bluuebunny/crossref_metadata_2025 huggingface dataset:
Second Virial Coefficients Calculated from Atom-Atom Intermolecular Potentials
Authors: Dows David A. , Hsu Lina
Published: February 2004

Atom-atom intermolecular potentials derived from studies of crystal properties are used to calculate the second virial coefficients of a number of polyatomic gases: carbon dioxide, methane, ethane, cyclopropane, benzene, and ethylene. Calculated virial coefficients are in moderate agreement with observed data and could be brought into excellent agreement with changes in attractive potential parameters of a few percent. Effective intermolecular central potentials—averages including rotational correlation—for methane, ethane, and benzene are compared with previous averaged potentials. It is possible to obtain good fits to the data with potentials of greatly differing well depths and ``molecular volumes.'' The effective potential is temperature dependent and in the case of benzene clearly reflects the anisotropy of the molecule at lower temperatures.
Thermal Properties of Cesium
Authors: Pal Satya
Published: February 2004

The frequency distribution, specific heat, electrical resistivity, and thermal resistivity of cesium are calculated using the lattice dynamical model of Sharma and Joshi. The calculated specific heats are compared with the calorimetric data in terms of the equivalent Debye temperatures. The computed Debye temperatures and the electrical resistivity are in fair agreement with the experimental data but the model overestimates the thermal resistivity.
Lifetimes of the v′ =0, 1, 2 Levels of the A 2Σ+ Electronic State of NO
Authors: Copeland G. E.
Published: February 2004

The lifetimes of the v′=0, 1, 2 levels of the A 2Σ+ state of NO have been measured by monitoring 17 transitions of the NO γ bands. A new cold cathode discharge tube was used in conjunction with the delayed coincidence technique for measurement of lifetimes. A nonlinear least squares program was used for data analysis in order to estimate cascade contributions. Values obtained for lifetimes are τ (v′=0)=108± 6, τ (v′=1)=106± 7, and τ (v′=2)=95± 8 nsec. Using Morse potential Franck—Condon factors, the electronic transition moments are calculated to be 0.195, 0.197, and 0.208 a.u.
Path Integrals and Semiclassical Tunneling, Wavefunctions, and Energies
Authors: Freed Karl F.
Published: February 2004

The semiclassical limit of Feynman path integrals is investigated in order to determine those classical trajectories which contribute to tunneling processes. The semiclassical bound state energies, wavefunctions, and scattering phase shifts are directly recovered from the poles and residues of the semiclassical Green's function in energy space. Some extensions to cases of tunneling and bound states for multidimensional nonseparable potentials are discussed.
Infrared Matrix-Isolation Studies of BrCN and CICN: Fermi Resonance and Dimer Structure
Authors: Freedman Teresa B. , Nixon Eugene R.
Published: February 2004

The infrared spectra of CICN and BrCN in argon and krypton matrices at 20°K have been investigated. There is good evidence that for the monomeric species the bending mode is split by the matrix environment and that the first overtones of these two bending components form a Fermi resonant triad with the v1 fundamental. The frequencies and intensities of the unperturbed levels and the Fermi coupling constants have been calculated. The absorption bands due to dimeric species are consistent with a linear or nearly linear configuration for the dimer.
An ESR Study of Anisotropic Rotational Reorientation and Slow Tumbling in Liquid and Frozen Media
Authors: Goldman S. A. , Bruno G. V. , Polnaszek C. F. , Freed J. H.
Published: February 2004

A careful study is described of the ESR lineshapes for the peroxylamine disulfonate (PADS) radical dissolved in 85% glycerol solution and in frozen water and D2O. In the frozen media, spectra characteristic of rotational correlation times τR ranging from 1.0 × 10−11sec to > 10−6sec are obtained, while the range in glycerol is from 1 × 10−10sec to >10−6sec. The very rapid rotational motion in frozen water is taken to imply that PADS is rotating in a clathrate cage. The activation energies in ice and 85% glycerol are 14.7 ± 0.1 and 11.3 ± 0.1 kcal/mole, respectively, (from motional-narrowing data). The value for ice is very similar to that obtained for other rate processes in ice. The lineshapes for τR ≲ 10−9sec are analyzed in terms of the familiar spin-relaxation theories valid in the motionally narrowed region. These results are well fitted by the model of axially symmetric rotational diffusion with the symmetry axis in the plane of the N, O, and S atoms and parallel to a line passing through the two S atoms. Diffusion about this axis is found to be 2.9 ± 1 and 4.7 ± 1 times faster for frozen water and glycerol solvent, respectively than about the other axes over a wide range of values of average τR̄. It was possible to obtain these results, because accurate measurements of the g and A tensors for PADS in these media could be made from the well-resolved rigid spectra at X band and 35 GHz; the intrinsic widths in D2O are only about 1.5 G. The spectra in the slow-motional region τ R¯ >10−9sec were simulated utilizing the slow tumbling formulation of Freed, Bruno, and Polnaszek appropriately generalized to include completely asymmetric g and A tensors. The simulated spectra are found, in general, to be in quite good agreement with experimental observations. The agreement is clearly improved by introducing axially symmetric rotational diffusion, as found for the motional-narrowing region, into the simulations. Spectra are simulated for Brownian rotational diffusion as well as for simplified models of free diffusion, which includes inertial effects, and for diffusion by jumps of substantial angle. Improved agreement with experiment is found with some of these latter models. What appears to be a surprisingly small nonsecular linewidth contribution in the motional-narrowing region is briefly discussed in terms of these models.
On the Calculation of the Coefficient of Self-Diffusion
Authors: Isbister D. J. , McQuarrie D. A.
Published: February 2004

