bluuebunny/crossref_metadata_2025 huggingface dataset:
Rates of Reaction of Hydrogen with Iodine
Authors: Sullivan John H.
Published: January 2005

The rates of reaction of hydrogen with iodine have been measured at 633.21°, 666.79°, 710.33°, and 737.93°K with at least a tenfold variation in the hydrogen and iodine concentrations at each temperature. The data have been treated considering the elementary reactions to be I2⇌2I(1)H2+I2→2HI(2)HI→H2+I2(3)I+H2→HI+H(4)H+HI→H2+I(5)H+I2→H2+I(6)I+HI→I2+H.

This classical reaction has long been considered to consist solely of the simple bimolecular reactions (1) and (2). However, the atom mechanism, reactions (3) to (6), is shown to account for 10% of the over-all reaction at 633° and 27% at 738°K when the iodine pressure is one-half atmosphere. The three independent constants k1, k3, and k4/k5 in (mole/cc)—1 sec—1, are given by log10(k1/T½) = 12.78–40740/4.575T, log10(k3/T½) = 12.75–33440/4.575T, and k4/k5 = 0.07, 0.082, 0.117, 0.125 at the experimental temperatures 633°, 667°, 710°, and 738°K.
Polymers and Theory of Numbers. IV. The Problem of Weak and Strong Links in Degradation
Authors: Pathria R. K. , Nanda V. S.
Published: January 2005

The technique employed in our earlier work is extended to treat the degradation of a monodisperse polymer system consisting of N chains such that each chain has two types of links of unequal strength, distributed randomly over its length. An expression for the size distribution in the degraded material is obtained in a closed form which is convenient for numerical computations. Further, the weight average chain length is expressed exactly in the form of a definite integral from which the particular cases follow in a straightforward manner. Exact expressions are also derived for the higher moments of distribution.

Finally, it is shown that the treatment given here is quite general and is capable of ready extension to the case of a polymer system in which the member chains possess more than two types of links.
Nitryl Chloride Molecular Constants from Microwave Spectrum Analysis
Authors: Clayton Lorimer , Williams Quitman , Weatherly T. L.
Published: January 2005

The microwave spectrum of NO2Cl has been studied in the region 25 000 to 40 600 Mc and an analysis made of the J = 2→3 and 3→4 transitions. The following molecular constants were obtained. NO2Cl35NO2Cl37Rotational constants      (Mc)      A13 250    13 250          B5173.85019.0      C3721.13640.4Asymmetry parameter      κ−0.6951−0.7131Quadrupole coupling constants      (Mc)      χaa−94.70−74.58      χbb52.441.3      χcc42.333.3

The structural parameters obtained from these are d (Cl–N) = 1.83 A, d (N–O) = 1.21 A, and O–N–O angle 129.5°. The dipole moment calculated from the Stark effect is 0.53 Debye. Implications of the aforementioned results are discussed.
Brownian Motion in the Centrifugal Field
Authors: Gehatia Matatiahu , Katchalski Ephraim
Published: January 2005

The combined sedimentation and diffusion process of macromolecules in the centrifugal field was considered phenomenologically. For each dissolved particle a stochastic equation is estimated composed of two independent velocities: a diffusional and a sedimentational. With the help of the ``central limit theorem with Lindeberg conditions'' the formula for the distribution of the particles in a ultracentrifugal cell was derived. A transformation has been found which converts the equations of diffusion alone in the formulas of diffusion in a centrifugal field. The expressions for concentrations in rectangular and sectorial cells can be easily tabulated; they solve the corresponding equations of continuity and fulfill the principle of conservation of amount of dissolved particles in the cell. With help of these formulas the sedimentation constant as well as the diffusion constant can be evaluated from the form of the experimental sedimentation curve.
Vibration Perturbations in Electronically Excited Molecules
Authors: Weigang O. E. , Robertson W. W.
Published: January 2005

Small vibration shifts of usually 10 to 50 cm—1 can be observed superimposed on the electronic shifts of 200 to 1000 cm—1 which occur on solvation of aromatic polynuclear hydrocarbons. Vibration assignments for benzene indicate that the observed behavior of its vibration bands is due to the perturbation of a single vibration in the electronically excited benzene molecule. The change corresponds to an increase of frequency for the excited state Eg+3080-cm—1 C–H vibration. A similar phenomenon can be detected in the naphthalene spectrum. The results are compared to the recent work of Fishman, Benson, Wiederkehr, and Drickamer on pressure perturbations of vibrations in electronic ground state molecules in solution.
General Collision Theory Treatment for the Rate of Bimolecular, Gas Phase Reactions
Authors: Eliason Morton A. , Hirschfelder Joseph O.
Published: January 2005

A collisional approach, somewhat similar to the Wang-Chang and Uhlenbeck treatment for the transport properties of polyatomic molecules, is used to obtain a general expression for the rate of a bimolecular chemical reaction in terms of reaction cross sections.

Specialization is then made to the case where a Maxwell-Boltzmann velocity distribution may be assumed for the reactants. This leads to a Laplace transform relation between the rate constants for reaction of molecules in definite internal quantum states and the reaction cross sections. The further assumption of a Boltzmann distribution among the internal energy states of the reactant molecules then leads to a rate equation of the usual form and to an explicit expression for the single over-all rate constant. This expression is used to rederive the results of the old ``simple'' collision theories.

