bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Adsorption Characteristics of Clean Surfaces of Germanium and Silicon
Authors: Schlier R. E. , Farnsworth H. E. 
Published: January 2005

Diffraction patterns obtained from atomically clean germanium surfaces contained half-integral order beams in (110) azimuths for both (100) and (110) surfaces and in all azimuths for the (111) surface. These results are considered to be due to displacements of surface atoms from their normal bulk lattice positions in the surface plane. Adsorption of oxygen on all of these surfaces extinguished all of the diffraction beams which were not integral order.
In addition to the normal surface lattice spacings of clean (111) and (100) surfaces of silicon, there were surface structures with larger spacings, most of which depended on the conditions of ion bombardment and/or subsequent heat treatment. Two such structures have been observed for the (100) surface of silicon; one is a double-spaced lattice in the (110) azimuth, similar to that for germanium, and the other has a spacing about 8% greater than that of normal silicon and was obtained only after radiation quenching of the crystal from 1000°C. Two large-spaced structures were observed for the (111) surface. All of these structures were extinguished by exposure to oxygen. Evidence is presented which indicates that these structures were not due to contamination but to the silicon itself.
The method of determining the kinetics of gas adsorption from the low-energy electron diffraction beams is outlined and the calculations of the fractional coverage and sticking probability are presented for oxygen. For silicon crystals, the calculations of surface coverages and sticking coefficients for oxygen were found to depend on the preceding treatments of the crystals. The rate of adsorption of oxygen was proportional to the pressure, at least for pressures below 10-6 mm Hg, and depended on the preceding treatments of the crystals. After oxygen adsorption, the clean germanium surface could be regenerated by heating at 500°C for 30 min and for silicon it was regenerated by heating at 900°C for a few minutes. A comparison with results of other observers is given.
Structure of K2CuF4. New Kind of Distortion for Octahedral Copper(II)
Authors: Knox Kerro 
Published: January 2005

Potassium tetrafluorocuprate(II) has been shown by single-crystal x-ray data to be isostructural with K2NiF4. The tetragonal unit cell, with a=4.155±0.005 and c=12.74±0.01 A, contains two formula units. The ions are in the following positions of space group D4h(17)−I4/mmm:2Cu in (a),4FI in (c),4K and 4FII in (e) with zK=0.356 and zFII=0.153. In this structure the Cu(II) ions are surrounded by a distorted octahedron of F— ions with two nearest neighbors at 1.95 A and 4 next nearest at 2.08.
This is the first time that copper(II) in essentially octahedral coordination has been proved to have a tetragonal distortion such that c/a for the distorted octahedron is less than one. This experiental result is contrary to the theoretical calculations of Öpik and Pryce but in accord with the refined computations of Liehr and Ballhausen.
Vibrational Spectrum of 4,4-Dimethylcyclopentene
Authors: Lauer James L. , Jones William H. , Beachell Harold C. 
Published: January 2005

The vibrational analysis of 4,4-dimethylcyclopentene has been carried out by a normal coordinate calculation based on the Wilson FG matrix method. Assignments of the infrared and Raman bands were made with the help of the calculated fundamentals. The model used in the calculation was assumed to be planar and to possess C2v symmetry. The good agreement between calculated and observed frequencies justified this assumption.
A matrix iteration program was used on an IBM—650 digital calculator to find the roots of the secular determinant. It worked very well considering the large number of modes caused by the low symmetry of the molecule.
Vibrational Spectrum of Cyanate Ion in Various Alkali Halide Lattices
Authors: Maki Arthur , Decius J. C. 
Published: January 2005

