bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Resolution Analysis of Vibrational—Electronic Circular Dichroism Spectra
Authors: Harnung Sven E. , Ong Edith C. , Weigang Oscar E.
Published: February 2004

Application of the approximations for the Born—Oppenheimer adiabatic wavefunctions, harmonic nuclear motions, and a perturbation of transition moment linear in the normal coordinates lead to general expressions which characterize position, bandwidth, and skewness of absorption and circular dichroism bands of nondegenerate electronic states. Such quantities are particularly useful when the spectra show little or no discernible vibronic structure and define in some cases parameters for a Gaussian description of the spectra. With introduction of additional assumptions which are commonly supposed in vibrational analysis in spectroscopy, the origins of the different terms in the final formulas for the mean frequency, bandwidth, and skewness can be discussed. The expressions obtained relate in a significant way the observed spectra to fundamental constants of the absorbing molecules.
Rate Equations for the Vibrational Relaxation of CO2 – N2 or CO2− Noble Gas Mixtures— Application to Comparison of Spectrophone Data with Results from Other Experimental Techniques
Authors: Huetz-Aubert Magdeleine , Tripodi Robert
Published: February 2004

Macroscopic rate equations are formulated for vibrational relaxation in mixtures of CO2 with either N2 or a noble gas. A model is used that assumes the bending and symmetric-stretching modes of CO2 to be in equilibrium with each other and to have a common vibrational temperature. The asymmetric-stretching mode is taken to be described by a different vibrational temperature, which, in the case of CO2−N2 mixtures, is taken to be common with the temperature of the nitrogen vibrational mode. The rate equations are then derived on a phenomenological basis. The resulting phenomenological coefficients can be interpreted in terms of characteristic relaxation times and energy exchange ratios, which are a measure of the relative amounts of energy exchanged by the different vibrational modes in V—V transitions. The equations can be used for any linearized problem. Here they are applied to a spectrophone. The resulting phase-lag equations are used to reinterpret spectrophone data that had been thought to lead to false conclusions. It is shown that the data is in fact compatible with the results from other experiments. Well done and well interpreted spectrophone experiments can possibly yield new information about the energy exchange ratio (and hence the important V—V transitions) for CO2−diluent collisions. It might also be possible to obtain more accurate values for the long V—T relaxation times for CO2 collisions with the heavy noble gases. These possibilities are discussed.
Rotational Barriers in Hydrogen Peroxide
Authors: Davidson Robert B. , Allen Leland C.
Published: February 2004

The rotational barriers in hydrogen peroxide are investigated using LC(Hartree–Fock) AO MO SCF calculations. Systematic improvement of the basis set produces a definite trans barrier, demonstrating that this barrier, like all those previously studied, is calculable within the Hartree–Fock approximation. Allowance for geometry adjustment, particularly OOH angle variation, leads to a cis barrier much closer to agreement with experiment than that obtained assuming rigid rotation. The theoretical and experimental inplications of these findings are discussed.
Low Frequency Motions in Barium Azide Crystals
Authors: Iqbal Zafar , Malhotra M. L.
Published: February 2004

A reinvestigation of the k ∼ 0 infrared and Raman active lattice modes of BaN6 crystals is reported. The symmetry species of the Raman active modes were determined unequivocally by oriented single crystal laser excited Raman spectroscopy. A new band at 40 cm−1 was resolved and a number of symmetry reassignments were made. The results are in essential agreement with the space group P21 / m–C2h2 for the crystal. The transmission far infrared spectra of polycrystalline BaN6 and SrN6 were measured between 20 to 300 cm−1 and compared with the reflection spectrum of BaN6 reported in the previous study.
Picosecond Pulse Radiolysis. III. Reaction Rates and Reduction in Yields of Hydrated Electrons
Authors: Aldrich J. E. , Bronskill M. J. , Wolff R. K. , Hunt J. W.
Published: February 2004

Rate constants for reactions of the hydrated electron with a wide range of compounds, including simple salts and amino acids, have been measured in the time region 20–350 psec. In nearly all cases the second-order rate constant for reaction with the hydrated electron did not change in the concentration range studied. However, the measured rate constant was in general different to that obtained in dilute solutions, and this was attributed to incomplete formation of the ionic atmosphere around the hydrated electron before reaction. Apart from the hydronium ion, Haq+, nearly all compounds decreased the initial hydrated electron yield: in all cases this decrease showed an exponential dependence on concentration. Compounds most efficient at decreasing the hydrated electron yield were cystine and cadmium salts, in both cases 0.39 mole/liter being needed to reduce the initial yield to 37%. The ability to reduce the initial yield showed no direct correlation with the corresponding hydrated electron rates. This and other evidence suggest that radiation-produced electrons are reacting before solvation.
Microwave Spectrum of 2-Aminoethanol: Structural Effects of the Hydrogen Bond
Authors: Penn R. E. , Curl R. F.
Published: February 2004

