bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Spectrum of d3 Ions in Trigonal Crystal Fields
Authors: Macfarlane R. M.
Published: January 2005

The effect of a trigonal crystal field on the energy levels of d3 ions is evaluated within the framework of the crystal-field model. Matrices of the trigonal-field potential for the d3 configuration are presented and used to discuss details of the ruby spectrum. Perturbation expressions for the effect of parameter changes on the energy levels are given. These enable some refinement of electrostatic and crystal-field parameters to be carried out. In particular the effect of the second trigonal parameter is found to be appreciable. Finally, the effect of the spin—orbit interaction is included and the eigenvalues of the total Hamiltonian are found to be in good agreement with the observed energy spectrum of ruby.
Time-Weighted-Average Approximation in the NMR Spectrum of CF2BrCFBrCl
Authors: Newmark R. A. , Sederholm C. H.
Published: January 2005

The spectrum of CF2BrCFBrCl has been redetermined at 150°K in CFCl3 as a solvent. The coupling constants, chemical shifts, and relative energies of the three rotamers have been determined with considerable care. Assuming that high-temperature coupling constants and chemical shifts are time-weighted averages of the coupling constants and chemical shifts of the individual rotamers, these quantities have been calculated for several high temperatures, and compared with the experimental values, which have been determined in the same solvent.

All of the spectra involved are typical ABX spectra. The experimental value for ½(JAX+JBX)Av is 0.6 to 1.3 cps lower than the calculated value. Excellent agreement is obtained between the calculated and observed chemical shift between the A and B fluorine atoms. At 371°K there is a large difference between the calculated and observed chemical shifts between any other pair of fluorine nuclei, including the solvent nuclei. This difference decreases linearly with temperature and extrapolates to 0 at approximately the temperature of the low-temperature data. The cause of these discrepancies is discussed.
Study of Low-Frequency Molecular Motions in HF, KHF2, KH2F3, and NaH2F3
Authors: Boutin Henri , Safford G. J. , Brajovic Velko
Published: January 2005

The spectra of KHF2, KH2F3, NaH2F3, and of liquid and solid HF were measured between 1200 and 30 cm—1 by the inelastic scattering of ``cold neutrons'' (0.005 eV). The spectrum of KHF2 is in agreement with previous infrared measurements and shows a peak at 147 meV corresponding to a deformation frequency ν2 of the F–H···F group and a broad peak at 13 meV due to a libration of this group. The observed spectra for KH2F3, NaH2F3, and solid and liquid HF were compared with that for KHF2 considering the known results than the F–F distance increases, the position of the H atom between the two fluorines becomes more asymmetrical, and the strength of the hydrogen bond decreases in going from the HF2— ion to H2F3— ion to HF. In this comparison, the known structure of the H2F3— ion is considered as being intermediate between that of HF2— and the zigzag hydrogen bonded chains in solid HF. As a result, the lines observed at 112 and 67 meV in the H2F3— spectra and in HF, respectively, are associated with the deformation frequency ν2 of the H–F–H group in these compounds. In addition, the spectra of H2F3— ions show a peak at a 15 meV attributed to a libration of the group. Both H2F3— and HF show peaks at 8 and 7 meV, respectively, attributed to a rotational motion of one F–H···F unit around the F–F bond. The observed spectrum of HF liquid, showing a high degree of association, is also discussed with respect to these motions.
Removal of Electron—Electron Poles from Many-Electron Hamiltonians
Authors: Hirschfelder Joseph O.
Published: January 2005

In many-electron problems, the Hamiltonian has poles 1/rij which produce difficulties in the solution of the Schrödinger equation HΨ = EΨ. If Ψ is taken to be φχ where φ= ∏ i>j[1+12rijexp(−αrij)],it is found that χ satisfies the new Schrödinger equation H′χ=Eχ where the new Hamiltonian H′ has no electron—electron poles.
On the Density—Intensity Calibration in Electron Diffraction Studies
Authors: Kimura K. , Bauer S. H.
Published: January 2005

A general formulation for the dependence of the optical density on exposure in electron diffraction photographs is given, and an analytical function for the density—intensity calibration is expressed in terms of observable density data.
Systematics of Vibrational Relaxation
Authors: Millikan Roger C. , White Donald R.
Published: January 2005

A large number of data points for the vibrational relaxation time (pτv in atm sec) of simple systems have been logarithmically plotted vs (T°K)—⅓. It appears that each system is well represented by a straight line, and that most of these straight lines when extended to higher temperatures intersect near the point [pτv=10—8 atm sec, (T°K)—⅓=0.03]. Systems with a small reduced mass μ are exceptions to such a simple convergence, and in an improved scheme, the location of the convergence point is dependent on the reduced mass. Such a presentation has lead to an empirical equation correlating available measurements of vibrational relaxation times: log10(pτv)=(5.0×10−4)μ12θ43[T−13−0.015μ14]−8.00, where θ is the characteristic temperature of the oscillator in K deg. This equation reproduces the measured times within 50% for systems as diverse as N2, I2, and O2–H2. In the worst case thus far, O2–Ar near 1000°K, it is off by a factor of 5.
Reaction between Nitric Oxide and Ozone in a Supersonic Nozzle
Authors: Marte J. E. , Tschuikow-Roux E. , Ford H. W.
Published: January 2005

