bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyperfine Structure Constants of HF and DF
Authors: Muenter J. S. , Klemperer William
Published: February 2004

The radio frequency spectrum of HF and DF is measured by the molecular-beam electric resonance method. The measurements are in the lowest vibrational state (υ = 0) and first rotational state (J = 1). The constants obtained are: HFDFμ (D)1.826526 (7)1.818805 (5)CF (kHz)307.637 (20)158.356 (45)CH (kHz)− 71.128 (24)− 5.755 (19)SHF (kHz)28.675 (5)4.434 (9)JHF (kHz)0.529 (23)(eqQ) D354.238 (78) The electron coupled spin–spin interaction, JHF = + 530 Hz.
Test of the Monte Carlo Method: Fast Simulation of a Small Ising Lattice
Authors: Friedberg R. , Cameron J. E.
Published: February 2004

A very fast stochastic procedure is used to generate samples of configurations of a 4 × 4 periodic Ising lattice in zero field. Running on the IBM 7094, we require only 15 μsec to process each site (cf. Yang who required 300 μsec on the 7090) and hence we generate 4000 completely new configurations each second. Our main results are based on samples of 106 configurations at each of 10 temperatures; we also took samples of 107 configurations at three temperatures. The 4 × 4 lattice can be solved exactly without much difficulty. Hence our data give information about the Monte Carlo method itself, especially its rate of convergence. We define the statistical inefficiency (SI) in a variable as the limiting ratio of the observed variance of its long-term averages to their expected (Gaussian) variance. (Thus, if the SI is 3, then averages of the variable taken over Monte Carlo runs of three million configurations will be as accurate as averages over one million configurations drawn randomly from the true ensemble. The SI accounts for correlations between configurations closely following one another in the Monte Carlo run.) We find that for this lattice the SI in energy never exceeds 12, and that its maximum occurs slightly above the temperature which is critical for the infinite lattice. We confirm earlier statements that the influence of the initial configuration is lost very quickly, except when two phases coexist.
Some Ion–Molecule Reactions of H3+ and the Proton Affinity of H2
Authors: Burt J. A. , Dunn J. L. , McEwan M. J. , Sutton M. M. , Roche A. E. , Schiff H. I.
Published: February 2004

The flowing afterglow technique has been used to study the reactions of H3+ with a number of neutral reactants at thermal energies. Proton transfer was the only primary reaction observed with N2, CO, CO2, N2O, NO, CH4, C2H2, H2O, and NH3. Both proton transfer and dissociative charge transfer were observed with C2H4 and C2H6, while dissociative charge transfer is the exclusive primary process with NO2. Secondary reactions were observed with NO, C2H6, C2H4, and C2H2. Cluster ions were formed between NO+ and NO2 and H2O, between H3O+ and H2O, CO2, and CO, and between NH4+ and NH3 and H2O. Proton transfer was also observed between HN2+ and CO2, N2O, CH4, and H2O, and between HO2+ and H2 and N2. Rate constants were obtained for these reactions and are discussed. Limits could be placed on the proton affinity (P.A.) of H2 from the failure to observe rapid proton transfer to O2 and the observation of proton transfer to N2. These indicate 4.2 < P.A. (H2)< 4.7 eV with a recommended value of 4.4 eV. The technique can be used to measure relative proton affinities of gases.
Double Excitation in the Infrared Spectra of Self-Associated Alcohols
Authors: Asselin M. , Sandorfy C.
Published: February 2004

At liquid-nitrogen temperature, in glassy matrices, self-associated alcohols exhibit two bands in the region of the first overtone of the OH stretching vibration. The one of lower frequency is shown to be the overtone, and the one of higher frequency a band due to simultaneous excitation by one quantum in two OH groups linked by hydrogen bonding.
Theoretical Investigations of Gas–Solid Interaction Phenomena. IV Spatial and Velocity Distributions
Authors: Lorenzen J. , Raff L. M.
Published: February 2004

A study of the spatial and final velocity distributions for gaseous particles reflected from a solid surface is reported. The three-dimensional classical model previously used by the authors is employed to study the scattering distributions as functions of the incident particle velocity, the velocity distribution in the incident beam, and surface temperature. The broadness of the spatial scattering distributions is predicted to decrease with increasing incident velocity. The spatial distribution peak position is specular for large incident velocity, shifts toward the surface for intermediate velocity, and approaches the surface normal for small incident velocity. The model indicates that the spatial distribution dependence upon initial velocity causes velocity-selected and thermal beams to give similar spatial scattering. For hot surfaces the spatial scattering is indicated to be a rather insensitive function of surface temperature. The velocity distributions of reflected particles are predicted to be non-Maxwellian, bimodal for large incident velocities, and clearly different for velocity-selected and thermal incident beams. The results indicate that final velocity distribution measurements may be the most informative characteristic of gas–solid interaction phenomena.
Magnetic Shielding of 19F in XeF4
Authors: Hindermann D. K. , Falconer W. E.
Published: February 2004

The second moment of the 19F nuclear magnetic resonance of XeF4 has been measured as a function of temperature and of magnetic field both in the rigid lattice and above a motional transition. A completely general shielding tensor was determined indicating that the previous assumption of axial symmetry about the Xe–F bonds was an oversimplification. The out-of-plane component σx was determined uniquely to be 0 ± 8 × 10−6, referred to the bare 19F nucleus. Complementary pairs of values for the in-plane shielding were found to be σy(σz) = 394 ± 25 × 10−6and σz(σy) = 261 ± 25 × 10−6. As for XeF2, the field-independent rigid-lattice second moment is larger than that calculated from the average atom positions.
Constructing Wavefunctions for Nonlocal Potentials
Authors: Gordon Roy G.
Published: February 2004

