bluuebunny/crossref_metadata_2025 huggingface dataset:
Apparent Phase—Transition Effect in the NMR Spin—Spin Relaxation Time Caused by a Distribution of Correlation Times
Authors: Resing H. A.
Published: January 2005

It is shown that a broad distribution of correlation times produces an apparent-phase-transition effect in the NMR spin—spin relaxation time just before the onset of rigid-lattice behavior. NMR relaxation-time data for liquid water filling the pores of a charcoal adsorbent provide a sensitive test of the theory. The occurrence of the apparent phase transition for molecules adsorbed on the surfaces of solids provides a method of estimating the spread of activation energies for surface diffusion and thereby provides a new method for studying the heterogeneity of surfaces.
Current Oscillations in Solid Polystyrene and Polystyrene Solutions
Authors: Weinreb A. , Ohana N. , Braner A. A.
Published: January 2005

Application of a dc voltage across a plate of polystyrene gives rise to oscillatory currents which reach considerably high negative values. The dependence of current intensity (maximum, minimum, and plateau values) on various parameters (voltage, dimensions of samples and electrodes, nature of dissolved solute, etc., as well as repetitive use) is treated. The pattern of oscillation is found to depend on all these parameters, too. The length of the oscillation period decreases very quickly with increasing voltage. It depends also very strongly on the nature and pressure of the surrounding gas.
Outer-Shell Overlap Integrals as a Function of Distance for Halogen—Halogen, Halogen—Alkali, and Alkali—Alkali Ions in the Alkali Halide Lattices
Authors: Hafemeister D. W. , Flygare W. H.
Published: January 2005

The outer s- and p-electron overlap integrals involving ns, npσ, and npπ orbitals have been computed for all combinations of ion pairs in all of the alkali halide lattices. The free-ion closed-shell Hartree—Fock wavefunctions were used in all calculations. The halogen—alkali (H—M) overlaps are listed at the equilibrium internuclear distances. The halogen—alkali (H—M), halogen—halogen (H–H), and alkali—alkali (M—M) overlap integrals were computed at several internuclear distances and were found to follow the exponential form Sab=A exp(—rab/ρ). Values of A and ρ are listed for all combinations of overlaps in the alkali halides.

Various convenient combinations of sums of squares of overlaps are also given as a function of distance for all the combinations in the alkali halide lattices.
Relative Intensities of Two Rydberg Transitions in the Electron-Impact Spectrum of Water
Authors: Skerbele Ausma , Meyer Vincent D. , Lassettre Edwin N.
Published: January 2005

The electron-impact spectrum of water has been determined using a higher-resolution electron spectrometer. The intensity distribution of five peaks in the spectrum which belong to two different Rydberg transitions has been investigated at zero scattering angle and electron kinetic energy of 200 V. Quantities proportional to the optical oscillator strengths for these excitations have been compared with absorption coefficients from ultraviolet spectra. The entire electron-impact spectrum in the region below the first ionization potential shows good agreement with ultraviolet absorption.
Singlet—Triplet Exciton Absorption Spectra in Naphthalene and Pyrene Crystals
Authors: Avakian P. , Abramson E.
Published: January 2005

Singlet—triplet exciton absorption spectra have been measured in naphthalene and pyrene single crystals at room temperature by observing the dependence of the ``anti-Stokes'' emission intensity resulting from mutual annihilation of triplet pairs on the wavelength of exciting light. The origin of the naphthalene spectrum is at 21 170 cm−1, and the most prominent intervals in the vibrational structure are 490 and 1360 cm−1. The origin of the pyrene spectrum is at 16 850 cm−1, and the vibrational structure for the lowest triplet state in this crystal includes the intervals 410, 1210, 1380, and 1590 cm−1.
Matrix Isolation Study of the Reaction of Cl Atoms with CO. The Infrared Spectrum of the Free Radical ClCO
Authors: Jacox Marilyn E. , Milligan Dolphus E.
Published: January 2005

Cl atoms have been produced by the photolysis of HCl, Cl2, Cl2CO, and (ClCO)2 in a matrix at 14°K. These atoms are found to react with CO with essentially zero activation energy, producing the previously unobserved free radical ClCO. The vibrational fundamentals of this species have been observed at 281, 570, and 1880 cm−1. Assuming that the ClCO valence angle is 120° or 135° and that the bond distances are similar to those observed for Cl2CO, it is possible to estimate force constants and to calculate frequencies for Cl13CO in reasonable agreement with those observed for this species. The C=O bond is found to possess partial triple-bond character. The thermodynamic properties of ClCO have also been estimated. No ultraviolet absorptions have been observed for this species in the region between 4500 and 2500 Å.
Luminescence of Rare-Earth-Activated Zinc Sulfide
Authors: Anderson W. W. , Razi S. , Walsh D. J.
Published: January 2005

The line structure of the photoluminescence of ZnS:Tb, ZnS:Nd, ZnS:Tm, and ZnS:Dy has been studied under various preparative conditions. There is a strong tendency for rare-earth pairing with other lattice defects in the presence of excess S. This pairing is manifested by the appearance of new emission lines and excitation bands. Of the many distinct sites for the rare-earth ion, one seems to stand out as most important in electroluminescence, although it gives only a minor contribution to the photoluminescence. Using a variety of luminescent phenomena, we are able to count at least four distinct sites for trivalent rare-earth ions in ZnS, and there is strong evidence that more exist.
Effect of Temperature on Fluorescence Quantum Yields in Solution
Authors: Ware William R. , Baldwin Bernard A.
Published: January 2005

