bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction Rates by Nuclear Magnetic Resonance
Authors: McConnell Harden M.
Published: January 2005

The Bloch equations for nuclear magnetic resonance are modified to describe the magnetic resonance of a single nuclear species X which is transferred back and forth between two (or more) magnetic environments (A,B) by kinetic molecular processes. The modified Bloch equations involve the usual assumptions of the Bloch theory and, in addition, require (a) that the X nuclear relaxation times be independent of the molecular exchange rates, and (b) that the X nuclear magnetization in A relax independently of the X magnetization in B, and vice versa. The modified Bloch equations are easily solved in the slow passage case, with arbitrary rf saturation. Earlier relations between reaction rates, and resonance line shapes, which were developed by Gutowsky, McCall, and Slichter, and extended by a number of other investigators, are easily derived using the modified Bloch equations. In the present work the modified equations are used to show how rapid exchange rates can sometimes be measured in solutions where the X relaxation times are relatively long in one system, A, and short in the second, B.
Irreversible Electrochemical Processes in Membranes. II. Effects of Solvent Flow
Authors: Kobatake Yonosuke
Published: January 2005

The correlation of the osmotic flow of the electrolyte solution with the membrane potential and the ionic permeability is discussed from the standpoint of the irreversible thermodynamics of continuous systems. The entropy production in the membrane having a porous structure is evaluated by means of hydrodynamical calculation taking into account the pressure, concentration, and electric potential gradient under the assumption that the ionic concentration can be determined by the Debye-Hückel approximation even in the membrane capillaries. From this entropy production a new equation for the volume flow is derived which enables us to give a reasonable explanation of the ``abnormal osmosis.'' The equations for the membrane potential and for the ionic permeability derived similarly from the entropy production contain the additional terms due to the solvent flow in comparison with the theoretical ones given in the previous paper. The new equation for the membrane potential is found to be more satisfactory than the previous one.
Thermodynamics of Nonstoichiometric Nickel Tellurides. I. Heat Capacity and Thermodynamic Functions of the δ Phase from 5 to 350°K
Authors: Westrum E. F. , Chou C. , Machol R. E. , Grønvold F.
Published: January 2005

Heat capacities of the nickel tellurides were measured at compositions NiTe1.1 and NiTe2.0 (near limits of homogeneity of the δ phase) and at one intermediate composition, NiTe1.5, from 5 to 350°K. Heat capacity values and entropy and enthalpy increments are tabulated. No evidence of order-disorder transitions, or thermal anomalies, or of contributions to the thermal properties from the anisotropy or phonon scattering by the holes in the structure on approaching the composition NiTe2 was observed. Although simple additivity of the heat capacities of the constituent elements failed to represent that of the solution compositions adequately, a Kopp-Neumann treatment in terms of the limiting compositions of the δ phase gives good agreement with the experimental heat capacity and entropy of NiTe1.5 and hence is useful in interpolating to other intermediate compositions.
Electronic Structures of the Methyl Radical: Effect of 3s Atomic Orbital of Carbon
Authors: Higuchi Jiro
Published: January 2005

By taking the 3s orbital of carbon into account, the self-consistent-field (SCF) LCAO—MO method has been applied to the ground state of the methyl radical. The 3s AO used has been determined for the valence state V4(1s22s2pπ+2pπ—3s) by a variational procedure, so that the orbital exponent of the 3s simple Slater AO obtained is 0.6374 instead of Slater's value 0.4833. For the other states with 3s AO, it is similarly concluded that good approximate 3s orbitals cannot be obtained by using Slater's rule, and more satisfactory shielding constants for the extra-valence-shell electron are given. Interactions between all electrons have been taken into consideration but the orthogonality relationship between 1s orbitals of carbon and hydrogen has been assumed. For the MOs occupied in the ground state, the forms are hardly changed by the inclusion of the 3s AO, and the contribution of the 3s AO is very small. For the lowest vacant orbital, however, this contribution is exceedingly great and qualitatively the conventional approximation by the 3s AO is rather more satisfactory than the use of the antibonding LCAO—MO constructed by the valence-shell orbitals. In the lower electronic states calculated, such properties are prominent and the agreements with the observations are relatively good, especially by the inclusion of the 3s AO. The influence of the other extra-valence-shell orbitals is discussed.
Role of Atomic Valence States in Molecular Energy Calculations
Authors: Hurley A. C.
Published: January 2005

Ab initio calculations of molecular binding energies are examined critically in a basis of antisymmetrized products of approximate atomic state functions (the approximate composite functions of Moffitt). It is shown that much more accurate results may be expected if the binding energy is calculated relative to a suitably defined generalized valence state V of the dissociation products. The energy of this state V relative to the ground state of the dissociation products is estimated from atomic spectral data. This procedure leads directly to the intra-atomic correlation correction previously proposed by the author as a necessary modification of Moffitt's method of atoms in molecules.

