bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum Calculations of the Velocity Dependence of the Differential and Total Cross Sections for Elastic Scattering of Molecular Beams
Authors: Bernstein Richard B.
Published: January 2005

The partial wave treatment (phase shift analysis) of the elastic scattering of molecular beams [J. Chem. Phys. 33, 795 (1960)] is applied to the calculation of the velocity dependence of the differential and total cross sections for an assumed L-J (12, 6) potential. For most of the calculations, the ε, σ values are chosen to correspond to the H2–Hg system. The range of the velocity parameter A≡kσ=μvσ/ℏ is from 3 to 30; this is equivalent to a 100-fold variation in H2 beam temperature (approx 8.2–820°K). Computations of the angular distribution of the scattering dσ(θ)/dΩ and the total cross section Q as a function of A are reported. A correlation of the interference maxima in dσ(θ)/dΩ is presented. The Massey-Mohr approximation for Q(A) for an inverse sixth-power attractive potential is compared with the present calculations for the L-J (12, 6) potential. Significant undulatory deviations are noted at low A; this effect is attributed to the existence of the broad maximum in the phase shift curve η(l), which, in turn, originates from the negative repulsive phases at low l. Consideration is given to the question of the sensitivity of the scattering to the repulsive part of the potential.
Spectroscopy of Fluorine Flames. I. Hydrogen-Fluorine Flame and the Vibration-Rotation Emission Spectrum of HF
Authors: Mann D. E. , Thrush B. A. , Lide D. R. , Ball J. J. , Acquista N.
Published: January 2005

The hydrogen fluoride vibration-rotation emission spectrum from a hydrogen-fluorine diffusion flame has been studied under high dispersion from 3200 cm−1 in the infrared to about 5500 A in the visible. Measurements were made on the rotational lines in 23 bands including (1–0), (2–1), and (3–2) of the Δv=1 sequence; (2–0), (3–1), (4–2), (5–3), and (6–4) of Δv=2; (3–0), (4–1), (5–2), and (6–3) of Δv=3; (4–0), (5–1), (6–2), (7–3), (8–4), and (9–5) of Δv=4; and (5–0), (6–1), (7–2), (8–3), and (9–4) of Δv=5. Complete rotational and vibrational analyses were carried out. The constants Bv, Dv, and Hv are given for v=0 to 9. The data were extensive and precise enough to warrant an extended Dunham treatment from which 18 coefficients could be determined, including those for terms in (v+½)5 and J4(J+1)4. Band centers for 22 bands and the vibrational term values Ev for v=0 to 9 are given.
Quasi-Lattice Model of Reciprocal Salt Systems. A Generalized Calculation
Authors: Blander Milton
Published: January 2005

A generalized statistical-mechanical calculation of the solution thermodynamics of the reciprocal molten salt system A+, B+, C−, and D− dilute in A+ ions has been made. The calculation is based on the quasi-lattice model of reciprocal salt systems and treats the problem as an order-disorder problem. Associations of the A+ and C− ions as A++C−⇌ACAC+C−⇌AC2−AC2−+C−⇌AC3=are taken into account. In terms of the conventional equilibrium constants K1, K2, and K3 for (A), (B), and (C), respectively, K1=Z(β1−1)K1K2=Z(Z−1)2!(β1β2−2β1+1)K1K2K3=Z(Z−1)(Z−2)3!(β1β2β3−3β1β2+3β1−1),where Z is the quasi-lattice coordination number, βj=exp(—ΔAj/kT) and ΔAj may be termed a specific bond free energy of the jth C− ion and is the specific Helmholtz free energy change for the formation of the jth bond. Equations (1), (2), and (3) demonstrate the surprising fact that the higher order association constants are dependent on the magnitude of the lower order association constants not only through the factor containing Z but also through the values of the βi for the lower association constants. If β1=β2=β3=··· etc., the equations reduce to the statistical ratios of Bjerrum. The higher association constants can be shown to be smaller for a case in which the bonding is directional (e.g., linear AC2−), than if they are nondirectional, as in Eqs. (2) and (3), even if the bond free energies are equal in the two cases.
Effect of Solvent and Solute Structure on Scintillator Pulse Heights. II. Correlation of Pulse Heights for Aromatic Liquid Organic Scintillators with Hammett Substituent Constants
Authors: Sandler Stanley R. , Loshaek Samuel
Published: January 2005

It has been found that numerous data in the literature on aromatic organic liquid scintillators could be interpreted in terms of the resonance and polarity of the constituent solvents and fluors. The resonance and polarity of the ring substituted aromatic compounds were characterized quantitatively by Hammett substituent constants (δ). For a number of liquid scintillator systems in which the fluor composition was kept constant and the structure of the aromatic solvent was varied, pulse heights increased approximately linearly with increasing electron donating (negative δ values) power of the substituents on the aromatic molecule. This correlation held for nine different fluors in each of seven different aromatic solvents. A similar correlation was found for a series of fluors consisting of substituted 2,5-diphenyl-1,3,4-oxadiazoles and 2,5-diphenyl 1,3-oxazoles in which toluene was used as the sole solvent. Pulse heights varied much more with a change in substituent groups on the solvent than with a similar change in the fluors. The observed correlation affords a means of organizing a large body of data and of gaining a further insight into the mechanism of scintillation.
Mean Free Path and Ultrasonic Vibrational Relaxation in Liquids and Dense Gases
Authors: Madigosky W. M. , Litovitz T. A.
Published: January 2005

