bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution to the Theory of Alternant Systems
Authors: Koutecký Jaroslav
Published: January 2005

The definition of an alternant system is given in terms of commutation and anticommutation relations of the Hamiltonian with certain operators. Necessary and sufficient conditions that the Hamiltonian fulfill these relationships are formulated. Different known cases of alternant systems are derived from the definition. Pairing properties are shown to follow as consequences of the definition, and they are summarized in simple general equations for matrix elements of an arbitrary operator.
Ultrasonic Shear and Longitudinal Measurements in Aqueous Glycerol
Authors: Slie W. M. , Donfor A. R. , Litovitz T. A.
Published: January 2005

Glycerol—water mixtures containing up to 68 mole % water were subjected to ultrasonic shear and longitudinal measurements over the temperature range +50° to −120°C. The low-frequency absorption coefficient and the velocity of sound were measured at 25°C for various glycerol—water mixtures from pure glycerol to pure water. The results demonstrate the existence of low- and high-frequency limiting compressional moduli and a high-frequency limiting shear modulus. The relaxational moduli were found to be linear with temperature for each concentration, and also were linearly dependent on water content.

The width of the distribution of relaxation times was found to be independent of water content up to 68 mole %. This result fails to support Frohlich's model for the origin of the distribution of relaxation times.

Estimated values of the relaxation parameters of water were obtained from the data. Those which were obtained by extrapolation appear to be reasonable when compared with theoretically obtained values.
Ground State of Divalent Co Ions in Cs3CoCl5 and Cs3CoBr5
Authors: van Stapele R. P. , Beljers H. G. , Bongers P. F. , Zijlstra H.
Published: January 2005

The 4A2 ground state of tetrahedrally coordinated divalent cobalt ions in Cs3CoCl5 and Cs3CoBr5 is investigated with magnetic-susceptibility measurements and paramagnetic resonance in pulsed magnetic fields up to 90 kOe at frequencies in the 70- and 120-Gc/sec bands. The first excited state (4T2) which lies ∼3000 cm−1 above the ground state is studied optically on Cs3Zn0.9Co0.1Cl5. The sign of the splitting of the 4T2 state is opposite to that expected from the observed negative zero-field splitting of the ground state.
Rigid Disks and Spheres at High Densities: Bounds on the Partition Function
Authors: Salsburg Zevi W.
Published: January 2005

Upper and lower bounds on the partition functions for finite systems of N rigid disks and N rigid spheres are obtained for the high-density limit. The lower bounds are also valid in the thermodynamic limit of N→∞ and at all densities. Consider the following asymptotic form for the specific Helmholtz free energy for a classical mechanical system of N ν-dimensional (ν=2 or 3) hard spheres confined in a volume V in the limit V→V0 (the close-packed volume), AN/NkBT≅νln(Λ/σ)−νln[1−(V0/V)]+Cν(N),where Λ is the de Broglie wavelength and σ the sphere diameter. The lower bounds obtained for Cν(N) are C2(N) > −0.7576··· and C3(N) > −0.05074···. Two upper bounds found for C2 are C2<1.530··· and C2<1.289···. An upper bound for C3 is 3.6423···.
Species and Composition of Dilute Alkali-Metal—Ammonia Solutions
Authors: Golden Sidney , Guttman Charles , Tuttle Thomas R.
Published: January 2005

Dilute solutions of the alkali metals in liquid ammonia are assumed to consist of the following constituents: M+, the solvated metal cation; S, the solvent; M−, the solvated metal anion; S−, the solvent anion (solvated electron); the ion pairs M+·M− and M+·S−. These species are assumed to be in equilibrium via M++2S−⇌M−+2Sand M++A−⇌M+·A−,where A− is either M− or S−. For simplicity, the activity coefficient of each species is assumed to be given by the extended theory of Debye and Hückel, with a fixed value of 5.5 Å for the interionic size parameter; the ion-pairing theory of Fuoss, with the same value for the interionic size parameter, is also assumed. The only adjustable parameter then remaining for a complete characterization of the composition of dilute alkali-metal—ammonia solutions is the redox equilibrium constant.

With generally good results being obtained, the foregoing model has been applied to account for the following properties of alkali-metal—ammonia solutions which are more dilute than about 0.10M: (1) the spin paramagnetic susceptibilities reported by Hutchison and Pastor; (2) the vapor-pressure-depression results of Kraus; (3) the electrical conductances measured by Kraus and the temperature coefficients of conductance, reported by Gibson and Phipps; (4) the Knight shifts for 14N and 23Na, reported by McConnell and Holm, Acrivos and Pitzer, and O'Reilly; (5) the optical-absorption results of Gold and Jolly, and those of Dye and Douthit. An a posteriori argument supports the neglect of ion triples for the solutions which have been considered, and reinforces a distinction to be made bewteen the metal anion Na− and the analogous ion triple S−·Na+·S−.
Measurement of Atomic Concentrations in Discharged Nitrogen, Oxygen, and Hydrogen
Authors: Elias Lorne
Published: January 2005

A relatively simple, absolute method for the determination of atomic densities in low-pressure flow systems is described. The method involves measurement of the pressure loss following recombination when a portion of the dissociated stream is rapidly isolated in a section of the flow line. The atom contents of discharged N2 and O2 were estimated to within 10%, H2 to within 15%. These results were compared with those of some current gas-phase, chemical titration procedures, utilizing as reagents NO for N atoms, NO2 for O, and NO2 for H. The correspondence between reacted titrant:atom density was found to be 1:1 for N and O, and 3:2 for H over a range of pressures and atom concentrations. For the levels of dissociation employed, the 3:2 correspondence for H was not affected by the presence of H2.
Mathematical Analysis of the Thermal Wave Technique for Linear Kinetics
Authors: Sekerka R. F. , Tiller W. A.
Published: January 2005

