bluuebunny/crossref_metadata_2025 huggingface dataset:
Space-charge effects in proustite (Ag3AsS3)
Authors: Byer Harold H. , Bobb Lloyd C.
Published: February 2004

A series of capacitance and dissipation factor (tanδ) measurements were made on single-crystal specimens of synthetic proustite (Ag3AsS3). The results showed a rise in the dielectric constant (∼3000) with increasing temperature as well as with decreasing frequency (dispersion effects). A model based on an equivalent-circuit analog of a two-layer dielectric was used to fit theoretical curves to the data. In this model, one layer is considered to be the space-charge region, while the other is the crystal bulk. The theoretical and experimental curves show the same general features, although some quantitative differences exist. The true dielectric constant is concluded to be ε′∥c = 22.
Structure of electroplated and vapor-deposited copper films. III. Recrystallization and grain growth
Authors: Gangulee A.
Published: February 2004

Changes in the structure of electroplated and vapor-deposited copper thin films, as a result of isothermal and isochronal annealing in the temperature range 100–500 °C, have been investigated by x-ray diffraction and metallographic techniques. In the electroplated films, recrystallization occurred with an activation energy of about 0.65 eV until the recrystallized grains attained sizes comparable to the film thickness. In vapor-deposited films, such recrystallization is believed to take place immediately after deposition on heated substrates. Grain growth in both sets of copper films proceeded with an activation energy of about 1.55 eV, until a limiting grain size was reached. This limiting grain size is shown to be dependent on the film thickness and the extent of texture present.
Relation between elastic-constant tensors of hexagonal and cubic structures
Authors: Fuller E. R. , Weston W. F.
Published: February 2004

The third-order elastic constants of hexagonal and cubic structures are related using an extension of a transformation derived by Martin. The transformation is used to calculate the zinc-blende second- and third-order elastic constants of CdS from the experimental wurtzite elastic constants. Also, the transformation is shown to give good results for some face-centered-cubic hexagonal closed-packed polymorphic metals. In particular, the second-order elastic constants of cobalt and thallium in the hexagonal structure are compared with those calculated from cubic elastic constants extrapolated from alloy data, and second- and third-order hexagonal elastic constants of Co-32% Ni are compared with those calculated from cubic elastic constants.
Electronic states of Mn ions in Ba0.97Sr0.03TiO3 single crystals
Authors: Nakahara Motohiro , Murakami Toshiaki
Published: February 2004

The electronic states of Mn ions in barium titanate have been studied on Mn-doped and Mn, Gd-codoped Ba0.97Sr0.03TiO3 single crystals, using ESR and optical absorption techniques. It was found from ESR measurements that Mn ions substitute at the B sites and exist as Mn2+ in reduced crystals and Gd-doped crystals, and as Mn3+ in fully oxidized crystals. Optical measurements indicated that the energy levels of Mn2+ and Mn3+ are above and below the Fermi level, respectively. Moreover, resistivity measurements showed that the conductivities of the specimens are associated with the difference between their concentration of Gd and Mn ions. These results indicate that, when donors are increased by reduction or doping of Gd3+, Mn3+ ions trap the donor electrons to change into Mn2+.
X-ray structure of a pinched plasma in a vacuum spark
Authors: Welch T. J. , Clothiaux E. J.
Published: February 2004

The size and shape of an x-ray source formed by a plasma pinch have been determined using time-integrated pinhole photography. Pinhole diameters as small as 4 μ have been used to image a source whose length is usually about one order of magnitude larger than this pinhole diameter. Such measurements should refine the density determination of the source and are essential to specifying a charged-particle acceleration mechanism in the pinch region. The x-ray images, visible streak photographs, and x-ray-source lifetime measurements suggest that the x-ray source may, as a whole, be moving as it emits.
Effect of temperature on shock-wave propagation in Cu–Zn alloys
Authors: Mitchell A. C. , van Thiel M. , Coleburn N. L. , Forbes J. W.
Published: February 2004

Several different types of brass have been shock compressed to 0.5 and 1. Mbar pressures. The effect of temperature on the Hugoniot points was checked and found to agree with Grüeisen theory.
Recombination processes in highly excited CdS
Authors: Fischer T. , Bille J.
Published: February 2004

Experimental results on the spontaneous and stimulated emission of CdS are presented in the temperature range from liquid-helium temperature to room temperature under electron-beam excitation. At temperatures below 100 K, the dominating laser process results from the exciton-exciton interaction. In addition, lasing on the first and second phonon replica of the A1 exciton has been observed. At temperatures above 100 K, the laser emission is found to shift to lower energies much stronger than that of the band gap. This shift can quantitatively be accounted for by the exciton-electron interaction process.
Transient photoinjection of electrons from amorphous selenium into trinitrofluorenone
Authors: Emerald R. L. , Mort J.
Published: February 2004

The photoinjection of electrons from a sensitizing layer of amorphous selenium into thin films of trinitrofluorenone (TNF) has been studied using the xerographic discharge technique. Discharge curves were observed for both the amorphous and crystalline state of TNF. Large changes in discharge characteristics observed for the two states of the material are correlated with changes in electron transport. The effective mobility determined from the xerographic measurements for the amorphous TNF structure is field dependent and has a value of 6×10−5 cm2/V sec at 4×105 V/cm. This value is consistent with those obtained using the conventional time-of-flight measurement technique. A lower limit of electron mobility in polycrystalline TNF may be inferred from these measurements.
cw generation of tunable narrow-band far-infrared radiation
Authors: Aggarwal R. L. , Lax B. , Fetterman H. R. , Tannenwald P. E. , Clifton B. J.
Published: February 2004