The rate of reaction between nitric oxide and ozone in a supersonic nozzle was measured in the temperature range 245–345°K by following the absorption of ultraviolet radiation by ozone at 2537 Å. The specific rate constant was found to be k=1.19×1012e−2500/RTcm3·mole−1·sec−1The result is in good agreement with previous studies and confirms the bimolecular nature of the reaction. The experimental pre-exponential factor is in satisfactory agreement with one calculated from transition state theory.
Polymer Segmental Motion as Related to Hindered Rotation
Authors: Brandt W. W.
Published: January 2005

The rotational oscillational motions of small units of the polymer chain with respect to their nearest neighbors are investigated insofar as these oscillations may be responsible for the over-all motions or configurational changes of the chain molecules. It is assumed that each degree of freedom involved in the over-all motion is endowed with an energy given by a Boltzmann distribution and independent of the energies of its neighbors. Using mathematical results of Kac, an expression for the average ``jump'' frequency, that is, the frequency of occurrence of deflections of a critical magnitude, is obtained. This jump frequency is found to be strongly dependent on the criterion adopted for a successful jump, and on the number of degrees of freedom in the moving segment, or the segment size. There is an optimum segment size which increases with the required jump magnitude, in agreement with experiment. The temperature dependence of the jump frequencies is qualitatively correct. The results show that bond stretching and bond-angle distortions contribute little to the over-all configurational change, and even the nearly free rotation of chain units with large energies is of relatively minor importance (at 298.2° and 398.2°K, for polyethylene). The exact shape of the potential of hindered rotation near its minima and the type of subsidiary (gauche) minima present, on the other hand, affect the rate process very much.
Microwave Spectrum of Methyl Isocyanate
Authors: Curl R. F. , Rao V. M. , Sastry K. V. L. N. , Hodgeson Jimmie A.
Published: January 2005

The J0→1 and J1→2 a-type transitions of CH3NCO and CD3NCO have been studied. These transitions are complicated by the population of a number of internal rotation states. Several absorptions arising from the lowest energy internal rotation states have been assigned. The barrier to internal rotation of the methyl group in CH3NCO has been found to be 49±3 cal/mole from the splitting of the J3→4, K=±1, m=±3 transition by the barrier. The component of electric dipole moment parallel to the a axis has been found to be 2.81±0.06 D by measurement of the Stark effect. The nitrogen quadrupole coupling constant has been found to be eqQ=+2.3 Mc/sec.
Effect of Additives on the Ionic Reaction Mechanism in the Radiolysis of Methane
Authors: Ausloos P. , Lias S. G. , Gorden R.
Published: January 2005

This work describes the reactions of the ions C2H5+ and CH5+ with C3D8, C4D10, C5D12, as well as the reactions of C2D5+ and CD5+ with C3H8. It is shown that ethyl ions undergo a hydride transfer reaction with all higher hydrocarbons even though they are present at a concentration of only 0.01%. The scavengers NO and O2 react with ethyl ions effectively, provided the relative concentration of the higher hydrocarbons is less than that of the free radical scavengers. A proton-transfer reaction between CH5+ and higher hydrocarbons followed by a rapid decomposition of the protonated hydrocarbon into a carbonium ion and a neutral alkane molecule is shown to occur. From the data it can be deduced that at a methane pressure of 48 cm G(C2H5+) =0.9±0.2 and G(CH5+) =1.9±0.2. It is concluded that in earlier published studies of the radiolysis of methane, the C2H5+ and CH5+ ions reacted with the accumulated products or with the added free radical scavengers, thus excluding the neutralization of these two species.
Temperature and Pressure Dependence of the Co59 Nuclear Resonance Chemical Shift
Authors: Benedek George B. , Englman Robert , Armstrong John A.
Published: January 2005

We have measured with precision the temperature and pressure dependence of the Co59 nuclear resonance chemical shift (σ) in the octahedral cobalt complexes Co(NH3)63+, Co(CN)63—, and Co(NO2)63— in aqueous solution. The pressure and temperature range was 1 to 10 000 kg/cm2 and 3° to 80°C, respectively. From the pressure dependence of σ and a theoretical determination of the compressibility of the complexes we have deduced the dependence of the crystal-field splitting on the cobalt—ligand distance. A theory for the explicit temperature dependence of the chemical shift is presented. The fundamental parameters which enter the theory are the 15 normal mode frequencies when the cobalt electrons are in the ground state and when they are in the excited state. While the former quantities are known from the vibrational spectra of these complexes, the latter are unknown. By fitting the theory to the experimental data, one concludes that on the average the vibration frequencies in the 1T1g excited electronic state must be smaller than those in the ground state by about 30% for the cyanide and nitrite complexes and by about 20% for the ammonia complex. A nonlinear dependence of σ on the temperature is predicted by the theory and observed experimentally.
Potential-Energy Curve of the Lowest-Lying Triplet Sigma State of Lithium Hydride
Authors: Taylor Howard S.
Published: January 2005

The potential-energy curve of the lowest-lying triplet sigma state of lithium hydride has been computed by a variational technique. Linear combinations of products of two-center molecular orbitals were used to approximate the wavefunction. All linear and nonlinear parameters are minimized and open-shell techniques are utilized. The triplet state is shown to be of a repulsive nature.
Molecular Weight Distribution of Linear Polymers from Stress Relaxation in Polymer Melts
Authors: Peticolas Warner L.
Published: January 2005

The method of Menefee and Peticolas for obtaining the molecular weight distribution of linear polymers from stress relaxation after steady-state flow has been applied to data on melt samples: a linear polyethylene and polystyrene sample. The results offer considerable promise for a rapid estimation of the high molecular portion of the distribution curve.