Fluorescence quantum yields and lifetimes have been measured as a function of temperature for anthracene and 9,10-dichloroanthracene in hexane and ethanol. It was found that the radiative transition probabilities are very slightly temperature dependent. However, for the nonradiative processes, 9,10-dichloroanthracene shows a strong temperature dependence, whereas anthracene shows none.
Effect of High Pressures on the Compressibilities of Seven Crystals Having the NaCl or CsCl Structure
Authors: Perez-Albuerne E. A. , Drickamer H. G.
Published: January 2005

The effect of pressure to several hundred kilobars has been measured on the compressibilities of seven substances having the NaCl (fcc) or CsCl (sc) structure. These include NaCl, KCl, CsCl, MgO, CaO, CaS, and TlI. For the first four crystals a Born—Mayer treatment involving the Madelung energy, van der Waals' terms, and an exponential repulsion (with constants evaluated from initial volume and compressibility) gave a quantitative fit throughout the range. CaO has a measurable lower compressibility at high pressure than predicted from the theory. This effect is exaggerated in CaS. An interesting feature of the behavior of TlI is that although it exhibits metallic conductivity above 160 kbar, there is no measurable discontinuity in the compressibility near this point.
Total Cross Sections for Ionization and Attachment in Gases by Electron Impact. II. Negative-Ion Formation
Authors: Rapp Donald , Briglia Donald D.
Published: January 2005

Absolute total cross sections for negative-ion formation in several gases (CO, NO, O2, CO2, N2O, SF6, and H2) by electron impact have been measured in a total ionization tube. Both dissociative attachment and ion-pair formation have been measured, with careful attention paid to complete collection of the negative ions. Possible errors due to scattered electrons and energy spread are discussed.
Pressure-Induced Shifts of Hydrogen Fluoride Lines Due to Noble Gases
Authors: Jaffe J. H. , Rosenberg A. , Hirshfeld M. A. , Gailar N. M.
Published: January 2005

The pressure-induced shifts of hydrogen fluoride 1–0 and 2–0 band lines due to noble gases were measured. The shifts have the same general features as those observed with HCl, but they display certain peculiarities that have been interpreted by using a phase-shift theory with a particular collision model.
Effects of Pressure on the Electrical Conductivity of Some Organic Charge-Transfer Complexes
Authors: Okamoto Y. , Shah S. , Matsunaga Y.
Published: January 2005

The effects of pressure and temperature on the electrical conductivity of some highly conductive charge-transfer complexes such as dibenzo[c, d]phenothiazine—dichlorodicyano-p-benzoquinone (2:1), dibenzo-[c, d]phenothiazine—dibromodicyano-p-benzoquinone (3:2), tetrathiotetracene—o-chloranil (3:1), tetrathiotetracene—o-bromanil (3:1) complexes are reported. The resistivity of these complexes under pressure follows the usual exponential law; 1/σ=ρ=ρ0 exp (E/kT). The measurements are carried out at a temperature range of 27°—120°C. The highest pressure applied is 40 kbar. The resistivity decreases with increasing pressure. However, this change is only of the order of 10 (from 1 to 30 000 bar). The activation energies also decrease with increasing applied pressure and the values in the tetrathiotetracene complexes become almost zero at about 35 kbar. The ρ0 obtained for these complexes increases with increasing pressure. The effect of pressure on the electrical properties of the organic solids is discussed.
Influence of Energy Transfer by the Exchange Mechanism on Donor Luminescence
Authors: Inokuti Mitio , Hirayama Fumio
Published: January 2005

The decay of donor luminescence in a rigid solution when modified by electronic energy transfer by the exchange mechanism is treated theoretically. The rate constant for the elementary process of energy transfer is taken to be of the Dexter form, const exp(−2R/L), where R is the donor—acceptor distance and L is a positive constant. Calculations are made of the yield and decay time of the donor luminescence as functions of the acceptor concentration. The resulting relationship among the above quantities enables one to analyze experimental data in a quantitative manner, and thereby to obtain information about an intermolecular exchange interaction. As an example of such an analysis, Ermolaev's data on triplet—triplet transfer between some aromatic molecules are compared with our results, and very good agreement is found with a choice of the single parameter L.
Mechanisms of Photochemical Reactions in Solution. XXXIII. Intersystem Crossing Efficiencies
Authors: Lamola Angelo A. , Hammond George S.
Published: January 2005

A simple method for measurement of quantum yields for the singlet→triplet crossing process in solution has been developed. The compound to be tested is used as a sensitizer for one or more cis—trans isomerization reactions and the quantum yield of the induced process is measured. The results are discussed briefly
Time-Correlation Function of Molecular Random Motion and Shape of Spectral Bands
Authors: Shimizu Hiroshi
Published: January 2005

It is shown that there is a close relation between the spectral density of Brownian motion and the band shape of a spectrum related to a general excitation-response process, and that time-correlation functions of a molecular system are obtained from the observed band shape of spectra. The correlation function for rotational Brownian motion of a molecular system is considered theoretically. Two limits of Brownian motion—the inertial limit and the Debye limit—are conveniently assumed. In the inertial limit, the correlation function is composed from two different parts, owing to the discrete nature of fluid in which the molecules are immersed. The first part of the correlation function gives the broadening of spectrum and the second part the narrowing. The relation between molecular motion and infrared spectrum is chosen as an illustration, because it provides simple correlation functions. Consequently, a theory of the band shape of infrared spectrum is presented in terms of the correlation function. The general features of the correlation function obtained from theoretical consideration are consistent with those obtained from the infrared spectrum of trans-dichloroethylene. In the Debye limit the effect of motion of neighboring molecules is considered. This leads a narrowing in the distribution of correlation times. The result is compared with the distribution function obtained experimentally through the Cole—Cole diagram.

