bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potential Function of NF3
Authors: Schatz Paul N. 
Published: January 2005

An approximate potential function has been determined for NF3 by using the four fundamental frequencies, the experimentally determined rotational distortion constant DJ, and physical arguments based on the absolute intensity results. Use has also been made of an argument proposed by Polo and Wilson based on a comparison of NF3 with the isoelectronic molecule CF3H.
The rotational distortion constants have been calculated as a function of the force field using the method of Kivelson and Wilson. Explicit formulas are given for the change in moment of inertia with symmetry coordinate for an XY3(C3v) type molecule.
Using the approximate potential function, values of the valence type force constants and the rotational distortion constant DK have been calculated.
Statistical Thermodynamics of Polymer Solutions. I. Theory of the Second Virial Coefficient for a Homogeneous Solute
Authors: Casassa Edward F. , Markovitz Hershel 
Published: January 2005

An approximate theory of the second virial coefficient A2 for a system of identical random flight polymer chains of n steps, of average length b, is developed on the basis of a treatment by Zimm in power series form which, though formally exact, is not rapidly enough convergent to be practically useful. By introducing, as an approximation, a spherically symmetrical distribution of the chain segments of two interacting molecules averaged relative to the locus of an initial intersegmental contact, it becomes possible to sum the series, the terms of which relate to molecular configurations with progressively greater numbers of simultaneous contacts. The result, a double integral, is evaluated numerically; but the simple relation A2=const[1−exp(1.42ψ)]/1.42ψ,in which ψ=4βn1/2(3/2πb2)3/2 and β is the mutually excluded volume for a pair of segments, differs from the integral by less than one percent for all positive values of the parameter ψ. The analytical form of this equation is justified in terms of the theory.
Virial coefficients calculated from the theory with parameters derived from intrinsic viscosity measurements agree fairly well with the observed dependence on solute molecular weight for two systems in good solvents, but the magnitudes obtained are too small. If, however, the parameters of the theory are considered arbitrary, correspondence with experiment, to within errors of measurement, can be achieved.
Rate of Recombination of Nitrogen Atoms
Authors: Harteck Paul , Reeves Robert R. , Mannella Gene 
Published: January 2005

The rate of recombination of nitrogen atoms by three-body collision has been determined at room temperature and 0.5–1.3 mm pressure. The nitrogen was dissociated (about 3–6% nitrogen atoms) in a condensed discharge and pumped continuously through a glass tube 4.2 cm i.d. and 2.5 m long. The atom concentration was measured at a given point by ``titrating'' the N atoms with NO which was introduced into the gas stream at this point which was a short distance from the discharge tube.
The N atoms react essentially instantaneously with NO in this titration, N+NO→N2+O.When excess NO is added, the unconsumed NO combines with the O atoms formed yielding the typical oxygen afterglow. If insufficient NO is added, however, the unconsumed nitrogen atoms react with the O atoms formed, yielding the typical blue color of the NO bands, N+O+M→NO*+M,When the quantity of NO added essentially equals that of the N atoms, the gas is practically colorless. This gives the N atom concentration at this point.
In order to determine the rate of recombination of the N atoms, the relative decrease in intensity of the yellow nitrogen afterglow was obtained by following the reaction along the tube by means of a photomultiplier. The intensity of the afterglow is known to be proportional to the square of the N atom concentration. With the decrease of N atoms as a function of time and with the absolute N atom concentration known at a given point, the rate coefficient could be determined.
The over-all value of the rate coefficient for the recombination reaction, N+N+M→N2+M,was determined by this experimental method to be k=1.72(±0.17)×10−32cm6/molecules2sec.
The third body was nitrogen or argon; the rate coefficient was the same for both gases within the limits of error given.
Effect of Poisons on Crystal Growth
Authors: Sears Gerald W. 
Published: January 2005

The effect of impurities is inexplicable by the accepted theory of crystal growth. In this report a mechanism is presented which describes the specific action of crystal-growth poisons.
By this model the step motion in growth is hindered and nucleation rate on an ideal surface is increased. To rationalize the effect of growth poisons it is necessary to postulate that complete monostep adsorption occurs at growth steps. In addition, the poison ion or molecule must present energetic and/or steric barriers to the addition of solute atoms so as to form an unpoisoned step by burying the adsorbed line of molecules.
Evidence for the Triplet State in Photoconductivity in Anthracene
Authors: Rosenberg Barnett 
Published: January 2005