Detailed calculations are carried out for the ground states of the molecules LiH and BH, and for the ground and excited states of the benzene molecule (in the usual π-electron approximation). In each case the intra-atomic correlation correction leads to a substantial improvement in the accuracy of the results.
Transitions in Adsorbed Monolayers. I. Experimental
Authors: Fisher B. B. , McMillan W. G.
Published: January 2005

This first of three papers describes the preparation of sodium bromide samples on which adsorbed krypton and methane exhibit transitions in the region below one monolayer. The isotherms for these gases are reported for temperatures ranging from 64 to 85°K. The nitrogen isotherms at various temperatures show no such transition, and are discussed from the point of view of the BET theory. A device for maintaining a constant level of liquid nitrogen under reduced pressure is also described.
Delayed Fluorescence of Complex Molecules in the Vapor Phase
Authors: Williams Richard
Published: January 2005

It has been found that the vapors of several fluorescent aromatic hydrocarbons have two components in their fluorescence. These have the same emission spectrum but greatly differing decay times. The lifetime of the fast component is probably that which would be predicted from the strength of the absorption spectrum. This investigation was concerned with the slow component whose decay was exponential with a lifetime of the order of milliseconds. Detailed observation of the behavior of this lifetime as several experimental conditions were changed has shown that a bimolecular process is responsible for the delayed emission. A mechanism is proposed and discussed in detail.
Resonance in Sterically Hindered Aromatic Molecules
Authors: Adrian F. J.
Published: January 2005

Many aromatic molecules, typical of which are the triphenylmethyl radical and cis-stilbene, cannot have the planar structure which would maximize the resonance energy, because of steric hindrance. A semiempirical method of treating such molecules has been developed. It is assumed that the primary effect of the steric strain is to rotate the phenyl groups out of the plane of the molecule. The resulting reduction in resonance energy is estimated using the valence-bond method. The steric interaction energies are calculated using a method of Eyring, based on the ``perfect pairing approximation'' of valence bond theory. A plot of the sum of these two energies vs twist angle gives the equilibrium configuration, and the effective resonance energy of the molecule.

The triphenylmethyl radical has a predicted twist angle of 32°, and is stabilized partly by its resonance energy and partly by steric strain in hexaphenylethane. The theoretical twist angle for the free radical di-p-anisyl nitric oxide is 25°, as compared with an experimental result of 33°. A close balance between steric strain and resonance in biphenyl leads to virtually free rotation about the central bond. Finally, it is shown that steric hindrance accounts for the energy difference between the cis- and trans-isomers of stilbene and azobenzene.
Energy Exchange between Cold Gas Molecules and a Hot Graphite Surface
Authors: Meyer Lothar , Gomer Robert
Published: January 2005

Methane or ethane do not decompose on clean graphite surfaces up to 2300°C as long as the mean free path of the gas molecules exceeds the dimensions of the reaction cell. An investigation of the energy exchange between a hot graphite surface and cold molecules impinging on it revealed an accommodation mechanism of temporary adsorption followed by evaporation at critical temperatures essentially independent of the filament temperature as long as the latter is higher than the former. The evaporation temperature for methane is far below its decomposition temperature.
Propagation of Electronic Excitation in Insulating Crystals
Authors: Merrifield R. E.
Published: January 2005

A general method for the description of nonstationary excited states of an insulating crystal is outlined. For the general case, the time-dependent wave function is given implicitly by means of a simple generating function. In the nearest-neighbor approximation, the solution can be given explicitly in terms of Bessel functions. The effect of an idealized crystal surface on exciton propagation is examined. The exciton behaves as though repelled by the surface.
Reactions of Nitrogen Atoms. II. H2, CO, NH3, NO, and NO2
Authors: Kistiakowsky G. B. , Volpi G. G.
Published: January 2005

The reactions of H2, CO, and NH3 with nitrogen atoms are too slow for detection either at room temperature or in the neighborhood of 250° in a low pressure ``stirred'' reactor flow system with a mass spectrometer as the analytical device, the rate constants being less than 108 cc/mole, sec. The addition of these gases to active nitrogen causes no qualitative changes in the spectrum of the afterglow. In presence of ammonia the intensity of the afterglow is reduced, the inverse of the intensity being linear in the pressure of ammonia. These observations, coupled with the data in the literature, are interpreted as evidence that a transfer of electronic energy takes place between the excited nitrogen molecules, the emitters of the afterglow and ammonia molecules. Excitation of ammonia is followed by its dissociation. A modified flow apparatus, more suitable for the study of fast reactions, was used to reinvestigate the reactions of nitrogen atoms with NO and NO2. Only the lower limit of the rate constant of the reaction N+NO=N2+O, 5×1013 cc/mole, sec, could be estimated. The rate of the reaction with NO2 was also too fast to measure, but the lower limit of the rate constant is less certain.
Hfs of the H2S Molecule and Its Electronic Structure
Authors: Ohno Kimio , Mizuno Yukio , Mizushima Masataka
Published: January 2005

The observed hfs coupling constant of the H2S33 molecule shows a large asymmetry although the H–S–H bond angle is known to be almost 90°. It is shown in this paper that a nonzero d character of the S–H bond orbital can explain this result. Assuming that the electron distribution is cylindrically symmetric about each S–H bond, and the radial part of the p- and d-wave functions are the same, 10.5% s character, 73.5% p character, and 16% d character is concluded for the bond orbital; 23% p character and 77 percent s character is assigned for the lone pair. If the ionic structure is neglected, the electric quadrupole moment of the S33 nucleus is estimated to be —0.11×10—24 cm2.
Note on the Determination of Molecular Structure from Spectroscopic Data
Authors: Laurie Victor W.
Published: January 2005