The theory of nuclear spin relaxation is examined carefully. It is shown that Schwinger and Bloembergen's theory cannot be applicable to large molecules and that Bloembergen's treatment for the relaxation in the liquid state is not applicable to nonviscous liquid. A more general description is proposed.
Microwave Spectra and Molecular Structures of POF3, PSF3, POCl3, and PSCl3
Authors: Williams Quitman , Sheridan John , Gordy Walter
Published: January 2005

From measurements of pure rotational transitions in the microwave region the following B0 values in Mc/sec were determined: 4594.25±0.04 for PO16F3, 4395.27±0.20 for PO18F3, 2657.63±0.04 for PS32F3, 2614.73±0.04 for PS33F3, 2579.77±0.04 for PS34F3, 2015.20±0.05 for PO16Cl335, 1932.38±0.08 for PO16Cl337, 1402.64±0.05 for PS32Cl235, 1355.72±0.05 for PS32Cl337, 1370.13±0.05 for PS34Cl335. With the aid of electron diffraction results the molecular structures have been determined as follows: for POF3, dPO=1.45±0.03A, dPF=1.52±0.02A and ∠FPF=102.5°±2°; for PSF3, dPS=1.87±0.03A, dPF=1.53±0.02A and ∠FPF=100.3°±2°; for POCl3, dPO=1.45±0.03A, dPCl=1.99±0.02A and ∠ClPCl=103.6°±2°. The structure of PSCl3, determined entirely from microwave data is: dPS=1.85±0.02, dPCl=2.02±0.01 and ∠ClPCl=100.5°±1°.
On the Free Energy of a Mixture of Ions: An Extension of Kramers' Theory
Authors: Berlin T. H. , Montroll E. W.
Published: January 2005

A theory of electrolytes founded on the principles of statistical mechanics is presented. The primary physical assumptions are: (1) point ions, and (2) small fluctuations. The theory is a modification of Kramers' theory of electrolytes. The modification consists of a more physically accurate development of assumption (2). The main result of the present theory is that a partition function for the electrolyte is obtained for all concentrations, whereas Kramers' theory breaks down beyond a limiting concentration. The deviation from the Debye-Hueckel limiting law is in the direction of the experimental observations.
The Self-Diffusion of Liquid Mercury
Authors: Hoffman R. E.
Published: January 2005

Self-diffusion coefficients in liquid mercury have been measured by the capillary technique and have been found to be in disagreement with the earlier calculated values of Haissinsky and Cottin. In view of the fact that the present data have been obtained by direct measurement and are also much more compatible with known viscosity data, it is concluded that the data of Haissinsky and Cottin are invalid. An examination of liquid self-diffusion data in general has shown that the Stokes-Einstein equation usually gives a much better correlation of self-diffusion and viscosity coefficients than the Eyring equation.
An Analytical Method for the Approximate Determination of the Eigenfunctions and Energies of Electrons in Atoms
Authors: Gáspár R.
Published: January 2005

The first part of this paper shows that the reduced effective nuclear charges Zp/Z, determined without exchange by the ``self-consistent field'' method, can be approximated by a universal function, if the distance from the nucleus is measured in the unit of length μ=0.8853a0/Z⅓, which changes from atom to atom. This universal function can also be approximated by a simple analytical expression. One of the possible applications of the above result is to use it to determine good starting potentials for calculations to be carried out by the ``self-consistent field'' method. The universal effective nuclear charge, especially in its analytical form, also allows the determination of important atomic constants for each element of the periodic system. The second part of the paper solves the one-electron Schrödinger equation by Rasetti's method, developing it to determine analytically the eigenfunctions and energies of electrons in the deepest s, p, d, and f energy states. The x-ray terms obtained by this method and the experimental ones are in good agreement with each other and with those calculated by the ``self-consistent field'' method.
Infrared Spectra of H2O and CO2 at 500°C
Authors: Taylor J. H. , Benedict W. S. , Strong J.
Published: January 2005

A porcelain-lined absorption cell of the Pfund type is described, in which 3 meters of gas may be heated to temperatures above 500°C. The spectra of air at atmospheric pressure containing varying amounts of H2O and CO2 have been obtained in this cell between 2.4–15μ with a prism spectrometer, and between 13–25μ with a grating spectrometer giving spectral resolution of about 2 cm−1. A number of new lines in the pure rotation spectrum and the ν2vibration of H2O, originating from levels of high energy, have been observed and classified. New CO2 bands in the regions of 11–20μ and 5μ have also been observed, originating from levels as high as 5ν2, and leading to improved values of higher-quanta levels of ν2 and vibrational constants for this molecule.
Viscosity, Self-Diffusion, and Allied Effects in Solid Polymers
Authors: Bueche F.
Published: January 2005

An attempt has been made to explain the observed viscous behavior of bulk polymers. It is found that the viscosity and diffusion may be represented by a theory which takes into account the coupling together of the molecules. Two equivalent treatments are given. One makes use of a segmental friction factor in the same manner as the common formulation of dilute solution viscosity of polymers. The second method uses the concept of segmental jumping. Since both are equivalent, an expression for the friction factor is found in terms of the segmental jumping frequency. Using this fact it is possible to calculate the segmental jumping frequency from bulk viscosity data. A simple application leads to the result that the jumping frequency is about 0.3 sec−1 at the transition temperature in polystyrene.