Some evidence is presented indicating that the formation of a triplet state is involved as an intermediary step in the creation and transfer of charges in the photoconduction process in organic substances. On the basis of the simple potential curve picture, approximate solutions are obtained to the rate process equations. These equations predict that the density of the triplet states under thermal and optical equilibrium conditions will follow a Boltzmann exponential dependence upon temperature with an energy equal to a low multiple (1 or 2) of the vibrational spacing of the excited singlet state. The assumption is made that the photocurrent is proportional to the triplet state density. Measurements by the author and others of the photoconduction activation energy in a number of aromatic hydrocarbons are in very good agreement with this. The triplet state model also requires that the buildup and decay of the photocurrents be approximately monomolecular with time constants at low temperatures and intensities equivalent to the lifetime of the triplet state. The experimental results corroborate this. The model also suggests that direct absorption into the triplet state should cause photoconduction. The experimental results with anthracene are not conclusive on this point.
The model of photoconduction in organic material is predicated on a molecular rather than an extended band model approach. The major contribution to the photocurrent comes from molecules which have undergone a spin conversion while in the excited state to the triplet state of the molecule. The long lifetime of this metastable state and the assumed partial localization of the uncoupled electrons increases the probability of an intermolecular quantum tunneling of the positive hole in the ground state orbital.
Does Ultraviolet Absorption Intensity Increase in Solution?
Authors: Jacobs Lois E. , Platt John R. 
Published: January 2005

Absolute absorption intensities and oscillator strengths were determined for isoprene and cis- and trans-piperylenes in the region 1750–2400A, in vapor and in n-heptane solution, using a vacuum fluorite spectrograph. More accurate oscillator strengths are obtained if our measurements at short wave-lengths are combined with the Beckman data of Shell Development Company at longer wave-lengths.
For the three compounds the best values of the experimental Lorentz-Lorenz correction, or ratio of integrated intensities under the molar absorption curves for solution and vapor, were close to unity, a result obtained previously by Pickett and co-workers for cyclopentadiene and cyclohexadiene absorption in this same region. A value of 0.98±0.04 for this correction represents the mean of all five of these determinations. Although the values obtained from our data alone without using the Shell curves showed a much larger spread, every determination was substantially below the correction factor of 1.30 predicted by Chako's classical oscillator theory for this wave-length region and these solvents.
Low Temperature Transport Properties of Gases. II. Neon, Argon, Krypton, and Xenon
Authors: Amdur I. 
Published: January 2005

Values are computed for the viscosity, thermal conductivity, and coefficient of self-diffusion, as functions of temperature, for the following gases: neon (60°−200°K), argon (110°−290°K), krypton (150°−370°K), and xenon (210°−550°K). The method of calculation is the same as that previously developed for gaseous helium and involves the use of classical scattering theory within angular regions where diffraction effects are absent, to obtain appropriate classical transport cross sections for insertion into the exact formulas of Chapman and Enskog.
The average absolute deviations between calculated and experimental values are 5.5 percent for viscosity and 5.9 percent for thermal conductivity. In the case of self-diffusion, only two experimental values are available for comparison with calculated values, one each for krypton and xenon. The absolute deviations are 9.7 and 10.3 percent, respectively.
A procedure is suggested for obtaining approximate values of the mutual diffusion coefficient of a binary gas mixture from the self-diffusion coefficients of the constituents.
On the Nature of the Interaction between Starch and Iodine
Authors: Stein R. S. , Rundle R. E. 
Published: January 2005