A precise calculation is made of the temperature distribution in two adjacent phases when the interface position is caused to vary harmonically with time under a thermal driving force. The departure from equilibrium at the interface required for ``uniform advance'' kinetics is included in the analysis. It is found that the interface temperature is exactly 180° out of phase with the freezing velocity and that the amplitude of the interface motion displays dispersion with frequency. The consequences of having phases of different density is evaluated. The analysis is discussed primarily from the viewpoint of solid—liquid interface motion.
Ion—Molecule Reactions by a Photoionization Mass Spectrometer. I. Propylene and 1,3-Butadiene
Authors: Koyano Inosuke , Omura Itiro , Tanaka Ikuzo
Published: January 2005

Ion—molecule reactions in propylene and 1,3-butadiene have been studied using a mass spectrometer which utilizes photoionization as an ion source instead of electron impact. The light source used was a low-pressure hydrogen-discharge lamp with a LiF window (substantially Lyman alpha, 1216 Å). It has been shown that this method has two major advantages in the study of ion—molecule reactions compared with the electron-impact method; one is the lack of unimolecular fragmentation of the parent ion and the other the absence of hot filament, which enables one to get high pressure without suffering pyrolysis.

Five reactions of C3H6+ with C3H6 and eight reactions of C4H6+ with C4H6 have been identified and the cross sections determined for these reactions. In propylene, the reaction leading to the formation of C3H7+ was found to be of the largest cross section and, although cross section was small, the reaction forming C3H3+ was found as a new reaction. It was shown that C3H6+ could not be the precursor of secondary C4H6+ in propylene, criticizing the Fuchs assignment. In 1,3-butadiene, three new reactions have been found; the reaction leading to the formation of C3H3+, the hydrogen-atom abstraction reaction just as in propylene, and the parent-minus-one reaction. The first one was of the largest cross section in all reactions in 1,3-butadiene. This reaction has been discussed in connection with the structure and the heat of formation of C3H3+.
Infrared and Raman Spectrum of Bromocyclopropane between 3200 and 240 cm−1
Authors: Rothschild Walter G.
Published: January 2005

The infrared spectrum of bromocyclopropane vapor and liquid was scanned between 3200 and 240 cm−1. The Raman shifts and their qualitative degrees of polarization were measured only for the liquid. All 21 fundamentals were assigned and an approximate picture of the motions of those atoms which are mainly involved in the fundamental modes is given. Some of the assignments are supported by the shape of observed and computed band contours and by a comparison in a correlation diagram. In spite of near coincidences of the wavenumbers of the carbon—bromine stretching fundamental and the first overtone of the symmetric carbon—bromine deformation mode, no Fermi resonance was apparent. The solvent shifts of the liquid are positive or negligible for fundamentals above 500 cm−1 and are negative for those below that value.
Perturbationlike Theory without φ
Authors: Yaris Robert
Published: January 2005

A perturbationlike expansion is derived for the (usual) case when the available starting wavefunction is not an eigenfunction of the unperturbed Hamiltonian. It is shown that the resulting expression satisfies a Hylleras variational condition.
On the Exponential Form of Time-Displacement Operators in Quantum Mechanics
Authors: Pechukas Philip , Light John C.
Published: January 2005

We derive and discuss a formula, due to Magnus, for the exponential representation of the operator solution to Schrödinger's equation when the Hamiltonian is time dependent. The formula gives a unitary time-displacement operator in every order of approximation. We study the usefulness of the first- and second-order approximations for the kind of problem posed by the semiclassical theory of inelastic collisions, basing our discussion on two exactly soluble two-state problems. The algebraic structure of the Magnus formula is in itself useful; to illustrate this, we solve exactly the problems of the linearly forced harmonic oscillator and the harmonic oscillator with time-dependent force constant.
Proton Resonance Study of Molecular Motion and Phase Behavior of Solid H2S and H2Se
Authors: Loehlin J. H. , Mennitt P. G. , Waugh J. S.
Published: January 2005

Measurements of longitudinal and transverse proton relaxation in the three solid phases of H2S and H2Se are reported. In the lowest temperature phase it appears that the molecules execute order-preserving 180° flips about their C2 axes. In the intermediate phase there are, in addition, molecular reorientations through other angles and about axes other than C2. Over much of the high-temperature phase the relaxation rates are dominated by translational self-diffusion. The lower transition in H2Se, which is gradual in nature, is unusual in that it is accompanied by a cooperative lowering of the barriers to three-dimensional reorientation through the region which is associated with a linewidth transition.
Electron-Impact Ionization Cross Sections for Atoms
Authors: Cooper John L. , Pressley George A. , Stafford Fred E.
Published: January 2005

The relative cross sections for electron-impact ionization of Fe, Co, Ni, and Ag have been measured using a crossed-beam technique with mass-spectrometric analysis of the ions. For 60-eV electrons, the relative cross sections for single ionization are 34, 39, 33, and 35, respectively.

