Richard D. , Knudtson J. Thomas , Flynn George W. , Ronn A. M.
Published: February 2004

Experimental results of the study of 10-μ and 16-μ laser induced fluorescence in SF6 and SF6-rare gas mixtures are presented. The fluorescence at both wavelengths is found to exhibit a fast and a slow decay process. The major features of the experimental fluorescence decay curves are well described by a simple model with only two energy levels. The rate equations for this model system include terms which couple collisional relaxation with heat and mass transport. The fast fluorescence decay process at each wavelength is found to be characteristic of binary collisional deactivation. The rate of decay of the slow process, however, is controlled by transport of both heat and mass to the wall of the fluorescence cell with heat transport being the dominant effect. The experimental results and the analysis based on a two level model system are consistent with a two step vibrational deactivation mechanism. The first step is a rapid equilibration of the vibrational modes. The second step is a somewhat slower equilibration of vibrational and translational degrees of freedom.
Cross Sections and Interpretation of Dissociative Attachment Reactions Producing OH−, O−, and H− in H2O
Authors: Melton Charles E.
Published: February 2004

Dissociative-electron-attachment cross sections for the production of OH−, O−, and H− from water vapor have been determined. These cross sections are discussed within the framework of resonance scattering theory. The relatively low cross sections for the production of OH−, 1.2, 0.85, and 0.85× 10−21 cm2 molecule−1 for maxima of 6.4, 8.4, and 11.2 eV, suggest that the atoms in the H2O− complex are loosely bound together and behave as essentially independent entities. All of the negative ions from H2O appear to be produced from three different electronic states of the molecule. Results from this study are used to draw a hypothetical potential energy diagram for H2O.
Centrifugal Distortion Analysis of Hypofluorous Acid: HOF and DOF
Authors: Pearson Edwin F. , Kim Hyunyong
Published: February 2004

The millimeter wave rotational spectrum of hypofluorous acid displays sizeable distortion effects. More than forty lines each for both HOF and DOF including a- and b-type transitions have been measured. A semirigid rotor Hamiltonian, which includes the quartic distortion terms, was employed to fit the spectrum. The special constants (in MHz) in the notation of Watson are for HOF: Ã= 585 631.20, B̃= 26 760.31, C̃= 25 510.19, ΔJ= 0.09414, ΔJK= 2.4146, ΔK= 82.52, δJ= 0.00432 and δK= 1.120. For DOF: Ã= 316 096.02, B̃= 25 593.91, C̃= 23 585.28, ΔJ= 0.07903, ΔJK= 1.7349, ΔK= 24.82, δJ= 0.005933 and δK= 1.183. Corrections to Ã, B̃, and C̃ given above have been applied to obtain the effective moments of inertia, and the structure is recalculated.
Critical Slowing Down and Correlation of Concentration Fluctuations of a Macromolecular Solution Very Near Its Critical Mixing Point
Authors: Lee S. P. , Tscharnuter W. , Chu B. , Kuwahara N.
Published: February 2004

The angular and the spectral distribution of scattered light intensity from polystyrene (Mn = 392 000) in cyclohexane were measured at the critical solution concentration very near its critical mixing point in the one phase region. Results show deviations from the critical exponent concept for both static and dynamic thermodynamic properties of critical macromolecular solutions.
Qualitative Theory of the Senftleben Effects
Authors: Coope J. A. R. , Snider R. F.
Published: February 2004

A qualitative description is given of the general properties of the magnetic (and electric) field dependence of the transport coefficients of nonionized gases. This description is based on partial phase randomization which is in turn governed by the ratios of the molecular transition frequencies to ``the'' collision frequency. Applications of this qualitative picture are given to gases in low and high (Paschen-Back) magnetic fields. The viscosity is used throughout to exemplify the theory.
Absorption Spectra of Inequivalent Sites of Tetravalent Np-237 in [(C2H5)4N]2NpCl6
Authors: Menzel E. R. , Gruber J. B. , Ryan J. L.
Published: February 2004