In addition a simple relation is found to hold between bulk viscosity and diffusion constant. The proportionality constant is easily evaluated and so one is now able to obtain self-diffusion constants directly from viscosity data.
Random Flight with Multiple Partial Correlations
Authors: Tchen C. M.
Published: January 2005

The fundamental statistical properties of a linear polymer can be best studied by a more general model of random flight with multiple partial correlations. Results show that the problems of free rotation and symmetrically restricted rotation in polymers correspond to one and two partial correlations, respectively. The present study of the correlation function by means of difference equations enables one to carry out the generalization to higher orders of partial correlations. The mean square value of the distance r between the ends of the chain is studied for both finite and infinite number of links, and for multiple partial correlations. It is shown that the case of one partial correlation corresponds to a Markoff chain, and the distribution of r is found to be normal.
Far U.V. Spectra of Peptides
Authors: Ham Joe S. , Platt J. R.
Published: January 2005

The spectra of diglycyl, triglycyl, and glycine anhydride have been extended to 1800A in water solution. The peak observed near 1850A is attributed to an almost additive absorption by the —CONH— groups. The oscillator strength f is 0.27±0.07 per peptide group.
Kinetics of a Fixed Bed System for Solid Diffusion into Spherical Particles
Authors: Rosen J. B.
Published: January 2005

A solution is presented to the general problem of the transient behavior of a linear fixed bed system where the rate of adsorption is determined by the combined effect of a liquid film and solid diffusion into spherical particles. The result obtained is an expression for the effluent following a sudden change in the influent concentration. It is given in two forms: (a) An exact solution to the problem in the form of an infinite integral suitable for numerical integration. (b) An approximation to the exact solution together with an expression for the leading error term in this approximation. The approximate solution and the error term are given as closed trigonometric expressions which can be easily evaluated.
The Mechanism of Hydrogen Evolution at Nickel Cathodes in Aqueous Solutions
Authors: Bockris J. O'M. , Potter E. C.
Published: January 2005

Hydrogen overpotential at nickel cathodes has been measured under very pure conditions in aqueous solutions of hydrogen chloride (0.001N − 1.0N) and in aqueous sodium hydroxide (0.001N − 0.2N). The measurements have been made in the current density range 10−8 − 10−1 amp/apparent cm2, and in the temperature range 0°—50°C. Observations were also made of the buildup and rate of decay of overpotential and of the capacity of the electrode/electrolyte interface. Direct measurements were made of the number of acts of the rate-determining step associated with one act of the over-all hydrogen evolution reaction (i.e., the stoichiometric number μ). The application of μ has been extended to hydrogen overpotentials greater than about − 20 millivolts. The experimental data were treated statistically and show that the most probable mechanism of hydrogen overpotential at nickel cathodes is that of a rate-determining discharge step followed by a recombination of hydrogen atoms. The discharge probably takes place from hydroxonium ions in acid solution. In alkaline solution the observed pH effect on overpotential is best explained by assuming that the discharge occurs from water molecules whose activity depends on the electrode field. Consideration of the role of chemisorption in the hydrogen electrode process indicates that a rate-determining discharge step can take place from a nickel surface substantially occupied with hydrogen atoms.
On the Cubic Law of Oxidation
Authors: Waber J. T.
Published: January 2005

Experimental and theoretical studies are reviewed to indicate that a cubic law of oxidation occurs at low temperatures. Data for tantalum and titanium have been presented to indicate that this growth law may apply to more metals than suspected in the past.
Dimensions of Polybutadiene-Type Molecules
Authors: Markovitz Hershel
Published: January 2005

The calculation of root-mean-square end-to-end distances (Rp) is carried out for polybutadiene-type molecules. A table and graphs are given for this dimension as a function of the fraction of 1,2 and 1,4 addition and the percentage cis- and trans-configuration about the double bonds remaining in the chain. Also the root-mean-square radius of gyration (Rg) for molecules with all 1,4 addition has been calculated. It is found that Rp2=6Rg2 as is true for polymer molecules all of whose bonds can rotate completely freely and for those molecules where freely rotating bonds maintain fixed valence angles. Free rotation about the single bonds, a linear chain, no volume exclusion effect, and a polymer molecule with many monomer units are assumed.
Isotopic Composition of Oxygen in the Catalytic Decomposition of Hydrogen Peroxide
Authors: Dole Malcolm , Rudd DeForest P. , Muchow Gordon R. , Comte Charles
Published: January 2005

The isotopic composition of oxygen liberated in the catalytic decomposition of hydrogen peroxide using MnO2, Fe2O3, colloidal gold, metallic platinum, and soluble catalase as catalysts has been measured. All the catalysts except catalase produced a measurable fractionation of the oxygen isotopes in the case of complete decomposition. A few rate experiments were also carried out, and the kinetics studied from the standpoint of isotope separation as a function of fraction of hydrogen peroxide decomposed. It is demonstrated that none of the liberated oxygen comes from the substrate water or from the potassium permanganate when hydrogen peroxide is oxidized. Observed fractionation factors are somewhat smaller than the maximum values calculated on the basis of Bigeleisen's equations. A minimum in the O18 percentage of the evolved oxygen in the case of the catalase experiments suggests that two mechanisms are operative for this type of catalysis.

