bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Area and Particle Size of Evaporated Lead Sulfide Films
Authors: Harada Roy H. 
Published: January 2005

Physical adsorption isotherms of lead sulfide films evaporated in vacuum and through oxygen were measured in order to determine their surface area and particle size. The surface areas of fresh and of annealed vacuum evaporated films were found to increase linearly with film thickness. Annealing the films in vacuum decreased the surface area considerably. The average specific surfaces of the fresh and annealed films were 63 m2/g and 6 m2/g, corresponding to particle sizes of 0.013μ and 0.13μ, respectively. The surface area of fresh films evaporated through oxygen depended upon the rate of evaporation. The average specific surface of the fresh slowly evaporated films was 66 m2/g; for those evaporated faster, it was 118 m2/g. The corresponding particle sizes were 0.012μ and 0.0068μ. When these films were annealed in a closed vacuum system, the specific surface became 12 m2/g and 14 m2/g, corresponding to particle sizes of 0.067μ and 0.056μ, respectively.
For films evaporated through oxygen, the oxygen is chemisorbed on the surface of the film during evaporation. When such a film is annealed sulfur dioxide is evolved and sulfate is formed.
Refinement of the Lennard-Jones and Devonshire Theory of Liquids and Dense Gases
Authors: Taylor William J. 
Published: January 2005

The Lennard-Jones and Devonshire (LJD) theory of liquids represents an advance over the early free-volume theories, in that each molecule is assumed to move in a potential field generated by its neighbors. However, this potential is the static field computed with each neighbor at its equilibrium position (cell center), so that the LJD theory does not take account of the correlation of the motion of neighboring molecules. This correlation problem is treated in the present paper by recasting the exact classical partition function in a form in which the LJD potentials appear in the principal terms, while certain correlation potentials appear in correction terms. The resulting integrals are analogous to those appearing in the conventional theory of an imperfect gas, but with the correlation potential playing the role of the usual intermolecular potential, and the range of integration of each molecule limited to its own cell (where it is also subject to the static LJD potential). A practical method of evaluation of the integrals is developed, based on power series expansions of the factors containing the correlation potentials.
The limitation of each molecule to a single cell (single occupancy) is not an essential feature of the theory. The allowance for multiple occupancy of the cells leads to the communal entropy correction, which has been treated by Pople and others. The present correction for correlation of neighboring molecules is applicable even for single occupancy, and is thus an addition to the communal entropy correction.
The method is compared with Kirkwood's self-consistent field modification of the LJD theory, which takes some account of correlation, but only in an average sense. Comparison is also made with the recent cell-cluster theory of de Boer, which was in fact antedated by the present work (see footnote). The two theories are basically equivalent, in spite of their different formulations. It is felt that the present method puts the integrals in a form more practical for calculation.
Relative Rates of Isomerization of Cyclopropane and Cyclopropane-t1
Authors: Lindquist R. H. , Rollefson G. K. 
Published: January 2005

The relative rates of isomerization of cyclopropane and monotritiated cyclopropane have been determined in the temperature range of 447° to 555°C. The ratio of the rate constants for the two reactions can be fitted by the equation: k/k′=0.63±0.02 exp(825±60/RT).
The marked increase in the temperature-independent term upon tritium substitution is discussed in terms of Slater's unimolecular reaction rate theory and Eyring's absolute reaction rate theory. The possibility of classical vibration coupling causing the observed effect is suggested.
Proton Conductance and the Existence of the H3O· Ion
Authors: Conway B. E. , Bockris J. O'M. , Linton Hedda 
Published: January 2005