The optical absorption spectrum of single crystal [(C2H5)4N]2NpCl6 has been examined. Between 300 and 77°K the spectrum can be understood in terms of the analysis made recently for Cs2NpCl6 since many aspects of the NpCl6 complex spectrum are similar. At 4°K, however, the spectrum shows evidence for two inequivalent sites of Np4+. The octahedral ground state Γ8 is split by 14 cm−1 in one site and by 16.5 cm−1 in the other site. The reason for occurrence of inequivalent sites in the salt is attributed to Jahn-Teller instability coupled with the presence of the large organic complex cation [(C2H5)4N]+.
Radiation Damage to Peptides: An ENDOR Study of X-Irradiated Acetylglycine
Authors: Box Harold C. , Budzinski Edwin E. , Lilga Kenneth T.
Published: February 2004

ENDOR spectroscopy and isotopic substitution were used in a study of the paramagnetic species produced by x irradiation in single crystals of acetylglycine maintained at 4.2°K. A reduced species was identified which is formed by the addition of an electron to oxygen of the peptide link. Another reduced species, formed by the addition of an electron to the carboxyl group, occurs in two conformations. The oxidized species decomposes losing a proton and CO2.
Anisotropic Transport Processes in Highly Polarizable Fluids. I. Nondeforming Media
Authors: Yun C. K. , Fredrickson A. G.
Published: February 2004

Induced anisotropies in the transport coefficients of highly polarizable fluids are studied. It is predicted that such anisotropy is a linear function of the inverse of either the square of the applied field strength or the size of the apparatus. Comparisons with several experiments on mass diffusion, heat conduction, and electromagnetic polarizations in nematic liquid crystals show good agreement. It is also predicted that a field applied to a very thin sample will have no effect on the transport coefficients of the system unless the field strength is larger than a critical value. Also described is an extrapolation method with which one may obtain the principal as well as the isotropic values of the transport coefficients from experimental data.
Configuration of Fe(CO)4· I2
Authors: Robinette Rosalie , Collins R. L.
Published: February 2004

The 27.8 keV transition of 129I has been studied in Fe(CO)4· I2 by the Mössbauer effect. Isomer shift, e2qQ, and asymmetry parameter η have been determined. Only one species of iodine is observed. From the derived bonding characteristics and the measured η=0.0, it is proposed that iodine bonds as molecular iodine through its px and py orbitals in pseudoeightfold coordination.
Inelastic Scattering of Ne+ by H2 and D2
Authors: Mahan Bruce H. , Winn John S.
Published: February 2004

The reaction Ne+(H2, H)NeH+ is notable as a simple exoergic ion-molecule reaction which has a very small rate constant, less than 8×10−12 cc/sec. We have studied the velocity vector distributions of Ne+ scattered nonreactively from H2 and D2 at a number of energies. There is no evidence for the occurrence of reactive or charge transfer collisions. The small angle (<90°) scattering is elastic, but there is large angle inelastic scattering of three types: vibrational and rotational excitation of hydrogen, collisional dissociation to Ne++H+H, and electronic excitation of hydrogen to B 1Σu+ and perhaps other states. The results are consistent with conclusions drawn from a molecular orbital correlation diagram for the (Ne-H2)+ system.
Evaluation of Liquid Structure Data
Authors: Mountain Raymond D.
Published: February 2004

A procedure for assessing the overall accuracy of liquid structure factor data is examined. The method makes use of the requirement that the two particle correlation function and its derivative vanish for separations smaller than the size of an atom. A series of numerical experiments, designed to evaluate this procedure, are discussed and a calibration of the method based on these experiments is presented. The method is sensitive when the over-all uncertainties in the data are smaller than 1%. Since this is just the level which is now being achieved in liquid structure measurements, the method should be quite useful in the evaluation of liquid structure data. As an illustration, the method is applied to recently published data for liquid neon and liquid gallium.
Simple Procedure for Open Shell SCF Molecular Orbital Computations
Authors: Peters David
Published: February 2004