Simple parametrized analytic expansions for both the velocity autocorrelation function and its associated memory function are presented. Two methods have been used to fix the parameters. One is to use the Maclaurin expansion of the velocity autocorrelation function through terms in t4. The other is to assume that the velocity autocorrelation function decays exponentially for long times and to use only the coefficients of t2 in the Maclaurin expansion. The results are compared to the molecular dynamics calculations of Rahman and Levesque and Verlet.
Infrared Absorption Spectra of Isotopic Ozone Isolated in Rare-Gas Matrices
Authors: Brewer Leo , Wang J. Ling-Fai
Published: February 2004

Some of the isotopic ozone molecules of different combinations of oxygen-16 and oxygen-18 have been synthesized and isolated in rare-gas matrices at 20°K. Their infrared absorption bands have been identified. The isotope effects are calculated for symmetrical as well as unsymmetrical isotopic ozone molecules.
Energy-Deposition Functions in Mass Spectrometry
Authors: Meisels G. G. , Chen C. T. , Giessner B. G. , Emmel R. H.
Published: February 2004

Methods for the evaluation of internal energy distribution functions resulting in ions from impact of energetic electrons are examined and their shortcomings are analyzed. It is shown that energy-deposition functions can be estimated from photoelectron spectra and photoionization cross sections if the Bethe—Born treatment of collisions is employed, but allowance for autoionization and multiple ionization processes is not possible. Deposition functions are calculated for methane, ethane, and ethylene. Mass spectra obtained by folding the functions into breakdown graphs are in reasonable agreement with experimental fragmentation patterns for 70−eV electrons.
On the Convergence of Multibody Expansions for Short Range Intermolecular Forces. A SCF Calculation of He3 and He4 Systems
Authors: Novaro O. A. , Beltran-lopez V.
Published: February 2004

In this paper we calculate the potential energy surface of He3 within the SCF—LCAO—MO approximation to test the pairwise additivity of intermolecular forces at short range. We obtain large nonadditive contributions at very close distances, but in general, in the neighborhood of the van der Waals well (∼5.6 a.u.), they are negligible. However the study of a few He4 configurations shows that four-body effects can be important enough to question the convergence of many-body expansions.
14N Nuclear Quadrupole Resonance in Compounds Containing N–N Bonds. I. Hydrazines
Authors: Sauer Enrique G. , Bray P. J.
Published: February 2004

The 14N nuclear quadrupole resonance spectra at 77°K of several hydrazines are reported and analyzed in the framework of a semiempirical theory extended to cover cases of large asymmetry parameters. The atomic-orbital occupation numbers obtained by this analysis are linked with the hydrogen-bonding configuration in the solid state. The results obtained indicate that the hydrogen bonding ability of the amino nitrogen exceeds that of the substituted nitrogen atom and decreases in the order: hydrazine>alkyl hydrazines>N-amino heterocycles>aryl hydrazines.
Pulse Radiolysis of Alcohol Glasses at 77°K: Mechanism of Electron Trapping
Authors: Kevan Larry
Published: February 2004

Ethylene glycol/water (50/50), methanol/water (95/5), ethanol, 1-propanol, 2-propanol, and 2-propanol/methyltetrahydrofuran (50/50) glasses were studied by pulse radiolysis at 77°K. In each glass a trapped electron spectrum is observed which shifts toward the blue on a microsecond timescale. This suggests a shift from shallow to deeper traps. The spectral shift appears to occur more rapidly in more polar matrices. This is the opposite of the direction expected based on relative matrix viscosities. When 10−2M biphenyl or benzyl chloride is added to 2-propanol glass about 40% of the electrons are scavenged. The resulting biphenyl anion and benzyl radical spectra show no transient changes in intensity after the pulse while the residual trapped electron spectrum shows the same shift as before. Both the polarity and the solute effects indicate that molecular reorientation around the electron is responsible for the transient spectral shift. A short-range electron—matrix interaction would presumably cause faster reorientation in more polar matrices. An alternative mechanism of a redistribution of electrons among shallow and deep preformed traps seems to be ruled out.
Kinematics of the C+(D2, D)CD+ Reaction
Authors: Iden C. R. , Liardon R. , Koski W. S.
Published: February 2004

The energy and angular distributions of CD+ formed by the reaction C+(D2, D)CD+ were measured for barycentric energies between 3.47 and 9.14 eV. From the threshold to an energy of 4.4 eV the reaction was found to go through a persistent complex, and at higher energies the reaction proceeded by direct mechanisms. CD+ was detected at energies considerably higher than the critical energy obtainable from the spectator stripping model. Measured values of Q, the difference between the relative kinetic energy of the products and reactants, and available theoretical calculations were used to infer the possible electronic states of the products.
Low-Temperature Absorption Spectrum of Uranium(3+) Formate Energy Level Scheme of Uranium(3+)
Authors: Drożdżyński Janusz , Conway John G.
Published: February 2004

The absorption spectrum of thin films of U(HCOO)3 was measured at 298, 77, and 4°K in the range 4000–24 000 cm−1. Electrostatic, spin—orbit, and configuration-interaction parameters were obtained by least-squares fitting to 12 observed levels for U(HCOO)3. The obtained parameter values (in cm−1) are: E1=2779, E2=14.1, E3=271.6, ζ5f=1656.4, α=17.5, β = −479, γ=1000. A good agreement with experiment is observed for all calculated levels and a number of new assignments of excited levels of U(3+) are proposed. Intensity calculations were carried out and considered in the problem of level assignment.
31P Chemical Shielding Anisotropy in Solids. Single Crystal and Powder Studies at 99.4 MHz
Authors: Gibby M. G. , Pines A. , Rhim W.-K. , Waugh J. S.
Published: February 2004