The method is based on a rather straightforward extension of the theory of Roase to bulk molten polymers. A discussion of the validity of this process is given in the light of recent developments.
Kinetic Theory of Adsorption of Intermediates in Electrochemical Catalysis
Authors: Gileadi E. , Conway B. E.
Published: January 2005

The behavior of adsorbed intermediates in consecutive electrochemical reactions is discussed in terms of the steady-state rate equations, and a comparison with results obtained using the quasiequilibrium assumption is made. The adsorption pseudocapacitance vs potential plot is shown to be symmetrical only when the quasiequilibrium assumption is made, namely when the ratio of specific rate constants for the desorption step (which is rate determining) and initial ion-discharge step, is exceedingly small. The C—V relationship is calculated for three types of mechanism: (i) discharge followed by atom—atom recombination, (ii) discharge followed by first-order decomposition, (iii) discharge followed by ion—atom desorption; cases for activated and nonactivated adsorption conditions are distinguished. Deviations from the symmetrical quasiequilibrium behavior are shown to depend on the kinetic pathway and, for a particular mechanism, are larger the larger is the value of the Temkin parameter r (defined by the rate of change of apparent standard free energy of adsorption of the intermediate with coverage). For a given value of r, these deviations are shown to be largest for the pathway when discharge is followed by ion—atom desorption, and smallest for the case when discharge is followed by a first-order decomposition step. Further, for any one mechanism, conditions of nonactivated adsorption lead to larger deviations than for the case when activated adsorption occurs.
Mössbauer Studies of Iron Organometallic Complexes. I. Iron Tetracarbonyl Complexes
Authors: Collins R. L. , Pettit R.
Published: January 2005

Mössbauer absorption spectra at 78°K have been obtained for a series of compounds of the form R:Fe(CO)4, where R includes triphenylphosphine, triethylphosphite, acenaphthalene, trans-cinnamaldehyde, maleic anhydride, syn-syn-1,3-dimethyl-π-allyl cation, syn-1-methyl-π-allyl cation, π-allyl cation, and I2. The isomer shift increases and the electric quadrupole splitting decreases regularly through this series. The effect is explained in terms of the extent of forward coordination of the ligands, and so forms a basis for measuring Lewis basicity of ligands. The compound I2:Fe(CO)4 unexpectedly follows the trend, suggesting there remains appreciable bonding between iodine atoms.
Optical Reflection Spectra of Chromia—Alumina
Authors: Poole Charles P. , Itzel John F.
Published: January 2005

The optical reflection spectra from 12 500 to 50 000 cm—1 were studied for a series of coprecipitated chromia—alumina samples calcined between 500° and 1400°C. The Melamed theory was employed to obtain extinction coefficients from these spectra. The Racah parameter B and the wavenumbers of the two visible transitions in ruby (1400°C calcination) arising from Cr3+ gradually decreased with increasing chromia content. The Racah parameter B and the wavenumber Δ of the 4A2→4T2 transition in high chromia content samples calcined at 500°, 750°, and 900°C. were unusually low due to the formation of chromia rich solid solutions. In the oxidized state the samples calcined below 1400°C showed an intense ultraviolet absorption due to Cr6+.
Effect of Isotopic Substitution on the Dipole Moment of Molecules of Symmetrical Configuration
Authors: Gangemi Francis A.
Published: January 2005

As is well known, molecules of symmetrical configuration possess no permanent dipole moment. Upon isotopic substitution, however, a dipole is produced due to the changed zero-point motion of vibration and the asymmetry of the restoring forces.

This effect is calculated for two molecules: O16C12O18, and CH3D.

A normal coordinate treatment is carried out for these two molecules using a simplified form for the force fields as an approximation to the general quadratic force fields of both CO2 and CH3D. It is assumed therefore that the omitted terms play a negligible part in dipole moment calculations. The vibrational wavefunctions for the nuclear skeletons of the systems are calculated, including the effect of the cubic terms in the potential function as perturbations to the simple harmonic wavefunctions. The shift from the equilibrium separation of the atoms is then calculated by taking the quantum mechanical average values of the position coordinates.

Finally, the dipole moment is given by the product Δμ=∂μ/∂r〈Δr〉Av, where ∂μ/∂r is the change in bond moment with respect to internuclear distance which is determined from experiment, and 〈Δr〉Av is the shift or displacement from the equilibrium separation of the nuclei.