The microwave spectra of six singly substituted isotropic species of 2-aminoethanol have been observed and assigned. The molecule has been found to exist in a gauche form with an intramolecular hydrogen bond of the O–H···N type. The rs structure of the groups involved in the hydrogen bond obtained is striking primarily in having an unusually long OH bond distance of 1.14 Å. The internal rotation dihedral angles assume values which minimize the distance between the hydroxyl proton and the lone-pair electrons of the nitrogen. This corresponds to the OH bond halfway between the eclipsed and staggered conformation with respect to the C–C bond. The dipole moment was determined from Stark effect measurements to be 3.05 ± 0.05 D and agrees well in magnitude and direction with that predicted by adding the moments of the alcohol and amine groups. The nitrogen nuclear quadrupole coupling constants were determined and agree well with those expected for an amine group not involved in hydrogen bonding.
Second Virial Coefficients and Intermolecular Force Constants of the Ethane–Hydrogen Sulfide System
Authors: Khoury Fouad , Robinson D. B.
Published: February 2004

Second virial coefficient data of ethane, hydrogen sulfide, and four mixtures of the two components at approximately equally spaced concentrations and at temperatures between 50 and 125°C were used for determining interaction second virial coefficients, evaluating the intermolecular force constants, and calculating the system second virial coefficients from the Lennard-Jones (6–12) and Stockmayer potentials. From second virial coefficient data between 25 and 200°C, the ethane force constants for the Lennard-Jones (6–12) potential were determined as ε / k = 219°K and σ = 4.59 Å, and the hydrogen sulfide force constants for the Stockmayer potential as ε / k = 194.5°K, σ = 5.15 Å, and t* = 0.1. Using the respective intermolecular potentials and force constants, it was found that the calculated second virial coefficients of ethane and hydrogen sulfide agreed with experimental data within 1% for the former and 2.5 to 4% for the latter. Because of the polarity of hydrogen sulfide, interaction second virial coefficients were calculated from the Lennard-Jones (6–12) potential using force constants obtained from modified mixing rules to account for the dipole–induced dipole interactions. The calculated interaction second virial coefficients differed from experimentally determined values by an average absolute deviation of 1.9% in the temperature range between 50 and 125°C. Experimental and calculated mixture second virial coefficients in the same region agreed within 2%.
Statistical Mechanics of a Compressible Ising Model with Application to β Brass
Authors: Baker George A. , Essam John W.
Published: February 2004

An Ising model in which the lattice parameter is allowed to fluctuate is studied, and the effects of antishearing forces which were omitted from a previous model are considered. It is found that, except in the limit when these forces are zero, the model exhibits a first-order transition. Depending on the parameters, the model can nevertheless appear to be undergoing a second-order transition which will only change to first order when the specific heat is quite large. The apparent exponents can fall on either side of the asymptotic values for the rigid lattice. A numerical study of the case when the antishearing forces are large shows good agreement with available neutron data for β brass. A comparison with the specific heat measurements of Ashman and Handler is also made.
Time-of-Flight Spectroscopy of Metastable Photodissociation Fragments. N2O Dissociation in the Vacuum uv
Authors: Gilpin R. , Welge K. H.
Published: February 2004

The photodissociation of N2O involving electronically excited metastable fragments has been investigated at wavelengths ≳ 1050 Å by photofragment translational energy spectroscopy. Irradiation was carried out with light pulses of a few microseconds duration, and fragment energies were measured by means of the time-of-flight technique. Auger electron emission from metal surfaces, cesium and brass, was used to detect metastable fragments after a flight path length of 46 cm. Experiments have been made in the wavelength regions ∼ 1050–1440, ∼ 1250–1440, and ∼ 1350–1440 Å. Formation of the metastables N2(A 3Σu+) and O(1S) in the processes N2O→N2(A 3Σu+)+O(3P) and N2O→N2(X 1Σg+)+O(1S) has been observed. O(1S) appeared in a translational energy range from ∼ 3 to 1 eV, and N2(A 3Σu+) in a range from ∼ 1 to 0.1 eV. O(1S) produced electron emission upon deactivation at a cesium-cated surface, and N2(A 3Σu+) produced electron emission upon deactivation at a cesium and also a bare brass surface.
Application of Conformal Solution Theory to Gas–Gas Equilibria
Authors: Tan Paulino Y. , Luks Kraemer D. , Kozak John J.
Published: February 2004

The conformal solution theory (CST) is applied to the problem of gas–gas immiscibility. It is found that the occurrence of this phenomena can be predicted in the system He–Xe; in particular, the calculated critical locus is in satisfactory agreement with the experimental data of de Swaan Arons and Diepen, provided a suitable reference is chosen. Furthermore, using CST as a guide, it was found that criteria could be developed, related to Temkin's criteria, which permit the prediction and classification of the three types of gas–gas equilibria known to occur in mixtures of nonpolar molecules.
Model Calculations of Transport Coefficients for Diatomic Gases in an External Magnetic Field. II. The Cartesian Tensor Perturbation Scheme
Authors: Cooper E. R. , Hoffman D. K.
Published: February 2004

Model calculations are used to examine the convergence of a Cartesian tensor perturbation scheme for computing transport coefficients of diatomic gases in a static magnetic field. Numerical results are given to fourth order in the “nonsphericity” for the thermal conductivity and viscosity coefficients. For the shear viscosity only the second-order contributions are significant. However, for the thermal conductivity, bulk viscosity, and coupling coefficients third-order contributions are important. It is found that the addition of Sonine polynomials in the linear and angular momenta in the expansion for the shear viscosity makes no substantial contribution.
Ultrasonic Velocity and Absorption in Liquid Mixtures of K–Rb and Na–Cs
Authors: Kim M. G. , Letcher S. V.
Published: February 2004

