bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Magnetic Resonance Spectrum of NO2 at 337 μm and 311 μm
Authors: Curl R. F. , Evenson K. M. , Wells J. S.
Published: February 2004

The Zeeman components of several rotational transitions of nitrogen dioxide have been observed in absorption using the 311 and 337 μm lines of an HCN laser as a source. The Zeeman components of four rotational transitions (two at 311 μm and two at 337 μm) have been assigned. Two components of the g tensor have been determined from the spectrum by least square fitting. The anisotropic component (aa)g(S), obtained as −0.010, agrees well with that predicted from theory, but the isotropic component (0)g(S), obtained as 2.013, does not agree satisfactorily with theoretical prediction or with solid phase measurements both of which give 1.9997. The rotational frequencies of the four transitions have also been obtained.
Van Vleck Perturbation Theory Applied to Vibration-Rotation Interaction in Tetrahedral Molecules
Authors: Susskind Joel
Published: February 2004

Vibration-rotation interaction in tetrahedral XY4 molecules is discussed with particular emphasis on the resultant effective vibration-rotation Hamiltonian in the ground and the first excited states of the F2 vibrations in these molecules. It is shown that to second order in perturbation theory, the coefficients of effective tensor operators in ν3 and ν4 of the form T044, T134, T224, T244, T246, and possibly T234, T144, and T22401 are expected to get contributions of comparable magnitude from a first order off-diagonal vibration-rotation operator in the Hamiltonian.
Scavenging Kinetics of Electrons Produced by Irradiation of Organic Glasses; Experimental Evidence for Long Range Tunneling
Authors: Miller John R.
Published: February 2004

This paper reports new experimental results on the influence of scavengers on the yields of trapped electrons in γ-irradiated organic glasses, which show that: (1) Trapped electron yields observed minutes after irradiation decrease exponentially with scavenger concentration; (2) transfer of trapped electrons to scavengers continues after irradiation, even in rigid matrices where no trapped electron decay occurs in the absence of scavengers; (3) the presence of a scavenger of low electron affinity can increase the yield of the anion of a scavenger of high electron affinity, although a large decrease would be expected if the scavengers competed for mobile electrons; (4) the ``electron capture cross sections'' of scavengers are often strongly dependent on what species the scavengers compete with for electrons, apparently indicating that the ``electron capture cross section'' is not an appropriate concept. These results and several others are consistent with a model involving tunneling of trapped electrons, but seem to be inconsistent with any model based on capture of electrons prior to their localization in traps.
Study of the A → X Transitions in N2+ and CO+
Authors: Holland Redus F. , Maier William B.
Published: February 2004

Optical emissions from long-lived, excited states of CO+ and N2+ in ion beams have been studied. CO or N2 is ionized by electron impact, and the ions are removed from the ion source to the observation region. Spectra of emission from CO+ and N2+ are obtained for wavelengths in the ranges 3200–5200 Å and 6000–8700 Å, respectively. All of the spectral features can be ascribed to the CO+ comet-tail and N2+ Meinel emission systems. The electronic transition moments, R̄e, for these two emission systems are determined and are found to vary rather slowly with wavelength over the wavelength ranges for which we have data. Lifetimes of the v′=1, 2, 4, and 6 vibrational levels of CO+ (A 2π) are found to be 3.49, 2.78, 2.63, and 2.41 μsec, respectively. Lifetimes of the v′=2, 3, 4, and 5 vibrational levels of N2+(Aπu2) are found to be 12.28, 10.70, 10.08, and 9.14 μsec, respectively. The dependences of the measured lifetimes on v′ are consistent with the experimental values of Re and with available Franck-Condon factors. Relative cross sections for excitation of various emission bands have been derived from the spectra and lifetimes presented in this report; these cross sections agree fairly well with theory and with previous measurements. The A states of CO+ and N2+ appear to constitute about 46% and 30%, respectively, of the ions produced by 46.5-eV electrons impinging on CO and N2. The electron energy dependences of the light output in the (2, 0) Meinel band and in the (3, 0) and (4, 0) comet-tail bands have been measured from threshold to 200 eV. From our data and total ionization cross sections we obtain maximum cross sections for excitation of the (2, 0) Meinel and the (3, 0) comet-tail bands of 0.073 and 0.133 Å2, respectively.
Single Crystal and Powder EPR Studies on Copper(II) Bis(di-n-butyldiselenocarbamate)
Authors: Kirmse Reinhard , Wartewig Siegfried , Windsch Wolfgang , Hoyer Eberhard
Published: February 2004

Copper(II) bis(di-n-butyldiselenocarbamate) is studied in single crystals, diamagnetically diluted by Ni(II) bis(di-n-butyldiselenocarbamate), in polycrystalline samples and in frozen solutions by means of EPR. The EPR spectra show that in the unit cell two magnetic nonequivalent Cu(dbsc)2 molecules are to be found and that 77Se ligand hyperfine splitting can be detected. The principal axes of the g and the copper-hfs tensor do not coincide. A spin Hamiltonian for this case is given. Contrary to the copper-hfs and the 77Se-hfs tensors, which were found to be in agreement with what is expected for a planar complex of approximately D2h symmetry, the behavior of the g tensor is significantly different with respect to analogous CuS4 compounds. This indicates that the electronic structure of the complex differs remarkably from the structure of planar Cu(II) complexes; consequently, the symmetry is C2h. The Se-hfs data were used to estimate the degree of covalency in the Cu–Se σ bond. This was compared with parameters for some analogous sulfur complexes. In the spectra of the polycrystalline samples the anomaly in the behavior of the tensors is obviously in accord with the single crystal EPR results.
Fluorescence Excitation and Photodecomposition of the First Excited Singlet Cyclobutanone (1A2): A Study of Predissociation of and Collisional Energy Transfer from the Vibronically Selected Species
Authors: Hemminger John C. , Lee Edward K. C.
Published: February 2004

