bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Contributions to the Kinetics of Growth of Multicomponent Chains with Application to the Problems of Ciliation and Fractionation in Polymer Crystallization
Authors: DiMarzio Edmund A.
Published: January 2005

The problem of the growth rate and purity of crystals formed by the sequential deposition of molecules in a mixed system is solved. The solution is given in terms of the fundamental rates aνij(βν+1ij) for laying down (taking off) species j at the (ν+1)th position of the growing crystal given that species i occupies the (ν)th position. The fundamental rates are thus dependent on nearest-neighbor interaction but not on neighbors further removed. The method used complements a previously used method and additionally solves the problem for ν-dependent ανij and βνij. The ν dependence of the α's and β's allows for the stochastic-like distribution of the various species in the substrate upon which we are growing our linear chain of molecules. It is shown that there exists one unique flux-determined steady-state solution for a wide variety of initial conditions. Several diagrams descriptive of various physical processes are displayed. The one describing ciliation (the growth process which results in the ends of polymer chains dangling out of the crystal lamella) is treated in some detail. It is found that there are two classes of α's and β's. One class gives large growth rates and very little ciliation. The second class gives growth rates which are orders of magnitudes smaller and results in much ciliation. It is concluded that when chain-folded crystallization occurs the amount of material dangling out of the crystal is less than 50% of the total amount of material participating. The problem of fractionation in polymers is treated. Formulas are given for the purity of polymer crystals which are formed by high molecular weight material crystallizing concomitantly with polymeric material of lower molecular weight and/or of different kind. Fractionation can be substantial even when the molecular weights of the mixed system are all large. Simple formulas are derived. More complicated diagrams that allow for more than nearest-neighbor interaction can be reduced to the nearest-neighbor case but with a larger number of components.
Relative Oscillator Strengths of CH. The Heat of Dissociation of CH
Authors: Linevsky Milton J.
Published: January 2005

The absorption spectra of the three electronic band systems of the CH radical have been observed in a graphite furnace containing an atmosphere of H2 gas. From the measured absorption intensities, the relative f numbers of the 4315 Å to the 3850 Å to the 3143 Å systems are found to be 1:0.62:1.26. By using the known absolute f number of the 4315 Å system and measured total absorptions, CH concentrations and, thus, the heats of formation and dissociation have been calculated. These resulting heats are: ΔH0∘(CH)=140.5±2.0 kcal/mole and D0∘(CH)=80.7±2.0 kcal/mole.
Benzene and Its Ionized States
Authors: Schulman J. M. , Moskowitz J. W.
Published: January 2005

Benzene ground and two pi ionized states, 2A2u and 2E1g, have been studied by the self-consistent-field method using contracted Gaussians as basis. Ionization potentials are assigned. A transfer of sigma charge density from hydrogen to carbon has been found to result from electron removal from the pi system.
Atomic and Molecular Calculations with the Pseudopotential Method. II. Exact Pseudopotentials for Li, Na, K, Rb, Be+, Mg+, Ca+, Al++, Cu, and Zn+
Authors: Szasz Levente , McGinn George
Published: January 2005

The pseudopotential equation of Phillips and Kleinman is solved numerically for the valence electron of the atoms Li, Na, K, Rb, Be+, Mg+, Ca+, Al++, Cu, and Zn+. In order to be able to use the pseudopotentials in molecular calculations analytic fits consisting of linear combinations of Slater functions are computed for the pseudowavefunctions. For each atom considered, the results are presented in the form of tables from which the total modified potential (Hartree—Fock potential plus pseudopotential) can be generated in any scale. The computed Phillips—Kleinman-type pseudopotentials are compared to other forms of pseudopotentials and the advantages of the P–K formulation over the other formulations are discussed.
Elastic Scattering of Low-Energy Electrons from Molecular Hydrogen
Authors: Wilkins Roger L. , Taylor Howard S.
Published: January 2005

The cross sections for elastic scattering of low-energy electrons by molecular hydrogen are calculated by solving numerically the continuum Hartree—Fock equations for an electron moving in the potential field of the neutral homonuclear diatomic hydrogen molecule. Hartree—Fock equations make full allowance for electron exchange. The cross sections for elastic scattering of electrons by molecular hydrogen are calculated with and without the inclusion of electron exchange. The agreement in the exchange approximation with experimental data is very good but disappears completely if exchange is neglected. The method of calculation is based on an expansion of the continuum orbitals up to fourth order as a product of a series of spherical harmonics and radial wavefunctions about the molecular midpoint of the molecule. The potential field of the incident electron due to the nuclei of the neutral molecule is expanded in spherical harmonics up to the eighth order. The continuum orbitals are substituted into the Hartree—Fock equations, integration is performed over angular coordinates, and the resulting infinite set of coupled differential—integral equations is truncated and solved numerically to a self-consistent solution, by an iterative technique for three radial continuum functions.
Luminescence Quenching and Decay Processes in Multicomponent Systems: n-Nonane+p-Xylene+CCl4
Authors: Amata C. D. , Ludwig P. K.
Published: January 2005

