bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two-Photon Absorption in Crystalline Anthracene and Naphthalene Excited with a Xenon Flash
Authors: Weisz S. Z. , Zahlan A. B. , Gilreath J. , Jarnagin R. C. , Silver M. 
Published: January 2005

Two-photon absorption and delayed fluorescence are observed in both anthracene and naphthalene using a 5-μsec xenon flash lamp. It is shown that coherence and monochromaticity are not important in two-photon absorption. It is also demonstrated that the two-photon absorption process does not involve triplet excitons. In anthracene the two-photon rate constant δ≃8×10—29 cm sec and is about this value in naphthalene.
Mechanical imperfections play an important role in processes involving excited states in naphthalene monocrystals. The effect of imperfections is such that only an order-of-magnitude value for the intersystem crossing constant can be evaluated at the moment: τfkst≃10—1, where τf is the fluorescence lifetime.
Studies on Absorption Spectra of Ni++ Ion in NiCl2 in Different Organic Solvents
Authors: Chhonkar N. S. 
Published: January 2005

The absorption spectra of Ni++ ion in NiCl2 in six different organic solvents were studied with a Hilger Uvispek spectrophotometer from 10 000 to 3900 Å. A comparison between the calculated and observed values of oscillator strength strengthens our view that electric dipole transition coupled with vibration give rise to these bands.
From the lowering of the term separation the covalency factor is found to vary between 0.85 and 0.89 for the different solvents. The deduced g- and magnetic moment have almost the same value in all the solvents.
The cubic field coefficient in some solvents is found to be smaller than that in aqueous solution. The cluster about the Ni++ ion appears to be more anisotropic than in aqueous solution.
Structure of InSb at High Pressures
Authors: Kasper J. S. , Brandhorst H. 
Published: January 2005

It has been found by x-ray diffraction studies at high pressure (∼30 kbar) that InSb occurs in a form other than the β-Sn type which has been reported in previous studies. The new modification appears to have a simple orthorhombic structure with two atoms in the unit cell and can be derived from the β-Sn structure by a simple shear process. While this structure may be a metastable one, it cannot be ruled out that it may be more stable than the β-Sn form.
On the other hand, it is confirmed that the β-Sn structure is readily obtained by quenching to 77°K and releasing the pressure, after the transformation has occurred in the vicinity of 30 kbar.
Gaseous Diffusion in Porous Media. IV. Thermal Diffusion
Authors: Mason E. A. , Malinauskas A. P. 
Published: January 2005

The pressure dependence of thermal diffusion is derived on the basis of the ``dusty-gas'' model, in which a porous medium is considered as a collection of giant molecules (dust particles) fixed in space. The results can also be applied to capillaries by suitable substitution for geometric parameters.
Thermal separation is zero at zero pressure and constant at high pressures, but the transition can be quite complex and varied, depending upon the temperature, molecular masses, and intermolecular forces of the gas molecules involved. Representative calculations have been made to illustrate the possibility of maxima and sign reversals of the thermal separation as a function of pressure. Comparison with the scanty available experimental results reveals no discrepancies, but further experiments are desirable, particularly for cases in which unusual transition behavior is expected.
Measurements of Thermal Dissociation of Hydrogen, Using Fast Protons
Authors: Lockwood Grant J. , Helbig Herbert F. , Everhart Edgar 
Published: January 2005

Experiments involving study of the angular scattering of kiloelectron-volt protons from atomic and molecular hydrogen targets have been used to measure directly the fraction of hydrogen gas dissociated in equilibrium with hot tungsten. The state of the hydrogen gas in a tungsten furnace is determined by analyzing the scattered incident particles which result from single collisions between the incoming protons and the hydrogen gas in the furnace. In particular, the number of H— ions among the scattered particles is a measure of the molecular hydrogen density, since H— ions cannot be created in single collisions between protons and hydrogen atoms. Under the present experimental conditions it was possible to achieve a fraction dissociated of over 87.5% at a furnace temperature of 2380°K and still higher fractions at higher temperatures. These measurements are made at hydrogen pressures of the order of 10—2 Torr.
The practical conditions under which an atmosphere of highly dissociated hydrogen can be created are described and it is pointed out how the dissociation fraction and also the density of the hydrogen can be directly measured in the otherwise inaccessible interior of the gas. These measurements using a proton beam probe do not require that the pressure or temperature of the hydrogen be known and, in fact, do not require thermal equilibrium conditions.
Nonadiabatic Elastic Scattering. II. The Scattering Process.
Authors: Thorson Walter R. 
Published: January 2005