Tunable narrow-band cw generation of far-infrared radiation has been achieved for the first time in the 70-μm to 1-mm wavelength region by noncollinear difference-frequency mixing of two single-mode CO2 lasers in GaAs at 80 K. Using a Schottky diode as a heterodyne harmonic mixer with a carcinotron local oscillator, the far-infrared signal is shown to have a linewidth of less than 100 kHz and a fine tuning capability in excess of 50 MHz.
Preparation and properties of submicron hexagonal FexN, 2<x<3
Authors: Bouchard R. J. , Frederick C. G. , Johnson V.
Published: February 2004

Hexagonal ε-FexN phases with 2.02<x<2.85 were prepared from finely divided carbonyl Fe and NH3/H2 mixtures at 350 °C. Both the Curie temperature and magnetic moment decrease with increasing nitrogen content and approach zero at ∼Fe2N, the limiting composition of the hexagonal phase. The coercive force was reasonably high (>200 Oe) for those phases with Tc above room temperature. The variation of the magnetic moment with composition is nonlinear.
Second-order elastic constants of high-purity vitreous silica
Authors: Fritz I. J. , Graham R. A.
Published: February 2004

Ultrasonic measurements of the longitudinal and shear moduli of a high-purity vitreous silica, GE151, are reported for comparison with longitudinal modulus values determined from elastic-impact experiments. Characterization of this material is important for a direct comparison of elastic constants determined in elastic-impact and second-harmonic-generation experiments. Good agreement is found between the ultrasonic and impact experiments. The shear modulus of GE151 is reported for the first time. The present values differ from similar measurements recently reported in ultrasonic second-harmonic-generation experiments on this material.
Calculation of the Effect of Non-Brownian Motion on Some dc Transport Coefficients in Solution
Authors: Friedman Harold L. , Ben-Naim Arieh
Published: February 2004

Effects of non-Brownian motion on transport coefficients are found on the basis of a model in which the carrier undergoes random changes of state between two states of different mobility. The transport properties investigated are the electrical mobility, the Hall mobility, and the Onsager slope of the equivalent conductance. On the basis of these examples the relations among certain transport coefficients may be expected to be quite sensitive to the microscopic dynamics of the carrier.
Magnetic Circular Dichroism of Benzene, Triphenylene, and Coronene
Authors: Stephens P. J. , Schatz P. N. , Ritchie A. B. , McCaffery A. J.
Published: February 2004

The magnetic circular dichroism of benzene, triphenylene, and coronene in regions of π→π absorption (20 000-45 000 cm−1) are reported. The data support the conventional molecular-orbital assignments of the absorption spectra. The lowest E′1 and E1u1 states of triphenylene and coronene, respectively, are shown to be little affected by Jahn-Teller perturbations. Magnetic moments are obtained for these states which are in good agreement with values calculated from the free-electron network model and from molecular-orbital wavefunctions if Löwdin orthogonalized atomic basis functions are employed.
Free Ion 4fn Levels of the Tetravalent Lanthanides. Fluorescence and Absorption Spectra of Cesium Dysprosium (IV) Heptafluoride
Authors: Varga Louis P. , Asprey Larned B.
Published: February 2004

When a mixture of chloride or sulfate salts of cesium and dysprosium in a 3:1 mole ratio was treated with fluorine gas at 10-60 psig and 200°-350°C, the white Dy(III) starting material was converted to an orange compound with an empirical formula approaching Cs3DyF7. Fluorescence and infrared absorption spectra of fluorocarbon mulls of the orange fluorination product, measured at liquid nitrogen temperature, were compared with experimental and literature values of the energy levels for the 4f8Tb (III) and the 4f9Dy (III). All of the components of the 7F ground-state multiplet for the 4f8Dy (IV) were identified as was the D45 resonance fluorescence level. The 4f energy levels of Dy(IV) were higher than those of the isoelectronic Tb(III) as would be expected from the less effective screening of the nuclear charge. Using the free-ion approximation, the 4fn energy levels were calculated by diagonalization of the energy matrices with the adjustment of two parameters, the coulomb integral F2 and the spin-orbit coupling constant ζ, until reasonable agreement was obtained with the experimental Dy(IV) levels. By interpolation, the parameters F2 and ζ for the largely unexplored Nd(IV) and Tb(IV) systems were estimated and the corresponding 4fn levels calculated.
Vibration→Vibration and Vibration→Translation Energy Transfer in Methane-Oxygen Mixtures
Authors: Yardley James T. , Moore C. Bradley
Published: February 2004

A laser-excited infrared fluorescence technique has been used to study vibration-to-vibration energy transfer from O2 to CH4 and to study vibration-to-translation relaxation in O2–CH4 mixtures. It is found that 440 ± 40 O2–CH4 collisions are necessary to transfer one quantum of vibrational excitation from O2 to CH4. Measurements of vibrational relaxation in NO–CH4 systems are also given.
Order-Disorder Phenomena. VI. Anomalous Changes in the Volume of Ammonium Chloride
Authors: Garland Carl W. , Young Robert A.
Published: February 2004

A compressible Ising model is used to show that the anomalous changes in the molar volume V due to ordering are essentially identical in character with the anomalous changes in the elastic constant c44. Indeed, the variations in V and c44 are both determined by the behavior of the configurational energy. Experimental data on NH4Cl are used to demonstrate this equivalence near the lambda point at 1 atm and at high pressures.
Near-Infrared Fluorescence and Absorption Spectra of Co2+ and Ni2+ in MgO
Authors: Ralph J. E. , Townsend M. G.
Published: February 2004