Fluorescence emission quantum yields (ΦF) from the first excited singlet state of cyclobutanone (CB) in the gas phase have been measured in the exciting wavelength (λex) range of 3050–3350 Å at ∼0.5 Å resolution. The value of ΦF at 5 torr is ∼0.002 above λex=3190 Å, but it suffers a sharp decline below this wavelength because of the onset of molecular predissociation, e.g., ΦF<4×10−6 for λex<3100 Å. Fluorescence stabilization phenomena are studied by addition of C3H8 up to 2200 torr. A simple kinetic treatment of the data provides (i) the estimated singlet lifetime value (τs) of 10−9−10−12 sec below λex=3140 Å; and (ii) the collision efficiency value of ∼0.5 for the upward transition as well as for the downward transition (of vibrational energy transfer). The primary photochemical transformation mechanism for the CB(S1*) is discussed in light of the new estimated lifetime information.
Effusion-Mass Spectrometric Determination of the Heats of Formation of the Gaseous Molecules V4O10, V4O8, VO2, and VO
Authors: Farber Milton , Manuel Uy O. , Srivastava R. D.
Published: February 2004

An effusion-mass spectrometric investigation of the vapor in equilibrium with the vanadium compounds, V2O5, V2O4, and V2O3, was conducted. The only congruently evaporating solid was V2O3, while the others decomposed to various vapors and V2O3 in the temperature range 1000–1200°K. The vapor over V2O5 was found to contain the compounds V4O10(g) and V4O8(g) with resulting ΔHf298 values of −681.2±7 kcal/mole and −590.5±7 kcal/mole, respectively. A study showed that the vapor over V2O3 at 2270°K contained the species V(g), VO(g), and VO2(g), yielding values for ΔHf298 of 35.1±4 kcal/mole and −56.3±4 kcal/mole for VO(g) and VO2(g), respectively.
Mixed Adsorption of D2 and C2H4 on Polycrystalline Tungsten
Authors: Cartier P. G. , Rye R. R.
Published: February 2004

The adsorption and reaction of hydrogen and ethylene on polycrystalline tungsten were studied by means of flash filament spectroscopy. For an ethylene exposure just sufficient to form a monolayer on a bare surface, a D2 covered surface adsorbs 12 monolayer of ethylene without loss of D2; for the inverse process, preadsorption of C2H4, no D2 is adsorbed. In flash filament spectra taken subsequent to a dose of hydrogen followed by ethylene, the major gas phase products are hydrogen and small quantities of ethane. The hydrogen spectra contain peaks at 300°K (ethylene decomposition), 450°K (both ethylene decomposition and hydrogen desorption), and 650°K (hydrogen desorption) with H2 predominant in the 300° peak and D2 predominant in the high temperature peaks. Since coverage studies show that ethylene decomposition occurs via transfer of hydrogen to the surface where H2 and D2 are known to equilibrate, this concentration of isotopes in specific peaks indicates that C2H4 adsorption does not occur uniformly over the D2-covered surface. These results are interpreted in terms of a surface composed of two regions: region A where D2 and C2H4 coadsorb on independent sites, and region B where D2 and C2H4 occupy the same sites. Arguments are presented for associating W(100) with region A and W(110) with region B. The production of ethane during the flash is consistent with a Langmuir-Hinshelwood mechanism with migration of hydrogen as the rate limiting step.
Application of the Semicontinuum Model to the Effect of Dipole Reorientation on Trapped Electron Spectra in Glassy Ethanol
Authors: Fueki Kenji , Feng Da Fei , Kevan Larry
Published: February 2004

A semicontinuum model is applied to trapped electrons in glassy ethanol at 77°K. The configurational stability of the ground state has been established. Ground, excited, and continuum states are calculated self-consistently for specific orientations from 80° to 0° of the molecular dipoles with respect to the trapped electron. It is shown that the spectral shifts observed for trapped electrons in pulse radiolysis experiments on alcohol glasses and the shifts observed upon warming from 4 to 77°K after γ irradiation at 4°K can be semiquantitatively accounted for by the molecular dipole orientation mechanism. The cavity radius of the trapped electron also increases somewhat upon dipole orientation but this is a small effect. The effect of dipole orientation upon other physical properties of the trapped electrons in ethanol is also discussed.
Polarizability Anisotropy of Hydrogen Fluoride
Authors: Muenter J. S.
Published: February 2004

The hyperfine spectra for the J=1 and 2 states of hydrogen fluoride have been observed by molecular beam electric resonance spectroscopy. The observed Stark coefficients are corrected for centrifugal distortion and yield a value for the polarizability anisotropy, α=0.220 ± 0.020 Å3. Differences in the values for the spin-rotation interactions are observed for the two rotational states and these are used to calculate dCF/dR=(1.66± 0.10)× 103 kHz/Å and dCH/dR=(2.5± 1.4)× 102 kHz/Å.
Collision Induced Far Infrared Absorption of Solutions of CH4 and CD4 in Liquid Argon
Authors: Marabella Leonard , Ewing George E.
Published: February 2004

