bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Calculation of Energy Eigenvalue Spectra from Time Evolution of Nonstationary States
Authors: Blinder S. M.
Published: January 2005

An arbitrary function in the eigenfunction space of some quantum-mechanical Hamiltonian may be thought to represent the initial configuration ψ(q,0) of a nonstationary state. The system develops in time according to ψ(q,t)=exp(−itH)ψ(q,0)= ∑ k=0∞(−it)kk!Hkψ(q,0).Defining F(t)≡〈ψ(q,0), ψ(q,t) 〉, and hk≡〈ψ(q,0), Hkψ(q,0) 〉, and taking the Fourier transformG(ω)= ∫ −∞∞dtexp(−iωt)F(t),we obtain G(ω)=2π ∑ k=0∞hkk!(ω).In terms of the formal expansion in the energy eingenfunctions ψ(q,0)= ∑ n=0∞cnφn(q)+ ∫ 0∞dωc(ω)φ(ω,q),the Fourier transform represents G(ω)=2π ∑ n=0∞|cn|2δ(ω+ωn)+2π|c(−ω)|2,which exhibits, in principle, the entire eigenvalue spectrum. In this paper, a direct method of calculating eigenvalue spectra, based on the foregoing principle, is proposed. Two modifications are required for computational practicability: (i) use of a finite representation for the delta function and truncation of the summation (a); (ii) replacement of the integrals hk by hk(q′)≡Hkψ(q,0)]q=q′. The modified spectral function is taken to be GN(τ,ω,q′)=2π ∑ k=0Nhk(q′)k!χτ(k)(ω),with χτ(ω)≡sinτω/πω. The sequence GN(τ,ω,q′) is shown to converge as N→∞ if in the Expansion (b) the coefficients cn and c(ω) decrease with ω as exp(—ω/λ) or faster. Assuming convergence, the spectral function represents a broadened eigenvalue spectrum.
Integrated Intensity Measurements of the 5.3-μ Fundamental and 2.7-μ Overtone Bands of NO between 1400° and 2400°K
Authors: Breeze J. C. , Ferriso C. C.
Published: January 2005

Measurements have been made of the total integrated band intensities of the 5.3-μ fundamental and the 2.7-μ first overtone bands of NO in the temperature range 1400° to 2400°K. The NO gas sample was studied at high temperatures using a reflected shock-wave technique.

Within the temperature range used in the present experiments, the integrated band intensity of the NO fundamental does not vary. However, the integrated intensity of the first overtone band of NO shows a small temperature dependence. The temperature dependencies of the two bands are in agreement with theoretical temperature dependencies determined assuming a harmonic oscillator approximation to the NO molecule. Using the theoretical temperature dependencies the experimental data have been extrapolated to give values of the integrated intensities α° at STP. The values of α° obtained for the fundamental and first overtone bands of NO are 76±7 cm—2·atm—1 and 2.8±0.5 cm—2·atm—1, respectively.
Intermolecular Forces: The Triangle Well and Some Comparisons with the Square Well and Lennard-Jones
Authors: Feinberg M. J. , De Rocco Andrew G.
Published: January 2005

Extending the methods of Kihara and of Alder and Pople for B3 and using a machine procedure for B4, we have calculated the virial coefficients for a potential with a hard core and a linear, finite attractive well. A comparison of these results with the SW and LJ potentials reveals distinctions which become more marked as one goes to higher coefficients. For B3 the TW is systematically closer to the LJ and this result is interpreted by analysis of the contributions made to B3 by collision situations ranging from three particles in the attractive well to three in the repulsive field. A nonzero force is seen to be necessary if the detailed behavior of B3 is expected. For B4 larger differences were noted and the so-called ``area rule'' was not obeyed even approximately, in contrast to B3. The critical constants were computed by truncating the series at B4, and the results compared to those for a SW and a LJ.
Infrared Absorption Spectra of Solid Solutions: Cluster Formation of Nitrate Ions in Alkali Halides
Authors: Van der Elsken J. , Kroon S. G.
Published: January 2005

Satellite bands appearing in spectra of dilute solid solutions of nitrate ions in alkali halide crystals have been identified as arising from clusters of two or more nitrate ions. The dependence of the number of clusters on the concentration has been determined. Out of the discrepancy between this dependence and the theoretically expected dependence an interaction energy can be estimated.
Ionization Potentials of Alkyl Free Radicals and of Benzene, Toluene, and Triethylamine by the RPD Technique
Authors: Melton Charles E. , Hamill W. H.
Published: January 2005

A time-of-flight mass spectrometer with a source of effectively monoenergetic electrons has been utilized to determine the ionization potentials and ionization-efficiency curves of the stable compounds benzene, toluene, triethylamine and of the free radicals, methyl, ethyl, n-propyl, and isopropyl. The appearance potentials in electron volts observed for the stable compounds were C6H6: 9.20, 9.40, 9.65; C6H5CH3: 8.80, 9.20, 9.50; (C2H5)3N: 7.68, 8.18, 8.55, 8.95, 9.40. Published values for the appearance potentials by electron impact of these compounds tend to converge upon one of the higher values observed in this work.