A monophoton technique to measure fast luminescence decay and utilizing pulsed uv excitation has been employed to determine specific rates of excitation quenching in systems containing n-nonane+p-xylene+CCl4, with n-nonane serving as an optically inert solvent, p-xylene as scintillator, and CCl4 as quencher. The decay-time data are employed to evaluate the characteristic rate parameters kq for quenching of p-xylene luminescence by CCl4. Values so obtained are in good agreement with values obtained from steady-state studies. The variation in kq with p-xylene concentration is consistent with the view that energy migration as such via p-xylene molecules occurs in addition to material diffusion of excited molecules. Dynamic and steady-state measurements of self-quenching in p-xylene+n-nonane systems indicate that, if excimer formation in p-xylene occurs, it is followed by a very rapid nonradiative deactivation of the excimer. Furthermore, differences in the self-quenching behavior as determined with steady-state and decay-time techniques suggest some form of static quenching in p-xylene. This static quenching can be explained on the basis of clustering in the ground state.
Improved Single-Center LCAO SCF Calculations on HF and CH4
Authors: Hoyland James R.
Published: January 2005

Calculations within the LCAO SCF framework utilizing large basis sets of Slater orbitals centered at the heavy nucleus are carried out on HF and CH4 in order to assess the feasibility of computing near-Hartree—Fock wavefunctions and energies for simple AHn-type molecules. Considerable improvement is obtained over previous results found by the single-center method, but it is concluded that it is not economically possible to extend the calculations to the accuracy given by poly-centered methods.
Lattice Scattering of Exciton in Molecular Crystals
Authors: Iguchi Kaoru
Published: January 2005

The general formulas of scattering probabilities by acoustic- and optical-mode vibrations are computed for the Frenkel exciton in molecular crystals. Two cases, fast and slow excitons, are distinguished in the formulation, and the different dependencies on temperature and wave vector are shown. At low temperature both acoustic and optical modes have about the same effect on the fast exciton, while the acoustic mode has a predominant effect on the slow exciton. The dependence of scattering probability on the direction of exciton wave vector relative to the crystal axis is also shown. The mean free path and the diffusion coefficient are calculated for the thermal equilibrium state attained after a multiple scattering. Comparison with theoretical and experimental results of other authors is discussed.
Mass-Spectrometric Study of the Thermal Decomposition of Ammonium Perchlorate
Authors: Verneker V. R. Pai , Maycock J. N.
Published: January 2005

The thermal decomposition of 14NH4ClO4, 15NH4ClO4, and deuterated ammonium perchlorate has been investigated mass spectrometrically. By investigating the decomposition at approximately 10−4 torr and also at 10−7 torr in the mass spectrometer inlet system it has been possible to clarify some of the previous conflicting data. This investigation has shown that ammonium perchlorate decomposes into O2, Cl2, N2O in the ratio of 3:2:2 at temperatures below 300°C. Activation energies for the formation of oxygen and chlorine have been calculated to be 28 kcal mole−1 which agree very well with those calculated from conventional constant-volume decompositions.
Magnetic Resonance Studies of Anisotropic Molecular Rotation in Liquid Acetonitrile-d3
Authors: Bopp Thomas T.
Published: January 2005

The magnetic relaxation times T1 for 14N and 2D in liquid CD3CN have been measured as functions of temperature and concentration of added ionic salts. With no model assumed for the reorientation process, the molecular rotation is demonstrated to be anisotropic. The further assumption of a rotational diffusion equation permits the determination of the rotational diffusion constants. At 25°C, D⊥=1.35×1011(sec)−1, and D∥=1.2×1012(sec)−1. The rotational diffusion tensor remains anisotropic over a wide range of temperatures. The addition of the perchlorates of silver, lithium, or sodium to CD3CN reduces D⊥ for bound CD3CN by a factor of 10, but leaves D∥ unchanged.
Nonstoichiometry in the Rare-Earth Aluminum Borates
Authors: Leask M. J. M. , Maxwell K. J. , Wanklyn Barbara M.
Published: January 2005

Optical spectroscopy on one of a series (the europium compound) of the rare-earth aluminium borates indicates appreciable nonstoichiometry, confirmed by further x-ray studies. Detailed studies as a function of magnetic field and temperature of a particular transition (7F0—5D1) indicate that not only the Al3+ site but also other sites are being occupied by the rare-earth ions. Crystal-field splittings in 5D1 and 7F1 agree well with Judd's calculations, confirming the assignment of levels.
Comparison of the Structures of Stretched Linear Polymers
Authors: Huggins Maurice L.
Published: January 2005

