bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the Thermal Conductivity of Neon Using Hot-Wire-Type Thermal Diffusion Columns
Authors: Saxena V. K. , Saxena S. C.
Published: February 2004

The thermal conductivity of neon is measured on two hot-wire-type thermal diffusion columns which are alike except for length. This has enabled a more explicit analysis of the so-called “end effects.” Convection and temperature jump effects are investigated experimentally by taking measurements for several values of gas pressure. The data are reported in the temperature range from 100° to 1200°C and these can be correlated by a quadratic polynomial in temperature (T), viz., λ × 105 = 4.68 + 2.62 × 10−2T − 4.40 × 10−6T2. Here λ is in cal cm− 1·sec− 1·deg− 1 and T is in degrees Kelvin. The present data are estimated to have an error of about ±2% and within this scatter these agree with the predictions of the theory and also with most of the available measurements. This technique appears very promising for generating data in a temperature range where none of the established techniques work satisfactorily.
Xenon-Sensitized Fluorescence of CO Excited by 1470-Å Radiation
Authors: Slanger Tom G.
Published: February 2004

The triplet fluorescence of CO, sensitized by xenon and excited by 1470-Å radiation, has been investigated. As opposed to unsensitized fluorescence, where almost all the observed triplet emission is from the d 3Δυ = 7 state, emission is observed from various vibrational levels of the d 3Δ, e 3Σ, and a′ 3Σ states. It is shown that Xe metastable atoms are not involved in the collisional process that causes excitation, and therefore, a reaction between the resonant Xe(3P1) atom and CO must be occurring. Experiments carried out to compare the quenching of unsensitized and sensitized fluorescence by He, Ar, and N2 indicate that there is a precursor to the emitting CO* in the sensitized case, presumably a collision complex of Xe(3P1) and CO. The reaction Xe* + CO→XeCO appears to take place at every collision, and the complex has a lifetime of at least 2 × 10−6 sec before it decomposes to Xe and CO*. Rate constants were obtained for the quenching of CO* by various gases, including CO, and ratios of rate constants were found for XeCO quenching by He, Ar, N2, and CO.
Jahn-Teller Effect in the EPR Spectrum of Cu++: MgO at 1.2°K
Authors: Coffman Robert E.
Published: February 2004

The EPR spectrum of Cu++: MgO at 1.2°K is described and shown to be characteristic of a Kramers quartet of states which have anisotropic transitions characteristic of a one-ion-per-unit-cell system. This is an octahedral symmetry property which may be realized either by the vanishing of the Jahn-Teller effect at 1.2°K or by the presence of tunneling between equivalent tetragonally distorted states. The tunneling process generates a Kramers doublet and quartet separated by a small tunneling (inversion) splitting, as has been shown by Bersuker and O'Brien. A theoretical g-value formula for the tunneling quartet is derived for the magnetic field in an arbitrary direction. The experimental g values are shown to be in good agreement with this formula, but they are not in agreement with a similar formula for the static octahedral symmetry quartet. The hyperfine structure is also shown to be better explained as a property of the tunneling quartet. The tunneling doublet has not been detected at 1.2°K and is presumed to be thermally depopulated. It is concluded that the paramagnetic resonance properties of Cu++:MgO at liquid-helium temperatures measured at 9 × 109 cps are determined by a dynamic tunneling effect. We have found no evidence for a “frozen-out” tetragonal distortion.
Assignment of the Lowest Triplet State of the Carbonyl Group
Authors: Dym S. , Hochstrasser Robin M. , Schafer Margaret
Published: February 2004

A study of the electronic spectrum of the 3nπ*←1A1 transition of benzophenone crystals is presented. The transition originates at 24 194 cm−1, and it displays carbonyl stretching and ring torsion modes of the molecule. The observed polarization ratio (Ib / Ia) of 2.5 ± 0.2 is indicative of the fact that at least two of the spin substates of the triplet can combine with the ground state in electric dipole radiation. The two transitions are z (parallel to C–O) and y (perpendicular to C–O in the R2CO plane) polarized with the former dominant by a factor of 3.

A polarized high-field Zeeman study of the transition shows that the σz and σx spin designated states are the active ones; this result shows that the 3nπ* state is of A2 (in C2υ) type and that the σx state becomes active through vibronic coupling amongst higher states. The appearance of torsional modes in the spectrum is discussed in relation to this vibronic coupling.
Multiple-Pulse NMR Experiments
Authors: Waugh J. S. , Wang C. H. , Huber L. M. , Vold R. L.
Published: February 2004

The behavior of a spin system disturbed by a train of closely spaced pulses can, under the proper limiting circumstances, be described in terms of a time-independent effective Hamiltonian. The necessary conditions on pulse spacing are discussed and a recipe is given for constructing the effective Hamiltonian. The method is applied to the previously employed trains of 180° or 90° pulses, obtaining the well-known limiting behavior for small pulse spacing. An analysis is given of a recently reported experiment using a train of phase-alternated 90° pulses. Two new experiments involving complex pulse sequences are proposed, one of which permits the arbitrary scaling of the effective chemical shifts in a high-resolution NMR spectrum, and the other of which annihilates dipole-dipole and quadrupole effects in solids, leaving the chemical shifts and scalar couplings.
Ellipsometric Study of Oxygen-Containing Films on Platinum Anodes
Authors: Reddy A. K. N. , Genshaw M. A. , Bockris J. O'M.
Published: February 2004

