bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative Studies of Apparent Rotational Temperatures of OH in Emission and Absorption (Spectral Lines with Doppler Contour)
Authors: Penner S. S. 
Published: January 2005

Even if a Boltzmann distribution exists for the population of molecules in various energy levels, it is not possible to obtain a satisfactory interpretation of experimental data by the use of conventional procedures unless the product of maximum spectral absorption coefficient Pmax and optical density X is sufficiently small. Detailed calculations are presented which show that the experimental results, which suggest an anomalous rotational temperature for the 2Σ state of OH in low pressure combustion flames, can be accounted for by using sufficiently large values for PmaxX (Sec. II). Whether or not experimental data should be interpreted in this manner must be determined by auxiliary studies.
Representative absorption studies for the determination of rotational temperatures in isothermal systems have been analyzed for the P1 branch, (0,0) band, 2Π→2Σ transitions of OH at 3000°K. The calculations show that erroneous interpretation of experimental results occurs if the product PmaxX is not small compared to unity. Sample calculations for a blackbody light source show that the customary procedure for treating experimental results will permit adequate correlation of the data by straight lines up to relatively large values for PmaxX. It is remarkable that the preceding statement remains true even under conditions in which emission data clearly indicate that PmaxX is no longer small compared to unity (Sec. III).
Representative calculations to determine observable peak and total intensity ratios in emission for spectral lines with Doppler contour have been carried out for 2Σ→2Π transitions, (0,0) band, P1 branch of OH at 3000°K. The calculations show that the ratios of peak and total intensities are functions of the products of maximum absorption coefficients (Pmax) and optical density (X) for the lines under study (Sec. IV).
Quantitative calculations have been carried out of apparent rotational temperatures in systems containing nonequilibrium distributions of OH at 3000°K and at 6000°K. The calculations on the P1 branch, 2Σ→2Π transitions, indicate that, in the absence of self-absorption, conventional plots showing discontinuities necessarily overestimate one and underestimate the other of the known temperatures of 3000°K and 6000°K (Sec. V).
Quantitative calculations on the nature of distortions produced when an isothermal region at 3000°K is viewed through an isothermal region at 1500°K show that the presence of a non-isothermal field of view magnifies the distortion produced by self-absorption alone (Sec. VI).
On the basis of the noncontroversial quantitative calculations described in Secs. II to VI for idealized systems, some speculations regarding the significance of reported flame temperature anomalies for OH are presented in Sec. VII.
Energy Exchange in Molecular Collisions
Authors: Widom Benjamin , Bauer S. H. 
Published: January 2005

A theory was developed for computing the probability of transition, upon molecular collision, between vibrational states, involving corresponding conversion of translational energy. A spherically symmetric Lennard-Jones 6–12 potential for interaction between the colliding molecules was introduced; their relative translational motion was described classically. Further, the theory was symmetrized to permit inclusion of collisions with nonzero impact parameters. As an example, the theory was applied to the CO2–H2O system. The effective collision diameter for an inelastic event was found to be of the observed order of magnitude, demonstrating not only the selective relaxation effect of water, but also its somewhat unusual temperature dependence.
Zener's solution of the problem for a head-on collision was generalized to three-dimensional collisions, assuming a spherically symmetric interaction potential; but the complete solution of this model, including a quantum-mechanical description of the relative translational motion, was not obtained. However, for such a potential it was possible to demonstrate that the semiclassical theory is an adequate approximation to the quantum theory result, whenever the relative translational energies are much greater than the energy of exchange.
Electronic Energy Levels of Molecular Oxygen
Authors: Meckler Alvin 
Published: January 2005