Measurements of ultrasonic absorption and velocity in CO2 yielded values of the vibrational relaxation times over a range of densities from 400 to 610 amagats at 25°C and 50.2°C. On the basis that only binary collisions are important it is found that the Enskog theory for determining collision times in the dense fluid failed to account for the results. Application of the Eyring-Hirschfelder cell model of the liquid accounted well for the density dependence of the relaxation frequency but gave values of mean free path which were too large. It is proposed that for mean free path calculations a realistic cell model must not use fixed walls as the Eyring and Hirschfelder model does but rather moving walls. When this modification is included excellent agreement is obtained for both CO2 and CS2. It is further shown that attractive forces do not play the role in determining the collision efficiencies in a liquid or dense gas that they do in the dilute gas. After correcting for the reduced effect of attractive forces, it is found that the collision efficiencies for the dilute gas agree with values obtained for the liquid and dense gas.
Infrared Spectrum of Co(CO)3NO
Authors: McDowell Robin S. , Horrocks W. D. , Yates John T.
Published: January 2005

The infrared spectra of Co(CO)3N14O and Co(CO)3N15O vapor are reported from 10 000 to 280 cm−1 and all fundamentals assigned. The two C–O stretches and the N–O stretch are at 2108, 2047, and 1822 cm−1, respectively. Exchange with C13O indicates that a strong band at 2010 cm−1 is due to the C13–O stretch of the isotopic species Co(CO)2(C13O)NO. A normal coordinate treatment has been carried out, and the force constants determined.
Origin of the Green Bands in the Boron-Oxygen System
Authors: Kaskan W. E. , Mackenzie J. D. , Millikan R. C.
Published: January 2005

A study has been made of the effect of oxygen on the intensity of absorption in the green or ``fluctuation'' bands by the gas phase in equilibrium with B2O3(l). The reaction which forms the substance responsible for the bands from B2O3(l) in the presence of oxygen was found to be 70 kcal/mole endothermic, in the range 1660–1950°K, in agreement with other work. At constant temperature the absorptivity was found to depend on the ¼ power of the oxygen pressure. This is interpreted as evidence that the absorbing species is BO2. The oscillator strength of the transition is estimated as 0.003.
Stabilities of Gaseous Molecules in the Pb–Se and Pb–Te Systems
Authors: Porter Richard F.
Published: January 2005

Mass spectrometric analyses of the vaporization products of phases near compositions PbSe and PbTe indicate that these substances vaporize primarily as molecular PbSe(g) and PbTe(g), respectively. Ion fragmentation processes originating from electron bombardment of vapors effusing from a conventional Knudsen cell interfere with quantitative determination of thermochemical dissociation energies of PbSe(g) and PbTe(g). The use of double oven-type Knudsen cells provided a means for the study of the dissociation of PbSe(g) and PbTe(g) into the gaseous elements. Dissociation energies of PbSe(g) and PbTe(g) were found to be 61.5±2.5 and 51.4±2.0 kcal/mole, respectively. The dissociation energy of Te2(g) was found to lie close to the published spectroscopic value.
Infrared Spectrum of Lithium Fluoride Monomer by Matrix Isolation
Authors: Linevsky Milton J.
Published: January 2005

A method has been developed which can be used to observe the infrared spectrum of high temperature vapors. It combines the techniques of matrix isolation with that of Knudsen effusion. The infrared spectrum of matrix isolated lithium fluoride has been observed in argon, krypton, xenon, and nitrogen matrices. The observed frequencies in the various matrix materials are shifted approximately 7% to 14% from the measured gas fundamental at 900 cm−1. These shifts can be explained by the interactions of the trapped molecule with its surrounding neighbors, based on a model which estimates the change in magnitude of the electrostatic, inductive, and dispersive interactions during the course of a molecular vibration. These effects are particularly large in lithium fluoride due to its sizable dipole moment.
Time Spectra of Positrons Annihilating in Organic Liquids Containing Halogens
Authors: Ormrod J. H. , Hogg B. G.
Published: January 2005

Measurements have been made of the mean life τ2, and the percent I2, of positrons forming triplet positronium in propyl halides and in benzene-carbon tetrachloride solutions. The experimental variations of I2 in the propyl halides can be predicted assuming a semiempirical equation of the form 100–4/3I2=AN1+2.4N2, where A is the annihilation factor of the parent molecule and N1 and N2 are the percent volumes of the parent and halide, respectively. A equal to 0.36 is needed for the propyl parent. This equation also predicts correctly the experimental values for the benzyl halides if A equal to 0.53 is used as the benzyl annihilation factor. The quenching of I2 in the benzene-carbon tetrachloride solutions is much greater than that computed by the equation and the variation in quenching closely resembles that obtained in aqueous nitrate-ion solutions.
Evaluation of Electrostatic Energy Levels of f6
Authors: Gruber John B. , Conway John G.
Published: January 2005

The 119 electrostatic energy levels for an nf6 configuration have been calculated for three different sets of Slater Fk ratios: 4f6 hydrogenic—F4/F2=0.1381, F6/F2=0.01511; 5f6 hydrogenic—F4/F2=0.1422, F6/F2=0.0161; and 5f6 based on a Hartree-Fock calculation for the normal uranium atom—F4/F2=0.159, and F6/F2=0.0204. A tentative theoretical analysis of the absorption spectra of Eu IV can be made by using ζ=1360 cm−1 and F2=370 cm−1. The results of our work show clearly that the intermediate field matrices are essential to a quantitative analysis of the Eu IV and Am IV spectra, and that Zeeman studies are needed to identify certain levels.
Concentration Dependence of NMR Spin-Lattice Relaxation Times in Solutions
Authors: Mitchell R. W. , Eisner M.
Published: January 2005