The radicals were produced by thermal—catalytic decomposition of appropriate alkyl nitrites, isopropyl ether, and isobutane. Appearance potentials (electron volts) determined for the free radicals were as follows: methyl—9.80, 10.3, 10.7, 11.4; ethyl—8.25, 8.7, 9.3; n-propyl—8.15, 8.6, 8.8, 9.2, 9.6; isopropyl—7.52, 8.1, 8.6. The measured ionization potentials of methyl, ethyl, and propyl free radicals were considerably lower than published values by electron impact.
Crystal Structure of Li6BeF4ZrF8
Authors: Sears D. Richard , Burns John H.
Published: January 2005

The crystal structure of Li6BeF4ZrF8 has been determined by x-ray diffraction. The tetragonal unit cell, having a=6.57, c=18.62 Å, contains four formula weights; the space group is D4h19—I41amd. Discrete BeF42— and ZrF84— ions are connected by shared Li+ ions. The BeF42— tetrahedron is quite regular with a Be–F distance of 1.57±0.01 Å; the ZrF84— dodecahedron has two independent Zr–F bonds of 2.05±0.01 Å and 2.16±0.01 Å, and deviates considerably from the shape predicted by theory.
Quantum Tunnel Model for Hard Spheres
Authors: Oden Lynn , Henderson Douglas
Published: January 2005

In the tunnel model of Barker a fluid is regarded as being composed of lines of molecules which move almost one-dimensionally in lines or tunnels, the walls of which are formed by neighboring lines of molecules. This model provides a simple and reliable theory for a classical system of hard spheres. In this paper the tunnel model is formulated for quantum fluids and is applied to a system of hard spheres. The resulting thermodynamic properties are calculated and appreciable quantum corrections are found to be present even at relatively high temperatures.
Study of the Born—Oppenheimer Approximation with Application to H2
Authors: Fisk George A. , Kirtman Bernard
Published: January 2005

A method for evaluating energy corrections dur to breakdown of the Born—Oppenheimer (BO) approximation in ordinary diatomic molecules has been developed. It is shown that the effective potential for nuclear motion depends upon both the vibrational momentum and the internuclear distance. Energy levels for H2 have been calculated by numerical solution of the Schrödinger equation for motion in this effective potential. The v=0 level is shifted ∼0.2 cm—1 by non-BO terms as compared to the total anharmonicity correction of about 30 cm—1. This shift is an order of magnitude too small to explain the difference between the best theoretical and experimental values of D00.
Spin Delocalization in Metallo-Pyrromethenes and Porphyrins
Authors: Eaton D. R. , LaLancette E. A.
Published: January 2005

Fermi contact shifts have been observed in the NMR spectra of Ni II and Co II pyrromethenes and of Fe III tetraphenylporphyrin chloride. These shifts have been interpreted in terms of delocalization of spin from the metal d orbitals to the lowest antibonding ligand π orbital.
Molecular Motion in Solid HCl and DCl. Quadrupole Coupling in the Low-Temperature Phase
Authors: Marram E. P. , Ragle J. L.
Published: January 2005

The 35Cl pure quadrupole spectra of HCl and DCl have been examined by pulse techniques between 50°K and the phase transformations at 98.36° and 105.03°K. In these materials, T1 is shorter than about 400 μsec above about 63° and 77°K, respectively, but shows behavior typical of a thermally activated rate process at lower temperatures. Activation energies for both compounds are 2.70±0.05 kcal/mole, in good agreement with values obtained from dielectric constant data. In HCl, T2, probably determined by the proton moment, is of the order of two to three times T2*, while in DCl T2 is 40 to 50 times T2* in the temperature range for which it is not controled by T1.

The data are discussed in terms of possible molecular motions in the solids in the low-temperature phase.
Motion of the H2O Molecule in Potassium Oxalate Monohydrate
Authors: McGrath J. W. , Paine A. A.
Published: January 2005

The proton magnetic resonance doublet splitting was measured for potassium oxalate monohydrate in the range from 74° to 395°K. The equilibrium position of the proton—proton vector was always perpendicular to the magnetic field. The measurements were made for orientations of the crystal such that the H–O–H bisector was parallel or perpendicular to the field. The doublet splitting is virtually independent of the temperature up to 395°K. However, the H2O molecules is in zero-point vibration. The angular amplitudes of the torsional and rocking motions are about 11° and 10°, respectively.

The orientational potential energy of the H2O molecule appears to be made up of a hydrogen-bond component and an electrostatic component due to nearest potassium ion neighbors. A reasonable, nominal H-bond energy and a reasonable, simple charge model for the H2O molecule yielded computed torque constants of 28 and 36 kcal/mole for the torsional and rocking motions, respectively. The proton—proton separation is found to be 1.54 Å when the raw value is corrected for the effects of molecular vibration. The results favor the crystal structure given recently by Pedersen.
Correlation Energy of Two-Electron Systems
Authors: Rosenfeld J. L. J. , Konowalow Daniel D.
Published: January 2005

Correlated closed-shell and open-shell functions (due to Roothaan and Weiss) are analyzed in terms of a 1/Z expansion to obtain the corresponding first-order wavefunctions and the second-order energy. The need for expanding the open-shell functions in powers of Z—½ is demonstrated. The contributions to the second-order energy from radial and angular correlation are estimated.
Intramolecular Cross Linking and Chain Dimensions in Amorphous Polymers
Authors: Graessley William W.
Published: January 2005