The infrared absorption spectra of dilute solid solutions of cyanate ion in KI, KBr, KCl, and NaCl single crystals have been examined between 600 and 5000 cm—1 at temperatures ranging from 150 to 480°K. Over fifty distinct maxima have been observed and assigned (including numerous isotopic, combination, and hot bands) in the most concentrated sample, for which KBr was the solvent. A strong Fermi resonance between 2ω2 and ω1 occurs. The vibrational energy has been expressed in terms of the eleven fundamental frequency and anharmonicity constants appropriate to a linear, unsymmetric triatomic molecule. Force constants in the KI solvent lattice are fNC=15.51, fCO=11.03, f′=1.35, and (fα/l1l2)=0.506 mdyne/A, a result which shows very clearly that the NC bond is of higher order than the CO bond in the cyanate ion, and that the latter bond is notably weaker in cyanate ion than in CO2, where its force constant is 16.0.
In general, the fundamental frequencies increase as the lattice constant decreases. Fairly detailed calculations show that although the induction energy term arising from the dipoles induced in the solvent by the vibrating cyanate ion is not negligible, the observed variation of frequency cannot be explained by the induction term alone and must involve the short-range, repulsive forces.
Electron Impact Study of Nitric Oxide Using a Modified Retarding Potential Difference Method
Authors: Cloutier G. G. , Schiff H. I. 
Published: January 2005

An electron impact study of NO was made using the retarding potential difference method for producing the effect of a monoenergetic electron beam. In this modification of the method the electron retarding potential is provided by the potential minimum which exists between the anode and cathode of a space-charge limited diode.
The ionization potential of NO was found to be 9.25±0.02 ev and the ionization efficiency curve for NO+ to be nonlinear near the onset. This curvature can be attributed to the difference in the equilibrium internuclear distances of NO and NO+. Appearance potentials were obtained for the formation of N+, O+, and O- ions from a number of processes. With the exception of O- ions formed by electron capture, it was not necessary to postulate that any of the ions are formed with excess kinetic energy. The appearance potentials of all the processes are consistent, within experimental error, with a value of 6.50 ev for the dissociation energy of NO. The shape of the resonance capture curve for O- formation was used to construct part of the potential energy diagram for the NO- ion.
Energy Transfer in Molecular Complexes. II. The Anthracene-sym-Trinitrobenzene Complex
Authors: McGlynn S. P. , Boggus J. D. , Elder E. 
Published: January 2005

The emission spectrum of the anthracene-sym-trinitrobenzene complex has been investigated in a solid solution in a diethylether-isopentane (EP) glass at 77°K. The observed luminescence consists of two distinct electronic transitions: one transition is the reverse of the charge-transfer E←N absorption of the complex; the other transition is a phosphorescence very similar to the T→S emission of anthracene in EP, but blurred somewhat in vibrational structure, blue shifted by 113 cm—1, decreased in lifetime by a factor of about 2 and showing decreases in the ground state vibrational frequencies of a few percent. These results, as opposed to previous conclusions (vide infra), would suggest that the phosphorescence is truly a T→S process of the complex which is largely localized on the anthracene component.
Vibrational analyses of T→S spectra of anthracene in EPA and in EP and of the T→S and E→N spectra of the complex in EP at 77°K are given.
Ion-Molecule Charge Transfer Reactions in the Alpha Radiolysis of Various Hydrocarbons in a Mass Spectrometer
Authors: Rudolph P. S. , Melton C. E. 
Published: January 2005

The new alpha-particle mass spectrometer proves to be a powerful tool for the study of charge transfer between gaseous ions and molecules. Energetically possible charge-transfer reactions have been differentiated into probable and improbable reactions by employing binary mixtures of hydrocarbon gases in this instrument.
The alpha-particle induced charge-transfer reaction, C2H2++C6H6→C2H2+C6H6+, is shown to be very efficient. In contrast, the charge-transfer reaction, C2H2++C2H4→C2H2+C2H4+, is shown to be inefficient. This inefficiency is discussed in terms of the competing chemical reaction, C2H2++C2H4→C3H3+ +CH3.
Unperturbed Chain Dimensions of Polymeric Chains
Authors: Hoeve C. A. J. 
Published: January 2005

Methods are given for the calculation of polymer chain dimensions unperturbed by excluded volume effects but dependent on restricted rotation around the chain bonds as a result of interactions between substituents on neighboring chain atoms. The matrix methods used by most previous investigators are valid only for cases where the rotations, or pairs of neighboring rotations, are noninteracting. The methods recently developed by Lifson to account for interactions between any two consecutive rotations in chains of the type (CR2)i are extended to chains of the type (CH2–CR2)i and isotactic chains of the type (CH2–CHR)i.
As an illustration the chain dimensions of polyisobutylene are calculated by using parameters from x-ray data in the crystalline state and results from stress-temperature measurements on amorphous networks. Reasonable agreement is obtained with experimental data on dilute solutions of polyisobutylene.
Infrared Dispersion Measurements and Integrated Absorption Coefficients for Pure Liquid Benzene
Authors: Schatz Paul N. 
Published: January 2005