(1) It is postulated that the interaction between starch and iodine in the amylose-iodine complex is of dipolar nature.
(2) A model for such dipolar interaction is proposed and the necessity for a cooperative effect is discussed.
(3) The interaction energy is calculated as a function of a parameter x and it is shown that this parameter possesses a critical value at which a ``condensation'' of iodine into the complex occurs.
(4) It is demonstrated that it is physically reasonable for this parameter to attain its critical value.
(5) It is shown that additional stabilization may occur as a result of the formation of a resonating ``polyiodine'' chain at high dipolar interaction having a I–I distance and heat of formation which compares favorably with experiment.
(6) Application of the theory is made in discussing the stability of the polyvinyl alcohol-iodine complex.
(7) The color of these complexes is discussed in terms of the theory.
Thermodynamics of the System Benzene-Biphenyl
Authors: Tompa H. 
Published: January 2005

The vapor pressure of benzene and the heat of dilution of benzene-biphenyl mixtures have been measured at 25°C. The results are shown to be in fair agreement with Guggenheim's formulae based on the lattice model, assuming that the biphenyl molecule occupies twice the volume of the benzene molecule, and that the coordation number of the lattice is between 6 and 12. No agreement can be obtained if the effect of the different sizes is neglected.
The experimental results of other authors are critically examined and shown to conform to the above picture.
The Surface Tension of Liquid Metals
Authors: Skapski Adam S. 
Published: January 2005

The author is opposed to the generally established opinion that the surface tension of liquid metals is abnormally high (as compared with that of non-metallic liquids) and that the metallic character (the presence of free electrons) is the main cause of the ``high'' surface tension of metals. He shows that this opinion is due to the fact that specific surface tensions (ergs per cm2) are compared and that the influence of temperature is not accounted for. Total surface energies σM—T(dσM/dT)—where σM=σspec×A is the surface tension referred to the surface A occupied (in monomolecular layer) by N-Avogadro's molecules—are of the same order of magnitude.
The author expresses the opinion that the main cause of the surface tension of all liquids, whether metallic or not, is the same, viz., the total surface energy is determined by the amount of energy required to bring the molecules or atoms (and electrons) from the bulk of the liquid to its free surface while enlarging the surface area. He shows that in organic liquids showing no dipoles this energy can be calculated directly from the heat of vaporization at absolute zero and from the configuration of nearest neighbors. In the case of metals, the change of kinetic energy of electrons must be considered in addition. The author shows that the latter must contribute a negative term to the total surface energy. In fact, liquid metals show lower surface energies than might be expected from their heats of vaporization and from the configuration of their nearest neighbors (Fig. 1).
A short review of the recent electron theories of the surface tension of liquid metals is given.
The Vapor Pressure and Heat of Sublimation of Graphite
Authors: Brewer Leo , Gilles Paul W. , Jenkins Francis A. 
Published: January 2005

The heat of sublimation of graphite and the heats of dissociation of CO and C2, which have been the subject of much controversy in recent years, have been unambiguously established by the direct determination of the total vapor pressure of graphite by an equilibrium effusion method and by the determination of the partial pressure of C2(gas) in equilibrium with graphite.
The heat of sublimation of graphite to C(g) is found to be ΔH0=170.39±0.20 kilocalories per mole at 0°K. The heat of sublimation of graphite to C2(g) is found to be ΔH0=233.1±7 kilocalories per mole. The heats of dissociation of C2 and CO have been shown to be 4.7±0.3 and 11.109±0.01 electron volts, respectively. The accommodation coefficient of carbon gas on graphite at high temperatures is found to be about 0.3 and vaporized carbon gas is shown to be in the 3P ground electronic state.
On the Photo-Chemistry of Some Ions in Solution
Authors: Farkas L. , Klein F. S. 
Published: January 2005

The absorption spectra of chlorate, bromate, iodate, and hypobromite ions and of hypobromous acid were measured.
The decomposition of bromate ion was investigated in the light of a mercury arc in the spectral region: 1900A to 2600A. The quantum yield of the decomposition is 0.19. The main decomposition reaction leads to the formation of hypobromite and molecular oxygen. The irradiation of hypobromite ions leads to the formation of bromide and bromate ions in a ratio of about 4 to 1 and to the evolution of oxygen. The decomposition of chlorate ion and iodate ion is analogous to that of bromate. It is assumed that in all these cases the primary process of light absorption consists of the transfer of an electron to the hydration layer. In the case of halate ions, the photo-chemical reaction can be formulated as a decomposition of the complex (XO3−·H2O) to XO−+H2O+O2; in the case of the hypobromite, as the decomposition of (XO−·H2O) to X−+H2O+O. In the latter case the oxygen atoms formed are responsible for the formation of bromate.
Countercurrent Gaseous Exchange Method for the Separation of Isotopes
Authors: Bernstein R. B. , Taylor T. I. 
Published: January 2005