Ellipsometry is applied to study the oxidation of platinum in sulfuric acid solution. Steady-state and transient measurements show that oxide-film formation commences when the potential is anodic to 0.95 V. The film is light absorbing. The film thickness increases linearly with potential. A mechanism of film growth based on place exchange is developed.
Spectroscopy of EDA Complexes at High Pressures. VI. Absorption and Fluorescence of Crystalline TNB and TNF Complexes
Authors: Kadhim A. H. , Offen H. W.
Published: February 2004

Several aromatic hydrocarbons are complexed with trinitrobenzene (TNB) and trinitrofluorenone (TNF) in the crystalline state and subjected to increasing pressures (0-30 kbar). The charge transfer absorption shows a ∼1200 cm−1 red shift, while the fluorescence red shift may vary between 200-1700 cm−1 at 25 kbar. In the same complexes the Stokes shift decreases at higher pressures. This decrease can be understood in terms of charge-transfer forces and potential energy curves appropriate for weak EDA complexes.
Magnetic Properties of the BF and BH Molecules
Authors: Hegstrom R. A. , Lipscomb W. N.
Published: February 2004

Values of magnetic constants for the 11B 19F molecule in its 1Σ+ ground state have been calculated ab initio using coupled Hartree-Fock perturbation theory. Predicted values, the average of two calculations employing different gauge origins, are χ = − 14.3 ppm, μj /J = − 0.21 nm, σF = 250 ppm, CF = 85.7 kc / sec, σB = 82.9 ppm, and CB = 15.8 kc / sec. Predicted anisotropies for BF are Δχ = 5.92 ppm, ΔσF = − 360.6 ppm, and ΔσB = − 188.2 ppm. In addition, values for the anisotropies for the BH molecule are calculated to be Δχ = 45.80 ppm, ΔσB = − 690.9 ppm, and ΔσH = − 12.53 ppm.
Broadline NMR Study of H2O and D2O in Oriented Rayon Fibers
Authors: Dehl Ronald E.
Published: February 2004

The broadline NMR spectra of H2O and D2O absorbed in parallel fibers of highly crystalline rayon have been found to consist of two lines, whose separation depends upon the angle between the fiber axis and the magnetic field. The D2O splitting, resulting from quadrupole perturbation of the nuclear Zeeman levels, was about 10 times greater than the H2O splitting, produced by direct nuclear dipole-dipole interaction. Two models for the partial orientation of water molecules are discussed, (I) in which the molecules rotate about a fixed axis, and (II) in which the molecules reorient rapidly about all possible axes, but maintain a small resultant projection, along the fiber axis. Model I is shown to be incorrect for the rayon fibers, on the basis of the combined H2O and D2O results; Model II, however, appears to be applicable not only to rayon but to other examples of partially oriented water as well.
Calculations on Rydberg Terms of the Water Molecule
Authors: Lin T. F. , Duncan A. B. F.
Published: February 2004

Calculations are reported on Rydberg series terms of the water molecule and are compared with available experimental data. A one-center core function is assumed, based on a model of Banyard and March. Trial one-electron Rydberg functions are assumed to be mutually orthogonal and orthogonal to the core function. The one-electron energies are obtained from a potential which contains operators for the core electrons. The calculated terms are obtained with an average accuracy of about one percent or less except for lowest members of some series. Variation of terms with respect to screening parameters led to stationary values of terms in all cases.
Behavior of Trapped Electrons in Irradiated 3-Methylpentane Glass at 77°K
Authors: Irie Masahiro , Hayashi Koichiro , Okamura Seizo , Yoshida Hiroshi
Published: February 2004

Formation and decay of trapped electrons in 3-methylpentane glass irradiated by γ rays were studied by the electron spin resonance method at 77°K. In pure 3-methylpentane, the trapped electrons decayed by first-order reactions. Observed decay curves are clearly the superposition of two reactions having the first-order rate constants of 0.2 and about 0.04 min−1, respectively. The yield of the trapped electrons (G value) is 0.14 for the fast decaying part and 0.09 for the slow decaying part. The addition of a small amount of 2-methylpentene-1 slowed down remarkably the decay of the slowly disappearing electrons, whereas the decay of the fast disappearing ones was not affected. It is indicated that the latter electrons are intrinsic to the nature of the 3-methylpentane glass, being bound in shallow traps, and their decay is caused by the migration of the electrons themselves. The former electrons are trapped deeply in anomalous sites in the glass such as impurity sites. Their decay is caused mainly by the migration of positive charges.
Intermolecular Forces in Globular Molecules. VI. Octopole Moments of Tetrahedral Molecules
Authors: Spurling T. H. , De Rocco A. G. , Storvick T. S.
Published: February 2004

The octopole moments for methane and carbon tetrafluoride have been estimated from the temperature dependence of second virial coefficients. The central potential employed was the spherical shell model for which the force constants were derived from the temperature dependence of gas viscosity on the assumption that the octopole moment had no measurable effect on the viscosity. The values obtained for the moments, defined as Ω = (5 / 2) Σieixiyizi, were: methane,  ± 3.7 × 10−34 esu·cm3 and carbon tetrafluoride, ± 13.7 × 10−34 esu·cm3.
Physical Properties of Fluid CH4 and CD4: Experimental
Authors: Grigor Anthony F. , Steele William A.
Published: February 2004