The electron-beam excited fluorescence spectra of Co2+ and Ni2+ in single crystals of MgO have been recorded at 77° and 4.2°K. For Co2+ the observed transitions occur from the E(t62e) and T24(t4e3) excited terms to the T14(t5e2) ground terms, and for Ni2+ from the Ti3(t5e3) to the A23(t6e2) terms. Comparison of the fluorescence spectra with the appropriate absorption spectra enables an unambiguous indentification of the zero-phonon magnetic-dipole transitions from spin-orbit levels of the excited terms to the ground spin-orbit level for both Co2+ and Ni2+. The splitting of these transitions is discussed. The lattice vibrational sidebands of the Co2+ and Ni2+ fluorescence and absorption spectra may be analyzed in terms of the same two or three phonon modes.
Determination of Centrifugal-Distortion Coefficients of Asymmetric-Top Molecules. II. Dreizler, Dendl, and Rudolph's Results
Authors: Watson James K. G.
Published: February 2004

Dreizler, Dendl, and Rudolph used the method of least squares to fit the equation of Kivelson and Wilson, which gives the rotational energy levels of an asymmetric top with first-order corrections for centrifugal distortion, to the observed rotational spectra of dimethyl sulfoxide and dimethyl sulfide. The normal equations obtained were found to be highly ill-conditioned, so that the centrifugal coefficients, A1to A6, were essentially indeterminate. It is shown here that the form of this indeterminacy can be understood quantitatively on the basis of a previously published linear relation between the average values in Kivelson and Wilson's equation. Explicit expressions are presented for the first-order centrifugal corrections to those energy levels that are given by linear or quadratic equations. These expressions suggest that there are no further linear relations of the above type.
LCAO-SCF Computations for Ethylene
Authors: Kaldor U. , Shavitt I.
Published: February 2004

A series of LCAO-SCF calculations with a minimal Slater basis set were carried out for the ethylene molecule and for its positive and negative monovalent ions in a number of electronic states. These computations, which included configurational mixing of the two low 1A states, were performed for seven values of the twist angle between the two CH2 groups, from 0° to 90°. For planar ethylene four singlet levels, two triplets, and two doublets of each of the ions, were investigated. The two Ag1 states, the triplets, and the ionic doublets were individually computed (with open-shell SCF procedures where applicable), while their energies, as well as those of the other singlets, were also derived from the data of the closed-shell calculations. This individual SCF optimization was found to have only limited effect in the case of the neutral molecule, but was more significant for the ions. The energy obtained for the planar ground state, though lower than that of a 40-function Gaussian calculation, is considerably higher than the energies reported for basis sets of 60 Gaussians or of 66 Gaussian lobe functions. The effect of the neglect of σ − π exchange was examined in a series of calculations for planar ethylene (including the ions). It was found that the errors introduced by this approximation are roughly proportional to the number of π electrons in each state, and are quite significant for the determination of energy differences involving changes in the number of these electrons. The assignment of the so-called olefin mystery band is considered, and we favor the opinion that this band correlates with the ethylene Rydberg singlet transition at 7.11 eV, with the corresponding upper level probably having some valence-shell π→CH* character. The twisting potential curves are obtained for four neutral and four ionic states. The ionic levels are degenerate in perpendicular configuration, and show a Jahn-Teller splitting at that point. Similar behavior should be expected of the Rydberg π→ns states.
Spin-Lattice Relaxation in Dilute Gases. II. 19F Relaxation in CF4 and SiF4
Authors: Armstrong R. L. , Tward E.
Published: February 2004

Fluorine spin-lattice relaxation times have been measured in gaseous CF4 and SiF4 as a function of temperature and pressure in the dilute gas region. The observed temperature dependence is consistent with that expected for relaxation dominated by a spin-rotation interaction. Effective cross sections for the transfer of angular momentum to molecular rotation during collisions are deduced. It is found that between one and three binary collisions are sufficient to randomize the molecular rotational angular momentum of these molecules in the temperature range studied.
Chemistry of Detonations. II. Buffered Equilibria
Authors: Kamlet Mortimer J. , Ablard J. E.
Published: February 2004

At low loading densities, values of N, M, and Q calculated from the H2O–CO2 “arbitrary” show poor individual agreement with estimates of these quantities from the RUBY computer code. Nevertheless, when substituted into the equation P = 15.58 NM1 / 2Q1 / 2ρ02 they lead to detonation pressures which correspond closely to RUBY predictions. That incorrect input information should yield results which are very nearly “correct” is rationalized on the basis that the equilibria whose shifting engenders the changes in N, M, and Q are “buffered” in the sense that “errors” in N are offset by compensating “errors” in M and Q. As a consequence of the fact that most of the important equilibria in the detonation of C–H–N–O explosives are buffered, calculated (and actual) mechanical properties of detonations appear to be extremely insensitive to exact product compositions. A number of other interesting consequences of these buffered equilibria are discussed.
Improved Quantum Theory of Many-Electron Systems. III. The GF Method
Authors: Goddard William A.
Published: February 2004