The calculations yielded the following results: for O16C12O18, a permanent dipole moment of the order of 10—3 D, and for CH3D, a permanent dipole moment of the order of 10—3 D, for the vibrational ground states.
Analysis of the Optical Absorption Spectrum of Neodymium Magnesium Nitrate
Authors: Tinsley Beatrice M.
Published: January 2005

The optical absorption spectrum and magnetic properties of Nd2 Mg3 (NO3)12·24H2O have been interpreted in the light of crystalline field theory, using intermediate coupling calculations within each level of the free Nd3+ ion. A field of C3v symmetry has been used to account successfully for most of the observed crystal field energy levels and their Zeeman splittings. The possibility of using icosahedral symmetry as an approximation has also been investigated.
Thermoelectric Power of CuCl Containing CdCl2
Authors: Hsueh Y. W. , Christy R. W.
Published: January 2005

The thermoelectric power of CuCl has been measured as a function of temperature between 200° and 400°C, using Cu-metal electrodes. Measurements were made on pure material, and also on material doped with CdCl2 in concentrations between 0.01 and 1.0 mole %. The results for pure CuCl are intermediate between previous results for AgBr and AgCl, and the effect of doping is very similar to that in AgBr. Comparison of the CuCl results with those for the silver halides suggests that in CuCl cation Frenkel defects are predominant, with the Cu+ interstitial more mobile. Quantitative values for the defect parameters could not be derived, apparently because of the limited solubility of CdCl2, but they are probably comparable with the silver halides. Additions of CaCl2, SrCl2, ZnCl2, and PbCl2 gave less informative results; PbCl2 showed what is believed to be an electronic effect at high temperatures. Conductivity measurements were also made on all specimens. The activation energy for pure CuCl was 1.06 eV.
Conditions for First- or Second-Order Kinetics during Multiple Zone Reactions
Authors: Dole Malcolm , Inokuti Mitio
Published: January 2005

The influence on observed reaction rates of isolating the reactants among a number of physically separated zones is considered from the standpoint first of the transition from second- to first-order kinetics as the concentration of reacting species per zone becomes very small (of the order of 10 or less), and second from the standpoint of an initial nonuniform distribution of the reactants in the zones. The case of the numbers of reacting species being limited to even numbers only, as in free radical production and decay, is also treated explicity for a small number of zones. When the number of zones is large and the restriction to even numbers omitted, the over-all observed reaction rate is exactly second order irrespective of the number of reacting species per zone, providing that the concentration distribution follows a multinomial (random) distribution.
Theory of Linewidths in Electron Spin Resonance Spectra
Authors: Freed Jack H. , Fraenkel George K.
Published: January 2005

A general theory of the linewidths in the electron spin resonance spectra of dilute solutions of free radicals has been developed in terms of the relaxation-matrix theory of Bloch, Redfield, and Ayant. In contrast to previous theories, it is shown that a composite line arising from a set of degenerate nuclear-spin states should, in general, consist of a sum of superimposed lines of Lorentzian shape with different widths rather than a single line with an over-all Lorentzian shape. A single Lorentzian line is still obtained, however, as a limiting case when the variation of the widths of the different components of a composite line is small compared to the average width. Although the non-Lorentzian shape of a composite line is often difficult to observe experimentally, a number of other observable properties are predicted by the present development that are outside the scope of the previous theories. For example, linewidth effects resulting from differences in the widths of the separate components of a composite line are predicted that explain the alternation in the linewidths from one hyperfine line to another recently observed in the ESR spectra in certain free radicals. The detailed form of the relaxation matrix is presented for intramolecular anisotropic and isotropic electron—nuclear dipolar interactions, quadrupole interactions, and g-tensor relaxations. Modulations of the spin density and hyperfine splittings are included, as are internal motions, and a number of cross terms between the different relaxation mechanisms arise. In general the relaxation matrix of a composite line contains significant off-diagonal elements, and the determination of the linewidths requires the evaluation of the eigenvalues of the matrix. Problems involving rapid chemical exchange, or modulation by jumps to a small number of sites, can be treated by the relaxation-matrix theory and, under special restrictions, by either the modified Bloch equations or the Anderson theory of motional narrowing. When applicable, these latter procedures can be used over the entire range of exchange rates, while the relaxation-matrix theory is limited to fast rates only.
Gaussian Expansion of Hydrogen-Atom Wavefunctions
Authors: Whitten Jerry L.
Published: January 2005

The 1s, 2s, 2p, and the four equivalent 3d hydrogen-atom wavefunctions were expanded as linear combinations of functions of the form, exp ( —ar2), without the use of spherical harmonic functions to give angular dependence. The Gaussian functions were located at different points in space in order to give the proper orbital symmetry. Expansion parameters were determined by a variational calculation of the hydrogen-atom energy. Energy errors are 0.2, 0.45, 0.25, and 0.9%, respectively, for the 1s, 2s, 2p, and 3d functions.

It is suggested that the approximations are sufficiently accurate to find use in molecular-energy calculations, particularly since integrals involving several centers are more readily evaluated in terms of Gaussian rather than exponential radial functions.
Far-Infrared Spectrum and Barrier to Internal Rotation of Ethyl Fluoride
Authors: Sage Gloria , Klemperer William
Published: January 2005

The far-infrared spectrum of gaseous ethyl fluoride has been remeasured. A series of sharp Q branches have been observed at 242.7, 225.5, 208.4, and 177 cm—1 and have been assigned as the band origins of the 0–1, 1–2, 2–3, and 3–4 Å torsional transitions. The V6 contribution to the potential hindering internal rotation is about —15 cal/mole.
Energy-Transfer Studies by Spectrophotofluorometric Method
Authors: Wilkinson Francis , Dubois Jean T.
Published: January 2005