The far infrared spectra of CH4 and CD4 dissolved in liquid argon were recorded to probe the dynamics of this liquid state system. Broad bands devoid of any fine structure were observed. Methane does not possess a permanent dipole moment and the observed absorption results from a dipole induced by the octopolar field of the molecule during a collision. For octopole induced rotational transitions the selection rules are ΔJ=0–3. Assuming free rotor energy levels and line strength factors, and a modified Lorentzian band shape, synthetic spectra were generated which agree quite well with the experimental data. The integrated absorption coefficient is much smaller than that predicted for binary collisions. This is expected since binary interactions in the liquid state cannot be isolated from higher order interactions with neighboring atoms. The dipole moment induced during a collision is partially cancelled by many-body interactions so the absorption coefficient in the liquid state is diminished, compared to the low density gas. Time correlation functions were determined from the far infrared data as well as from near infrared and Raman spectra of methane and compared. The quantum mechanical free rotor time correlation functions were calculated and found to agree with the experimental results for times shorter than liquid state collision times. Since the far infrared correlation function is due to an induced dipole moment, it is damped accordingly. We estimate that the duration of collision is ≈ 2 × 10−13sec. The good agreement of the synthetic spectra and free rotor correlation functions with experiment indicate a barrier to rotation that is comparable to the magnitude of rotational energies observed. Hindered rotation in liquids is also discussed in terms of collisional effects.
Nuclear Quadrupole Resonance of Some Four-Coordinated Nitrogen Compounds
Authors: Marino R. A. , Oja Tõnis
Published: February 2004

Nitrogen-14 nuclear quadrupole resonance spectra have been obtained from several substituted ammonium ions. The data are interpreted in terms of the electronegativity of the substituents, and a relative scale for H, CH3, NH2, NH3+, and OH is obtained. The enhanced proton-nitrogen spin-spin coupling was utilized to match unequivocally the v+ and v− spectral lines for each nitrogen-14 site.
Reduced Partitioning Procedure in Configuration Interaction Studies. I. Ground States
Authors: Bartlett Rodney J. , Brändas Erkki J.
Published: February 2004

A variation-perturbation approach to configuration interaction (CI) studies of atoms and molecules has been derived which yields a series of converging upper bounds to the CI energy. As a consequence, the method permits an adequate representation of a large n-particle wavefunction in terms of a very low order nonlinear perturbation summation. This ``reduction'' procedure is found to have simplifications for full CI studies as well as suggesting certain systematic improvements over the standard Hartree-Fock (HF) and ``truncated'' CI calculations. The first order solution, which is equivalent to the application of a geometric sumrule to the perturbation expansion is also shown to be derivable from a ``steepest descent'' argument. In preliminary calculations on H2 and the HeH+ molecular ion with a HF function as the unperturbed state, the first order result gives 60% to 70% of the energy difference between the full CI energy and the HF value, while only a third order treatment accounts for better than 90%. Potential curves for the ground state of HeH+ for the eight lowest orders of solution and their spectroscopic parameters are also obtained, with the eighth order energies differing from the full CI values by less than 10−4 a.u. at all internuclear separations.
Comparison of Two Theories for the Two Particle Distribution Function of Polar Fluids
Authors: Nienhuis Gerard , Deutch J. M.
Published: February 2004

Two recent theories for the two particle distribution function of polar fluids are compared. The formal theory of Nienhuis and Deutch [J. Chem. Phys. 55, 4213 (1971)] is valid for arbitrary sample geometry and arbitrary short-range forces accompanying the dipole-dipole interactions. The theory of M. S. Wertheim [J. Chem. Phys. 55, 4291 (1971)] presents an exact result for the mean spherical model (MSM) of a fluid of hard spheres with embedded dipole moment in an infinite system and in a finite spherical system. Perfect agreement is found when the approximations of the MSM are introduced into the Nienhuis-Deutch theory. This lends strong support to the conclusions that have been drawn about the long-range and shape dependent nature of the two particle distribution function for polar systems. Finally an expression is given for the excess free energy of a dipolar fluid in the MSM.
Vibrational Spectra of Vapor-Deposited Binary Borosilicate Glasses
Authors: Tenney A. S. , Wong J.
Published: February 2004

Room temperature infrared absorption spectra in the range 4000–250 cm−1 of binary borosilicate thin glass films deposited by reacting argon-diluted SiH4–B2H6–O2 mixtures on heated silicon substrates at 300–400°C have been obtained throughout the composition range. Spectra of the end components are found to be in good agreement with those of vitreous SiO2 and B2O3 prepared from the liquid state. The band shapes, intensities, and frequencies of maximum absorption of the B–O stretching mode and the Si–O stretching mode have been studied as a function of composition. At constant composition the shape of the former band is found to be dependent on the substrate temperature during deposition. Insight into the ``mixing'' nature of these vapor-deposited glassy solids has been obtained from an analysis of the spectral distribution of Si–O–Si, B–O–B, and B–O–Si bonds as a function of composition. A new band at 670 cm−1 not previously reported in literature, has tentatively been assigned to a bond bending mode of the B–O–Si centers in the borosilicate structure.
Viscosity-Dependent Rate of Ion Recombination Following Pulse Irradiation
Authors: Sawai Takeshi , Hamill William H.
Published: February 2004