The problem of the change upon isotopic substitution of ``effective'' bond lengths and angles involving hydrogen is considered. Evidence is presented that in certain cases such variation is largely due to vibration of the heavy atoms rather than of the hydrogens. A method of calculating this effect is presented which utilizes a parameter similar to the ``quantum defect'' Δv=Ic—Ia—Ib observed in planar molecules. Estimates are given of the changes to be expected in effective hydrogen parameters upon isotopic substitution. Bond angles are found to slightly increase and bond lengths are found to decrease.
Absorption Spectrum of Crystalline Anthracene. Measurements on the Absorption Edge
Authors: Ferguson J. , Schneider W. G.
Published: January 2005

The absorption spectrum of single sublimation flakes of anthracene has been redetermined with a view to investigating the b polarized absorption edge. From measurements at room temperature on crystals of known thickness and also from spectra at 77° and 4°K it has been established that the major part of this absorption takes place in a region of about 50 layers below the crystal surface. The crystal energy levels are then split to a much greater extent than in the main body of the crystal, and it is suggested that this occurs because of some slight crystal structure modification. The weaker absorption lines which also occur on the absorption edge are taken to represent transitions in molecules located near or at imperfections.
Absorption and Fluorescence Spectra of Crystalline Pyrene
Authors: Ferguson J.
Published: January 2005

The absorption and fluorescence spectra of crystalline pyrene have been measured at room temperature and 77°K. Only the first absorption region could be studied because of crystal thickness but a Davydov splitting of about 18 cm—1 was detected with the a polarization at higher energy than the b polarization. Calculations of the splitting (dipole-dipole approximation for the intermolecular potential) give 23 and 13 cm—1, respectively, for the B2u and B3u levels with the observed sense, and so it is not possible to decide between two possible assignments from theory. The polarization ratio shows that mixing with a higher level of opposite polarization is present and this is consistent with the only theoretical prediction of energy levels in the molecule.

The fluorescence is displaced to long wavelengths from the absorption spectrum and is a broad band with a maximum which is further displaced on cooling the crystal. The band has been interpreted as a charge-transfer transition involving the molecules grouped in pairs in the crystal.
Paramagnetic Resonance Spectra of Some Semiquinone Free Radicals
Authors: Adams M. , Blois M. S. , Sands R. H.
Published: January 2005

The paramagnetic resonance spectra of a number of semiquinone free radicals have been observed using a microwave ESR spectrometer.

The character of the hyperfine structure, splitting constants, and g values for these radicals are tabulated.
Electrical and Optical Properties of Synthetic Calcium Titanate Crystal
Authors: Linz A. , Herrington K.
Published: January 2005

The optical density of a flame fusion single crystal plate of CaTiO3 is reported. The refractive indices for the visible region are given, with nD = 2.403±0.02. The results of dielectric constant and loss measurements over the temperature range from 90 to 430°K reveal no unusual behavior. A room-temperature dielectric constant of 190 is reported.
Rotational Structure of the Infrared Absorption Spectrum of Hydrogen Peroxide Vapor
Authors: Hirota Eizi
Published: January 2005

The internal rotation of hydrogen peroxide molecule is treated on the assumption that the hindering potential is approximately expressed by the two-term Fourier expansion: V=(V1/2)(1+cosχ)+(V2/2)(1+cos2χ). The doublet structure of the infrared absorption spectrum is considered to be caused by the existence of a double minimum in the hindering potential. The available experimental data on the microwave spectra and on the infrared combination bands yield the result of V1=244 cm—1 (700 cal/mole) and V2=319 cm—1 (910 cal/mole). Thus it is concluded that the cis barrier (452 cm—1 or 1290 cal/mole) is definitely higher than the trans one (208 cm—1 or 590 cal/mole).
Chemical Effects of Photonuclear Reactions in the Propyl Bromides
Authors: Richardson A. E. , Voigt A. F.
Published: January 2005

Two new photonuclear reactions are reported, Br79(γ,2n)Br77 and Br79(γ,3n)Br76.

The organic retention following the Br81(γ,n)Br80m reaction in liquid n- and isopropyl bromides was found to be 47 and 36%, respectively, appreciably higher than reported values following the Br79(n,γ)Br80m reaction. Higher retentions were also noted for irradiations of the solid bromides. The relative yields of individual organic products were determined for irradiations of both liquid and solid and were in many respects in striking agreement with data from activation by (n,γ) reaction and isomeric transition. In solid n-propyl bromide the (γ,n) and (γ,3n) reactions gave the same ratio of parent compound to total organic yield.

Data on the scavenger effect show that thermal recombination reactions occur in both liquid and solid. Marked increases are shown in the thermal organic yield with only slight increases in the nonthermal retention for both bromides for (γ,n) compared to (n,γ) activation. The reasons for these increases are discussed.