Measurements of some physical properties of liquid and gaseous CH4 and CD4 are reported. The data were obtained at temperatures ranging from the freezing point up to 10° above the critical temperature and at pressures up to 70 atm. The measured quantities include vapor pressures, liquid molar volumes, liquid isothermal compressibilities, critical constants, and gas-phase molar volumes and compressibilities in the critical region. These results are compared with those of other workers and with some theoretical predictions of fluid behavior in the critical region.
Deuterium Isotope Effects on the Luminescence of Terbium and Europium Chelates
Authors: Mikula James J. , Salomon Robert E.
Published: February 2004

The intensity of luminescence of piperidinium tetrakis (1,3-diphenyl-1,3-propanediono) Tb (III) in EPA is enhanced when the phenyl groups are deuterated. This luminescence has been measured as a function of temperature and the enhancement appears to be a constant over the temperature range studied. Similar studies when carried out with piperidinium tetrakis (1,3-diphenyl-1,3-propanediono) Eu (III) with deuterated phenyl groups did not lead to any appreciable enhancement over that of the undeuterated complex. Similar results were obtained with deuterated and undeuterated tris dibenzoylmethides of Eu (III) and Tb (III). Increased ion emission was observed with deuterated Tb complex but not with the deuterated Eu complex. An explanation for the temperature dependence as well as the difference observed between the terbium and europium complexes is offered.
Multiplicity of Force Constants in the Vibrational Analysis of Molecules
Authors: O'Reilly E. J.
Published: February 2004

Double roots for the force constants arise in the solution of the secular equation because of the symmetry of the force constant matrix. If the F matrix is of order m, there are 12m (m − 1) sets of such double roots. These roots correspond to a difference in “phase” of the normal-coordinate composition. The set of single roots applicable to the molecular force field can be in principle found by solving 12m (m + 1) linear equations: Trλi = Tr(GF) = ΣijαsiαsjαuαFij using isotopic substitutions on the α sets of symmetrically equivalent atoms. Application is made to HCN.
Spin-Spin Interaction in Many-Electron Atoms
Authors: Malli Gulzari
Published: February 2004

Spin-spin interaction has been evaluated for all the atoms with pn and dn configurations using the radial functions calculated from numerical Hartree-Fock wavefunctions. The magnitude of the interaction is much smaller than the orbit-orbit and spin-other-orbit interaction and may in most practical cases be neglected.
Toward an Understanding of Potential-Energy Functions for Diatomic Molecules
Authors: Borkman Raymond F. , Parr Robert G.
Published: February 2004

The problem of understanding potential-energy functions for diatomic molecules is discussed. First, starting from the virial theorem, the Born-Oppenheimer electronic energy W ( R) is shown to satisfy the differential equation R2(d2W / dR2) + 4R(dW / dR) + 2W = − (1 / R) (d / dR)[R2T(R)] ≡ Q(R), where R is the internuclear distance and T(R) is the electronic kinetic energy, as a function of distance. Then the assumption Q(R) = const for R near Re, equivalent to the assumption T(R) = const + const / R2for R near Re, is considered. This assumption is shown to lead to simple formulas relating quadratic (ke), cubic (le), quartic (me), and higher potential constants, e.g., le = − 6ke, me = 36ke, (keme / le2)1 / 2 = 1. Ratios of potential constants are calculated for many diatomic species, including several electronically excited states. They are found to agree well with experiment. The quadratic force constants ke are estimated for a number of species, using a modified overlap-population concept. An approximate formula is developed which gives the force constant in terms of overlap populations, the equilibrium distance, the dissociation energy, and atomic-orbital kinetic energies. Calculated and experimental values agree within about 15%. Finally, a well-known approximate rule that Re2ωe = const, relating internuclear distance and vibrational frequency through a series of different electronic states of one molecule or different molecules, is elucidated using a free-electron or uncertainty-principle interpretation of the R-dependent part of T(R).
Correlation of Triplet Positronium Annihilation Parameters with Structural and Electronic Properties of Organic Liquids
Authors: Gray Peter R. , Cook Charles F. , Sturm Gene P.
Published: February 2004

The parameters of triplet positronium annihilation in 193 organic liquids have been measured. The annihilation quenching cross sections, 〈συ〉A v = (1 / τ2) (M / ρ), is a linear function of the length of the molecule in homologous series of compounds. Partial quenching cross sections, calculated for 27 structural functional groups, are used to calculate annihilation cross sections. The importance of steric effects in the annihilation mechanism is demonstrated in the study of several isomeric systems. Triplet positronium intensities depend upon specific atoms or groups in the molecule, rather than any property of the molecule as a whole. A correlation is also shown between annihilation quenching cross sections and electron polarizabilities as measured from indices of refraction. Several systems which quenched the triplet positronium were examined, e.g., free radicals, quinones, and paramagnetic species.
Molecular g Values and Paramagnetic Susceptibility in Pi-Bonding Systems: Vinylidene Fluoride
Authors: Flygare W. H. , Lo Mei-Kuo
Published: February 2004