Spin-lattice relaxation times for protons in benzene, cyclohexane, chlorobenzene, bromobenzene, and o-dichlorobenzene in solution with carbon tetrachloride and carbon disulfide are empirically fitted to theoretical curves based on the Hill and molecular sphere models of molecular motion. The results indicate that the Hill model properly accounts for the variation of both the rotational and translational relaxation times with concentration of solute.
Cation-Electron Interaction in Metal-Ammonia Solutions
Authors: Jortner J.
Published: January 2005

The problem of electron binding in the field of a cation in metal solutions is treated on the basis of an interstitial ion model. The energy levels and charge distribution of the unpaired electron are computed by a self-consistent field treatment for electron binding in a continuous dielectric medium employing one parameter wave function. Comparison with experimental results and with theoretical treatment based on a molecular model is presented. The adequacy of the continuous model is discussed.
Bonding in Cubic Complexes
Authors: Macek Joseph H. , Duffey George H.
Published: January 2005

Symmetry arguments yield the general spdf σ bond orbitals for A in cubic AB8. The valence orbitals needed include 1s, 3np, 3d, and (4–3n)f. The greatest strength, 3.934, is found when n is 27/55. Incomplete hybridization, splitting of valence levels of A, and π bonding in a cubic field are also discussed.
Nuclear Relaxation Processes of a Nonequivalent Two-Spin System
Authors: Shimizu Hiroshi , Fujiwara Shizuo
Published: January 2005

Nuclear magnetic relaxation of a two-spin system is discussed using Redfield's semiclassical formulation of the relaxation processes. Time dependences of longitudinal magnetizations are given as a function of the ratio J/δν0. An expression for the nuclear induction signal is given, from which the expected shape of multiplet lines and their behaviors upon saturation under various origins of the relaxation are discussed in detail. The discussion leads to the conclusion that the mechanism of nuclear relaxation can be determined by carefully analyzing the spin multiplet lines on the basis of the theory. Finally, it is shown that there is a possibility of finding the absolute sign of the spin-spin coupling constant in a two-spin system using the multiple resonance method.
Calculation of Pressure Shifts of Optical Absorption Spectra from Solvent Data
Authors: Robertson W. W. , King A. D.
Published: January 2005

Frequency shifts in the absorption spectra of both polar and nonpolar absorbers have been observed at atmospheric pressure in a range of polar and nonpolar solvents and in pentane and ethanol under hydrostatic pressures up to 5000 atm. McRae's equation representing frequency shifts in terms of solvent refractive index and dielectric constant can be modified by the use of the Debye equation to represent frequency shifts in terms of solvent density. If it is assumed that the volume of the cavity occupied by the absorber remains constant with solvent density, frequency shifts resulting from an increase in hydrostatic pressure can be calculated almost to within the limit of experimental error from solvent shift data.
Ionization Processes in CCl4 and SF6 by Electron Beams
Authors: Fox R. E. , Curran R. K.
Published: January 2005

The ionization processes in CCl4 and SF6 have been studied for both positive and negative ions in a mass spectrometer, and in a total ionization tube. The appearance potential of Cl− is 0+0.05 ev with a very sharp energy dependence. A second process with an onset at about 0.4 ev and a maximum at about 0.7 ev, exhibits a much broader energy dependence. The relative intensities of these two processes are found to be extremely sensitive to the energy distribution of the electron beam, but do not appear to exhibit a temperature dependence. From the appearance potentials and kinetic energy measurements of Cl− a value of 3.30±0.07 ev is obtained for D(CCl3–Cl). The appearance potential curves for CCl3+ and SF5+ near threshold indicate structure which may be associated with energy states of these ions.
The State of the Nd3+ Ion as Derived from the Absorption and Fluorescence Spectra of NdCl3 and Their Zeeman Effects
Authors: Carlson E. H. , Dieke G. H.
Published: January 2005

The absorption and fluorescence spectra of Nd3+ in NdCl3 diluted by LaCl3 have been examined with their Zeeman effect at 4.2° and less completely also at 77°K. The empirical energy-level diagram is complete up to 28 000 cm−1 except for the location of the 2K term. Crystal Stark splittings, magnetic properties, and intensities are compared to calculated values obtained from an intermediate coupling calculation of the 4f3 configuration.
Polarity of the C–H Bonds in Acetylene and Its Molecular Quadrupole Moment
Authors: Hamano H.
Published: January 2005

By using the molecular quadrupole moment data of acetylene, the polarity and the dipole moment of the CH bonds have been investigated. The semiempirical LCBO MO method was applied to this problem. The results obtained show that the CH bonds in this molecule are almost homopolar, but hydrogen is slightly positive in polarity. From this, the so-called bond moment and the infrared bond moment have been discussed. The sign of the molecular quadrupole moment of acetylene which cannot be given by the experimental data was determined as positive in the present work.
Temperature Dependence of NMR Absorption in Solid Acetic Acid and in Some of Its Chloro and Acid Chloride Derivatives
Authors: Peterlin A. , Pintar M.
Published: January 2005