Triphenylamine (TPA) in alkane radiolytic systems traps both electrons and holes. The recombination fluorescence of TPA+-TPA− geminate pairs decays exponentially, and the half-life tr depends empirically upon (viscosity)1/2. This dependence applies equally for squalane as solvent over a range of temperature and for isothermal variation of viscosity in mixtures of squalane and 3-methylpentane. The relation tr ∝ η1/2 is attributed to a Boltzmann dependence of ion jumps along field lines with mean free path λ. The mean free path is described in terms of the Cohen and Turnbull free-volume model. The probability of a redistribution of free volume vf for a critical v* (and λ*) is P(v*)=exp(-γ v* / vf), with γ ≅ 1. Defining λ=λ* P (v*) the motion of the correlated ion pair is given by dR=[1 - exp( -e2λ / ε R2kT)]udt, where u is thermal kinetic velocity and 2R is the separation of the ion pair.
Intramolecular Contributions to the Entropy and Energy of Fusion of Polyethyleneoxalate and Polyethylenesuccinate
Authors: Tonelli Alan E.
Published: February 2004

The intramolecular or conformational contribution to the entropy and energy of fusion of polyethyleneoxalate (PEO) and polyethylenesuccinate (PES) are calculated in the rotational isomeric state approximation. Both aliphatic polyesters are found to have conformational entropies equal to or in excess of those measured and calculated for the lower melting homologs polyethyleneadipate, polyethylenesuberate, and polyethylenesebacate. Consequently, it is concluded that PEO and PES melt at substantially higher temperatures than the higher members of the homologous series of polyesters [–O–(CH2)x–O–CO–(CH2)y–CO–]h, primarily because of larger enthalpies of fusion. Furthermore, it is shown that the major contribution to the increased enthalpies of fusion for PEO and PES can be attributed to their possession of crystalline conformations of lower intramolecular or conformational energy.
Property-Optimized Gaussian Atomic Orbitals
Authors: Page Gerald , Ludwig Oliver G.
Published: February 2004

Property-optimized Gaussian expansions of 1s-, 2s-, and 2p-Slater-type orbitals are obtained by weighting the usual fittings with r−2, r−1, r and r2. Pseudonormalized expectation values of r−2, r−1, r, r2, and −12 ∇2 calculated with the very small-term expansions are of exceptional quality by comparison with the values calculated with unweighted expansions.
Liquid Water: Atom Pair Correlation Functions from Neutron and X-Ray Diffraction
Authors: Narten A. H.
Published: February 2004

Neutron diffraction data for heavy water at 25°C, together with results derived from x-ray scattering, show that the orientational correlation between pairs of molecules is of a much shorter range (<5Å) than the positional correlation between molecular centers (<8 Å). The neutron diffraction pattern is completely described by a model which assumes preferred average orientation between neighboring molecules and no orientational correlation between second and higher neighbors. The structure of an average D2O molecule in the liquid is not significantly different from that of an isolated molecule in the dilute gas. Atom pair correlation functions derived from the data and the model are in good qualitative agreement with results derived from molecular dynamics studies.
Spectra and Structure of Small Ring Compounds. XXIV. Microwave Spectrum of 2,3-Dihydrofuran
Authors: Durig J. R. , Li Y. S. , Tong C. K.
Published: February 2004

The microwave spectrum of 2,3-dihydrofuran has been recorded from 12.4 to 40.0 GHz. Only A-type transitions were measured. Both Q-branch and R-branch assignments have been made for the ground and first five vibrationally excited states of the ring-puckering mode. From a consideration of the rotational constants for the ground and excited states and the comparative intensities of lines in the vibrationally excited states of the ring puckering mode with similarly assigned lines in the ground state, it is concluded that the potential function for this out-of-plane skeletal bending mode has a double minimum with a low barrier (around 83 cm−1). In the ground states the expectation value for the dihedral angle is consistent with the 19° previously reported. The total dipole moment was determined to be 1.32± 0.02 D for the ground state and the following components were obtained: μa=1.30± 0.02, μb=0.25± 0.02, μc= 0.00± 0.01 D. The dipole moments for the first three excited states of the ring-puckering mode was also determined and only the μb component was outside the experimental error of that found for the ground state.
Termolecular Association Reactions of Mg, Ca, and Ba Ions
Authors: Spears K. G. , Fehsenfeld F. C.
Published: February 2004

We have measured termolecular association rate constants of Mg++, Ca++, and Ba++ with a variety of neutrals (Ar, O2, N2, CO, CO2, N2O, and H2O). Most neutrals associated to form all species M++·(X)n, where n=1, ···, 6. The association rate constants of double ions are 100–500 times larger than those of single ions. There are smooth changes in rate constants for any neutral as a function of ionic radius, and a definite ordering exists between neutrals. We can understand the general features of such data and some unusual rate constants with one simple hypothesis (which is based on a kinetic model). We hypothesize that for similar ions and neutral species the rate constants for the termolecular association of neutral molecules are correlated with the ion-molecule bond strengths. With this hypothesis and our data, predictions can be made for termolecular rate constants of other double ions. Our hypothesis allows inference of a kinetic effect in termolecular association reactions; the low frequency vibrational modes of CO2 increase the rate of association to ions (compared to H2O). Electrostatic bond energy calculations show the importance of the molecular hyperpolarizability in determining both bond energies (and unusual rate constants) and the changes in bond energies for successive additions of neutrals to the cluster. We also report a few termolecular association rate constants for Ca+ and Ba+, equilibrium constants for addition to some large clusters, and observations of some additional bimolecular reactions.
Transport Properties of a Gas of Diatomic Molecules. IV. Classical Limit
Authors: Curtiss C. F. , Olmsted Richard D.
Published: February 2004