Previous studies on nonadiabatic elastic scattering of high-energy atomic beams have shown that the potentials which produce such scattering exhibit downward shifts (``Coriolis shifts'') due to high angular velocities during collisions. The elastic-scattering cross sections produced by such potentials are studied in the present work, and it is found that the scattering tends to mask the presence of Coriolis shifts, so that the apparent potential which could be deduced from measurements of such scattering differs from the adiabatic potential by only small fractions of the Coriolis shifts.
The 9-eV discrepancy between the potential for He2 at 0.5 Å, calculated in the adiabatic approximation, and the potential deduced from beam experiments cannot be accounted for in terms of Coriolis shifts.
Kinetics of the Gas-Phase Addition of HI to Butene-2
Authors: Nangia Prakash S. , Benson Sidney W. 
Published: January 2005

The kinetics of the gas-phase reaction 2HI+butene-2→n-C4H10+I2 have been studied from 292° to 333°C using a spectrophotometer to follow I2 production. Except for the first few minutes of each run d[I2]/dt is a constant for up to 25% reaction. On the basis of two coupled sets of reactions: HI+butene−25⇋6sec−C4H9Isec−C4H9I+HI→n−C4H10+I2it is shown that the reaction path 5 consists of two separate steps, one a direct molecular addition of HI and the other an I-atom-catalyzed addition.
Using estimates of the equilibrium constant K5·6 it is shown that the rate constants for molecular and I-atom-catalyzed paths are consistent with data of Ogg and Polanyi on the pyrolysis of sec-C4H9I. The Arrhenius parameters for the two addition paths are examined in terms of recent proposed theories of the transition states for four-center reactions and shown to be compatible with similar data in other systems.
Some complexities of the present system are examined involving the butene-1, butene-2 isomerizations catalyzed by I2. The pyrolysis studies on the iodides are shown to be complicated by butadiene+HI production.
Molecular Structure and Bonding of InC5H5
Authors: Shibata Shuzo , Bartell L. S. , Gavin R. M. 
Published: January 2005

The molecular structure of gaseous indium cyclopentadienyl was investigated by electron diffraction. Diffracted intensities revealed the molecule to be an ``open-faced half-sandwich'' with a symmmetry at least closely approximating C5v. The principal mean distances and vibrational amplitudes found were 2.621±0.005 Å and 0.077±0.007 Å for In–C and 1.427±0.007 Å and 0.040±0.009 Å for C–C. It was observed that the C–H bonds are pushed 4.5°±2° out of the plane of the carbon ring by the indium atom. The failure of the Born approximation significantly lowered the sensitivity of the analysis but did not prevent the deduction of reasonably good structural parameters.
Metal—carbon bonds were 0.4 Å shorter than the sum of the ionic radii but both the In–C and C–C bond lengths agreed well with calculations based on Pauling's theory of covalent bonds of fractional bond order. Moreover, metal—ring overlap integrals were found to be of substantial magnitude. Therefore it is reasonable to conclude that the binding in the complex is essentially covalent, contrary to some previously published conjectures.
Purification and Single-Crystal Growth of Potassium Cyanide
Authors: Neubert Theodore J. , Susman Sherman 
Published: January 2005

Reagent-grade KCN has been fashioned into nominally pure, low-strain, single crystals via a sequence of operations involving vacuum melting, zone refining and thermal-gradient growth of a monocrystal. Vacuum melting of KCN largely transforms oxygen-containing impurities (e.g., HCOO—, C2O4=, and CO3=) to OCN—. Zone refining removes the OCN— contamination with an effective working segregation coefficient of 0.7. Fe, Na, and Si are also readily removed. Molybdenum is a suitable container material.
Single crystals of KCN were grown under vacuum in a quartz, filtering-crystallizing device and strain minimized by freeing the crystalline boule from the ampoule walls prior to annealing slowly to room temperature. Samples cleaved from such a boule proved suitable for polarized-light experiments. They typically contained 10 ppm Na and trace quantities of OCN— impurity. A pure KCN crystal has no absorption bands in the visible or near-ultraviolet regions and begins to absorp strongly at 190 mμ. As the purity of KCN crystals decreases, the tail of the fundamental absorption shifts to lower energies. This shift is related to an increase in cyanate-ion contamination.
Crystallite Orientation in Materials Having Fiber Texture. II. A Study of Strained Samples of Crosslinked Polyethylene
Authors: Krigbaum W. R. , Roe R.-J. 
Published: January 2005