This paper concerns the relationship between the average dimensions of chains in a polymer solid and the subsequent frequency of intramolecular cross linking when adjacent units are joined at random. Equations are developed for calculating the relative proportion of intramolecular (loop-forming) links prior to the gel point, and the result is specialized to the case of molecules having a Gaussian segment distribution, an approximate representation of the presumed state of affairs in amorphous polymers. An apparent deviation from Stockmayer's equation for the cross-linking density at the gel point is predicted, the magnitude of the departure depending on the average dimensions of the random coil molecules. These deviations are shown to be small for chains with moderately large numbers of segments if the coil dimensions in the solid are similar to those in a θ solvent. Some evidence that the individual chains may, in fact, be more compact in the solid is furnished by gelation data obtained in the cross linking of several well-characterized samples of polystyrene by high-energy radiation.
Photochemical Addition of Hydrogen Bromide to 2-Butene in the Gas Phase
Authors: Oldershaw G. A. , Cvetanović R. J.
Published: January 2005

The relative rates of the photochemical addition of hydrogen bromide to 2-butene, and of the simultaneous cis—trans isomerization have been measured in the gas phase at 54°C. Similar but less extensive experiments have been carried out with 1,2-dideuteroethylene. In this case, comparison of the rates with the data in the literature indicates much faster cis—trans isomerization than can be expected from the decomposition of thermalized bromoethyl radicals. Alternative explanations of the fast geometric isomerization are briefly discussed.
Accurate Adiabatic Treatment of the Ground State of the Hydrogen Molecule
Authors: Kol/os W. , Wolniewicz L.
Published: January 2005

Accurate ground-state energies of the hydrogen molecule have been computed using wavefunctions in the form of expansions in elliptic coordinates and including explicitly the interelectronic distance. The computations have been made with 54-term expansions (0.4≤R≤3.7) and with 80-term expansions (0.5≤R≤2.0). For the equilibrium internuclear distance, the best total energies obtained in the two cases are —1.1744701 a.u. and —1.1744746 a.u., respectively, the corresponding binding energies being 38 291.8 and 38 292.7 cm—1. Employing the 54-term wavefunctions, the relativistic corrections and the diagonal corrections for nuclear motion have been computed for several internuclear distances. For equilibrium their contributions to the binding energy have been found to be —0.526 and 4.947 cm—1, respectively. Thus the final theoretical binding energy for H2 amounts to 38 297.1 cm—1 and is a little larger than the experimental value 38 292.9±0.5 cm—1. The discrepancy may be due to the adiabatic approximation.
On the Kinetic Theory of Dense Fluids. XVIII. The Bulk Viscosity
Authors: Gray Peter , Rice Stuart A.
Published: January 2005

A formula for the bulk viscosity of a simple liquid has been obtained from the solutions of the kinetic equations proposed by Rice and Allnatt. The reliability of numerical results obtained is limited to about ±20% by uncertainties in the radial distribution function, its density dependence, and the pair potential. Nevertheless, the theory unambiguously predicts that the ratio of bulk to shear viscosity for liquid argon, at a density of 1.12 g·cm—3 and temperatures between 128° and 185°K, should be approximately 1.3.
Spin Densities in Alkali-Metal—Ammonia Solutions
Authors: O'Reilly D. E.
Published: January 2005

Wavefunctions for the alkali metal monomers of Li, Na, Rb, and Cs in liquid ammonia are calculated using a multipole expansion potential. The wavefunctions are made orthogonal to molecular orbital wavefunctions for the ammonia molecules surrounding the metal ion and spin densities at the metal, nitrogen, and hydrogen nuclei are calculated. A model is proposed for the cavity species which is exactly soluble within the same approximation. Spin densities are evaluated at nitrogen and hydrogen nuclei following orthogonalization to wavefunctions of ammonia molecules on the periphery of the cavity. Orthogonalization produces a large enhancement of spin density at nitrogen and a corresponding decrease in spin density occurs at hydrogen due to a node in the wavefunction produced by orthogonalization. The calculated spin density at the metal nucleus of the monomer and at nitrogen of the cavity species are in good agreement with experimental values. An explanation for the negative spin density at the protons is proposed.
Nuclear Magnetic-Dipole Coupling in Solid BF3
Authors: Casabella P. A.
Published: January 2005

The nuclear magnetic resonances of 11B and 19F have been studied in solid polycrystalline BF3 at 77°K. From a study of the 11B resonance, the 11B nuclear quadrupole coupling constant was found to be 3.045±0.060 Mc/sec. The 19F resonance possessed an unusual asymmetric structure that is explainable in terms of a magnetic-dipole interaction between a 19F nucleus and its nearest-neighbor 11B nucleus. An analysis of this interaction revealed that the observed asymmetry of the 19F resonance indicates that the 11B quadrupole coupling constant is positive. Furthermore, the width of the 19F resonance leads to a value of 1.29 Å for the distance between nearest-neighbor boron and fluorine atoms in the solid in excellent agreement with the known values for BF3 gas.
Magnetic Properties of Gd–Sc Alloys
Authors: Nigh H. E. , Legvold S. , Spedding F. H. , Beaudry B. J.
Published: January 2005

Magnetic properties of some Gd–Sc alloys have been measured. Paramagnetic to antiferromagnetic to ferromagnetic transitions were observed in the 69 at. % Gd alloy. Alloys of higher Gd content were ferromagnets and those of lower Gd content were antiferromagnets. The paramagnetic Curie temperatures decreased with decreasing Gd concentration. The effective number of Bohr magnetons per Gd atom showed a nearly linear increase with decreasing Gd concentration. Also the saturation magnetic moment per Gd atom increased with decreasing Gd concentration in the case of the ferromagnets.
Energy of Excimer Luminescence. II. Configuration Interaction between Molecular Exciton States and Charge Resonance States
Authors: Azumi Tohru , Armstrong Andrew T. , McGlynn S. P.
Published: January 2005