A method is developed for constructing wavefunctions for nonlocal interaction potentials of the type that arise in the theory of chemical reactions, electron scattering by molecules, and also in nuclear scattering problems. The nonlocal potential is approximated by piecewise polynomial functions, for which analytic solutions are constructed. Accurate and efficient algorithms are derived for evaluating all the special functions needed for the solutions. The method is particularly advantageous for heavy-particle scattering at higher energies.
Experimental Study of Reaction Kinetics by Light Scattering. II. Helix–Coil Transition of the Copolymer Deoxyadenylate–Deoxythymidylate (dAT)
Authors: Yeh Yin
Published: February 2004

The average rate of configuration transition of the (dAT) copolymer has been determined by the study of the spectrum of light scattering. For the alkaline transition of (dAT) at 18.7°C, pH = 11.0, and ionic strength of 0.1M Na+, we find a rate τR−1 = 2.33 ± 0.21 × 103sec−1. This compares favorably with previous measurements obtained by the temperature-jump technique. Simultaneously, we have measured the linear diffusion coefficient within the transition region to be D = 2.91 ± 0.14 × 10−8cm2/sec. There is a 6%–10% variation of the diffusion rates between the samples at the low-pH (10.4) helical conformation and at the high-pH(11.6) random coil conformation.
Monte Carlo Study of the Thermodynamics of Electrolyte Solutions
Authors: Card D. N. , Valleau J. P.
Published: February 2004

Monte Carlo techniques have been used to study the primitive model of an ionic solution. The parameters chosen correspond to a simple 1:1 electrolyte dissolved in water at 25°C. Data are derived for the pair distribution functions, excess internal energy and heat capacity, osmotic coefficient, and mean activity coefficient, in the range 0.01–2M. The results are compared with a nonlinear form of the Debye–Hückel theory and with integral equation results in the Percus–Yevick and hypernetted chain approximations. The last appears to be excellent up to 1M.
New Approach to Electronic Structure Calculations for Diatomic Molecules: Application to F2 and Cl2
Authors: Schaefer Henry F.
Published: February 2004

A new method is described for the calculation of diatomic molecule wavefunctions. Two-center molecular orbitals (MO's) are used directly, and all integrals are evaluated by strictly numerical means. By avoiding the use of analytic basis functions, the calculation of accurate configuration interaction (CI) wavefunctions requires the computation of a vastly smaller number of molecular integrals. Using this approach it is possible to compute MO CI wavefunctions which are exactly equivalent to complete, high accuracy valence bond (VB) wavefunctions. Other ways of using the present approach to compute wavefunctions of beyond molecular Hartree–Fock (HF) accuracy are discussed. For the F2 molecule, using accurate (within 0.00001 hartree of the exact HF energy) HF atomic orbitals, complete valence bond wavefunctions are computed for nine internuclear separations, and a dissociation energy of 0.32 eV is obtained. Experimental values of the F2 dissociation energy range between 1.39 and 1.86 eV. Similarly, high accuracy VB wavefunctions were obtained for Cl2, yielding a dissociation energy to 0.71 eV, to be compared with the experimental value 2.48 eV. For F2 more complicated CI wavefunctions, starting from HFAO's, were computed. These wavefunctions added additional d or p functions on each center and included up to 318 configurations and 1438 distinct determinants. The calculations yielded total energies substantially below those previously obtained for the F2 molecule. However, the largest calculated value of De for F2 was 0.80 eV. We conclude that it is very difficult to obtain a quantitative ab initio dissociation energy for F2 starting from symmetry MO's which are linear combinations of HFAO's.
Ultrasonic Absorption Properties of Tetra-n-butylammonium and Tetraethylammonium Bromides in Water at 298.15°K; Comparison with the Trends Required by the Thermodynamic Properties
Authors: Blandamer M. J. , Waddington D.
Published: February 2004

The Romanov–Solovyev treatment of the ultrasonic absorption of liquid systems is applied to aqueous solutions of two tetra-alkylammonium salts. Published thermodynamic data for these two alkylammonium salts in water are used in an examination of the dependence on salt concentration of the ultrasonic absorption at fixed frequency and temperature. The theory predicts that the absorption for tetra-n-butylammonium bromide is larger than that for tetraethylammonium bromide and increases rapidly when the concentration exceeds 0.8 mole dm−3. Both predictions agree with observed trends, and the results are examined in terms of the thermodynamic parameters which control the ultrasonic absorption.
Pulse Radiolysis Studies. XVIII. Spectrum of the Solvated Electron in the Systems Ethylenediamine–Water and Ammonia–Water
Authors: Dye James L. , DeBacker Marc G. , Dorfman Leon M.
Published: February 2004

The pulse radiolysis technique with fast infrared detection was used to determine the optical absorption spectrum of the solvated electron in the systems ethylenediamine–water and ammonia–water. These spectra, determined over the entire concentration range, show the following: In ammonia and in ethylenedamine, the bands at 1550 and 1350 nm, respectively, have the same shape and position as those attributed to the solvated electron in alkali metal solutions. In each of the two-component systems a single band is seen with the peak position intermediate to those in the pure solvents. For ethylenediamine–water mixtures, the band shape (normalized) and half-width (energy scale) are invariant with composition, while for ammonia–water mixtures the ratio of the peak position to the half-width is invariant. These observations suggest a delocalized electron with optical characteristics determined by the aggregate properties of the solvent. Models which require that the optical properties be strongly influenced by solvation with a small number of solvent molecules are not in accord with these observations. Kinetic data indicate that the decay of the solvated electron in ammonia and in ethylenediamine is a complex process. The rate constant for the reaction of the solvated electron in ammonia with ammonium ion was found to be at least four orders of magnitude lower than the diffusion-controlled limit.
Excited States of Neutral Molecular Fragments from Appearance Potentials by Electron Impact in a Mass Spectrometer
Authors: Lewis David , Hamill William H.
Published: February 2004