Ultrasonic absorption and velocity measurements have been made in potassium–rubidium and sodium–cesium alloys at temperatures from 25 (or the liquidus points) to 250°C. It has been found that the potassium–rubidium system behaves as an ideal liquid mixture. For both potassium–rubidium and sodium–cesium alloys, Rao's constant and Wada's constant calculated from measured velocity data vary linearly with concentration and are temperature independent to within 2% over the temperature range 100–200°C. The ultrasonic measurements in the sodium–cesium system suggest a substantial molecular association and the absorption peak at 75 at.% sodium concentration is attributed to a molecular association of the form of 3Na+Cs⇋Na3Cs. The Na3Cs has been identified as the critical composition of an assumed submerged miscibility gap under the inflection point of the melting-point curve.
EPR Studies of Multiple Ag Trapping Sites Produced in Gamma-Irradiated Frozen AgNO3 Ices
Authors: Bales Barney L. , Kevan Larry
Published: February 2004

EPR studies show that gamma-irradiated AgNO3–KF and AgNO3 ices at 77°K form Ag0 in several magnetically distinct sites. Temperature and optical excitation cause conversions among these sites with little loss of Ag0. From 77 to 150°K the predominant change is form a matrix site characterized by a symmetric electric field to a matrix site characterized by an asymmetric electric field. This is explained in terms of water dipole rotation in response to the removal of the electric field of Ag+ upon formation of Ag0. Then the change in electric field due to water dipole rotation semiquantitatively accounts for the change in magnetic parameters of the Ag0 sites. The activation energy for the dipole rotation process is 0.12 eV. At higher temperature Ag0 is converted to Ag2+ with an activation energy of 0.32 eV, and finally Ag2+ decays with an activation energy of ∼ 0.5 eV. These activation energies are discussed in terms of L-defect formation and motion of the ice matrix. Optical studies show that uv light converts Ag2+ to Ag0 in a symmetric site and that visible light converts Ag0 from a symmetric to an asymmetric site and partly back to Ag2+.
Indices of Refraction, Susceptibilities, and Correlation Functions
Authors: Fulton Robert L.
Published: February 2004

The previously derived phenomenological Maxwell equation [R. L. Fulton, J. Chem. Phys. 50, 3355 (1969)] is used to give a general description of the propagation of electromagnetic radiation in media which are invariant under translations and rotations. The connections between the complex indices of refraction and correlation functions are derived with a minimum of hypotheses about the nature of the medium. It is shown that the commonly assumed connection between the complex angle of rotation of plane polarized light in optically active media and correlation functions is more general than the usual derivation indicates. The correct inclusion of the frequency dependence of the index of refraction in the connection between the optical parameters and the Fourier transform of the dipole–dipole correlation function is shown to give rise to qualitative and quantitative changes of infrared band shapes, including the narrowing of lines, in the cases of C6F6 (1527 cm−1), C6H6 (678 cm−1), and CHCl3 (760 cm−1). The contribution of the 1527-cm−1 band of C6F6 to the time dependent dipole–dipole correlation function is found, obtaining a relaxation time of τr = 1.07 psec when the frequency dependence of the index of refraction is correctly included as compared to a value of τr = 0.58 psec when the variation is disregarded. The correlation functions arising from the cosine and the sine Fourier transforms of the 522-cm−1 band of CH3I are determined, the comparison of which with the dipole–dipole correlation function illustrates the necessity of retaining both transforms in the calculation of the correlation function.
Spontaneous Ionization of a Hydrogen Atom in an Electric Field. I
Authors: Hirschfelder Joseph O. , Curtiss Larry A.
Published: February 2004

The time-independent Schrödinger equation expressed in parabolic coordinates for a hydrogen atom in an electric field was numerically integrated for the state n = 5, n1 = 3, n2 = 0, and m = 1 to obtain the resonance energy Er and the rate of ionization τ−1 for field intensities ranging from 8 × 105 to 11 × 105 V/cm. It is found that near the resonance energy, τ−1 varies quadratically with (E − Er)2 in accordance with the well known Weisskopf–Wigner treatment of metastable states. When E is nearly equal to Er, the wavefunction has a node at the outer turning point—no explanation is offered. At the very high field intensities considered, there was considerable difference between Er
Energy Loss Spectra of Low-Energy Electrons Scattered from Thin Solid Molecular Films
Authors: Merkel Paul B. , Hamill William H.
Published: February 2004

An electron impact spectrometer designed for measurement of energy loss spectra of low-energy electrons reflected from thin solid films is described. The spectrometer operates at impact energies as low as 1 eV and is capable of monitoring dynamic changes in electronic excitation cross-sections in the important threshold region. Spectra of benzene demonstrate a progression from vibrational excitation through electronic excitation to ionization as the most prominent energy loss mode as incident electron energy is increased. Excitations of benzene to the optically forbidden B1u3 or B2u1 states, while highly probable near threshold, show a rapid falloff in excitation probability at higher impact energies as compared to the optically allowed E1u1 ← A1g1 transition. In studies on 1-hexene, losses involving excitation to the lowest triplet state are also prominent near threshold.
Diamagnetic Anisotropies of Metal-Free, Nickel(II), and Zinc(II) Phthalocyanines
Authors: Barraclough C. G. , Martin R. L. , Mitra S.
Published: February 2004