Published x-ray data from crystalline selenium and tellurium and from stretched sulfur (amorphous), polyethylene, polyisobutylene, polyvinyl alcohol, polyvinyl chloride, polyvinylidine chloride, polyoxymethylene, polyoxyethylene, polyethylene disulfide, polyethylene tetrasulfide, and polyphosphonitrile chloride are compared. In most cases the experimental identity distance in the direction of the chain axes and the expected interatomic distances and interbond angles are found to be in agreement with the assumption that the chain atoms form a regular spiral, unidirectional in each chain and of uniform pitch. Apparent exceptions are briefly discussed.
Systems Manifesting Superposed Elastic and Viscous Behavior
Authors: Tobolsky A. V. , Andrews R. D.
Published: January 2005

Actual substances exhibit a very complicated behavior under mechanical stresses which cannot be described by classical elasticity theory nor by the classical theory of the hydrodynamics of viscous fluids. A general molecular theory describing the behavior of matter under stress is discussed and related to previous investigations and to experimental observations. Particular attention is devoted to rubberlike substances for which the classical theories are definitely inadequate. Experimental results on relaxation and creep of rubbers are interpreted in terms of modern structural concepts. It is found that these substances exhibit three regions of stress-temperature-time dependence. At intermediate temperatures there exists a region of relative stability in which the statistical-thermodynamic theory of rubber elasticity is valid. At elevated temperatures relaxation and creep are caused by chemical changes involving the rupture and formation of primary valence bonds. These chemical changes, which are responsible for the aging of rubber, can be isolated and studied by appropriate experimental techniques. At low temperatures relaxation and creep are caused by the slipping of secondary interchain bonds which are breaking and reforming in times comparable to experimental times of measurement. Theories are advanced to explain the observed stress-temperature-time behavior of rubbers over the entire temperature range studied.
The Influence of Velocity Gradient on the Relation Between Viscosity and Concentration in Cuprammonium Solutions of Cellulose
Authors: Lyons W. James
Published: January 2005

The numerous equations which have hitherto been employed to relate the viscosity of solutions of high polymers to the concentration of the solute have neglected to recognize explicitly the influence which velocity gradient (rate of shear) has upon the observed viscosity of non-Newtonian liquids. Consequently, the theoretically important, intrinsic viscosity, calculated on the basis of these equations, from data obtained on a solution in the anomalous region, is found to have a different value for each velocity gradient prevailing during measurement. A modification of the Baker-Philippoff equation has been developed empirically having the advantage that it yields a uniform value for the intrinsic viscosity of a given solution regardless of changes in velocity gradient. This new equation: ηr=(1+cλ)8+(ki−8λ)c,has been found to agree well with data on cuprammonium solutions of cellulose in concentrations below 0.5 g per 100 ml. The parameter λ, interpreted as a function of velocity gradient, is found to increase with gradient, while ki, which is shown to be the intrinsic viscosity ηi, is found to have a constant value characteristic of the solute. It appears that the second constant appearing in other recent equations in addition to the intrinsic viscosity, may be interpreted as a velocity gradient adjustment term. The algebraic series into which the various recent equations can be expanded to express ηr are strikingly similar to each other and to a proposed equation based on the Eyring reaction-rate theory.
Force Constants of Triatomic Molecules
Authors: Glockler Geo. , Tung Jo-Yun
Published: January 2005

In the general expression of the potential energy of the triatomic molecule XYZ there are six force constants c1, c1′ (valence bond), c2 (angle deformation), c3, c3′ (angle bond interaction), and c4 (bond-bond interaction), of which only three can be calculated from the three experimentally determined fundamental frequencies. For the isosceles triatomic molecule YX2 the number of force constants reduces to four (c1, c2, c3, and c4). From a study of all the real values of these four force constants, it is seen that they are related to one another by ellipses and straight lines. The graphs of these ellipses indicate the possibility of choosing a certain singular point (near one end of the major axis) which gives the following relation between the force constants: dc4/dc2=0  or  dc4/dc3=0.This condition and the equations usually obtained from the theory of small vibrations permit the calculation of a singular set of four force constants of the isosceles triatomic molecule. When these force constants are applied to isotopic molecules, satisfactory checks between the calculated and experimentally determined frequencies are obtained.

The ellipses showing the relation between the force constants indicate clearly why the simple central force field (c1, c2, c3) or the simple valence force field (c1, c2, c3), containing one interaction constant or crossterm, must yield imaginary values for c2 and c3 in certain cases.
The Variation of the Transference Numbers for Calcium Chloride in Aqueous Solution with Temperature. III
Authors: Keenan A. G. , McLeod H. G. , Gordon A. R.
Published: January 2005

Transference numbers for calcium chloride in aqueous solution have been determined for concentrations up to 0.15N at 15°, 25°, and 35°C. At all three temperatures autogenic cation boundaries using cadmium chloride as indicator gave transference numbers which showed no progression as the boundary moved and were independent of current. The same was true of anion boundaries (employing calcium iodate and paratoluene sulphonate as indicators) at 25°C provided the concentrations of the indicator ions were held within rather narrow limits. Where both t+ and t− were determined for a solution, their sum was unity within the precision of the measurements. These results differ, however, from Longsworth's data by somewhat more than the apparent precision of the measurements. The variation of the transference numbers with temperature is normal in that they tend to approach one-half with increasing temperature. As in the case of sodium chloride, the variation of the transference number with concentration is independent of the temperature.
The Conductance of Aqueous Solutions of Calcium Chloride at Temperatures from 15° to 45°C
Authors: Benson G. C. , Gordon A. R.
Published: January 2005