Finally, a collisional approach is used to rederive the usual rate expression of the Eyring theory of absolute reaction rates. The rather drastic approximations which seem to be necessary for such a derivation are pointed out and discussed.
Entropy Effect in Ice Crystal Nucleation
Authors: Fletcher N. H.
Published: January 2005

The effect of bond orientation in ice, which leads to its residual entropy, is also found to be important in its heterogeneous nucleation. Any substrate which orients ice dipoles at its surface parallel to one another is a poor nucleating atent, because it reduces the entropy and hence raises the free energy of any small embryos growing upon it. Critical temperatures are calculated for surfaces of this type, and it is shown that for crystals like AgI or PbI2 the basal faces are poor ice crystal nuclei, and activity is mostly confined to the prism faces. This result leads to improved agreement between observed and theoretical nucleation thresholds and gives an explanation of some of the phenomena observed in nucleation by monocrystalline substrates.
Effect of Conjugation, Hyperconjugation, and Steric Hindrance on Methyl Affinities
Authors: Binks J. H. , Szwarc M.
Published: January 2005

The mechanism of the addition of radicals to aromatic and olefinic compounds is discussed in terms of a potential energy diagram which explains the linear relation between localization energy and the logarithm of methyl affinity per reactive center. It is pointed out that such a linear relation is expected for series of compounds, each having the same type of reaction center, e.g., C–C=C–Hin a series of aromatic hydrocarbons or C=C–H–Hin a series of substrates like ethylene, styrene, butadiene, etc.

The relation between the slope of such a line and the nature of the reactive center is discussed.

The foregoing treatment is extended to explain the effects caused by hyperconjugation, and an excellent agreement is found between theory and experiment.

It is shown that compounds having a methyl substituent on the reactive center are less reactive. This inhibitory action of the methyl substituent is explained in terms of steric hindrance, and it is shown that for a particular center the inhibitory effect amounts to a constant factor independent of the original reactivity of the center. Still greater steric effects are caused by phenyl groups and by two methyl substituents located on a reactive center.

The utility of this ``blocking'' technique for determining the most reactive centers is pointed out.
Effect of Pressure on Some Charge Transfer Spectra
Authors: Stephens D. R. , Drickamer H. G.
Published: January 2005

The charge transfer spectra of [Co(NH3)5I]I2,K2ReCl6,K2ReBr6, quinhydrone, and chloranil-hexamethyl-benzene have been measured as a function of pressure. The shifts of the peaks for the inorganic complexes can be explained in terms of the effect of pressure on the acceptor levels of the metal relative to the ligand levels. The large red shifts observed in the peaks for the organic complexes can be explained in terms of solid-state band theory.
Note on the Normal Stress Effect in the Solution of Rodlike Macromolecules
Authors: Kotaka Tadao
Published: January 2005

Three components of normal stresses in a solution of rodlike macromolecules are calculated on the basis of the general theory of irreversible processes of macromolecular solutions developed by Kirkwood. The results are expressed in expansion series of even powers of the rate of shear and are explicitly given to their fourth powers.

When the hydrodynamic interaction is not taken into account, two components of the normal stresses perpendicular to the direction of flow identically vanish, while, by the introduction of this interaction, they appear. The action of normal stresses is still mainly ``pull'' in the direction of flow as in the free-draining case.
Adsorption of Hydrogen on Silicon
Authors: Law J. T.
Published: January 2005

The adsorption of both atomic and molecular hydrogen on silicon films and single crystals has been studied. The kinetics of the processes as a function of coverage and gas pressure are discussed, and it is shown that in the case of adsorption of atoms, two types of adsorbed species exist. Data obtained for the areas of silicon films as a function of the number of silicon atoms evaporated are in good agreement with previous work.
Statistical Mechanics of Multicomponent Systems: Perturbation Theory
Authors: Nosanow L. H.
Published: January 2005

The molecular Gibbs free energy of a conformal solution is treated by the use of perturbation theory. A general expansion is given, the zeroth order term of which is a linear combination of the molecular Gibbs free energies of suitably chosen one component systems. A criterion is given for the choice of these systems that leads to a unified derivation of three well-known approximations which involve the use of composition dependent pair potentials. The second-order term of the general expansion is used to give a discussion of these approximations. Finally a workable procedure for computing this term is given.
Perturbation of Molecular Distribution Functions by Chemical Reaction
Authors: Mahan Bruce H.
Published: January 2005

A collision cross section for radial combination reactions is derived which indicates that translationally hot free radicals combine faster than the average thermal radicals. The cross section is used to calculate the disturbance of the equilibrium distribution of velocities by radical combination reactions. It is concluded that the equilibrium assumption of chemical kinetics is justified for photochemical systems where the radical concentrations are low, but may be violated in systems where free radical concentrations approach 0.1 mole fraction.
Empirical Intermolecular Potential for Inert Gas Atoms
Authors: Woolley Harold W.
Published: January 2005

Transport and thermodynamic calculations for gases at high temperature call for reliable interaction potentials at close approach. Potentials for the noble gases can be extrapolated approximately, yet with some reliability, from the empirical fit of properties in the ordinary range, using a screened Coulomb repulsion and a dispersion attraction reduced by a suitable factor at close approach. Parameters for this potential can be obtained approximately from the known parameters for the exp-six potential. The resulting empirical coefficient for the Coulomb term is found to be of the general order of magnitude given by the product of the nuclear charges. If the theoretical Coulomb repulsion is used, the screening exponent may alternatively be chosen on the basis of other empirical parameters.
Thermal Conductivity of Binary Mixtures of Diatomic and Monatomic Gases
Authors: Srivastava B. N. , Barua A. K.
Published: January 2005