Measurements of the conductance of HCl in water, methanol, ethanol, n-propanol, ethylene glycol, glycerol, 1:4 dioxane, acetone, formic, and acetic acids and the respective aqueous-nonaqueous systems have been made as a function of concentration of water and HCl. The degree of anomalous proton conductance decreases with increasing n in CnH2n+1OH, and conductance minima occur in aqueous alcoholic HCl solutions of low H2O content.
Former theories of proton conductance have permitted no quantitative distinction to be made between the rates of classical proton transfer, quantum-mechanical tunneling transfer, and water rotation as rate determining stages. If resonance in H3O· is set up sufficiently quickly after arrival of a given proton at a water molecule, rotation of H3O· cannot be a rate determining step.
Detailed calculations of the rates of classical proton transfer, tunnel transfer, and the rate of rotation of water are made. Classical transfer is much slower and tunnel transfer much faster than corresponds to the observed proton mobility; rotation of hydrogen bonded water molecules near the H3O· ion is the rate determining reaction (preceded and succeeded by fast tunneling of protons). This conclusion is quantitatively consistent with the OH′ mobility in water, and the H·/D· mobility ratio and qualitatively consistent with pressure and temperature effects and with the absence of abnormal mobility of NH4· and NH2′ in liquid NH3. A detailed interpretation of the dependence of abnormal conductance upon chain length in ROH gives fair quantitative agreement with experiment. The conductance minima observed in aqueous alcoholic HCl are quasi-quantitatively predicted by the theory.
The proton spends about 1% of its time undergoing tunnel transfers; the effective existence of the H3O· ion is thus confirmed.
Photolysis of Ethane at 1470 A
Authors: Wijnen M. H. J. 
Published: January 2005

The photolysis of ethane at 1470 A has been investigated in the temperature range 25° to 240°C and over a wide range of initial ethane pressures. As reaction products were found mainly H2, CH4, C3H3, and C4H10. Traces of ethylene and, not identified, higher hydrocarbons were also detected. The results indicate that the primary step in the photolysis of ethane is C2H6+hν→C2H5+H.The amounts and ratios of products, formed during the photolysis, indicate that the reaction mechanism of the photolysis is similar to that of the Hg photosensitized decomposition of ethane.
A few experiments on the photolysis of CO2 at 1470 A indicate that[open phi]CO increases with increasing temperatures.
Flame Zone Studies. II. Applicability of One-Dimensional Models to Three-Dimensional Laminar Bunsen Flame Fronts
Authors: Fristrom Robert M. 
Published: January 2005

The applicability of one-dimensional models in flame theories has been investigated experimentally in the case of a lean quarter-atmosphere propane air flame. Studies of flow patterns through the flame fronts were made using particle track techniques. From this time-position information, normal gas velocity, stream tube area, and gas density were calculated throughout the flame front. If the density is a single valued measure of the state of the gas, then one-dimensional models can be tested for Bunsen flames. Unidimensionality was verified for this and several other propane-air flames under a number of conditions. In the reaction region preceding the luminous zone it was also found that the velocity and density profiles were invariant with respect to changes in flame geometry, gas flow, and burner diameter. Therefore, it is a good approximation to speak of single reaction path for this flame, which is a function only of the initial state of the gas.
The measurements indicate that one-dimensional flame theories should be modified to include the effects of area expansion during the course of the reaction. Continuity, diffusion, and heat conduction equations should also be generalized to include the effect of expansion. It was noted that the hydrocarbon flame reaction consists of two regions: a fast propagating reaction associated with the luminous regions and the major portion of the heat release and a slow secondary reaction associated with the post luminous mantel of the flame. Flow in the primary region is a function only of the initial state of gas and independent of external influences such as gas velocity and flame geometry. Flow in the secondary region could be varied over wide limits with no measureable effect on the propagation of the flame.
Burning velocity was found to be independent of gas velocity, flame geometry, and radius of curvature of flame front, and a function only of the initial state of the gas, providing it was defined as the minimum normal gas velocity ahead of the flame front. A discussion is given of the errors introduced by measuring burning velocity by flow measurements in the throat of the burner.
Zeeman Quadrupole Spectra of p-Chloroaniline and p-Chlorobenzylchloride
Authors: Meal Harlan C. 
Published: January 2005