The available absolute and relative cross-section data show singificant deviations from the correlations proposed by Otvos and Stevenson and by Lampe, Franklin, and Field.
Exciton Analog of the Peierls Instability of One-Dimensional Metals
Authors: Merrifield R. E.
Published: January 2005

A one-dimensional metal in which the conduction electrons interact with excitons in an array of polarizable side groups is shown to possess an inherent instability analogous to the phonon-induced Peierls instability. The instability manifests itself by the simultaneous appearance of an energy gap at the center of the conduction band and a ferroelectric polarization of the side groups. An approximate quantitative treatment of this effect is presented. The principal conclusions are: (1) the system is unstable for all values of the electron—exciton coupling constant, (2) the resulting semiconducting gap is at least as large as the BCS superconducting gap for the same system, and (3) while it cannot be said with certainty that this precludes superconductivity in such a system it suggests that if it does not become superconducting it will become ferroelectric.
Mass-Spectrometric Investigation of the Reactions of Atomic Hydrogen with Acetylene
Authors: Volpi G. G. , Zocchi F.
Published: January 2005

The reactions of hydrogen atoms with acetylene have been investigated in a flow system, using a mass spectrometer for the determination of the concentrations of the stable and of the transient species. The disappearance of atomic hydrogen can be described by the mechanism H+C2H2=C2H3*,  k1=2.4×1010 cc mole−1·sec−1,C2H3*=C2H2+H,C2H3*+M=C2H3+M,k2/k3=2.6×10−8 mole cc−1(M=H2),C2H3+H=C2H2+H2,k4≥1012 cc mole−1·sec−1,C2H3+H2=products,k5≤2×10−4 k4.All values of the rate constants refer to a temperature of about 40°C.
Metastable-Ion Peak Shapes in Dempster-Type Mass Spectrometers
Authors: Newton Amos S.
Published: January 2005

The shape and position on the mass scale of the metastable peak at M*/q=31.88 in the mass spectrum of n-C4H10 has been calculated and compared with the observed peak. The calculation was made on the assumption that the ion beamwidth, determined by the beamwidth of normal ions at the collector slit, was widened by velocity components added to the fragments from kinetic energy released in the fragmentation process. The only adjustable parameter used was the total kinetic-energy release in the fragmentation, T. A value of T=0.015±0.005 eV gave the best fit of the observed peaks to the computed peaks. This value is compared with the literature values of T determined by different methods for this metastable dissociation.
Nuclear Quadrupole Coupling Constants and the Ionic Character of Covalent Bonds
Authors: Considine William J.
Published: January 2005

A correlation between the nuclear quadrupole coupling constant for the halogens in some halomethanes and Jaffe's group orbital electronegativity is presented. Since the calculation of group electronegativity does not allow variations in the hybridization of the atoms in the group, it is apparent that the change in coupling constant is due, not to changing s character of the carbon, but rather to changes in ionic character of the bonds involving the halogens.
Analytical Wavefunctions of 2D States of Lithium Isoelectronic Sequence
Authors: Cook D. B. , Ali M. A.
Published: January 2005

Analytical wavefunctions for the first three 2D states of lithium isoelectronic atomic sequence have been obtained using a split-shell core function plus a generalized orbital form for the outer electron. Values of ionization potentials for the outer electron in the three 2D states have been calculated by the ``frozen-core'' approximation, and these compare very well with experimental results. The use of an extended wavefunction for the lowest 2D state obtained by superposing (2p)2 1S function on the split-shell function for the core leads to energy values within 0.01 a.u. of experimental values.
Decomposition of Ozone by O(1D)
Authors: Snelling David R. , Baiamonte Vernon D. , Bair Edward J.
Published: January 2005

Photometric measurements of ozone decomposition following flash photolysis of O3—inert-gas mixtures are interpreted in terms of the time-dependent quantum yield. Decomposition occurs in time segments which contribute increments to the quantum yield that depend on temperature, pressure, and sample composition. A major portion of the reaction O(1D)+O3→2O2,  k≥2.3×109liter/mole·secis complete during the photolysis flash and has no temperature dependence in the range 205°—298°K. Processes which further enhance the quantum yield are much slower and depend on temperature, inert-gas pressure, and composition in a way that has some correlation with the effectiveness of the gas in deactivating vibrationally excited O2†. In N2 a factor of 2 less O3 is decomposed by the end of a flash than in He or Ar, indicating deactivation of the O(1D) by N2. The quantum yield is smaller in N2 than in He or Ar but qualitatively similar in its pressure dependence. Some limitations in accounting for the results by an energy chain mechanism are discussed.
Transfer of N2 Vibrational Energy to Potassium
Authors: Starr Walter L. , Shaw Thomas M.
Published: January 2005

The transfer of vibrational energy from N2 to electronic energy of potassium has been demonstrated experimentally. Vibrationally excited nitrogen N2‡ was obtained from the afterglow of a microwave disin N2. Potassium vapor was admitted to the afterglow and 23 potassium emission lines between 3447 and 7699 Å were observed in the region of the potassium inlet. The N2‡ was deactivated by adding either N2O or CO2 to the afterglow. From measurements of potassium emission intensity and N2O or CO2 flow rates the rate constants for the deactivation of N2‡ by N2O and CO2 were found to be (1.4±0.2)×10−13 and (8.0±0.9)×10−14 cm3 molecule−1·sec−1, respectively. Ionization was observed downstream from the potassium inlet when N2‡ was present. Arguments are presented which eliminate all afterglow constituents other than N2‡ as sources of potassium excitation.
Far-Infrared Spectra of Crystalline Acetylenes C2H2 and C2D2
Authors: Anderson A. , Smith Wm. Hayden
Published: January 2005