Acetic acid and some of its chloro and acid chloride derivatives with increased substitution of protons by chlorine in the CH3-group were studied by NMR from −175°—0°C in order to elucidate the temperature dependence of molecular and CHnCl3−n group mobility and association in the solid state. While CH3 is free to rotate around the C–C bond, the substitution of one proton by chlorine already results in fixed CH2Cl group. In order to obtain dimeric association, however, one has to substitute two or all protons by chlorine. The rotational freedom of single molecules of such associates reappears upon heating to temperatures far below the melting point.
Effect of Several Light Molecules on the Vibrational Relaxation Time of Oxygen
Authors: Parker J. G.
Published: January 2005

Measurements of vibrational relaxation times of O2–H2, O2-D2, and O2–He mixtures have been carried out by means of an acoustic resonance tube. It was found that all these light elements shorten the vibrational relaxation time of oxygen with H2 being by far the most effective. Surprisingly, D2 and He produced almost identical effects, indicating that molecular mass is the dominating factor in the ability of these gases to excite vibration in O2. Results of these measurements show that an O2–H2 collision is 2.96×103, an O2-D2 collision 2.96×102, and an O2–He collision is 3.53×102 more effective than an O2–O2 collision. Most extensively studied was O2–H2, for which relaxation times were measured in eight different mixtures, the maximum concentration of H2 being 2.64% and the minimum 0.072%. Variation of the relaxation frequency with H2 concentration was linear, indicating that binary collisions alone are important. Extrapolation of this data to zero concentration gives a relaxation time for pure O2 of approximately 1.8×10−2 sec which is considerably longer than that obtained by other investigators. Comparison of the experimental data with theory suggests that the variation of intermolecular forces in the interaction of light elements with oxygen is much less steep than one would predict from a knowledge of the interaction forces in the separate similar interactions.
Theoretical Investigations on the Light Scattering of Colloidal Spheres. XI. Determination of Size Distribution Curves from Spectra of the Scattering Ratio or from Depolarization Spectra
Authors: Stevenson Arthur F. , Heller Wilfried , Wallach Morton L.
Published: January 2005

The theory of a method is developed by means of which size distributions in heterodisperse systems of colloidal and small microscopic spheres can be determined from spectra of the scattering ratio or depolarization. The method is applicable whenever the distribution is unimodal, positively skewed, and of the type most commonly found in emulsions. It makes use of the Mie-scattering functions and encompasses α values up to 25.2 (diameters up to 3.3 μ if the vacuum wavelength is 5460.73 A) and the relative refractive indices m=1.05 (0.05) 1.30. The method yields the mean number or weight average diameter, modal diameter, half-width, and ``half-spread'' of a distribution and, in addition, the diameter of the smallest particles present in consequential numbers. For those instances where the assumed type of distribution does not apply, an extension of the theory is provided which is based upon a linear combination of two distribution functions of the same type. It allows one, in principle, to consider also negatively skewed and bimodal distributions. Use of the linear combination is indicated only when failure to obtain a satisfactory fit between theoretical and experimental spectra shows nonvalidity, in a particular system, of the simple one-term distribution function.
Field Emission from Whiskers
Authors: Melmed A. J. , Gomer R.
Published: January 2005

A method for obtaining field emission from whiskers grown in situ from the vapor under high-vacuum conditions has been developed and is described. It is possible to fabricate clean and strong emitters from almost any conducting material, so that the range of substances that can be used for field emission has been considerably expanded. Electrical methods for following the growth kinetics and determining whisker length and radius are described and applied to Au. Growth is found to be positively exponential with time, which supports a mechanism of growth by diffusion of impinging atoms over the whisker sides and incorporation at the growing end. Cessation of growth is diffusion limited in these experiments. It was possible to estimate the activation energy for the surface diffusion of Au on Au as 23±5 kcal from the variation of terminal length with temperature. Some adsorption and oxidation experiments indicate that the method can also be used for the study of these phenomena. It was found for instance that H2 is not adsorbed on Au and that Al is oxidized with severe surface rearrangement even at 77°K.
Proton Magnetic Resonance Studies of Polycrystalline Uranium Oxide Hydrates. II. β-UO3H2O
Authors: Porte A. L. , Gutowsky H. S. , Boggs J. E.
Published: January 2005

The broad-line proton magnetic resonance spectra of polycrystalline samples of the compound formulated empirically as β-UO3H2O have been examined in the temperature range 77°—370°K. Analysis of the spectrum at 77°K shows that the compound is uranyl hydroxide UO2(OH)2. The interrelationships between the different phases in the uranium-trioxide—water system which involve the β-modifications of the ``uranium trioxide hydrates'' are discussed.
Cluster Theory of Saturated Vapor of Helium-Isotope Mixtures
Authors: Adams Richard O. , Band William , Ingram Glenn R. , Perry Clay L.
Published: January 2005

The quantum statistical cluster model of the saturated vapor of mixtures of helium isotopes He3 and He4 has been subjected to a program on an electronic digital computer. The results permit a prediction of the saturated-vapor density as a function of the mixture concentration for each of the isotherms given by experimental data on the saturated-vapor pressure of the same mixtures.
Dissociation of Halogens in Shock Waves
Authors: Hiraoka Hiroyuki , Hardwick R.
Published: January 2005

The rate of dissociation of Cl2 has been measured at high temperatures in a shock tube. The temperature dependence curves, regardless of Cl2 concentration, are fitted by invoking 4° of freedom of internal motion and an activation energy of 48 kcal.