The transfer of electronic excitation energy from the lowest excited singlet and triplet states of a number of aromatic hydrocarbons and ketones to the lowest excited singlet and triplet state of biacetyl has been studied in hexane and benzene solution at room temperature by the spectrophotofluorometric method. Singlet-state lifetimes for benzene, toluene, diphenyl, and acetone are reported and triplet-state lifetimes for diphenyl, naphthalene, acetophenone, and acetone are also obtained. Useful information concerning the triplet states of other donors is also obtained by comparing the phosphorescence to fluorescence ratio of biacetyl when biacetyl alone is irradiated with the ratio obtained when a mixture of biacetyl and the donor is excited at wavelengths absorbed by the donor.
Virial Coefficients for Square-Well Potentials
Authors: Hauge E. Hiis
Published: January 2005

Part of the fourth virial coefficient, D2(T,λ), is calculated with square-well potential in the region 1≤λ≤2. The location of the singularities in ring integrals as functions of λ is discussed.
Self-Avoiding Walks on the Simple Cubic Lattice
Authors: Sykes M. F.
Published: January 2005

Numerical data on self-avoiding walks on the simple cubic lattice are presented. It is estimated that the number, cn, of such walks of n steps behaves for large n as n1/6μn, where μ=4.68260±0.00025.
Electron Spin Resonance Spectrum of XeF in γ-Irradiated Xenon Tetrafluoride
Authors: Morton J. R. , Falconer W. E.
Published: January 2005

The radical XeF has been detected by means of electron spin resonance in a single crystal of XeF4 γ-irradiated at 77°K. The following hyperfine interaction constants were obtained for magnetic field directions parallel and perpendicular to the Xe–F bond:F∥19=2649 Mc, F⊥19=540 Mc, Xe∥129=2368 Mc, and Xe⊥129=1224 Mc. The unpaired electron occupies a σ orbital, and it was shown from parameters derived from the respective atomic wavefunctions that the orbital is predominantly F 2p and Xe 5p in character. The experimentally determined g values for XeF were g∥=1.9740, g⊥=2.1251. Departures from the free-spin value are interpreted in terms of interaction between the orbital ground state and excited states of the molecule.
Cation Distributions in Nonstoichiometric Magnesium Ferrite
Authors: Mozzi R. L. , Paladino A. E.
Published: January 2005

The temperature dependence of the cation-distribution parameter η, the lattice constant a, and the oxygen-position parameter u, for Mg1.06Fe1.94O3.97 has been established for quench temperatures between 410° and 1100°C. The fraction of magnesium ions on tetrahedral sites, η, increases from 0.12 to 0.28 in this temperature range and follows the formula η(2−y+ny)(1−η)(1−ηy)=exp[−(θ0−θ1η)yT],where the magnesium concentration, y, is 1.06, θ0=1850°K and θ1=4480°K. The lattice constant varies linearly with η from 8.385 Å for the 410° quench to 8.398 Å for the 1100°C quench, and the u parameter is 0.381, independent of quench temperature.
Microwave Spectrum of Normal Propyl Chloride
Authors: Sarachman T. N.
Published: January 2005

The microwave spectrum of gaseous normal propyl chloride reveals the presence of two rotational isomers, the trans and gauche conformations. The ground vibrational state rotational constants found for the more abundant Cl35 species are, for the gauche form, A = 11829.22, B = 3322.58, C = 2853.06 Mc/sec; for the trans form, B = 2379.7, C = 2271.7 Mc/sec. Analysis of quadrupole hyperfine splittings in the spectrum of the gauche form gives the quadrupole coupling constants χaa = —19.41 Mc/sec, η = 2.105, in the principal axis system of the Cl35 species. Satellite spectra rising from excited vibrational states were also observed: in the gauche form, the first and second excited states of the skeletal torsion were assigned, and another satellite is believed to be from the excited methyl torsion; in the trans form, only the first excited state of the skeletal torsion was assigned. From relative intensity measurements, it is concluded that the energy difference between the trans and gauche isomers is 0±0.5 kcal/mole.
Resolution of Exact H2+ Wavefunction on One-Center Hydrogenic Basis
Authors: Boorstein Seth , Goodisman Jerry
Published: January 2005

The ground state of H2+ is treated by a variational procedure, using as basis functions discrete hydrogen-like orbitals located at the midpoint. The variational coefficient for each function is compared to its overlap with the exact function. The effect of using different Z's for the basis sets is studied. When the basis set is not well chosen, the variational coefficients may differ radically from the values determined by the overlaps. The nodal properties of the basis functions, rather than their energies, are emphasized.
Infrared Absorption Intensities in Mixed Crystals of Benzene and Deuterobenzene
Authors: Hollenberg J. Leland , Dows David A.
Published: January 2005

Absolute absorption intensities of the infrared-active fundamentals in dilute crystalline solutions of benzene in deuterated benzene and vice versa have been measured. The intensities are, within experimental error, equal to those measured for the pure crystals.