Diamagnetic susceptibilities and anisotropies of metal-free, nickel(II), and zinc(II) phthalocyanines are reported. Calculations based on Pauling's semiclassical model give very poor agreement with the experimental results. The results are interpreted following the procedure of Amos and Roberts from which it emerges that only part of the total anisotropy can be attributed to the π-electron macrocyclic ring.
Two Algorithms for Choosing Optimum Parameters in the Variation–Perturbation Calculation of Physical Properties
Authors: Kirtman Bernard
Published: February 2004

Two algorithms for choosing optimum parameters in the variation–perturbation calculation of physical properties are presented. These algorithms are based on a judicious combination of the Rayleigh–Ritz variation principle with a stationary condition on the property. Some examples are discussed.
Influence of Molecular Geometry, Orientation, and Dynamics on Angular Correlation Patterns from Rotationally Labeled Macromolecules
Authors: Shirley D. A.
Published: February 2004

In order to determine the sensitivity of gamma-ray angular correlation patterns from solute macromolecules labeled with rotational tracers such as 111mCd, a theoretical study was made of the behavior expected under certain conditions. A nucleus of spin 52, acted upon by an axially symmetric electric field gradient, and bound to a rodlike macromolecule, was considered. Under static conditions (no molecular rotation), the time-dependent correlation pattern is quite sensitive to molecular orientation and, for oriented molecules, to the angle between the axis of the field-gradient tensor and the molecular axis. A general equation and results for selected geometric configurations are given. When molecular rotation is allowed, a classical model is applicable if the rotation is sufficiently slow. This model is used to calculate relaxation curves for several geometrical configurations under the condition that the macromolecules rotate about their long axes. These curves are shown to have considerable diagnostic value. Finally, the applicability of rotational tracers in the light of these results is discussed.
Crystal Field Splitting of the Energy Levels of Nd3+ and Er3+ in CaWO4
Authors: Gualtieri J. G. , Lhery G. P. de
Published: February 2004

Crystal field parameters appropriate for D2d symmetry were fit to data on the IJ4 level splittings of Nd3+:CaWO4. The symmetry assignments of the sublevels of I9/24 now seem firmly established. The “missing” sublevel in I11/24 was selected by comparing to existing Nd3+:PbMoO4 data. Spectral data which were used to interpret the I13/24 and I15/24 sublevel structure are presented. The total rms deviation for the I4 term without g-value fitting was 9.4 cm−1. When g-value fitting was included, the rms deviation was 10.7 cm−1. The total rms deviation for the F 4term of Er3+:CaWO4 was 7.2 cm−1.
Entropy Change and Fluctuation in Reaction System
Authors: Ishida Kenzi
Published: February 2004

The irreversible entropy change ΔiS due to a chemical reaction near equilibrium in a closed system is expressed by ΔiS = − k / 2χ(ξ − ξe)2, where k is the Boltzmann constant, and ξ is the degree of advancement. The reciprocal of the factor χ, according to the stochastic approach to chemical kinetics, is the fluctuation in the number of molecules of reacting species at chemical equilibrium. It is similarly shown that the factor Γ, which Eigen and de Maeyer introduced in the thermodynamic analysis of chemical relaxation, is equivalent to the fluctuation. The interrelations between chemical affinity, equilibrium reaction rate, and relaxation time are also discussed through these relations to the fluctuation.
Effect of Pressure on the Electronic Structure of Phthalocyanine and Iron Phthalocyanine Derivatives
Authors: Grenoble D. C. , Drickamer H. G.
Published: February 2004

The electronic structures of phthalocyanine, ferrous phthalocyanine, and the adducts with pyridine, 3-picoline, 4-picoline, and piperidine have been studied to 175 kbar pressure using optical absorption and Mössbauer resonance. One observes shifts of the optical absorption peaks to lower energy and changes in relative intensity of peaks which can be explained in terms of changes in the configuration interaction. Fe(II) in ferrous phthalocyanine is in an intermediate spin configuration at all pressures. In the axially coordinated adducts the Fe(II) is low spin at 1 atm. For the pyridine and picoline adducts this is caused by the increased backbonding to the axial ligands in addition to the phthalocyanine and by repulsion due to σ bonding. These factors both tend to separate the dz2 orbitals from the dπ orbitals. In the piperidine adduct only the latter factor is operative. With increasing pressure the low spin compounds convert partially to a new spin state, believed to be intermediate spin. The picolines show the most conversion, the pyridine adduct less, and the piperidine complex still less. The general explanation lies in the decrease in backbonding at high pressure caused by the tendency for occupation of the ligand π* orbitals by ligand π electrons. A similar effect has been observed in ferrocyanides and in phenanthroline complexes. The differences among the various adducts can be explained in terms of differences in the degree of π backbonding and σ bonding.
Electronic Transition Moment of the Lyman Bands of H2 (B 1Σu+–X 1Σg+) as a Function of Internuclear Separation
Authors: Marchetti M. A. , Paglia S. R. La
Published: February 2004