Free induction decays of a single crystal of P4S3 and powders of Zn3P2, Mg3P2, and P4S10 are studied at 99.4 MHz. The P4S3 molecule is found to have two 31P chemical shielding tensors, one for the single apical phosphorus and one for the three phosphorus atoms of the basal triangle in the molecule. The tensors are more or less symmetric and the eigenvectors for the unique elements are found to be colinear within experimental error, thus suggesting that there is rapid motion about the C3 axis of the molecule. A comparison with theoretical spectra bears this out. The general character of the spectra agrees with the crystal structure of the compound found by x-ray analysis and the isotropic shielding values agree with a previous spinning-sample study. 31P powder patterns for Zn3P2 and Mg3P2 yield chemical shielding parameters and the spectra appear to disagree with previous pulsed and spinning-sample experiments on these compounds. The spectrum of P4S10 indicates rapid molecular motion at room temperature. The possibility of low-temperature and liquid experiments is discussed.
Depolarized Light Scattering: Theory of the Sharp and Broad Rayleigh Lines
Authors: Keyes Thomas , Kivelson Daniel
Published: February 2004

A statistical theory of depolarized laser light scattering is developed, based upon the projection operator transport theory of Mori. It is assumed that the autocorrelation function of the dielectric tensor is proportional to the autocorrelation function of a ``primary'' variable, and the time evolution of this autocorrelation function is calculated by means of a pair of coupled linear transport equations in which the primary variable is coupled to a ``secondary'' variable. The theory ignores some of the k−dependent fine structure of the spectra and concentrates upon explaining the sharp and broad depolarized Rayleigh lines which dominate the spectra. It is concluded, in contradiction to numerous existing theories, that the observed spectra cannot be explained in terms of a single primary variable. It is believed that the sharp line arises from molecular reorientations in the role of primary variable and that a separate mechanism, dependent upon a distinct primary variable such as the one describing local field fluctuations, gives rise in large part to the broad line. The theory is also used to obtain autocorrelation functions for reorientation in an ``extended diffusion model limit.'' The relationships between one- and two-particle orientational correlation functions are discussed, and it is shown how the discrepancies between reorientation times determined by NMR and those determined by light scattering might possibly be understood on this basis.
Mechanism of Oxidation of Carbon Monoxide in Presence of Chromium Carbonyl
Authors: Izod T. P. J. , Kistiakowsky G. B. , Matsuda S.
Published: February 2004

The catalytic effect of small concentrations of chromium vapor, added in the form of Cr(CO)6, on the oxidation of CO is investigated at temperatures between 1100 and 2200°K in shock waves using two different methods of product detection. The formation of CO2 in incident shock waves of CO/O2/Ar mixtures containing between 100 and 500 ppm Cr(CO)6, at a total gas density of about 5.0·1017 particles/cc, was followed by ir emission over a time scale of 1500−μsec particle time. The rate of CO2 formation was much larger than in the absence of Cr(CO)6, and the CO2 concentration was observed to rise linearly with time. A complete intermediate and product analysis was performed by shock heating various CO/O2/Ne mixtures containing 0.4% Cr(CO)6 and observing the reaction species in reflected shock waves by means of a time-of-flight mass spectrometer during 180 μsec. The thermal decomposition of Cr(CO)6 is very rapid at all experimental temperatures. The oxides of chromium, CrO, CrO2, and CrO3, were observed together with Cr. A chain mechanism involving these oxides is proposed to account for the catalysis of CO oxidation by Cr(CO)6, and rate constants for the chain reactions are estimated. A rather sudden cessation of the catalytic effect was observed under varying conditions of (Cr) and temperature. Mass spectrometric analysis indicated the disappearance of atomic Cr and its oxides from the gas phase under these conditions. A very rapid condensation of Cr atoms when chromium vapor becomes highly supersaturated is proposed to account for this phenomenon.
Photoeffects in the Pb–PbO Cell
Authors: Houston J. Richard , Michels Walter C.
Published: February 2004

Studies have been made of the current—voltage characteristics of Pb–PbO cells in the presence of illumination varying both in area and intensity. The data are consistent with the supposition that the photocreation of electron-hole pairs both increases the effective area of the cell and breaks down rectification at the surface electrode. A revised form of the model previously presented by Laws is proposed.
Photodetachment of Electrons from Phosphide Ion; the Electron Affinity of PH2
Authors: Smyth Kermit C. , Brauman John I.
Published: February 2004

The relative cross section for photodetachment of electrons from PH2− has been measured in the wavelength region 725–1020 nm (1.71–1.22 eV). An ion cyclotron resonance spectrometer has been used to generate, trap, and detect the negative ions, while two light sources have been employed to study photo-detachment: a 1000-W xenon arc lamp with grating monochromator and a continuously tunable laser. A single sharp threshold in the cross-section curve has been observed, and a detailed analysis has yielded a value for the electron affinity, E.A. (PH 2·) = 1.25 ± 0.03 eV.
Microwave Spectrum of Benzoyl Fluoride
Authors: Kakar Ramesh K.
Published: February 2004