In general, the data indicate that elastic collision mechanisms are unimportant compared to random fragmentation as an explanation of the results.
Determination of the g Tensor in Paramagnetic Resonance
Authors: Weil John A. , Anderson John H.
Published: January 2005

Methods for evaluating the completely asymmetric g tensor from magnetic resonance data are outlined and discussed.
Photodesorption in Zinc Oxide Semiconductor
Authors: Medved D. B.
Published: January 2005

Dark and photoconductivity in sintered zinc oxide have been studied by Morrison and Melnick as an oxygen chemisorption process. An order of magnitude calculation shows that a consequence of Melnick's theory of photoconductivity should be an observable new effect which we call photodesorption (the release of surface adsorbed gases by light). Measurement of the photodesorption from sintered porous zinc oxide simultaneously with the photoconductivity is described.
Hydrogen Conversion and Exchange Reactions in Aqueous Solutions Induced by Gamma Rays
Authors: Friedman Harold L. , Zeltmann Alfred H.
Published: January 2005

Experimental studies have been made of several γ-ray-induced reactions of hydrogen in aqueous solutions in which no net chemical change occurs. The most complete results were obtained at pH 2, where radiation-induced chain reactions are found in the conversion of parahydrogen and in the isotope exchange reactions of HD and of H2—D2 mixtures, but where there is only a nonchain exchange of D2 with the solvent. The exchange data are in agreement with the earlier work of Gordon and Hart, but are more extensive in some respects.

It is assumed that the chain conversion and exchange are carried by steps such as H+H2→H2+H,H+D2→HD+D,and isotopically related reactions, and furthermore that these reactions have the same specific rate constants in solution as in the gas phase at the same temperature. All the data at pH 2 can then be correlated by a single mechanism and the following conclusions are reached. At the lower dose rates in solutions of H2 the effective stationary-state concentration of H atoms is proportional to the dose rate, reaching 2×10—8 M at 1018 ev/l sec. The effective mean life of H atoms under these conditions is 0.2 sec. The rate constant of the reaction H+H→H2,in water at pH 2 is at most 1×108 l/mole sec. The pseudo firstorder rate constant of the reaction D+H2O→DOH+H,in water at pH=2 is 2 sec—1.

The last conclusion leads to an important restriction on the importance of H2+ in irradiated solutions, namely, H2+ cannot be in rapid equilibrium with H and H+ or this would be a path for a fast exchange of D with H2O.

The investigation of other pH ranges is less complete than that at pH 2, but the conclusion of Gordon and Hart, that the stationary-state H atom concentration produced by γ rays is much lower in basic than in acid solution, has been confirmed.
Antisymmetrized Hückel Orbital Calculations of Ionization Potentials and Electron Affinities of Some Aromatic Hydrocarbons
Authors: Hedges R. M. , Matsen F. A.
Published: January 2005

Antisymmetrized Hückel orbital calculations of the ionization energy and the electron affinity have been made for twenty-three condensed-ring aromatic molecules. In these calculations differential overlap has been neglected. The calculated ionization energies together with the polariographic reduction potentials permit the estimation of solvation energies of molecular ions.
Molecular Association of Methanol Vapor
Authors: Inskeep Richard G. , Kelliher James M. , McMahon Paul E. , Somers Bruce G.
Published: January 2005

The absorption of infrared radiation by methanol vapor in the region 3200 to 3800 cm-1 has been studied at 305° and 335°K as a function of vapor density. The results best correlate with the model that methanol vapor is composed of monomer, dimer, and tetramer, with little or no trimer present. The heat of dissociation of the dimer is found to be approximately 3 kcal/mole, and that of the tetramer approximately 17 kcal/mole. The greater stability of the tetramer compared to the dimer is consistent with a cyclic structure for the tetramer.
Hydrogen Fluoride Polymer Spectrum, Hexamer and Tetramer
Authors: Smith D. F.
Published: January 2005

The experimental techniques employed to investigate the polymer absorption are presented.

Experimental results at various pressures at temperatures from —70°C to +73°C are presented. The more important qualitative features noted are: (1) the absorption is strongly dependent upon both the temperature and pressure; (2) in some cases the shape of the bands is dependent upon the pressure; (3) at low temperature only very low pressures of vapor (hence of polymer) are necessary to observe some absorption. The application of Dalton's law, the law of mass action, Lambert's law, and Beer's law, as well as Van't Hoff's equation to the hydrogen fluoride monomer-polymer system is discussed.

It is then shown that under some special circumstances the absorption varies simply as the fourth power of the pressure, under others as the sixth power of the pressure, but more generally where the absorption is strong as the sum of two terms, one containing the fourth power of the pressure the other the sixth power. The absorption thus corresponds to the overlapping spectra of a tetramer and of a hexamer, which can be separated on the basis of this pressure dependence. From the temperature variation of the absorption, the heats of polymerization are estimated as ΔH4 = —19 kcal/mole and ΔH6 = —40 kcal/mole. In general, the absorption outside the range of monomer absorption is as consistent with a tetramer-hexamer interpretation for deuterium fluoride as for hydrogen fluoride.
Mean First Passage Time for a Random Walker and Its Application to Chemical Kinetics
Authors: Kim Shoon Kyung
Published: January 2005

The mean first passage time for a random walk with reflecting and absorbing barriers is computed by assuming Onsager's reciprocal relation for the transition probabilities. The result, which is valid for an arbitrary dimensional random walk, appears as a quotient of determinants whose elements are the transition probabilities and the initial distribution. For the one-dimensional case, this result is written as a series which converges rapidly when nearest neighbor transitions predominate; in fact, the series reduces to a closed form for the case when only nearest neighbor transitions are allowed, and always converges for the case when only nearest and next-nearest transitions are allowed. Montroll and Shuler's computation of the mean first passage time for the case of the truncated harmonic oscillator model of a diatomic molecule is simplified and extended to an arbitrary initial distribution. In addition, the mean first passage time for the case of an-harmonic oscillator model is computed by using the transition probability obtained recently by Shuler, Bazley, and Montroll. In terms of the mean first passage time, the range of validity of the equilibrium theory in chemical kinetics is discussed.
Kinetic Studies of Hydroxyl Radicals in Shock Waves. I. The Decomposition of Water between 2400° and 3200°K
Authors: Bauer S. H. , Schott G. L. , Duff R. E.
Published: January 2005