A simple device for use with open shell SCF computations is proposed. This method eliminates the nonphysical elements in the usual method and leaves a simple operator which is easily computed or approximated.
Infrared Dispersion in Binary Mixtures of Benzene, Carbon Tetrachloride, and Carbon Disulfide
Authors: Zelano A. J. , King W. T.
Published: February 2004

The integrated intensities of the infrared-active fundamental bands of binary mixtures of C6H6, C6D6, CCl4, and CS2 were determined in the 3500–400-cm−1 range, using the dispersion method. It was found that deviations of band intensity in these systems from those predicted from gas-phase measurements are most likely due to ``physical interactions'' which perturb vibrational states rather than due to ``chemical interactions'' which perturb the ground electronic state of the absorbing molecule.
Vibrational Spectrum of Methanetellurol
Authors: Sink C. W. , Harvey A. B.
Published: February 2004

The infrared and Raman spectra of methanetellurol have been investigated with the aid of the isotopic species CH3TeD, CD3TeH, CD3TeD. Spectra of vapor, liquid, and matrix isolated samples are presented. The spectra of the molecule are consistent with the expected Cs symmetry and resemble those of a near symmetric top molecule. Normal coordinate calculations were conducted and results are reported and compared with similar molecules. Unfortunately, repeated attempts to observe the torsional motion in both solid matrix and vapor were unsuccessful.
Absorption Spectra of Nb Atoms Isolated in Rare-Gas Matrices
Authors: Green David W. , Gruen Dieter M.
Published: February 2004

The absorption spectrum of Nb isolated in Ar, Kr, and Xe matrices at 14°K is reported. Observed absorptions in the ultraviolet spectral region correlate well with those expected from known gas phase data. Assignment of all observed absorptions to specific gas phase transitions was not possible in the visible and IR spectral regions. Absorption features observed upon annealing an Ar matrix containing Nb are assigned to the dimer Nb2. The luminescence spectrum of Nb isolated in an Ar matrix is reported.
Equations Governing the Statistical Mechanical Distribution Functions of a Molecular Fluid Interacting with a Solid Boundary
Authors: Chapyak E. J.
Published: February 2004

An infinite set of integrodifferential equations, governing the equilibrium, statistical mechanical distribution functions of a molecular system in contact with a plane, solid wall, is derived. The derivation involves an examination of the effect on the distribution functions produced by an infinitesimal change in the applied external potential. The resulting equations are similar in form to the well-known Bogoliubov-Born-Green-Kirkwood-Yvon equations, specialized to the fluid-wall problem. However, unlike the BBGKY equations, the equations presented here are not restricted by the pair potential condition. The application of these equations to fluid adsorption and to other aspects of liquid state physics is discussed in detail.
Calculation of Atomic Force Constants from Electron Densities
Authors: King W. T.
Published: February 2004

An expression is derived which relates molecular electron densities to the atomic force constants obtained from an analysis of the frequency sum rule for polyatomic molecules. Using approximate electron densities computed by Pople and Segal by the CNDO method [J. A. Pople and G. A. Segal, J. Chem. Phys. 43, S136 (1965)], it was found that not only the magnitudes of the atomic force constants for H, C, N, O, and F atoms were accounted for, but also their observed independence of bond multiplicity.
Low-Frequency Vibrations in Molecular Solids. XVIII. Torsional Modes and Barriers to Internal Rotation of Some Isopropyl Compounds
Authors: Durig J. R. , Player C. M. , Li Y. S. , Bragin J. , Hawley C. W.
Published: February 2004