Analysis of the Zeeman quadrupole spectra of Cl35 in single crystals of p-chloroaniline and p-chlorobenzylchloride yields the following information: There are two sets of chlorine atoms in the p-chloroaniline crystal with differently oriented electrical field gradients. The angle between the field gradient z-axes is 79°±1°; the y-axes are parallel. Both field gradients have the same asymmetry, η=0.06±0.03. In p-chlorobenzylchloride there are four sets of chlorines (attached directly to the ring) which have differently oriented field gradients. The z-axes are parallel to the edges of a rectangular pyramid with apex angles of 8° and 67°, both ±1°. All four have the same asymmetry, η=0.07±0.02.
The bond between the chlorine and the ring is calculated to have 2.0±1.0% double bond, 79±10% single bond and 19±10% ionic character in p-chloroaniline; 2.4±0.7% double bond, 80±10% single bond and 17±10% ionic character in p-chlorobenzylchloride. The large uncertainty in the single bond and ionic characters results from the uncertainty in the hybridization of the chlorine bonding orbital.
Infrared Spectra of Gaseous and Solid Digermane
Authors: Dows David A. , Hexter R. M. 
Published: January 2005

The infrared spectra of gaseous and solid Ge2H6 have been studied in the spectral region 400—4000 cm—1. The infrared-active fundamental frequencies are as follows: A2u: 2078, 755; Eu: 2114, 898, and 407 cm—1. Assignment of combination bands gives the remaining fundamentals: A1g: 2070, 765, 229; A1u: 144; Eg: 2150, 875, and 417 cm—1. From the torsional frequency, a cosine barrier to internal rotation is 1200 cal. The structure of the perpendicular band at 898 cm—1 has been resolved, giving information connecting the Coriolis constant for this vibration with the molecular structure parameters.The spectrum of the solid, obtained at 90°K, shows only those fundamentals active in the gas phase. Small splittings or satellites are observed, and possible crystal symmetries are suggested.
On the Second Virial Coefficients for Assemblies of Nonspherical Molecules
Authors: Castle Barbara J. , Jansen Laurens , Dawson John M. 
Published: January 2005

A method of calculating the second virial coefficients for nonspherical molecules is presented which differs from the usual procedure in the following ways:
(a) The long-range directional forces between molecules are generally represented by a multipole expansion of the Coulomb interaction; this expansion is not valid for small intermolecular distances. However, these forces are usually extended into the region of small separations between molecular centers in the calculation of the second virial coefficients. The magnitude of the error introduced by this extension is investigated and found to be appreciable. The customary method is modified in such a way that the long-range orientational forces are cut off inside the molecular diameter r0.
(b) Effects resulting from anisotropy in the London forces are taken into account. It is shown that this component of the directional field is usually predominant, even for molecules with large quadrupole moments.
(c) Induction forces are considered, especially those resulting from permanent quadrupole moments. It is found that the effect of these forces is, in general, not negligible.
The results are applied to an evaluation of the second virial coefficients for carbon dioxide, nitrous oxide, nitrogen, carbon monoxide, ethane, and ethylene. A comparison is made between the effects of the long-range directional forces on the physical properties of nitrogen, carbon monoxide, and carbon dioxide in the gaseous state and in the crystal.
On the Theory of Oxidation-Reduction Reactions Involving Electron Transfer. I
Authors: Marcus R. A. 
Published: January 2005

A mechanism for electron transfer reactions is described, in which there is very little spatial overlap of the electronic orbitals of the two reacting molecules in the activated complex. Assuming such a mechanism, a quantitative theory of the rates of oxidation-reduction reactions involving electron transfer in solution is presented. The assumption of ``slight-overlap'' is shown to lead to a reaction path which involves an intermediate state X* in which the electrical polarization of the solvent does not have the usual value appropriate for the given ionic charges (i.e., it does not have an equilibrium value). Using an equation developed elsewhere for the electrostatic free energy of nonequilibrium states, the free energy of all possible intermediate states is calculated. The characteristics of the most probable state are then determined with the aid of the calculus of variations by minimizing its free energy subject to certain restraints. A simple expression for the electrostatic contribution to the free energy of formation of the intermediate state from the reactants, ΔF*, is thereby obtained in terms of known quantities, such as ionic radii, charges, and the standard free energy of reaction.
This intermediate state X* can either disappear to reform the reactants, or by an electronic jump mechanism to form a state X in which the ions are characteristic of the products. When the latter process is more probable than the former, the over-all reaction rate is shown to be simply the rate of formation of the intermediate state, namely the collision number in solution multiplied by exp(—ΔF*/kT). Evidence in favor of this is cited. In a detailed quantitative comparison, given elsewhere, with the kinetic data, no arbitrary parameters are needed to obtain reasonable agreement of calculated and experimental results.
Nuclear Magnetic Resonance : Structure of the Amino Group. II
Authors: Moulton W. G. , Kromhout R. A. 
Published: January 2005