The rotational transitions of benzoyl fluoride in the ground and first seven excited torsional states, two ``other'' vibrational modes, and the second excited state of one of these ``other'' modes have been assigned. The term values of these states with respect to the ground state have been derived from relative intensity measurements. The term value of the torsional fundamental has been determined to be 59.5 ± 3 cm −1 which gives a twofold barrier to internal rotation of 1560 ± 160 cm −1 for the –COF group. The variation of inertia defect with vibrational state has been used to aid the assignment of in plane or out of plane for the two ``other'' modes. The fundamentals at 168 ± 10 cm −1 and 215 ± 10 cm −1 are tentatively assigned to the out-of-plane wag and in-plane bend, respectively, of the –COF group. There is a close agreement between the observed inertial coefficients in excited torsional states and those derived on the basis of a molecular model with one degree of internal freedom.
Resolution Enhanced ESR Spectra of the Trapped Electrons in an Alkaline Ice
Authors: Ohno K. , Takemura I. , Sohma J.
Published: February 2004

The hyperfine coupling constant and the paramagnetic relaxation characteristics of e t − in the γ-irradiated NaOH ices annealed at 110°K were studied by resolution enhancement of ESR spectra. The structure of the trapping site was also studied. The resolution of enhanced spectra depends on both the annealing time and the solute concentration, but not on γ-irradiation dose. The solute concentration dependence is discussed by a simple model.
Vibronic Interactions. The Adiabatic Approximation
Authors: Fulton Robert L.
Published: February 2004

A general treatment of vibronic interactions is given in terms of the adiabatic approximation. It is pointed out that the terms arising from the dependence of the electronic transition moment on nuclear configuration which are commonly used to discuss vibrational borrowing are also closely related to the terms involved in the coupling of the adiabatic wavefunctions. Formulas for spectral intensities and band strengths are given. An inequality is derived which states that if the excited state geometry closely approximates the ground state geometry, the emission band strength is less than the absorption band strength. The interplay between the coupling of the adiabatic wavefunctions and the dependence of the electronic transition moment on nuclear coordinates is illustrated by a simple model which complements that given by Fulton and Gouterman [J. Chem. Phys. 35, 1059 (1961)]. It is shown that in weak coupling spectral intensities due to vibrational borrowing can be understood qualitatively, but not quantitatively, by the Herzberg—Teller mechanism [Z. Physik. Chem. B21, 410 (1933)], while in the case of strong coupling both the coupling of the adiabatic wavefunctions and the dependence of the transition moment on nuclear configuration must be included to obtain a quantitative description of intensities. Comparisons are made with the previous model.
Interactions between Oppositely Charged Nonspherical Ions. I. Potential Energy Function
Authors: Hay Patrick Fenton , Kozak John J.
Published: February 2004

In this paper we apply the theory of Steele to the problem of determining the pairwise interactions between oppositely charged nonspherical ions imbedded in a vacuum. The diatomic model of Sweet and Steele was extended by superimposing at either end of each linear, symmetric rod a Coulombic center characterized by a r−1 distance dependence. With respect to the consequent charge—charge interactions, a value of the Onsager coupling parameter was chosen which allowed a more detailed study of the relative importance of Lennard-Jones versus Coulombic forces; in effect, the ions were assumed to be only partially charged. Coefficients in the expansion of the potential energy function were calculated numerically, and changes in the profiles of the resulting curves [Ul,l′,m(r) as a function of interionic distance] were noted for different values of R/σ (where R is the length of the rod and σ is the usual Lennard-Jones range parameter). The trends observed were compared with those found by Sweet and Steele in their study of the diatomic model.
Symmetry Labeling of Low Lying Electronic Levels of EuGaG by Means of Light Scattering Techniques
Authors: Dabrowski I. , Grünberg P. , Koningstein J. A.
Published: February 2004

A discussion is given of the Raman tensors of the F07→ F17, F07→ F27, and the F17 intermanifold transitions of the compound EuGaG. Some of these tensors are completely antisymmetric and the correlation is given of tensors, symmetry of the states, and crystal field parameters.
Single Crystal Electron Spin Resonance Spectra of X-Irradiated Potassium Hydrogen Malonate
Authors: Nicklin Robert C. , Farach Horacio A. , Poole Charles P.
Published: February 2004

Single crystals of x-irradiated potassium hydrogen malonate were studied by electron spin resonance. The principal radical produced by the irradiation was (COOH) (·CH) (COOK). The main hyperfine doublet arose from the coupling to the α hydrogen, and satellite lines from four more distant extramolecular protons were identified. Previous theory on the positions and intensities of satellite lines was extended to include the present case. A model was prepared for the arrangement of the molecules in the unit cell.
Conformation Studies of Molecules Partially Oriented in the Nematic Phases: NMR Spectra of 5,5′-Bisisoxazole
Authors: Bucci P. , Veracini C. A.
Published: February 2004

A high-resolution NMR study of 5,5′-bisisoxazole in different liquid crystals and at various temperatures is reported. An interpretation of all data, based on a simple model for conformational equilibrium in solution, is given. Very good agreement with a CNDO calculation of the potential energy for the internal rotation of the two rings is found.
Green's-Function Method with ``Non-muffin-tin'' Potentials for Molecules and Clusters
Authors: Scherz Udo
Published: February 2004

The Green's-function technique for molecules or multiple scattering model is generalized to potentials which consist of a muffin-tin potential plus a spherically symmetric potential. The method is based on a Green's function for particles in a spherically symmetric potential. A method to calculate the Green's function is presented and the secular equation, which determines the energy levels, is derived. The method can be used to calculate the energy levels of molecules with a more realistic potential as well as to find the impurity energy levels of semiconductors in the band gap.
Electron Paramagnetic Resonance Absorption in Oriented Phosphorescent Chrysene at Magnetic Fields below 125 G. I. Multiplet Structure in Low-Field EPR Spectra
Authors: Gerkin Roger E. , Winer Arthur M.
Published: February 2004