The far-infrared spectra of polycrystalline films of acetylene and fully deuterated acetylene have been recorded at 77°K, using a commercial Michelson interferometer. Two sharp bands are observed for each crystal, and the frequency change on deuteration leads to their assignment as translational lattice modes. From these and other spectroscopic results, deductions concerning the crystal structure, which has not been directly measured at this temperature, are made, and it is concluded that the most likely factor group is of D2h symmetry with two molecules per unit cell on C2h sites, a structure similar to those of crystalline carbon disulfide and the halogens.
Electron Spin Resonance of Parabenzosemiquinone-17O
Authors: Silver Brian L. , Luz Z. , Eden C.
Published: January 2005

The electron spin resonance spectrum of 17O labeled parabenzosemiquinone in aqueous ethanol solutions has been examined. The hyperfine splitting constant due to 17O, a0, was 9.02±0.02 G. The splitting constant has the same sign as Δg, the anisotropy of the g tensor, and since Δg is negative, the sign of a0 is also negative. Taking into account the fact that 17O has a negative gyromagnetic ratio, the sign found for a0 implies that the net spin polarization at the 17O nucleus is the same as that in the radical.

Marked variations in linewidth occur between the different components of the 17O hyperfine structure due to modulation through molecular tumbling of the anisotropic dipolar and g-tensor interactions. These variations are quantitatively accounted for by the general theory of ESR linewidths due to Freed and Fraenkel. Analysis of the spectrum gives | Δg | = 0.0029, and a correlation time for the tumbling of the molecule of 9.4×10−11 sec.
Interpretation of NMR Spectra. I. A2BXx and A2BKk Spectra
Authors: Hirst Robert C. , Grant David M. , Paul Edward G.
Published: January 2005

Difficulties encountered in analyzing NMR spectra are greatly multiplied as the number of interacting nuclei increases. The concept of effective internal chemical shifts or effective Larmor frequencies is developed here to simplify the study of complex NMR spectra in which a group of magnetically equivalent nuclei (Xx) is greatly shifted from a strongly coupled group. This concept permits decomposition of a complex NMR spectrum into two or more simpler groups of transitions called subspectra. These subspectra are then analyzed by previously developed methods. It is proved that this decomposition is independent of the nature of the strongly coupled group.

A discussion is given of the change in appearance of spectra as the shift of the Xx group from the strongly coupled group is decreased and small deviations from the ``X'' approximation appear. The Xx group is relabeled Kk (x=k) when such deviations appear. The form of this breakdown depends only on x (or k) and is given for general x (or k). Explicit expressions for the A2BXx system are tabulated. Detailed analyses are presented for the following series of A2BXx or A2BKk spectra: 2,6-dichlorofluorobenzene (A2BX); 1-chloro−2,3-butadiene (A2BX2 or A2BK2); methylallene (A2BX3 or A2BK3).
Decomposition of Tropylium and Substituted Tropylium Ions
Authors: Jennings K. R. , Futrell J. H.
Published: January 2005

Metastable transitions arising from the decomposition of tropylium ions have been investigated in a double-focusing mass spectrometer. It has been shown that the loss of an acetylene molecule is the only major decomposition process, and metastable peaks in the mass spectrum of toluene-α-d3 have been interpreted in terms of this. The relative intensities of the metastable peak and the normal peak at m/e=65 in the mass spectra of several compounds have been shown to correlate with the apparent heat of formation of the C7H7+ ion. Metastable transitions in the mass spectra of several halogenated and alkylated toluene and benzyl compounds have been interpreted in terms of the decomposition of substituted tropylium ions by the elimination of C2H2 or C2HX (X = F, Cl, Br). No evidence could be found for the existence of a pseudotropylium ion in which a CH group is replaced by a N atom in the mass spectra of alkyl pyridines.
Thermal Quenching of Cr(III) Luminescence
Authors: Targos William , Forster Leslie S.
Published: January 2005

The luminescences of chromium acetylacetonate and the nitro- and haloderivatives dissolved in three different isomorphous crystalline hosts have been studied as a function of temperature. The lifetimes and relative quantum yields were determined and evidence for two thermally activated nonradiative processes has been obtained. The activation energies and frequency factors are E1<1 kcal/mole, s1≃103 sec−1 and E2≃7 kcal/mole, s2≃1012 sec−1. This latter value is very large for a spin-forbidden process. The lattice appears to affect nonradiative processes originating in the 4T2 more than those involving the 2E state.
Effect of High Pressure on the Compressibilities of Five Alloys
Authors: Clendenen R. L. , Drickamer H. G.
Published: January 2005

The effect of high pressure has been measured on a series of alloys, including Fe plus 8 at. % Si, which has a (disordered) bcc structure, Fe3Al and Fe3Si, which have an ordered bcc structure, and FeAl and AgMg, which have the CsCl structure. The compressibilities of all the alloys except Fe3Si decrease with increasing pressure and lie between those of the pure components. For Fe3Si the compressibility increases slightly with increasing pressure and is less than that either of pure iron or pure silicon.
Sign of the 17O Hyperfine Coupling Constant in Fremy's Salt
Authors: Luz Z. , Silver Brian L. , Eden C.
Published: January 2005