The nuclear magnetic resonance spectra of powder samples of hydroxylamine hydrochloride and oxamide have been obtained. N–H bond distances were calculated to be 1.036±0.025 A in formamide, and 1.039±0.013 A in oxamide, assuming a 120° bond angle and a planar structure in each case. An attempt is made to correlate the N–H bond lengths with the hydrogen bond length by a modification of Lippincott's theory of the linear O≡O hydrogen bond.
The rigid lattice second moment of cyanamide was also measured. The result is not consistent with the assumption of an ammonia-like N–H bond structure, but requires a larger H–H separation.
Phosphorescence Spectra of the β-Halonaphthalenes
Authors: Sidman Jerome W. 
Published: January 2005

The 3La→1A phosphorescence spectra of the β-halonaphthalenes have been studied at 20°K in crystals and in dilute solid solutions in naphthalene and in each other. No phosphorescence was observed at 300°K or at 77°K in the pure or mixed crystals. The phosphorescence spectra at 20°K are sharp in the solid solution in naphthalene, whereas the spectra of the pure crystals or of the solid solutions in the β-halonaphthalenes are broad. The spectra are similar in energy and vibrational structure. The vibrational frequencies which appear in the spectrum can be related to those of naphthalene. From the vibrational analysis, it is concluded that the molecule possesses the same elements of symmetry in both ground and triplet states.
Quenching by impurities in the purest obtainable crystals of naphthalene made it impossible to observe the naphthalene phosphorescence.
The causes for broadening in low-temperature electronic spectra are discussed.
Space-Charge Formation in Small PbS Particles
Authors: Minden Henry T. 
Published: January 2005

A theoretical model is discussed for the effect of oxygen on the electrical properties of PbS thin films. The films are assumed to be composed of very small n-type microcrystals, on the surface of which oxygen is adsorbed. The adsorbed atoms are singly ionized by electrons from the interior of the microcrystals. The appropriate Poisson-Boltzmann equation is solved for particles of radius 5×10—8 m and 5√10×10—8 m, and for donor concentrations of 1023 m—3 and 1024 m—3. The potential distribution is given as a function of the surface acceptor concentration required for the conservation of charge.
Models for the electron and hole conductivities are given, and the results of calculations based on these models are compared with experiment. This theory is contrasted with the earlier bulk diffusion theory of the effect of oxygen. The free energy of adsorption is roughly calculated. Implications of this theory are discussed—on the general character of conduction in PbS films, on the temperature coefficient of conduction, and on the nature of photoconduction.
Nuclear Magnetic Interactions in the HF Molecule
Authors: Solomon I. , Bloembergen N. 
Published: January 2005

Magnetic relaxation times of hydrogen and fluorine in anhydrous hydrofluoric acid cannot be accounted for on the assumption of a pure dipole-dipole interaction between the hydrogen and the fluorine nuclei in the same molecule. However, the introduction, in the Hamiltonian, of a scalar term AI·S resulting from the indirect electron-coupled interaction between the two nuclei removes all the discrepancies between the calculated and observed decay times. Although the splitting due to this scalar term is smeared out by the rapid chemical exchange of the protons with the traces of water present in the acid, the nuclear Overhauser effect provides the extra parameter required to separate the dipole-dipole interaction from the scalar interaction and to calculate separately the scalar splitting and the exchange rate of the protons. The value obtained for the splitting is A/h=615 cps.
The same method has been applied to investigate the structure of the HF molecule in solutions. The experimental results can be explained qualitatively by the following picture: (a) The fluorine nuclei form long chains that move more slowly than the Larmor frequency of fluorine. (b) The chemical exchange with the relatively large quantity of water present makes the motion of the hydrogen nuclei fast with respect to the hydrogen Larmor frequency. The results are: Long relaxation times for hydrogen with T1 and T2 equal, relatively short relaxation times for fluorine resonance, with T2 shorter than T1.
Solutions of salts of hydrofluoric acid (KF) show the same character as solutions of the acid.
On the Burning Rate of Carbon Monoxide
Authors: Friedman Raymond , Cyphers Joseph A. 
Published: January 2005