Appearance potentials (A.P.) and ionization efficiency (I.E.) curves have been measured by the retarding potential difference technique for processes of the type AD+ / ABCD where the products at onset are a molecular ion AD+ and a stable molecule BC. The structure in the linear segmented I.E. curves has been correlated with the structure in the I.E. curves for AD+ / AD and the electronic energy levels of the neutral molecule BC. The method provides a means to measure the energy separation between the ground-state singlet and the first excited state of the molecule BC, assumed to be triplet. Singlet–triplet separations have been measured for H2O at 4.4 eV; C2H6 at 2.4 eV; C2H4 at 3.25 eV; cyclopentene at 3.1 eV; and n-C6H14 at 2.8 eV.
Theory of Dielectric Relaxation in Polar Liquids
Authors: Nee Tsu-Wei , Zwanzig Robert
Published: February 2004

The theory of dielectric relaxation in a model polar liquid is developed and applied to experimental data. The model is a spherical Onsager cavity, with a uniform dielectric background described by the high frequency limit ε∞ and containing a permanent point dipole. The dipole moment undergoes rotational Brownian motion in the cavity. Dielectric friction on the rotating dipole is taken into account and leads to a frequency-dependent relaxation time. Earlier theoretical results, obtained first by Klug, Kranbuehl, and Vaughn and by Fatuzzo and Mason, are rederived. When the rotational Brownian motion is spherically isotropic, approximate Debye relaxation is found. When the rotational Brownian motion of the dipole is restricted to a constant angle with respect to some fixed axis, approximate Davidson–Cole relaxation is found. Experimental data on glycerol and i-amylbromide are analyzed this way.
Hydrogen Chloride Vibrational Populations Produced by the H and D Atom Reactions with SCl2 and S2Cl2
Authors: Johnson R. L. , Perona M. J. , Setser D. W.
Published: February 2004

Infrared emission intensities from HCl and DCl products in high vibrational levels have been used to measure energy partitioning in the reactions of H and D atoms with SCl2 and S2Cl2. The results are compared to the infrared chemiluminescence from the H and D atom reactions with Cl2. The relative vibrational level populations were measured under experimental conditions such that vibrational relaxation was minimized. The H atom reactions with SCl2 and S2Cl2 partitioned >37% and >36% of the available energy into vibrational energy of the hydrogen chloride product. Within our experimental error the fraction of energy partitioned to vibration was the same for the H and D atom reactions. In the reactions of H and D with SCl2 and S2Cl2 the distribution of rate constants for formation of HCl† and DCl† into the vibrational levels apparently peaks at levels intermediate between υ = 0 and the maximum possible level of vibrational excitation. The distributions are similar to those from the H and D atom reactions with Cl2. The additional internal degrees of freedom in S2Cl2 relative to SCl2 did not greatly affect the partitioning of energy to the HCl† product.
Theory of Charge Carrier Transport in Aromatic Hydrocarbon Crystals
Authors: Munn R. W. , Siebrand W.
Published: February 2004

Evidence is presented that the dominant electron–phonon coupling in aromatic hydrocarbons is quadratic in molecular out-of-plane vibrational coordinates. A linear-chain model based on this interaction, previously treated in the hopping transport limit, is extended to the coherent transport limit. Both limits are also studied for a model with two oscillators per lattice site. Hopping transport varies little with the number of oscillators, but coherent transport decreases approximately as the square of this number. Carrier mobilities in three-dimensional lattices comprise contributions from mobilities along nearest-neighbor directions. The model calculations and literature values of intermolecular electronic couplings are used to determine the dominant contributions to carrier drift mobilities in anthracene self-consistently from the experimental data. Transport of electrons in the c′ direction by hopping accounts for the observed magnitude, temperature dependence, and deuterium effect. The other diagonal mobility components for electrons and holes can be attributed to transport which is either coherent or intermediate between coherent and hopping transport in the slow-phonon limit. The off-diagonal mobility components μac′ at 300°K are predicted to be 0.2 cm2V−1·sec−1 for both electrons and holes. By allowing different modes of transport to contribute to the same mobilities the model proves superior to previous ones, which fail to account for the anisotropy and the temperature dependence of all the carrier mobility components in anthracene.
Magnetic Properties of Polyatomic Molecules. II. Proton Magnetic Shielding Constants in H2O, NH3, CH4, and CH3F
Authors: Arrighini G. P. , Maestro M. , Moccia R.
Published: February 2004

Proton magnetic shielding constants in H2O, NH3, CH4, and CH3F molecules have been evaluated by the perturbed HF scheme, by employing extended basis sets of Slater orbitals. Explicit formulas for both diamagnetic and paramagnetic contributions to the observable are given, for a gauge transformation corresponding to any change of the origin of the external vector potential. The calculated results are in fairly good agreement with the experimental data, when the chosen gauge is coincident with the central nucleus of the molecule.
Specific Excitation of N2 (C3πu) and Specific Ionization by 4.3-MeV α Particles
Authors: Tatischeff I.
Published: February 2004