A general method of calculating accurate and useful many-electron wavefunctions for atoms and molecules has previously been described. This general method besides achieving lower energies than do the Hartree-Fock and unrestricted Hartree-Fock methods still yields an independent particle interpretation of the many-electron wavefunction, correctly describes dissociation of molecules and solids, and can be used on systems of any total spin. There are several possible approaches for the general method; here we concentrate on one of these, GF method, which is equivalent to optimizing the orbitals in the unrestricted Hartree-Fock method after spin projection rather than before. The detailed equations (the GF equations), for the GF method are derived here for all values of total spin and number of particles.
Oscillatory Kinetics in the Electrochemical Oxidation of Formate and Ethylene
Authors: Wojtowicz J. , Marincic N. , Conway B. E.
Published: February 2004

A number of electrocatalytic anodic oxidations of simple organic substances exhibit periodic effects in their kinetics. The anodic oxidation of formate and of ethylene has been studied at Pt and Pd under potentiostatic and constant-current conditions and the oscillatory behavior observed has been related to (a) mass transport effects; (b) coverage of the electrode by electrochemically formed surface-oxide species. In the formate case, the oscillations are associated with activation-controlled processes and are not eliminated by high-speed rotation of the electrode; in the case of ethylene, diffusion control is shown to play an important role. Kinetic conditions are examined for several mechanisms of formate oxidation; for certain circumstances, an autocatalytic surface-oxide removal step is consistent with the conditions required for oscillatory kinetics to arise. Such a process is supported by experimental observations on the periodic changes of oxide coverage which arise during the oscillatory behavior. For ethylene oxidation a more intuitive approach is employed in which it is shown that only imaginary solutions for the “steady-state” reaction flux can arise under certain conditions of adsorption and mass transfer in the partly diffusion-controlled reaction.
F− Vacancy Conductivity in BaF2 Crystals
Authors: Barsis E. , Taylor A.
Published: February 2004

The ionic conductivity of the system BaF2–BaO has been measured over a wide range of temperature in order to deduce the value for the energy of motion of the F– vacancy in BaF2 crystals. Using the strong electrolyte Debye-Huckel theory to account for association effects between the oxygen and the mobile vacancy, we obtained the value of μT = 6.4 × 102exp(−0.56 ± 0.03 / kT) cm2V−1·sec−1 for the F− vacancy mobility, and 0.56 ± 0.04 for the association energy between the oxygen and the vacancy. The solubility of oxygen in BaF2 is equivalent to a free carrier concentration equal to 12 exp (−0.68 / kT) mole fraction.
Trees Correction Matrices for d5 Configuration in Cubic Symmetry
Authors: Mehra Anjani K.
Published: February 2004

A method is given for finding the matrix elements of Trees correction term in cubic symmetry in the strong-field scheme. The correction matrices have been calculated for d5 configuration for which this term has been found quite significant.
Fluorescence Spectra of the Excited Ion N2+ Resulting from Vaccum-Ultraviolet Photon Impact on N2
Authors: Judge D. L. , Weissler G. L.
Published: February 2004

The spectrum of the radiation between 3500 and 6500 Å, resulting from the impact of monochromatic vacuum-ultraviolet radiation on N2, is obtained for incident-photon energies between 18.8 (661 Å) and 26.8 eV (460 Å), and the vibrational progressions and sequences of the first negative system of nitrogen, N2+(B 2Σu+→X 2Σg+) are identified. For incident photon energies less than 18.8 eV no significant radiation was observed. From an intensity measurement of the bands of the first negative system, experimental Franck–Condon factors for the transitions N2[X 1Σg+(υ″ = 0)]→N2+[B 2Σu+(υ′ = 0, 1)] and N2+[B 2Σu+(υ′ = 0, 1)]→N2+[X 2Σg+(υ″ = 0, 1, 2)] were obtained and found to agree reasonably well with theoretical values, calculated using Morse potentials. In addition, the absolute ionization cross section vs incident photon energy for the ionic state N2+[B 2Σu+(υ′ = 0)] is presented for the above indicated range of incident photon energies. The lower energy of 18.8 eV is the threshold energy for excitation to this ionic state. An observed quenching at N2 pressures above 100 μ may arise from excitation transfer in ion–molecule reactions, although no spectral changes were observed as a function of gas pressure.
Spontaneous Emission Probabilities and Quantum Efficiencies for Excited States of Pr3+ in LaF3
Authors: Weber M. J.
Published: February 2004

Spontaneous emission probabilities for electric- and magnetic-dipole transitions from several electronic states of Pr3+ in LaF3 are calculated using the Judd–Ofelt theory and experimental intensity parameters. The calculated radiative decay probabilities are combined with observed fluorescence lifetimes to determine the quantum efficiencies of the D21 and P03 states. Although the lifetimes were measured at low temperatures and small Pr concentrations where competing nonradiative decay by multiphonon emission and ion-pair relaxation should be negligible, the predicted quantum efficiencies are less than unity. The radiative lifetimes obtained via the Einstein relations and measured integrated absorption and relative fluorescence intensities agree, however, with the observed lifetimes. The discrepancies appear to arise from approximations and possible limitations inherent in the approach used to calculate the radiative transition probabilities. Matrix elements of U(λ) for states of 4f2 in intermediate coupling are included in an appendix.
Resolution Enhancement of ESR Spectra from Irradiated Single Crystals of Glycine
Authors: Hedberg A. , Ehrenberg A.
Published: February 2004