The spectroscopic resolution was sufficient to show clearly the effects of isotopic dilution on the crystal multiplets.
Electron Spin Resonance Study of Some Organic Photoconductors
Authors: Cho B.-Y. , Nelson R. C. , Brown L. C.
Published: January 2005

In dye photoconductors which have a very high density of traps, such as rhodamine-B and crystal violet, it is possible to build up a density of spins ∼1016/cm3 in strong illumination. The kinetics of rise and decay of these spins can be directly related to those of photoconductivity, and the spins are believed to be associated with trapped conduction electrons. Since the magnitude of the ESR signal is a measure of the number of electrons, the assumptions regarding mobility which have been made to account for the conductive behavior can be tested. In general, the conclusion that the mean or drift mobility has an exponential temperature dependence corresponding to a monoenergetic trap depth has been confirmed. The mean mobility of electrons is estimated to be ∼1× exp (— Et/kT) cm2/V·sec. The previously observed irregularities in the photoconductive behavior of rhodamine-B arise from the existence of a considerable population of unpaired electrons which do not contribute directly to conduction, but interchange with those which do. Some salts of crystal violet which have appreciable semiconductivities were found to have spin densities ∼1017/cm3 in the dark.
Rare-Earth Tungstates and 1:1 Oxytungstates
Authors: Borchardt Hans J.
Published: January 2005

The normal tungstates (R2O3·3WO3) of all rare-earth elements have been prepared as well as the 1:1 oxytungstates (R2O3·WO3) of all except Sc and Ce. Physical properties were studied with particular emphasis on luminescence.
Molecular Relaxation Times from Thermal Transpiration Measurements
Authors: Mason E. A.
Published: January 2005

It is suggested that measurements of the maximum pressure difference across a capillary due to thermal transpiration can be used for the determination of the molecular relaxation time of the gas (usually rotational relaxation). This pressure difference is related to the translational thermal conductivity of the gas, which in turn is affected by the relaxation times. Available experimental data on thermal transpiration are analyzed in this way, and the results compared with other determinations of relaxation times. The results, although scanty, indicate that the method has promise. The greatest asset of the method is its extreme experimental simplicity; the greatest liability is that two approximate theories intervene between the experimental measurements and the calculated relaxation times.
On the Kinetics of Chemisorption
Authors: Coekelbergs R. , Frennet A. , Lienard G. , Resibois P.
Published: January 2005

The kinetics of chemisorption are analyzed by aid of a very simple model. Due account is taken of the role played by geometrical factors (resulting from the finite size of the molecules) whereas both possible modifications of the activation energy with surface coverage and dissociation on the surface are neglected. The physical aspects of the model are discussed. Some exact numerical results as obtained by the Monte Carlo method are given. The mathematical formulation of the problem is made, yielding an approximate kinetic equation where steric effects are taken account of. The possibility is discussed for this model to be generalized in a more complete theory as well as its interest for further studies in the field of elementary heterogeneous catalytic reactions.
Second Virial Coefficient of Polyelectrolytes. III
Authors: Ise Norio , Ander Paul
Published: January 2005

The polymer concentration dependence of the Donnan equilibrium parameter was studied using an interionic interaction theory based on a spherical model for the macro-ions. It was found that the calculated value of the equilibrium parameter generally decreased quite sharply at first with increasing polymer concentration, increased after reaching a minimum, and then decreased again. The macromolecular dimension was assumed to be independent of the polymer concentration. Also, the theoretical value of the parameter varied more sharply with polymer concentration as the concentration of simple electrolyte decreased. The parameter decreased with increasing macro-ion radius and became negative when large values of the radius were assumed.
Influence of Molecular Quadrupole Moments on the Second Virial Coefficient
Authors: Orcutt Ronald H.
Published: January 2005

Viscosities and second virial coefficients of five molecular gases considered cannot be reproduced by a single pair potential function for central forces. Contributions of quadrupole interactions to the second virial coefficient, but not the viscosity, account adequately for the differences over wide ranges of temperature for the following values of molecular quadrupole moments (in units of 10—26 esu): H2, 0.52; N2, 1.90; CO, 2.81; CO2, 4.59; C2H4, 3.92. These are compared with other estimates, and the legitimacy of the assumptions is discussed.
Formal Kinetic Theory of Transport Phenomena in Polyatomic Gas Mixtures
Authors: Monchick L. , Yun K. S. , Mason E. A.
Published: January 2005

A rigorous formal kinetic theory of multicomponent polyatomic gas mixtures is derived. The methods are essentially a combination of those used by Chapman and Enskog for monatomic gases (as extended to multicomponent mixtures by Curtiss and Hirschfelder), and those used by Wang Chang and Uhlenbeck for a single polyatomic gas for the case where the equilibration between internal and translational degrees of freedom is easy. The calculations correspond to the first approximation in the classical Chapman—Enskog theory. Expressions are derived for the coefficients of shear viscosity, volume viscosity (which is proportional to a relaxation time), ordinary diffusion, translational and internal thermal conductivity, and thermal diffusion. Although the results are rather formal, a number of useful conclusions about the effects of inelastic collisions can be drawn without the necessity of detailed calculations. For instance, it is comparatively simple to show that inelastic collisions have very little effect on shear viscosity and ordinary diffusion, but probably seriously affect thermal conductivity and thermal diffusion. The Hirschfelder—Eucken formula for the thermal conductivity of polyatomic gas mixtures appears as a limiting case of the present formulas. A number of other conclusions and implications of the present formulas are also discussed.
Radiationless Triplet—Singlet Transitions in Naphthalene
Authors: Hadley Steven G. , Rast Howard E. , Keller Richard A.
Published: January 2005