A four-electron MO treatment of the interaction of the D2h polyacenes naphthalene, anthracene, pyrene, and perylene to yield D2h dimers is developed, and the energies of these dimers are calculated as functions of the effective nuclear charge to be used in a Slater orbital exponent, and of the intermolecular distance D. Agreement with excimer luminescence energies is obtained for values of Z∼3 and values of D between 3.0 and 3.6 Å. Contact absorption processes are predicted to occur and are discussed. An Appendix which provides simple analytic expressions for four different types of penetration integrals is included.
Solvent Effects on the Non-Newtonian Viscosity of Dilute Solutions of Flexible Linear Macromolecules
Authors: Subirana Juan A.
Published: January 2005

The average density of segments within a macromolecular coil decreases when the molecule is deformed by shear. Consequently, the excluded volume effects, and therefore the intrinsic viscosity, diminish as the rate of shear increases. The magnitude of the effect has been calculated for flexible polymers introducing the following simplifications: (1) An approximate density distribution of segments is used. (2) The degree of expansion α of the hydrodynamically deformed macromolecular coil is calculated using Flory's method. (3) The expanded macromolecule behaves hydrodynamically as a Gaussian coil of the same size. Some interesting conclusions are derived from the theory and are supported by the experimental results: (1) The non-Newtonian viscosity of polymer solutions should be studied in θ solvents to eliminate excluded volume effects. (2) The influence of shear increases with solvent power. (3) At large rates of shear all solvents behave as θ solvents. (4) Stiff chains and polyelectrolytes show a much more pronounced influence of rate of shear at relatively low molecular weights, which cannot be explained by the present theory.
Sound Absorption in Binary Mixtures of Halomethane Gases
Authors: Wang M. L. , Boade R. R. , Legvold Sam
Published: January 2005

Results of sound absorption measurements on binary mixtures of CH2F2, CHF3, CF4, and CCl2F2 are given. The mixtures show no evidence of multiple dispersion. The observed relaxation times are discussed in relation to a theory of Calvert and Amme.
Analysis of Isotope Exchange Reactions among Nitrogen Oxides Involving N2O3
Authors: Monse E. U. , Kauder Lois Nash , Spindel W.
Published: January 2005

The fundamental frequencies of isotopic N2O3 molecules and equilibrium constants of isotope exchange reactions involving N2O3 have been calculated from available spectroscopic data. The calculations are compared with observed fractionation factors for nitrogen isotope exchange between N2O3 and NO, reported previously, and with experimental fractionation factors for oxygen isotope exchange, reported in this paper. The effect of phase changes on the isotopic equilibrium constant has been estimated.
Line-Reversal Studies of the Sodium Excitation Process Behind Shock Waves in N2
Authors: Hurle I. R.
Published: January 2005

Spectrum-line reversal measurements of the time variation of Na excitation temperatures behind shock waves in N2 over the range 1720°—4340°K are described. From a comparison of the results with recent interferometric and infrared measurements of N2 vibrational relaxation, made also behind shock waves, it is shown that the observed Na excitation temperature is identified with the vibrational temperature of the relaxing nitrogen molecules. The present measurements thus confirm that the thermal excitation of Na by energy transfer from the N2 vibrational mode occurs with a much higher probability than by transfer from the rotational or translational modes. This result removes recent doubts concerning the interpretation of Na-line reversal temperatures in terms of N2 vibrational temperatures in earlier shock-tube studies. The probability of Na excitation by vibrationally excited N2 at the temperatures concerned is shown to be close to unity. The Na–N2 interaction process in various environments is briefly discussed in the light of this and other quenching measurements at low temperatures.

The measurements were made with a double-beam spectrum-line reversal system in which the sodium emission and absorption intensities are both recorded in the same optical path. The high-temperature measurements were made using a calibrated xenon arc as the background source for reversal. For the low-temperature measurements a tungsten strip lamp was employed. The system is able to measure Na-line reversal temperatures from 1500° to 5500°K to within an accuracy of ±2% and with a time resolution of 1 μsec. The optical arrangement and xenon source characteristics are described in detail.
Two-Step Energy Transfer in Solution
Authors: Gallagher P. K. , Heller A. , Wasserman E.
Published: January 2005

In the presence of terbium ions, a transfer of energy is observed from 4,4′-dimethoxybenzophenone (DMB) to europium ions. This transfer does not take place in the absence of terbium and it is concluded that the terbium ion serves as an intermediate in the energy transfer. Fluorescence and excitation spectra, fluorescence lifetimes, and time-resolved excitation spectra are presented to substantiate the proposed nonradiative two-step energy transfer.
Transfer of Triplet-State Energy and the Photoreactive State of Anthracene
Authors: Kusuhara S. , Hardwick R.
Published: January 2005

The transfer of electronic energy from the triplet states of coronene and anthraquinone to that of anthracene may be observed in bromobenzene, but does not occur in solutions of Lucite plastic; this finding supports the proposal that collision is necessary to efficient triplet—triplet energy transfer. Using these systems, the photoreactive state of anthracene with carbon tetrachloride was studied. Comparison was made of the reaction rates in carbon tetrachloride; (a) when anthracene was excited in such a way as to populate both the excited singlet and triplet states, and (b) when anthracene was excited by energy transfer so that it was populated only in its triplet state. The results show within experimental error that it is possible for the entire photoreaction of anthracene and CCl4 to take place via the triplet state of anthracene.
Optical Radiation from Nitrogen and Air at High Pressure Excited by Energetic Electrons
Authors: Davidson G. , O'Neil R.
Published: January 2005