The initial enhancement of the O18 percentage of the evolved oxygen over that in the peroxide remains unexplained.
Polarization in Electrolytic Solutions. Part I. Theory
Authors: Chang Hung-Chi , Jaffé George
Published: January 2005

The theory of ``Conductance in Polarizable Media'' developed by one of the authors is modified in such a way as to be applicable to electrolytic solutions. This is achieved by the introduction of a new set of boundary conditions. In their original form they expressed the fact that the polarizing ions could not carry any current through the boundary. Now it is assumed that the discharge at the electrodes is a rate process of the first order, characterized by a rate constant ξ. In Sec. II the case of an applied ac voltage is treated. The expressions for the equivalent parallel conductance and capacitance of the polarization layer 1/Rp and Cp are derived by the same method, and to the same extent, as in the older theory. If ξ tends to zero, the previous results are obtained (``completely blocked electrode''). If ξ increases, the ``polarization capacitance'' and the ``excess resistance'' both decrease until they vanish for ξ=∞ (``open electrode''). The dependence on frequency remains similar for all finite values of ξ, and is represented in Figs. 1 and 2. Subsequently, in Sec. III, the older theory is improved by a determination of the thickness of the polarization layer. Reduced values of 1/Rp and Cp can be represented as universal functions of one reduced variable, which is proportional to the frequency. The two universal functions are tabulated to some extent in Table I. Finally the theory is extended to the case where several groups of ions of different mobilities are present in the electrolyte.
The Rotation-Vibration Spectra of Allene and Allene-d4
Authors: Lord R. C. , Venkateswarlu Putcha
Published: January 2005

The infrared absorption spectra of allene and allene-d4 vapor have been measured over the spectral range 250–5000 cm−1 with a prism spectrometer. The infrared data, together with previously obtained Raman spectra, enable a complete vibrational analysis that satisfies the product rule well for all vibrational species. The torsional vibration is located at 865 cm−1 in allene and 615 cm−1 in allene-d4. Fine structure was resolved for all perpendicular fundamental bands except that of the lowest frequency in both compounds. With help of the zeta-sum rule, a modified equation of H. H. Nielsen and the statistical weights of the rotational levels, the fine structure is analyzed to yield a complete set of zeta-values for both molecules and a moderately accurate value for the moment of inertia about the figure axis. The latter gives for the HCH angle the figure 113°±1° if one assumes a C–H distance of 1.071A.
Markoff Random Processes and the Statistical Mechanics of Time-Dependent Phenomena
Authors: Green Melville S.
Published: January 2005

Two principles of a statistical mechanics of time-dependent phenomena are proposed and argued for. The first states that the proper mathematical object to describe the physical situation is the stationary random process specified by the ensemble of time series ai(Xt)i=1···s and the distribution ρ(X). The set phase functions ai(X)i=1···s represent the set of grossly observable features of the system. Xt is the image of the phase X after time t. ρ(X) is a stationary distribution. The second principle is concerned with the very common case in which the phenomenological equations are of the first order in time and states that in this case the random process in question is a Markoff process. A Fokker-Planck equation is derived for the process, and an entropy is defined and is shown always to increase. Phenomenological equations are derived as a first approximation to the Markoff process. These involve a certain matrix ξij which is shown to satisfy symmetry relations which are a generalization of Onsager's. The theory is applied to the uniformization of the direction of momentum of a particle on a two-dimensional torus subject to a small perturbing potential.
A Calculation of the Static Dielectric Constant of Ice
Authors: Powles J. G.
Published: January 2005

A calculation is made of the static dielectric constant of ice using only simple molecular data and with well-defined assumptions as to the possibilities of molecular movement in the crystal. The paper serves as an illustration of the procedure for calculating static dielectric constants, and it results in a numerical value of this quantity for ice which is in reasonable agreement with experiment.
Sedimentation Behavior of Flexible Chain Molecules: Polyisobutylene
Authors: Mandelkern L. , Krigbaum W. R. , Scheraga H. A. , Flory P. J.
Published: January 2005

The sedimentation constants s0 at infinite dilution and the intrinsic viscosities [η] of five fractions of polyisobutylene have been determined in cyclohexane, a good solvent. Their osmotic molecular weights ranged from 3.1×104 to 1.4×106. Under the assumption that the effective hydrodynamic radii vary as the average linear dimensions of the molecule, f0/η0=P(〈r2〉)½ and [η]=Φ(〈r2〉)32/M, where f0 is the frictional coefficient, η0 is the viscosity of the solvent, 〈r2〉 is the mean-square end-to-end distance of the molecule, and P and Φ are constants. In confirmation, s0[η]⅓/M⅔ is constant throughout the molecular weight range investigated. Furthermore, Φ⅓P−1=2.5×106. The close agreement of this quantity with values for four other systems reported in the literature indicates that P, like Φ, is a universal constant for flexible chain molecules. It follows also that the observed proportionality of s0 (or of M/f0) to M0.42 instead of to M½ occurs because of intramolecular interactions which cause the molecule in solution to be expanded by a factor α which increases with molecular weight.