From the temperature TH at which the decrease of Cl2 optical density through dissociation matches the increase due to the cooling, by reaction enthalpy, the dissociation energy of Cl2 has been calculated. The agreement with the well-known spectroscopic value gives a confirmation of the shock-tube temperature measurements and of many assumptions made in the other calculations.
On the Vapor Pressure of Electrically Charged Droplets
Authors: Gallily Isaiah , Ailam (Volinez) Gedalia
Published: January 2005

A general expression is derived for the vapor pressure of a charged drop situated at the center of a spherical container with perfectly reflecting wall. It is assumed that the liquid is conducting, the medium devoid of external fields of force and that the gaseous phase comprises both neutral and charged molecules. The vapor pressure in the case where the radius of the container is close to that of the drop was evaluated after solving the equation for the distribution of the charged molecules near the surface.

It was shown that, in general, the vapor pressure tends to infinity with increasing distance from the droplet, thus rendering impossible the attainment of a thermodynamic equilibrium in the atmosphere. The vapor pressure of a charged mercury droplet is given as a numerical example.
Hyperfine Interactions in X-Irradiated Magnesium Phosphite Hexahydrate
Authors: Hanna Melvin W. , Altman Larry J.
Published: January 2005

An analysis of the electron spin resonance spectra of X-irradiated single crystals of MgHPO3·6H2O has shown that the principal long-lived paramagnetic species produced by irradiation is a PO3 fragment. This fragment retains the same orientation within the unit cell as the undamaged molecule. The parallel and perpendicular components of the diagonal (electron-spin) — (nuclear-spin) coupling dyadic for the phosphorus nucleus are found to be of the same sign and of magnitude 2210 and 1730 Mc, respectively. These results are compared with theoretical values of the distributed dipole and contact hyperfine interactions calculated on the assumption that the unpaired electron is located in an sp3 hybrid orbital centered on phosphorus.
Vibrational Distribution in Evaporating Iodine
Authors: Brown Robert L. , Brewer Richard G. , Klemperer William
Published: January 2005

The vibrational distribution of iodine molecules evaporating from solid iodine has been measured by means of their visible absorption spectrum. Within the experimental error a Boltzmann distribution with a temperature equal to that of the crystal was observed.
Higher-Order Rotation-Vibration Energies of Polyatomic Molecules. V
Authors: Amat Gilbert , Nielsen Harald H.
Published: January 2005

The Schrödinger equation for the energies of a rotating-vibrating polyatomic molecule is not exactly soluable. The common procedure is to expand the Hamiltonian for the problem in orders of magnitude, the parameter of smallness being of the order of (Be(αα)/ωs)½, where Be(αα) is a rotational constant and ωs is a vibration frequency, and to arrive at energy expressions by successive approximations.

The actual order of magnitude of a term in the Hamiltonian will depend upon the values of (Be(αα)/ωs) and the values of the rotational quantum numbers relative to the vibration quantum numbers. One may, therefore, use different expansions for the quantum mechanical Hamiltonian corresponding to the values of J and K taken under consideration, in which case the ``index'' of magnitude of the matrix element of an operator O belonging to the Hamiltonian operator hm, expansion for the Hamiltonian H as has been done by Goldsmith et al., whatever the values of the quantum numbers may be, accepting then that the true ``index'' of magnitude is not necessarily equal to m.

Adopting the latter scheme and using the expansion of the Hamiltonian proposed by Goldsmith et al. the contributions to the energy of the various terms comprising it are considered for various ranges of J and K and an assignment of the order of magnitude to which the contribution belongs is made.
Vibronic and Rotational Energy Levels of a Linear Triatomic Molecule in a 3Π Electronic State
Authors: Hougen Jon T.
Published: January 2005

Expressions are presented for the vibronic and rotational energy levels of a linear triatomic molecule in a 3Π electronic state which take into account spin-orbit and vibronic (Renner) interactions. The results are valid when both interactions are small compared to the frequency of the bending vibration. It is shown that the vibronic energy levels can be divided into two sets, such that the energies of one set are like those of the vibronic states of a 1Π electronic state, whereas the energies of the other set are like those of the vibronic states of a 2Π electronic state. Some similarities and differences between the expressions for the rotational energy levels presented here and the corresponding expressions for diatomic molecules are discussed.
Coupled Anharmonic Vibrations and Spectral Line Broadening
Authors: Mazo Robert M.
Published: January 2005

It is pointed out that some numerically important terms were omitted in the approximate solution of the differential equations of the model proposed by Frisch and Vidale for broadening of spectral lines in hydrogen bonded systems. An improved estimate of the broadening is presented. With the parameters of Frisch and Vidale, as corrected by McDowell, the improved estimate for the frequency width is 625 cm−1.
Magnetic-Resonance Studies of Lithium Vanadium Bronze
Authors: Gendell Julien , Cotts R. M. , Sienko M. J.
Published: January 2005

The nuclear magnetic resonance of Li7 in LixV2O5 shows no Knight shift, but there is a small diamagnetic shift relative to LiCl solution, amounting to 0.0023 and 0.0058% at 296° and 77°K, respectively. The spin—lattice relaxation time T1 as measured by pulse experiments, decreases from 0.16 sec at 296°K to a minimum of 0.060 sec at 163°K and then rises to 0.13 sec at 77°K. The free-induction decay half-width decreases from 850 μsec at 296°K to 100 μsec at 77°K. The minimum in T1 is attributed to back-and-forth motion of the lithium ions within but normal to the axis of channels in the oxygen framework; the line narrowing, to diffusion along the channel from one unit cell to an adjacent one. EPR studies give Lorentzian-shaped lines, centered at g=1.96, of intensity proportional to 1/T. Results are consistent with a model in which lithium atoms in a host V2O5 structure are completely ionized to give Li+ ions and electrons which are almost, but not completely, localized as V4+ centers.
Effects of Electronic Exchange on the Efficiency of Vibrational Excitation by Molecular Collisions. Part I. Interaction Potential
Authors: Korobkin I. , Slawsky Z. I.
Published: January 2005