In this paper, specific excitation, dN* / dx (the number of excited molecules per millimeter) is compared with specific ionization, dN + /dx (the number of ions created per millimeter) along the track of 4.3-MeV α particles in nitrogen at atmospheric pressure. The knowledge of the ratio of the collisional to the radiative rate constants allows one to calculate the specific excitation from measurements of specific luminescence. In this way, the specific excitation and specific ionization at atmospheric pressure have been calculated from measurements of specific luminescence and ionization at eight pressures ranging from 23–253 torr. It is assumed that the comparison along the entire track concerns ionization and excitation leading to the state C 3πu. The excitation is found to be nearly proportional to the ionization along most of the α track. Beyond the average range of the α particles, however, excitation seems to become much more likely than ionization. This could be simply the result of a higher efficiency for excitation, compared with ionization, when the secondary electrons are formed with lower velocities. In addition, it may partly result from the appearance of another type of excitation of N2 ( C3πu), namely excitation by He+ ions.
Temperature and Pressure Dependence of Phosphorescence Lifetimes in PMMA
Authors: Rodriguez Silvio , Offen Henry
Published: February 2004

The phosphosescence lifetimes of 1,2,5,6-dibenzanthracene and triphenylene have been measured in polymethylmethacrylate as a function of temperature (77–360°K) at 1 atm and 30 kbar. Two temperature regimes with different activation energies are discernible for both compounds. Matrix compression has negligible influence on the ∼200-cm−1 activation energy below room temperature, but diminishes the larger activation energy (1500–4500 cm−1) above room temperature by 20%–25% at 30 kbar. The pressure data suggest that diffusional quenching is not responsible for the thermally activated process(es).
Complete Partial-Wave Treatment of Compound-State (Rotational Excitation) Resonances in Subthreshold Scattering of an Atom by a Diatomic Molecule
Authors: Muckerman J. T. , Bernstein R. B.
Published: February 2004

The present study deals with quantitative prediction of compound-state resonance energies and widths in the elastic scattering of a diatomic molecule at energies below the threshold for rotational excitation. Previous work had been restricted to the weak interchannel coupling limit or to s-wave scattering only (but with no restriction on coupling strength). The two-state adiabatic decoupling approximation, adequate to describe the s-wave resonance phenomenon, requires modification to be practical for higher partial waves. This extension is carried out and calculations yield good agreement with exact (close-coupled) results. It is then used in the numerical solution of the complete subthreshold resonance problem for an example involving moderately strong coupling, for which other approximate methods are inadequate. This decoupling approximation, which yields accurate energies and semiquantitative lifetimes of the compound states, leads also to a spectroscopic correlation scheme, i.e., an indexing of the spectrum of resonances.
Classical Scattering Theory. Elastic Collisions
Authors: Miles J. R. N. , Dahler J. S.
Published: February 2004

The methods of Prigogine and Resibois are used to construct a description of classical two-body scattering events which bears a close formal analogy to that of time-dependent quantum-scattering theory. It is shown how the distribution in phase space evolves after long times into a steady-state scattering form, from which expressions for cross sections and transition rates are obtained by means similar to those of the quantum-mechanical treatment. These expressions are shown to be equivalent to the conventional classical formulas but offer in principle alternative means of evaluation.
Multiplet and Phonon Structure in Mixed Crystal Spectra: Anthracene in p-Terphenyl
Authors: Small Gerald J.
Published: February 2004

The origin and molecular vibronic bands in the absorption and fluorescence spectra of anthracene-h10 and -d10 dissolved in p-terphenyl exhibit a multiplet structure consisting of several components with a maximum multiplet splitting of about 250 cm−1. The phonon structure originating from the multiplet component origins is very different and the spectral phonon shapes consist of sharp peaks (bandwidths ∼1 cm−1) superimposed on a broad band. A theory of electron–phonon coupling is presented which suggests that the sharp phonon bands are due to pseudolocalized phonon modes and the broad bands due to delocalized phonon modes.
Far-Infrared Spectra of Gaseous and Liquid SF6
Authors: Rosenberg A. , Birnbaum G.
Published: February 2004

The far-infrared absorption spectrum of SF6 in the gaseous state was measured at 25°C at pressures from 3 to 19 atm in the wavelength region 12–250 cm−1. The absorption of liquid SF6 in this region was measured at 0°C and −40°C. The strongest bands in the gas phase are centered roughly at 50 cm−1, and approximately at 94 and 173 cm−1. Bands centered at approximately 55, 90, and 150 cm−1 were observed in the liquid phase. Since the intensity of the band at 50 cm−1 varies as density squared, it is ascribed to collision induction. The bands at 94 and 173 cm−1 in the gas phase (considered to be the same bands at 90 and 150 cm−1 in the liquid phase) vary linearly with density and are ascribed to the difference vibrations, respectively, ν4 − ν5 and ν5 − ν6. The hexadecapole moment of SF6 was estimated from the integrated intensity of the collision-induced band in the gas.
Viscosities of the Inert Gases at High Temperatures
Authors: Dawe R. A. , Smith E. B.
Published: February 2004

The viscosities of the inert gases and nitrogen have been determined over the temperature range 300–1600°K. The results suggest that earlier measurements are in error by as much as 6% at 1600°K. The extent to which the new results may lead to a revision of the functions commonly used to represent the intermolecular energy of simple molecules is discussed.
Diffusion and Heterogeneous Reaction. XII. Measurements of O–O2 Diffusion as a Function of Temperature
Authors: Yolles Robert S. , McCulley Leonard , Wise Henry
Published: February 2004