The differential cross sections for rotational excitation in collisions of diatomic molecules may be expressed in terms of the generalized phase shift, H(l̄SaSb). As with the usual phase shift, η(l̄), a semiclassical expansion of ℏ H(l̄SaSb) begins with a term of zero order in ℏ. Unlike the expansion of ℏ η(l̄), however, the next term in the expansion of ℏ H(l̄SaSb) is a purely imaginary term of order ℏ. The effect of this term in the expansion on the classical limit of certain sums and integrals of the cross sections related to the transport coefficients is considered.
Vibrational Spectrum and Force Field of Ruthenium Tetroxide
Authors: McDowell Robin S. , Asprey Larned B. , Hoskins L. Claron
Published: February 2004

Infrared and Raman spectra are reported for the vapor and liquid phases of Ru16O4 and Ru18O4. Anharmonicity corrections were estimated for the observed isotope shifts, and Coriolis constants were obtained from the infrared band contours. General quadratic force constants are calculated, using as constraints the 16O–18O and 96Ru–102Ru isotope shifts, Coriolis constants, and vibrational amplitudes; the relative effectiveness of these and the effects of the anharmonicity corrections are discussed. The force field is nearly extremal. The valence stretching force constant is fr = 6.99±0.04 mdyn/Å, appreciably less than for OsO4. Standard-state thermodynamic functions for RuO4 vapor are calculated for the temperature range 273–500°K.
Hydrodynamic Model Calculation of Momentum Correlation Functions at Long Times
Authors: Ailawadi N. K. , Harris S.
Published: February 2004

We show that recent calculations, based on a hydrodynamic model, for the long-time behavior of the linear and angular momentum autocorrelation functions for a molecular fluid contain internal inconsistencies which can lead to a physically unrealistic result. We remove these inconsistencies, and rederive the results of interest via an internally self-consistent procedure. Finally, we show that these same long-time results can be obtained by a more direct treatment of the linearized hydrodynamic equations.
Quasistatistical Complexes in Chemical Reactions
Authors: George Thomas F. , Ross John
Published: February 2004

The S matrix for inelastic and rearrangement collisions derived within Feshbach's theory of resonances can be written as the sum of SD and SC, where SD refers to direct interaction processes, and SC refers to complex (resonant) processes. For collision times short compared to characteristic times of internal motions of reactants, models of direct interactions, which assume SC to be zero, have been developed. For collision times long compared to all characteristic times of internal motion, statistical models of complex formation, which assume SD to be zero, have been formulated. Although much experimental work can be classified with either of these extreme models, intermediate cases do occur. We examine a possible method for making quasistatistical (or partial statistical) approximations on SC (for inelastic and reactive scattering), and indicate how well-known statistical models can be modified with this method to describe quasistatistical behavior. The concept of doorway states provides another category of intermediate cases and is developed briefly. The classification of experimental results into the various categories (direct interaction, complete statistical complex, partial statistical complex, doorway states, and combinations of all of these) requires a number of different measurements. Possible deductions from the various experiments are discussed and examples of reactions for the different categories are cited.
Photoionization and Autoionization of H2
Authors: Shaw Gilbert B. , Berry R. Stephen
Published: February 2004

The cross sections are calculated for direct photoionization and photoexcited autoionization of H2 for light in the region 600–800 Å. Angular distributions of directly produced photoelectrons, lifetimes for vibrationally induced autoionization, some spectral assignments, and relative intensities of photoelectrons of various energies (from autoionizing states) are also given. The method by which the Rydberg and continuum state wavefunctions are derived is similar to the correlated pseudopotential method of Tully. The results indicate that correlation has only a small effect on the differential and total cross sections for photoionization. Agreement of theoretical and experimental lifetimes for autoionization is improved by the inclusion of correlation in the wavefunction. Critical tests of the calculations could be made by experimental study of the photoelectron spectra produced when H2 is excited to certain specific autoionizing states; for these states, the theory predicts anomalously efficient autoionization associated with transfer of two vibrational quanta into electronic excitation.
Effects of Deviations from the Bethe Model on LEED Intensities for an Exactly Soluble One-Dimensional Model
Authors: Flamholz J. , Krieger J. B.
Published: February 2004

The effects of deviations from elastic scattering from perfectly periodic potentials on LEED intensities is investigated for an exactly soluble one-dimensional model. The model consists of a perfectly periodic semi-infinite substrate with delta function scatterers and a selvage consisting of a finite number of arbitrarily spaced delta functions of arbitrary scattering strength. Inelastic processes are included by means of a complex potential. Calculations are performed for the perfect crystal, the crystal with surface scatterers of different strength than in the bulk, variable lattice spacing near the surface, both localized inelastic scattering at the lattice sites and bulk inelastic processes, and combinations of these conditions. The results, which include shifting of the center and decrease in intensity of the Bragg peaks, symmetric and asymmetric broadening of the peaks and peaks not associated with Bragg reflection from the bulk, are discussed in terms of the wavefield of the incident electron in the crystal.
Nuclear Spin Polarization During the Photolysis of Di-t-buytl Ketone
Authors: Tomkiewicz Micha , Groen Arie , Cocivera Michael
Published: February 2004