Thermal conductivity of the binary mixtures of O2–He, O2–Ne, O2–Kr, and O2–Xe have been measured at 30°C and 45°C for various compositions by using the thick-wire-variant of the hot-wire method. For pure O2 the experimental value of the thermal conductivity is lower than that given by the recent theory of Hirschfelder based on the assumption of local chemical equilibrium, and consequently the values calculated from Hirschfelder's formula for the mixture conductivities are also expected to be higher than the experimental values which is actually found to be so for the mixtures investigated here. The agreement becomes excellent when the experimental values of the conductivity of pure O2 are used to calculate the mixture conductivities. The formula for the mixture conductivities has been tested in detail and was found to give satisfactorily the composition dependence. The simpler formula for the thermal conductivity of gas mixtures given by Mason and Saxena has also been tested.
On the Dynamical Theory of Diffusion in Crystals. III. Some Model Calculations and Relation to Continuum Theory
Authors: Lawson A. W. , Rice Stuart A. , Corneliussen Roger D. , Nachtrieb Norman H.
Published: January 2005

Some simple models are considered which permit exact evaluation of the various dynamical parameters of the theory of crystal diffusion previously proposed. The models considered suggest that: (a) The jump frequency is insensitive to the normal mode modifications produced by the adjacent vacancy. (b) There is considerable relaxation about a vacancy. (c) The volume of formation of a vacancy is related to the molar volume by ΔV*≈V/(γG—⅓), where γG is the Gruneisen constant.

The restrictions of the models are briefly analyzed, and the mass dependence proposed by Bak and Prigogine is compared with the quasi-equilibrium model and the discrepancy discussed.
Optical Rotation of Oriented Helices. II. Calculation of the Rotatory Dispersion of the Alpha Helix
Authors: Tinoco Ignacio , Woody Robert W.
Published: January 2005

The polarizability theory for the average optical rotation of a molecule has been generalized and has been used to calculate the optical rotation along specific directions in the molecule. The optical rotatory dispersion of polyglycine and polyalanine for light incident parallel and perpendicular to the helical axis has been calculated. The predicted dispersion is consistent with most experiments if a left-handed helix is assumed for polybenzyl-l-glutamate and peptides with similar rotatory behavior. The average rotatory dispersion for a helix is not in general qualitatively different from that of a random coil.
Interactions between Ground State Oxygen Atoms and Molecules: O–O and O2–O2
Authors: Vanderslice Joseph T. , Mason Edward A. , Maisch William G.
Published: January 2005

Potential energy curves for O–O interactions corresponding to the X 3Σg−, 1Δg, 1Σg+, 3Δu, A 3Σu+, 1Σu−, and B 3Σu− states of O2 have been calculated from spectroscopic data by the Rydberg-Klein-Rees method. Curves for the remaining twelve states of O2 dissociating to ground state atoms have been obtained from relations derived from approximate quantum-mechanical calculations, and checked against the meager experimental information available. Two semi-independent calculations have been made, and are in good agreement with each other. The quantum-mechanical relations also lead to an approximate O2–O2 interaction, which is consistent with interactions derived from vibrational relaxation times and from high-temperature gas viscosity data.
Crystal Spectra of Metal Coordination Compounds. I. Tetrahedral Cobalt(II)
Authors: Ferguson J.
Published: January 2005

A reflecting microscope has been used to measure the absorption spectra, in polarized light, of a number of cobalt(II) compounds in which the ligands are arranged tetrahedrally. These compounds are Cs3CoCl5, cobalt di-p-toluidine dichloride, cobalt dipyridine dibromide, and cobalt dipyridine diiodide. The two transitions, 4A2→4T1(F) in the near infrared and 4A2→4T1(P) in the visible, have been compared in the different compounds and the effect of symmetry discussed. It was also found that the crystal spectra of all but Cs3CoCl5 are modified by interaction between the complexes in the crystal so that the energy levels are not accurately described by the field of the ligands only.
Kinetic Theory of Moderately Dense Rigid Sphere Fluids. III. The Formulation and Solution of the Transport Equation for Binary Mixtures
Authors: Harris Robert A. , Rice Stuart A.
Published: January 2005

The theory of the moderately dense rigid sphere fluid is extended to mixtures. The modified Boltzmann equation is derived from the Liouville equation using the technique of time smoothing. The solution of the Boltzmann equation is given in terms of bracket integrals and the entropy production formulated in terms of the perturbation to the distribution function. The bracket integrals are not explicitly evaluated in this paper but a first order result valid for a mixture of spheres of equal diameters gives for the leading term of the diffusion coefficient D=D0/g0(2)(σ) with D0 the dilute gas diffusion coefficient, and g0(2)(σ) the pair correlation function evaluated at contact. This leading term is in agreement with the corresponding leading terms for the thermal conductivity and shear viscosity of a one component hard sphere fluid, which also differ from the dilute gas coefficients by the factor [g0(2)(σ)]—1. The results quoted in this abstract are the leading terms and do not include all contributions of order v—1.
f
2 Configuration in a Crystalline Field
Authors: Satten Robert A. , Margolis Jack S.
Published: January 2005