The electron spin resonance spectrum of +H3NĊHCOO− in single crystals of glycine γ irradiated at room temperature has been re-examined at X band and evaluated by resolution-enhancement technique. The resolution enhancement is obtained by reducing the linewidth by a factor of maximum 0.55 at the expense of the signal-to-noise ratio. The calculations, which require a high-speed digital computer, consist of three steps: (1) transformation of the experimental spectrum to a complex Fourier plane, (2) multiplication of this Fourier spectrum with a suitable linewidth-reduction function, and (3) inverse transformation back to the real plane. From the obtained constants, the hyperfine coupling tensors have been calculated, including contributions from second-order effects (ΔMI = ± 1). One of the principal values of one of the tensors was appreciably affected by these second-order effects. The results fully confirm the structure of the radical.
Anomalous Emission from Substituted Hafner's Hydrocarbons
Authors: Dhingra R. C. , Poole J. A.
Published: February 2004

The emissive behavior of substituted, pericondensed, nonalternant Hafner's hydrocarbons has been investigated in fluid solution at room temperature. The compounds investigated showed fluorescence from electronic states other than the first excited singlet.
Semiclassical Theory of Inelastic Scattering: An Infinite-Order Distorted-Wave Approximation
Authors: Cross R. J.
Published: February 2004

A previously derived semiclassical theory of inelastic scattering is generalized to include collisions where the trajectory is nonlinear. Schrödinger's equation is expressed as an infinite-order perturbation series using the radial wavefunctions corresponding to the spherically symmetric part of the potential as the unperturbed solution. In the classical limit this series simplifies, and the scattering matrix is obtained by exponentiating a phase shift matrix which is obtained as a simple integral over the classical trajectory corresponding to the spherically symmetric part of the potential. A second-order term is obtained to correct for the deviation from this trajectory.
Rydberg Absorption Series and Ionization Energies of the Oxygen Molecule. I
Authors: Yoshino K. , Tanaka Y.
Published: February 2004

Rydberg absorption series of O2 have been investigated with a 6.6-m normal-incidence vacuum spectrograph in the first and second orders in the 600–750-Å region. Previous observations have been improved upon, and it has been possible to obtain much more accurate ionization energies for the b 4Σg− and B 2Σg− states of O2+. The data are compared with recent results obtained in the investigation of the electron energy spectrum of photoionized O2+. Another Rydberg series converging to the B 2Σg− state has been observed and is now reported for the first time.
Solid Fluorine and Solid Chlorine: Crystal Structures and Intermolecular Forces
Authors: Nyburg S. C.
Published: February 2004

Extended Hückel molecular-orbital (EHMO) calculations and molecular multipole sums are compared for various assemblies of Cl2 molecules. It is shown that the multipole sums does not predict the correct space group for Cl2 but that the EHMO calculation does, if there is d-orbital involvement. Some comments are made on the crystal structures of α- and of β-F2, both different from those of the other halogens.
Method of Diatomics-in-Molecules. VIII. Excited Triplet States of H3+
Authors: Wu Ay-ju A. , Ellison Frank O.
Published: February 2004

It is possible to construct 18 triplet-state functions for nonlinear H3+ which are antisymmetric with respect to the molecular plane and which belong to electron configurations like 1sA2pπB. The set reduces to A13″ + 3A2″ + 23E″ for equilateral triangles, 33A2 + 33B1 for isosceles triangles, or one component of each of 3 3Πg + 3 3Πu for linear symmetrical H3+. Diatomics-in-molecules theory is used to compute the potential energy surfaces for these states. None appear to be stable or metastable.
Nanosecond-Pulse Radiolysis of Aniline
Authors: Cooper R. , Thomas J. K.
Published: February 2004

The nanosecond-pulse radiolysis of pure aniline reveals two transient species absorbing at 3850 Å and 10 500 Å or higher. Each transient shows a rapid initial first-order decay (t1/2 = 62.5 ± 1.5 nsec) and a long-lived (tens of microseconds) decay. In the presence of electron scavengers, the long-wavelength transient is removed, and yields of the negative ions of biphenyl and pyrene are observed with plateau yields of G = 0.95 ± 0.05. At high concentrations of biphenyl or pyrene, the decay characteristics of the negative ions are identical with those of the species in pure aniline at 3850 Å. Scavenging studies using both positive and negative ion scavengers show that the two transients present in pure aniline are the solvent positive ion (3850 Å) and the solvated electron (10 500 Å) in aniline. The extinction coefficients of φNH2+ and eaniline− determined from ionic scavenging results are 12 050 and 3550 cm2/mole, respectively. The formation of excited states of naphthalene, anthracene, and 1, 2-benzanthracene are observed, and the results clearly show that, where solvent–solute charge-transfer reactions are possible, they lead to the production of ∼20% of the total triplet yields.
Electron Spin Resonance Absorption Spectrum of Y3+-Stabilized CO33− Molecule–Ion in Single-Crystal Calcite
Authors: Marshall S. A. , McMillan J. A. , Serway R. A.
Published: February 2004

An electron spin resonance absorption spectrum of effective spin S = 12 exhibiting two hyperfine structure doublet patterns has been observed in naturally occurring single crystals of calcite. The nuclei responsible for these doublets are identified from electron–nucleus double resonance and relative intensity measurements to be 89Y and 13C. From the mean of the spectroscopic splitting tensor values as well as from the 13C hyperfine structure separations, it is deduced that this spectrum is due to the CO33 − molecule–ion which is charge stabilized by a neighboring Y3+ ion. Experimental data suggest the existence of two sets of six equivalent centers each having an orthorhombic g tensor which is diagonal in a coordinate system whose z axis is canted with respect to the crystal [111] direction. The 89Y and 13C hyperfine tensors exhibit orthorhombic and axial symmetries, respectively, with the z axis of each being parallel to the crystal [111] direction. From an analysis of the 89Y hyperfine structure spectral components, an estimate is obtained for the unpaired electron spin density transferred to the Y3 + ion. This taken together with the 89Y contact term provides an estimate to the hyperfine field of the Y2+ (4d1) ion. Over the temperature range 4.2°-450°K, the 89Y hyperfine splitting increases by about 5% and asymptotically reaches a maximum value at the upper temperature. Attempts to interpret this effect using existing theories on the variation of hyperfine structure with temperature have proven unsatisfactory.
Methyl Alkali Halides: A New Molecular Type; Infrared Spectra by the Matrix Isolation Technique
Authors: Tan Luisa Y. , Pimentel George C.
Published: February 2004