The decomposition of water vapor has been studied at temperatures between 2400° and 3200°K generated in plane shock waves by following changes in the concentration of OH with time. Specific radiation absorbimetry permits these measurements to be made with microsecond resolution. The source of OH radiation used was a flash lamp containing water vapor. Measurements were made on the gas behind reflected shock waves in argon at initial pressures near 50 mm Hg and containing the reactant, H2O vapor, in amounts of the order of 1 mole %. The shock tube and associated electronic and optical equipment are described. Problems of purity, chemical analysis, and reduction of data are discussed. Absorption by OH was calibrated with the equilibrium mixtures resulting from the decomposition of H2O and from the reaction of H2 and O2. The rate of formation of OH from H2O is proportional to the H2O concentration and nearly independent of the argon pressure. The effective activation energy is about 50 kcal/mole. Addition of 2% O2 to the mixture approximately doubles the rate of OH formation and preserves the 50 kcal activation energy. Addition of 2% H2 decreases the rate and increases the activation energy to about 80 kcal/mole. Possible reaction mechanisms are considered. The initial rate of appearance of OH cannot be interpreted in terms of the simple dissociation of H2O into H and OH, and it seems necessary to consider a relatively low-energy path involving H2O2 or the HO2 radical as an intermediate.
Hydrogen→Deuterium Exchange Reaction in α-Keratin
Authors: Fraser R. D. B. , MacRae T. P.
Published: January 2005

A quantitative study of the hydrogen→deuterium exchange reaction in α-keratin by means of infrared spectra showed that after 50 hr at 30°C about 30% of the peptide linkages had not reacted. Observations between 50 and 1000 hr failed to detect any further reaction but elevation of pD or temperature caused additional exchange. Evidence is presented which suggests that the unreactive peptide linkages occur in the organized regions of the structure (microfibrils) and that complete exchange of the replaceable hydrogen atoms in the sidechains takes place.
Specific Heat of Liquid Ozone
Authors: Brabets Robert I. , Waterman Thomas E.
Published: January 2005

The specific heat of liquid ozone has been measured over a temperature range of 97 to 121°K. The heat capacity was found to be a linear function of temperature and is represented by the equation Cp=0.425+0.0014(T−90) cal/g ∘C.This equation is considered sufficiently accurate for engineering purposes over the temperature range of 90 to 150°K. Thus, the values of 0.425 and 0.509 cal/g °C are reported for the sp ecific heat of liquid ozone at 90 and 150°K, respectively.
Infrared Absorption Spectra of Chromyl Fluoride and Chromyl Chloride
Authors: Hobbs Willard Earl
Published: January 2005

The infrared absorption spectra of gaseous chromyl fluoride and gaseous chromyl chloride have been investigated. The region investigated for chromyl fluoride was 2 to 36 μ while that for chromyl chloride was 2 to 25 μ. Six fundamental and nineteen first overtone or binary combination bands have been observed in the spectrum of chromyl fluoride, the fundamental bands being located at 274, 304, 727, 789, 1006, and 1016 cm—1. The observed transitions have been assigned on the basis of a tetrahedral model of C2v symmetry. From the observed spectrum it was possible to estimate the probable positions of the three remaining fundamental bands. The observed spectrum of chromyl chloride included four fundamental bands located at 475, 499, 990, and 1000 cm—1 and one first overtone or binary combination band located at 1980 cm—1.
On the Growth of Metal Whiskers by Hydrogen Reduction of Halides
Authors: Webb W. W. , Riebling E. F.
Published: January 2005

Observations have been made of the pressures of hydrogen and hydrogen halide gases prevailing during growth of a variety of metal whiskers by hydrogen reduction of volatile metal halides. The orders of magnitude of the maximum metal activities observed are only 1 to 100 rather than the maximum thermodynamically feasible values of 104 to 106 that might be attained in these reactions. This result is more in accord with current theories of whisker growth. It appears that the reduction of metal halide occurs primarily on the whisker surface and that metal halide vapor rather than metal vapor provides most of the vapor-phase mass transport during whisker growth by this process.
Mass Spectrometric Study of Ferrous Chloride Vapor
Authors: Schoonmaker Richard C. , Porter Richard F.
Published: January 2005

Mass spectrometric studies of the vaporization process of ferrous chloride show that the major vapor species is monomeric FeCl2(g). A small concentration of Fe2Cl4(g) is present in the vapor at low temperatures. The ratio of dimer to monomer concentration increases rapidly with temperature showing that at the melting point of FeCl2(s), the equilibrium vapor consists of about 25% dimer. Thermodynamic treatment of ion current data yields for the reaction 2FeCl2(s)=Fe2Cl4(g),ΔH640∘K∘=56±3 kcal/mole of dimer and for the reactionFe2Cl4(g)=2FeCl2(g),ΔH640∘K∘=32±3 kcal/mole of dimer.
Infrared Spectra of the Alkaline-Earth Halides. I. Beryllium Fluoride, Beryllium Chloride, and Magnesium Chloride
Authors: Büchler Alfred , Klemperer William
Published: January 2005