The electron spin resonance spectrum of Fremy's salt—17O, [(SO3)2N17O]K2—has been studied in aqueous solution. Twelve out of the expected 18 17O satellites were clearly resolved. The measured hyperfine coupling constant for 17O, aO, is 20.7±0.2 G. Variations in linewidth between the 17O satellites were observed and interpreted quantitatively in terms of relaxation by modulation of the anisotropic dipolar and g tensors. The relaxation rate is mainly determined by interactions involving the magnetic moment of 17O. The terms in the expression for the linewidth that depend on mN are small, except for a cross term EmNmO. Analysis of the results combined with a knowledge of the sign of the g-tensor anisotropy allowed the determination of the signs of aN and aO, which are positive and negative, respectively.
Effusion from Spherical Orifices. I. Transmission by Molecular Flow
Authors: Edwards Jimmie G. , Gilles Paul W.
Published: January 2005

Molecular flow through orifices which are spherical segments is treated by a method analogous to that which previously has been applied to cylindrical and conical orifices. The integral equation which expresses the rate at which molecules impinge on a unit area is shown to possess a simple, closed-form solution for spherical orifices, and the transmission probability for such orifices is derived in closed form. Transmission probabilities are presented for several spherical orifices and are shown to be always larger than those for conical or cylindrical orifices of the same dimensions. For very short and very long divergent spherical orifices the transmission probability approaches unity, and at intermediate lengths it passes through a minimum. For very short spherical orifices with equal and parallel plane entrance and exit, the transmission probability approaches unity, and it decreases to a limiting value of one-half for very great length.
Laser-Induced Luminescence and Dissociation in Biphenyl
Authors: Eisenthal K. B. , Peticolas W. L. , Rieckhoff K. E.
Published: January 2005

The interaction of the radiation field of an unfocused ruby laser with molecules containing a phenyl—phenyl or benzyl—benzyl single bond is found to give rise to a new luminescence. This luminescence is linearly dependent on the molecular concentration and proportional to either the second or the third power of the laser intensity. Thus it appears that a multiphoton absorption is occurring. The absorption does not appear to involve the electronic states of the molecules. This luminescence occurs throughout the visible region and bears no resemblance whatever to either the normal fluorescence or phosphorescence. Because of the exceedingly high laser intensities or electric fields necessary for electronic dielectric breakdown it appears that this mechanism is not of importance. It is suggested that multiphoton vibrational excitation to a dissociative state of the molecule may occur which leads to molecular fragmentation. This process is followed by a chemiluminescent emission. A quantitative comparison of the experimental results with a theoretical treatment of multiphoton vibrational dissociation is made.
Measurement of the Relative Abundances and Recoil-Energy Spectra of Fragment Ions Produced as the Initial Consequences of X-Ray Interaction with CH3I, HI, and DI
Authors: Carlson Thomas A. , White R. Milford
Published: January 2005

Methyl iodide, hydrogen iodide, and deuterium iodide have been irradiated with x rays, whose energies are such that the most probable event is the formation of a vacancy in the L shell of iodine. The readjustment to this vacancy, principally by a series of Auger processes, gives rise to extensive ionization and decomposition; and the relative abundances of the fragment ions and their recoil-energy spectra have been measured with a specially designed mass spectrometer. As the result of the inner-shell vacancy, CH3I decomposed primarily into hydrogen, carbon, and iodine ions, having, respectively, the average charges of 1+, 2+, and 5+. Very few molecular ions were observed. The recoil energies were quite large with values in some cases above 100 eV. A calculation, based on a simple model for a Coulombic ``explosion,'' is shown to be consistent with the data. In the studies made with HI and DI the recoil spectra of H+ and D+ are compared with calculations of the kinetic energies expected from multiple ionization. From this comparison there appears to be evidence that the multiply charged molecular ions separate slightly during the time the Auger processes are taking place. Finally, a brief discussion is given concerning the importance of the initial consequence of x-ray interaction in radiation damage.
Phase Diagrams of Sodium Tungstate and Sodium Molybdate to 45 kbar
Authors: Pistorius Carl W. F. T.
Published: January 2005

The phase diagrams of Na2WO4 and Na2MoO4 have been determined to 40–45 kbar. Two new high-pressure phases have been found for Na2WO4. The 440°C transition in Na2MoO4 consists of two transitions very close together. A further new high-pressure phase has been found. Crystallographic data are given for Na2WO4 I and Na2MoO4 III, both of which are orthorhombic, Space Group Pnam. The phase diagrams of Na2WO4 and Na2MoO4 are strikingly similar, and there are reasons for believing that every known polymorph of Na2WO4 has an isostructural counterpart in the phase diagram of Na2MoO4.
Hydrodynamic Properties of Flexible-Ring Macromolecules
Authors: Fukatsu Masaaki , Kurata Michio
Published: January 2005

The sedimentation constant of a series of multiple-ring macromolecules has been calculated by the method of Kirkwood. The multiple-ring form consists of m subrings of equal size linearly connected by universal joints. In the limit of large intersegmental hydrodynamic interaction, the ratio of the sedimentation constant of a multiple-ring molecule to that of a linear chain of the same molecular weight is 1.18 for m=1, 1.32 for m=2, 1.40 for m=3, ··· and 2.00 for extremely large m. These values are found to be practically independent of the excluded volume effect.