The extent to which the infrared spectrum of methyl in an argon matrix is altered by an alkali halide as nearest neighbor has been investigated. The matrix reaction of sodium atoms with methyl iodide produces a new absorption at 696 cm−1 which shifts to 700 cm−1 when methyl bromide is used and to 680 cm−1 when potassium atoms are used instead of sodium. The evidence indicates that these absorptions, together with the 730-cm−1 feature reported earlier using lithium, are due to a methyl radical interacting strongly with an alkali halide molecule. We believe this interaction is best attributed to a new molecular species, a methyl alkali halide. The nature of the bonding in this molecular type is discussed.
Molecular Beam Kinetics: Reactions of K, Rb, and Cs with Cl2
Authors: Grice R. , Empedocles P. B.
Published: February 2004

Crossed beam studies have been made of the reactions of K, Rb, and Cs atoms with Cl2. These systems are found to exhibit the “stripping” reaction characteristics previously observed for the M + Br2 and I2 systems: (1) the reaction cross sections are very large, ⪞150 Å2; (2) most of the alkali halide product recoils into the forward hemisphere with respect to the incident alkali beam, with scattering angle θ < 60° (in the center-of-mass system). However, there also seems to be substantial intensity (∼5%–15% of the forward peak) throughout the backward hemisphere, 90° < θ < 180°. The sharpness of this forward peaking appears to decrease along the sequence Cl2, Br2, I2 and to be relatively independent of the alkali atom; (3) the angular distribution (in the c.m. system) of alkali atoms scattered without reaction falls off much more rapidly at wide angles than for collisions between unreactive molecules of comparable size. The falloff is most rapid for K + Cl2 and somewhat less rapid for Rb and Cs + Cl2, which are roughly comparable with M + Br2; (4) most of the chemical energy released appears as internal excitation of the products, and other evidence indicates that this is predominantly vibrational excitation of the newly formed bond.
Contributions of Internal Rotation to the Rotational Coefficients in Phenol
Authors: Quade C. R.
Published: February 2004

The theory of internal rotation for molecules with twofold barriers is used to calculate the rotational coefficients for phenol using three possible structures. The difference in coefficients for the substates of the ground torsional state is found to be quite dependent upon the structure of the hydroxyl group. Structural parameters for the hydroxyl group are obtained which are consistent with the observed splittings of the microwave rotational spectra.
Ion–Molecule Reactions of Oxygenated Species. Proton–Transfer Reactions Involving CHO+
Authors: Pritchard Howard , Harrison A. G.
Published: February 2004

The ionic reactions of the major ions in the mass spectra of formaldehyde, acetaldehyde, ethylene oxide, dimethyl ether, vinyl formate, and formaldehyde–D2O mixtures have been studied and rate constants determined for ions of 2.4-eV exit energy. The major reaction involves formation of the protonated molecule. The rate constants for transfer of a proton from CHO+ to a neutral molecule M vary from 1.28 × 10−9 cm3 molecule−1·sec−1 (M = D2O) to 2.7 × 10−9 cm3 molecule−1·sec−1 (M  =  vinyl formate). The rate constants are shown to be in reasonable agreement with theoretical predictions.
Electronic Angular Momentum of Cyclic Aromatic Hydrocarbon Radicals and Ions
Authors: Bishop David M. , Dingle Thomas W.
Published: February 2004

The electronic angular momentum ζe is calculated for the ground-state, π-electronic wavefunctions of C3H3, C5H5, C7H7, C4H4+, C4H4−, C6H6+, and C6H6− on the basis of simple molecular-orbital theory. If the effective nuclear charge of carbon is taken as 3.18 and the carbon-carbon bond distance as 1.40 Å then ζe, in units of h / 2π, is 0.393, 0.755, 1.331, 0.644, 0.644, 0.809, and 1.084 for C3H3, C5H5, C7H7, C4H4+, C4H4−, C6H6+, and C6H6−, respectively. Values of ζe are also given for other values of effective nuclear charge and bond distance.
Anisotropy in the Magnetic Susceptibility and the Molecular Quadrupole Moment of 16O12C32S
Authors: Taft Harrison , Dailey Benjamin P.
Published: February 2004

A high-resolution Zeeman effect microwave spectrometer has been used to determine the anisotropy in the magnetic susceptibility of OCS as χzz − χxx = ( − 8.35 ± 0.28) × 10−6emu. From this data, the individual components of the magnetic susceptibility and the quadrupole moment of OCS have been calculated as χxx = χyy = − 29.6 × 10−6emu; χzz = − 38.0 × 10−6emu and Θ = − 2.10 × 10−26esu·cm2, respectively.
Method of Diatomics in Molecules. VI. BeH2
Authors: Wu Ay-ju A. , Ellison Frank O.
Published: February 2004