The matrix representation of a 4th and 6th degree octahedral potential in a complete basis of f2LSJ functions belonging to a particular row of each of the 5 irreducible representations of the octahedral group Oh is presented. The matrices are 7×7, 3×3, two of 9×9, and 12×12 when spin-orbit and electrostatic interaction are included. Bases for the 5 irreducible representations are presented as linear combinations of M states for integral J values ranging from 0 to 6. Reduced matrix elements (independent of M or row of representation) are also given including a 2nd degree potential as well so that matrices for any other symmetry can readily be formed in the f2 configuration. Sufficient information is given to define the phases of the states so that other interactions such as spin-orbit can readily be included.
Infrared Spectra of Metal-Chelate Compounds. I. A Normal Coordinate Treatment on Bis-(Acetylacetonato)-Cu(II)
Authors: Nakamoto Kazuo , Martell Arthur E.
Published: January 2005

A normal coordinate treatment on the chelate ring of bis-(acetylacetonato)-Cu(II) gives calculated frequencies in good agreement with the observed ones in the 1700 and 350 cm—1 range obtained with NaCl, KBr, and CsBr optics. In order to assign the observed bands and to see the coupling between various vibrational modes, the L matrices and the potential energy distribution, Lii2Fi were calculated for all the in-plane vibrations. The results reveal that (1) the band at 1580 cm—1 previously assigned to asym. CO stretching is asym. CC stretching, (2) the bands at 684 and 654 cm—1 formerly suggested to be metal-oxygen stretching modes are metal-oxygen stretching vibrations coupled with ring deformation and CCH3 bending modes, respectively, and (3) a new band found at 455 cm—1 is the sym. Cu–O stretching mode. By comparing the force constants of the Cu–O stretching vibration with those of metal-nitrogen and metal-carbon bonds of other compounds, it is suggested that the Cu–O bond in this compound has double bond character.
Vibrational Distribution in Late Nitrogen Afterglows
Authors: Young R. A. , Clark K. C.
Published: January 2005

The late portion of long afterglows in nitrogen at a pressure of 1 mm Hg has been investigated spectroscopically, revealing that during 140 sec of decay no change occurs in the characteristic relative vibrational distribution of the N2 (B 3Π→A 3Σ) 1st positive bands. A common excitation mechanism for all levels is required; it cannot depend upon known metastable particles formed in the initial discharge or generated during the decay.
Excitation of the Auroral Green Line in Nitrogen Afterglows
Authors: Young R. A. , Clark K. C.
Published: January 2005

Production of the auroral green line of OI (1D—1S, 5577 A) is observed during long (30-sec) afterglows in a static system containing nitrogen and small amounts of oxygen. Relative to the intensities of the N2 1st positive bands, the measured intensities of 5577-A and the NOβ bands increase with time. The long period of observation definitely eliminates the initial discharge as a possible source of the metastable oxygen atoms, and their chemical excitation in the afterglow volume is established. A probable process consistent with observations is that involving collision of N atoms with vibrationally excited NO molecules. This mechanism is discussed as a possible source of 5577 A in the airglow.
Light Scattering by Anisotropic Inhomogeneities in Thin Polymer Films under Strain. I. Simple Elongation
Authors: Bhatnagar Hari L.
Published: January 2005

Inhomogeneities in thin polymer films are assumed to have two different polarizabilities, one longitudinal and the other transverse. A distribution function for orientation of these anisotropic inhomogeneities is obtained as a function of degree of strain and utilized to obtain average scattered intensity. Expressions for differential cross sections of scattering which have been defined are derived.
Some Considerations of Unimolecular Rate Theory
Authors: Buff Frank P. , Wilson David J.
Published: January 2005

It is the purpose of this paper to examine the pressure dependence of the rate constant k of unimolecular decompositions within the framework of the generalized Lindemann mechanism. For trace amounts of reactive polyatomic molecules possessing very small equilibrium fractions of reactive states, the observed k may be identified with the lowest eigenvalue of the relaxation spectrum. After an examination of the Kassel and Slater microscopic decomposition frequencies (m.d.f.'s), this approach is applied to the strong collision mechanism which is a common feature of both theories. Finally, the lowest eigenvalue is calculated for the inefficient stepwise activation mechanism in combination with the simple Kassel m.d.f. The pressure dependence of k on a reduced basis is found to be relatively insensitive to the details of the activation mechanism employed. The effect of less efficient processes in the intermolecular energy transfer and of anharmonicities in the intramolecular energy transfer tend to broaden the transition range of k between the high- and low-pressure limits.
Hydrogen Atom Abstraction Reactions by Cyanide Ion-Radicals
Authors: Martin T. W. , Melton C. E.
Published: January 2005

Ion-molecule reactions of low energy (0–0.15 ev) CHN+ and CH3N+ are shown conclusively to follow a hydrogen atom abstraction mechanism of the type, XH++YH→XH2++Y. These reactions are presumably bimolecular being first order with respect to each reactant over the pressure range 10—7—10—3 mm Hg. The rates of these reactions are markedly influenced by the molecular structure of both the cyanide ion and the hydrogen donor (YH). Ion-molecule reactions of this type are similar to the hydrogen atom abstraction processes of free radicals, but differ in having no appreciable temperature coefficients (in the range of 100–215°C), and in having much larger rate constants. On the basis of this study, chemical species having unpaired electrons whether charged (ion-radicals) or uncharged (free radicals) are shown to undergo similar types of reactions. Possible implications of these observations to the field of radiation chemistry are discussed.
Estimated Electron Affinities of the Light Elements
Authors: Glockler George
Published: January 2005