The conductance of aqueous solutions of calcium chloride at temperatures from 15° to 45°C has been determined by the direct-current method previously used for potassium chloride, sodium chloride, and potassium bromide. The results for 25° are in excellent agreement with those of Shedlovsky and Brown. At all temperatures the data can be represented by the extended Onsager-Shedlovsky equation, as in the case of the 1–1 salts. In contrast to the 1–1 salts, however, the contribution of the logarithmic term passes through a minimum with increasing temperature, and then rises. The limiting conductance has been determined for calcium ion; the temperature coefficient of the ionic conductance is large in comparison with those for univalent ions.
A Reinvestigation of the Conductance of Aqueous Solutions of Potassium Chloride, Sodium Chloride, and Potassium Bromide at Temperatures from 15° to 45°C
Authors: Benson G. C. , Gordon A. R.
Published: January 2005

The conductance of aqueous solutions of potassium chloride, sodium chloride, and potassium bromide has been redetermined by the direct-current method at temperatures from 15° to 45°C. It is found that on the whole the present measurements satisfactorily confirm the earlier work reported from this laboratory; however, there were apparently slight errors in the temperature scale at 35° and 45° corresponding to a few hundredth's of a percent in the conductance. Revised values of the conductance, of the limiting ionic conductance and its temperature coefficient, and of the coefficients in the Onsager-Shedlovsky equation are tabulated.
The Isotope Effect and the Ratio Rule
Authors: Edgell Walter F.
Published: January 2005

A perturbation treatment of the isotope effect has been developed which gives the change in the normal coordinates as well as the frequencies of vibration. The ratio rule is obtained from this treatment, and the conditions which are prerequisite to its application are clearly indicated. At present the lack of required experimental data limits the utility of this rule somewhat, and a more useful but generally less accurate form of it has been derived, which depends for its validity upon the ability to construct symmetry coordinates which approximate the corresponding normal coordinates. The application of these equations to experimental data has been illustrated. In particular the modified ratio rule has been tested on the molecules CD4, CH3D, CHD3, CDCl3, CD3Cl, ND3, B10F3, C2D4, and C2D6 and found to give generally good results.
A Generalization of the Quasi-Chemical Method in the Statistical Theory of Superlattices
Authors: Yang C. N.
Published: January 2005

The quasi-chemical method in the investigation of the equilibrium distribution of atoms in the pairs of neighboring sites in a superlattice is generalized by considering groups containing large numbers of sites. The generalized method may be used to obtain successive approximations of the free energy of the crystal. The labor of integration is avoided by the introduction of a Legendre transformation. In order to analyze the fundamental assumption underlying the method more closely, the number of arrangements of the atoms for given long-distance order is calculated and the hypothesis of the non-interference of local configurations discussed. The method is applied to the calculation of the free energy in the different approximations discussed in this paper, including Bethe's second approximation and a simple approximation for the face-centered cubic crystal Cu3Au.
The Tetrahedral X2YZ2 Molecular Model Part II. Rotation-Vibration Energies
Authors: Shaffer W. H. , Herman R. C.
Published: January 2005

The appropriate quantum-mechanical Hamiltonian is set up according to the method of Wilson and Howard for investigating rotation-vibration energies to second-order approximation. The vibrational term G is derived explicitly as a function of the anharmonic constants, Coriolis parameters, etc. The elements are given for the secular determinant required for evaluation of the rotational term F including dependence on Coriolis interactions, centrifugal stretching, effective moments of inertia, etc. Selection rules are discussed.
Potentiometric Determinations of H-Ion Concentration in Hydrocarbon Oils
Authors: Gemant Andrew
Published: January 2005

The paper discusses potentiometric measurements of hydrogen ion concentration carried out in hydrocarbon oils that have attained high electrical conductivity (a) through oxidation in the laboratory, (b) through deterioration in service, (c) through addition of certain compounds. The e.m.f. data are interpreted by comparing them with those obtained from lauryl sulfonic acid solutions in oil. The results indicate that the hydrogen ion concentration in the three types of oils is too low to account for the total observed electrical conductivity. It is obvious, then, that the predominant mechanism of ion generation is different from the usual acidic dissociation. A bimolecular reaction leading to two organic ions is suggested on the basis of evidence from organic chemistry and a quantitative relation that follows from conductivity data presented in this paper.
An Investigation of the Determination of Molecular Weights of High Polymers by Light Scattering
Authors: Doty P. M. , Zimm B. H. , Mark H.
Published: January 2005