The refractive index of pure liquid benzene has been measured in the 2-to 21-μ region to an accuracy of about ±0.003 using an interferometric technique developed by Kagarise and Mayfield. A general relation is derived between the refractive index and integrated absorption coefficients of a pure liquid. The relation is used to determine the absolute intensities of the fundamental vibrations of pure liquid benzene from the dispersion data. A comparison is made with the same intensities determined in the direct absorption measurements of Hisatsune and Jayadevappa. The dispersion values appear to be higher than the absorption results, the difference being about 40% for the 14.8 μ fundamental where the most accurate comparison is possible. A comparison between pure liquid and gas intensities is also made.
A brief discussion is given of the advantages and limitations of the dispersion method in determining integrated intensities in liquids.
Effect of Pressure on the Spectra of Color Centers
Authors: Eppler R. A. , Drickamer H. G. 
Published: January 2005

The effect of pressure on the spectra of certain color centers produced in the alkali halides by x irradiation has been measured to pressures as high as 166 000 atm.
For the F center a shift to higher energies with increasing pressure is observed. The slope of the shift versus density is at least twice the value that would be predicted from Ivey's relation at low pressure, and decreases with increasing pressure. This indicates that the compressibility in the neighborhood of the F center is greater than in the bulk crystal, particularly at low pressure.
For the M center in LiCl a shift to higher energy with increasing pressure is observed, about one-fifth as great as the shift observed for the F center.
Approximate Analytical Wave Functions for the 1sns 1S States of He and He-Like Ions
Authors: Ritter Z. , Pauncz R. 
Published: January 2005

Calculations have been made for the 1s2s, 1s3s, and 1s4s 1S states of He and He-like ions, assuming wave functions of the symmetrized product form, u(1) v(2)+u(2) v(1). The results are the best obtained till now using such a functional form, and are even better than some recent calculations which, in addition, use angular correlations.
The energy values obtained for He are: 2.14307, 2.06036, and 2.03320 for the 1s2s, 1s3s, and 1s4s 1S states, respectively. The wave functions obtained were checked by other criteria besides the energy criterion.
Nonstoichiometry and Ferroelectric Properties of PbNb2O6-Type Compounds
Authors: Subbarao E. C. , Shirane G. 
Published: January 2005

The crystal structure of PbNb2O6 consists of a framework of NbO6 octahedra linked through corners. The Pb2+ ions occupy 5 out of the 6 available interstitial sites in this framework. Single-phase compositions have been prepared by solid-state reactions to yield nonstoichiometric compounds of the form A1+xB2O6 where A and B may consist of two ions of different valency and x has values between —0.08 and 0.15. In these materials, the number of unfilled interstitial sites inherently present in PbNb2O6 lattice has been varied. Lattice parameter and x-ray intensity data confirm that the additional ions introduced occupy the same sites as Pb2+ ions.
The ferroelectric Curie temperature has been studied as a function of the composition of these dielectric solids. For compositions with x&gt;0, the Curie temperature is not very sensitive to composition. As the number of unfilled interstitial sites increases (x&lt;0), the Curie temperature decreases sharply.
Quantum Mechanical (Phase Shift) Analysis of Differential Elastic Scattering of Molecular Beams
Authors: Bernstein Richard B. 
Published: January 2005