Estimates have been made of the electron affinities of the following elements: He(∼+0.), Li(0.5), Be(∼+0.), B(0.3), N(0.2), Ne(∼+0.), Na(0.7), Mg(∼+0.), Al(0.4), Si(1.9), P(0.8) ev. The known electron affinities of the other elements of the first two groups of the periodic table form the basis of the graphical method. It involves the variation of screening constants derived from the ionization potentials of isoelectronic sequences.
Kinetic Studies of Hydroxyl Radicals in Shock Waves. III. The OH Concentration Maximum in the Hydrogen-Oxygen Reaction
Authors: Schott Garry L.
Published: January 2005

The chemical reaction zone in shock waves in H2–O2–Ar mixtures has been studied in detail using an ultraviolet line absorption technique to measure the OH radical concentration. The observed reaction course consists of an induction period followed by a sharp rise of [OH] to a maximum and then slow disappearance of OH. The [OH] maxima measured in rich, lean, and stoichiometric mixtures at 1000∘≦T≦2600∘K and over a sevenfold range of density show that the reaction occurs in two distinct steps. The intermediate condition, in which [OH], [H], and [O] reach values greatly in excess of their equilibrium ones, is approximately a state of equilibrium among the three independent bimolecular reactions which is reached before any significant recombination has occurred. The relationship of these results to experiments near the explosion limits and in flames is emphasized. The occurrence of this overshoot in atom and free radical concentrations, which is very pronounced in hydrogen-oxygen flames but is not observed in many hydrocarbon flames, is related to the decrease in number of moles which occurs in the oxidation of hydrogen but not of most other fuels.
Measured Transition Probabilities for the Schumann-Runge System of Oxygen
Authors: Treanor Charles E. , Wurster Walter H.
Published: January 2005

Transition probabilities for the Schumann-Runge system of O2 have been measured in absorption in the wavelength region 2650–3900 A. Oxygen was heated in a shock tube to temperatures up to 4500°K, thereby populating high vibrational and rotational levels. Absorption spectra were photographed using a high-speed flash lamp and a large Littrow quartz spectrograph. Transition probabilities for the bands of three sequences, associated with the zero, 1st, and 2nd vibrational levels of the excited electronic state, yield an f value of 0.048±0.008 which, when corrected for wavelength dependence, is about ⅓ that determined in the vacuum ultraviolet. This corresponds to a decrease in transition probability with increasing internuclear separation. Line-width variations with temperature and density have also been measured. The optical diameter for O2–O2 collisions was determined as 6 A and for O2–O collisions as 10 A.
Crystalline Transitions and Mechanical Resonance Dispersion in Vinyl and Ethyl Stearate
Authors: Fitzgerald Edwin R.
Published: January 2005

Dynamic shear compliance measurements on vinyl and ethyl stearate yield results depending critically on the particular crystalline modification in which these materials exist at the time of measurement. When first crystallized from the melt the materials are in a metastable state and only a few very small resonance dispersions are found in the range 50 to 5000 cps. At later times many large resonances occur; the largest is in the vicinity of 300 cps for both vinyl and ethyl stearate. While vinyl stearate is in its metastable state (about 60 days) a reversible transition takes place at 24.85±15°C such that above this temperature there are no resonances from 50 to 600 cps, but below the transition point the large resonance near 300 cps always appears. A break in the slope of density-temperature curves for vinyl stearate occurs between 25 and 24°C indicating that a transition occurs in the vinyl stearate while in its β form (with the molecules tilted with respect to the planes formed by the terminal groups). X-ray powder diffraction photographs show no changes in the long spacing between planes so the transition must involve alterations in cross-sectional packing of the chains or a change from a monoclinic to triclinic unit cell rather than a variation in angle of tilt. While the details of the crystalline modification at 24–25°C are not as yet sufficiently clear to define a specific mechanism for the resonance phenomena, the results do prove conclusively that the dispersions are intimately connected with the crystalline state of the material. Eventually a kind of mechanical spectroscopy may be evolved yielding information on the actual crystalline state of solids in much the same way that electromagnetic spectra now aid in determinations of molecular structures.
Thermodynamic Properties of Trifluoromethanethiol from 12°K to Its Boiling Point. Entropy from Molecular and Spectroscopic Data
Authors: Dininny R. E. , Pace E. L.
Published: January 2005

The heat capacity of trifluoromethanethiol has been measured from 12° to 227°K. The heat of fusion at the triple point temperature, 116.04°K, was 1177 cal mole—1. The heat of vaporization at the normal boiling point, 235.16°K, was 4798 cal mole—1. The vapor pressure has been measured, and the data are represented by the equation log10pmm=(−1352.568/T)−2.686918 log10T+15.00409. The entropy of trifluoromethanethiol gas calculated from the calorimetric data was 69.45±0.17 eu at 235.16°K. The result calculated from spectroscopic data and structural parameters for the molecule was 70.19 eu. The discrepancy of 0.74±0.17 eu has been attributed to a potential barrier of 1540±260 cal mole—1 restricting the internal rotation of the trifluoromethyl group.
Experimental Study of the Shape of the F-Band Absorption in KCl
Authors: Konitzer John D. , Markham Jordan J.
Published: January 2005

