bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic Significance of Heat of Transport in Interstitial Solid Solutions
Authors: Raleigh D. O. , Sommer A. W. 
Published: January 2005

The theoretical relationships involved in thermal diffusion have been re-examined. It has been shown from strictly thermodynamic considerations that in dilute solid solutions the quantity ``heat of transport,'' or Q*, can be expressed as the sum of two distinct contributions.
One of these is the partial molal heat of solution of the solute, referred to pure solute as the standard state. The second is a portion, designated the thermal gradient effect, which exists independent of solubility relationships. The latter has been shown to be obtainable from a plot of log solute activity vs reciprocal temperature when the activity is referred to pure solute as the standard state. Comparison of heat of transport with heat of solution in interstitial solid solutions where data are available indicate that the thermal gradient effect is small in these systems.
Relation between ESR Spectra and Molecular Orientation in Irradiated Polyethylene
Authors: Kashiwagi Michio 
Published: January 2005

Measurements have been made of the electron spin resonance spectra of irradiated polyethylene filaments with various draw ratios. The feature of the spectra is that the doublet splitting in each component of a quintet structure depends on the degree of molecular orientation in filaments. This can be ascribed to σ-proton anisotropy in alkyl radicals mainly trapped in irradiated polyethylene.
From the information about CH radicals of irradiated organic crystals and the molecular orientation of polymers, the relation between the doublet splitting D and the degree of molecular orientation f is obtained as follows: D=13.9(1−0.35f)12+5.1(1−0.65f)12 (gauss)for the high-density polyethylene, consisting predominantly of the crystalline regions, and the spin density of the central carbon atom of the radical is 0.70.
Departure from the Steady State in Chain Reactions with Two or More Radicals
Authors: Giddings J. Calvin , Shin Hyung Kyu 
Published: January 2005

A method used previously for obtaining the departure from steady-state kinetics with one reactive intermediate is extended to chain reactions with two or more intermediates or radicals. This method is applied to the H2–Br2 reaction and to the pyrolyses of methane, ethane, and acetaldehyde. It is found that serious departures from steady-state conditions occur in the experimental range of ethane decomposition and H2—Br2 reaction. The departure is serious for all such processes in the very fast reaction, high-temperature region.
Using a hypothetical reaction scheme with characteristics similar to those of most chain reactions, approximate equations are obtained for the initial transients connected with the build up of radicals. The relationship between steady-state departure, both during and after the transient period, and the cumulative extent of reaction are explored for this reaction.
Electron Distribution in the C–Cl Bonds of CH2Cl2 and Derivation of Matrix Elements Off-Diagonal in J for Two Quadrupolar Nuclei in an Asymmetric Rotor
Authors: Flygare W. H. , Gwinn William D. 
Published: January 2005

The microwave spectrum of methylene chloride has been reinvestigated with the high-resolution spectrometer now available. The diagonal quadrupole coupling constants of Cl in CH2Cl235 were remeasured under high resolution, giving χaa=—41.07±0.01 Mc, χbb=1.24±0.02 Mc, and χcc=+39.83±0.01 Mc. By using second-order perturbation theory, the off-diagonal element χab was measured directly and was —52±3 Mc. These results show that the C–Cl bond in methylene chloride is not bent within an experimental error of 1°.
Matrix elements off-diagonal in J, of the quadrupole interaction Hamiltonian for two quadrupolar nuclei, are derived using Racah coefficients. The I1=I2=32 matrix elements are evaluated and listed in the Appendix.
Pyrolysis of Di-tertiary Butyl Peroxide: Temperature Gradients and Chain Contribution to the Rate
Authors: Batt Leslie , Benson Sidney W. 
Published: January 2005