Di-t-butyl ketone photolyzes in perfluoromethylcyclohexane to give pivalaldehyde, isobutylene, and 2-methylpropane which exhibit enhanced absorption and emission proton magnetic resonances as a result of nuclear spin polarization. Upon addition of CCl4 to the solution, the proton spin polarization in 2-methyl-propane disappears whereas the other products including a new product, t-butyl chloride, still exhibit the effect. Piperylene also prevents proton spin polarization in 2-methylpropane. These results are consistent with a model in which nuclear spin polarization occurs in radical pairs formed via dissociated radicals and via excited states of the ketone. Analysis of the spectra is presented in detail. For this purpose, the quantum yields for reaction from the excited states were obtained from fluorescence quenching experiments and reaction quenching data in the literature.
Investigation of Certain Auxiliary Functions Occurring in the Study of Molecular Integrals
Authors: Randić Milan
Published: February 2004

The auxiliary functions Zm, n, l+1/2(κ, τ) introduced by Barnett and Coulson in their approach to many-center integrals are related to the auxiliary functions An(p), Bm(pt) occurring in evaluations of overlap integrals in elliptical coordinates. The explicit formulas for Z functions in terms of the auxiliary functions An and Bm are given. They may provide the simplest way yet for obtaining numerical values of Coulson-Barnett Z functions. In the case of Z functions of small indices, the overlap integrals involving unconventional Slater-type orbitals arise. Z functions may be defined as particular overlap integrals. An application of this analysis leads to several relationships between different overlap integrals. In particular, when n=3 it is shown that not all overlap integrals are linearly independent. Similarly Coulomb, hybrid, and penetration integrals can be expressed in terms of selected overlap integrals. This was previously shown by Harris for Coulomb integrals only.
Torsion-Vibration-Rotation Interactions in Methanol. II. Microwave Spectrum of CD3OD
Authors: Lees R. M.
Published: February 2004

The microwave spectrum of CD3OD has been investigated in the 8–40 GHz region. Lines of the J = 1 ← 0 transition have been measured up to the fourth excited torsional state and fitted to Kivelson's semiempirical formula. The moments and product of inertia have been obtained, and the barrier height V3 determined to be 362.8 cm−1.
Near-Infrared Studies of the Structure of Water. III. Mixed Solvent Systems
Authors: Choppin G. R. , Violante M. R.
Published: February 2004

The near-infrared absorption of water in the 7000-cm−1 region has been studied for pure water and solutions of water-acetone and water-dioxane between 0 and 80°C. The absorption was resolved into Gaussian components and the component bands were used to calculate the mole fraction of water species with 0, 1, and 2 of the hydrogen atoms involved in hydrogen bonding. The data do not agree with the presence of significant effects due to Fermi resonance. A model of water with three spectroscopically distinct species agrees with the analysis of the bands.
Exciton Band Structure and Properties of a Real Linear Chain in a Molecular Crystal
Authors: Hochstrasser Robin M. , Whiteman John D.
Published: February 2004

An experimental study is presented that leads to the elucidation of the whole band structure for the triplet exciton state of 1,4-dibromonaphthalene. We show that the band states are essentially those of a linear chain characterized by nearest neighbor interactions along the c crystallographic axis. Although the crystal is topologically a three-dimensional network, for the practical purpose of energy transfer and trapping the crystal behaves as a set of linear chains. Heavy doping of DBN-h6 (host) with up to 18% DBN-d6 (guest) yielded the expected discrete spectra of a random linear array corresponding to a nearest neighbor interaction of 7.4± 0.1 cm−1 and total bandwidth of 29.6± 0.4  cm−1 for the zero-zero transition. A symmetric mode at 0+520 cm−1 was shown to have an exciton bandwidth of 15 cm−1, and an unsymmetric vibrational level at 0+250  cm−1 was shown to have a vanishing bandwidth in accordance with expectations from weak coupling theory. The quasiresonance interactions of host and guest were significant and were included in establishing the agreement between experiment and calculation. The total bandwidth is estimated to be 90± 20  cm−1. This type of doping has an effect on line shape even at very low concentration and even in undoped crystals the line shape is asymmetrical, perhaps due to impurities and imperfections that have small zero-order shifts from the band center. The intensity of transitions to the carbon-13 isotopic traps is shown to be distributed over the band states in the origin and is clearly visible in the narrow band nontotally symmetric vibrational state. The vibrational analysis of the crystal spectrum (electronic or vibrational states) is shown to be dependent on exciton effects even in the case where no Davydov splitting is observed. Spectra of DBN-h6 (guest, H) in DBN-d6 (host, D) were also studied and resonance multiplets were seen and identified in absorption and emission. We identified ··· DHD···,  ··· DHHD···,  ··· DHHHD···, and probably ··· DHDHD··· in the phosphorescence spectra at 2°K. We present a brief discussion of the effect of dimensionality on the dynamical features of energy transfer and trapping, and we show experimentally, that heavy doping (d6 in h6) enhances the phosphorescence of the crystal about 60-fold. In addition the existence at 2°K of a Boltzmann distribution over resonance multiplets leads us to propose a long-range trap-to-trap migration as part of the thermalizing process.
On the Madelung Parameter and Electrostatic Energy of Potassium Sulfate
Authors: Jenkins H. D. B.
Published: February 2004

The Madelung parameter and electrostatic energy change for the process, K2SO4(c)→ 2K+(g)+SO42−(g), have been computed as single parameter, quadratic functions of the charge Q(0) on the oxygen atoms of the SO42− ion. A comparison of the present calculations (based on the Ewald-Bertaut method) and existing calculations (based on the Evjen method) for the cases where Q(0) = 0 and −1 is made. A value for the electrostatic energy of the lattice is suggested on the basis of recent SCF calculations of Q(0) for the SO42− ion.
Diagonalization of the Hartree–Fock Hamiltonian for Occupied States
Authors: Kobe Donald H.
Published: February 2004