The first-order molecular Zeeman effect is observed in vinylidene fluoride to yield the molecular g values along the principal inertial axes. The results are | gaa | = 0.0373 ± 0.002, | gbb | = 0.0480 ± 0.003, and | gcc | = 0.0064 ± 0.003 where the a axis passes through both carbon nuclei and the b axis is in the molecular plane. The negative (positive) molecular g values and the molecular structure are used to give the diagonal elements in the paramagnetic-susceptibility tensor. The results are χaap = 103 (89) × 10−6, χbbp = 108 (92) × 10−6, and χccp = 217(212) ± 10−6 all in ergsG−2·mole−1. These values are compared with the recent corresponding numbers in H2CO, F2CO, H2C2O, and H2CF2. A molecular-orbital theory of paramagnetic susceptibility is employed to interpret the paramagnetic susceptibility in the H2CO, H2C2F2, F2CO, H2C2O, and H2CF2 molecules. A detailed discussion is given concerning the molecular orbitals participating in the n→π* transition in H2CO.
Mechanism of Hydrogen Formation by Electrons in x- or γ-Irradiated Gaseous HCl
Authors: Davidow R. S. , Armstrong D. A.
Published: February 2004

Studies of the effects of Cl2 and SF6 on the production of hydrogen from the x or γ radiolysis of gaseous HCl indicate that 2.5 ± 0.1 electrons per 100 eV form an intermediate Hα, which is not a thermal hydrogen atom. The remainder of the total yield of 4.0 electrons per 100 eV give rise to thermal hydrogen atoms. The results can be explained satisfactorily on the basis of the electron-capture reactions (6a) and (6c) (see text), where the sum of k6a and k6c lies in the range 5 × 10−32 to 2.6 × 10−30 ml2 molecule−2·sec−1. Hα is taken to be a clustered form of HCl− which either produces molecular hydrogen in further reactions with HCl molecules, or is scavenged by Cl2. The rate constant ratio kHα+HCl / kHα+Cl2 was 8 × 10−6 at − 77° ± 2°C and 1.2 ± 0.3 × 10−3 at 1° ± 1°C. Chlorine competes with HCl for the thermal hydrogen atoms formed in Reaction (6a) as well as for Hα, and at − 77° ± 2°C kH+HCl / kH+Cl2 was found to have a value of 2.6 ± 0.7 × 10−3, in good agreement with the data of Klein and Wolfsberg. SF6 cannot scavenge thermal hydrogen atoms and its effects are attributable entirely to a competition with HCl for electrons.
Dielectric Studies. XVI. Relaxation Processes of Some Molecules Containing the C6H4 Nucleus
Authors: Crossley J. , Hassell W. F. , Walker S.
Published: February 2004

The dielectric absorption of benzocyclobutene, 2-bromonaphthalene, o-dichlorobenzene, m-dichlorobenzene, indane, 1-methylnaphthalene, 2-methylnaphthalene, tetralin, o-xylene, and m-xylene in cyclohexane solution has been examined. All the dielectric data were analyzed in terms of a Cole-Cole distribution, and where appropriate, the data were further analyzed into contributions from two relaxation times. Tetralin at 15° and 25°C showed a nonzero distribution coefficient (α); at 50°C its α was zero and this was also the case for benzocyclobutene, indane, o-dichlorobenzene, and m-dichlorobenzene at 25°C. A short relaxation time process, together with that of molecular reorientation, contributes to the dielectric absorption of the methyl-substituted compounds and may also be present in the benzocyclobutene, indane, and tetralin solutions. The short relaxation time for the aromatic hydrocarbons may be accounted for by an intermolecular relaxation process.
Temperature Dependence of Chemiluminescent Reactions. I. Nitrogen Afterglow
Authors: Gross Rolf W. F.
Published: February 2004

Using the glow discharge shock tube recently developed in this laboratory, we measured the temperature and density dependence of the Lewis–Rayleigh afterglow between 300° and 2400°K. We also determined the absolute efficiency, i.e., the rate constant of this chemiluminescent reaction. Our results can be represented by the following expression: I = 0.60 × 10−17 (T / 300)−0.90[N]2photons / cm3·sec. The value of the integrated rate constant given includes all radiation between 500 and 700 nm.
Application of Finite Orthogonal Polynomials to the Thermal Functions of Harmonic Oscillators. I. Reduced Partition Function of Isotopic Molecules
Authors: Bigeleisen Jacob , Ishida Takanobu
Published: February 2004

The utility as well as limitations of the Taylor series expansion of the quantum-mechanical partition function of a harmonic oscillator is discussed. Finite orthogonal polynomials are suggested as a basis for the approximation of the thermodynamic functions of an assumbly of harmonic oscillators. Shifted Chebyshev polynomials of the first kind are used to obtain finite expansions of arbitrary order of the reduced partition functions of isotopic molecules. The resulting series is similar, except for modulating coefficients, term by term to the Bernoulli series obtained from the Taylor expansion. The modulating coefficients of each term in the Chebyshev expansion approach unity as the order of the expansion increases. Thus, the Chebyshev series developed here approaches the Bernoulli series asymptotically. The Chebyshev expansion converges much faster than the Bernoulli expansion. The radius of convergence can be made arbitrarily large in contrast to the limit of 2π which exists for the Bernoulli expansion. These features of the Chebyshev expansion provide a basis for the extension of the principles of isotope effects, derived from quantum corrections of order (ℏ / kT)2n, to the complete spectrum of energy states. The mathematical behavior of the modulating Chebyshev coefficients is examined. Detailed application of the Chebyshev expansion to typical polyatomic molecules is given through numerical calculations.
Infrared Spectra of Vapors, Solutions, and Crystals of Biphenylene and Biphenylene-d8
Authors: Pecile Cesare , Lunelli Bruno
Published: February 2004