An investigation of the pyrolysis of di-tertiary butyl peroxide over the range 27–130 mm Hg pressure and 130–160°C has shown that the experimental stoichiometry is 3.0 rather than the previously reported 2.9. Trace amounts of t-BuOH (0.5 to 1.0%), isobutylene oxide (1–2%) and t-BuOMe (0.02%) have been identified as well as biacetonyl and small amounts of other ketones. By using spherical vessels and octopus vessels of large surface/volume ratio, it is shown that the previously reported scatter in the Arrhenius parameters can be attributed to temperature gradients established in the vessel. This is confirmed by direct measurement of the gas temperature with fine thermocouple wires in thin glass wells.
The best rate constant for the first-order decomposition in the absence of temperature gradients is given by: logk=15.6–37 400/4.575T sec—1 with an uncertainty in E of about ±0.5 kcal. Assuming zero activation energy for the recombination of t-butoxy radicals, this gives the peroxide bond dissociation energy of 37.4±0.5 kcal/mole. An estimate of the standard entropy change for dtBP→2 t-BuO gives the remarkably low value of 108.2 l/mole-sec for the Arrhenius factor for the recombination of t-BuO radicals. It is shown that such a low value is needed to explain the concordance in Arrhenius parameters for liquid and gas state pyrolyses.
The isobutylene oxide puts a limit to the chain contribution of about 1 to 2%. The t-BuOH and t-BuOMe yields permit independent estimates of the rate of dissociation of t-BuO radicals in fair agreement with each other and other investigations.
The explosion limits for the decomposition are estimated to be about 7.5 atm (150°C). The present work confirms the importance of temperature gradients in contributing to spurious activation energies for very exothermic reactions.
Deuteron Quadrupole Coupling in Diatomic ``Hydrides''
Authors: Kolker H. J. , Karplus M. 
Published: January 2005

For LiD and DF, the deuteron quadrupole coupling constant (eqQ/h) has been calculated with single-determinant SCF-LCAO-MO functions. The results obtained are 38 kc/sec for LiD and 373 kc/sec for DF, in rather satisfactory agreement with the recently measured values (30±3 kc/sec for LiD and 340±40 kc/sec for DF). To evaluate the molecular integrals required for the determination of q, a formulation in terms of confocal elliptic coordinates was used. This made possible the introduction of certain auxiliary functions that are very convenient for the calculation of field gradient and related integrals. A comparison of the quadrupole coupling constants obtained with a number of different molecular orbital functions is presented. The results demonstrate the importance of using atomic basis functions with exponents optimized for the molecular system and suggest that exact Hartree-Fock functions may yield relatively reliable values for field gradients and other one-electron weak-interaction parameters.
A calculation of the field gradient at the Li nucleus (q = —0.0401 a.u.) yields a value of —3.7×10—26 cm2 for the Li7 quadrupole moment when combined with the coupling constant measurement of +346±1 kc/sec.
Secondary Reactions in the Ion Chamber of a Mass Spectrometer
Authors: Marmet P. , Morrison J. D. 
Published: January 2005

A study has been made with a mass spectrometer of the ionization efficiencies of a number of gases, using an ion source incorporating an electron velocity selector. It is found that the shapes of the I.E. curves are affected by numerous instrumental factors. These have been examined, and the data lead to the following conclusions. Ions may be formed on the walls of the ionization source, at energies different from those corresponding to the ionized states of the free molecules. Charge transfer reactions may occur between these bound ions, and other neutral molecules on the walls. The surface ions may subsequently become detached, and are detected at the collector of the mass spectrometer.
It is suggested that these ions formed by such processes may account for many of the spurious ``breaks'' often found in measured I.E. curves. The sharpness of the structure in the present curves indicates that the half-width of the electron energy spread is of the order of 0.02 ev.
Studies of Hydrogen Peroxide: The Infrared Spectrum and the Internal Rotation Problem
Authors: Redington R. L. , Olson W. B. , Cross P. C. 
Published: January 2005

Several hydrogen peroxide infrared absorption bands have been obtained under 0.2 cm—1 resolution. They demonstrate both doubling due to internal rotation and effects due to the inertial asymmetry. The ground-state rotational constants are found to be: A″=10.068 cm—1, B″=0.8740, C″=0.8384. These parameters indicate a wide dihedral angle for H2O2, as proposed in the following structure: OO bond=1.475 A, OH bond=0.950 A, dihedral angle=119.8°, and OOH angle=94.8°.
The constants are applied to the microwave data for H2O2 and the deuterated species. The ground-state splitting is found to be 11.44 cm—1, and this, used with the recently reported torsion at 317 cm—1, yields the barriers hindering internal rotation. They are Vcis=1300 cm—1 and Vtrans=300 cm—1. A simple correlation of the infrared doublings is attempted.
Radiolysis of Methylcyclohexane. I. Liquid Phase
Authors: Freeman G. R. 
Published: January 2005