A theoretical study has been made of the mechanism for the transfer of molecule translational energy into the internal energy of vibration by molecular collisions. In particular, the research considered the interaction between molecules which can combine chemically to form a covalent bond. Previous theoretical treatments using a Lennard-Jones type of interaction potential resulted in calculated efficiencies which were low by several orders of magnitude for the vibrational excitation process. A stable covalent bond is formed by the sharing of electrons, i.e., electronic exchange, between the various atoms in a molecule. The concept of electronic exchange was used in determining a more realistic interaction potential then the Lennard-Jones for a typical case, namely, the collision of a proton and a diatomic hydrogen molecule which can combine to form a stable molecule ion. The resulting interaction potential was entirely of negative energy as opposed to the Lennard—Jones which is of positive energy and strongly repulsive for small separation distances between the colliding particles. Furthermore, the depth of the potential well with electronic exchange was about 2 eV compared to Lennard-Jones well depths of about 0.01 eV. In addition, the equilibrium separation between the nuclei of the hydrogen molecule increased to 2½ times the normal value as the proton approached, and the spring constant of the molecule as a vibrator decreased to less than ⅕ the normal value. The above results all tend to increase the ease of vibrational excitation and should result in higher excitation efficiencies.
Proton Shielding in Diborane
Authors: Kern C. William , Lipscomb William N.
Published: January 2005

The chemical shift of the bridge proton relative to the terminal proton in diborane is discussed in several approximations based on Pople's and on Ramsey's atomic and molecular theories of magnetic shielding, respectively. The analysis, which depends on Yamazaki's 12-electron SCF LC—STO MO wave function, gives the result, generally observed in the H1 NMR spectra of the higher hydrides, that the bridge protons show resonance at higher fields than do the BH2 terminal ones.
Proton Chemical Shift in HCo(CO)4
Authors: Stevens Richard M. , Kern C. William , Lipscomb William N.
Published: January 2005

The anomalous high-field chemical shift observed in general for H bonded to a heavy metal has been calculated in the localized diatomic approximation for the CoH bond in HCo(CO)4 with the use of the theory of Kern and Lipscomb, valid for a light atom bonded to a heavy atom. It is shown for the first time that reasonable agreement with experiment is obtainable at a bond distance corresponding to a normal covalent bond, and that, aside from the electron around H, the major contribution to the high-field shift comes from the electron populations in the large and diffuse 4s and 4p orbitals of Co.
Rotational Isomerism and Microwave Spectroscopy. I. The Microwave Spectrum of Normal Propyl Fluoride
Authors: Hirota Eizi
Published: January 2005

The normal propyl fluoride molecule has been confirmed by microwave spectroscopy to exist in two rotational isomers, trans and gauche. Rotational constants in the ground vibrational state are A = 26 986.73, B = 3748.32, C = 3509.88 Mc/sec for the trans form and A = 14 503.69, B = 5085.71, C = 4295.28 Mc/sec for the gauche form. The dihedral angle of the gauche form is about 63° from the cis position.

The barrier height hindering methyl rotation has been determined, using lines in the first excited state of methyl rotation, to be 2.69 kcal/mole and 2.87 kcal/mole for the trans and the gauche forms, respectively. The dipole moment and its components along the principal axes have been determined by the Stark effect: μa = 1.970±0.026, μb = 0.566±0.064, μtotal = 2.050±0.043D for the trans form and μa = 1.137±0.008, μb = 1.450±0.033, μc = 0.472±0.137, μtotal = 1.902±0.064 D for the gauche form. The total dipole moment is nearly parallel to the C–F bond for both forms; the angle between them is 10.6° in the trans form and 7.4° in the gauche form.

The intensities of satellites due to the first and the second excited states of the C–C torsion have been measured relative to the ground-state lines. The energies of the first and the second excited states are 98.0 cm−1 and 211.3 cm−1 for the trans form and 160.8 cm−1 and 322.6 cm−1 for the gauche form. The same technique of the relative-intensity measurement has been applied to the temperature dependence of the intensity ratio of trans and gauche lines, giving the result that the gauche form is more stable than the trans form by 0.47±0.31 kcal/mole. Using these data the first seven constants were determined in the Fourier expansion of the potential function around the central C–C bond. The barrier at the cis position seems to be higher than that separating the trans form from two equivalent gauche forms.
Flash Photolysis of Azoethane
Authors: Roquitte B. C. , Futrell J. H.
Published: January 2005

The photodecomposition of azoethane has been investigated at absorbed light intensities of the order of 1023 quanta liter−1 sec−1 obtained from a flash discharge. The effect of incident intensity and of azoethane pressure on the rate of decomposition were studied. The results agree with primary acts postulated on the basis of low intensity photolysis with the exclusion of the reaction of an ethyl radical with fresh molecules of azoethane.
Electron Spin Resonance of an Irradiated Single Crystal of N-Carbamyl Glycine
Authors: Rao D. V. G. L. Narasimha , Katayama Mikio
Published: January 2005

The electron spin resonance spectra of γ-irradiated single crystals of N-carbamyl glycine have been measured at 9 and 23 kMc/sec for various orientations of crystals in the external magnetic field. From the analysis of the hyperfine-interaction constants the free radical produced by γ irradiation is found to be[Complex chemical formula]The spin density at the carbon atom is 75% and the free radical is similar to that produced from acetylglycine and glycylglycine.
Experimental Investigation of the Effect of Irradiation Intensity on the Production of F Centers in NaCl
Authors: Harrison Patrick G.
Published: January 2005