A configuration interaction study of the lower-lying electronic energy levels of molecular oxygen is made. With the 1s and 2s shells kept filled, the remaining eight electrons are distributed among the twelve spin-orbitals arising from the 2p levels on each atom. The atomic functions are represented as Gaussians, which are poor atomic functions but facile integrands in many-center integrals. The molecular orbitals are formed as symmetrical linear combinations of the atomic orbitals, simply for convenience. Inclusion of all configurations implies complete equivalence of all possible constructions of linear combinations.
Out of the 495 configurations (many-electron determinants) a group of nine states of 3Σg− character is set up and twelve of 1Σg+ character. The interaction matrix of each block is computed and diagonalized (by electronic computer). The results for the ground state, which is a triplet, are very good. The binding energy is off by 2 percent, the internuclear distance is off by 1 percent, the fundamental nuclear vibration frequency is off by 4 percent. The lowest singlet state is not given as accurately.
The energies and wave functions for the lowest triplet and singlet are calculated and compared for various values of internuclear separation. Discussion is made of the validity of single configuration theory, from both the Heitler-London and Hund-Mulliken points of view.
The Photochemical Separation of Isotopes
Authors: Billings Bruce H. , Hitchcock W. J. , Zelikoff Murray 
Published: January 2005

A method of successfully separating mercury isotopes by a photochemical process is described. The method involves the use of a monoisotopic resonance lamp as the source of light for the photochemical reaction. In this particular case a Hg198 lamp was used to excite only the Hg198 atoms. The excited Hg atoms react with water vapor to produce enriched mercuric oxide. In the first experiments an enrichment factor of 1.5 was obtained.
The analysis of the isotopes was undertaken by the use of multilayer dielectric Fabry-Perot interferometers.
On the Use of Ultrasonic Absorption for the Determination of Very Rapid Reaction Rates at Equilibrium: Application to the Liquid Phase Association of Carboxylic Acids
Authors: Freedman Eli 
Published: January 2005

An equation is derived for the excess acoustic absorption in a liquid system due to the occurrence of a chemical reaction; the method used follows in part that used by Damköhler in the case of gases. It is shown that the gross reaction rate at equilibrium can in general be found once the frequency at which the maximum excess absorption per wavelength occurs has been found, provided thermodynamic data for the reaction are known.
The application of this method to the study of the kinetics of very rapid reactions is discussed and the effects of other causes of absorption are considered.
As another application of the results obtained the acoustic absorption of acetic and propionic acids is considered. A consistent interpretation of data in the literature is given on the assumption that the excess absorption is due to the perturbation of an equilibrium between monomeric and dimeric molecules. The mole fraction equilibrium constant KN, and the heat of reaction for the dimerization are calculated. The values found for acetic acid are KN(293°K)=61.97 and ΔH=−6.21 kcal/mole; for propionic acid, KN(281.2°K)=3.040×103 and ΔH=−9.33 kcal/mole. Rate constants and activation energies for the dissociation of the dimers are also calculated.
Vibration Spectrum of a Simple Cubic Lattice
Authors: Newell Gordon F. 
Published: January 2005

Analytic expressions are derived for the frequency distribution function g(f) of a simple cubic monoatomic lattice. Only nearest and next-nearest neighbor interactions are considered, and the latter are assumed to be weak compared with the former. The procedure is based upon considering the next-nearest neighbor interactions as a perturbation, and the results are correct to the first power of a parameter τ which is essentially a measure of strength of the next-nearest neighbor forces as compared with the nearest neighbor forces.
It has been known for some time that a simple cubic lattice with only nearest neighbor interactions degenerates into the equi alent of three independent one-dimensional lattices giving a nonzero g(f) for f=0 and an infinite value at the maximum frequency. If, however, one includes even a small interaction between next-nearest neighbors, the behavior of g(f) near both ends of the spectrum changes considerably; in fact it vanishes at both ends. For intermediate frequencies, g(f) is continuous but has four analytic singularities with vertical tangents of the type predicted by van Hove for a quite general type of crystal. Although the calculated g(f) is exact only in the limit τ→0, it does properly describe the exact location and type of singularities for 0≤τ≤1/10.
The Thermal and Dielectric Properties of Crystalline Long-Chain Acetates
Authors: Meakins R. J. , Mulley Joan W. 
Published: January 2005