The above theory accounts for both the sedimentation and intrinsic viscosity behavior of flexible chain molecules in a satisfactory manner. Neither the Kirkwood-Riseman nor the Debye-Bueche theories succeeds in doing so.
Spin Densities and the Heisenberg Exchange Interaction
Authors: McWeeny R. , Yonezawa F.
Published: January 2005

The spin Hamiltonian HS=E0−JABSA·SB is derived for two arbitrary nonorthogonal systems, to a certain well-defined order. It is shown that the coupling constant, which no longer necessarily takes only positive values, is determined by the electron densities and spin densities of the two systems.
Electron Spin Resonance Investigation of Photochromic Sodalites
Authors: Hodgson William G. , Brinen Jacob S. , Williams Emil F.
Published: January 2005

Synthetic sodalites containing sulfur and showing considerable photochromic activity have been investigated by ESR. The center responsible for the color has been shown to be an electron trapped at a chlorine vacancy. The origin of the electron which is reversibly transferred during the processes of coloration and bleaching is believed to be the ion S2−.
Born Inelastic Differential Cross Sections in H2
Authors: Miller Kenneth J. , Krauss Morris
Published: January 2005

First Born differential cross sections are calculated for inelastic electron scattering of 300-eV electrons off H2 for excitations from the ground electronic—vibrational state into the vibrational levels of the B, B′, C, D, and D′ Rydberg states. The initial and final state electronic wavefunctions were approximated by Hartree—Fock functions. In order to facilitate the calculation, the molecular orbitals were expanded in a linear combination of Gaussian-type atomic orbitals.

The variation of the electronic scattering amplitude was examined as a function of molecular orientation, internuclear separation, and scattering angle (or electron momentum transfer). It is shown that the use of the Franck—Condon factors to determine relative intensities for scattering into different vibrational levels yields errors of less than 20%, and hence these factors are a good approximation to the relative intensities.

The theoretical differential cross section for zero-angle scattering is in good agreement with the most recent experimental data, and transition moments extracted from electron scattering experiments within the context of the Franck—Condon principle are in agreement with the theoretical values.
Crystal Structure of Piezoelectric Bismuth Germanium Oxide Bi12GeO20
Authors: Abrahams S. C. , Jamieson P. B. , Bernstein J. L.
Published: January 2005

Piezoelectric Bi12GeO20 crystallizes in the cubic system with space group I23 and lattice constant a = 10.1455±0.0008 Å at 298°K. The complete x-ray scattering pattern within a reciprocal lattice hemisphere of radius (sinθ)/λ = 1.02 Å−1 was determined with PEXRAD. A total of 4812 reflections were measured, resulting in 631 independent and significantly nonzero Fmeas. The crystal structure was solved using three-dimensional Patterson and Fourier series, and refined by the method of least squares. The final agreement factor R is 0.062. The germanium atoms occupy geometrically regular tetrahedra, with Ge–O=1.717±0.028 Å. The bismuth atoms are heptacoordinated: five oxygen atoms form an incomplete octahedral arrangement, with Bi–O distances ranging from 2.076±0.027 to 2.640±0.028 Å. The remaining two oxygen atoms are electrostatically coordinated, on either side of the 6s2 inert electron pair in Bi3+, at distances of 3.082 and 3.170 Å from bismuth. The Bi atom vibrates anisotropically. The absolute configuration of the atomic arrangement has been determined. The positive piezoelectric polarization induced by compressive stress applied along 〈111〉 is given by the normal to a triangular GeO4 tetrahedral face in the direction from the Ge atom to the face.
Extensions of the Widom Model for Two- and Three-Component Liquid Mixtures
Authors: Neece George
Published: January 2005

A decorated lattice model recently proposed by Widom in a study of the plait points in two- and three-component liquid mixtures is extended to include the effects of interactions between molecules on the model's primary lattice. The extended model exhibits a variety of behavior with changing temperature. A decorated lattice model of a three-component mixture is also presented, and the behavior of its plait point is discussed.
Magnetic-Field Interactions in a Rotating Molecule
Authors: Hüttner W. , Flygare W. H.
Published: January 2005

Rotational—magnetic-field interactions of a molecule with zero electronic spin and zero orbital angular momentum are treated. The external magnetic field gives rise to interactions involving the molecular-magnetic-moment tensor (molecular g tensor), the magnetic-susceptibility tensor, and the nuclear magnetic-shielding tensor. The tensors are described in the principal inertial-axis system. Two types of molecules are considered. In the first case only external magnetic-field-induced nuclear-rotational couplings are present. In the second case a strong nuclear-quadrupole and spin—rotation coupling is added. The possibility of determining the diagonal elements in the above tensors by high-resolution microwave spectroscopy is discussed. Appropriate first-order expressions are given for a general asymmetric-top molecule.
Vapor Pressures of Isotopic Methanes—Evidence for Hindered Rotation
Authors: Bigeleisen J. , Cragg C. B. , Jeevanandam M.
Published: January 2005

The liquid—vapor separation factors of CH3T and 14CH4 from 12CH4 have been determined over the temperature range 90°—120°K by the column-distillation technique. 14CH4 is less volatile than 12CH4 over the measured temperature range; CH3T shows the cross over at 103.9°K. The reduced partition function ratios derived from the elementary separation factors are lnfc/fg(14CH4/12CH4)=231/T2−1.42/T,lnfc/fg(CH3T/12CH4)=503/T2−4.83/T.