The determination of the molecular weights of large molecules by measuring the turbidity of the solution and the change in index of refraction with concentration is discussed. The apparatus, its calibration, and the technique used are treated together with a comparison between molecular weights measured by this method and other methods. The effect of polymolecularity is also presented.
The Near Ultraviolet Absorption Spectrum of Aniline Vapor
Authors: Ginsburg Nathan , Matsen F. A.
Published: January 2005

The absorption spectrum of aniline vapor has been photographed in the first and second order of a 3-m grating spectrograph. The strongest bands appeared as doublets and on the basis of these, a tentative analysis was made and compared with the available Raman data.
Analysis of Excitation Functions
Authors: Oldenberg O.
Published: January 2005

The mechanical laws of impact lead to the conclusion that, in any transfer of kinetic energy into quantized energy (excitation, dissociation), the ``excitation function'' should, at the threshold, start from zero and increase with increasing kinetic energy. This shape of the function is likely to cause a systematic error in the measurement of critical energies with certain non-equilibrium methods.
Target Chemistry of Zirconium and Yttrium; Isolation of Zr89 in Pure State
Authors: Kurbatov M. H. , Kurbatov J. D.
Published: January 2005

Radioactive Zr89 obtained by bombardment of Y2O3 with deuterons, was separated without addition of stable zirconium in quantities ∼10−10 gram. Oxychloride solutions of Zr89 mixed with inactive Zr were used for coagulation studies in the concentration range 1.5×10−4−1.5×10−11 gA/l. It was found that the fraction coagulated increased with dilution under the constant conditions used (pH−4.0; NaCl−2.5×10−2N; T−25°), to 2.7×10−6 gA/l. The log-log plot of zirconium concentration (C) in solution against coagulated part (c) closely approaches a straight line with exponent n=1.50 and k=490. At 1.5×10−6 gA/l and lower concentrations the coagulated fraction reaches a maximum and becomes constant, k=C/c=.45. Within the range studied salt increases coagulation of zirconium above 10−5 gA/l; but below 10−6 gA/l the salt effect is reversed. Increase in pH results in increase in the fraction coagulated (r) in all concentrations studied. At a minute concentration r=(pH—K)/m, K being 1.85 with NaCl, 0.05N and 1.58 with NaCl, 0.005N and m being 3.15. The separation of Zr89 in minute quantities without addition of stable zirconium is plausible if a Nernst distribution of zirconium between coagulated part and solution is postulated. The concept of the solubility of the hydrous oxide of zirconium as a constant quantity remaining in solution under specified conditions was not verified.
Molecular Constants and Chemical Theories
Authors: Wheland G. W.
Published: January 2005

A few selected topics from four papers by Samuel on the theory of valence are critically examined. The conclusions are drawn that Samuel's bond-moments for molecules containing ``pentacovalent nitrogen'' are not as satisfactory as claimed, and provide no evidence in favor of the existence of pentacovalent nitrogen; that Samuel's eigenfunctions for structures with pentacovalent nitrogen are identical with the ones set up in the now conventional manner for structures without pentacovalent nitrogen but with semipolar double bonds instead; that the existence of antibonding orbitals seems to be theoretically necessary; and that several of Samuel's further conclusions are either based upon the use of words in unfamiliar senses, or else are erroneous.
A Simple Classical Model Treatment of the Chemical Bond
Authors: Cook Melvin A.
Published: January 2005

A simple method for the determination of bond energies and internuclear distances is developed based on old quantum theory models modified to include the effect of zero-point vibrational energy and a type of resonance (orbital pulsations) assumed to be associated with nuclear vibrational motion. The virial theorem is employed in evaluating the proposed models. The method is applied to the hydrogen molecule and the ``molecule ion'' (H2+). Excellent agreement with experiment is achieved. A possible correlation of the old quantum theory and wave mechanics is indicated.
The Statistical Thermodynamics of Multicomponent Systems
Authors: McMillan William G. , Mayer Joseph E.
Published: January 2005

Distribution functions, Fn(z, {n}), for multicomponent systems are defined proportional to the probability density that n molecules in an infinite isothermal system of fugacity set z will occupy the configurational coordinates symbolized by {n}. All thermodynamic functions may be obtained as certain sums of integrals of these distribution functions. These sums are always convergent, but impractically slow in convergence for numerical use without further transformation. In particular, the grand-partition function, exp [VP(z)/kT], may be expanded in a power series in the fugacities z with coefficients given by integrals of the distribution functions Fn(0, {n}) at the fugacity set 0. As has been previously demonstrated for one component systems, this is shown to be a special case of a more general relation permitting the calculation of the distribution functions (and therefore the thermodynamic functions) for one fugacity set from those at another set. The function —kT ln Fn(z, {n}) is the potential of average force, Wn(z, {n}), of n molecules at the fugacity set z; at zero fugacities, the potential of average force is simply the potential energy. When only short range forces are present, by employing the procedure previously used for the imperfect gas, the integrals of the distribution functions may be simplified to integrals of lower order which become the coefficients in such expressions as the power-series expansion of the pressure increment in terms of the fugacity increments. These series have the advantage of a much higher rate of convergence than those involving integrals of the distribution functions, themselves; however, they do not converge when the initial and final fugacity sets bridge a phase transition. The general equations are applied to the imperfect multicomponent gas, to isotopic gas mixtures, and to condensed systems with the variables converted to the usual activities and activity coefficients. A change of independent variable with a corresponding change in coefficients then permits the evaluation of the pressure increment in terms of the solute concentrations. The equations for osmotic pressure are developed and found to be entirely analogous to those for the pressure of an imperfect gas. Finally, the osmotic pressure in a binary system and its behavior near phase transitions are discussed with emphasis on the critical mixing phenomenon, for which the existence of a region of anomalous first-order transition is shown to be probable.
Deviations from Stoichiometric Proportions in Cuprous Iodide
Authors: Maurer Robert J.
Published: January 2005