The effect of x-ray intensity on the room temperature production of F centers has been studied experimentally. It was found that the initial rate of production (number of F centers produced per incident photon) is independent of intensity. However, the total first-stage coloration that can be produced increases with increasing intensity. Part of the first-stage coloration produced by a high-intensity radiation is bleached upon reducing the intensity. The coloration in the second stage was found to be independent of the intensity. The rate of coloration in the third stage (the relatively rapid coloration following the second stage) was found to increase with increasing intensity. The excess third-stage centers produced by a high-intensity radiation over those that would be produced by an equivalent lower intensity radiation were bleached upon reducing the intensity to the lower value.
Effect of Pressure on the Resistance of Three Thallous Halides
Authors: Samara G. A. , Drickamer H. G.
Published: January 2005

The effect of pressure to several hundred kilobars has been measured on TlI, TlBr, and TlCl at 25° and 120°C. Since the materials were not highly purified, the sources of conduction electrons at lower pressures, at least, are probably impurities. The resistance pressure curves show three regions. In the lowest pressure region, the resistance decreases rapidly with increasing pressure, corresponding to ionization of the impurities; in the second region the resistance depends only slightly on temperature. In this region the resistance is apparently controlled by mobility of impurities. In the third region the material appears to be a true metal. The electrical measurements are consistent with previous optical studies.
Photolysis of Diborane at 1849 Å
Authors: Kreye W. C. , Marcus R. A.
Published: January 2005

The photolysis of diborane at 1849 Å has been studied in a specially constructed, internal-type mercury-vapor lamp. The products have been found to be H2, B4H10, B5H11, and, at low pressures, a —BH— polymer. Reaction orders at 4°C have been obtained from linear plots of reaction products vs time for a range of diborane pressures from 0.08 to 80 cm, and at two light intensities. Linear relations between products and time existed only at very low conversions (∼1%), which required the development of a low-temperature separation method for manipulating and analyzing the traces of B4H10 and B5H11. Because of the reactivity of these compounds, a detailed conditioning procedure was employed for the glass system.

A mechanism consistant with the kinetic data and suggested by the kinetic results of thermal and photosensitized decomposition of diborane is postulated: the B5H11 is assumed to be formed from a dissociation of B2H6 into BH3's, the latter arising from an excited molecule. The B4H10 and polymer are assumed to be formed from a dissociation of B2H6 into B2H5 and H, followed by radical recombination. There is a significant difference between the kinetics of thermal and photochemical B5H11 formation, a result which may be due to the considerable energy excess of the 1849 quantum over that needed for dissociation (∼125-kcal excess). These kinetic results raise a number of interesting questions, questions which can only be resolved through further investigations of effects due to light intensity, added inert gases, and temperature.

The primary quantum yield of the step forming B2H5 and H is about 10 times higher than that of the one forming BH3's. A rather rough estimate suggests that the former is of the order of magnitude of unity.
Effect of Pressure on the Resistance of Fused-Ring Aromatic Compounds
Authors: Samara G. A. , Drickamer H. G.
Published: January 2005

The effect of pressure to several hundred kilobars has been measured on the resistance of seven-fused ring aromatic compounds, including two polyacenes and five quinones. In general, there is a rapid drop in resistance at lower pressures, followed by a marked leveling at above 200–250 kbars. The leveling is apparently associated with the rapid decrease in compressibility at high pressure observed by Bridgman. The resistance at high pressure varied by several orders of magnitude among the compounds. It seems to be closely associated with the amount of overlap between adjacent molecules in the unit cell. The temperature coefficient of resistance at high pressure was obtained for three compounds. They all remained semiconductors at the highest pressure studied, but the activation energy was about one-sixth of the atmospheric pressure value.
Temperature Dependence of ESR Spectra of Irradiated Polytetrafluoroethylene
Authors: Tamura Naoyuki
Published: January 2005

The double quintet spectrum in the ESR spectra of irradiated polytetrafluoroethylene, which is identified as the radical —CF2ĊFCF2—, varies its spectral shape with temperature. The changes in the linewidths of component lines in room-temperature region are compared with the results of NMR and dynamic mechanical properties and are ascribed to the rotational motion of chains in crystalline regions. The change of isotropic splittings of the quintet from 61 G in rigid state to 32 G in motional state is due to the motional averaging of angular dependences of the β fluorines relative to p orbital of the radical carbon atom. With the triplet spectrum the variation of hyperfine structure with temperature is observed, which is also due to molecular motions.
Equilibrium Constant for Boron Isotope Exchange between BF3 and BF3·O (CH3)2
Authors: Palko A. A. , Begun G. M. , Landau L.
Published: January 2005

The isotopic equilibrium constant for boron exchange between BF3 and BF3·O (CH3)2 has been measured at −8°, 4°, and 22°C. The measured values are compared with values calculated from infrared and Raman spectral data. The physical basis for boron isotope fractionation in systems of this type is discussed.
Magnetic Susceptibility of Neptunium Hexafluoride in Uranium Hexafluoride
Authors: Hutchison Clyde A. , Tsang Tung , Weinstock Bernard
Published: January 2005