The infrared spectra of BeF2, BeCl2, and MgCl2 in the vapor phase have been measured. Both the asymmetric stretching mode ν3 and the bending mode ν2 were observed for each of these compounds. The observed frequencies are BeF2BeCl2MgCl2ν315201113597cm−1ν2825482295Two bands of the gaseous dimer Be2Cl4 were also observed. Examination of the bending force constants shows that the bonds in the dihalides are strongly directional. The bond stretching force constants of these dihalides are almost identical in magnitude with those of the corresponding monohalides BeF, BeCl, and MgCl.
Some Aspects of Photoconductivity in Cadmium Selenide Crystals
Authors: Bube Richard H. , Barton Lucian A.
Published: January 2005

Vacuum annealing of insulating and insensitive cadmium selenide crystals grown from the vapor phase increases their photosensitivity to a value at least as high as that of crystals sensitized by impurity incorporation. Such annealing-sensitized crystals have one hundred to one thousand times greater sensitivity than impurity-sensitized crystals at low light intensities and/or high operating temperatures. A new infrared quenching band with maximum at 1.0 ev is found at elevated temperatures, correlated with the residual sensitivity of the annealing-sensitized crystals. The same sensitizing centers are involved in the photoconductivity of annealing-sensitized and impurity-sensitized cadmium selenide crystals, regardless of whether the excitation is absorbed only at the surface or throughout the volume. In annealing-sensitized crystals, the effective volume for photocurrent flow for volume excitation is one hundred times larger than that for surface excitation; this result indicates a fairly homogeneous distribution of sensitizing centers through the volume of the crystal. A tentative description of conductivity and photosensitivity characteristics is given in terms of the various types of vacancies likely to be participating.
Absorption Spectrum of Rubidium in the Presence of Isomeric Hydrocarbons
Authors: Jefimenko Oleg , Gwinn Joel Anderson
Published: January 2005

Absorption spectra of Rb in the presence of various hydrocarbons (ethylene, propylene, butene-1, isobutylene, isobutane, n-pentane, isopentane, neopentane, n-hexane, 3-methylpentane, 2,3-dimethylbutane, and neohexane) were studied for the purpose of determining the dependence of the collision-induced satellite bands on the structure of colliding particles. It was found that the positions of the low-temperature red bands are regularly affected by the differences in structure of the hydrocarbon molecules. In particular, the least branched (straight chain) isomeric molecules produce bands with the smallest band-line separations, and the most branched molecules with four or three methyl groups attached to the same carbon atom produce bands with the largest band-line separations. On the other hand, the positions of the high-temperature red bands as well as the positions of the violet bands are not noticeably affected by the differences in molecular structure of the hydrocarbon isomers employed in this work.
Nonstoichiometry in Uranium Dioxide
Authors: Aronson S. , Belle J.
Published: January 2005

A thermodynamic study of the uranium-oxygen system, primarily in the single phase region UO2–UO2.20, has been made at temperatures of 1150° to 1350°K. An electrochemical technique was used to obtain emf measurements on uranium oxide half-cells. The cells were of the type Fe, FeO|(ZrO2+CaO)|UO2+x, Pt where x varied from 0.01 to 0.20.

Partial molar free energies, entropies, and enthalpies of solution of oxygen in UO2+x were calculated. The partial molar free energy is a linear function of temperature at constant composition. The partial molar entropy increases negatively with increasing oxygen content.

Equations relating the thermodynamic quantities to the degree of nonstoichiometry have been developed on the assumption that the UO2+x region can be treated as an interstitial solution of oxygen ions in the UO2 fluorite lattice. Semiquantitative agreement with the data was obtained.
Pi-Electron Correlation in the Polyenes
Authors: Dewar M. J. S. , Wulfman C. E.
Published: January 2005

The study of electron correlation by the determination of configurations of maximum probability is extended to molecular problems in an investigation of the ground states of the first four polyenes. The correlation among pi electrons of the same spin is such that they are most likely to be found near the midpoints of the classical double bonds. Reasons are adduced for extending this result to all the pi electrons, irrespective of spin, and a simple wave function implying this is investigated and shown to give good pi electron energies.
Dielectric Properties of Aqueous and Alcoholic Electrolytic Solutions
Authors: Hasted J. B. , Roderick G. W.
Published: January 2005

Results of dielectric constant and loss measurements on a range of aqueous and alcoholic electrolytes at wavelengths of 1.25, 3.2, 9.9, 17, and 51.5 cm from 3°C to 25°C are analyzed in terms of dielectric constant depression, relaxation time depression and spread, and conductivity elevation. The small relaxation time spread (α∼0.02) is interpreted as being due to hydrogen bond bending, the relaxation time depression as bond breaking, and the dielectric constant depression as restriction of dipole rotation by the ions. The conductivity elevation is believed to be an effect of the same type as that observed by Little and Smith.