A variational principle is found which implies that the Hartree-Fock (HF) single-particle Hamiltonian for occupied states is diagonal. The Brillouin condition is recovered by stipulating that the arbitrary unoccupied orbitals be orthogonal to the occupied ones. When it is further stipulated that the unoccupied orbitals be orthonormal, the HF equation for occupied states is determined uniquely and no off-diagonal Lagrangian multipliers occur.
Quenching of O(1S) by O(3P)
Authors: Felder W. , Young R. A.
Published: February 2004

The rate constant for the quenching of O(1S) by O(3P) has been measured in a flow system using a pulsed source of O(1S) (1470 Å photolysis of N2O) and NO titration of flowing N atoms as a source of O(3P). The time dependence of the emission intensity of 5577 Å from O(1S) was measured as a function of O(3P) concentration. The rate constant derived from these data was 7.5 × 10−12 cm3 sec−1, a value larger than had been previously estimated. In addition, an estimated upper limit of the rate constant for quenching of O(1S) by ground state N atoms of 1× 10−12 cm3 sec−1 was obtained.
One-Phonon Inelastic Scattering of Gas Atoms in Three Dimensions by a Simplified Continuum Model of a Solid: Calculation of Energy Accommodation Coefficients
Authors: Goodman Frank O.
Published: February 2004

The quantum-mechanical theory of the one-phonon inelastic scattering of gas atoms in three dimensions by a solid surface, presented recently by F. O. Goodman [Surface Sci. 30, 1 (1972)] is used to calculate energy accommodation coefficients for the system He-W. The approximations used are the same as those in the above paper, except that the gas-surface interaction is represented by the exponential repulsive potential with zero well-depth. The theory is compared with experimental data on both equilibrium and nonequilibrium energy accommodation coefficients for He-W. With a gas-surface interaction potential inverse-length parameter corresponding to a Morse parameter for He-W in the range 1.3–1.6 Å−1, and with a (bulk) Debye temperature for W in the range 320–380°K quantitative agreement is found between theory and experiment in regimes in which the theory may be expected to be applicable. These regimes are those in which effects of bound states of gas atoms at the surface, which are neglected in the theory, are relatively unimportant.
Effect of Resonance on Vibrational Distributions in Charge Transfer Reactions
Authors: Tomcho Linda , Haugh Michael. J.
Published: February 2004

The emission from the A  2Σ+ → X  2Πi transition in HBr+ and HCl+ has been used to monitor the vibrational distribution produced in these ions by charge transfer between the neutral molecules and Ar+ and Kr+ ions over the energy range from 5000 to 100 eV. In all cases the vibrational distribution at high ion velocities approached that for a Franck-Condon excitation. The vibrational distribution from the (Ar+, HCl) and (Kr+, HBr) reaction showed appreciable change with ion velocity. The vibrational distributions were compared with distributions that were calculated using the Rapp and Francis theory of near-resonant charge transfer, modified to take vibrational overlap into account. The (Kr+, HBr) reaction showed quantitative agreement with calculations for the variation of vibrational distribution with ion velocity but the predictions for the (Ar+, HCl) reaction showed only ``semiquantitative'' agreement. A large change was predicted for the (Ar+, HBr) reaction but no change was observed. A summary is made of available data on vibrational distributions resulting from near-resonant and nonresonant charge exchange and some mechanisms are discussed.
Auger Electron Spectroscopy Investigations of the Surface Chemical Composition of Vanadium, the Vanadium Oxides, and Oxidized Vanadium: Chemical Shift and Peak Intensity Analysis
Authors: Szalkowski F. J. , Somorjai G. A.
Published: February 2004

The Auger spectra of vanadium metal and of the oxides VO0.92, V2O3, and VO2 have been studied. Chemical shifts on the order of 0.6 eV per oxidation number have been observed for the vanadium inner shell Auger transitions. Relative intensities of the oxygen and vanadium Auger peaks could be used to determine the surface composition of the different oxides. Using both the chemical shifts and the oxygen to vanadium Auger peak intensity ratios for the different vanadium oxides, the oxidation of vanadium metal to VO and then to V3O5 with increasing temperature was observed.
Absorption Spectrum of HD in the Vacuum-uv Region. Rydberg States and Ionization Energy
Authors: Takezawa S. , Tanaka Y.
Published: February 2004

The absorption spectrum of the HD molecule has been investigated in the 950–600 Å region with a 6.65-m normal-incidence vacuum spectrograph in the second order using the helium continuum as a light source. In the spectrum of cooled HD, seven Rydberg series are identified. Four consist of the Q(1) lines in the npπ ← X transitions and converging to the v=0,  1,  2,  and  3 levels of the HD+ ground state. The other three are identified as the R(0) series of the npσ ← X transitions, converging to the v=0  and  1 levels, and the R(0) series of the npπ ← X transitions converging to the v=1 level of the HD+ ground state. The lowest ionization energy (v=0,  N=0) of this molecule, obtained from the Q(1) series, is 124  569.5± 0.6  cm−1. Eight additional Rydberg series, observed near their series limits and identified as either R(0) or R(1) series, are also reported.
Tracer Diffusion and Shear Viscosity for the System 2,6-Lutidine-Water near the Lower Critical Point
Authors: Stein Arnold , Davidson Steven J. , Allegra Joseph C. , Allen Guy F.
Published: February 2004