The absorption of iodine by cuprous iodide has been studied by means of a quartz micro-balance. At 132.1°C the concentration of absorbed iodine varies as the square root of the pressure of iodine vapor in equilibrium with the sample. The temperature dependence of the the reaction at constant iodine vapor pressure indicates a heat of reaction of 0.24 ev per atom absorbed. The electrical conductivity of cuprous iodide at 132.1°C varies approximately as the 4/3 power of the concentration of the absorbed iodine.
ESR Studies of Triplet States in Plastics: Effect of Temperature on the Spectra
Authors: Thomson Colin
Published: January 2005

The use of polymethylmethacrylate (Lucite) as a host medium for the study of aromatic triplet states by ESR has been explored. The zero-field splitting parameter D* and the lifetime of the triplet state have been measured for a variety of aromatic molecules, and the effect of temperature on these parameters studied in the cases of coronene, triphenylene, and naphthalene.
Electronic Structure of HCl
Authors: Nesbet R. K.
Published: January 2005

An approximate molecular Hartree—Fock electronic wavefunction has been obtained for the ground state of the hydrogen chloride molecule at three closely spaced internuclear distances. This work is of accuracy intermediate between the LCAO approximation and a true molecular Hartree—Fock calculation, since a double orbital basis set is used for the L and M shells of Cl together with extra H orbitals, but 3d basic orbitals are not included. There are 12 basis orbitals of σ symmetry and five of π symmetry. Orbital exponents are determined by variational calculations on atomic chlorine. The computed results include molecular electric dipole and quadrupole moments and their derivatives, estimates of the excitation energy of several low-lying excited states of the neutral molecule and of the positive ion, estimates of the equilibrium internuclear distance of those states that are bound, and identification of the lowest purely repulsive state.
Proton Spin—Lattice Relaxation in Barium Chlorate Monohydrate
Authors: Silvidi A. A. , McGrath J. W. , Holcomb D. F.
Published: January 2005

The protonic spin—lattice relaxation times were measured as functions of orientation and temperature in a single crystal of Ba(ClO3)2·H2O. Pulse methods were used. The proton—proton vector was the axis of rotation of the crystal. Values of T1 were found within the range from 6 to 2400 sec. The orientational dependence was characteristic of intermolecular relaxation of the kind described by Holcomb and Pedersen. The temperature dependence was characteristic of 180° flipping motion of the H2O molecule whose activation energy was 5.0 kcal/mole. Sharp dips appeared in the values of T1 at certain orientations and temperatures. These probably are caused by cross relaxation between the protons and 35Cl nuclei.
Ion—Molecule Reactions in Methanol and Ethanol
Authors: Ryan Keith R. , Sieck L. Wayne , Futrell Jean H.
Published: January 2005

Proton-transfer reactions in the methanol and ethanol systems have been investigated by the techniques of conventional mass spectrometry. Using isotopically substituted methanols, relative transfer probabilities from the carbon and hydroxyl positions of the parent molecule ion are found to be 1.00 and 0.81, respectively. The reaction involving CH2OH+ has also been investigated quantitatively. In ethanol, only C2H4OH+ is found to participate significantly in proton transfer processes. Other secondary ions formed in the high-pressure mass spectrum of methanol and ethanol are reported, as well as the rate constants for the various proton-transfer processes.
NMR in Hydrate Crystals: Correction for Vibrational Motion
Authors: Pedersen Bjo/rn
Published: January 2005

A theoretical analysis of the effect of vibrational motion of the water molecule on the line splitting observed in proton magnetic resonance spectra of hydrates is presented. For an assemblage of magnetically equivalent water molecules, the observed line splitting is given by the Pake formula properly averaged over the motion, 〈(3μ/R3) (3 cos2θ—1)〉. The intramolecular stretching and deformation vibrations are assumed to be uncoupled from the rigid body librational vibrations. The intramolecular vibrations affect the (3μ/R3) term only and are given as 0.980 times the value at equilibrium from an anharmonic model of the vibrations. The angular factor is averaged over the librational oscillations assumed to be of small amplitude and harmonic. The resulting expression is a function of the mean-square amplitude of the rocking, 〈θx2〉, and the twisting, 〈θz2〉, oscillations of the H2O molecule. From a simple model of the librational motion the relative magnitude of 〈θx2〉 and 〈θz2〉 is calculated, and an expression is developed for 〈θz2〉 which only contains the potential barrier for rotation of the H2O molecule and the temperature. From the developed formulas it is estimated that, on the average, the uncorrected intramolecular proton—proton distance is about 5% larger than the equilibrium value. This is mainly due to the zero point motion of the H2O molecule; the line splitting is expected to decrease about 5% going from 0°K to room temperature.