The absorption spectra in the conventional and far-infrared region of biphenylene and biphenylene-d8 as a solid, as a solution and as a vapor are presented. Forced crystallization from the melt allowed us to obtain the (100) crystal plane whose spectra in polarized light were measured from 4000 to 400 cm−1. A comparison between the observed and predicted dichroism for those bands whose symmetry classes are distinguishable on the basis of the vapor spectra band contours, shows that the oriented gas model is an approximation which is more acceptable here than in other similar cases. The vibrational assignment of the 22 infrared-active fundamentals is discussed taking into account band contours, isotopic shifts, and dichroism. Only a few band splittings can be attributed to the correlation crystal field on the basis of comparison between pure oriented crystals and dilute isotopic solutions. Such effects are minor in relation to those observed in some aromatic hydrocarbons where the shortest intermolecular distances are comparable in the crystal phase.
Studies on Rydberg Orbitals. II. Calculation of the Rydberg Orbitals of Li(I)–F(I) and Their Isoelectronic Series
Authors: Hosoya Haruo
Published: February 2004

The 3s, 3p, and 3d orbitals of the atoms Li(I)–F(I) and their isoelectronic ions were calculated by optimizing the one-electron energy with the core electrons being fixed. These orbitals are for the valence states of the lowest Rydberg excited configurations, e.g., 1s22s22p3l, V2 for the C(I) series. First, the wave-functions were expanded with Slater orbitals of the least basis (3—l STO). Except for the case of 3p orbitals of the Li(I)–B(I) series, they are different from hydrogenlike expansions in that the coefficients and orbital exponents are independently optimized. Secondly, a 3l-STO was added to improve the shape of the inner loop. These Rydberg wavefunctions satisfy the following restrictions: (i) normalization, (ii) orthogonalization to the core orbitals, and (iii) cusp condition. The orbital exponents of the terms for the inner loops were set equal to the values calculated by Slater's rule for the precursors (the core orbitals of the same l with the Rydberg orbital). “Energy-optimization” and “virial-optimization” were applied separately, case by case. The results are generally good with respect to the orbital energy or quantum defect when compared to the values observed and calculated by others, the error being in the order of d ≪ p < s. Perturbations of the core by the Rydberg electron were discussed. It was revealed that for d orbitals the Slater–Condon parameters are almost constant for the different spectroscopic terms and the calculated and observed values coincide with each other, while for 3p and 3s orbitals the Slater–Condon parameters change drastically from term to term and due caution is necessary for assigning their values.
Optical Spectra of Pu in CaF2
Authors: McLaughlin R. , White R. , Edelstein N. , Conway John G.
Published: February 2004

The optical spectra of Pu3+, Pu4+, and color centers, in CaF2 have been measured. Tetravalent Pu and the color centers are formed in the crystal as the result of the decay of the Pu nucleus. Fluorescence spectra of Pu3+ and Pu4+ are also obtained.
Charge Scavenging vs Hydrogen Atom Scavenging in the Radiolysis of Liquid Saturated Hydrocarbons
Authors: Robinson M. G. , Freeman G. R.
Published: February 2004

The nitrogen and hydrogen yields from the γ radiolysis of solutions of nitrous oxide in various saturated hydrocarbons were measured. The nitrogen yields were nearly the same in all hydrocarbons, but the amounts of decrease in the hydrogen yields caused by the nitrous oxide varied markedly. The results support the suggestion that nitrous oxide reacts with electrons rather than hydrogen atoms in liquid hydrocarbons, but indicate that some nitrogen is also formed by another reaction and that all electrons do not eventually lead to hydrogen formation during the radiolysis of the pure hydrocarbon. The gaseous product yields from binary cyclohexane solutions of nitrous oxide and of propylene were subjected to kinetic analysis according to several models. It was concluded that the decrease in hydrogen yield caused by nitrous oxide and by propylene can be quantitatively interpreted in terms of interactions between the solutes and the charged intermediates. This offers an alternative to the hydrogen atom scavenging mechanism that has usually been assumed in the past for propylene. Although carbon dioxide and propylene do not attach electrons in the gas phase, they appear to do so in liquid alkanes. Propylene is a somewhat less efficient scavenger than is nitrous oxide.
Intermolecular Forces in Globular Molecules. V. Transport Collision Integrals
Authors: De Rocco A. G. , Storvick T. S. , Spurling T. H.
Published: February 2004

Collision integrals are tabulated for the spherical shell potential over a range of reduced temperatures from 0.2 to 10.0, for a range of core sizes from 1.20 to 4.0 The results are compared with those obtained for other bireciprocal potential models and the Kihara core model. Potential parameters are deduced from gas viscosity data and compared with those obtained from second virial data alone. The viscosities agree for most models over a rather wide temperature range; however, the thermal-diffusion factors show marked differences especially at low and at high temperatures.
Lattice Vibrations and Elastic Constants of Molecular Crystals in the Pair Potential Approximation
Authors: Walmsley S. H.
Published: February 2004

Expressions for lattice vibration frequencies and elastic constants of molecular crystals are developed assuming that the molecules are rigid and that the potential energy is a sum of interactions between pairs of molecules. The theory is used to calculate the elastic constants of solid carbon dioxide and the results compared with available experimental data.
Pyrolysis and Combustion of Metal Hydrides—Analysis by Kinetic Spectroscopy
Authors: Petrella R. V. , Spink T. L.
Published: February 2004