Multiple electron paramagnetic resonance absorptions by phosphorescent chrysene-h12 and -d12 in single crystals of p-terphenyl-h14 and -d14 and symmetric octahydroanthracene (OHA) have been investigated, principally in static magnetic fields below 125 G, and in the temperature range from 64 to 250°K. The zero-field splittings of the lowest triplet state of chrysene-d12 have been determined very precisely in experiments at static fields from ·25 to ·3 G. The high-precision splittings determined for the twenty resonance absorptions observed for chrysene-d12 in p-terphenyl (at ·0.116, 0.063, and 0.053 cm−1) could be correlated into seven triples corresponding to seven distinct triplet-state species. Only six absorptions were observed for chrysene-d12 in OHA, and these could be correlated into two triples of splittings. Decisive evidence is presented that all 26 resonance absorptions observed arise solely from chrysene-d12 and not (in part) from impurities. For p-terphenyl host, direct experimental evidence has been obtained for orientational inequivalence among the chrysene-d12 guest triplet states associated with the different zero-field splitting triples. [In a subsequent report (II), the orientations of the inequivalent guest triplet tensor axes with respect to each other and to the p-terphenyl molecular and crystal axes have been quantitatively calculated from data presented here and from supplemental data.] The temperature dependences of the triplet lifetimes of the sets of chrysene-d12 guests associated with different zero-field splittings have been investigated for both p-terphenyl and OHA hosts. In addition, the temperature dependences of the zero-field splittings of chrysene-d12 in OHA have been determined over an extended range of temperature. The effects on the chrysene zero-field splittings of the deuteration of both guest and host (p-terphenyl) have been investigated. A limited investigation of the system chrysene-d12 in biphenyl is also reported.
Photoionization of Vibrationally Excited Nitrogen
Authors: Cook G. R. , McNeal R. J.
Published: February 2004

A quadrupole mass spectrometer with a photoionization source has been used in conjunction with a flowing nitrogen afterglow to obtain the photoionization spectrum of vibrationally excited nitrogen (N2*) at a spectral resolution of 0.03 nm in the interval 79.58–84.20 nm. This wavelength interval lies below the photoionization threshold of N2 (v″=0). More than 50 new preionized bands and an underlying continuum have been observed. Many of the new bands are attributed to preionized transitions between N2 (X  1Σg+, v″=1 to 4) and Rydberg states belonging to series that converge either to N2+ (A  2Πu) or to vibrationally excited levels of N2+ (X  2Σg+). From estimates of the concentrations of various vibrationally excited states of N2 and measurements of the ionizing photon flux as a function of wavelength, we have estimated the photoionization coefficients of the new preionized bands and continuum. The relative probabilities of various transitions from N2* to the preionized Rydberg states are different from transitions to the same upper states from N2 (v″=0) owing to different Franck—Condon factors. The N2* continuum is a sum of continua from all of the vibrational states, each of which rises only slowly from threshold because of the unfavorable transition probability for direct ionization of N2 when Δ v ≠ 0. Many of the preionized bands can be attributed in large part to a specific vibrationally excited level, and the application of photoionization as a sensitive tool for studying kinetic processes involving N2* is proposed. A detection limit of 1011 molecules/cm3 is obtainable with the present apparatus. Preliminary experiments on the quenching of N2* by N2O and CO2 are reported.
Electron g3 Configurations in LS Coupling
Authors: Patera J.
Published: February 2004

Total orbital momentum and total spin are good quantum numbers for a complete basis which we construct as explicit linear combinations of orthonormal vectors (m1m2m3), where integers | mi |  ≤ 4. Matrix elements of generators of the orbital momentum group are found explicitly in the basis (m1m2m3) and a one-to-one correspondence between (m1m2m3) and Gel'fand—Tseitlin patterns of SU (9) is shown. The multiplicity problem is solved systematically by simplicity conventions similar to those introduced by Racah for the cases where his classification scheme for higher fn configurations failed. Every angular momentum multiplet we construct belongs to one irreducible representation of O (9) only.
Far-Infrared Spectra of Ring Compounds. VIII. The Effect of a Finite Central Barrier on Pseudorotation in Five-Membered Rings
Authors: Ikeda Tatsuya , Lord R. C. , Malloy Thomas B. , Ueda Toyotoshi
Published: February 2004

A two-dimensional Schrödinger equation appropriate to pseudorotation in five-membered rings with the potential function V=(z1 2 + z2 2)2 + B (z1 2 + z2 2), where z1, z2 are reduced coordinates of ring bending and twisting, has been solved numerically by several different approaches. The result of the two-dimensional approach, as opposed to the method often used of solving an angular equation alone, is to show a negative curvature in the pseudorotation energy level separations and an increase in the ``pseudorotational constant,'' β, in the excited states of the radial mode. These effects are a direct result of the finite central barrier for B < 0, given by B2/4. This increase in the pseudorotational constant in the excited state of the radial mode and the negative curvature of the transition frequencies had already been observed experimentally in the case of tetrahydrofuran and 1,3-dioxolane.
Spectroscopic Determination of the Barrier to Planarity in Cyclopentane
Authors: Carreira L. A. , Jiang George J. , Person Willis B. , Willis James N.
Published: February 2004