The gamma-radiolysis of liquid methylcyclohexane has been studied over the dose range 0.40 to 35.0×1019 ev/ml. The initial 100 ev yields of the products are: H2, 4.80±0.07; (1-methylcyclohexene+methylenecyclohexane), 2.65±0.15; (3-methylcyclohexene+4-methylcyclohexene), 0.83±0.10; open chain heptene′, 0.33±0.02; open chain heptene″, 0.31±0.04; bi-methylcyclohexyl, 0.75±0.05; methylcyclohexylheptene, 0.13±0.02. Methylcyclohexyl-methylcyclohexene was a secondary product, resulting mainly from reaction of methylenecyclohexane and partly from reaction of 1-methylcyclohexene.
The values of the ratios of the olefin yields to the ``dimer'' yields in the cyclohexane and methylcyclohexane systems were compared with values of disproportionation to combination ratios for moderately bulky alkyl radicals in the gas phase. It was concluded that the major portions of the olefins and ``dimers'' in the radiolytic systems were formed by the disproportionation and combination of radicals. A steric hindrance effect probably has a small influence on the rate of the combination reaction.
It was illustrated that a polymerization reaction occurs, involving the olefinic products, although the polymer could not be characterized. The relative significance of the polymerization reaction increases with decreasing dose rate.
Theory of Multicomponent Fluid Mixtures. III. A Pseudo Pair Potential
Authors: Salsburg Zevi W. 
Published: January 2005

This article considers some further consequences of the exact statistical mechanical theorem (given in article I of this series) which relates the thermodynamic properties of a mixture to those of a fictitious pure fluid by defining an intermolecular potential function (called the pseudopotential) for this pure fluid. Starting with the perturbation series for the pseudopotential all terms which can be written as a sum of pairwise interactions are collected and summed to give a simple closed expression for a pseudo pair potential function for the mixture.
Retaining only these pair terms and neglecting all triplet and higher-order interactions in the pseudopotential gives an approximation which is a rigorous lower bound to the correct pseudo-potential for all configurations. For mixtures of molecules with rigid cores this pseudo pair potential is also a potential with a rigid core, but with a diameter equal to that of the smallest molecule. The extreme nature of this approximation, which severely limits the application of the theory at high densities and pressures, is shown to be a direct consequence of neglecting triplet interaction terms in the pseudopotential. The nature of the limitations inherent in any approximation of the pseudo-potential by a sum of pair-wise interactions is clarified by comparing these results with the random mixing approximation to the pseudopotential which is known to give an upper bound for all configurations. The free-volume theory for the pseudo pair potential, resulting from summing the pair terms, for mixtures of rigid spheres is developed. The results of this calculation are compared with recent Monte Carlo calculations for binary mixtures of rigid spheres to illustrate the extremely ``soft'' equation of state which results when triplet interactions are neglected.
Thermoluminescence of Solid Nitrogen after Electron Bombardment at 4.2°K
Authors: Brocklehurst Brian , Pimentel George C. 
Published: January 2005

Solid nitrogen annealed at 20°K and then bombarded with electrons at 4°K gives three glow peaks on warming, at 10°, 14.5°, and 19°K. Unannealed nitrogen gave broader peaks. A feeble, long-lived glow followed the normal afterglow after bombardment at 4°K. Thermal effects during warming were observed in one apparatus with radiation shielding at 77°K, but they were not observed in a much more sensitive apparatus with radiation shielding at 4°K. The thermal effects are probably caused by an anomalous vapor pressure and loss of Dewar vacuum.
The data are discussed with reference to two interpretations, the storage of 2D excited nitrogen atoms and the recombination of 4S nitrogen atoms through diffusion. The latter explanation is preferred and a simple model is offered to account for the three diffusion activation enthalpies implied by the three thermoluminescence peaks.
Study of the Adsorption of Hydrogen, Ethane, Ethylene, and Acetylene on Iridium by Field Emission Microscopy
Authors: Arthur John R. , Hansen Robert S. 
Published: January 2005