Far-infrared spectra of solid (CH3)2CHCl, (CD3)2CHCl, (CH3)2CHBr, (CD3)2CDBr, (CH3)2CHI, (CD3)2CHI, (CH3)2CHCN, (CH3)2CHOH, and (CD3)2CDOD have been studied from 33 to 500 cm−1. The A′ and A″ torsional modes have been observed and assigned at 248 and 283, 178 and 208, 256 and 272, 189 and 205, 246 and 253, 190 and 198, 230 and 242, 237 and 277, and 169 and 194 cm−1, respectively, for the above molecules. From these assigned frequencies, the torsional barriers were calculated to be 4.48, 4.54, 4.51, 4.77, 4.11, 4.73, 3.63, 4.18, and 3.94 kcal/mole, respectively. These barrier values are compared to those obtained for some similar compounds and certain trends are noted. Some of the lattice frequencies have been assigned to librational and translational motions on the basis of the isotopic shifts with deuteration.
Thermochemistry of the Molecular Species LiO, LiO+, and Li2O+
Authors: Hildenbrand D. L.
Published: February 2004

Molecular species in the Li–O system were studied by electron-impact mass spectrometry and the data were used to derive the dissociation energy of LiO and the ionization potentials of LiO and Li2O. From studies of the gaseous equilibria Li+O2=LiO+O and Li2O+O=2LiO and from the composition of saturated vapor over Li2O(c), the value D00(LiO)=80.5 ± 1.5 kcal (3.49 ± 0.06 eV) is obtained. The ionization potentials were found to be I.P.(LiO) =8.45 eV and I.P.(Li2O)=6.19 eV with an uncertainty of 0.20 eV, leading to Δ Hf0o(LiO+)=211.5 kcal/mole (9.17 eV) and Δ Hf0o(Li2O+)=103.1 kcal/mole (4.47 eV). The data are compared with the results of some theoretical calculations, and the chemical bonding in these molecules is discussed briefly.
ESR Study of Radicals in γ-Irradiated Polycrystalline AsF3 and AsCl3
Authors: Subramanian S. , Rogers Max T.
Published: February 2004

The free radicals produced in frozen, polycrystalline AsF3 and AsCl3 by γ irradiation have been characterized by ESR and shown to be AsF3− and, most probably, AsCl3−. Hyperfine interactions with arsenic are observed in each case and in AsF3−, ligand hyperfine splittings by three fluorine atoms, two of one kind and one of another, are also seen. The ESR parameters are consistent with an approximately planar-T configuration for AsF3− with the odd electron largely in an orbital perpendicular to the plane.
Square-Well Potential. III. Transport Properties of Liquids
Authors: Schrodt I. B. , Ku J. S. , Luks K. D.
Published: February 2004

The Davis-Rice-Sengers square-well theory of transport for simple dense gases and liquids is tested with Yvon-Born-Green theoretical pair correlation functions for σ2/σ1=1.85. Comparison with experiment shows that the theory correctly predicts the qualitative features of liquid argon transport properties and quantitatively is very good at high temperatures and densities in the liquid region. An adjustment of intermolecular potential parameters is shown to improve the predictions of the theory uniformly. Some comments are made concerning the success of this theory in light of recent studies of the Rice-Allnatt theory.
He-D
2
Total Scattering Cross Sections in the Velocity Range 760–2600 m/sec
Authors: Lilenfeld Harvey V. , Kinsey James L. , Lang Neil C. , Parks Eric K.
Published: February 2004

Measurements of the total scattering cross section Q for He-D2 are reported over a range 760 m/sec≤ vr≤2600 m/sec in the relative speed. The data have been fit with a piecewise continuous potential that also gives a good fit to the diffusion coefficients, has the theoretical C6 coefficient, and joins smoothly with the short range a priori computed potential.
Unified Theory of Orientational Relaxation
Authors: Kivelson Daniel , Keyes Thomas
Published: February 2004