The flash-pyrolytic decomposition of AlH3 and BeH2 has been studied by kinetic spectroscopy at 2477° ± 20°K. The major dissociation product seen in the flash pyrolysis of AlH3 is AlH. The existence of a subhydride AlH2 is postulated, and its role in the pyrolytic decomposition of AlH3 is correlated to the observed species AlH. The first product seen in the flash pyrolysis of BeH2 is BeH. Within a few microseconds of the appearance, the BeH is seen to decrease in intensity. At 25 μsec after the photoflash the first bands of BeH+ are seen. From 60 μsec on, the BeH+ is the major beryllium-containing pyrolysis product. The pyrolytic decomposition of BeH2 has been observed for 165 μsec after the initial photoflash. The flash-induced combustion of BeH2 in oxygen has been studied at 20 mm pressure of the gas. The absorption spectra of OH, BeH, BeH+, and BeO are described, and the relative concentration of each is given for the period of 140 μsec following the initial photoflash. A mechanism for the combustion of BeH2 is given in terms of the spectra observed.
Diffraction Pattern and Structure of Liquid Benzene
Authors: Narten A. H.
Published: February 2004

The scattering of x rays from the free surface of liquid benzene has been analyzed at 25°C. The diffractometer used was specially designed for the study of liquid structure. Intensity and radial distribution functions have been computed for a model structure and compared to those derived from experiment. The model assumes that each benzene molecule “sees” 12 neighboring molecules in preferred orientations similar to those observed for the crystal, surrounded by a continuous distribution of distances. The intensity and radial distribution functions computed for the model are in essential agreement with those derived from experiment.
Ion Motion in Tetrafluoroborate Salts. II
Authors: Huettner D. J. , Ragle J. L. , Sherk L. , Stengle T. R. , Yeh H. J. C.
Published: February 2004

Fluorine nuclear relaxation and linewidths have been studied as a function of temperature in a series of tetrafluoroborate salts containing the following cations: ND4+, K+, Rb+, Cs+ NO+, NO2+ and Na+. Anion tumbling correlation times have been extracted from the nonexponential decays of longitudinal magnetization in the temperature region near the orthorhombic-cubic phase transition and exhibit a close relationship to the temperature T0 of the phase transition: τF(T0)∼10−10 sec. Activation energies decrease smoothly with increasing cation radius. Previously unreported phase transitions have been observed in RbBF4, CsBF4, NOBF4 and NO2BF4 at 523°, 449°, 433°, and 335°K, respectively. Room-temperature quadrupole coupling constants are reported for 11B in the alkali metal salts.
Polarization of Transitions to the Magnetic Substates of Triplet Excitons
Authors: Clarke Richard H. , Hochstrasser Robin M.
Published: February 2004

A development of the intensity relations for electronic transitions to the spin states of a molecular crystal which shows factor group splitting in its triplet levels is discussed. The relationships show that the unique polarization found in the case of the singlet Davydov states of a crystal with two molecules in the unit cell is recovered in the individual spin states of the triplet factor group levels. Experimental results consistent with our development are presented for the particular case of phenazine crystals. The singlet-triplet transition of phenazine, origin at 15 448 cm−1, is studied on the a′b crystal face in a 50 kG magnetic field directed along the b axis with light polarized parallel and perpendicular to the direction of the magnetic field.
Electric Field Gradient at a (100) Surface of Some Alkali Halide Crystals
Authors: Brown Ronald J. , Vail John M.
Published: February 2004

Given the model of Benson, Freeman, and Dempsey (BFD) for a (100) alkali halide surface, including polarization and displacement of ions, the electric field gradient (efg) is evaluated at various surface sites. The surface Mössbauer quadrupole splitting is estimated and found to be below the magnitude required to test the BFD model. However, it is found that a partial test of the model could be based on the fact that the efg for positive ion sites in the surface of KI changes sign when surface ion polarizations and displacements are taken into account.
Barrier Studies in the Halopropenes. III. Microwave Spectra, Molecular Structure, Quadrupole Coupling Constants, Orientation of the Field Gradient Tensor, and Barrier to Internal Rotation in cis-1-Chloro-2-fluoropropene
Authors: Stone R. G. , Srivastava S. L. , Flygare W. H.
Published: February 2004

The microwave spectra of cis-CH3FC:CH35Cl and cis-CH3FC:CH37Cl have been observed in the ground torsional state. The ground-state rotational constants for cis-CH3FC:CH35Cl are A = 9958.22 ± 0.05 MHz, B = 2285.88 ± 0.02 MHz, and C = 1879.89 ± 0.02 MHz. The ground-state rotational constants for cis-CH3FC:CH37Cl are A = 9958.00 ± 0.08 MHz, B = 2225.36 ± 0.03 MHz, and C = 1838.75 ± 0.03 MHz. The 35Cl quadrupole coupling constants along the appropriate inertial axes in the ground state of cis-CH3FC:CH35Cl are χaa = − 53.09 ± 0.20 MHz, χbb = + 19.45 ± 0.05 MHz, and χcc = + 33.64 ± 0.20 MHz, and for the corresponding 37Cl isotope χaa = − 41.70 ± 0.20 MHz, χbb = + 15.17 ± 0.20 MHz, and χcc = + 26.53 ± 0.20 MHz. Second-order quadrupole coupling effects have been used to obtain a direct measurement of the nonzero off-diagonal element of the χ tensor for the 35Cl species. The off-diagonal element is χab = ± 43.5 ± 3 MHz. Analysis of the ground torsional state spectra for the 35Cl species yields a barrier to internal rotation of the methyl group of 2565 ± 30 cal/mole.
Dielectric Relaxation in Isomeric Octyl Alcohols
Authors: Dannhauser Walter
Published: February 2004