This investigation deals with the normal long-chain acetates with 18, 20, 24, and 28 carbon atoms. When crystallized from the melt, these compounds first give the transparent α-phase which gradually changes to the white, opaque β-phase on standing or on cooling below a certain temperature. It is found that the acetates in the α-phase all give large dielectric absorption, whereas, in the β-phase the absorption is small, or, in some cases, negligible.
Of the long-chain compounds so far investigated, the acetates in the α-phase are unique in giving two absorption regions which appear to be the result of the rotational transitions of complete molecules. The maxima for the two regions are separated by about 7 decades in frequency. Measurements of the lower frequency absorption at various temperatures show that the associated energy barrier is very large compared with previous values for compounds of similar chain-length. To explain these results it is suggested that a molecule rotating in the crystal lattice of a long-chain compound possesses four positions of equilibrium instead of two, as previously proposed.
In addition to the two absorption regions mentioned above, the long-chain acetates in the α-phase give further absorption at still higher frequencies, which is probably caused by independent orientation of the polar groups near the ends of the molecular chains.
The Effect of Pressure and Temperature on the Absorption Spectrum of Benzene in the Near Ultraviolet
Authors: Sambursky S. , Halperin A. , Henig H. 
Published: January 2005

The absorption spectrum of benzene vapor in the near ultraviolet was photographed at temperatures varying from room temperature up to above the critical temperature (287°C), and at the corresponding pressures of the saturated vapor (from a few mm of mercury up to about 50 atmos).
Changes of the intensity distribution within each of the groups of bands were found, which gave a shift in the maxima of these groups, but even at the highest temperatures and pressures near the critical point, no measurable shift in the frequencies of the components of the groups was found. This shows that the effect of intermolecular forces on the frequencies of the bands is very small.
A short discussion of the results is also given.
Molal Volumes and Compressibilities of the System NaCl–H2O above the Critical Temperature of Water
Authors: Benson Sidney W. , Copeland Charles S. , Pearson David 
Published: January 2005

From quantitative P, T, V, x data on the system NaCl–H2O in the supercritical region it has been possible to calculate apparent molal volumes, partial molal volumes, and compressibilities with accuracies of about 10 percent, 25 percent, and 15 percent, respectively.
The apparent molal and partial molal volumes of NaCl show similar, remarkable, and quite anomalous behavior. Above the critical temperature of the particular solution studied and at low NaCl compositions, the molal volumes are very large and negative, being of the order of magnitude of liters/mole. As the densities decrease, the values become more negative, pass through a minimum, and then rise again.
These minima decrease in absolute magnitude with increasing temperature, but seem to occur (for 0.2 percent solutions) at densities not very different from the critical density of water. When the partial molal volumes at constant temperature are plotted against partial densities of water, the results seem to fall on a smooth curve independent of the concentration of NaCl.
The compressibilities show a behavior which resembles that of the pure solvent and whose significance has heretofore escaped any detailed attention. They go through maxima at densities near the density at the critical temperature.
These observations can be accounted for qualitatively if it is assumed that above the critical temperature all fluids are capable of undergoing continuous, short-range condensation over a narrow range of densities near the critical density of the fluid.
The particular behavior of the NaCl–H2O systems emphasizes quantitatively the enormous effect of small amounts of solutes (capable of associating strongly with the solvent) on the behavior of the solvent near its critical temperature.
Primary Photochemical Process in Bromine
Authors: Kistiakowsky G. B. , Sternberg James C. 
Published: January 2005

A kinetic investigation of the photobromination of ethylene has led to results which are in general consistent with the earlier work of Schumacher et al. The existence of an induced oxidation reaction was demonstrated in mixtures containing traces of oxygen, which is a very strong inhibitor of the ethylene-bromine chain reaction.
The relative quantum yields of the photobromination reaction were measured at six wavelengths using narrow pass Baird interference filters. The quantum yields were shown to be independent of wavelength between the limits of 4800 and 6800A. Radiation of 7150A wavelength is absorbed but is totally ineffective photochemically. These results were interpreted with the aid of spectroscopic information to mean that the photochemically effective transitions of bromine molecules in radiation of wavelengths longer than the convergence limit, 5107A, lead to the continum of the 3π1u state, which then dissociates in one elementary act to form two normal atoms. It is unnecessary to invoke the assumption of collisional dissociation of excited bromine molecules to explain their photochemical reactivity below the convergence limit.
On the Ultraviolet Absorption Spectra of Uninegative Ions
Authors: Friedman Harold L. 
Published: January 2005