The optical absorption due to F centers in KCl at temperatures between 4°K and 377°K has been measured. The authors believe they have eliminated the K band, and obtained the absorption due to transitions from the ground to the first excited state. The method of preparing ``pure'' F centers is discussed. The halfwidth, the point of maximum absorption, and the zeroth, first, and second moments have been measured in the above temperature range. The data establish Smakula's formula on a firm experimental basis for this center. The half-width in ev is given by the relation 0.163 [coth(71.0/θ)]12, while the point of maximum absorption is at 2.340–0.027 coth(71.0/θ), where θ is the absolute temperature. An equation has been found from which one may calculate the F band absorption. The shape of the band is temperature independent and is approximated by the low temperature form predicted by Pekar. The data on the whole support a generalized theory. The authors believe that the F band shape is due to the interaction of the F electron with localized modes whose average ground state frequency is 2.96×1012 sec—1.
Theory of the Heat of Transport of Electrolytic Solutions
Authors: Helfand Eugene , Kirkwood John G.
Published: January 2005

The limiting concentration dependence of the heat of transport of an ionic component of a dilute solution of electrolyte is determined. The theory is based on recasting the Bearman-Kirkwood statistical mechanical expression for the heat current into a form linear in the particle diffusion currents and identifying the coefficients with the heat of transport. Ion-ion interactions are treated exactly to order c½ by using a nonequilibrium correlation function determined from the Debye-Hückel radial distribution function by Brownian particle theory. A hydrodynamical model is employed for the analysis of the effect of ion-solvent interactions. Indications are that the latter contributions are often, but not always, negligible. There is accord between the theory and experimental data.
Semiempirical Calculation on the Electronic Structure of the Nitrogen-Containing Heterocyclic Molecules. IV. Electronic Structure of Pyridine
Authors: Anno Tosinobu
Published: January 2005

The semiempirical theory on the electronic structure of the nitrogen heterocycles, proposed in Part I of this series, is applied to pyridine. Only the singlet levels are considered in this paper, deferring the discussions on the triplet levels to a later publication. Doubly excited as well as singly excited configurations are taken into CI calculation. The hybridization parameter λ of the nitrogen nonbonding AO determined so that the calculated value of the lowest singlet-singlet n—π transition energy agrees with the experimental value is +0.5439 which corresponds to 22% s character of the nitrogen nonbonding AO. By assuming this value of λ, the lower singlet levels of this molecule are calculated and compared with experiment. The calculation shows that a hidden n—π transition (1A2—1A1 transition) exists in the neighborhood of the strong 4.8-ev band which is assigned to a π—π transition.
Correlation of Rates of Intramolecular Tunneling Processes, with Application to Some Group V Compounds
Authors: Berry R. Stephen
Published: January 2005

A method is presented whereby the WKB expression for tunneling frequencies permits correlation of these frequencies for members of homologous series of molecules. The necessary data required are the tunneling rate for one member of the series, and structural parameters and vibrational frequencies for all members of interest. The method is applied to ND3, NF3, PH3, and AsH3, using NH3 as the molecule whose frequency is known. The method also is used to support the hypothesis that pseudorotation occurs in the trigonal bipyramids PF5 and PCl5.
NMR Chemical Shifts of Aluminum: Experimental Data and Variational Calculation
Authors: O'Reilly D. E.
Published: January 2005

Chemical shifts of Al27 for aluminum alkyl halides, halides, alkyls, alkoxides, AlH4—, and Al(OH)4— are given. The magnitude of the resonance line width of aluminum compounds as liquids or in solution is indicative of the cubic or noncubic molecular symmetry around the Al27 nucleus. The chemical shift of Al27 in AlH4— is calculated by a variation procedure using both valence bond and molecular orbital type wave functions. Requirements on variational functions due to time reversal and inversion symmetry are given. Factors determining the shifts of other aluminum compounds are discussed.
Emission Spectra of N2, O2, and NO Molecules Trapped in Solid Matrices
Authors: Broida H. P. , Peyron M.
Published: January 2005

Molecular systems are observed in emission in solid products from a gas discharge trapped at liquid helium temperature. Previous tentative molecular assignments have been checked with the help of isotopic substitutions of oxygen and nitrogen. The Herzberg system (A bands) of oxygen (A 3Σu+ — X 3Σg—) is analyzed and the molecular constants are derived for a molecule trapped in a nitrogen matrix. Another system (M bands) is attributed to the NO molecule (4II — X 2II).
Infrared Spectra of Alkyldiboranes. I. Monomethyldiboranes
Authors: Lehmann Walter J. , Wilson Charles O. , Shapiro I.
Published: January 2005

The infrared spectra of five isotopic derivatives of monomethyldiborane (CH3B210H5, CH3B2H5, CH3B2D5, CD3B2H5, and CD3B2D5) are analyzed and frequency assignments are made through correlation with trimethylborane and terminally substituted B2H5D and B2D5H.
Steady-State Studies by EPR on the Photodissociation of Some Alkyl Hydroperoxides
Authors: Piette L. H. , Landgraf W. C.
Published: January 2005

A new steady-state method for studying dynamic photochemical processes by EPR is discussed. The EPR spectra of some photolysed alkyl hydroperoxides are obtained and the free radical intermediates identified as alkoxy radicals.