Burning velocity measurements of the CO–O2–N2–H2O system were made with the flat-flame burner technique. The plan of experimentation was to vary the H2O content, the equivalence ratio, and the pressure, while holding the flame temperature constant by controlling the proportion of N2 in the mixture. The results could be represented empirically by the relation: vu2=3.8×106(CO)u(H2O)u0.5(P/Patmos)−0.24e−11 130/Tb,where vu is burning velocity (cm/sec), (CO)u and (H2O)u are mole fractions in the unburned gas, P is pressure, and Tb is burned-gas temperature. The Zeldovich, Frank-Kamenetsky, and Semenov equation was used to obtain an ``over-all'' activation energy (20 kcal) and frequency factor for the process, and the CO oxidation rate in this type of flame was then compared with the rate at which the CO forming as an intermediate in a lean hydrocarbon-air flame is oxidized in the downstream portion of such a flame. The comparison showed that, at comparable conditions, the CO oxidized 5.6 times as fast in the CO flame as in the hydrocarbon flame. Temperature traverses in hydrocarbon-air flames to which large proportions of H2O have been added showed the rate of CO oxidation to be slightly increased thereby.
Equilibrium concentrations of the species H, OH, and O in the burned gases were calculated for a variety of CO–O2–N2–H2O mixtures, all at the same flame temperature, and correlations with burning velocity were sought. The square of the burning velocity was found to be directly proportional to (OH)b(CO)b0.72; alternatively, the group (H)b(O2)b0.136 gave equally good correlation. A third successful grouping was [(H)b+0.15(OH)b]½. The writers are not convinced that correlations of this type reveal the burning mechanism.
Mass Spectrometric Study of the Kinetics of Nitrogen Afterglow
Authors: Berkowitz Joseph , Chupka William A. , Kistiakowsky G. B. 
Published: January 2005

Lewis-Rayleigh afterglow in nitrogen has been examined by simultaneous observation with a mass spectrometer and a photomultiplier. Afterglow intensity was found to be proportional to the square of the ground-state nitrogen atom concentration under a variety of conditions. The proportionality constant was essentially unaffected by small oxygen addition, but was somewhat increased with admixture of noble gases. Evidence is presented for a linear dependence of afterglow intensity on total pressure of nitrogen. Addition of nitric oxide to the afterglow results primarily in the production of nitrous oxide. From a rough calibration of the atomic concentration (ca 1%) and the afterglow radiation intensity, (1013 photons/cc-sec) a termolecular rate constant of 2×10—33 cc2-molecule—2-sec—1 is obtained.
The experimental data point to a termolecular reaction involving two 4S nitrogen atoms. The detailed mechanism probably involves the intermediate formation of the 5Σg+ molecular state, followed by a collision-induced, radiationless transition into the 3πg state.
Low-Frequency Librations and the Vibrational Spectra of Molecular Crystals
Authors: Hexter R. M. , Dows D. A. 
Published: January 2005

The effect of librations of molecules about axes perpendicular to those of the transition moments of molecular vibrations upon the dichroic ratios associated with such vibrations in the infrared spectra of molecular crystals is considered. It is demonstrated that if such librations are harmonic and of small amplitude, the root-mean-square deviation of the molecular orientation from its equilibrium orientation is sufficient to account for the deviation of observed dichroic ratios from those predicted by the ``oriented gas model.'' Deviations of this type previously reported from the polarized infrared spectra of iodoform, brucite, para-dichloro-benzene and benzene are reviewed. From a knowledge of the libration frequencies determined by examination of infrared or Raman spectra of molecular crystals, and of the observed dichroic ratios of polarized infrared spectra, the orientations of molecules and/or functional groups of molecules in crystals may be quantitatively determined. It is also demonstrated that as a consequence of the model used for correction of observed dichroic ratios, a branch-type libration-vibration spectrum of such crystals is predicted. The fine structure of this spectrum is discussed and is shown to be similar, in many ways, to the rotation-vibration spectra of polyatomic gases.
The relationship of this work to the interpretation of electron density maps of molecular crystals is discussed.