A mathematically simple model for orientational relaxation in liquids is presented. This theory, expressed in terms of Mori's formalism for generalized hydrodynamics, is developed with three orientational variables interrelated by three coupled linear transport equations. The three variables are D,dD/dt, and d2D/dt2, where D is a relevant Wigner rotational transformation function. In appropriate limits the theory reduces to that for rotational diffusion, gas-like extended rotational diffusion (GLED) and solid-like oscillatory rotations (SLOR) or cell model motions. This theory, which we call the pseudo-GLED-SLOR theory, therefore gives a unified picture, encompassing all limits, of molecular rotations in liquids. The assumptions, and consequently the results, differ slightly from those usually introduced in the GLED and SLOR theories; the various limiting forms of molecular reorientation are obtained in the present theory via restrictions on the quantities, D,dD/dt, d2D/dt2, and d3D/dt3, whereas the usual quantities of interest are D, the molecular angular velocity, the intermolecular torques, and the rate of change of torques. It is for this reason that we have introduced the term ``pseudo'' in describing the theory. The only restriction that must be placed on the theory is that d3D/dt3 changes impulsively, but of course, different assumptions concerning the magnitudes of the other variables lead to different limiting physical situations. In appropriate limits, the present theory exhibits most of the interesting features of the rotational diffusion theory, Gordon's extended rotational diffusion theory, Steele's inertial effects and Ivanov's jump theory; furthermore, it predicts rotational or torsional side bands in the frequency spectrum of the molecular orientational autocorrelation function. In the far wings it predicts an ω−6 frequency dependence. The theory treats D,dD/dt, and d2D/dt2 as dynamical quantities and only d3D/dt3 is treated as a Markoffian variable. A careful analysis is presented of the differences between the correlation time τθ= ∫ 0∞ 〈DD(t)〉 dt〈DD〉−1,where 〈DD(t)〉 is the autocorrelation function of D, and the spectral half-width Δ ω1/2.
ΔmS=±1, ΔmI=0, ±1, ±2 Transitions in the Paramagnetic Resonance Spectrum of Mn(pic)2 · 2H2O:Zn(pic)2 · 4 H2O
Authors: Stoller H. J. , Rist G. , Günthard Hs. H.
Published: February 2004

ESR spectra of manganese picolinate substituted in zinc picolinate tetrahydrate single crystals are presented. Two magnetically nonequivalent sites are found to be occupied in this matrix. Highly resolved hyperfine line groups were found in the spectra, which nearly completely exhibit the full pattern of transitions with ΔmS=±1, ΔmI=0, ±1, ±2. The spectra may be analyzed to a high degree of approximation by a spin Hamiltonian containing 8 magnetic constants for the Mn picolinate molecules. For satisfactory interpretation third order perturbation theory was found unsatisfactory but high accuracy may be achieved by exact diagonalization.
Vibrational Spectra and Structure of 3-Methyl-1,2-Butadiene
Authors: Harris W. C. , Longshore C. T.
Published: February 2004

The infrared and Raman spectra of gaseous and crystalline 3-methyl-1,2-butadiene have been recorded from 140 to 4000 cm−1. All spectra have been interpreted in detail, and the fundamentals have been assigned on the basis of depolarization ratios, vapor-phase band contours, relative band intensities, and group frequency correlations. The interesting a2 and b2 methyl torsional vibrations are assigned to bands at 185 and 236 cm−1, respectively, in the spectrum recorded at liquid nitrogen temperatures. From these frequencies the magnitude of the internal rotational barrier is estimated to be 2.7 kcal/mole. The barrier height and the observed top-top frequency splitting is discussed in conjunction with recent studies on similar molecules.
Random Matrix Theory and the Master Equation for Finite Systems
Authors: Gelbart William M. , Rice Stuart A. , Freed Karl F.
Published: February 2004