For a spherically symmetrical intermolecular potential V(r)=εf(r/σ) the quantum calculation of the elastic scattering cross section dσ(Θ)/dΩ in the c.m. system is carried out as follows. For a given relative velocity (or deBroglie wavelength) and an assumed V(r), the radial wave equation is integrated for successive values of the angular momentum quantum number l, yielding the phase shifts ηι. Then dσ(Θ)dΩ is computed in terms of the series of ηι's in the standard way. A general computational program (following that of K. Smith) is outlined for the evaluation of the radial wave function and the phase shifts, utilizing an IBM 704 computer. Calculations are presented for the L-J (12, 6) potential function. The results may be concisely represented using the framework provided by the semiclassical treatment of Ford and Wheeler, i.e., in terms of a set of reduced phase constants vs reduced angular momenta at various reduced relative kinetic energies K. Tables and graphs are presented from which the phases may be obtained, to a good approximation, for any given ε, σ and K. Computation of the differential and total cross sections from the phase shifts is then readily accomplished.
The results are compared with the classical and semiclassical treatments. The problem of tunneling and orbiting is discussed.
Theory of Dilute High Polymer Solutions. II
Authors: Krigbaum W. R. , Carpenter D. K. , Kaneko M. , Roig A. 
Published: January 2005

The second virial coefficient is calculated according to the smoothed distribution method. Our treatment differs from those of Flory-Krigbaum and Isihara-Koyama through inclusion of the numerous short-range intramolecular contacts arising by virtue of the connected nature of the chain. The result is to replace the previous F(X) by F(X, ρ), where the parameter ρ depends upon the ratio of the total number of intramolecular contacts to the number of long-range contacts counted using a radial segment distribution. The number of intermolecular contacts created when two molecules overlap is estimated by the use of an additional smoothed radial segment distribution which is assumed to be uniformly expanded by intramolecular excluded volume effects.
Comparison with experiment reveals that both the temperature and molecular weight dependences of A2 in the vicinity of the theta temperature are described in a reasonably quantitative fashion by the present treatment. In this case there are no adjustable parameters. Furthermore, satisfactory agreement is observed for good solvents using values for the thermodynamic interaction parameter deduced from intrinsic viscosity. In the limit ρ=1 the present treatment yields a result equivalent to those of FK and IK. We conclude that the latter underestimate the number of intramolecular contacts through neglect of the connected nature of the chain. In the other limit, ρ=0, a result approximating that of the Casassa-Markovitz treatment is obtained. We believe that their assumption of a spherical segment distribution about the initial point of contact results in an over-estimation of the number of intermolecular contacts.
Polycrystalline Resonance Line Shape of π-Electron Radicals
Authors: Sternlicht Himan 
Published: January 2005

A general expression in the form of a multiple integral involving a delta function is derived for the polycrystalline spectra of radicals. The expression is exact when the hyperfine structure is due to the interaction of one proton with the unpaired electron. The extension to a system involving the interaction of a number of protons with the unpaired electron is straightforward but was not done here.
Because of the formidable integrations encountered when the complete spin Hamiltonian is used, a simpler case is considered to illustrate the technique developed. It is shown that if one assumes that IH, the nuclear spin component along the externally applied magnetic field, is a good quantum number, then the peak to peak separation of the broad doublet that is obtained bears a simple relationship to the hyperfine interaction.
For a properly chosen Cartesian axis system, the hyperfine spin Hamiltonian can be written as Hhf=hA SzIz+hBSxIx+hCSyIy.The peak to peak separation corresponds to the middle value of | A |, | B |, | C |.
The line shape for a C–H fragment with the unpaired electron in a carbon 2px orbital is worked out in detail assuming that IH is a good quantum number. Two peaks with very slightly asymmetric shoulders are obtained, the peak to peak separation being 61 Mc.
Microwave Spectrum, Barrier to Internal Rotation, and Quadrupole Coupling of Acetyl Bromide
Authors: Krisher Lawrence C. 
Published: January 2005

The microwave spectra of the two acetyl bromide species, CH3COBr79 and CH3COBr81, have been investigated in the region 12 000 to 33 000 Mc.
The bromine nuclear quadrupole hyperfine splittings were analyzed to give values for the quadrupole coupling constants. The observed coupling constants indicate a considerable deviation from cylindrical symmetry of the electric field gradient about the C–Br bond.
Several of the rotational transitions were further split into doublets due to the hindered internal rotation of the methyl group. The quadrupole hyperfine and internal rotation splittings were found to be essentially independent, and analysis of the latter gives a barrier to internal rotation of 1305±30 cal/mole.
Emission Spectrum of Trivalent Holmium in the Scheelite Structure
Authors: Van Uitert L. G. , Soden R. R. 
Published: January 2005