A method is described for isotope enrichment by countercurrent gaseous exchange in a thermal diffusion column. The theory is derived for two cases of interest: diffusion limited and reaction-rate limited. Solutions of the equations are presented for the over-all separation S at the steady state as a function of the following: single stage enrichment factor α; diffusion constant D or exchange rate constant k; length of column Z; and the convective flow L, which in turn depends on pressure, temperature, column dimensions, etc. The results may be expressed in the usual form S=αN. For the diffusion-limited case N=4πDc̄Z/L, where c̄=moles of gas per cc. For the reaction-rate limited case the number of theoretical plates per unit length is given by the expression N/Z=k/v, where v is the convective velocity.
Experiments are described in which C13 was concentrated by the exchange reaction C12O2+C13O⇌C13O2+C12O. The observed dependence of the over-all separation upon the operational variables is consistent with the theory.
Growth of Potassium Chloride Crystals from Aqueous Solutions. II. Growth in a Gamma-Radiation Field
Authors: Botsaris G. D. , Mason E. A. , Reid R. C. 
Published: January 2005

Seed KCl crystals were grown from aqueous solution under conditions of constant temperature, supersaturation, and impurity Pb+ + level. Experiments were carried out both in-and-outside a gamma-irradiation field. The dislocation densities and absolute-growth rates of the (100) faces of the KCl crystals were measured.
With solutions containing about 10−7 moles PbCl2/mole KCl, irradiation had no measurable effect on dislocation density. At lower lead concentrations, irradiation reduced the number of dislocations and a dislocation climb process is suggested to explain the results.
The effect of irradiation on growth rates of KCl was insignificant when the Pb+ + concentrations were 10−8 and 10−6 moles/mole of KCl. At intermediate concentrations (around 10−7 moles Pb+ +/mole KCl), the effect of irradiation was such as to decrease the growth rate. A possible mechanism is suggested to explain these somewhat anomalous results.
Infrared-Emission Studies of Electronic-to-Vibrational Energy Transfer. III. Hg* + NO
Authors: Karl G. , Kruus P. , Polanyi J. C. , Smith I. W. M. 
Published: January 2005

Electronic-to-vibrational transfer has been observed in the system Hg*(63P1,0)+NO. Both Hg*(63P1) and Hg*(63P0) have been found to be effective in bringing this about. A set of rate constants, kv (or cross sections σv2) for electronic-to-vibrational transfer were derived according to various models from an observed set of steady-state concentrations, Nv. The set of kv bear a qualitative resemblance to those for Hg*+CO (Part II). Hg*+NO exhibits a significant but slowly diminishing probability for vibrational excitation into vibrational levels up to v=16 or 17, and an insignificant probability for vibrational excitation into higher levels than v=16–17, corresponding to ⅔ of the electronic energy converted into vibration. The qualitative similarity of these results to those obtained for Hg*+CO suggests that a similar mechanism may be applicable here: Hg*+NO→HgNO*→HgNO→Hg+NO†. However, there exists in the present system an alternative mechanism which would involve electronic-to-electronic transfer: Hg*+NO(X 2Π)→Hg+NO*(4Π), followed by formation of NO† in the ground X 2Π state by collisional deactivation of NO*(4Π).
The total cross section for electronic-to-vibrational transfer with Hg*(63P1) as the donor was estimated to be (σvib2)1=1–15 Å2, and that with Hg*0 as donor (σvib2)0=0.05–1.0 Å2.
Adsorption of Barium on Tungsten: Measurements on Individual Crystal Planes
Authors: Schmidt L. D. 
Published: January 2005