A measurement of the Raman spectrum of cyclopentane in the gas phase under moderately high resolution reveals that the ground state radial transition at 272.5 cm−1 has two associated Q branches at 265.3 and 257.8 cm−1, corresponding to the first two excited transitions of the radial mode. With this information and the pseudorotational combination and difference bands with the CH2 deformation observed by During and Wertz, we have used both the perturbation treatment developed by Ikeda et al. and the direct matrix diagonalization program developed earlier to obtain the potential energy surface for cyclopentane in the ground state and in the first excited state of the CH2 deformation. In the ground state the barrier to planarity is found to be 1824 ± 50 cm−1 (5.21 kcal) and the equilibrium out-of-plane amplitude qe=0.47 ± 0.025 Å.
Localization of Energy in Organic Molecules as Revealed by Dynamic Nuclear Polarization of Diphenylpicrylhydrazyl in Polystyrene
Authors: Turkevich John , Soria Javier , Che Michel
Published: February 2004

The model of the free radical in an amorphous polystyrene matrix was studied by dynamic polarization to obtain insight into transfer of electron spin energy into thermal energy. A solid-state effect was obtained for protons in 5% DPPH in polystyrene at 9.5 GHz at liquid-helium, liquid-nitrogen, and even at room temperature with ordinary microwave power. The proton spin relaxation took place by spin-diffusion mechanism. The electron spin relaxation took place by direct process from liquid-helium to room temperature suggesting that the slow step in the electron spin relaxation took place in the molecule of the DPPH rather than in the polystyrene. The results obtained indicate possibilities of further enhancing nuclear orientation for nuclear reaction by modification of free radical and for constructing model systems for energy storage useful in catalysis and biochemical enzyme reactions.
Lattice Modes and Intermolecular Potential of Orthorhombic Polyoxymethylene
Authors: Boerio F. J. , Cornell D. D.
Published: February 2004

Lattice modes have been observed at 37 and 81 cm−1 in Raman spectra of orthorhombic polyoxymethylene. The normal modes of the orthorhombic polyoxymethylene crystal have been calculated and used to assign the lattice modes. The intermolecular potential has been evaluated and used to compute the dispersion curves and frequency distribution of the crystal. The calculated frequency distribution has been compared to that observed experimentally by inelastic neutron scattering.
Determination of the Symmetry of the First Excited Electronic State of Benzyl by Rotational Contour Analysis of Vibronic Bands of the Emission Spectra of C6H5CH2, C6H5CD2, and C6D5CD2
Authors: Cossart-Magos Claudina , Leach Sydney
Published: February 2004

Theoretical calculations have differed in their predictions as to the symmetry of the first excited state of benzyl. Furthermore, conflicting interpretations have been given to previous experimental results. Rotational band contour analysis of high resolution gas phase emission spectra of C6H5CH2, C6D5CD2, and C6H5CD2 are here used to determine this electronic symmetry. A discussion is given of the treatment of new problems which arise in the band contour analysis of emission spectra and of free radicals as compared with previous contour work on absorption spectra of stable molecules, in particular, as regards the determination of molecular geometry, temperature effects and contour program modifications. Qualitative and quantitative criteria for matching experimental and calculated contours are made explicit. Nonmatching features are assigned to hot bands, using supporting assignments. The effect on calculated contours of the interpolation procedure used in Parkin's program is discussed in the Appendix. Good fit of calculated to experimental contours for type A and type B vibronic bands of the three isotopic benzyl radicals, including the vibronic origin band of the C6H5CH2 species, leads to the conclusion that the first doublet-doublet electronic transition in benzyl is 1 2A2–1 2B2. This agrees with an earlier experimental assignment, based on the observation of a2 vibrations in the fluorescence spectrum of benzyl in crystalline cyclohexane solution but is in disagreement with the 2 2B2–1 2B2 assignment of Johnson and Albrecht based on three-step photoselection studies in glassy solutions.
Stability of Gas Bubbles in a Deformable Material Containing Dissolved Gases
Authors: Yang Wen-Jei
Published: February 2004

This paper analyzes the stability of gas bubbles in a medium which contains dissolved gases and deforms due to creep. The effects of mass diffusion and surface tension on the dynamic behavior of a gas bubble are taken into account. Asymptotic solutions valid for large times are obtained which predict the radius-time relation, the creep rate, and the rate of diffusion of dissolved gases induced by the growth of a gas bubble in an oversaturated solution. The case where the bubble is situated in a saturated or undersaturated solution is also examined.
On the Franck—Condon Factor for Continuous Spectra
Authors: Riess Ilan
Published: February 2004

The Franck—Condon factor for a continuous absorption spectrum has by semiclassical consideration the shape of the ground state density probability function. It is shown here that the very deviation from the semiclassical approach introduces additional peaks as well as asymmetries into the continuous spectra. An approximate formula for the Franck—Condon factor for the transition from the v=0 state of a diatomic molecule into a continuum is given, where the repulsive potential appears explicitly. The approximation is then investigated both analytically and numerically, and quantititative examples for the O2 molecule are given.
Electron Paramagnetic Resonance Detection of the Photoexcited Triplet State of Some Conjugated Phenylacetylenes in Glasses
Authors: Wade Charles G. , Webber S. E.
Published: February 2004