Diffraction data obtained for a crosslinked polyethylene sample crystallized at fixed strain are utilized to demonstrate the practicality of the method of analysis for samples having fiber texture which was presented in a previous paper. Plane-normal distributions qi(ζi) reconstructed using data for twelve reflections reproduce the features of the measured distributions quite satisfactorily. The series termination error is only appreciable for planes having a sharply peaked distribution, and fortunately it then appears mainly as false oscillations of small amplitude in the low-density region, which do not distort the principal features of the distribution. As a test of the accuracy of plane-normal distributions constructed for unmeasured reflections, qi(ζi) was recalculated for the (200) plane with omission of the intensity data for this plane. Deviations from the experimental distribution are again trivial. Thus, the procedure permits one to calculate the plane-normal distributions for the (002) and (401) planes, for which experimental measurements are not feasible.
The crystallite orientation distribution G(ξ, φ) is calculated using the diffraction data for twelve reflections. This may be presented as a contour map or, if plotted in stereographic projection, as the inverse pole figure diagram. The most probable crystallite orientation for this sample, having relative elongation α=4.58, inclines the a, b, and c axes from the fiber direction by 41°, 90°, and 49°, respectively. The series termination error does not displace the peak positions, but it creates small areas of negative density in the low-density region. It is demonstrated that data for four planes suffice to reveal the qualitative aspects of the crystallite distribution. The approximate relation used to estimate the standard deviation of the truncated series is tested and verified.
Diffraction data were also obtained for three additional samples covering a range of elongation α from 2.20 to 6.67. The (h0l) plane-normals orient most strongly toward the fiber axis, the (h/l) ratio of the plane exhibiting the best alignment decreasing continuously as α is increased. The implication that the b axis tends to orient perpendicular to the fiber axis is verified by the plane-normal distribution, which becomes more sharply peaked about χ=90° as α is increased. The maximum in the a-axis distribution shifts from χ=0° to larger values of χ as α is increased, while the c-axis distribution undergoes a more complex transformation.
Collisional Deactivation of Highly Vibrationally Excited Cyclopropane
Authors: Simons J. W. , Rabinovitch B. S. , Setser D. W. 
Published: January 2005

Vibrationally excited cyclopropane molecules were produced by chemical activation at ≈100 kcal mole—1 above the ground level; methylene radicals were formed by photolysis of ketene at 3200 Å and were added to ethylene. Collisional deactivation has been studied at 298° and 423°K, with ethylene as the inert deactivator, and at 298° with He, Ar, and N2 as deactivators.
The average amount of energy removed by ethylene per collision was calculated on a stepladder model and found to be in excess of 10 kcal mole—1, and not higher than 14 kcal, from the present data. Nitrogen and argon appear to have lesser efficiency than ethylene. Helium is the most inefficient gas; it removes ≈ 6 kcal mole—1 per effective collision, with some evidence that an important fraction of collisions (≈ 0.67) are elastic, i.e., result in only a little or no energy transfer. This suggests that a bimodal distribution of collisional transition probabilities, or other distribution skewed toward smaller step sizes, may be more appropriate for helium, as also found previously in works by Kohlmaier and Rabinovitch.
Partial Pressures in Equilibrium with Group IV Tellurides. III. Germanium Telluride
Authors: Brebrick Robert F. 
Published: January 2005