Diatomics-in-molecules theory is applied to linear HBeH using as a basis three canonical valence-bond wavefunctions related to the structures k2s2(a − b), k2(s − a) (z − b), and k2(s − b) ( z− a); k, s, z represent 1s, 2s, and 2pz AO's on Be, and a and b represent 1s AO's on the two hydrogens. Theory indicates that the ground Σ1g+ state is best represented by 24.6% of the first structure and equal weights (37.7%) of the second and third structures. The atomization energy (fixed nuclei) is predicted to be 142 kcal and the optimum RBeH = 2.60 bohrs (cf., about 49 kcal and 2.54 bohrs for ground-state BeH). The Σg+ and Σu+ vibrational frequencies for BeH2 are predicted to be 1841 and 1996 cm−1, respectively (cf., 2059 cm−1 for BeH). Potential-energy surfaces for excited Σ1u+ and Σ1g+ states as well as the ground Σ1g+ state are computed.
Interferometric Determination of Near-Critical Isotherms of Xenon in the Earth's Field
Authors: Wilcox L. R. , Balzarini D.
Published: February 2004

Optical measurements which determine the equation of state in xenon near its critical point are described. The method is based upon an analysis of the Fraunhofer interference pattern produced by a thin slab of near-critical fluid in the earth's field. The top of the coexistence curve is rounded, i.e., Guggenheim's relation is uniformly valid as T→Tc to within ε = ΔT / Tc = 5 × 10−6. The coefficient of isothermal compressibility β0 continues to diverge as T→Tc down to at least ε = 5 × 10−6. The rate of divergence, however, is slower than others have found at larger ΔT. If [εPcβ0]−1 = 2(ε / 10−3)0.4 represents the accepted relation, our measured value of β0 at ε = 10−5 is smaller by a factor of five. Supercritical isotherms ΔP(ρ, ΔT) for 5 × 10−6 < ε < 5 × 10−5 have been measured. No departure from Widom's “scaling law” is detected. Further work to sharpen this observation is under way. The purity of our sample has been assumed. Further work to establish the effect of small impurity concentrations is planned.
Monte Carlo Calculations. VI. A Re-evaluation of the RRKM Theory of Unimolecular Reaction Rates
Authors: Bunker Don L. , Pattengill Merle
Published: February 2004

Previously obtained Monte Carlo rate constants for unimolecular decomposition of model molecules [J. Chem. Phys. 40, 1946 (1964)] are compared with the predictions of a modified version of the Rice-Ramsperger-Kassel-Marcus theory. The principal modification is an unambiguous method of specification of the critical value of the reaction coordinate. Anharmonicity corrections are accurately calculated, and an improved way of treating rotational state densities, closely related to that of Marcus [J. Chem. Phys. 43, 2658 (1965)], is used. The agreement between theory and Monte Carlo results is drastically improved; remaining deviations are about  ± 50% for bent molecules and undetectable (within 20%) for linear ones.
Calculation of Extended Hartree-Fock Wavefunctions
Authors: Kaldor Uzi
Published: February 2004

It is shown that an extended Hartree-Fock (EHF) function, obtained by applying a projection operator O to a Hartree product φ with subsequent optimization, has vanishing matrix elements of the operator H-EI with all its singly excited states. A method for obtaining the EHF function using this property is described. Calculations for the Li atom are reported.
Experiments on N2(A 3Σu+). I. Reaction with N
Authors: Young Robert A. , St. John Gilbert A.
Published: February 2004

The Vegard–Kaplan bands from N2(A 3Σu+)υ′ = 0,1 were detected when highly purified, flowing N2 was subjected to a weak Tesla-type discharge. This excited state of N2 was destroyed when nitrogen atoms were added from an upstream microwave discharge. Measurements of the decay time of N2(A 3Σu+), when the Tesla discharge was rapidly extinguished, gave τ−1 = τ0−1 + 5 × 10−11[N], indicating that the reaction N2(A 3Σu +  + N→N2(X 1Σ) + N, was occurring with a rate coefficient of 5 × 10−11 cm3/sec.
Threshold Electron Impact Excitation of Atoms and Molecules: Detection of Triplet and Temporary Negative Ion States
Authors: Compton R. N. , Huebner R. H. , Reinhardt P. W. , Christophorou L. G.
Published: February 2004

A technique which utilizes SF6 as a scavenger of low-energy electrons is employed to study the “threshold” excitation spectra of He, N2, HCl, H2O, D2O and a number of aromatic molecules. For electrons within ∼0.03 eV of threshold, it is found that the probability of exciting the 23S state of helium is approximately 1.5 times larger than that for the 21S state. For HCl all of the optically allowed transitions are observed including a Rydberg series leading to the ionization potential. Temporary negative ion resonances are observed below the first electronic state for all of the aromatic molecules studied. For benzene, in addition to the optically allowed transitions, the first (3.9 eV) and second (4.7 eV) triplet states are detected, while for naphthalene a new intense level at 5.4 eV as well as the lower triplet states are observed.
Near-Infrared Spectrum of Ethane-1,1,1-d3
Authors: Lysne P. C. , Meister A. G.
Published: February 2004

The infrared spectrum of ethane-1,1,1-d3 in the 4600–5100-cm−1 and 5600–6300-cm−1 regions was obtained. Of the eight band centers that were located, only the perpendicular bands ν5 + ν7, at 5065.9 cm−1 and 2ν7, at 5945.5 cm−1, were sufficiently resolved to make a rotational analysis possible. From this analysis it was found that A′(2ν7) = 1.834 cm−1, A′(ν5 + ν7) = 1.787 cm−1, ζ2ντ = −0.264, and ζν5 + ν7 = 0.170. A comparison of the rotational constants of the 2ν7 perpendicular band with likely values for these same constants determined from other bands indicates that the 2ν7 band is strongly perturbed.
Wavefunctions and Correlation Energies for Two-, Three-, and Four-Electron Atoms
Authors: Goddard William A.
Published: February 2004