The reduced partition functions of all the deuteromethanes and 13CH4 in the liquid and solid are derived from known vapor-pressure data. Comparison of the T−2 dependence of species of equal molecular weight but different moments of inertia, i.e., CH3D and 13CH4, and 14CH4, CH3T, and CH2D2, with model calculations leads to the conclusion that the rotation in methane is hindered both in the liquid and the solid.
Competitive Unimolecular Decomposition in Chemically Activated Radical Systems
Authors: Larson C. W. , Rabinovitch B. S. , Tardy D. C.
Published: January 2005

The study of the competitive unimolecular decomposition of chemically activated alkyl radicals has been extended. Relative and absolute rates of decomposition for the series of radicals 3-methyl—butyl-2, 3-methyl—pentyl-2, 3-ethyl—pentyl-2, 2-methyl—pentyl-3, 2-methyl—hexyl-3, and 3-methyl—hexyl-3, each of which possess from two to four carbon—carbon rupture reaction channels, have been measured.

A quantum-statistical model for the absolute decomposition rates provided good theoretical agreement with the experiments. The measurement of relative rupture rates provided stringent conditions on the permissible values of the differences in critical energies ΔE0 for the competing decomposition modes. They also allowed the formulation of a consistent prescription for making the vibrational assignment for the decomposition complexes of the six radicals. The results are compatible with D0∘(CH3–H)−D0∘(C2H5–H)=5.7 kcal mole−1 and differences between critical heats of addition of methyl and ethyl radicals to olefins, Ec(Me, olefin) — Ec(Et, olefin), which vary systematically from −0.2 to 0.9 kcal mole−1.
Redetermination of the Structure of the Ferroelectric Crystal Guanidinium Aluminum Sulfate Hexahydrate, GASH, and its Chromium Isomorph
Authors: Schein B. J. B. , Lingafelter E. C. , Stewart J. M.
Published: January 2005

Calculations with hypothetical data suggest the presence of nonrandom errors in earlier x-ray diffraction data on GASH, which caused the difficulties in refinement of its crystal structure. New data have been collected on GASH and on GCrSH and the structures of the two compounds have been refined to final R values of 0.035 and 0.036, respectively, reducing the estimated standard deviations of the parameters by a factor of about 5.
Collisional Transfer Contributions in the Quantum Theory of Transport Coefficients
Authors: Imam-Rahajoe S. , Curtiss C. F.
Published: January 2005

The quantum-mechanical BBGKY equations are solved in terms of the phase-space transformation functions. Introducing the molecular-chaos assumption, the pair distribution function is obtained. In the binary-collision approximation, this leads to a generalized Boltzmann equation, in which the collisional-transfer contributions are included. This equation is solved by the method of Chapman and Enskog, and expressions for the transport coefficients are obtained, which are given entirely in terms of the solutions of the two-particle Schrödinger equation. The classical limit (ℏ→0) of the expressions are also derived. The heat flux is found to contain contributions which are proportional to the gradient in density. The significance of these terms, which are of the order ℏ4, is discussed.
Linear Relation of Temperature and Density at Unit Compressibility Factor
Authors: Holleran Eugene M.
Published: January 2005

A linear relation is found for the experimental temperatures and densities at which the compressibility factor PV/RT equals unity. The two characteristic constants of the relation are evaluated for 12 gases for which appropriate data exist. The pertinent range of temperature and density for gases is from the critical temperature to the Boyle temperature, and from zero density to over twice the critical density. For one gas, Ar, the available data extend over this entire range and fit the linear law to within two parts per thousand. For CH4, Xe, and C2H4 over shorter ranges, the data are linear to within a few parts in ten thousand.

Implications of the relation are discussed, including its usefulness as a necessary condition for equations of state, as a basis for a corresponding states treatment, as a means for detecting and correcting experimental errors in PVT measurements, and in providing a possible insight into the nature of intermolecular forces.
Resonance Absorption of p-Benzosemiquinone in the Zeeman Region
Authors: Acrivos Juana V.
Published: January 2005

The resonance absorption of p-benzosemiquinone in sodium ethylate—ethanol solution has been determined from t=−50°C to room temperature in the Zeeman region at frequencies of the order of the zero field splitting produced by the isotropic hyperfine coupling. At t=−50°C, the resonance absorption indicated free-radical interactions with two sodium nuclei. The isotropic coupling constants measured for the free electron spin—1H and 23Na interactions were, respectively, | A | = 6.63±0.01 MHz and | A′| = 0.34±0.05 MHz. Due to the finite widths, resonance absorptions were observed near Hz = 0 for rf frequencies of ν/ | A | = 2.48±0.01 and 1.49±0.01. The observed linewidth inverse temperature dependence for −20°≤t≤0°C was explained on the basis of the over-all chemical exchange process[Complex chemical formula],whence the first-order rate of disappearance chemical exchange time τe,k=|A′|−1×exp[Ea(T−1−T0−1)/R] was obtained. The over-all energy of activation was determined to be Ea = 10±1 kcal mole−1 and T0 = 253°±5°K. Also, since the solvent—free-radical interactions occur at the end oxygen atoms, an estimate was made of the role played by the spin—orbit—lattice interactions introduced in the p-benzosemiquinone ion by the asymmetric vibration of the CO bonds. In the Zeeman region, the transition probability per unit time between a participating pair of levels induced by Van Vleck second-order Raman processes was estimated to be of the same order of magnitude, W∼104 sec−1, as other processes considered previously for p-benzosemiquinone in solution. This is however two orders of magnitude less than the experimental values.
Thermal Conductivity of Molten Alkali Nitrates
Authors: White Lloyd R. , Davis H. Ted
Published: January 2005