The partial pressures of Te2(g) and GeTe(g) over Ge–Te condensed phases between 1 and 52 at. % Te have been determined between 525° and 940°C by measuring the optical density of the vapor. Partial optical densities due to each species are calculated and converted to partial pressures by assuming Beer's law and published vapor pressures.
Over Te-saturated GeTe(c), pTe2 reaches a maximum value of 2.5±0.2 Torr between 644° and 679°C. In the same temperature interval pTe2 over Ge-saturated GeTe(c) is about 20 times smaller. At the maximum melting point of GeTe(c), 725°C, pTe2 is 0.6±0.3 Torr and pGeTe is 17 Torr. Values of pGeTe and pTe2 over GeTe-saturated Ge(c) reach maximum values of respectively 125 and 2.2 Torr near 890°C. The value of pGeTe is the same over Te- and Ge-saturated GeTe(c) and up to 725°C is given by logp (Torr)= —(10.1±0.2)103/T+8.84. The standard Gibbs free energy of formation of GeTe(c) according to Ge(g)+ ½Te2(g)=GeTe(c) is ΔG°=—(117.8±3)+41.3(10—3)T kcal/mole. The heat of fusion of GeTe(c) is 11.3±2 kcal/mole. For the dissociation of GeTe(g) into Ge(g) and Te2(g), ΔG°=(71.5±2)—(14±1)(10—3)T kcal/mole between 637° and 940°C. This leads to a value of 95±4 kcal/mole for the dissociation energy, D0°, of GeTe(g) at 0°K in close agreement with the spectroscopic value of 95±9 kcal/mole. Our previous data for the standard enthalpies of formation of PbTe(g) and SnTe(g) lead to dissociation energies of PbTe(g) and SnTe(g) at 0°K of 52.7 and 79.3 kcal/mole, respectively.
Kinetics of Capillary Condensation in Wedge-Shaped Pores
Authors: Philip J. R. 
Published: January 2005

The kinetics of capillary condensation into an initially dry pore is treated as an unsteady diffusion problem with a moving boundary at which the vapor concentration satisfies the Kelvin equation. The (justifiable) approximation that the phenomenon is radial leads to important simplifications. An exact similarity solution is found which is valid for the early stages of the condensation process. An approximate method of analysis is developed, using the class of similarity solutions of the two-dimensional radial diffusion problem with a constant concentration condition at an appropriately moving boundary. The method has some analogies to the Pohlhausen method in fluid mechanics in that the initial and boundary conditions are satisfied exactly, and the diffusion equation is satisfied in an integral sense. The method depends on numerical methods of integration, but approximate analytical solutions are available when the time is sufficiently large.
Numerical solutions are given for the capillary condensation of water. The characteristic equilibration time is highly sensitive to h0, the relative saturation of the atmosphere to which the dry pore is exposed, varying approximately as (1—h0)—3. The initial condensation rate is a constant, largely independent of h0 when this is close to one. The kinetics of capillary condensation is highly sensitive to temperature, equilibration times for water at 80°C being only 1/233 as great as at 0°C. The major influence of temperature on kinetics is due to the temperature dependence of the saturated vapor density.
A limitation to this approach is that the treatment is essentially macroscopic, although the early stages of condensation may involve relatively few molecules.
Franck—Condon Factors for the Ionization of CO, NO, and O2
Authors: Wacks Morton E. 
Published: January 2005

Calculated values of the vibrational overlap integrals for the following transitions are given: (a) CO(X 1Σ+, v′′=0)→CO+(X 2Σ+, v′=0→10); (A 2Πi, v′=0→10); (B 2Σ+, v′=0→10).(b) NO(X 2Π, v′′=0)→NO+(X 1Σ+, v′=0→10); (A 1Π, v′=0→10).(c) O2(X 3Σg−, v′′=0, 1)→O2+(X 2Πg, v′=0→10); (a 4Πu, v′=0→15); (A 2Πu, v′=0→20); (b 4Σg−, v′=0→10).
These probabilities are used to construct theoretical ionization-efficiency curves assuming an energy dependence for the electronic transition integral for both photoionization and ionization by electron impact. Previously published experimental data are discussed in terms of the theoretically calculated Franck—Condon probabilities.
Configuration-Interaction Study of the Ground State of the H3+ Molecule
Authors: Christoffersen Ralph E. 
Published: January 2005