New spectral data are reported for NO2−, ClO2−, and ClO− in aqueous solution.
The theory of the electron transfer spectra of aqueous halide ions is extended to uninegative polyatomic ions by allowing for the greater excitation energy of the polyatomic radicals produced in the act of absorption, as compared with the excitation energy of the atoms produced from halide ions. This additional excitation energy arises from the operation of the Franck-Condon principle in determining the internuclear distances in the radical. Tri-iodide ion is the only one of the uninegative ions for which the required data are available and for which these data are not consistent with the assignment of the intense ultraviolet bands to transitions involving transfer of an electron to the solvent.
It is found that the low intensity absorption bands of NO2− and ClO2− coincide with the bands predicted by R. S. Mulliken for triatomic oxide molecules (AO2), with the same numbers of valence electrons.
Infrared and Raman Spectra of Fluorinated Ethanes. V. The Series CF3CF3, CF3CF2Cl, CF3CFCl2, and CF3CCl3
Authors: Nielsen J. Rud , Liang C. Y. , Smith R. M. , Smith D. C. 
Published: January 2005

The infrared spectra of CF3CF2Cl, CF3CFCl2, and CF3CCl3 vapors have been obtained in the region from 2 to 38μ, and the spectra of liquid CF3CF2Cl and CF3CFCl2 in the region from 2 to 22μ, with the aid of LiF, NaCl, KBr, and KRS−5 prisms. The Raman spectra of all three compounds in the liquid state, and of gaseous CF3CF2Cl, were studied with a three-prism glass spectrograph of linear dispersion 15A/mm at 4358A. Depolarization ratios were determined for most of the Raman bands.
All fundamental vibration frequencies except the lowest (torsional) have been assigned for each molecule, and the observed spectra have been interpreted in detail.
A Detailed Formulation of Kinetic Processes. II. The Role of Collision Processes
Authors: Benson Sidney W. , Axworthy Arthur E. 
Published: January 2005

A detailed treatment is given of the activational processes occuring in both unimolecular and bimolecular processes. Such a treatment leads very naturally to the postulate of two critically energized species, one related to the products and one to reactants. In the case of unimolecular isomerizations it is shown that the properties of either one or both of these species may dominate the rate of the nonequilibrium reaction rate expression, and the form of the rate expression is given in terms of the Slater theory of unimolecular reactions.
In the case of unimolecular decompositions, only the complex corresponding to reactants is important, whereas in the inverse case of association reactions only that for the products is of importance. Both of these types of reactions have the same form of pressure dependence in the steady-state concentration region. The above considerations apply even when the reactions are not reversible. That is, the critically energized complex related to products is still of importance in determining the reaction rate. In the case of bimolecular and higher order processes, a detailed investigation shows that the activational processes are always maintained at their equilibrium values, and there is no region in which the rate constants will show a significant dependence on concentration of inert gas.
Photoelectric Observation of the Rate of Recombination of Iodine Atoms
Authors: Marshall Royal , Davidson Norman 
Published: January 2005

The rate of the homogeneous three-body recombination of iodine atoms, I+I+M→I2+M, d[I2]/dt=k[I]2[M], is measured. A short intense pulse of light from a flash lamp dissociates 1–9 percent of the ca 1018 iodine molecules in a 200-cc cell, and the subsequent recombination of iodine atoms is followed by fast photoelectric techniques.
The measured values of k at room temperature are 4.2(±0.4)×109 liter2 moles−2 sec−1 (argon), 58(±4)×109 (neopentane), 65(±6)×109 (pentane). The value for neopentane is the same at 200°C.
The large values of the recombination rate constants indicate that an important recombining process consists of a ``sticky'' collision between an I atom and an M molecule or atom, leading to the formation of a complex IM, which reacts with a second I atom. The lifetimes of the collision complexes are estimated.
The rates of the reverse process, the dissociation of I2 by collision with M, are calculated; the pre-exponential factors are extraordinarily large.
The extinction coefficients of gaseous iodine have been remeasured.
On the Kinetics of the Disorder-Order Transformation in Cu3Au
Authors: Lord Norman W. 
Published: January 2005