The dielectric constant and loss of eight isomeric octanols has been measured over a wide range of temperature and frequency. Two distinctly different types of dispersion loci are found: For those alcohols whose –OH group is so sterically hindered that association into linear chains is unfavorable, a very small, very broad dispersion, characterized by relatively short relaxation times, is found. For less hindered species, the low-frequency, relatively slow, dispersion is Debye-like, and two high-frequency dispersion regions have been resolved in two compounds. The molar activation energies for all three dispersion regions are closely similar and τ1:τ2:τ3 ∼ 100:10:1. The activation energy for the principal (Debye-like) dispersion is strongly dependent on the steric hindrance of the –OH group. Activation energies vary from about 8 to 20 kcal so that rupture of a hydrogen bond is an unlikely rate-determining step.
Emission Spectrum of Molecular Fluorine
Authors: Porter Terence L.
Published: February 2004

The emission spectrum of fluorine has been investigated under high resolution in the region 4220-7510 Å. The spectrum was excited by means of a low-frequency, high-voltage discharge in fluorine flowing through a sapphire tube. Rotational analyses have been carried out for 21 bands in this region. Nine of these bands, together with six unanalyzed bands, are attributed to the emission spectrum of F2, primarily to the well-known orange system, C 1Σ − B 1Π. Two bands, however, are assigned to a new system, C 1Σ − B′ 1Π. The F2 spectrum is particularly characterized by extensive perturbations, affecting linewidths, intensities, and level positions. The data permit the calculation of several molecular constants and the deduction of other probable characteristics of the states involved but leave some important questions about the F2 spectrum unanswered. The rotational analyses of the 12 remaining bands was aided by the computer processing of over 2900 sharp emission lines in the region 4220-5090 Å. These bands are attributed to the A 2Π − X 2Π system of F2+, representing the first observation of the optical emission spectrum of this molecule. Several molecular constants of F2+ are also given.
Zero-Field Splittings of Am2+ and Cm3+ in Cubic Symmetry Sites in CaF2
Authors: Edelstein N. , Easley W.
Published: February 2004

The g-value anisotropies of the ground crystal-field states of the nominally S7/28 ions, Am2+ and Cm3+, have been measured in cubic symmetry in CaF2 at 35 Gc/sec and magnetic fields of approximately 5500 G by EPR spectroscopy. From the magnitude of these anisotropies the Γ6 – Γ8 zero-field splittings of 13.4 ± 0.5 and 18.6 ± 0.5 cm−1 have been deduced for Cm3+ and Am2+, respectively. These splittings are about 250 times greater than for the corresponding lanthanides, Gd3+ and Eu2+. It is shown that the large intermediate coupling effects in the actinide ions can account qualitatively for these differences.
Dynamic Nuclear Polarization (the Solid-State Effect) Associated with Asymmetric ESR Spectra in Polycrystals
Authors: Richardson Ralph J. , Jacobsmeyer Vincent P. , Lee Sook
Published: February 2004

A qualitative investigation has been made of the behavior of the dynamic nuclear polarization arising from the solid-state effect in polycrystalline substances containing paramagnetic centers for which the g and/or hyperfine tensor is substantially anisotropic. For nearly all the cases considered, the dynamic nuclear polarization and the resultant NMR enhancement will be proportional to the shape of the first derivative curve of the polycrystalline ESR spectrum. The theoretical maximum enhancement obtainable in single-crystal samples is expected to be reduced in the corresponding polycrystal samples due to the anisotropy in the g and/or hyperfine tensor. Experiments were carried out to measure 23Na NMR enhancements in powdered NaCl crystals by staturating the Cl2−(Vk) ESR spectrum, and the experimental results were found to be in good agreement with the prediction.
Nuclear Magnetic Resonance Relaxation in 1-Propanol
Authors: Drake P. W. , Pridham R. , Meister R.
Published: February 2004

The NMR spin–lattice and spin–spin relaxation times have been measured in 1-propanol at the resonant frequency of 20 Mc/sec and over the temperature range from − 130° to + 25°C using “spin-echo” techniques. Average nuclear correlation times were obtained using log-Gaussian distribution of correlation times. The distribution of correlation times was found to have a width parameter which varied from b = 0.33 to b = 0.36 over the temperature range observed. Both magnitude and the required distribution of nuclear relaxation times support the proposal that the nuclear relaxation is more closely associated with the mechanical relaxation process. The ratios of ̄τD′ / ̄τnc and ̄τnc / ̄τ8 are observed to be temperature dependent and this temperature dependence is discussed in terms of a difference in the required critical local free volume for the three processes.
Ion–Molecule Reactions of Negative Ions. I. Negative Ions of Sulfur
Authors: Dillard John G. , Franklin J. L.
Published: February 2004