The magnetic susceptibilities of solid solutions of NpF6 in UF6 have been measured by the Faraday method. Measurements have been made on solutions with mole fractions 0.0000, 0.0407, 0.0972, 0.1806, 0.340, 0.646, and 1.000 NpF6 and over the temperature range from the boiling point of liquid He to 336.9°K. The susceptibilities χ of Np+6 so determined have been fitted by equations of the form χ=χ0+gs2Nβ2/4kT=χ0+0.09380 gs2/Tat the lower concentrations of NpF6, and by χ=χ0+gs2Nβ2/4kT+A/T2at the higher concentrations of NpF6. The values of | gs | and χ0 extrapolated to infinite dilution are 0.605 and 165×10−6 cm3 mole−1, respectively, using unrationalized Maxwell equations. The standard deviations of these values are 0.004 and 20×10−6, respectively. There is no observable variation of χ0 with concentration of NpF6 in UF6. | gs | is observed to increase from the value 0.641 for pure NpF6 and to pass through a maximum value 0.694 for the 0.340 mole fraction sample as the concentration of NpF6 is decreased. The susceptibilities of solutions of 0.646 mole fraction NpF6 in UF6 above the melting point are lower by about 10 times the error of the determination than those given by (b) when (b) is fitted to only those measurements made below the melting point. They are lower by approximately 4%. The value of the susceptibility of pure UF6 is found to be (43.7±2.6)×10−6 cm3 mole−1 independent of temperature. The value of the susceptibility of fused silica is found to be (−0.412±0.005)×10−6 cm3 g−1 and is independent of temperature. The measurements for NpF6 are compared with the results of the studies of paramagnetic resonance of NpF6 and with theoretical discussions of the electronic states of this molecule.
Quantum Treatment of the Physical Adsorption of Isotopic Species
Authors: Yaris Robert , Sams John R.
Published: January 2005

The results of isotopic substitution in the adsorption of H2, D2, CH4, and CD4 on a graphitized carbon black observed by Constabaris, Sams, and Halsey are explained in terms of two competing effects: the quantum statistical mass effect on the vibrational energy levels normal to the surface and the quantum mechanical effect of isotopic substitution on the dispersion energy.
Photosensitization by Benzene Vapor: Biacetyl. The Triplet State of Benzene
Authors: Ishikawa H. , Noyes W. Albert
Published: January 2005

Biacetyl strongly quenches the fluorescence of benzene vapor. There is a resulting dissociation of biacetyl which occurs presumably because the second excited singlet state of biacetyl is produced by energy transfer from the benzene. Emission by biacetyl also occurs, but the ratio of phosphorescence to fluorescence is very large and may be infinity. The triplet state of biacetyl seems to be produced preferentially by energy transfer from a triplet state of benzene. Emission efficiencies are such that nearly every singlet-state molecule of benzene which does not fluoresce must undergo an intersystem crossover to the triplet state. Since this crossover predominates over fluorescent emission, the life of the singlet state of benzene is presumably determined mainly by the crossover. The effective cross section for self-quenching of the singlet state of benzene is about 0.036×10−16 cm2, while the effective cross section for quenching by biacetyl is about 2.5×10−16 cm2. Since the life of the triplet state of benzene in the gas phase is not known, cross sections for reactions of this state may not be calculated.
Temperature Dependence of Ionic Mobilities in Gas Mixtures
Authors: Courville G. E. , Biondi Manfred A.
Published: January 2005

An ion mobility tube has been used to investigate the mobilities of various ions in helium—neon mixtures at gas temperatures of 77°, 195°, and 300°K. From plots of reciprocal mobility vs fractional concentration of the gases in the mixture which exhibit the linear dependence predicted by Blanc's law, it is possible to trace the mobility of a given ion, e.g., He+, from its parent gas (helium) value, through the mixtures, to its value in the ``foreign'' gas (neon). In this way we have determined the thermal-energy mobilities of the various ions under conditions where the ion—atom interaction changes markedly (e.g., from predominantly charge transfer to polarization interaction). In addition, a search was made for the effects of (HeNe)+, previously postulated to account for deviations from Blanc's law in 300°K studies. No effects clearly attributable to (HeNe)+ ions have been observed.
Mass Spectral Studies of Kinetics behind Shock Waves. II. Thermal Decomposition of Hydrazine
Authors: Diesen R. W.
Published: January 2005

The decomposition of hydrazine diluted in argon has been studied over the temperature range 1200° to 2500°K and pressure range 0.04 to 0.25 atm using a shock tube coupled to a time-of-flight mass spectrometer. The time-resolved mass spectra (25 μsec) enable the simultaneous identification and determination of N2H4, NH3, N2, H2, and the NH2 radical, the five major species observed. The material balance is within the experimental error (10%) during reaction up to complete decomposition.

The primary process in the dissociation of hydrazine is shown to be the rupture of the N–N bond to give NH2 radicals. The observed rate constants for the disappearance of hydrazine are those expected of a unimolecular reaction: N2H4+M→ lim k1N2H4*,N2H4*→ lim k22NH2,at or near the second-order region where the collisional activation (1) is rate controlling. At the higher temperatures, the results are consistent (within experimental error) with the very simple reaction scheme of Reaction (1) and (2) followed by NH2+NH2→ lim k3NH3+NH,NH+NH→ lim k4aN2H2*→ lim k4bN2+H2.At the lowest temperatures the reaction NH2+N2H4→N2H3+NH3 appears to become important.

From the experimental concentrations, a value of k3=2.5×1013 cc/mole−sec (2000∘K)is obtained. An order-of-magnitude estimate gives k4∼1014 cc/mole−sec (2000∘K).