A recently developed method (the GF method) which is equivalent to optimizing the orbitals of a Slater determinant after spin projection has been applied to H−, He, Li+, Be++, Li, Be+,B++, Li−, Be, B+ and C++. These wavefunctions, which can be given an independent particle interpretation, yield better energies than those of the Hartree-Fock method. For example, H− and Li− are correctly predicted to be stable in contradistinction with the Hartree-Fock results. The new correlation energies are tabulated and compared to the Hartree-Fock values. In the case of the two-electron systems the new wavefunctions are nearly at the radial limit, accounting for 93% to 97% of the radial correlation error present in the Hartree-Fock description.
Polymorphism and Melting of Sodium Cyanide and Thiocyanate to 40 kbar
Authors: Pistorius Carl W. F. T. , Boeyens Jan C. A.
Published: February 2004

The phase diagrams of NaCN and NaSCN were studied to 40 kbar by means of differential thermal analysis. The NaCN orthorhombic/cubic transition line can be expressed as t(°C) = 15.3 + 5.42 P − 0.0426 P2 (P in kilobars). The melting curve of cubic NaCN is very similar to the melting curve of NaCl, and can be fitted by the Simon parameters A = 18.55 kbar, c = 2.224. NaSCN is orthorhombic, space-group Pnma, with a0 = 13.45 Å, b0 = 4.10 Å, c0 = 5.66 Å. It has no polymorphism in the range studied. The melting curve can be fitted by Simon parameters A = 8.808 kbar, c = 6.938.
Dipole Hyperpolarizabilities of S-State Atoms and Ions in the First Two Rows
Authors: Drake G. W. F. , Cohen M.
Published: February 2004

The Z expansion technique for calculating atomic properties has been extended to the calculation of dipole hyperpolarizabilities. The leading two terms are of order Z−10 and Z−11 in the closed-shell case and of order Z−7 and Z−8 in the open-shell case. The corresponding coefficients have been calculated exactly, and also within the uncoupled Hartree-Fock approximation. Numerical results have been obtained for the ground states of the helium, lithium, and beryllium isoelectronic sequences, and for the metastable S1 and S3 states of the helium sequence. Our Hartree-Fock values for the ground states of the helium sequence are in good agreement with those of Langhoff, Lyons, and Hurst. However, the value derived from the leading two terms of the exact Z expansion for neutral helium is about 40% lower, and even for N5+, the discrepancy is still 10%. For the other sequences, the discrepancies are much larger, extending even to the signs of the hyperpolarizabilities of the lithium and beryllium sequences. The polarizabilities of the above sequences are also included for comparison with other data to indicate the rate of convergence of the asymptotic Z expansions.
Thermodynamic Properties of Carbonyl Fluoride from 12°K to Its Boiling Point. The Entropy from Molecular and Spectroscopic Data
Authors: Pace E. L. , Reno M. A.
Published: February 2004

The saturated molar heat capacity of carbonyl fluoride has been measured from 12°K to its normal boiling point, 188.58°K, for a sample of 99.85 mole % purity. The molar heat of fusion was found to be 1603.2 cal/mole at the solid-liquid-vapor equilibrium temperature of 161.89°K. The molar heat of vaporization at the normal boiling point was found to be 4368 cal/mole. The vapor pressure of the solid in the range from 130°K to the triple point of 161.89°K is represented by the equation log10P (mm) = 80.946550 − 3017.1338 / T − 27.311382 log10T. The vapor pressure of liquid from the triple point to the normal boiling point is represented by the equation log10P (mm) = 31.086907 − 1682.1748 / T − 8.4754322 log10T. The standard entropy of carbonyl fluoride gas at the normal boiling point was found to be 57.09 ± 0.14 ca/mole·°K) from the experimental data. A spectroscopic entropy of 57.23 cal/(mole·°K) was calculated by statistical procedures using the moments of inertia: Ia = 42.7928 amu·Å2; Ib = 43.0130 amu·Å2; and Ic = 85.9614 amu·Å2 and the frequency assignment (in cm−1): ν1(A1) = 965; ν2(A1) = 1928; ν3(A1) = 584; ν4(B1) = 1249; ν5(B1) = 626; and ν6(B2) = 774. The agreement between the calorimetric and spectroscopic entropy establishes the fact that there is no residual entropy of randomness in the solid. It is suggested that the high-dipole moment (0.951 D) of the carbonyl fluoride is a factor which influences the ordering of the molecules in the solid.
Raman Intensity Studies on CCl4 in Various Systems
Authors: Bahnick Donald A. , Person Willis B.
Published: February 2004

Solution measurements are presented of the Raman intensity changes occurring in the four fundamental vibrations of CCl4 upon changing from “inert” solvents to ones which can act as electron donors. Donor solvents containing oxygen have little or no effect on the Raman vibrational intensities of CCl4, while significant changes are found in the intensities of ν1, ν3, and ν4 in solutions containing aromatic and amine donors. The nature and magnitude of the observed Raman intensity changes are similar in the latter solutions suggesting that they are caused by a common effect. The observed changes in the intensities of the CCl4 fundamentals are analyzed in terms of changes in bond polarizability parameters. It is concluded that the observed intensity changes are due to specific intermolecular interactions, such as weak charge transfer complex formation.