The spectral characteristics and fluorescent efficiencies for electron excitation of nitrogen and air at 600 Torr have been determined. Results are presented for the efficiency of conversion of electron energy to optical radiation in approximately one hundred resolved spectral components of air and nitrogen between 3200 and 10 800 Å when bombarded by 50-keV electrons. The total fluorescent efficiency under these conditions is (0.14±0.02)% for nitrogen and (6.7±1.0)×10—3% for air. In nitrogen the first positive (B 3Πg→A 3Σu+), second positive (C 3Πu→B 3Πg), Gaydon green, Herman infrared, and Goldstein—Kaplan (C′ 3Πu→B 3Πg) band systems of N2 and the first negative (B 2Σu+→X 2Σg+) band system of N2+ were observed. The (0–2) and (0–3) transitions of the Herman infrared system and [N I]32(2D—2P) forbidden doublet at 1.04 μ, previously unreported in the laboratory, were observed. In air the first positive and second positive band systems of N2 and the first negative band system of N2+ were observed as well as atomic spectra of nitrogen, oxygen, and argon.
Gas-Phase Radiolysis of n-Pentane. A Study of the Decompositions of the Parent Ion and Neutral Excited Pentane Molecule
Authors: Ausloos P. , Lias Sharon G.
Published: January 2005

The direct and inert-gas-sensitized radiolyses of equimolar n-C5H12–C5D12–NO mixtures have been investigated in the absence and presence of an applied electrical field. It is shown that the partially deuterium-labeled products remain essentially unchanged upon the application of an electrical field, while the yields of the fully deuterated and nondeuterated species increase indicating that the former entirely originate from ionic processes. Comparison of the ion-pair yields of these partially labeled products, which can be ascribed mainly to hydride ion transfer from pentane to carbonium ions, with the ion-pair yields deduced from the 70-eV mass spectral pattern shows that, in the direct radiolysis, those fragment ions which are formed with a high activation energy are produced in a lower yield than in the mass spectrometer and are also reduced most strongly by an increase in pressure. In all experiments, both the propyl and butyl ions formed in the decomposition of the pentane ion acquire the secondary configuration either prior to or during reaction. In the inert-gas-sensitized radiolysis, the fragment ions which are formed with a high appearance potential are seen to increase with an increase in the recombination energy of the added inert gas.

From the applied-field experiments, it was possible to determine the modes of decomposition of neutral excited pentane molecules formed by electron impact. These were found to be analogous to those deduced from vacuum-ultraviolet photolysis experiments carried out at 1470 or 1237 Å. On the basis of the information gained from these experiments, and a detailed isotopic analysis of the products formed in the radiolysis both in the presence and absence of benzene, a value of 0.3±0.05 could be deduced for the number of neutral excited molecule decompositions per ion pair. Neutral excited pentane molecules are also seen to be formed in the inert-gas-sensitized radiolysis.
Reaction of PbS Surfaces with Oxygen
Authors: Hillenbrand L. J.
Published: January 2005

The reaction of fresh PbS surfaces with oxygen was studied by crushing the sample in a clean, degassed system. The reaction of PbS with oxygen was noted at room temperature, but the rates were conveniently measurable only above about 100°C. The reaction did not stop at monolayer coverage and showed no inflection in rate at that extent of reaction. The rate of the reaction was found to be directly proportional to the area of the PbS surface, and the pressure of oxygen over the surface, and inversely proportioned to the thickness of the reaction product layer for extents of reaction in excess of 0.4 mole O2 reacted per mole PbS on surface initially. Although the main products of the interaction were SO2 and lead oxides, considerable amounts of CO2 were detected, in spite of attempts to purify the PbS by recrystallization from the vapor. The complexities of the reaction of PbS with oxygen, and probably the performance of PbS-film devices, are related to a considerable extent to the difficulties in obtaining clean PbS surfaces for reaction. The extent of these difficulties does not appear to have been fully appreciated in earlier work.
Electron Spin Resonance Study of the Antiferromagnetism of Chromia Alumina
Authors: Poole Charles P. , Itzel John F.
Published: January 2005

Chromia alumina mixtures calcined between 500° and 1400°C were studied by electron spin resonance (ESR) in the temperature range from 125° to 550°K. The low-chromia content chromic ions are paramagnetic while at high-chromia contents the ESR spectra exhibit antiferromagnetic behavior. For Cr/Al ratios greater than ⅔ the 1400°C calcination samples produce sharp Néel points which increase with chromia content, while the samples with Cr/Al ratios less than ½ show broad Néel points which become less well resolved with decreasing chromia content. The spectra of high Cr/Al ratio samples calcined at 900°C and below are superpositions of a βw phase resonance which appears paramagnetic and a βn phase resonance which has a fairly sharp Néel point several degrees below the bulk chromia value, and the latter is attributed to clumps of chromia in the sample.
Analytical Hartree—Fock Functions. IV. Isoelectronic Series for 31 to 36 Electrons and Conclusions
Authors: Clementi Enrico
Published: January 2005