Recombination rate constants of ∼105 liters/mole sec were obtained with activation energies of ∼4 kcal. A new EPR spectrometer with improved sensitivity capable of photoirradiation in situ and variable temperatures is discussed.
Mass Spectrometric Studies of Ionic Intermediates in the Alpha-Particle Radiolysis of Ethylene
Authors: Melton C. E. , Rudolph P. S.
Published: January 2005

Two techniques were used for the elucidation of ion-molecule reaction mechanisms in the alpha radiolysis of C2H4 in the new alpha-particle mass spectrometer. The corresponding variations in the percent of primary, secondary, and tertiary ions over a tenfold pressure range (to 0.1 mm) were used to postulate the reaction mechanisms. Mixtures of the C2 hydrocarbons were employed to increase the relative concentrations of a specific reactant ion, thus independently confirming the postulated mechanisms. Polymeric ions as large as C5H9+ were observed. Conclusions as to reaction mechanisms drawn from this study are compared to those drawn from the appearance potential technique used in the electron impact studies. Values of the rate constants are also compared for several secondary reactions.
Mayer's Ionic Solution Theory Applied to Electrolyte Mixtures
Authors: Friedman Harold L.
Published: January 2005

For solutions of a mixture of two electrolytes with a common ion, the characteristic free energy function is ΔmGex, the change in excess free energy on forming the solution from solutions of the single electrolytes. This is closely related to ΔmS, where S is the cluster integral sum of the Mayer theory. For systems that conform to Harned's rule the contributions of most of the cluster integrals to ΔmS are negligible. The form of the principle contribution to ΔmS depends on whether the two electrolytes have the same charge type (symmetrical mixtures) or not.

The equations for symmetrical mixtures which nearly conform to Harned's rule are developed in detail, first for the general case in which the components of the potential of average force are arbitrary and then for the special case of hard sphere ions, designated as the primitive model for electrolyte solutions. The leading term of ΔmS is determined by the difference in short-range interaction of pairs of ions of the same charge and does not depend at all on the common ion. Another general result is that ΔmGex/I2 does not vanish as I→0, as has sometimes been expected on the basis of the Brønsted principle of specific ion interaction, but approaches a finite value in a way that is governed by a higher-order limiting law.

Comparison with experiment is made on the basis of the primitive model. The results are roughly consistent with the free energy effects in alkali metal chloride mixtures if it is assumed that the effective radii of the alkali metal ions are about double their crystal radii.
Vapor-Liquid Equilibrium of Benzene-2,2,4-Trimethylpentane Mixtures
Authors: Weissman Stanley , Wood Scott E.
Published: January 2005

The vapor-liquid equilibria of solutions of benzene and 2,2,4-trimethylpentane have been measured at 10 deg intervals from 35 to 75° over the entire range of composition. The excess thermodynamic functions have been calculated from these data for the processes of mixing at constant pressure and at constant volume. All these functions are positive over the whole range of composition and decrease with increase of temperature. The behavior of this system is in qualitative agreement with the predictions of theory.
Out-of-Plane Vibrations of Molecules Containing Planar XY4 Rings. I. The Normal Vibration Problem
Authors: Stewart James E.
Published: January 2005

The F and G matrix elements for out-of-plane vibrations of molecules containing planar, five-membered heterocyclic rings of the type XY4 have been derived under the assumption that substituents on the ring can be treated as point masses.
Magnetic Investigations of Spin-Free Cobaltous Complexes. II. Tetrahedral Complexes
Authors: Holm Richard H. , Cotton F. Albert
Published: January 2005

The magnetic moments of 17 tetrahedral complexes of Co(II) have been carefully measured, most of them over a temperature range. The Curie-Weiss law is found to hold in all cases where the temperature dependence was studied. The variations of the orbital contribution to the moment are shown to be in accord with expectation from ligand field theory (Schlapp and Penney), and the utility of the results in correlating magnetic properties, spectra, and structures of Co(II) complexes is briefly discussed.
Electronic Energy Levels and Crystal Quantum States of Tm (IV)
Authors: Gruber John B. , Conway John G.
Published: January 2005

To date limited agreement has been obtained between theory and experiment for 4f→4f transitions for Tm (IV) (4f12). It is clear from the considerations that have appeared so far in the literature that intermediate coupling is important in the case of Tm (IV). Solutions of the intermediate field equations yield ζ4f=2700 cm—1, F2=450 cm—1, and x=(ζ/F2)=3. Experimental agreement to ±200 cm—1 was obtained.
Spectra Emitted from Rare Gas-Oxygen Solids during Electron Bombardment
Authors: Schoen L. J. , Broida H. P.
Published: January 2005

Light emission from rare gas solids containing small amounts of oxygen has been excited by an electron bombardment technique. The Herzberg bands of oxygen and a line group believed to be the 1S→1D transition of the neutral oxygen atom form the strongest features of the observed spectra. In a neon matrix, the Second Negative system of O2+ has been identified. The effect of the various solids on the vibrational structure of the Herzberg bands is discussed.
Higher Ionization Potentials of Linear Triatomic Molecules. I. CO2
Authors: Tanaka Y. , Jursa A. S. , LeBlanc F. J.
Published: January 2005