It is shown that the alcohol dielectric constant depression is too large to be interpreted in terms of dipole restriction by solvation so that the ion must have a marked effect on the alcohol structure.
Triatomic Linear Molecules Containing Carbon and Oxygen, Sulfur, Selenium, or Tellurium. I. Vibrational Spectra of CS2, CSe2, SCSe, and SCTe
Authors: Wentink Tunis
Published: January 2005

The vibrational infrared absorption spectra of the molecules CSe2, SCSe, and SCTe have been recorded and analyzed. Some Raman data are also reported. The fundamental frequencies (in cm—1) of these molecules, σ1 (symmetric stretching), σ2 (bending), and σ3 (asymmetric stretching) are, respectively: CSe2 (gas) 368, 308, and 1303; CSe2 (liquid) 368, 310, and 1267; SCSe (g) 506, 355, and 1435; SCSe (l) 502, 350, and 1408; SCTe (CS2 solution) 423, 337, and 1347. Observed isotopic shifts due to C13 in all three compounds are reported and discussed. The expected linearity of CSe2 is confirmed. The synthesis and purification of the more unstable members of the CX2-XCZ family (X, Z=0, S, Se, or Te) are discussed. Some predictions, of possible use in identification, for the intense fundamental σ3 of the so far unreported and probably very unstable OCTe, SeCTe, and CTe2 are made. These are based on a treatment using a uniform potential energy function for all these molecules, to be presented in a subsequent paper.
Sputtering of Silver by Hydrogen Ions
Authors: O'Briain Cormac D. , Lindner Amelie , Moore Walter J.
Published: January 2005

The sputtering of silver by the ions H+, H2+, and D+ has been measured by allowing a magnetically analyzed beam of ions from an RF source to strike a target containing radioactive silver. The angular distribution of the sputtered silver follows approximately a cosine law. At normal incidence and 9250 volts energy, the number of atoms sputtered per incident ion is 0.03 for H+, 0.075 for H2+, and 0.08 for D+. These values are much lower than those of previous workers, and the difference is ascribed to the absence of atoms and excited molecules from the analyzed ion beams.
Molecular-Orbital Treatment of Isotropic Hyperfine Interactions in Simple Aliphatic Radicals
Authors: Chesnut Donald B.
Published: January 2005

The problem of isotropic hyperfine interactions in the EPR spectra of aliphatic free radicals is approached from the molecular-orbital picture of hyperconjugation. The ethyl, methylethyl, and 1,1-dimethylethyl radicals are treated by this approximation; with a reasonable choice of parameters, the results can be correlated rather well with our present knowledge of aliphatic radicals. The calculated coupling constants of methyl group hydrogens are of the order of 15 to 25 gauss, do not decrease radically with the presence of additional methyl groups, and are very nearly proportional to the molecular-orbital unpaired electron density at the central carbon atom.
Absorption and Photoionization Coefficients of Furan Vapor
Authors: Watanabe K. , Nakayama Toshio
Published: January 2005

Total absorption coefficients of furan vapor were determined in the region from 1050 to 2150 A by a photoelectric method, and photoionization coefficients in the region from 1050 to 1400 A with an ion chamber. A reassignment of the absorption bands in the region from 1400 to 1700 A yielded two Rydberg series converging to 8.89 ev in agreement with the ionization potential obtained by photoionization measurements. Another Rydberg series was found to converge to 9.95 ev corresponding probably to the removal of an inner π electron of furan.
Changes in the Near Ultraviolet Spectrum of Crystalline Hexamethylbenzene Accompanying a Low Temperature Phase Transition
Authors: Schnepp O.
Published: January 2005

The hexamethylbenzene crystal undergoes a phase transition at 110°K. The near ultraviolet absorption spectra of single oriented crystals of this substance have been studied in polarized light in the neighborhood of the transition temperature. A drastic and discontinuous change of the spectra is observed to accompany the phase change. The spectral change at the transition point is interpreted as indicative of a distortion of the molecule such that only twofold axes remain.
Neighbor Interactions and Internal Rotations in Polymer Molecules. I. Stereospecific Structure and Average Dimensions
Authors: Lifson Shneior
Published: January 2005

The skeletal bonds of vinylic polymer molecules are classified as (+) bonds and (—) bonds according to the arrangement of the side groups relative to the bonds. The detailed structure of isotactic and syndiotactic polymers is characterized by the different regularities of arrangement of these two bond types along the molecular chain. Symmetry properties of (+) and (—) bonds, and of (+) (+), (—) (—), and (—) (+) bond pairs, are discussed. These lead to relations between the average values of functions of the internal-rotation angles of the various bond-pairs.

The end-to-end distance of isotactic and syndiotactic molecules is expressed in terms of bond lengths, bond angles, and internal rotation angles of the skeletal bonds, using methods of matrix algebra. The mean-square end-to-end distance 〈h2〉 of these molecules is determined by certain averages of trigonometric functions of the internal rotation angles enclosed between neighboring skeletal bond pairs. The averages depend on the energy of interaction of neighboring side groups as well as on the internal interactions within the skeletal bonds, and are different in the isotactic and syndiotactic molecules.
Reactions of Gaseous Molecule Ions with Gaseous Molecules. V. Theory
Authors: Gioumousis George , Stevenson D. P.
Published: January 2005