The intrinsic viscosity of a single-ring macromolecule has also been calculated by the method of Zimm. The eigenvalue problem encountered in the Zimm theory can be solved exactly over the whole range of the hydrodynamic interaction parameter, h=0 to ∞. The ratio of intrinsic viscosities of ring and linear molecules is 0.500 for h=0 (free-draining case) and 0.645 for h= ∞ (non free-draining case). The latter value is slightly modified if the hydrodynamic interaction is treated by the Fixman method.
Thermodynamic and Conformational Properties of Polystyrene. I. Light-Scattering Studies on Dilute Solutions of Linear Polystyrenes
Authors: Berry G. C.
Published: January 2005

The results of an extensive study of some dilute solution properties of a series of linear, homogeneous (anionically prepared) polystyrenes (4.8<10−4M<440) over a wide temperature interval (10°<T<110°C) in decalin and toluene are described. The data are used to obtain detailed comparisons among the second virial coefficient A2, the mean-square molecular radius 〈s2〉, the molecular weight M, and the temperature. The empirical correlations thus obtained are compared to theoretical predictions. In particular, it is found that A2M½(〈s2〉/M)0−32 and α2=〈s2〉/〈s2〉0 are each single-valued functions of the interaction parameter z=B(〈s2〉0/M)0−32M½, when B is assumed to have the temperature dependence B=B0[1—(Θ/T)]. Certain theoretical predictions for the dependence of A2M½/α3 on z/α3 are found to adequately describe the form of the observed behavior and can be used as the basis for a satisfactory empirical relation. The observed dependence of α2 on z is satisfactorily predicted by recent calculations of Flory and Fisk. It is expected that the correlations given among A2, α2, and z will be valid for any flexible, nonionic polymer.
Hauffe—Ilschner Transition during Thermal Oxidation
Authors: Fromhold A. T. , Cook Earl L.
Published: January 2005

Numerical computations together with physical considerations are used to argue that a transition proposed by Hauffe and Ilschner from electron tunneling to nonlinear ionic diffusion as rate-limiting mechanisms during thermal oxidation is not to be expected. The results indicate instead that the reverse transition is likely to occur. This in turn has serious implications regarding the oxidation kinetics and limiting thicknesses as a function of temperature deduced from the Mott—Cabrera theory.
Estimation of the Hydrodynamic Interaction Parameter in Dilute Polymer Solutions from the Extinction Angle in Steady-Flow Birefringence
Authors: Tschoegl N. W.
Published: January 2005

The theory of Zimm is shown to predict that χ0, the extinction angle in steady-flow birefringence of dilute polymer solutions, is a function of Je, the steady-state compliance of the polymer, and of (η—ηs), the contribution of the polymer to the steady-state viscosity of the solution. From the same theory, Je may be calculated as a function of the hydrodynamic interaction parameter h. In good solvents Je also depends on ε, the parameter which accounts for the expansion of the coil due to excluded volume effects. Values of Je(h, ε) as a function of h have been calculated for several values of ε and are presented in tabular and graphical form. These values, along with the equations presented, afford the possibility to estimate h from (η—ηs) combined with measurements of the extinction angle χ0.
Dielectric and Viscous Behavior in the i-Amyl Bromide−2-Methylpentane System
Authors: Denney D. J. , Ring J. W.
Published: January 2005

Equilibrium and dynamic dielectric and viscous-flow behavior in the i-amyl bromide−2-methylpentane system has been studied at five concentrations down to 7.7 mole % bromide (the equilibrium studies extend to more dilute solutions). Dielectric relaxation has been examined in the frequency range from 50 cps to 300 kc/sec and viscous flow in the range 102 to 107 P, the appropriate temperature ranges being practically coincident. Equilibrium dielectric constants have been measured from room temperature down to 122°K.

The equilibrium dielectric constants reveal no significant short-range correlations tending to preferentially align the dipoles. In the relaxation studies, only a single dispersion region appears at all concentrations. It is asymmetric and, except for the pure halide, not representable by any simple known dispersion function. It is qualitatively similar to the high-frequency dispersion in the 1-propanol−2-methylpentane system. The distribution width shows a maximum at some intermediate concentration which suggests that environmental heterogeneity is important but this hypothesis does not seem tenable in the light of other evidence.

The similarity in concentration and temperature dependences of dielectric relaxation and shear viscosity supports the idea that a large molecular region is involved in the relaxation process so that individual molecular interactions tend to be averaged.
Resonances in Electron Scattering from H2, HD, and D2
Authors: Kuyatt C. E. , Simpson J. Arol , Mielczarek S. R.
Published: January 2005

Resonances in the transmission of electrons through H2, HD, and D2 have been studied for electrons of energy 11 to 13 eV. In H2 and HD pairs of resonances were observed, indicating that there exist two electronic states of H2− and HD−, each with well-developed vibrational structure. In D2 only one series of resonances is observed. The single series is attributed to the overlap of two states of D2− because of a smaller vibrational separation. The absolute energy scale for the resonances has been recalibrated to an estimated accuracy of 0.1 eV.
Quantum Dynamics of Anharmonic Oscillators. I. Simple Examples
Authors: Alterman Elliott B. , Tahk Charlotte T. , Wilson David J.
Published: January 2005

The dynamical behavior of two anharmonic oscillators, having a linear and a square-well potential, respectively, is studied. The expectation values of the coordinate and the mean spread of the oscillating wave packets are calculated as functions of time and presented graphically. Significant departures from the behavior of the corresponding classical systems are observed. These results cast some doubt on the use of classical-mechanical models in the theory of unimolecular rates.
Vibrational Levels of the 2D—E State of Ce3+ in CaF2
Authors: Struck Charles W. , Herzfeld Fred
Published: January 2005

The equations for the Jahn—Teller problem of an E electronic state and an E vibrational mode are solved by a numerical technique analogous to the procedure for finding solutions for a lower-order eigenvalue equation.