In this paper we consider the justification for the use of a stationary Markov assumption to describe vibrational relaxation and dissociation in isolated, highly excited, polyatomic molecules. We discuss first a model in which only a single oscillator is allowed to break, the remaining vibrations serving as a heat bath which interacts weakly with the reactive degree of freedom. A random matrix hypothesis is used to derive a time-independent form for the rates of internal energy exchange. In the limit of very ``hot'' molecules these transition probabilities are shown to have the expected linear and quadratic dependences on the individual vibrational quantum numbers. The constants of proportionality are simple functions of the size of the molecule and the interaction strengths coupling the nuclear motions. Finally, we return to the full dynamical theory of unimolecular reactions which was introduced in an earlier paper [J. Chem. Phys. 52, 5718 (1970)] as an alternative to the conventional statistical (e.g., transition-state) approaches. We use the Zwanzig projection operator formalism to derive the sufficient conditions for which Liouville's equation for internal energy exchange assumes the Markov form appropriate to an irreversible relaxation process. The familiar Green's function (resolvent operator) techniques are generalized to the case of tetradic propagators and a stochastic description is shown to be justified for time scales which correspond to experimental observation of the vibrational dissociation.
Initial Ionization Yield and Scavengable Electron Yield in Liquid Hydrocarbons
Authors: Ko H. W. , Mozumder A.
Published: February 2004

A self-consistent procedure has been described for calculating the W value for initial ionization. It utilized yields for energy deposition and a prescribed rule of correspondence between energy deposition and average number of ionizations created in an event. A value of 21.5 eV has been obtained for W in hydrocarbons using Mozumder and Magee's distribution for energy deposition. It is postulated that a certain fraction of ionized electrons will be neutralized before thermalization occurs resulting in a nontrivial difference between initial ionization yield and scavengable electron yield. A superposition model has been proposed to calculate the unscavengable part of the ionization yield. Present computations give G values (100 eV yield) for initial ionization and scavengable electrons as 4.65 and 4.10, respectively.
On the Formation of Very Thin Oxide Films on Metals: Contact Potential Measurements During the Oxidation of Different Crystallographic Faces of Copper
Authors: Boggio Joseph E.
Published: February 2004

The low temperature oxidation of copper is treated in terms of a model in which the surface reaction involving the formation of copper ion vacancies at the gas-oxide interface is rate controlling. The predictions of the model are compared with experimental observations of the change in contact potential difference when clean (100), (110), and (111) copper surfaces are oxidized at room temperature. A value of 0.75±0.03 eV for the activation energy for formation of a copper ion vacancy is derived from the process of fitting experiment to theory. The interpretation of the observed changes in contact potential difference is made in terms of surface states located at the metal-oxide interface and at the gas-oxide interface. A reaction rate anisotropy that is in agreement with the observations of Young, Cathcart, and Gwathmey follows naturally from the model.
Total Cross Sections for Formation of Ions from CsBr by Collision with Ar, Xe, and NaBr(Ar)
Authors: Piper L. G. , Hellemans L. , Sloan J. , Ross J.
Published: February 2004

Measurements have been made by cross beam techniques on the absolute total cross section Q for formation of ions from CsBr in collisions with Ar and Xe, and relative total cross section for NaBr with Ar, in a range of relative kinetic energies (Xe: 12–120 eV; Ar: 20–125 eV). The absolute cross sections obtained for CsBr, with estimates of accuracy, are 5.0±1.2 Å2 for Ar and 12.6±2.7 Å2 for Xe at a relative kinetic energy of 46 eV. The energy dependence of the cross sections follows closely that predicted by the simple reaction model of hard spheres. A fit of this model to the measurements leads to estimates of threshold energies. Measurements have also been made on a crude energy analysis of the ions formed. About half the ions of either sign have laboratory energies below 5 eV and the remainder is distributed continuously over larger energies up to the maximum. Negative ions have somewhat lower energies than positive ones. The results are consistent with a knockout model of collisional dissociation to ions, with a preference for dissociation by collision of the rare gas atom with the heavy (positive) end of the molecule.
ESR Evidence for Proton Tunneling from a Positive Hole through Intermolecular Hydrogen Bond in Irradiated Single Crystals of Carboxylic Acids
Authors: Minakata Kayoko , Iwasaki Machio
Published: February 2004