Steady-state and time-transient measurements of the decay of oxygen atoms in a cylinder with catalytic walls have been used to determine the diffusion coefficient of atomic oxygen in molecular oxygen over the temperature range 298–873°K. The resulting temperature dependence of the O–O2 diffusion coefficient was fitted to a modified Buckingham potential with ε / k = 16°K, α = 15, and rm = 4.99 Å. Measurements of the surface reaction rate of oxygen atoms on quartz gave a value for the recombination coefficient γ = 1.70 × 10−4 with little variation in temperature over the range studied.
Analysis of the Heat Conductivity Data for Polar and Nonpolar Gases Using Thermal Transpiration Measurements
Authors: Gupta A. Das , Storvick T. S.
Published: February 2004

Thermal transpiration experiments for carbon monoxide, nitric oxide, sulfur dioxide, and hydrogen sulfide at 366, 398, and 444°K are reported. The “dusty gas” model proposed by Mason, Evans, and Watson describes the variation of the thermomolecular pressure difference as a function of the mean pressure for each temperature. The thermal transpiration measurements for each gas were used to analyze the heat conductivity data for each gas. It appears that nonresonant rotational energy exchange must be included in the kinetic theory representation of the polar gas heat conductivities. The rotational collision numbers deduced from the thermal transpiration measurements are found to increase with increasing temperature. The recent model of the thermal transpiration effect developed by Loyalka reproduces these collision numbers and the temperature dependences.
Positronium and Iodine Reactions in Organic Solvents
Authors: Tao S. J.
Published: February 2004

The quenching of o-Ps by iodine in various organic solvents is investigated. It is found that iodine acts as both a chemical quenching agent and a Ps formation inhibitor. The reaction between Ps and iodine is diffusion controlled. The annihilation lifetime of the formed Ps iodine compound (PsI2 or PsI) is estimated to be 0.4 nsec. The inhibition coefficient is calculated to be 20 mole−1 for iodine in hydrocarbon solvents and 5.0 mole−1 in oxyhydrocarbon solvents. After an investigation the high Ps quenching rates in iodine solutions cannot all be attributed to high values of the diffusion coefficient. The interaction between Ps and iodine must also be taken into consideration. Obviously, the formation of the charge-transfer complex of iodine plays an important role here.
Structure, Vibrational Spectra, Dipole Moment, and Stability of Gaseous LiCN and LiNC
Authors: Bak B. , Clementi E. , Kortzeborn R. N.
Published: February 2004

An ab initio Hartree–Fock calculation of the structure of gaseous LiCN and LiNC has been performed using a basis set of 84 uncontracted and 45 contracted Gaussian atomic functions. The calculated Li–C distance is 3.6317 a.u.; the calculated C–N distance is 2.1915 a.u. for linear LiCN. For linear LiNC the calculated Li–N distance is 3.3354 a.u.; the calculated N–C distance is 2.1857 a.u. No experimental gas-phase data have been reported, but the calculated C–N and N–C distances agree well with experimental C≡N bond lengths in other molecules. The calculated linear stretching mode frequencies are ν1 ≈ 2375, ν2 ≈ 670 cm−1 (6Li12C14N), and ν1 ≈ 2367, ν2 ≈ 785 cm−1 (6Li14N12C), agreeing with ν1 ≈ 2250 cm−1 for other molecules. For linear 6Li14N12C, a bending mode frequency of ≈ 250 cm−1 was calculated. The predicted dipole moment is very high (3–4 a.u.). A marginal energy difference of 0.0141 a.u. between LiCN and LiNC was found, LiNC being the more stable.
Raman Spectra of the Crystalline Methyl Halides
Authors: Brown Chris W. , Lippincott Ellis R.
Published: February 2004

The laser-excited Raman spectra of polycrystalline CH3Cl, CH3Br, and CH3I have been measured and compared with previous infrared and Raman data. The Raman spectra are used to support certain controversial assignments of the infrared active bands and to provide additional information on the effect of the crystal field on the vibrational bands. Due to the naturally occurring isotopes of chlorine and bromine the bands assigned to the C–X stretching vibrations in the spectra of these halides are more complex than the band in the spectrum of CH3I. A model is proposed to account for the unusual contours of these bands.
Photoelectron Spectra of Ethylene and Ethylene-d4
Authors: Branton G. R. , Frost D. C. , Makita T. , McDowell C. A. , Stenhouse I. A.
Published: February 2004

The photoelectron spectra of ethylene and ethylene-d4 have been measured using a new high-resolution spectrometer and the 584-Å helium resonance line as a light source. Five ionization potentials have been observed for each compound. Vibrational structure associated with the transitions leading to the first and fourth ionization potentials has been resolved, and it has been possible to assign the corresponding vibrational modes. The photoelectron spectrum of neon, obtained with the 537-Å line from the same light source, is also presented.
Single-Crystal Paramagnetic Resonance Studies of V(II), Mn(II), and Ni(II) in CsMgCl3 and the Crystal Structure of CsMgCl3
Authors: McPherson G. L. , Kistenmacher T. J. , Stucky G. D.
Published: February 2004