The fluorescent intensity, phosphorescent intensity, and phosphorescent lifetime of naphthalene and naphthalene-ds, dissolved in durene, were measured as a function of temperature from 77° to 325°K. These measurements indicate that radiationless transitions from the first excited singlet state are temperature-independent but radiationless transitions from the lowest triplet are strongly temperature-dependent. Analysis of the data for the decay of the triplet state indicates that only one activated state is responsible for this temperature dependence. The activation energy and pre-exponential factor for decay from this state are 3559±79 cm—1 and (4.2±1.5)×107 sec—1 for naphthalene, and 3362±35 cm—1 and (1.30±0.24)×107 sec—1 for naphthalene-ds. These data can be interpreted as corresponding to the excitation of one of the intramolecular CC stretching modes to its second excited state or a combination of two CC fundamentals.
Dissociation of Cl2 in Shock Waves
Authors: Jacobs T. A. , Giedt R. R.
Published: January 2005

The dissociation of Cl2 in Cl2–Ar mixtures was measured in a shock tube over the temperature range 1700° to 2500°K. Direct absorption spectrophotometry was used to follow the course of the reaction. A rate constant given by k=8.90×1013 exp —48 300/RT cm3/mole-sec [or,alternatively,k=3.13×1012(57 080/RT)2.087exp−57 080/RT cm3/mole·sec]was found to fit the measured data over the entire temperature range with a most probably error of ±6%. The activation energy determined agreed exactly with that measured by Hiraoka and Hardwick although the over-all rate constants were a factor of 10 lower than those reported by these investigators. Recombination rate constants, calculated from the measured dissociation rate constants by use of the thermodynamic equilibrium constant, were found to be in good agreement with the theoretical predictions of Benson and Fueno.
Quantum Effects in Liquid Hydrogen
Authors: Bigeleisen Jacob
Published: January 2005

The thermodynamic description of a nonideal two-component solution is developed for the case where the excess free energy of mixing in the liquid has its origin in the volume change on mixing. The equilibrium condition is calculated for the real gas. The equilibrium vapor—liquid distribution is related to the partition functions of the components in the liquid phase and the ideal gas. This relationship affords a basis for the calculation of the partition function ratios HT/H2 and DT/D2 in the liquid phase from experimental data. Partition function ratios of HD/H2, D2/H2, and T2/H2 in the liquid state are derived from vapor-pressure data. It is shown that the method of ordered quantum corrections is an inconvenient one for the description of the quantum effects in liquid hydrogen in its various isotopic forms. ``Lattice'' zero-point energy differences for the isotopic liquid hydrogens are derived from the partition functions under the assumption of free rotation in the liquid. A large asymmetry effect is found for the heteronuclear species HD, HT, and DT. The ``lattice'' zero-point energy of HT is 5.54°K greater than that of D2, which has the same molecular weight. The structural effect of the molecule is shown to be a consequence of quantum mechanical coupling of rotation with the libration of the molecule in the condensed phase. Comparisons are made with two simple models of the coupling, both of which give qualitative agreement with experiment but overemphasize the coupling. A coupling parameter is derived from the experimental data to describe the translation—rotation interaction in an anharmonic potential field. It is shown that the anharmonic correction to the thermodynamic properties of condensed hydrogen is large.
Absorption and Fluorescence Spectra of Several Praseodymium-Doped Crystals and the Change of Covalence in the Chemical Bonds of the Praseodymium Ion
Authors: Wong Eugene Y. , Stafsudd Oscar M. , Johnston David R.
Published: January 2005

The absorption and fluorescence spectra of praseodymium-doped lanthanum trifluoride, lanthanum ethylsulfate, and yttrium aluminum garnet single crystals are reported. The center of gravity of each J level is shifted to the red when the nearest neighbors of the praseodymium ion change in the order of fluorine, water, chlorine, bromine, and oxygen. This corresponds to an increase of covalent character by 0.7, 0.9, 1.1, and 2.0% for Pr–H2O, Pr–Cl, Pr–Br, and Pr–O bonds when compared with Pr–F.
Excitation Mechanism for the Nitrogen Pink Afterglow
Authors: Prag A. B. , Clark K. C.
Published: January 2005

An excitation mechanism is described which can account for the observed features of the fast, so-called pink afterglow of pure nitrogen. Metastable sextet atoms are assumed to participate in the formation of loosely bound N4 molecules, which can release sufficient energy to produce the necessary delayed excitation. An improved method of isoelectronic extrapolation gives an energy of 17.2 eV for the metastable N 3s′′′ 6S0 state and 18.0 eV for the N 3s′′′ 4S0 state. With the assumption of a simple model of N4, the detailed processes of spectroscopic excitation are predicted through collisions involving single-electron exchanges.
Potential Curve for the 2Σu+ State of H2—
Authors: Taylor Howard S. , Harris F. E.
Published: January 2005

The 2Σu+ state of H2— is shown to lie in the continuum of H2X 1Σg+e. This result is contrary to a number of previously reported results.
Electron Transfer in Dilute Gold Alloys
Authors: Barrett P. H. , Grant R. W. , Kaplan Morton , Keller D. A. , Shirley D. A.
Published: January 2005

Isomeric chemical shifts were observed in the Mössbauer spectra of Au197 atoms in dilute solutions in 19 metals and semiconductors at 4.2°K. The shifts were interpreted as arising from transfer of (conduction) electrons in the 6s shell of gold, probably toward the gold atom, in the alloys. A correlation was found between the shifts and the host electronegativities. The relationship between the 6s electron of gold and the nickel d bands in gold—nickel alloys is discussed. It is shown that the ground and first excited nuclear states of Au197 have radial charge moments sufficiently different (the excited state is probably ``larger'') to require collective nuclear excitation. The isomeric shift in Al2Au does not directly confirm the electroneutrality hypothesis for intermetallic compounds.
Vaporization of Tungsten Studied by Flash Heating and Kinetic Spectroscopy. I. Near-Ultraviolet Region
Authors: Nelson L. S. , Kuebler N. A.
Published: January 2005