The Hartree—Fock functions have been obtained in the Roothaan—Hartree—Fock approximation for the neutral, first positive, and first negative ions of the elements Ga, Ge, As, Se, Br, and Kr. The ground and the excited states of the ground-state configuration are reported. With this paper, we have completed the analysis of the first third of the periodic system in the Roothaan—Hartree—Fock approximation. The experiences gained in this work were used in analyzing the major obstacles which lie ahead in order to complete the analysis to the remaining elements of the periodic system. The major obstacles are (i) in the treatment of the relativistic energy, (ii) in the construction of a ``control program'' which will supervise the use of a relativistic Hartree—Fock program, and (iii) in the programmation of a relativistic Hartree—Fock program which combines speed and accuracy.
Zeeman Effect and Rotational Analyses of the Near-Ultraviolet Bands of CS2
Authors: Douglas A. E. , Milton Earl R. V.
Published: January 2005

The Zeeman effect of the near ultraviolet absorption bands (B2←1Σg+) of CS2 has been studied at high resolution. It has been found that the magnetic moment in the excited state increases linearly with the rotational quantum number J and reaches a value in excess of one Bohr magneton at J=50. The Zeeman effect can be understood if it is assumed that the observed B2 state is one component of a 3A2 state in which the triplet splitting is large. It is shown that this interpretation is consistent with the observed spectrum and with the excited states expected for CS2. The rotational structures of a number of bands have been analyzed and the rotational constants are given.
Optical Properties of Molecular Aggregates. I. Classical Model of Electronic Absorption and Refraction
Authors: DeVoe Howard
Published: January 2005

A theoretical classical model is developed to predict the absorption and refraction of an aggregate of monomer units (a molecular aggregate, molecular crystal, or polymer) at any frequency. The monomers are treated as having complex electronic polarizabilities whose frequency dependence is determined by the absorption bands of the isolated monomers. Polarizations in the aggregate induced by incident light are modified by Coulombic interactions between the monomers. No first-order approximation is involved as in exciton theory. The molar extinction coefficient and molar refraction are obtained from normal mode polarizabilities found by solving an eigenvalue problem. The predicted absorption spectra agree (to first order in interaction energy) with exciton theory in the limit of weak coupling, with the hypochromism theory of Tinoco and Rhodes, and (for a classical oscillator model) with exciton theory for strong coupling. The oscillator strength sum rule is obeyed. The predicted spectrum of a pair of dyelike monomers is illustrated for the cases of weak, intermediate, and strong coupling.
Third Virial Coefficient for the Kihara, Exp-6, and Square-Well Potentials
Authors: Sherwood A. E. , Prausnitz J. M.
Published: January 2005

The classical third virial coefficient, assuming pairwise additivity, has been calculated by numerical integration for the Kihara and exp-6 potential functions. The nonadditive contribution, using the three-body potential model of Midzuno and Kihara (modified in the case of nonsixth-power attraction) has also been calculated numerically for the Kihara, exp-6, and square-well potentials. Results are tabulated for each potential model at 40 reduced temperatures from 0.50 to 100.0 and for a range of third parameter values. A comparison is made of the change in emphasis on intermolecular separation between the second and third virial coefficients.
Anomalous Effects in EPR Spectra of the Azulene Anion
Authors: Reddoch A. H.
Published: January 2005

The proton hyperfine coupling constants of the azulene anion in dimethoxyethane with lithium ions show systematic variations of the order of 10% as temperature and concentration are changed. No splitting is observed from the lithium ion. As the concentration decreases, the variations of the five proton coupling constants are linearly related and the coupling constants approach those obtained by Bernal, Rieger, and Fraenkel for azulene in dimethylformamide with tetra-n-propyl ammonium ions. As the temperature is lowered, the coupling constants change rapidly until by about —40°C they are close to those of Bernal et al. At lower temperatures the change is small. At —40°C the peak heights of the lines are those predicted by the degeneracies of the nuclear spin states. At higher temperatures the peak heights become anomalous and the widths of the lines vary from line to line.

These effects are explained by a model involving a rapid chemical equilibrium between two states of the azulene—lithium ion system, having different degrees of association and different proton coupling constants. The less associated form has coupling constants similar to those of Bernal et al. and is more stable at low temperatures and concentrations. The anomalous linewidths are shown to result from the perturbation caused by the association and dissociation of the azulene—lithium ion pairs and are quantitatively related to the measured variations in the coupling constants.
Structure of Molten Oxides in the System: 0.25 Na2O·(0.75-x)GeO2·xSiO2
Authors: Riebling E. F.
Published: January 2005

The counterbalanced-sphere technique was used to obtain high-temperature viscosity and density data for a series of Na2O·GeO2·SiO2 ternary melts. These compositions contained a fixed amount of Na2O (∼25 mole %). The effect of gradual SiO2 substitution for GeO2 was studied at 1300°C.

The data have been interpreted in terms of a model that involves no change for the partial molar volume of SiO2 (v̄SiO2). It is concluded that the elimination of GeO6 octahedra is not continuous with the gradual substitution of SiO2 for GeO2. A 0% to 10% replacement of GeO2 results in a slight decrease of the number of GeO6 octahedra. The partial molar volume results suggest that most of the GeO6 octahedra are transformed to GeO4 tetrahedra between 30% and 50% GeO2 replacement.
Phonon-Induced Exciton Interactions
Authors: Chesnut D. B.
Published: January 2005