It has been found that an irradiated single crystal of potassium hydrogen fumarate-d2 (K+−OOC–CD=CD–COOH) gives two kinds of carboxyl radical, OOC–CD=CD–COO−· [Oσ(I)] and · OOC–CD=CD–COOH[Oσ(II)]. Evidence has been obtained for Oσ(I) being formed from the positive hole at the COOH end by proton tunneling to the neighboring COO− group through the intermolecular hydrogen bond. The dipolar tensor calculated for the transferred proton agrees well with the observed tensor in both the principal values and directions. Oσ(II) formed by loss of an electron from the COO− group gives the hyperfine coupling to the proton which belongs to the neighboring COOH group. Agreement between the observed and calculated dipolar tensors is also fairly good.
Field Induced Perturbations in the Ultraviolet Spectrum of HCP
Authors: Moehlmann Jon G. , Hartford A. , Lombardi John R.
Published: February 2004

Both electric and magnetic field induced perturbations are observed and analyzed for several excited states of HCP. An electric field causes the R(13) line of the Δ13←1Σ+ transition (0010← 0000) to shift nonlinearly. This is interpretted as due to a nearby electronic state with a nonzero transition moment of 0.11±0.02 D with the 3Δ1 state, and the zero-field energy level separation of the rotational sublevel of the two states is 0.04±0.01 cm−1. In the limit that the 3Δ1 state is case (a), it can be shown that Ω must be either 0 or 2 for the perturbing state. In the 0200← 0110 band of the Ã 1A″← X 1Σ+ transition we observe magnetic field induced deperturbations in the J=8 and 13 levels, which are perturbed in zero field. The zero-field energy separation of the two levels is 0.092±0.005 cm−1 and 0.009±0.005 cm−1, the off-diagonal matrix elements connecting the levels with a perturbing state in zero field are 0.106±0.005 cm−1 and 0.148±0.005 cm−1, respectively. It is also determined that the effective magnetic moment of the perturbing state is 0.68±0.15 and 1.25±0.20 μB for J=8 and 13, respectively. This combined with other evidence indicates that the perturbing state is of 3Σ+ vibronic symmetry with a B value of 0.40±0.02 cm−1 and with splitting constant λ=4.0±1.0 cm−1.
Analysis of Macromolecular Polydispersity in Intensity Correlation Spectroscopy: The Method of Cumulants
Authors: Koppel Dennis E.
Published: February 2004

The first order electric field correlation function of laser light scattered by polydisperse solutions of macromolecules can be written as a sum or distribution of exponentials, with decay rates proportional to the diffusion coefficients of the solute molecules. It is shown that the logarithm of this correlation function is formally equivalent to a cumulant generating function. A method is described by which the distribution function of the decay rates (and thus the extent of polydispersity) can be characterized, in a light scattering experiment, by calculation of the moments or cumulants. The systematic and random statistical errors in the calculated cumulants are discussed.
Dynamic Susceptibility of a Model Polymer in Several Limits-Theory and Calculations
Authors: Mandell M. J.
Published: February 2004

We study the susceptibility of a model polymer having rotating dipolar sidechains with nearest neighbor interactions and diagonal visocosity. The susceptibility can be found exactly (1) at zero frequency for arbitrary interaction strength, and (2) at zero interaction strength for arbitrary frequency and viscosity. In addition, a high-temperature expansion exists for arbitrary frequency both in the viscous limit and for finite viscosity. We also study the time-dependent correlation function 〈 cosφi(t) cosφi+1(0)〉 for arbitrary viscosity and weak interaction, and the possibility of a more complex diagonal friction law. In no case are we able to produce a Cole-Cole plot which approaches the origin with finite slope at high frequencies, as does much experimental data.
Study of the Electronic Structure of Molecules. XVII. Analysis of the Formation of the Acetylene, Ethylene, and Ethane Molecules in the Hartree-Fock Model
Authors: Clementi Enrico , Popkie Herbert
Published: February 2004