The vibrational fine structure in the spectrum of CaF2:Ce3+ at 3100 Å is compared with the structure which a first-order Jahn—Teller effect would predict. A stabilization energy of about 330 cm−1 and a E mode vibrational frequency of about 210 cm−1 are indicated.
Theoretical Estimation of the Conductivity of Different Periodic DNA Models
Authors: Ladik J. , Biczó G. , Elek G.
Published: January 2005

Using the deformation-potential approximation, we have estimated the conductivity of some periodic DNA models. The necessary band structures we had determined previously using the tight-binding approximation. We have obtained separately the contributions to the conductivity of the mobile electrons and the positive holes.

For the total conductivities (σ0) we have obtained values between 103−105Ω−1·cm−1. In the cases when the conduction bands are rather narrow we have obtained much larger values for the electronic contribution than for the contribution of the positive holes. This discrepancy can be interpreted within the framework of the deformation potential approximation, but it makes questionable the applicability of this method for narrow bands.
Repulsive Interactions and Molecular Rotation in Inert-Gas Lattices
Authors: Armstrong R. L.
Published: January 2005

A model is discussed from which the effect of repulsive interactions on the rotational energy levels of a solute molecule in an inert-gas lattice may be calculated. The model is based on the assumption that repulsive interactions may be understood in terms of single interatomic-exchange processes in the solid. Application is made to the case of HCl in argon, krypton, and xenon. The results show that, for this case, repulsive interactions are small compared to long-range multipole interactions.
Optical Spectra of Thallium in Glasses as Related to Crystals and Solutions
Authors: Ghosh Amal K.
Published: January 2005

The absorption and emission spectra of thallium in fused silica, aluminoborate, and phosphate glasses are similar to those of thallium-doped alkali halides and solutions. The absorption and emission bands in the different systems can be attributed to transitions within the central Tl+ ion in a center with a (TlXn)(n−1)— configuration, where X stands for the anions neighboring the Tl+ ion. There is a shift in the absorption bands with the nature of the anions and cations neighboring the Tl+ ion. This shift may be related to the chemical shift observed in NMR studies. The thallium centers in glass are possibly present in ordered regions in the glass structure. The minimum size of such an ordered region is estimated to be about 15 Å. There are indications of dimers being formed in thallium-doped fused silica.
Color Centers in Aluminoborate Glass
Authors: Ghosh Amal K.
Published: January 2005

Different types of color centers are present in aluminoborate glass. Some of these are related to impurities, others are possibly due to defects in the glass structure. Radiation induced bands at 520 and 340 mμ are attributed to hole centers. The Fe3+ and Pb2+ ions present as impurities in a normal melt of aluminoborate glass act as electron traps, while Fe2+ ions and Pb0 (atoms) present in a reduced glass act as hole traps. The reduction of Fe3+ ions to Fe2+ ions results in decrease of uv absorption around 220 mμ. On heating the irradiated glass thermoluminescence along with bleaching of color centers were observed and the relation between the two processes was investigated. Glow peaks were observed at 60°±5°C, 165°±10°C, and 210°±5°C. The high-temperature glow peak is observed only at high gamma-ray exposures (∼107 R).
Application of the Hellmann—Feynman and Virial Theorems to the Theoretical Calculation of Molecular Potential Constants
Authors: Schwendeman R. H.
Published: January 2005

The Hellmann—Feynman-theorem expression for the z component of the force on a single nucleus is differentiated successively to obtain expressions which are related to the harmonic and anharmonic potential constants in a molecule. The method used to simplify the differentiations is also used to derive two expressions for the field-gradient part of the nuclear-quadrupole coupling constant; the two expressions involve only convergent integrals. The virial-theorem expression for diatomic molecules is differentiated to obtain equations for the cubic and quartic potential constants and for the Dunham constants a1 and a2. Application of the equations to quantum-chemical calculation of the potential constants is discussed.
Double-Perturbation Treatment of the Ground State of the Hydrogen Molecule
Authors: Liu Bowen , Lyon William D. , Brown W. Byers
Published: January 2005

The ground state of the hydrogen molecule is treated by a double-perturbation theory through second order. The unperturbed system is defined mathematically by the unperturbed spatial wavefunction, which has the form exp[—s(ra1+rb1+ra2+rb2)] where s is an energy-optimized scale parameter. The perturbations are (a) one-electron terms due to the simple form chosen for the zeroth-order wavefunction, and (b) the two-electron repulsion potential. The first-order wavefunction for (a) is known analytically and that for (b) is obtained approximately from the Hylleraas variational principle using a James—Coolidge type trial function.

The energy through second order gives an equilibrium distance within 1% of that obtained by Kol/os and Roothaan and a dissociation energy of 4.988 eV, 5% larger than their value of 4.747 eV. The wavefunction through first order gives expectation values for one-electron operators in good agreement with accurate calculations, but is poor when the electrons are close together.
Preparation and Low-Temperature Magnetic Properties of the Terbium Oxides
Authors: MacChesney J. B. , Williams H. J. , Sherwood R. C. , Potter J. F.
Published: January 2005