Ion-molecule reactions of the sort observed as secondary reactions in mass spectrometers have been treated by the methods of the modern kinetic theory; that is, the rate of reaction is expressed in terms of the velocity distribution functions of the reactants and the cross section for the reaction. The cross section, which is calculated by means of the properties of the classical collision orbits, is found to have an inverse square root dependence on energy. The ion distribution function, which is far from Maxwellian, is found by means of an explicit solution of the Boltzmann equation. A simple relation is given which relates the mass spectrometric data to the specific rate of the same reaction under thermal conditions. For the simpler molecules, this rate may be calculated completely a priori, with excellent agreement with experiment.
Intramolecular Twisting Effects in Substituted Benzenes. II. Ground-State Properties
Authors: McRae Eion G. , Goodman Lionel
Published: January 2005

The effects on ground-state properties of twisting a substituent group about the substituent-ring bond in substituted benzenes are discussed from the viewpoint of semiempirical MO theory. The ground-state properties are discussed with reference to a parameter θ, which generally increases as the substituent is twisted. The substituent-ring bond order varies approximately as cosθ, and the following vary approximately as cos2θ: the resonance energy, charge densities, ring C–C bond orders and the π-electronic dipole moment. The θ dependence of the total dipole moment is discussed. Numerical applications to N,N-dimethylaniline and related molecules are described, including a detailed treatment of the dipole moments of N,N-dimethylaniline and some of its ortho-substituted derivatives. A brief discussion of the valence state of the dimethylamino group is included.
Relative Intensities of Microwave Absorption Lines
Authors: Verdier Peter H. , Wilson E. Bright
Published: January 2005

A method is described for measuring the relative intensities of microwave absorption lines up to 80 mc. apart to within a few percent, using a Stark-modulated resonant cavity absorption cell of novel design. Barriers to internal rotation in CH3CHO and CH3CH2F have been obtained by measuring the relative intensities of torsional satellites. The resulting barrier heights are: 1103±60 cal for CH3CHO, 3310±210 cal. for CH3CH2F, in good agreement with the values 1162±30 cal for CH3CHO, and 3306±100 cal for CH3CH2F obtained from splitting measurements by Kilb, Lin, and Wilson, and by Herschbach, respectively.

Correction factors are given for errors in intensity and splitting measurements due to small doublet splittings.
Generalized United-Atom Theory. II. A One-Center Model for Cyclic Polyenes
Authors: Chen Tien Chi
Published: January 2005

In cyclic polyenes the quantum numbers of Hückel and Platt are related to the atomic magnetic quantum number ml. A one-center treatment shows that, within the tubular assumption, the lowest one-electron wave functions have roughly the same (ρ, z) dependent part and are distinguished chiefly by the dependence on the azimuthal angle [open phi]. The one-electron level scheme to first approximation is identical to that of Platt's electron-gas theory. Reintroduction of the lower molecular symmetry mixes states of different ml and splits the ml=±(2N+1) degeneracy. The result is suggestive of the LCAO-MO theory, although the latter can be shown to be basically different. A semiempirical united-atom theory can be formulated in close parallel to the LCMO theory of Coulson, Longuet-Higgins and Dewar.
Mass Spectra of Some Simple Esters and Their Interpretation by Quasi-Equilibrium Theory
Authors: King A. Bruce , Long F. A.
Published: January 2005

Mass spectra and appearance potential data are reported for normal and isotopically labeled methyl formate, methyl acetate, and ethyl formate, and reaction mechanisms are proposed for the production of the spectra. The data are analyzed from the standpoint of the quasi-equilibrium theory of Eyring and co-workers. For the data from 70-volt ionizing electrons, frequency factors can be adjusted so that the calculated patterns agree well with the experimental data. These frequency factors seem qualitatively satisfactory although there are some difficulties with the values for some of the rearrangements and hydrogen abstraction processes. However the theory is clearly inadequate at lower ionizing voltages. The probable explanation is that the electronic states are in narrow bands which do not overlap, so that at low voltages a portion of the ionic fragments are produced by direction dissociation, without the redistribution of energy which is required by the quasi-equilibrium theory.
Approximate Formulas for the Viscosity and Thermal Conductivity of Gas Mixtures
Authors: Brokaw Richard S.
Published: January 2005

Approximate expressions for the viscosity and thermal conductivity of gas mixtures have been derived from the rigorous kinetic theory formulas. Three levels of approximation are distinguished, with the third approximation rigorous for binary mixtures.

The first approximation for mixture viscosity is found to be very nearly equivalent to empirical expressions known heretofore. The first and second approximations for mixture conductivity have been compared with rigorous calculations for binary mixtures of nonpolar gas pairs; the first approximation has an average error of 2.6% while the second approximation reduces this error to 0.5%.

The second approximation accounts for the thermal conductivity of binary mixtures of polar and nonpolar gases. (It is assumed that the interchange of translational energy is abnormal for the polar-polar interaction.)
Dissociation of Formic Acid and Deuteroformic Acids by Ion-Molecule Collision
Authors: Melton C. E. , Ropp Gus A.
Published: January 2005

The dissociation of 5.1 kev HCOOH+, DCOOH+, and HCOOD+ ions by ion-molecule collision with H2, D2, He, N2, A, and Kr has been investigated in a mass spectrometer. Approximate values for the cross sections for the resultant fragment ions have been calculated. Positive ion fragments CHO+ and CHO2+. are produced by loss of hydrogen from both of the possible positions. However, rupture of the C–H bond is a factor of two more probable than cleavage of the O–H bond in the formation of CHO2+. The CHO+ ion fragment is formed mainly by removal of the hydroxyl group.