The LCAO–MO–CI method is applied to the study of the electronic transition moment of the Lyman bands of H2 (B 1Σu+–X 1Σg+) over the range of internuclear separations 1 ≤ R ≤ 6 a.u. It is found that configuration interaction is responsible for a strong nonlinear variation of the transition moment with internuclear distance (maximum transition moment at 3.0 a.u.). Comparison with other calculations indicates that the method is applicable to more complicated molecules and permits the examination of how individual electron correlation effects contribute to the transition moment.
Effective Potentials between the Components of a Hydrogeneous Plasma
Authors: Barker A. A.
Published: February 2004

Two-particle “effective potentials,” which incorporate the quantum mechanical effects into the pair interaction potential, are evaluated accurately. Tables and graphs of these potentials between electron–proton, parallel spin electron–electron, antiparallel spin electron–electron, and proton–proton are presented for a wide range of temperatures. The range of validity and analytic properties of the effective potentials in certain regions are given. Possible uses of these potentials to evaluate thermodynamic properties and percentage ionization of the plasma are discussed.
Anomalous Alignment and Domains in a Nematic Liquid Crystal
Authors: Parker J. H. , Carr E. F.
Published: February 2004

The relationship between anomalous alignment and domain formation is examined for the room temperature nematic liquid crystal, p-methoxybenzilidene p-n-butylaniline (MBBA). An increase in order with the long molecular axes preferring a direction perpendicular to an externally applied low-frequency electric field is observed for potential differences below the threshold voltage for anomalous alignment. Employing measurements of the dielectric loss at a microwave frequency of 24.4 GHz, the threshold voltage for anomalous alignment is examined as a function of the frequency of an externally applied electric field. This is then contrasted with the frequency dependence of the threshold voltage for domain formation as determined from visual observation. Comparing optical and dielectric data we show that the threshold is the same in each case. At very high electric field strengths, behavior indicating a tendency towards random molecular alignment is observed.
Energy Transfer in Poly(vinyl toluene)
Authors: Powell R. C.
Published: February 2004

An investigation of host-sensitized energy transfer in poly(vinyl toluene) doped with p-terphenyl and diphenylstilbene is reported, along with a study of energy transfer from p-terphenyl to diphenylstilbene in the poly(vinyl toluene) host. The results indicate that excitons can migrate in poly(vinyl toluene) and that excimer-forming sites and p-terphenyl molecules act as exciton traps. Both of these kinds of traps can transfer their energy to diphenylstilbene by radiative reabsorption and by long-range resonant interaction.
Two-Body Dispersion Forces for Pairs of Polyatomic Molecules
Authors: Yorke Ellen D. , De Rocco Andrew G.
Published: February 2004

The question of additive two-body forces for polyatomic molecules is investigated by a generalization of our earlier results for a Drude model. We show that to third order of perturbation, additivity obtains for spherically symmetric arrays consisting of harmonic dipole oscillators which are characterized by different frequencies, which can contain unequal numbers of oscillators and for any number of arrays N ≥ 2.
Photolysis Mapping Studies of Aliphatic Carbonyl Compounds
Authors: Solomon J. , Jonah C. , Chandra P. , Bersohn R.
Published: February 2004

The photolysis mapping technique is a marriage of an old radical detecting system with the following principle: If polarized light is used for photodissociation, the flux of fragments will be anisotropic because the molecular absorption is anisotropic in the molecular axis system. The simplest aliphatic carbonyl compounds (formaldehyde, acetaldehyde, propionaldehyde, and acetone) were photodissociated using polarized ultraviolet light. The gases were held at such a low pressure that the fragments travel to the walls without collision in the gas phase. On the walls the radicals were detected by the old mirror removal technique. There is a substantial anisotropy of removal. The sense of the anistropy is different for the different molecules, being perpendicular for formaldehyde and acetone, and parallel for acetaldehyde and propionaldehyde. These results are interpreted by assuming that the carbonyl compounds all become nonplanar in the excited state and the ultimate direction of the fragments can be inferred from the initial motion. In formaldehyde the departing hydrogen atom leaves in a direction perpendicular to the plane as does the methyl in acetone. On the other hand, in acetaldehyde and propionaldehyde the hydrogen atom leaves the molecular plane but remains attached to the central carbon atom while the departing alkyl radicals leave in the molecular plane, parallel to the transition dipole moment.
Stresses in Dilute Solutions of Bead–Nonlinear-Spring Macromolecules. I. Steady Potential and Plane Flows
Authors: Tanner R. I. , Stehrenberger W.
Published: February 2004

The mechanics of a dilute solution of bead–nonlinear-spring molecules are investigated in various steady homogeneous flows. A new type of nonlinear spring (“linear locked”) with a finite end-to-end distance is introduced which allows closed solutions of the diffusion equation to be found. Hence, only a simple numerical calculation of stresses is necessary. In a steady shear flow we find a viscosity decreasing with shear rate, and in an extensional flow there is a limiting upper viscosity for large extension rates. Neither of these realistic results holds for the Rouse model. In a shear flow the first normal stress difference is positive, and the second normal stress difference is zero. In general steady plane flow it is shown there is a critical kinematic condition separating states of large and small dissipation for highly extensible molecules. The role of polydispersity in molecular weights is briefly considered.
Energy Transfer Reactions of N2(A3Σu+). IV. Measurement of the Radiative Lifetime and Study of the Interaction with Olefins and Other Molecules
Authors: Meyer J. A. , Klosterboer D. H. , Setser D. W.
Published: February 2004