Fluorescent emission due to holmium can be readily observed in a calcium tungstate host lattice under 3660 A excitation. There are at least eight excited states of holmium which fluoresce in the visible range due to transitions to the 5I8 ground state. These emission peaks show concentration quenching effects which appear to be due to the development of exchange coupling.
A number of emission peaks due to holmium represent transitions which do not correspond to known absorption bands. These peaks are particularly prominent in the emission spectra at high concentrations of holmium.
NMR Spectra of Glycidaldehyde
Authors: Reilly C. A. , Swalen J. D. 
Published: January 2005

The NMR spectra of glycidaldehyde were measured at 40 and 60 Mc/sec. [Complex chemical formula] These complicated spectra of four interacting protons were analyzed by two methods: the ABKY approximation and the iterated ABCD solution. The various mathematical techniques developed should prove useful in the analyses of other complicated spin resonance spectra.
The following spin-spin coupling constants, Jij in cycles per second and chemical shifts, δi in parts per million (relative to tetramethylsilane) were found: JABJACJBCJADJBDJCDδAδBδCδD40 Mc/sec5.542.044.90−0.03−0.326.363.0963.1583.3568.92260 Mc/sec5.542.094.87+0.03−0.316.243.0983.1663.3568.922 The first three coupling constants are very close in magnitude to those obtained in other epoxides (in most cases to within 0.5 cps).
The magnitude of the coupling constant between the aldehyde proton (D) and the adjacent proton (C) indicates that the D proton of the aldehyde group is probably on a time average, mainly in a plane perpendicular to the epoxide ring. The proton (D) could be either cis or trans to proton (C), but from a consideration of internal rotation interactions, it is probably in the trans configuration. The JAC and JBC coupling constants are consistent with an ``eclipsed-ethanelike'' model rather than with an ``ethylenelike'' one. The coupling constants across the molecule, JAD and JBD, are an order of magnitude smaller than the other constants. This is in agreement with the approximate attenuation factor of 1/10 for spin-spin coupling through a single bond.
Gaseous Detonations. XV. Expansion Waves in Gaseous Detonations
Authors: Miyama Hajime , Kydd Paul 
Published: January 2005

The ultraviolet absorption spectrum of OH and the visible light emission profile in the rarefaction wave following a detonation in C2H2+H2+2O2 have been measured. Analysis of the absorption spectrum at an initial pressure of 60 mm Hg gives an average rotational temperature of 3164°K during the first 310 μsec. after the detonation wave front. The gas temperature calculated by using detonation theory and necessary thermodynamic data is 392°K higher than the experimental rotational temperature. The difference is very close to the difference of 350°K which has been predicted by T. C. James theoretically.
The emission profiles demonstrated the presence of double waves at initial pressures higher than 90 mm and the appearance of these waves coincides with an increase in detonation velocity to that calculated using a ``frozen'' sound velocity.
In expansion waves produced by bursting a thin diaphragm with the detonation wave, the emission intensity was found to be far higher than predicted and the velocity of the expanding gas and the shock wave ahead of it to be somewhat lower than expected.
NMR Spectra of Some Halogenated Propenes
Authors: Swalen J. D. , Reilly C. A. 
Published: January 2005

The 40-Mc/sec nuclear magnetic resonance (NMR) spectra of CF3CF=CF2, cis and trans isomers of CF3CCl=CFCl, and CF3CCl=CF2 have been analyzed in terms of the NMR parameters of the molecules; i.e., the magnetic shielding constants of the various fluorine nuclei and the spin-spin coupling constants between them.
The spectrum of perfluoropropylene, CF3CF=CF2, has been analyzed adequately by a first-order perturbation treatment. The spectrum of each of the isomers of CF3CCl=CFCl has been analyzed exactly as an AB3 system of spins by the use of the trace relations only. In a previous analysis of the cis-isomer, a small signal from the trans-isomer was not identified. This small signal has now been proved to arise from the trans-isomer. The spectrum of CF3CCl=CF2 has been analyzed by an interative scheme on an electronic computer. Here the nuclei were treated as an ABC3 system of spins.
The various magnetic parameters determined by these analyses have been compared with the molecular structures and have been briefly discussed in terms of the theories of the magnetic properties of molecules.