A configuration-interaction calculation on the ground state of H3+ has been done using Slater-type orbitals of the form 1s, 2s, 2px, 2py, 2pz to form the basis set. The calculation was effected by approximating the exact wavefunction for the system by a linear combination of configurations, each of which is a properly antisymmetrized function constructed from the basis orbitals, and by applying the variation theorem to the approximate wavefunction.
The most stable nuclear geometry for H3+ is an equilateral triangle, since a plot of total energy versus central bond angle shows a deep minimum at a bond angle of 60 deg.
The best energy that was obtained for the equilateral triangle was —1.33264 hartree at R=1.6575 bohr, using 12 basis orbitals and 12 symmetry-adapted configurations. The experimental energy for H3+ is not known, but is estimated to be —1.35 hartree from these calculations.
The first excited singlet state, which is a doubly degenerate 1E′ state, has been examined at many values of R for an equilateral triangle with three basis orbitals, and has been found to give a typical repulsive energy curve.
The fundamental vibrational frequencies for the ground state have been calculated, and it has been found that the symmetric stretch frequency is 3354±60 cm—1, and the doubly degenerate bending frequency is 2790±100 cm—1.
Pulse Radiolysis Studies. IV. The Solvated Electron in the Aliphatic Alcohols
Authors: Taub Irwin A. , Harter Douglas A. , Sauer Myran C. , Dorfman Leon M. 
Published: January 2005

Some of the physical and chemical properties of the solvated electron in the aliphatic alcohols have been investigated by means of the pulse radiolysis technique.
In ethanol the optical absorption spectrum exhibits a maximum at 700 mμ. The decadic molar extinction coefficient at 5461 Å is determined to be εe—sol5461=(1.1±0.4)×104 M—1 cm—1. From this the oscillator strength of the band from 270 mμ to about 980 mμ is estimated to be f=0.7. The radiation chemical yield of the solvated electron in ethanol is found to be 1.0±0.3 per 100 eV of absorbed energy.
Absolute rate constants for a number of reactions of the solvated electron in ethanol and methanol have been determined. The diphenylide ion, formed by electron attachment to diphenyl in ethanol, shows a fast first-order decay for which the rate constant has been determined.
Mass-Spectrometric Study of the Reactions of O Atoms with NO and NO2
Authors: Klein Fritz S. , Herron John T. 
Published: January 2005

The reactions of O atoms with NO and NO2 have been studied using a mass spectrometer to directly measure the O-atom partial pressure. The results obtained are as follows: NO+O+M→NO2+M,  k1(M  is  N2)=(1.44±0.20)×1015exp (1930±100/RT) cc2 mole−2·sec−1;NO2+O→NO+O2,  k2=(1.95±0.61)×1013exp (−1060±200/RT) cc mole−1·sec−1.
These reactions are discussed in terms of the general mechanism O+XO⇌ lim BA[OXO]*+M→ lim CXO2+M→ lim DX+O2→ lim EXO2+hv.
The rates of the elementary reaction steps have been calculated from the over-all rate constants and previous results on the isotopic exchange rates of 18O with O2, NO, and NO2.
Solvent Field Corrections for Electric Dipole and Rotatory Strengths
Authors: Weigang Oscar E. 
Published: January 2005

Quantum-mechanical perturbation theory is applied to the evaluation of the electric dipole strength and the rotatory strength of a condensed system of negligibly overlapped, randomly oriented solute and solvent molecules. Besides the traditional Lorentz field corrections, a correction factor is obtained which is a function of inductive and dipolar solute—solvent interactions.
An extension of the types of intermolecular force fields heretofore considered is achieved. In particular, the effect of solvent fields due to solvent molecule static dipole moment is predicted to be a decrease in solute absorption intensity and optical activity. The complexity of terms and level of approximation cannot be expected to yield more than semiquantitative relationships, but the important solvent and solute variables are identified.
Comparison of Experimental and Theoretical Vibrational Relaxation Times for Diatomic Gases
Authors: Parker J. G. 
Published: January 2005

A comparison of theoretical and experimental vibrational relaxation times has been carried out for the halogens, nitrogen, oxygen and carbon monoxide. Reasonably good agreement is obtained for all gases except oxygen. For oxygen the predicted variation of the vibrational collision number with temperature appears to be correct; however, experimental values at high temperatures appear to be low by a factor of 0.55. Values obtained at room temperature on the other hand agree well with theory. It would seem therefore that an anomalous decrease in the vibrational collision number takes place in the temperature range from 300° to 500°K.
Since data for carbon monoxide could be fitted very well by theory, it is apparent that the effect of radiation is negligible, at least in the temperature range above 1000°K. This is consistent with the value of 0.03 sec for the radiative lifetime of carbon monoxide in the first excited vibrational state.
An empirical relationship is established between the interaction constant α and the molecular diameter σ, which reproduces the experimentally derived values quite closely.