The rate constants and products from the interaction of the first triplet state of nitrogen, N2(A 3Σu+), with C2H4 and cis-C4H8 have been measured in a discharge flow apparatus. The reactions are fast with rate constants near 1014 cc mole−1·sec−1 and give products which are typical of other triplet—triplet donor reactions with olefins. The product yields were used to measure the concentration of N2(A 3Σu+) molecules. This concentration was combined with the absolute emission intensity from the N2(A 3Σu+−X 1Σg+) transition to estimate the radiative lifetime of (N2A 3Σu+; v′=0, 1). The data support the recently published low lifetime value reported by Shemansky and Carleton. Rate constants were measured for quenching of N2(A 3Σu+) by acetylene, cyanogen, propene, benzene, 1,4-butadiene, cyclopropane, oxygen, sulfur dioxide, carbon monoxide, nitrous oxide, and ammonia. The first-order removal of N2(A 3Σu+) by the quartz surface also was characterized.
PVT Behavior of Water at Negative Pressures
Authors: Winnick Jack , Cho Sung J.
Published: February 2004

Measurements have been made of the extension of a column of liquid water in a centrifugal field. Schlieren photographs of the meniscus position were made at rotational speeds up to 18 000 rpm at temperatures from 5 to 35°C. The data were analyzed using a form of the Tait equation. All of the data were able to be represented well within experimental error, 7.5× 10−5cc/cc. The constants in the equation, found by regression of these negative pressure data, are very nearly those which describe the positive pressure region.
ESR Study of Radical Structure and Symmetrical Hydrogen Bond in a Single Crystal of Potassium Hydrogen Maleate Irradiated at 77°K
Authors: Toriyama Kazumi , Iwasaki Machio
Published: February 2004

ESR study has been carried out on the structure of radicals produced in an irradiated single crystal of potassium hydrogen maleate which is known as a typical compound having a symmetrical intramolecular hydrogen bond. It was found that in the radical formed by removal of the acidic proton the unpaired electron occupies the σ antibonding orbital between the in-plane p orbitals of the two ring oxygen atoms, when the crystal is irradiated at 77°K. The principal values of the g tensor for this radical were determined to be gxx=2.0043, gyy=2.0039, and gzz=2.0079. The hyperfine couplings for the two vinylene protons are equivalent and have the nearly isotropic value of 5±1 G. On the other hand, if the crystal is warmed up to room temperature after irradiation at 77°K, the same species of radical is formed but the unpaired electron occupies the delocalized π orbital. This radical is the same as that found in room-temperature irradiation which was previously reported. Both the radicals possess the mirror symmetry perpendicular to the C=C bond as does the mother molecule. The formations of such symmetrical radicals are closely related to the symmetrical structure and the extremely short O···O distance of the parent molecule, which are due to the symmetrical hydrogen bond. The cause of the formations of the σ and π electron radicals from the same mother molecule is also discussed.
Ultrasonic and Relaxational Spectroscopy of Fast Reactions. II. Liquid
Authors: Tabuchi Daisaku
Published: February 2004

As a method of ultrasonic spectroscopy, ultrasonic absorption and dispersion in liquid due to multiple reactions are treated theoretically, and the interaction of the reactions is examined. The complex velocity of sound is calculated from the changes of the number of moles, the volume, the internal energy, and the rates of the reactions by sound wave. The heat capacities for liquid at constant pressure and at constant volume are composed of the terms of a simple mixture, the terms due to each reaction, and the terms due to the mutual interaction of the reactions. The latter two terms depend on the sound frequency. Examples involving one and two reactions are shown. The characteristics of the ultrasonic spectrum will be treated in a later paper.
ESR Study of C·F2COO− Radicals in Irradiated Single Crystals of Sodium Chlorodifluoroacetate
Authors: Rogers Max T. , Kispert L. D.
Published: February 2004

Electron spin resonance studies have been made of the radicals produced by electron irradiation of sodium chlorodifluoroacetate at room temperature. Three sets of C·F2COO− radicals are observed, each with a somewhat different conformation or local environment in the crystal lattice, but each with nearly the same principal values of the hyperfine splitting tensor for the two equivalent α-fluorine atoms. One radical occupies two sets of nonequivalent positions characteristic of the space group. A second radical also shows site splitting in the ESR spectrum, but the maximum separation is only about 14 G since the maximum principal component of the hyperfine splitting tensor lies nearly parallel to the a axis of the monoclinic unit cell and one of the smaller principal values is nearly parallel to b. A third radical has its maximum principal hyperfine splitting direction perpendicular to b and minimum value parallel to b so that no site splitting is observed; however, triplet superhyperfine structure from interaction with two equivalent nuclei of spin one-half is present. The hyperfine coupling tensors have been evaluated and the structures of the radicals discussed. The radicals undergo some reorientation in the lattice on cooling from 300 to 77°K. Incomplete data for C·13F2COO− indicate that these radicals are probably nonplanar with the unpaired electron in an orbital with some s character. Exposure to air or gaseous oxygen converts all these to peroxide radicals, each of which gives only a single ESR line.
Measurements of CO Relaxation in an Unsteady Expansion Wave
Authors: Just T. , Roth P.
Published: February 2004