Second-order perturbation theory is used to calculate the effective exciton—exciton interaction potential resulting from a first-order exciton—phonon coupling in a linear chain of ``diatomic'' molecules. The calculations imply that the virtual exchange of acoustic phonons leads to an attractive interaction while virtual exchange of optical phonons tends to cause a repulsive potential. The two limiting cases of strongly and weakly bound dimers are investigated and are used to suggest that the phonon-induced interaction potential in the systems of interest is probably attractive.
Parabolic Growth Law for Coherent Oxides
Authors: Fromhold A. T.
Published: January 2005

The Wagner derivation of the parabolic growth law is shown to be inconclusive, since the rate constant can be a function of film thickness. The additional criterion to be met is that the dependence of concentrations C(x, L) on position x and film thickness L(t) be a function of x/L(t) only. This can be examined for any particular case by solving the appropriate diffusion equation and applying the proper boundary conditions. The condition that C(x, L) be a function of x/L(t) for parabolic growth is in accordance with the results of previous work showing that surface charge due to two diffusing species enhances the parabolic rate constant but space charge causes deviations from the parabolic law. The functional form of C(x, L) is examined further by solving the diffusion equation for the general cases in which mobilities μ vary arbitrarily with temperature and concentration. The parabolic law with modified rate constants is shown to be valid for these general cases, unless the values of | μC | for the two oppositely charged species do not differ by more than an order of magnitude and the mobilities depend strongly on several powers of the concentration.
Appearance Potentials of Positive and Negative Ions by Mass Spectrometry
Authors: Melton Charles E. , Hamill William H.
Published: January 2005

Appearance potentials (AP) of ions were obtained by the retarding potential difference (RPD) technique using a time-of-flight mass spectrometer. Confirmatory measurements were made using a 180° magnetic instrument. Information about processes such as ion-pair formation, electronic excitation of ions, rearrangement of ions, autoionization and metastable transitions is inferred from the structure of the ionization efficiency (IE) curves of Xe, H2, CH4, CD4, C2H4, C2H6, C3H8, and C4H10 over about a 4 eV range. The AP's in Xe at 12.02, 12.35, 12.75, and 14.0 correspond in a qualitative way to autoionization levels. The structure observed in parent and fragment IE curves for hydrocarbons can, in some systems, be correlated with known processes. Structure due to vibrational excitation of ions was not resolved. The IE curves for polyatomic ions indicate that many ions formed by electron impact are formed in electronically excited states, and that appearance potentials of fragment ions often correlate with upward breaks in the parent IE curves. Parent ion intensities did not decrease with increasing electron energy even at large degradation ion intensities. An AP at about 0.7 eV above onset was observed in all the IE curves of R+ from RH and shown to arise from R++H— formation. The ion-pair process is as probable as the ground-state ion—neutral reaction in the systems investigated. The structure in the fragment IE curves can explain some of the difficulties encountered in measuring appearance potentials. An example of interference by ion—molecule reactions is also reported. Appearance potential data obtained by RPD and by conventional techniques are compared.
Angular Dependence of the Scattering of Metastable Helium Atoms in Helium and Neon
Authors: Richards H. L. , Muschlitz E. E.
Published: January 2005

A molecular beam method has been used to perform scattering experiments with an atomic beam of metastable helium atoms in helium and neon. The atomic beam, in which some of the atoms had been excited by electron impact, was passed through a scattering chamber containing gas at low pressures and subsequently detected by electron ejection from gold surfaces. The 21S to 23S helium atom ratio in the beam was determined using an inhomogeneous magnetic field. Total collision cross sections for the scattering of both metastable helium atoms in helium and neon have been measured as a function of the angular resolution of the apparatus. Angular scattering coefficients in the angular range 7°—25° have been calculated. In both gases the scattering at these angles of 23S helium was larger than 21S helium. These differences can only be caused by differences in the interaction forces between the colliding particles. The results are consistent with the higher interaction of triplet metastable atoms with ground-state atoms calculated by Buckingham and Dalgarno. Separate measurements of the backward scattering allowed a lower limit of 2×10—16 cm2 to be set for the He*–He energy-transfer cross section.
Configuration Interaction in Crystal Field Theory
Authors: Rajnak K. , Wybourne B. G.
Published: January 2005

The effect of configuration interaction on the validity of the usual method of expanding the crystal field potential in terms of spherical harmonics is examined using second-order perturbation theory. It is found that for a configuration of equivalent electrons lN most mechanisms of configuration interaction lead to a simple scaling of the crystal field parameters Bqk. However, one-electron excitations, either from the lN shell to unfilled orbitals or from closed shells into the lN shell, result in a scaling of the Slater integrals Fk and in overt effects that cannot be accommodated by the Bqk parameters alone. As a result, the crystal field parameters can be expected to vary from one multiplet to another, even in the limit of Russell—Saunders coupling. The consequences of these overt configuration-interaction effects are discussed.
Triplet—Triplet Energy Transfer in Rigid Glasses: Lack of a Solvent Effect
Authors: Siegel Seymour , Judeikis Henry
Published: January 2005

Experiments were conducted to study the possible effects of the nature of the solvent in triplet—triplet energy transfer between aromatic molecules dissolved in rigid glasses. Electron paramagnetic and emission spectroscopy were used to monitor the energy-transfer processes. Results of the study indicate that the probability of triplet energy transfer is essentially independent of the solvent used.
Abnormalities in Vibrational Potential Constants
Authors: Pitzer Kenneth S. , Strickler S. J.
Published: January 2005

A summary is presented of potential constants for =C= valence-angle bending in a number of linear or quasilinear molecules. It is pointed out that these constants can vary over a wide range, with certain molecules having abnormally low values. One such low value in C3O2 helps to explain the infrared spectrum of that molecule. A very low value in C3, obtained from spectroscopic measurements, is found to conflict with thermodynamic data.
Single-Crystal X-Ray Diffraction Studies of α-N2 and β-N2
Authors: Jordan Truman H. , Smith H. Warren , Streib William E. , Lipscomb William N.
Published: January 2005

The structure of α-N2 is cubic in the space group P213 with four molecules per unit cell. A total of 49 independent observed single-crystal x-ray diffraction maxima yield R=Σ ‖Fo|−|Fc ‖ /Σ|Fo|=0.13. Two faint reflections, (501) and (520), violate the space group Pa3, which yields R=0.21. Molecular centers are displaced by 0.1 to 0.2 Å from the centrosymmetric positions in Pa3 along the [111] directions so that the symmetry is reduced to P213.