A field emission microscope permitting precise control of iridium emitter temperature from 4 to 1700°K was used to study changes in emission patterns and work functions resulting from time and temperature dependent surface reactions in the adsorption of hydrogen, ethane, ethylene and acetylene on iridium.
The qualitative character of the emission patterns indicates a rather uniform covering of the high index faces of iridium by all species studies in the temperature range 70–300°K. Hydrocarbon species, once chemisorbed, are substantially immobile at temperatures below 700°K; above 700°K an intensification of emission pattern, probably due to carbonization, occurs around the edges of the 111 planes.
Iridium surfaces containing adsorbed species were flashed for controlled periods of time to controlled temperatures; characteristic changes in work function resulted which were both time and temperature dependent. These experiments indicate that hydrogen is readily desorbed by iridium above 400°K, and that a large portion of adsorbed ethane is readily desorbed at 100°K, but a residue from adsorbed ethane is not desorbed below 1000°K. For a given flash time, curves representing work function as a function of flash temperature for adsorbed ethylene and acetylene show characteristic differences below 450°K but are very similar above 450°K. Results are interpreted as indicating chemisorption of ethylene, dehydrogenation of chemisorbed ethylene to form chemisorbed acetylene and chemisorbed hydrogen, desorption of chemisorbed hydrogen, dehydrogenation of chemisorbed acetylene and finally crystallization of carbon residue.
On the Applicability of the Temkin-Pyzhev Equation for the Determination of Activation Energies of Ammonia Synthesis at One Atmosphere Pressure
Authors: Brill R. , Tauster S. 
Published: January 2005

It is shown that for measurements at 1 atm pressure, rate constants calculated by means of the Temkin-Pyzhev equation cannot be used for the determination of activation energies in the usual way.
Our experimental values lead to activation energies of about 17 kcal/mole for a doubly promoted catalyst which are in reasonable agreement with those given by Ozaki, Taylor, and Boudart if either the rate equation for low yields of these authors or a simple extrapolation process to very low yields is used to define a rate constant.
Mass Spectrometric Study of the Reactions of BF3(g) with BCl3(g), B(OH)3(g), and B2O3(1)
Authors: Porter Richard F. , Bidinosti Dino R. , Watterson K. F. 
Published: January 2005

Exchange reactions of halogen and hydroxyl with BX3(g) have been studied mass spectrometrically. The major product produced by the reaction of BF3(g) with boric acid at 25°C and pressures of the order of 10—6 atm is B(OH)F2(g). The species B(OH)2F(g) is also formed at higher temperatures when B(OH)3(g) is observable. Equilibria involving the reactions13BF3(g)+23BCl3(g)=BFCl2(g),23BF3(g)+13BCl3(g)=BF2Cl(g),13BF3(g)+23B(OH)3(g)=B(OH)2F(g),and 23BF3(g)+13B(OH)3(g)=B(OH)F2(g),have been studied as a function of temperature. Heats of formation at 298°K for BFCl2(g), BF2Cl(g), B(OH)2F(g), and B(OH)F2(g) are found to be —154.1±1.0, —211.9±2.0, —249.8±2.5, and —260.2±2.5 kcal/mole, respectively.
Reactions of BF3(g) with B2O3(l) have also been studied at pressures between 10—6 and 10—3 atm and temperatures between 400 and 1000°K. Results are consistent with published data from studies with BF3 at pressures near 1 atm and show that (BOF)3(g) is the primary product at both pressure extremities. For the reactionBF3(g)+B2O3(l)=(BOF)3(g),we obtain ΔHT°=3.46±0.30 kcal/mole.
Charge Injection into Organic Crystals: Influence of Electrodes on Dark- and Photoconductivity
Authors: Pope Martin , Kallmann Hartmut P. , Chen Augustine , Gordon Peter 
Published: January 2005

Studies have been made of dark and photoconductivity in thin anthracene single crystals using a Ce4+ solution as one electrode and a 1MNaCl solution as the other electrode. It was found that the Ce4+ electrode was capable of injecting holes into anthracene in the dark, the saturation current at 15 000 v/cm being about 1 μa/cm2. This current was observed when the Ce4+ electrode was at a positive potential. With the same polarity, it was found that there was practically no increase in the saturation current upon illumination of the crystal with 3650 or 4300 A light; at low voltages there was a distinct photoeffect which was attributed to the emptying of polarization producing traps, thus increasing the internal field. The saturation current was proportional to the sixtenths power of the Ce4+ concentration. At low voltages, the current was very small until a certain voltage, referred to as the onset voltage, was reached, after which the current increased rapidly. The onset voltage was larger for the dark current than for the photocurrent. The efficiency of carrier production by the Ce4+ ion was about 10—10 based on a simple collision hypothesis. Possible explanations for this low efficiency were advanced but no definite mechanism was chosen. The use of Ce3+ ion was without effect in increasing either the dark or photocurrent.
Using a positive electrode of I2 in glacial acetic acid, it was found that there was practically no hole injection, in contrast with the marked hole injecting characteristics of the aqueous I2–I— electrode. Furthermore, the Ce4+ and I2–I— electrodes were ineffective with naphthalene. These results are explained by reference to a criterion for hole injection IA—WE—Ex&lt;0, where WE is the work function of the electrode, IA is the ionization energy of anthracene in the solid, and Ex is the externally supplied energy (optical, thermal, electric field).
Molecular-Orbital Theory of Diamagnetism. I. An Approximate LCAO Scheme
Authors: Pople J. A. 
Published: January 2005