The ``Δm=2'' EPR transitions have been observed for the photoexcited triplet states of phenylacetylene, phenylmethylacetylene, phenylethylacetylene, and diphenylacetylene in glasses at 77°K. The reduced zero field parameters D* have been found to be nearly invariant for these molecules (ranging from 0.145–0.152 cm−1). This result is discussed semiquantitatively from two points of view: (1) Hückel MO theory with configuration interaction, and (2) an intramolecular exciton theory.
Scattering of Argon Beams with Incident Energies up to 20 eV from a (111) Silver Surface
Authors: Hays W. J. , Rodgers W. E. , Knuth E. L.
Published: February 2004

Angular scattering distributions for argon atoms incident on well-characterized epitaxially deposited (111) Ag surfaces have been measured for incident-beam energies up to approximately 20 eV. The scattering pattern is a specularly directed single lobe. Its width increases as the incident-beam energy increases, as is expected for structural scattering. The direction of the maximum scattered signal is about 3° supraspecular for the entire energy range (3–18 eV) covered in these experiments. The expected increase of the scattered-beam peak amplitude with increase of beam energy is observed at the lower energies. A peak-amplitude decrease with beam-energy increase at higher beam energies is observed here for the first time. Bombardment of the surface with an argon beam with energy above an observed threshold energy reduced significantly the scattering-distribution width for a thermal-energy helium-beam probe. It is found that, at least under certain surface conditions, a high-energy argon beam is a more sensitive surface probe than is a thermal-energy helium beam.
Distinguishable Electron Method (DEM) for Electronic Structure Calculations. IV. Polarizability of Three- and Four-Electron Atoms
Authors: Scott William R. , Kirtman Bernard
Published: February 2004

The distinguishable electron perturbation method is applied to the polarizability of three- and four-electron atoms, with results comparable to much more complicated coupled Hartree-Fock calculations. For the initial approximation we use a product of Slater-type orbitals with exponents optimized via the Rayleigh-Ritz principle. Using accessible correlation expressions the polarizability can be computed to first order in correlation without resorting to correlated wavefunctions. The polarization functions required for this calculation are found exactly as solutions of one-electron perturbation equations. We introduce adjustable parameters into these equations which do not affect the energy but are optimized with respect to the polarizability property.
Luminescence Quantum Efficiency of Gd and Tb in Borate Glasses and the Mechanism of Energy Transfer between Them
Authors: Reisfeld Renata , Greenberg Esther , Velapoldi Rance , Barnett Baruch
Published: February 2004

A study of the quantum efficiency of the luminescence of gadolinium and terbium in borate glasses and of the energy transfer between these ions is presented. From our measurements of fluorescence decay times, absorption, fluorescence, and excitation spectra, we calculated the fluorescence quantum yield of the 6P7/2 gadolinium and the 5D4 terbium levels on excitation to higher gadolinium and terbium levels, respectively. The energy transfer rates between gadolinium and terbium in borate glasses were calculated on the basis of the above measurements. These measurements were performed for gadolinium and terbium concentrations ranging from 0 to 4 wt%. Our results show that the energy transfer occurs mainly between the 6P7/2 gadolinium level and (5D0, 5H7) terbium levels and is due to a dipole-dipole interaction. It is concluded that the energy transfer between gadolinium and terbium is a phonon assisted process.
Far-Infrared Spectra of Ring Compounds. VII. The Ring-Puckering Vibration in Chlorocyclobutane, Bromocyclobutane, and Cyanocyclobutane
Authors: Blackwell C. S. , Carreira L. A. , Durig J. R. , Karriker J. M. , Lord R. C.
Published: February 2004

The infrared spectra of chlorocyclobutane, bromocyclobutane, and cyanocyclobutane have been recorded in the range 200–33 cm−1. Under high resolution each of the spectra in this range show four or five distinct Q branches, which have been assigned to transitions between energy levels of the ring-puckering vibration for the equatorial isomer of each molecule. The transitional frequencies were fitted to asymmetric single-minimum potential functions of the form V(X)=aX4 − bX2 + cX3, where X is the ring-puckering coordinate. For V in cm−1 and X in angstroms, the respective values of a, b, and c are: chlorocyclobutane, 6.048·105, 2.039·104, 11.78·104; bromocyclobutane, 11.28·105, −7.247·104, 45.21·104; cyanocyclobutane, 10.04·105, −6.61·104, 42.63·104.
Effective Polarizability of a Point Dipole near a Metal Surface with a Thomas-Fermi Response
Authors: Antoniewicz P. R.
Published: February 2004

The response of a polarizable atom in the vicinity of a metal surface to an external field is greater than that of an atom in free space due to the field of the image dipole moment. The effective polarizability of a polarizable atom is calculated assuming a Thomas-Fermi response of the metal. Exact solutions are found for a monopole and a dipole potential near a metal surface.
Isotope Exchange vs Abstraction for H + DCl
Authors: Wood Gerry Odell
Published: February 2004

Rates of isotope exchange reactions in deuterium chloride—hydrogen mixtures photolyzed at 1849 Å have been measured by mass spectroscopy. Under conditions where reactions of product molecules were negligible quantum yields of HD and D2 were calculated using DCl for actinometry. Large HD quantum yields indicate that chain reactions occur. The ratio of HD to D2 formed in these chain reactions is shown to be equal to the ratio k2/k3 of rate coefficients for the abstraction (2), H + DCl → HD + Cl, and the exchange (3), H + DCl → HCl + D. From quantum yields at 27–225°C this ratio is calculated to be k2/k3=(850 ± 200) exp [ − (2220 ± 180) / RT]. A quantum yield of D2 independent of chain lengths and with little temperature dependence is attributed to the reaction D* + DCl → D2 + Cl of hot atoms from DCl photodissociation.
Interaction of 25 keV Electrons with the Nucleic Acid Bases, Adenine, Thymine, and Uracil. II. Inner Shell Excitation and Inelastic Scattering Cross Sections
Authors: Isaacson Michael
Published: February 2004