The single-crystal electron spin resonance spectra of (VII), Mn(II), and Ni(II) are reported in the diamagnetic lattice CsMgCl3 at 298 and 77°K. The structure of the host lattice CsMgCl3 is also reported. The crystal system is hexagonal, space group P63/m mc. The basic structural feature is the linear array of [MgCl6]4− octahedra sharing faces directed along the hexagonal c axis. The crystallographic site symmetry at the Mg2+ ions is D3d. The spin resonance spectra of the doped salts Cs[Mg1−x, Vx]Cl3, Cs[Mg1−x, Mnx]Cl3, and Cs[Mg1−x, Nix]Cl3, where x is small, can be readily explained in terms of the axial field Hamiltonian: H = β[g‖HzSz + g⊥(HxSx + HySy)] + D[Sz2 − 13S(S + 1)] + ASzIz + B(SxIx + SyIy). The principal measured quantities are, respectively: V(II)(77°K), g‖ = 1.9740, g⊥ = 1.9760, D(gauss) = 931, A(gauss) = 82.3, B(gauss) = 79.8; Mn(II)(77°K), g‖ = 2.0016, g⊥ = 2.0015, D(gauss) = 313, A(gauss) = 86.5, B(gauss) = 86.5; Ni(II)(77°K), g‖ = 2.257, g⊥ = 2.241, D(gauss) = 18 980.
Electronic States of Heavily Doped Molecular Crystals—Naphthalene. I. Theoretical
Authors: Hong Hwei-Kwan , Robinson G. Wilse
Published: February 2004

The energy spectrum of heavily doped molecular crystals was treated in the Green's function formulation. The mixed-crystal Green's function was obtained by averaging over all possible impurity distributions. The resulting Green's function, which takes the form of an infinite perturbation expansion, was further approximated by a closed form suitable for numerical calculations. The density-of-states functions and optical spectra for binary mixtures of normal naphthalene and deuterated naphthalene were calculated using the pure-crystal density-of-states functions. The results showed that when the trap depth is large two separate energy bands persist, but when the trap depth is small only a single band exists. Furthermore, in the former case it was found that the intensities of the outer Davydov bands are enhanced whereas the inner bands are weakened. Comparisons with previous theoretical calculations and experimental results are also made.
Optical Spectra of Ru4+ in Single Crystals of K2PtCl6 and Cs2ZrCl6 at 4.2°K
Authors: Patterson Howard H. , Dorain Paul B.
Published: February 2004

The optical absorption spectra of Ru4+(4d4) has been studied at 4.2°K in single crystals of K2PtCl6 and Cs2ZrCl6. Eight electronic transitions have been observed which have a similar appearance to the spectra of OS4+(5d4) except that the vibrational structure is not as well resolved. An intermediate-coupling crystalfield analysis for a d4 configuration fits the observed electronic transitions with the parameters B = 803 cm−1, C = 1363 cm−1, Dq = 1892 cm−1, and λ4d = 1044 cm−1. The rms deviation of the energies is 262 cm−1. The observed absorptions are assigned on the basis of calculated transition probabilities and energy level diagrams. The relative linewidths are in qualitative agreement with the calculated results for a small tetragonal distortion of the cubic field. The molar susceptibility which is calculated from the optical data is in agreement with the experimental magnetic susceptibility. The calculated g values are tabulated for all the assigned electronic states. A discussion of several unassigned transitions with E > 26 000 cm−1 is given.
Low-Temperature Studies. IV. The Phase Transitions of Ammonium Sulfate and Ammonium-d4 Sulfate; the Nature of Hydrogen Bonding and the Reorientation of the NX4+ Ions
Authors: Schutte C. J. H. , Heyns A. M.
Published: February 2004

The temperature dependence of the infrared spectra of (NH4)2SO4 and (ND4)2SO4 between 17 and 298°K has been accurately determined. An analysis of the spectra of the high-temperature and ferroelectric phases of (NH4)2SO4 supports the evidence of the neutron-diffraction data of Schlemper and Hamilton that there is an increase in hydrogen bonding below 223°K. From the temperature variation of the peak heights of certain bands it is shown that graphs of this type can be used to determine the presence of any phase transitions accurately. Inflection points of these curves of (NH4)2SO4 at ∼ 160°K are correlated with the NMR linewidth transition at 163°K; it is the first time that such a correlation has been established. The temperature dependence of ND4+ stretching bands indicates the possible existence of three phases in (ND4)2SO4 (transition temperatures 225°K and ∼ 223°K). The torsional mode of the NH4+ ions has been identified; there is no evidence that the ion rotates “freely” at any temperature.
Infrared Spectrum of Cyanogen Azide
Authors: Shurvell H. F. , Hyslop D. W.
Published: February 2004

The infrared spectrum of cyanogen azide (N3CN) has been recorded in the gas phase between 3000 and 70 cm−1. The nine vibrational fundamentals have been located. Assignments of the seven in-plane and two out-of-plane fundamentals have been made on the basis of observed and calculated vibration–rotation band contours. Two strong Fermi doublets have been observed in the triple bond stretching region of the spectrum. Valence force constants have been calculated for the in-plane vibrations of cyanogen azide, and the distribution of potential energy among the force constants obtained, in order to give qualitative descriptions of the normal modes. Thermodynamic quantities of cyanogen azide have been calculated for several temperatures and compared with corresponding quantities for methyl azide.
Binary Diffusion in Dense Gases to 1360 atm by the Chromatographic Peak-Broadening Method
Authors: Balenovic Zdravko , Myers Marcus N. , Giddings J. Calvin
Published: February 2004

The chromatographic peak-broadening method for measuring diffusion coefficients is applied to 11 binary gas pairs at pressures in the range 272–1360 atm. Operation is in the nonequilibrium mode, where it is shown that the small diffusive displacements characteristic of dense systems can be magnified to an arbitrary level, thereby increasing speed and accuracy. Since comparable data are not available, an attempt is made to estimate the level of accuracy; a 5% error is judged most probable. The results are compared with the Enskog–Thorne equation for binary diffusion in dense gases. The deviations become considerable at the higher pressures. When the trace species is larger than the carrier species, diffusivity exceeds the Enskog–Thorne value and, in a few cases, exceeds the ideal-gas value. The opposite result is found for small trace species. These results are consistent with an explanation based on velocity correlations, the nature of which changes drastically with the relative size and thermal momentum of the trace and carrier species.
Radiative Linewidths and Lifetimes from the Phenomenological Maxwell Equation
Authors: Fulton Robert L.
Published: February 2004