Some corrections have been made in the Lorentz factors for upper levels and for the absorption of x rays in the experimental arrangement in the β-N2 study. The value of R improves from 0.09 to 0.04 for the freely rotating model, and the best precession angle is 56.0° rather than 54.5° (both ±2.5°) for the precession model, which we prefer.
Spin—Rotation Interaction and Magnetic Shielding in Molecules
Authors: Flygare W. H.
Published: January 2005

Equations are derived relating the spin—rotation constants and magnetic shielding for any type of molecule. In general, the spin—rotation constants depend on the equilibrium nuclear positions and a second-order term involving the excited electronic states. The spin—rotation constants are interpreted by a localized theory in terms of the average excitation energy, average value of (1/r3), and the charge-bond order matrix of the associated LCAO—MO functions.
ESR Study of the Crystallographic Phases in Zn2P2O7:Mn and Zn2P2O7:Cu
Authors: Chambers J. G. , Datars W. R. , Calvo C.
Published: January 2005

The ESR spectra of Mn++ and Cu++ in Zn2P2O7 have been studied between room temperature and 200°C. A first-order phase transition is found at 132°C and a transition of higher thermodynamic order occurs near 155°C. The space group of Zn2P2O7 above 155°C is determined to be C-2/m, whereas between 132° and 155°C it is C-m. The value of | D | in the spin Hamiltonian for Mn++ ranges from 612 to 1319 G with nearly isotropic g values. The g values for Cu++ indicate an anisotropic environment with nearly axial symmetry about the z axis. The spectral lines of Zn2P2O7:Mn++ are broadened near the upper transition with the broadness dependent upon the particular electronic transition involved. This phenomenon is discussed in terms of possible mechanisms for the upper phase transition.
Infrared Induced Absorption of Dilute Solutions of H2 and D2 in Liquid Argon
Authors: Ewing George E. , Trajmar Sandor
Published: January 2005

The induced infrared absorption spectra of dilute solutions of H2 and D2 in liquid argon have been studied using a low-temperature cell with a path length of 0.5 m. The close correspondence between observed absorptions with narrow band widths (ν½∼20 cm—1) and vibration—rotation transitions calculated using the gas-phase molecule spectroscopic constants strongly suggests that H2 and D2 rotate freely in liquid argon. An interpretation of the observed broad absorption features (ν½∼100 cm—1) is considered in which they assigned to vibration—translation combination bands involving changes in translational energy of H2 (or D2) in its solvent cage. These translational energy levels shift with isotopic change of the solute. A cell model of the solution system is considered in which the H2 (or D2) molecules are assumed to translate in their solvent cages as isotropic harmonic oscillators. The predicted difference in translational energy levels between H2 and D2 in argon is in satisfactory agreement with the observed isotopic shifts. The selection rules which govern the vibrating—translating solute molecule transitions are derived for the model of the isotropic harmonic oscillator and are consistent with the observed absorptions. An estimate of the translational energy level spacing which is provided by considering the solute in solvent as a particle in a box gives values which are in order of magnitude agreement with the proposed interpretation of the broad absorptions. If the present assignments are correct the results of this investigation provide a basis for the determination of all the types of energy levels of the solute molecule: vibrational, rotational, and translational.
Relation of Variational Functions to Exact Function for H2+
Authors: Goodisman Jerry
Published: January 2005

Approximate wavefunctions for H2+ of the James and LCAO types are discussed in terms of their ability to serve as useful representations of the exact function. For a wavefunction to be suitable for this, we require that, in addition to giving a good energy, (a) it have a large overlap with the exact wavefunction, and (b) values obtained by variation for parameters in the approximation functions be the values required to maximize the overlap. With three-parameter functions, the overlap is essentially complete. The accuracy to which values of parameters can be predicted is only approximate, which may lead to difficulty when these are to be used to help understand the process of molecular binding.
Thermal-Spike Model of Low LET Radiolysis: Temperature Dependence of Reactions Induced by Radiolysis in Liquid Toluene
Authors: Ingalls R. B. , Spiegler P. , Norman A.
Published: January 2005

The yields and isotopic composition of hydrogen gas and the yields of bibenzyl from the 60Co gamma radiolysis of liquid toluene, toluene-α,α,α-d3 in the temperature range —90° to +100°C are reported. A thermal-spike model of the radiolysis of organic liquids is presented. This model accounts for the observed low-temperature dependence of hydrogen yields and is consistent with the established chemistry of hydrogen atoms. This model requires local ``temperatures'' in the thermal spike to be in the order of 500°C above the ambient temperature and suggests that a majority of the hydrogen atoms which react to form the product hydrogen gas do so in these regions of high ``temperature.''