Thin wires or strips of tungsten have been vaporized by heating with an intense pulse of light from a capacitor discharge lamp. The appearance of the metal as it vaporizes has been recorded by high-speed photography; the characteristics of the vapor were studied at various times by kinetic absorption spectroscopy. When flash heated, tungsten behaves grossly like an electrically exploded metal. Using an approximate spectroscopic method, we have estimated the electronic temperature of the vapor to be near 3000°K as it sublimes from the solid, and near 7000°K as it boils from the liquid. Thermal excitation of nearly 22000 cm—1 occurs under the latter conditions. Production of tungsten ions seems negligible. Some secondary photoexcitation of the atoms to states lying as high as 55000 cm—1 may occur.

Flash heating shows promise as a general method for producing vapors of even the most refractory elements for absorption spectroscopy.
Ion Radicals of Methyl-Substituted Benzenes: Temperature Dependence of Spin and Charge Densities
Authors: Brown Thomas H. , Karplus Martin
Published: January 2005

The spin and charge densities for the monomethyl and dimethyl benzene negative ions are calculated with the valence-bond perturbation procedure developed previously. Because the difference in energy (ΔE) between the two lowest eigenvalues of these systems is found to be small, thermal averaging is included in the determination of the theoretical spin densities. Meta-xylene negative-ion data are used to evaluate the required valence-bond parameters. Comparison of the measured and calculated hyperfine constant values, including the available temperature-dependence data, shows good agreement in most cases. However, a number of discrepancies appear to exist and further investigation is required. The experimental and theoretical difficulties in obtaining good ΔE values are also discussed.

The formulation is used to predict spin densities for some unknown methyl-substituted benzene negative ions and for the methyl-substituted benzene positive ions. Also, values are obtained for the perturbation parameter (ΔCx—) for the other alkyl-substituted benzene negative ions which have been studied experimentally. Some discussion is given concerning the extension of the treatment to systems other than substituted benzene ion-radicals. The reliability of the method is considered, and comparisons are made with available molecule-orbital calculations.
Radiative Lifetime of Triplet Biacetyl
Authors: Dubois Jean T. , Wilkinson Francis
Published: January 2005

Absolute quantum yields of phosphorescence of biacetyl have been obtained in fluid and rigid solutions. In fluid solutions, the measurements were made relative to the quinine bisulfate standard and in rigid media, relative to benzophenone. The values obtained have been taken together with the known triplet-state lifetimes of biacetyl in these media to calculate the radiative lifetime of triplet biacetyl. These results compare favorably with the radiative lifetime of biacetyl triplet in the gas phase, calculated in a similar manner using available data on the phosphorescence yield and the actual mean life in the vapor.
Correlation of Magnetothermodynamic Data with a Theoretical Model. Powdered CoSO4·7H2O over the Range 0 to 100 kG above 1.2°K
Authors: Fisher R. A. , Hornung E. W.
Published: January 2005

Equations for calculating the magnetothermodynamic properties, under varied conditions of field and temperature, are presented and discussed for a model based on a theory of paramagnetism in the solid state. An averaging technique, making use of a digital computer, is derived for use in evaluating the theoretical equations for randomly oriented crystals of paramagnetic material. These equations are applied to the magnetic system of randomly oriented crystals of CoSO4·7H2O. It was shown previously that after subtracting a small temperature independent term from the measured isothermal differential magnetic susceptibility and magnetization, the data followed an H/T function, where H is the magnetic field within the crystals. (The experimental magnetic entropy measurements were made in the liquid-helium range of temperature. Magnetic induction measurements were made in the liquid-helium and liquid-hydrogen temperature ranges, and at the boiling point of liquid nitrogen.) Since CoSO4·7H2O has two different Co++ ions per unit cell, seven parameters are theoretically necessary to fit the experimental magnetothermodynamic data. These parameters are: the ``fictitious'' spin of the ground state of the Co++ ions, S′0, and the principal g values for the gs0′ tensors for each of the two Co++ ions per unit cell. Lacking definitive paramagnetic resonance data for the principal values of the gs0′ tensors, the assumption was used that (1) both Co++ ions per unit cell have the same gs0′ tensor, and (2) two of the principal g values for the gs0′ tensor are equal. Using S′0=½ and deriving the principal g values of g⊥=1.754 and g‖=7.528, all of the measured temperature-dependent magnetothermodynamic properties could be fitted to the solid state model over the H/T range 0 to 60 000 G/deg K, the limit of the measurements, to within the estimated experimental accuracy.
Dissociative Charge Transfer in He+–O2 and He+–N2 Collisions
Authors: Stebbings R. F. , Smith A. C. H. , Ehrhardt Helmut
Published: January 2005

The cross sections for charge transfer between He+ ions and molecules of nitrogen and oxygen have been determined within the energy range 100–7700 eV. A mass spectrometer was used to analyze the secondary ions, and the dissociative and nondissociative charge-transfer cross sections were separately determined. The observations show that in both reactions the major contribution to the total charge-transfer cross section comes from collisions involving dissociation.