The propagation of the electromagnetic field in the presence of N interacting molecules which are fixed in space is considered. It is shown that radiative linewidths and radiative lifetimes are given by the classical phenomenological Maxwell equation in spite of the fact that the susceptibilities entering the equation are to be evaluated in the absence of the transverse radiation field. The linewidths and lifetimes are in agreement with quantal calculations.
Models for Competitive Cooperative Linear Adsorption. The Amylose–Iodine–Iodide Complex
Authors: Rawlings P. K. , Schneider F. W.
Published: February 2004

Cooperative competitive adsorption of two different types of monomer species on a one-dimensional lattice composed of identical sites is solved exactly for any chain length by the use of the matrix method (Model A). It is assumed that the adsorbed species mutually interact with each other by first nearest-neighbor interactions. Detailed general matrix operators are given for the well-known case of identical monomer molecules adsorbing to a polymer composed of two different kinds of sites (Model B). Matrix operators for a third and more complex model are presented: two different types of monomer species adsorbing on two types of adsorption sites (Model C). As an experimental example the binding of iodine and triiodide to helical amylose is treated according to Model A for the first time. Satisfactory agreement between our experimental data and this theoretical model is obtained.
Solution of the Poisson–Boltzmann Equation about a Cylindrical Particle
Authors: Philip J. R. , Wooding R. A.
Published: February 2004

An analytical approximation is developed to the solution of the Poisson–Boltzmann equation about a charged cylindrical particle in an electrolyte solution. A symmetrical electrolyte is treated specifically, but the method applies also to nonsymmetrical ones. The analysis preserves the mathematical character of the exact problem and (as is shown by comparison with machine solutions) yields results with errors which are for most purposes negligibly small. The complete solution involves five separate cases depending on the value of limR→∞[Ψ / K0(R)], where R is the radial coordinate and Ψ the electrostatic potential, both in dimensionless form. In two cases the singularity in Ψ is at R = 0, and the Debye–Hückel solution is a uniformly valid, though quantitatively poor, approximation. In the other three cases the (physically relevant) singularity is away from the origin. Similar singular behavior would account for the limited success of iterative and regular perturbation schemes for the solution about the sphere.
Negative-Ion–Neutral Reactions in N2O
Authors: Paulson John F.
Published: February 2004

A double mass spectrometer system has been used to study the reactions O−+N2O→NO−+NO, O−+N2O→O2−+N2, and NO−+N2O→N2O−+NO over the range of reactant ion energies from 0.3 eV to about 35 eV. Using 18O−+N2O, both N16O− and N18O− are formed with approximately equal probability. However, little or no 16O appears in the N2O− product when NO− reacts with N218O. The dependence of the cross section for production of O2− from O−+N2O upon O− kinetic energy indicates that the reaction is endothermic.
LCAO–MO–SCF Calculations Using Gaussian Basis Functions. V. BH2−
Authors: Sachs Lester M. , Geller Murray , Kaufman Joyce J.
Published: February 2004

This article reports the results of an intensive LCAO–MO–SCF investigation of the negative ion BH2−. The geometry of the (1A1) BH2− molecule was determined to a high precision relative to the exact minimum for the basis set and SCF wavefunctions used; the central angle was found to be 102° and the equilibrium B–H bond length 2.3507 bohr. Even within the Hartree–Fock Roothaan approximation BH2− has a fourth bound orbital. A Walsh diagram of orbital energies vs H–B–H angle is presented, and the discrepancies with Walsh's original prediction are discussed. The potential curves of BH2− as a function of angle and distance both indicate it to be a stable species.
ESR Study of the Ozonide Ion in γ-Irradiated Sodium Bromate
Authors: Cosgrove M. M. , Collins M. A.
Published: February 2004

The identification of a paramagnetic center in γ-irradiated sodium bromate crystals as the ozonide ion, O3−, is confirmed. At ambient temperatures the principal values of the axially symmetric g tensor are found to be g‖ = 2.0035 ± 0.0001 and g⊥ = 2.0220 ± 0.0001, whereas at 77°K, g‖ = 2.0028 ± 0.0001 and g⊥ = 2.0242 ± 0.0001. If the O3− ion is a bent molecule of bond angle 110 ± 5° the electron spin resonance data suggests that the O3− ion is undergoing rapid motion at ambient temperatures and that the rate of motion is reduced at 77°K. Because no bromine-containing radical is characterized after the ambient temperature irradiation of sodium bromate, the electron spin resonance results suggest a radiolytic decomposition differing from that of the alkaline-earth bromates, in which the paramagnetic species BrO2 is postulated.
Gaussian Basis Set for Molecular Wavefunctions Containing Third-Row Atoms
Authors: Wachters A. J. H.
Published: February 2004

A Gaussian basis set consisting of 14s-type, 9p-type, and 5d-type functions has been optimized for the third-row atoms up to Zn. Energy values are reported for different contractions of this basis set.
SCF MO's and Molecular Properties of H2O
Authors: Arrighini G. P. , Guidotti C. , Salvetti O.
Published: February 2004