The electronic density and energy of the C2H2, C2H4, and C2H6 molecules are computed in the Hartree-Fock approximation and the results compared. Each molecule is computed at three different carbon-carbon internuclear distances, namely, those experimentally known for the equilibrium geometry in C2H2, C2H4, and C2H6. The comparison is extended by reporting computations on the lowest singlet state of the C2 molecule. The analysis is performed by making use of Mulliken's electron population analysis and our technique for partitioning the energy (bond energy analysis). For C2H4 we have also considered the twisted configuration (where one CH2 group is perpendicular to the other) and for C2H6 we have considered both staggered and eclipsed configurations (and therefore, we are in a position to add a few comments on the barrier to internal rotation). The basis set is sufficiently large and extended so as to be near to the Hartree-Fock limit for all the computations reported. The binding energy computed in the Hartree-Fock approximation has been corrected for the correlation error making use of Wigner's formula relating the electronic density to the correlation energy. It is shown that the one-center energies, the molecular orbital valence state (MOVS) energies, are regular functions of the 2s and 2p population at the C atom, complementing previous work where it was shown that the MOVS energies are functions of the gross atomic charges. Also, it has been shown that the two-center energy terms are proportional to bond strengths traditionally used in the chemical literature. The difficulty of analyzing small energy differences in the barrier to the internal rotation of C2H6 has been removed by analyzing the barrier at smaller R(C–C) distances where the barrier is considerably larger. It has been proposed that the observed (or computed) small barrier is the result of internal charge transfer and conjugation between the pseudo-2p orbitals on H3 and the 2p orbitals on C.
Energy Levels of Er3+ in Three Rare Earth Hydroxides
Authors: Cone R. L.
Published: February 2004

Energy levels of Er3+ in three compounds: Er(OH)3, 1% Er3+:Y(OH)3, and 1% Er3+:Tb(OH)3 have been determined from optical absorption experiments on single crystals at 77 and 1.3°K and from far infrared absorption experiments at 1.3°K. For each material, the four crystal field parameters which specify the crystal field for f electrons at a site of C3h symmetry were found by a least squares analysis including intermediate coupling and the J-mixing effects of the crystal field. The results for Er(OH)3 are typical: the 37 measured levels were fitted with a mean deviation of 3.2 cm−1 with the best parameters being: B20=192 cm−1, B40=−64 cm−1, B60=−40 cm−1, and B66=521 cm−1. The parallel Zeeman effect of the Er3+ energy levels was also studied in fields up to 38 kilogauss for two of the compounds, Er3+:Y(OH)3 and Er3+:Tb(OH)3, and good agreement was found between the calculated and observed splitting factors and with the results for Er3+:Y(OH)3 from previous electron spin resonance experiments. The spontaneous splittings of the Er3+ doublet levels in ferromagnetically ordered Tb(OH)3 have also been determined, and analysis of these splittings has indicated the presence of nondipolar interactions between the Er3+ and Tb3+ ions.
Structure of (KSO3)2NO in X-Irradiated Single Crystals of (KSO3)2NOH
Authors: Hamrick Phillip J. , Shields Howard , Gangwer Thomas
Published: February 2004

The nitrosyldisulfonate ion has been identified in x-irradiated single crystals of potassium hydroxylaminedisulfonate. Principal values of the N14 hyperfine coupling constants are 27.5, 7.7, and 5.5 G. The principal g values are 2.0094, 2.0055, and 2.0026. Weak transitions due to hyperfine interactions with a proton from the host crystal are observed.