The theory presented has been used in interpreting splitting data obtained from Ba(ClO3)2·H2O rotated about the baxis. The set of line splittings are shown not to follow the simple Pake formula, but the data can be satisfactorily interpreted on the basis of the developed formulas with the numerical values of 〈θx2〉 and 〈θz2〉 available in the literature. A reinterpretation of the experimental results by McGrath and Silvidi is given at the end of the paper. The equilibrium intramolecular proton—proton distances in the lattice-bound H2O molecules are derived from literature data in three hydrates and ice. The values obtained are close to the equilibrium distance found in the isolated H2O molecule, 1.51 Å.
Thermodynamic Properties of Mixtures of Hard Spheres
Authors: Lebowitz J. L. , Rowlinson J. S.
Published: January 2005

We have investigated the thermodynamic properties of a binary mixture of hard spheres (with special reference to the existence of a phase transition) by using the recently obtained exact solution of the generalized equations of Percus and Yevick for the radial distribution functions of such a mixture. The distribution function obtained from the equations of Percus and Yevick is only an approximation and so yields two different pressures, pc and pv, when used, respectively, in the compressibility equation of Ornstein and Zernike and in the equation of state obtained from the virial theorem. Comparisons with machine calculations show that pc is slightly above and pv slightly below the true pressure but that both are close to it. Our results show that the volume change on mixing at constant pressure is negative at all densities and compositions within the fluid phase when it is calculated from pc, but that it becomes positive at high densities when calculated from pv. In neither case is there a separation into two fluid phases. These results are compared briefly with those obtained from other theories of mixtures.
Second Virial Coefficient of Linear Polymer Molecules
Authors: Kurata Michio , Fukatsu Masaaki , Sotobayashi Hideto , Yamakawa Hiromi
Published: January 2005

A variation theory is developed for obtaining a closed expression for the second virial coefficient A2 of linear polymer molecules, which corresponds to the Fixman theory of the excluded volume effect. It is shown that the second virial coefficient of the polymer in good solvents is effectively identical with that of a nonpenetrating sphere whose radius is proportional to the root-mean-square statistical radius 〈S2〉½. In extremely good solvents, A2 becomes a constant independent of molecular weight M. A graphical method is proposed for separate determination of the effective bond length and the polymer—solvent interactions; the method consists of plotting A2M½ against M½. Applications of this method are illustrated by four examples, polystyrene in toluene, isotactic polypropylene in tetralin and in α-chloronaphthalene, and nitrocellulose in acetone. The effective bond lengths obtained are in good agreement with those previously evaluated from the molecular weight dependence of intrinsic viscosity [η], but the polymer—solvent interactions are not. The theoretical value of the ratio A2M/[η] is about 60 in good solvents, which is approximately a half of the ordinary experimental values.

A modification of the variation theory is proposed, which corresponds to Ptitsyn's modification of the Fixman theory and leads to a more plausible value 110 for A2M/[η].

The triple contact term in the perturbation expansion series of A2 is also evaluated. It is found that the expansion of a molecular coil due to the volume effect is somewhat suppressed by intermolecular interactions in the proximity of the second molecule.
Low-Temperature Heat Capacity and Related Thermodynamic Functions of Propylene Oxide
Authors: Oetting Franklin L.
Published: January 2005

The heat capacity of propylene oxide has been determined from 11° to 300°K in an automatic low-temperature adiabatic calorimeter. The melting point of propylene oxide is 161.22°±0.05°K and the heat of melting is 1561.4±1.7 cal/mole. The absolute entropy at 298.15°K is 46.91±0.15 cal/mole·°K) which includes a residual entropy of R ln 2 for the entropy of mixing of the optical isomers.