Measurements of the thermal conductivities of the molten alkali nitrates are reported. A law of corresponding states is found for the conductivities, but an entirely satisfactory theoretical basis of the law is not yet available. At atmospheric pressure the conductivities increase with temperature, a behavior seen in associated liquids such as water. Moreover, the same temperature trend is observed for solid-state thermal conductivities near the melting point. This indicates that the temperature trend observed for the conductivities of the melts is not peculiar to the liquid state but is perhaps due to the nitrate ion or to the long-range Coulombic interactions. Use of the hot-wire transient method for studying thermal conductivities of molten salts is criticized.
Perimetric Coordinates
Authors: Wang Pearl S. C.
Published: January 2005

Pekeris introduced perimetric coordinates to treat the helium atom, a three-particle system. Recently several attempts have been made to obtain perimetric coordinates for four-particle systems. The purpose of this paper is to point out that such coordinates do not exist for systems containing four or more particles.
Spin-Lattice Relaxation and Phase Transitions in Deuterated Ammonium Bromide
Authors: Woessner D. E. , Snowden B. S.
Published: January 2005

We have studied the low-temperature order-order transition in deuterated ammonium bromide. In a 99% deuterated sample of ammonium bromide, a hysteresis effect is observed. The T1 minimum value obtained with a decreasing temperature sequence appeared 0.06 msec higher than the value of 0.45 msec obtained with an increasing temperature sequence. With a 94% deuterated sample of ammonium bromide, no such hysteresis effect is observed. Assuming that the activation energy is a function only of lattice type, it is possible to explain this behavior in 99% ND4Br in terms of the coexistence of two phases in the temperature range between 163° and 169°K.
Excited Species and Their Contribution to NO(β, γ) Fluorescence in the Photodissociation of N2O
Authors: Okabe H.
Published: January 2005

The fluorescence intensity and the yield of the NO β bands, originating from photodissociation of N2O, was measured as a function of wavelength of incident light in the vacuum ultraviolet region. Photon energies required for the occurrence of the fluorescence are far less than the threshold energy to produce NO(A2 Σ+, B 2Πr) directly from N2O, indicating that the emission is due to secondary processes. The fluorescence intensity curve follows closely the absorption curve of N2O indicating that excited species responsible for the emission are produced from dissociation of electronically excited N2O rather than from the direct dissociation to these species. A mechanism of fluorescence is discussed on the basis of the threshold energy above which a specific photochemical process is possible. Reactions responsible for the β emission in the absorption region 1400 to 1550 Å of N2O are production of N(2D) and O(1S) followed by N(2D)+N2O→N2+NO(B 2Πr) and O(1S)+N2O→NO+NO(B 2Πr). In the region below 1400 Å, N(2P) and N2(B 3Πg, B′ 3Σu−) also can contribute to the emission. When NO was added to N2O, the fluorescence intensity increased considerably and the emission changed from β to γ bands. Reactions which produce the emission in the absorption region 1400 to 1550 Å are N2O→ lim hνN2(A 3Σu+)+O(3P)followed by N2(A 3Σu+)+NO→N2+NO(A 2Σ+). Below 1350 Å additional excited molecules N2(B 3Πg, B′ 3Σu−) can contribute to the emission in similar reactions.
Approximate Self-Consistent Molecular Orbital Theory. IV. Calculations on Molecules Including the Elements Sodium through Chlorine
Authors: Santry D. P. , Segal G. A.
Published: January 2005

The CNDO method is extended to molecules containing the elements sodium through chlorine and used to examine the importance of the 3d orbitals of these elements to molecular properties. An examination of the radial dependence of the 3d orbitals is carried out by performing parallel calculations with three different basis sets on a selection of molecules. A basis set in which the 3d orbitals are somewhat contracted is found to best predict molecular geometries, dipole moments, and bending force constants. The molecular dipole moments are found to present the most persuasive evidence for 3d participation, while most molecular geometries are relatively insensitive to inclusion of atomic orbitals of d symmetry.
Yield of Scavengeable Hydrogen Atoms, Electrons, and Positive Charges in the Radiolysis of Liquid n-Hexane
Authors: Rajbenbach L. A. , Kaldor U.
Published: January 2005

The yield of radiolytic hydrogen from solutions of perfluorocyclobutane in n-hexane has been compared with that obtained from n-hexane solutions containing both perfluorocyclobutane and hexene-1 or benzene. A mechanism for radiolytic hydrogen formation which assumes the existence of two precursors of molecular hydrogen is postulated. Thermal hydrogen atoms and molecular hydrogen are assumed to be formed from the decomposition of a short-lived excited-state C6H14′, a process which cannot be affected by the presence of the solutes used. The recombination of the solvent molecular cation and an electron is assumed to result predominantly in the formation of ``hot'' hydrogen atoms. Perfluorocyclobutane decreases the hydrogen yield by scavenging electrons, while hexene-1 and benzene decrease the yield of hydrogen both by charge-transfer processes and by scavenging of hydrogen atoms formed from C6H14′. The yield of scavengeable electrons, positive charges, and thermal hydrogen atoms determined by kinetic analysis are: G (electrons) = 2.6, G (positive charges) = 2.1, G (thermal hydrogens) = 1.4.