Vibrational relaxation of various CO–Ar mixtures in an unsteady expansion wave was measured using an infrared technique. Results indicated no deviations from values predicted using the Landau—Teller model.
Experimental Study of the Equation of State of Liquid Krypton
Authors: Streett W. B. , Staveley L. A. K.
Published: February 2004

The gas expansion method has been used to measure the density of liquid krypton at 11 temperatures from 120 to 220°K and at pressures up to 3680 atm. The results have been fitted to the Strobridge equation, which has been used to estimate, at regular intervals of pressure and temperature, the following properties: density, isothermal compressibility, thermal expansion coefficient, thermal pressure coefficient, configurational internal energy, and entropy relative to the saturated liquid. The equation of state results, together with estimated values of the third virial coefficient and published values of vapor pressure, second virial coefficient, and sound velocity in the liquid phase, have been used to estimate the following properties of the saturated liquid: enthalpy of vaporization, configurational internal energy, isothermal compressibility, thermal expansion coefficient, thermal pressure coefficient, adiabatic compressibility, and specific heats. The linear dependence of configurational internal energy on density, over a wide range of pressures and temperatures, suggests a relatively simple form for a hard sphere equation of state for monatomic liquids. The evaluation of constants for such an equation is briefly discussed.
Isotopic Shift for Vibrations with Potential Energy Barriers
Authors: Laane Jaan
Published: February 2004

The isotopic shift ratio has been examined for nine different double-minimum potential energy functions. The shift generally has a minimum when the v=2 state, on which the transition terminates, has an energy very close to the top of the barrier. For large barriers the isotopic shift approaches that of a harmonic oscillator. The minimum value of the shift for any curve found was 1.17, in contradiction to previous postulates that this value could be less than unity. Recent analyses of the δOH bending mode in acetic acid are discussed using these results.
Theoretical Basis for the Viscoelastic Response of a Polymeric Network
Authors: Curro John G.
Published: February 2004

Kubo's general statistical mechanical theory of irreversibility is applied to a polymer chain subjected to an external force. If it is assumed that the deformation is affine, then the Boltzmann superposition equation for a polymer network is obtained. The empirical compliance function of the Boltzmann superposition equation is shown to be a correlation function in the end-to-end vector of a chain. This result is independent of any model. The explicit form of the correlation function is evaluated for the Rouse model.
Stochastic Model for Chains with Excluded Volume
Authors: Alexandrowicz Z.
Published: February 2004

A chain consisting of n links with excluded volume (EV) interactions is described by a multilevel hierarchy of segments of increasing length, joined together in succession. Thus the second level segments, t=2, consist of s links, the third consist of s second segments (or s2 links), etc., t=1, 2, ···T, until the chain length is reached with the longest T segment, n=sT. The configurations for this model chain are constructed with a stochastic process which links the segments together, head to tail, with a probability that favors their orientation in the forward direction. Such a partly oriented linkage on one hand, decreases the multiplicity of the chain configurations but, on the other, increases the Boltzmann factor due to EV interactions. The linking probability at each level is, therefore, determined with a variation principle that maximizes the product of these two quantities. An approximate analytical solution shows, that the chain expansion coefficient (accumulated over all T levels) obeys the Fixman equation α3∼z. It seems that a computer execution of the requisite stochastic process would permit a further study of this, and of related, models for chains with EV.
Pressure Effect of Noble Gases on the Pure Rotational Spectrum of Hydrogen Chloride
Authors: van Kreveld M. E. , van Aalst R. M. , van der Elsken J.
Published: February 2004

The changes of the pure rotational spectrum of HCl in the region 15–170 cm−1 under the influence of compression with helium and argon up to 100 atm have been investigated. The experimental results are compared with the spectra calculated on the basis of correlation theory. Energy and momentum transfer in collisions of short duration give full account of the observed features.
Reinterpretation of the Alkali Chloride Dissociation Rates of R. Hartig et al. as Cl− Collisional Detachment Rates
Authors: Mandl A.
Published: February 2004

Thermal dissociation rates kd for various alkali chlorides have been published by Hartig et al. We have reinterpreted their results in terms of a collisional detachment rate for Cl−. Our interpretation implies a collisional detachment rate of Cl− by Ar kCl− (Ar) ∼5×10−10exp(−83 000/RT) cm3/sec. Our reevaluation of their kd also removes the large disagreement between their measured rates and calculated values of the thermal dissociation rates of the alkali chlorides using the theory of Bates and Flannery.
Carbon-13 Relaxation and Internal Rotation in Mesitylene and o-Xylene
Authors: Kuhlmann Karl F. , Grant David M.
Published: February 2004

A dynamic method for determining carbon-13 spin—lattice relaxation times and nuclear Overhauser enhancements from spectra of samples with natural isotopic abundance is presented. The method, along with adiabatic rapid passage and relative intensity measurements, is used to determine the relaxation times and important relaxation mechanisms of all carbons in neat samples of o-xylene and mesitylene. The results are interpreted in terms of over-all molecular rotational diffusion and internal methyl rotation. The relaxation times in mesitylene indicate that internal methyl rotation is very rapid with respect to over-all molecular diffusion. There is also evidence that the relatively free methyl rotation leads to relaxation of these carbons through spin—internal-rotation interaction. In the case of o-xylene the internal rotation is not well separated from the over-all rotation, but approximate calculations show that the results are consistent with a rate of hindered rotation which does not greatly exceed the over-all diffusion rate, with a barrier to rotation of 1 or 2 kcal/mole. Relatively large Overhauser enhancements and dipolar relaxation rates for the substituted ring carbons indicate that intermolecular dipole—dipole interactions are significant in the relaxation of these carbons. These intermolecular interactions are shown to be relatively unimportant, however, for carbons with directly bonded protons.
Rayleigh Scattering by Linear Flexible Macromolecules
Authors: Utiyama Hiroyasu , Tsunashima Yoshisuke , Kurata Michio
Published: February 2004