The adsorption of barium on the (110), (211), (100), (111), and (221) planes of a tungsten field emitter was studied for both thermally equilibrated and unequilibrated adsorbate layers. At low coverage the equilibrated atom densities on the (110) and (221) planes are ∼100 times greater than on the (211) and (100) planes, while for θ̄&gt;0.2 equilibrated atom densities are essentially identical on all planes. Dipole moments are roughly the same on all planes, corresponding to q∼1.0 electron/atom. At high coverages (θ∼0.8) there is evidence for rearrangement on heating to produce pronounced work function minima on the close-packed crystal planes.
These results are interpreted in terms of the previously suggested model of electropositive adsorption, with generally good agreement obtained. The influence of the small size of the substrate on the measurements is considered, and it is shown that these results should be identical to those on perfect macroscopic surfaces in most situations.
Molecular One-Center Two-Electron Integrals Containing a Function of the Interelectronic Distance
Authors: Grein Friedrich , Hawton Margaret H. 
Published: January 2005

Two-electron integrals are solved for arbitrary one-center functions of r1, r2, and r12, combined with spherical harmonics of the angular coordinates.
All matrix elements are derived in detail for a configuration-interaction wavefunction, multiplied by the correlation factor 1+ar12, with complex a. Closed-form expressions of the matrix elements are given for a Shull—Löwdin basis set with a single scaling parameter.
Applications to ground state and lowest excited 1A1′ state of H3+, with equilateral-triangular structure show that the improvement in energy due to the correlation factor is from 0.01 to 0.03 a.u.
Acetylene—Oxygen Reaction in Shock Waves. Origin of CO2
Authors: Homer J. B. , Kistiakowsky G. B. 
Published: January 2005

The ir emissions from CO and CO2, formed in the C2H2–O2 reaction in a shock tube, have been observed as a function of time. By calibrating these emissions in terms of concentrations and by comparing them with the emission of CH* (A 2Δ→X 2π), produced in the same reaction, it has been possible to confirm that CO2 is formed in the early stages by a reaction other than CO+OH→CO2+H. This reaction involves a primary carbon-containing radical and an O2 molecule, and its rate at 1800°K is 5% of the rate of formation of CO, produced by a similar reaction.
The importance of the reaction CO+OH→CO2+H in the later stages of oxidation has been examined as a function of the initial O2/C2H2 ratio, and the growth of OH concentration during the reaction elucidated.
More decisive proof is given that CH* is produced by a reaction which is second order in reaction intermediates.
Electronic Excited States of Benzene and Ethylene
Authors: Clark P. A. , Ragle J. L. 
Published: January 2005

Energies of low-lying excited electronic states of benzene have been calculated using the semiempirical SCF scheme of Pople, Santry, and Segal. Semiquantitatively transferable parameters are chosen by fitting the theory to the ionization potential and the position of the 3B1u state. The principal requisite modification of parameters concerns a reduction in scale of resonance integrals from those suggested by Pople et al.; subsidiary small adjustments are required in diagonal core parameters.
The theory predicts several interesting features which are at variance with the usual interpretation of the near-ultraviolet spectrum but which are not in irrevocable conflict with experiment. When these are taken into account, positions of other states, calculated without scaling of atomic-orbital Coulomb repulsion integrals, are in good agreement with experiment.
Representative results are also presented for ethylene.
Chlorine and Deuteron Relaxation Time Measurements in Liquid HCl and DCl
Authors: Boehme H. , Eisner M. 
Published: January 2005

Measurements of chlorine T2 in liquid HCl and DCl have been made over the temperature range of −40° to 60°C. Estimates of the reorientational correlation time made possible by the chlorine measurements were used to evaluate the proton intramolecular dipole contribution which was subtracted from the total intramolecular contribution to obtain the proton spin—rotational contribution. The magnitude of the spin—rotational contribution thus obtained compares with that estimated by Krynicki and Powles.
Deuteron T1 times in liquid DCl were measured over the temperature range of −75° to 25°C and found to differ considerably both in magnitude and temperature dependence from deuteron T2 times. Estimates of the quadrupole contribution to the deuteron (1/T1) and, thus, a value of 2.0×1017 V/cm2 for the electric-field gradient at the deuteron site in DCl were made by use of the reorientational correlation time from chlorine measurements.