Tracer diffusion coefficients of tritiated water in mixtures of 2,6-lutidine-water have been measured over the entire concentration range at ε =1.1× 10−4 below the critical point using the diaphragm cell. No anomaly was detected. The shear viscosity coefficients were measured across the entire concentration range at ε =2.246× 10−2, 1.268× 10−2, 7.8× 10−5 by a closed capillary viscometer. The observed anomaly in the region of the critical point was further characterized by studying the temperature dependence of the viscosity of a mixture at critical composition. These data are discussed in terms of Kawasaki's mode-mode coupling theory.
Light Scattering and Shear Viscosity Studies of the Binary System 2,6-Lutidine-Water in the Critical Region
Authors: Gülari Erdoḡan , Collings A. F. , Schmidt R. L. , Pings C. J.
Published: February 2004

Measurements have been made at the critical mixing composition of the system 2,6-lutidine-water for a (Tc-T) range of 0.001°–7.5°C for the intensity and Rayleigh linewidth and of 0.007°–27.4°C for the shear viscosity. We find that Ic−1(0) ∝ (ε)(1.26± 0.02),ξs=(2.0± 0.2)(ε)−(0.61± 0.08) Å,D=(0.290± 0.020)(ε)(0.554± 0.015)× 10−5cm2/sec,ξΓ=(2.92± 0.19)(ε)−(0.567± 0.015) Å,where ε =(Tc-T)/Tc,  Ic(0) is the intensity extrapolated to zero angle, ξΓ the correlation length from intensity measurements, D the mutual diffusion coefficient, and ξΓ the correlation length obtained from fitting the Kawasaki equation to linewidth measurements with the above value of D. We find that the Ornstein-Zernike-Debye theory is valid for (Tc-T) >0.03°C and the Kawasaki mode-mode coupling theory gives a good over-all description of the behavior of the linewidth of the Rayleigh line. The Kadonoff-Swift-Kawasaki result γ - psi = ν seems to be valid with ν=νs=νΓ. We also find that the excess shear viscosity does not exhibit a simple power law dependence on (Tc-T) as the critical temperature is approached.
Thermal Conductivity and Resonant Multipole Interactions
Authors: Nyeland Carl , Mason E. A. , Monchick L.
Published: February 2004

The influence of multipole interactions on exchanges of rotational energy in molecular collisions is investigated by means of a simple two-state impact-parameter approximation. The calculations are restricted to linear molecules and to dipole and quadrupole fields. The effects of such exchanges on the thermal conductivity of gases and of gaseous mixtures is investigated in some detail, after correcting the kinetic theory of mixtures to include exchanges between unlike molecules. We find that dipole-quadrupole and quadrupole-quadrupole interactions can have a significant effect for molecules with low moments of inertia. In particular, quadrupole interactions are important in the hydrogen isotopes, and the calculated corrections for H2 are consistent with recent experimental work by Harris. The theory seems capable of accounting for the anomalies observed by Baker and Brokaw in HF+DF and HCl+DCl mixtures in terms of multipolar ``accidental'' resonances.
Proton Magnetic Resonance Lines in Liquid Crystalline 4,4′-Dipropoxyazoxybenzene, 4,4′-Dibutoxyazoxybenzene, and Diethyl 4,4′-Azoxydibenzoate
Authors: Fink J. J. , Moses H. A. , Cohen P. S.
Published: February 2004

Experimental linewidth (2.3 to 3.1 G) vs temperature measurements are given for the broad triplet nuclear magnetic resonance lines of the nematic phases of 4,4′-dipropoxyazoxybenzene and 4,4′-dibutoxyazoxybenzene, along with a broad doublet line of the latter as it cools down to the solid state. Also observed was a 4.2-G triplet line for the smectic liquid crystal diethyl 4,4′-azoxydibenzoate. It is the first time that a triplet line has been observed for any smectic liquid crystal.
Dynamics of Intramolecular Triplet Exciton Transfer Using Electron Spin Resonance
Authors: Shain Albert L.
Published: February 2004

The rate of intramolecular triplet exciton transfer in a series of congeneric dimeric systems composed of two biphenylene subunits linked by an insulating tetravalent Group IVa atom is studied as a function of temperature using electron spin resonance. A first-order density matrix theory including the transfer process is developed. The transfer model assumes a coupling between the ``high-field'' monomer magnetic substates with the same mg only (T2 process), without inducing transitions between states of different mg (T1 processes). By comparing computer simulated line shapes with the experimental spectra, activation energies for the dynamic process are extracted. These energies are attributed to low-frequency torsional modes which are active in vibronically coupling the monomer sites. A discussion based on electron exchange and on vibronic coupling is given, and an order of magnitude calculation of the transfer probability based on the resonance excitation transfer mechanism yields numbers agreeing satisfactorily with the transfer rates obtained from experiment.
Self-Consistent Polarization Propagator Approximation as a Modified Random Phase Method
Authors: Linderberg J. , Jo/rgensen P. , Oddershede J. , Ratner M.
Published: February 2004

A formal scheme is developed for finding the particle-hole propagator by means of a self-consistent decoupling procedure analogous to the Hartree-Fock decoupling for the electron propagator. The self-consistency comes from a contour integration of the Fourier transform of the propagator, utilizing a method introduced by Coulson. The method yields oscillator strengths and excitation energies, as well as the two-particle density matrix, which allows any one- or two-particle operator expectation value to be evaluated. The stability of the scheme is discussed, and comparisons with other, related, approximations are made.