The magnetic properties of terbium oxide phases (Tb2O3 cubic and monoclinic polymorphs, TbO1.715, TbO1.809, TbO1.823, and TbO2) have been measured between 1.4° and 300°K. With the exception of TbO1.809, each of these phases is observed to order magnetically at low temperatures. The ordering is predominantly antiferromagnetic, several of the lower oxide phases show metamagnetic behavior, wherein the observed moment has a nonlinear dependence upon the applied field at fields above a critical value, approximately 2000 Oe. The phase TbO1.023 exhibits a tendency toward ferrimagnetic alignment as evidenced by remanent magnetization at 1.4°K. TbO2 is antiferromagnetic with a Néel temperature of 3°K. At higher temperatures, in the paramagnetic region all of the oxide phases give effective Bohr magneton numbers close to the expected values for the free ions.
Rice—Allnatt Assumption in the Low-Density Limit
Authors: Harris S.
Published: January 2005

The Boltzmann collision term for a system of particles which interact through a potential composed of a hard repulsive potential plus a soft attractive potential is expanded in the small parameter which characterizes the soft potential. If the hard and soft forces do not overlap, it is shown, in agreement with the Rice—Allnatt assumption, that in lowest significant order no cross terms containing the hard and soft potentials appear in the collision term.
Shape of a Self-Avoiding Walk or Polymer Chain
Authors: Fisher Michael E.
Published: January 2005

If pn(r) is the probability density of self-avoiding walks of m steps which reach the point r it is proved rigorously that the generating function P(θ,r)= ∑ n=1∞pn(r)exp(−nθ)decays exponentially with r. This result is used to derive restrictions on the form of the distribution pn(r). In particular it is argued that if, for large n the distribution in d dimensions approaches a limiting shape, Rn−dF(r/Rn), where the scaling length Rn, which measures the mean end-to-end distance, varies as r0nv, then the shape factor has the form F(y)=A(y)exp(−yδ),where δ=1/(1—v) and where A(y) does not vary exponentially fast for large y. Accepting the values v2=¾ and v3=⅗ for d=2 and 3, as suggested originally by Flory and since supported by numerical and theoretical calculations, yields δ2=4 and δ3=2½ so that F(y) has the form conjectured recently by Domb et al. on the basis of the numerical analysis of finite lattice chains.
Fluorescence Spectra of Several Aromatic Crystals under High Pressures
Authors: Offen H. W.
Published: January 2005

The fluorescence spectra of crystalline chrysene, 1,2-benzanthracene, anthracene, and four derivatives of anthracene were surveyed in the 0–25-kbar pressure range. In addition to stronger reabsorption of the crystal fluorescence upon compression, a pressure exceeding 10 kbar results in significant modifications of the spectrum. Diffuse bands at longer wavelengths appear at the higher pressures and may be attributed to a reorientation of the molecules in the lattice and the creation of many defects, which favors excimer interaction. The effect is largest for anthracene, where the initial intensity distribution at 1 atm generally does not return after high pressures have been applied. The results appear to depend significantly upon the crystal size and preparation.
Infrared Study of Hydrogen Bonding between Polymers and Methanol: Polypropylene Oxide and Polypropylene Glycol
Authors: Heil J. F. , Prausnitz J. M.
Published: January 2005

Infrared spectra have been measured in the 3600-cm−1 region for two hydrogen-bonding systems containing polymeric proton acceptors in carbon tetrachloride solution. Methanol was the proton donor in both systems. Proton acceptors were polypropylene oxide of molecular weight 450 and 1000, and polypropylene glycol of molecular weight 1025 and 2025. Equilibrium constants were obtained at 10° intervals from 20° to 60°C. The enthalpies of hydrogen-bond formation were −4.0±0.7, −4.7±0.8, −4.1±0.5, and −4.5±0.5 kcal/g-mole. Equilibrium constants for hydrogen bonding between methanol and polypropylene glycol are markedly larger than those observed for polypropylene oxide of comparable molecular weight. This disparity, however, decreases with increasing polyglycol molecular weight, i.e., with decreasing ratio of glycol—hydroxyl to ether—oxygen groups.
Fundamental Vibrations and Force Constants in the Partially Deuterated Methyl Halides
Authors: Riter J. R. , Eggers D. F.
Published: January 2005

Gas-phase infrared spectra of all eight partially deuterated methyl halides have been obtained; samples were of high isotopic purity. Molecular asymmetry, though quite small, was found to yield significant shifts in the perpendicular structure for the two central Q branches. This was most helpful in the choice of band centers. Observed bands were assigned, including the 72 fundamentals and also 35 overtones and combinations. Although most earlier work was done with samples containing two or more isotopic species, agreement with the present results is quite good in many cases. Evidence for Fermi resonance was found, including two examples in which it occurred below 2000 cm−1. Coriolis coupling between fundamentals was detected in several cases for the fluorides, including a strong resonance between a perpendicular and a parallel vibration. Application of the product and sum rules yielded satisfactory agreement. In a few cases substitution of a heavier atom, such as deuterium for hydrogen, was found to result in an increase for one of the vibration frequencies. However, all such instances involved perpendicular bands in which the choice of origin was quite difficult, and the increases were rather small. Anharmonicity corrections for the partially deuterated fundamentals were computed with the aid of a simple expression, using the corrections employed by others for the C3v molecules. The fundamentals investigated here were compared with values calculated from three different harmonic potential functions for CH3X and CD3X molecules; anharmonic corrections were subtracted from the calculated values. The force field of Aldous and Mills yielded substantially better agreement than an earlier one which was also of the general quadratic type. For the chlorides, bromides, and iodides a Urey—Bradley field was also found to give good agreement with the observed frequencies. In the fluorides the deviations for the Urey—Bradley field were larger than for either of the other two potential functions.