Precise light-scattering measurements were made on poly-α-methylstyrene samples with sharp molecular weight distribution, the molecular weight ranging from about 400 thousand to 7 million. The specific reduced scattered intensity at infinite dilution was determined for 18 scattering angles in the range of 9°−150°, in trans-decalin at 9.6° (theta temperature), 15.2, 29.4, 91.3°C, and in benzene at 30.0°C. In trans-decalin, the particle scattering factor P obtained is in good agreement with the well-known Debye equation irrespective of the temperature and the molecular weight. Experimental results in good solvent, benzene, are also well represented by the Debye equation for 1≥P≥0.15, but significant deviation is observed for P〈0.15. All the experimental data can be fitted to a theory in which the generalized Domb—Gillis—Wilmers distribution function for end-to-end distances R, ΦN(R)=CNRl exp[− (R/σ)t], is used for polymer chains of N segments with excluded volume effects. CN is the normalizing constant; σ is related to the standard deviation of R; and t=2/(1−ε), where ε is defined by 〈 R2〉=AN1+ε. A is a numerical constant. The parameter l obtained by fitting the experimental data to the theory was found to increase with ε and to be slightly greater than t.
Characterization of an Active Matrix Binder Photoreceptor X-Form Metal-Free Phthalocyanine in Poly(N-vinyl Carbazole)
Authors: Hackett C. F.
Published: February 2004

The photoconductivity of a binder-type photoreceptor, the X form of metal-free phthalocyanine in poly(N-vinyl carbazole) is shown to involve: a field-assisted thermal carrier dissociation step; an exclusive hole injection across a field-lowered barrier, i.e., Schottky emission; and facile hole transport across PVK layers. Highly efficient photoresponse peaks in the near infrared indicate that the lowest triplet state is an intermediate in the generation of charge carriers in the X form of metal-free phthalocyanine.
Intrinsic Viscosity of Polymer Chains with Small Excluded Volume
Authors: Yamakawa Hiromi , Tanaka Genzo
Published: February 2004

The intrinsic viscosity of polymer chains with small excluded volume is calculated on the basis of the Fixman—Pyun theory for unperturbed chains. The eigenfunctions of the unperturbed free-draining time evolution operator are chosen as the basis set, and the formulation is made so as to take into account the coupling of the normal coordinates for excluded-volume interactions but not for hydrodynamic interactions. An additional approximation introduced is the preaveraging of the Oseen hydrodynamic interaction tensor. Therefore, the present theory gives the same result as the Zimm theory in Hearst's version for vanishing excluded volume. Evaluation is carried out only in the nondraining limit, and the cubed viscosity—expansion factor is obtained as αη3= 1+1.06z –···, where z is the well-known excluded-volume parameter. This is consistent with the recent experimental results. Furthermore, it is emphasized that the present value for the coefficient of z is smaller than the corresponding value of 1.80 predicted by the boson-operator theory of Fixman and also the value of 1.55 obtained by Kurata and Yamakawa. It is noted that if the coupling of the normal coordinates is completely ignored, the corresponding value is 0.810.
Raman Scattering Studies in Liquids and Glasses. II. Liquid and Supercooled Liquid Glycerol
Authors: Wang C. H. , Wright R. B.
Published: February 2004

The Raman scattering technique was used to investigate the temperature dependence of the low frequency (10–250 cm−1) intermolecular spectrum in liquid and supercooled liquid glycerol. The Raman spectra, both polarized and depolarized, were interpreted by using a relationship connecting the Raman scattering spectral density to the imaginary dielectric susceptibility. The imaginary dielectric susceptibility function was then calculated by a damped harmonic oscillator model. Within the framework of this model, the temperature dependent behavior of the characteristic oscillator frequency, damping constant, and static susceptibility were obtained and interpreted as arising from the hydrogen bond motion existing in the glycerol system. The intermolecular Raman and the thermal neutron scattering results have been found to be supplementary and have both led to a consistent description of the various low frequency motions in the liquid and supercooled liquid glycerol as influenced by the temperature sensitive hydrogen bonding.
Calculation of the Anharmonicity in the Vibrational Frequencies of Alkane Molecules by the CFF Functions
Authors: Warshel A.
Published: February 2004

The CFF method is extended to include all the first five terms of the Taylor expansion of the molecular potential functions. A scheme for anharmonicity calculations in any molecule, in every equilibrium conformation is suggested. The actual anharmonicity calculation for ethane, n-butane, and cyclohexane is described. It is shown that a mixed function of bond stretching and bond angle bending, with Morse type dependence on the bond length is suitable for such calculations. The advantage of using potential functions instead of a force constant field, which is a central idea of the CFF philosophy, is strongly supported by the calculations.