The energy loss spectra of 25 keV electrons traversing thin films of the nucleic acid bases adenine (C5N5H5), thymine (C5N2O2H6), and uracil (C4N2O2H4) have been obtained at room temperature in the region of K-shell excitation (>285 eV), and fine structure near the carbon K edge of these materials has been analyzed. The inelastic scattering cross sections have also been determined for both K-shell and valence shell excitation. Preliminary results on the effect of electron beam damage of these specimens will also be presented.
Calculation of Moment Directions of Electronic Transitions in Nonsymmetrical Amino-Anthracenes
Authors: Jo/rgensen Poul
Published: February 2004

Moment directions of electronic transitions have been calculated with the CI and the TDHF approximations for 1-, 2- and 9-amino-anthracene. Comparison with the experimental values shows that the CI and especially the TDHF approximation are able to describe these directions satisfactorily.
Single-Crystal Broad-Line 59Co and 55Mn NMR in CoMn(CO)9
Authors: Mooberry E. S. , Sheline R. K.
Published: February 2004

The 59Co and 55Mn NMR was studied in a single crystal and solution of CoMn(CO)9. Two pairs of independent crystallographic sites were found related by the twofold axis and the mirror plane of the monoclinic crystal. The z axes of the 59Co and 55Mn electric-field-gradient tensors were found to be coaxial. The 59Co quadrupole coupling parameters were determined to be (1) e2qQ/h=129.15 MHz, η=0.1558 and (2) e2qQ/h=128.44 MHz, η=0.0937. The z component of the chemical shift was found to be identical with that for the compounds X3MCo(CO)4 (M is Si, Ge, Sn, and Pb; X is Cl, Br, I, C6H5) which have near C3ν symmetry. The 55Mn quadrupole coupling parameters were determined as (1) e2qQ/h= ∼ 20 MHz, η undetermined and (2) e2qQ/h=19.940 MHz, η=0.004. The z component of the chemical shift was found to be identical with that for the manganese pentacarbonyl halides which have approximate C4ν symmetry. The structure of CoMn(CO)9 has not been determined by x-ray crystallography as it always forms twin crystals, but the quadrupole coupling and chemical shift give evidence that there is threefold symmetry at the 59Co site and fourfold symmetry at the 55Mn site. Because the z axes of the electric-field-gradient tensors at the 55Mn and 59Co site are coaxial, they are assumed to lie along the Co–Mn bond. Information about the packing of the molecules in the crystal is therefore obtained. The bonding in CoMn(CO)9 was compared to the compounds Mn(CO)5MX3 and Co(CO)4MX3. The electrons forming the Co–Mn bond were found to be unequally shared by the two metal atoms with Co having the larger MO coefficient.
Thermodynamics of Hydrogen-Isotope-Exchange Reactions. I. Electrochemistry in Dimethylformamide
Authors: Silvester Leonard F. , Kim Janice J. , Rock Peter A.
Published: February 2004

The paper reports our results for the direct experimental determination of the equilibrium constants for the hydrogen-isotope-exchange reaction, D2(g)+2HCl(DMF)=H2(g)+2DCl(DMF), where DMF is the solvent N,N-dimethylformamide. The reaction was studied in electrochemical double cells without liquid junction of the type, (Pt)D2(g) | DCl(DMF) | TlCl(s) | Tl(Hg) | TlCl(s) | HCl(DMF) | H2(g)(Pt).The experimentally determined values of E0(296.6oK) for this cell are Eion0=7.64± 0.38 mV and Eneut0=8.12± 0.54 mV, where Eion0 refers to strong electrolyte standard states for HCl(DMF) and DCl(DMF), and Eneut0 refers to undissociated solute standard states for HCl(DMF) and DCl(DMF). The corresponding experimental values of the equilibrium constants are Kion=1.82± 0.05 and Kneut=1.89± 0.08 (296.6oK). The experimental values of the equilibrium constants are compared with values for K calculated from statistical thermodynamic theory for model reactions.
Random Walk Model of Interstitial Thermal Diffusion in Crystals
Authors: Weeks John D. , Shuler Kurt E.
Published: February 2004

We have developed a random walk model of interstitial diffusion of light impurity atoms in a host lattice of heavy atoms in the presence of a thermal gradient. To take account of the effect of the thermal gradient on the flux of impurity atoms we introduce a bias in the jump direction of the interstitial impurity. We assume that this bias is due to the temperature dependence of the excluded volume effects which arise during the jump of the impurity atom between interstitial sites. The resulting random walk equation for thermal diffusion is consistent with both positive and negative heats of transport in agreement with experimental data. Using a cell model approach and the assumption of local equilibrium, we then develop equations which permit the calculation of the bias in jump direction. The theory of interstitial diffusion developed here clarifies and supports the classic Wirtz model for interstitial thermal diffusion.
Three-Body Dipole and Quadrupole Interactions in Neon and Argon
Authors: Fowler Ronald , Graben H. W.
Published: February 2004

Contributions from three-body dipole and quadrupole interactions to the third virial coefficients of neon and argon and to the cohesive energy of solid argon are evaluated. In both cases it is found that the triple-dipole term dominates the nonadditive effect while the dipole—dipole—quadrupole, dipole—quadrupole—quadrupole, and triple-quadrupole terms are of successively decreasing importance.