Negative ions from carbonyl sulfide and carbon disulfide have been studied in a time-of-flight mass spectrometer. The principal ions formed by dissociative resonance electron capture in carbonyl sulfide are S− and O−. Those from carbon disulfide are S− and CS−. The onset for the formation of S− by a resonance capture process has been found to occur at 1.2 eV from carbonyl sulfide, and the translational energy of the resulting ion has been found to be approximately 0.04 eV. ΔHf(S−) is thus found to be 20 kcal/mole in agreement with previous values. At pressures of several microns in the source, secondary ions are formed in both carbonyl sulfide and carbon disulfide. In the electron capture region the principal secondary ion is S2−, formed by reaction of S− with the corresponding parent molecule. At higher electron energies where greater ion intensities are observed, ions of the general formula Sn− are formed with n varying from 2 to 6. These must result from sequential reactions of Sn−1− with the parent molecule. An important ion in the high-pressure spectrum of carbon disulfide is CS2−, presumably formed by charge transfer. The rate constant from the reaction of S− with COS is about 3.0 × 10−10 cc/molecule·sec.
Equilibrium Line between Ice I and III
Authors: Kell G. S. , Whalley E.
Published: February 2004

The equilibrium line between ice I and III has been reinvestigated in an attempt to verify an order-disorder transformation in ice III that has been inferred from the reported curvature of the I-III line. The line is in fact nearly straight, and previous measurements indicating that it is curved are wrong. There is therefore no order-disorder transformation in ice III above − 61.9°C.
Dynamic Polarization in Solutions of Sodium in Liquid Ammonia
Authors: Lambert C.
Published: February 2004

Dynamic polarization experiments have been carried out in dilute solutions of sodium in liquid ammonia (mole ratio R > 130) at room temperature in a magnetic field of 3.3 kG. A positive Overhauser enhancement corresponding to a leakage factor of 0.5 was measured for 14N, showing an important relaxation process due to the hyperfine interaction with electrons. The paramegnetic shift of 14N was measured in a direct way, and the results are in agreement with those of other authors. Overhauser shift measurements were performed for 14N and H; an experimental proof of a negative spin density at the proton was thus obtained.
Dependence of the Time-Correlation Functions of Molecular Random Motions on the Intermolecular Potential
Authors: Shimizu H.
Published: February 2004

A general theory on the time-correlation function and the spectral density for the random motion in molecular system is presented. We study the dependence of these functions on the intermolecular potential and on the rate of fluctuation of the potential. It is shown that the fluctuating intermolecular interactions or potentials not only introduce the randomness to molecular motion but also characterize important details of the randomness. Here we assume that the fluctuation can be regarded as a Gaussian random process contributed from the perturbers around the molecule. Therefore, the theory may be applied to the molecular motions in the liquid state. As an example of application of the present theory we discuss the collapse of multiplet structure in magnetic resonance spectrum of two-spin system; Anderson's results for the exchange narrowing of spectrum is derived as a special case of our formulation. The correlation functions and the spectral densities for the random reorientation of diatomic molecules are studied quantum mechanically as second example of application. Graphical presentations are given for the dependence of these functions on the intermolecular potential. The shape of vibrational spectra of molecules can be thus analyzed quantitatively by using the present theory.
Magnetic Resonance Studies on Irradiated Crystals of Chloroacetyl dl-Alanine
Authors: Wells James W. , Box Harold C.
Published: February 2004

The rotation of the methyl group in the free radical ClCH2–CONH–C(CH3) COOH was studied by ESR and ENDOR spectroscopy. The results are analyzed using a quantum-mechanical hindered rotor model with Mathieu functions as basis functions. The experimental results indicate a barrier height of less than 0.5 kcal/mole.
Theory of Zeeman Effect for Rare-Earth Ions in Crystal Field with C3h Symmetry. III
Authors: Syme R. W. G. , Haas W. J. , Spedding F. H. , Good R. H.
Published: February 2004

An analysis is made of several strikingly regular Zeeman patterns which have been observed in the optical absorption spectrum of erbium ions in ethylsulfate crystals. In the experiments the magnetic field was applied in the basal plane, and the light was shone in perpendicular to both the c axis and the magnetic field. It was polarized either in the direction of the c axis or the magnetic field. The spectra were observed as a function of orientation of the crystal about the c axis. In most of the Zeeman patterns there is a complicated dependence of the frequencies and intensities of the lines on the crystal orientation. In the three special cases analyzed here the frequencies are independent of orientation and the intensities are constant or vary in a sixfold way. It is shown that the energies and intensities of these patterns can be well understood by restricting the Zeeman contribution to the rare-earth-ion Hamiltonian to interaction within a small set of crystal-field states in the appropriate multiplet. This is a reasonable approximation to make for the transitions studied because the particular energy levels involved remain isolated from the others throughout the range of magnetic-field strengths used (H < 30 kG). Comparison of the theoretical and experimental results determines some of the parameters in the calculation and provides new information about the odd-parity part of the C3h environment of Er3+ in the ethylsulfate lattice. In particular, the results suggest that the major contribution to the departure from effective D3h symmetry at the rare-earth-ion site is provided by the Y3±3 terms in the crystal-field expansion rather than by Y5±3 and Y7±3 terms.
Determination of the Rate Constant of the Gas-Phase Reaction between O(1D) and CO2
Authors: Clerc Michel , Reiffsteck André
Published: February 2004

From the measurement of the amount of O3 produced by vacuum-uv` flash photolysis of O2−Ar mixtures to which either CO2 or CO is added, a value of the ratio k5 / k3 = 55 ± 5 has been determined for the reactions O(1D) + CO2→CO3, O(1D) + CO→CO2. The results provide indirect evidence for the occurrence of Reaction (3) instead of Reaction (4), O(1D) + CO2→O(3P) + CO2.