The isothermal order-dependent change in the Young's modulus of a single crystal of Cu3Au is measured as a function of time at various temperatures in the range 279.3°C to 384.3°C. These temperatures were reached by quenching rapidly from an equilibrium state 28.2°C above the critical temperature (386.0°C).
The time variations of Young's modulus indicate two distinct stages of the disorder-order transformation. The initial stage starts immediately and is completed a few minutes after quenching, while the later stage requires a few minutes before starting and then proceeds very slowly toward an equilibrium state. ``Relative relaxation times'' are associated with each of them.
In conformance with the work of Sykes and Evans and others, the initial stage is described as the formation of contiguous, antiphase, ordered domains by means of normal atomic interdiffusion. The later stage consists of the coalescence of these domains and requires at least two different geometrically constrained diffusion processes.
Kinetics of Two Exchange Reactions Involving Diborane
Authors: Maybury P. Calvin , Koski W. S. 
Published: January 2005

The kinetics of the exchange between deuterium and diborane were studied over a temperature range of 25°—75°C, and it was found that the reaction was 32 order with respect to diborane and zero order with respect to deuterium at high pressures. At low pressures the zero-order dependence of the deuterium changed to first-order. The activation energy of the zero-order reaction was 20.4±2 kcal/mole. A mechanism is proposed in which the borine radical reacts with deuterium on the wall and is followed by a rate determining bimolecular collision between the partially deuterated borine radical and a diborane molecule.
The closely related exchange reaction between normal and completely deuterated diborane was also investigated. The total order of this reaction was 32, and it had an activation energy of 21.8±3 kcal/mole. A mechanism is proposed which involves the collision between a borine radical and a diborane molecule as the rate determining step.
The Limiting Thickness of an Electrolyzed Gas Film Capable of Sustaining a Given Negative Pressure
Authors: Briggs Lyman J. 
Published: January 2005

The critical thickness of a gas film that is just capable of withstanding a given negative pressure PN in a liquid column has been studied. The film was generated electrolytically on the surface of a spherical platinum electrode of known area. The number of gas molecules corresponding to the measured charge required to release the negative column was then computed from the relation between the Faraday constant and Avogadro's number. The number of gas molecules required to form a monolayer on the electrode was next computed from the molecular diameter, based on van der Waals' equation. The ratio of these numbers gives the ``thickness'' t of the film in fractions of a monolayer.
Both O2 and H2 gas films were measured under conditions such that the same number of gas molecules were deposited on the same electrode and the corresponding critical negative pressures observed. Assuming the effectiveness of the film to be proportional to the area covered, the ratio of the diameters of the O2 and H2 molecules is inversely proportional to the square root of the ratio of their critical negative pressures. This gave O2/H2=1.11 as compared with 1.06 from measurements based on van der Waals' equation.
Measurements of oxygen films were made at various negative pressures, ranging from PN=90 cm of water, t=0.55 monolayer, to PN=4 cm, t=0.87 monolayer. The results lie on a smooth curve down to PN=10 cm, t increasing steadily as PN is reduced. Below PN=10 cm, the thickness of the film no longer increases, indicating that the zone of influence of the gas molecule extends beyond its projected area.
Application of the Fermi-Thomas Model in Computing the Dipole Moment of Iodine Chloride
Authors: Glazer Herbert , Reiss Howard 
Published: January 2005

The Fermi-Thomas statistical method is applied to the molecule ICl and the nonlinear boundary value problem solved by means of the relaxation method of Southwell. In this manner it is possible to construct an electron density map for ICl and to compute its diploe moment. The computed moment compares favorably in magnitude with the measured and has the correct sense.
It appears as though the statistical method will be useful in estimating the senses of dipole moments when they are not clearly evident from experiment.