Four new Rydberg series, in addition to series already known, have been observed. One of them, which corresponds to the vibration series of Henning's series, converged to 18.23 ev, while the other three converged to a value of 19.38 ev and yielded an additional higher ionization potential. All the observed values were compared with the theoretically calculated values. Several new progressions of absorption bands were also observed.
Higher Ionization Potentials of Linear Triatomic Molecules. II. CS2, COS, and N2O
Authors: Tanaka Y. , Jursa A. S. , LeBlanc F. J.
Published: January 2005

Four ionization potentials for the CS2 molecule, three for the COS, and three for the N2O were determined by an analysis of Rydberg series of the respective molecules. Our value for the first ionization potential of CS2 agrees very well with the previous spectroscopically determined value; however, there was disagreement between our value for the first ionization potential of N2O and that determined previously.

Several progressions of absorption bands for each of the molecules were also observed.
On the Nature of Solvent Effects in the Proton Resonance Spectra of Unsaturated Ring Compounds. I. Substituted Benzenes
Authors: Schaefer T. , Schneider W. G.
Published: January 2005

The relative chemical shift between the resonances of ortho and meta hydrogens in certain para-disubstituted benzenes are markedly dependent on solvent and concentration. This behavior, which is observed also in other substituted benzenes, is characterized by a pronounced shift of some proton signals to low field in acetone solution and to high field in benzene solution. In compounds of the type[Complex chemical formula]where X is an electron-withdrawing substituent, the resonance signals of protons meta to the X substituent are displaced selectively in donor solvents. When the CH3 group is replaced by F, both ortho and meta hydrogens show pronounced shifts. The observations can be interpreted in terms of a specific molecular association involving hydrogen bonding. Although generally these bonds appear relatively weak, for some compounds the hydrogen-bond strength is estimated to be comparable to those formed by chloroform in donor solvents. These effects offer a valuable practical aid in proton resonance measurements since in such compounds, within limits, it is possible to alter the relative chemical shifts by a suitable adjustment of solvent conditions.
Unimolecular Decomposition of Chemically Activated sec-Deuterobutyl Radicals from D Atoms plus cis-Burene-2
Authors: Harrington R. E. , Rabinovitch B. S. , Diesen R. W.
Published: January 2005

Chemically activated sec-deuterobutyl radicals were produced at 25°C by the reaction of D atoms with cis-butene-2. These vibrationally excited species contain an increment of energy above that of the corresponding light radicals as formed from H plus cis-butene-2 in a previous study [B. S. Rabinovitch and R. W. Diesen, J. Chem. Phys. 30, 735 (1959)]. Apparent rate constants for the unimolecular decomposition to propylene of the deuterobutyl radicals were obtained as a function of pressure, relative to the collision induced stabilization process. Theoretical values for the rate constants at the limits of high and low pressures were calculated using a direct count for the density of vibrational energy levels. The calculated and experimental results are compared with one another, and with the results of the previous study of the sec-butyl radical decomposition. The expected energy effect is observed; the deuterobutyl radicals appear slightly more monoenergetic than the equivalent nondeuterated species.
Observations of the Thermal Behavior of Radicals in Gamma-Irradiated Ice
Authors: Siegel Seymour , Baum Lillian H. , Skolnik Sol , Flournoy John M.
Published: January 2005

Ice was subjected to γ radiation at 77°K and the EPR spectra of the radicals produced were examined as a function of temperature. The spectrum consisted essentially of a doublet centered at g=2.008±0.002 and split by 40 gauss; the corresponding spectrum of irradiated D2O consisted of a triplet with approximately 6 gauss between adjacent lines. The doublet decayed rapidly above 100°K leaving a residual broad line which was thermally stable until approximately 145°K. The main spectrum has been attributed to the OH radical and the residual line assigned to the HO2 radical. The decay process of the OH radicals was shown to follow the rate law d(OH)/dt=—k(OH)32 where k=8.5×1012 exp—6000/RT (liter/mole)½ sec—1. The magnitude of the rate constant was shown to be a function of the total irradiation damage experienced by the ice sample.

Stabilization of OH radicals at 77°K was studied as a function of total irradiation dosage; saturation is reached at an OH concentration of 1.8×10—3M or 0.003 mole %. The EPR spectrum of a frozen aqueous NO solution was also observed; it consisted of a broad line centered at approximately g=2.08.
Nuclear Magnetic Resonance in B2O3–H2O Glasses and Boric Acids
Authors: Silver A. H.
Published: January 2005

The class of materials B2O3–H2O has been investigated over the range B2O3 to B2O3·3H2O. This includes ``dry'' glassy B2O3, ``wet'' glassy boron oxide of approximate composition B2O3·½H2O, monoclinic and orthorhombic forms of metaboric acid, B2O3·H2O, and triclinic orthoboric acid, B2O3·3H2O. The nuclear quadrupole interaction of the B11 isotope was measured and comparisons of the structures are made on the basis of this interaction. It is shown that all substances contain similar planar BO3 triangular units. The presence of O–H–O hydrogen bonds, as in B2O3·3H2O, has a minor effect on the boron nuclear quadrupole interaction. It is concluded that BO4 tetrahedral units exist in several of the wet glass samples as well as in monoclinic metaboric acid.