An independent-electron molecular-orbital theory is developed for the diamagnetic behavior of electrons in the presence of an applied magnetic field. The molecular orbitals are written as linear combinations of gauge-invariant atomic orbitals, the dependence of the (complex) coefficients on the magnetic field being studied by perturbation theory. By making a systematic set of approximations involving the neglect of some interatomic terms, a general expression is derived for the diamagnetic susceptibility tensor as a sum of atomic contributions. Each atomic contribution is made up of two parts, the first being a diamagnetic (Langevin-type) term and the second being a paramagnetic contribution involving the details of the electronic excited states. At a lower level of approximation, this second term can be expressed in terms of atomic charge densities and bond orders together with a mean electronic excitation energy.
It is pointed out that the theory provides a convenient basis for detailed interpretation of the Pascal constants used for empirical calculations of diamagnetic susceptibilities of large molecules. In addition, a similar treatment of the theory of nuclear magnetic screening leads to an expression for the shielding constant involving a set of localized contributions closely related to corresponding contributions for the susceptibility.
Studies of Metastable Ion Transitions with a 180° Mass Spectrometer
Authors: Coggeshall Norman D. 
Published: January 2005

The decay of metastable ions through transitions giving an ionized fragment and a neutral radical has been investigated with a 180° mass spectrometer. Four aspects of the main problem have been studied. These are: (a) the decay of metastable ions within the ion source to produce a continuous distribution of ``metastable ions''; (b) an examination of the mathematical conditions relating dissociation beyond the ion-source exit slit to the formation of a ``metastable'' peak, to the shape of such a peak, to the cutoff imposed by the analyzer walls and to the length of travel during which detectable dissociation may occur; (c) an examination of the conditions for determining lifetimes with a 180° instrument; and (d) a consideration of the elements leading to the broadness of metastable peaks.
The distribution function resulting from dissociation within the slit drops very rapidly and is ordinarily hidden within the peak due to the daughter ion. The formation of a metastable peak in a 180° instrument results from a low-order dependence of where the ion fragment resulting from dissociation hits the focal plane on the position of dissociation beyond the exit slit. The cutoff mass due to ions striking the walls of the analyzer tube may be readily calculated. In a CEC model 21–103 instrument there is adequate distance of free travel beyond the exit slit to allow the instrument to be used for lifetime measurements. Using repeller voltages up to 120 V, shorter lifetimes than those previously reported have been observed. For the m*=31.9 metastable peak from n-butane, for example, there is evidence that the metastable ions are created in at least three classes, each with its own lifetime. The shortest lifetime observed was of the order of 9×10—8 sec. Evidence has been obtained to indicate that the broadness of the observed metastable peaks is probably the result of the perturbation of focusing conditions by the increased angular spread in the ion beam.
Carbon and Oxygen Isotope Exchange between CO and Ni(CO)4
Authors: Monse E. U. , Spindel W. 
Published: January 2005

The single stage factor α of the carbon and oxygen isotope exchanges between liquid Ni(CO)4 and gaseous CO, according to the reactions Ni(C12O)4+C13O⇌Ni(C12O)3C13O+C12Oand Ni(CO16)4+CO18⇌Ni(CO16)3CO18+CO18,respectively, has been determined: For the carbon exchange,α=1.020±0.002 at−10∘ and α=1.010±0.002 at+10∘.For the oxygen exchange,α=1.005±0.002 at−10∘ and α=1.000±0.002 at +10∘.These data are in good agreement with values calculated from spectroscopic data for Ni(CO)4 and CO.
From the isotope fractionation measured in a packed countercurrent column, the activation energy E for the exchange was estimated. The value of E=12 kcal/mole agrees with the results obtained from kinetic data for the thermal decomposition of Ni(CO)4 and the exchange of Ni(CO)4 with labeled CO. The rate of the thermal decomposition of Ni(CO)4 is assumed to be the rate determining step in the exchange.