SCF MO's of H2O molecule have been calculated for a geometry very close to the experimental one, using a basis set of 29 STO's. The evaluated HF energy is −76.0384 a.u. Several ground-state one-electron properties have also been computed, viz., the first three electric multipole moments, electric field and gradient field at the nuclei, electric polarizability, and magnetic susceptibility.
Glass-Forming Composition Regions and Glass Transition Temperatures for Aqueous Electrolyte Solutions
Authors: Angell C. A. , Sare E. J.
Published: February 2004

As a first stage in a study of the low-temperature-region behavior of aqueous solutions, the composition regions of a large number of binary salt-water systems in which macroscopic samples can be obtained in the vitreous state have been determined. The glass transition temperatures Tg within these regions have also been measured. Correlations of the magnitude of Tg at a given composition with the formal charge on the cation (for salts with a common anion) and with the viscosity “B” coefficient of the anion (for salts with a common cation) are presented. In addition, an important correlation is found with the basicity of the anion which is interpreted in terms of the bonding of anions to the protons of the water molecules in the cationic hydration sheath. Thermodynamic relations for the composition dependence of Tg are presented. From the breaks in the otherwise monotonic composition dependence of Tg in the chloride systems, the existence of low temperature liquid–liquid immiscibility regions is proposed and is utilized in discussion of “total” hydration numbers. The Tg for pure water, obtained by extrapolation of the data, is found to be in agreement with the value obtained for vapor-deposited vitreous ice but to be incompatible with the value predicted from thermodynamic data; an interpretation in terms of different short-range order possibilities for water molecules is offered.
Electron Ejection from Triplet State in Fluid Solutions
Authors: Houser Nathan , Jarnagin R. C.
Published: February 2004

The triplet state of tetramethylparaphenylenediamine (TMPD) dissolved at 10−5M in aliphatic hydrocarbons was photoionized with light of photon energy ≤3.86 eV at room temperature. A combination of transient photocurrent measurements, transient absorption measurements, and temperature effects permitted evaluation of the pertinent kinetic parameters. A representative thermalization range of the low-energy photoejected electron was estimated to be 180 Å and the absorption coefficient connecting triplet to continuum between 320–410 nm was estimated as 1 × 10−18 cm2.
Molecular Collisions. XI
Authors: Curtiss C. F.
Published: February 2004

The development of Paper VIII of the series is continued to obtain equations and expressions suitable for the numerical evaluation of the cross sections for rotational excitation in collisions of rigid diatomic molecules interacting through an arbitrary soft potential. Explicit equations which describe collisions between an atom and a diatomic molecule are also given. An approximate solution of the equations is discussed.
Rate of Some Hydroxyl Radical Reactions
Authors: Breen J. E. , Glass G. P.
Published: February 2004

The rates of the following reactions of the hydroxyl radical have been measured in a fast flow system using ESR detection: OH+OH→H2O+O, OH+O→H+O2, OH→wall. The rate constants obtained were k1 = 8.4 ± 2.6 × 10−13cm3molecule−1·sec−1, k2 = 4.3 ± 1.3 × 10−11cm3molecule−1·sec−1, and k3 = 124 ± 40 sec−1. The rates of the first two reactions are compared with previous measurements. Earlier investigators have not included the third reaction in their mechanisms. In all experiments, the hydroxyl radicals were generated by means of the titration reaction H + NO2→OH + NO.
Spectroscopic Study of the Chemiluminescent Reaction O + CCO
Authors: Bayes Kyle D.
Published: February 2004

Further spectroscopic studies of the chemiluminescence from oxygen atom–acetylene and oxygen atom–carbon suboxide flames are reported. The reaction18O + CC16O→C18O + C16O results in the emission of Fourth Positive bands by both C18O and C16O with comparable intensities, suggesting that the intermediate OCCO exists for at least several vibrations. Some bands in the d 3Δ→X 1Σ+ system are identified. Partially resolved rotational structure of the Fourth Positive bands show irregular intensities which are interpreted as strong emission from perturbed rotational levels. It is concluded that the reaction forming excited CO in hydrocarbon flames populates the A 1Π, d 3Δ, e 3Σ−, I 1Σ−, and a′ 3Σ+ states of CO at comparable rates. Possible reactions of the metastable CO molecules are suggested.
Theoretical Investigations of Gas–Solid Interaction Phenomena. III. Adsorbed Particles and Lattice Impurities
Authors: Lorenzen J. , Raff L. M.
Published: February 2004

A study of the interaction of gaseous particles with contaminated surfaces is reported. An extension of the three-dimensional classical model previously used by the authors to study gas–solid interactions at clean surfaces is employed. The surface is assumed to consist of nine movable lattice atoms and one or two movable adsorbed particles. Morse potential functions are assumed to exist between the incident gaseous atom and each of the movable surface atoms while Lennard-Jones (12–6) potentials operate between the adparticles and the lattice. Numerical solution of the Hamiltonian equations that describe He interacting with Ar absorbed on a Ni lattice (He/Ar/Ni) yields energy-transfer coefficients and spatial distributions of reflected atoms. The energy-transfer coefficient (ETC) is found to reach a maximum at a half-monolayer of adatom coverage due to changes in surface roughness. The ETC is also found to increase with decreasing adatom mass and adatom–lattice binding energy. It is a strong but irregular function of the surface particle vibration phases. The spatial distributions show a maximum amount of backscatter and out-of-plane intensity for half-monolayer coverage. A study of He scattered from an Ni surface containing oxygen impurity atoms indicates that quasispecular scattering is possible in such cases. The results of the model are qualitative due to an inadequate number of surface atoms, a lack of knowledge about the nature of the surfaces, and uncertain interaction potential parameters.