The third-law entropy of gaseous propylene oxide at 298.15°K is determined from the entropy of the liquid plus literature data on the heat of vaporization, vapor pressure, and the critical constants. This entropy value is in good agreement with the value determined from statistical thermodynamics using literature data on the fundamental vibrational assignment, the internal rotational barrier, and the entropy of mixing.
Energy Degradation of Energetic Atoms and Hot Atom Reactions
Authors: Estrup Peder J.
Published: January 2005

The energy degradation of energetic (hot) atoms can be characterized by a parameter, α, termed the average logarithmic energy loss. In previous gas phase studies of energetic atoms α has been calculated assuming rigid-sphere collisions. It is shown how α may be calculated using more realistic, ``softer'' intermolecular potentials, and the method is applied to the interaction of energetic hydrogen atoms with helium, methane, and hydrogen. Large differences are found between the rigid-sphere values and the soft-sphere values. The previously developed kinetic theory of hot atoms is not affected, but it is shown that the interpretation of hot-atom data depends strongly on which interaction model is assumed. In the case of hot hydrogen atoms the calculations indicate that values for both collisional energy transfers and reaction probabilities may be reduced by an order of magnitude when the soft-sphere model is used.
Association in Vapors of Ionic Salts. A Dimensional Theory
Authors: Blander Milton
Published: January 2005

A dimensional analysis of the statistical-mechanical equations for the association of ionic molecules in the vapor leads to relationships between association constants and the interionic distances. The analysis leads to (a) a law of corresponding states for pure salts, (b) a relation between isothermal association constants and between enthalpies and entropies of association of pure salts, (c) a relation for the estimation of relative association constants in mixed salt vapors. The only parameters required in these relations are the interionic distances. The results of the analyses are in excellent agreement with available experimental data. This suggests the potential usefulness of the theory in making predictions in unknown systems.
Critical Opalescence of a Binary Liquid Mixture, n-Decane—β,β′-Dichloroethyl Ether. I. Light Scattering
Authors: Chu B.
Published: January 2005

Opalescence of a binary liquid mixture, n-decane and β,β′-dichloroethyl ether, has been investigated at and near the critical solution concentration over a range of temperatures near the critical solution temperature in the one phase region. Both components were purified by preparative gas chromatography with estimated organic impurities at less than 1 ppm. Corrections for attenuation and density scattering were briefly discussed. It was found that trace impurities (essentially water) did not affect the over-all molecular interaction range of the principal components. Within the range of the values s/λ [s=2 sin (θ/2),λ= wavelength in the medium, s/λ varied from 1.29×10—4 to 7.46×10—4 Å—1] and temperatures studied, the light scattering data were in good agreement with the Debye theory [J. Chem. Phys. 31, 680 (1959)]. The average range of molecular forces (l) was found to be 13.4 Å.
Gamma-Induced Divalent Dysprosium in Calcium Fluoride
Authors: Fong Francis K.
Published: January 2005

Experiments dealing with photochemical and thermal reactions of dysprosium in calcium fluoride are described. Trivalent dysprosium ions doped in calcium fluoride have been reduced by gamma irradiation at room temperature. The efficiency of reduction of Dy3+ in CaF2 is described in terms of the dosage of gamma irradiation and concentration of the dopant ions. The optimum conditions for the photoreduction are given. The absorption band responsible for the reoxidation of the gamma-reduced dysprosium has been determined. It has been established that high densities of gamma-induced defect sites are necessary for the conversion of the majority of divalent ions to the trivalent state, which may be indicative of the tunneling of Dy2+ electrons to hole centers via the gamma-induced defect centers. The tunneling process is also believed to be responsible for the saturation of local and macroscopic concentrations of Dy2+ ions.

The thermal reoxidation of Dy2+ ions is accompanied by bright luminescence, the spectrum of which resembles that of the photoluminescence of Dy3+ ions. The decay of the thermoluminescent emission bands is nonexponential, and the reaction kinetics fit the description of a second-order reaction. The evaluated activation energy (0.33 eV) is indistinguishable from the energy required for the thermal ionization of holes from V1 centers in alkali halides.
Potential Function for the Stretching Region in Potassium Acid Fluoride
Authors: Ibers James A.
Published: January 2005

A simple potential function is used to fit the observed fundamentals and overtones of the asymmetric and symmetric stretching frequencies of the bifluoride ion in KHF2 and KDF2 and also to account for the difference in mean FHF and FDF bond lengths. The agreement with experiment is good, considering the simplicity of the function and the uncertainties in the data. This potential function is based on a linear symmetric model for the bifluoride ion and there is thus no spectroscopic evidence in favor of an asymmetric model.
Paramagnetic Resonance of Mn2+ in KF
Authors: Veigele W. J. , Tanttila W. H.
Published: January 2005

The Mn2+ hyperfine and superhyperfine interactions in a KF single crystal and powder have been observed at room temperature and sites of cubic and tetragonal symmetry have been identified. A Hamiltonian with the constants D = (—111∓2)×10—4 cm—1, a = (6.5±1)×10—4 cm—1, A55 = (—91±2)×10—4 cm—1, and As = (9.2±0.3)×10—4 cm—1 has been fit to the data. A maximum ion fraction of 10—5 has been estimated from 19F nuclear magnetic resonance linewidth and nuclear spin—lattice relaxation time measurements.
Paramagnetic Resonance of Mn++ in NaN3, KN3, and RbN3
Authors: King Gerard J. , Miller Brian S.
Published: January 2005

The paramagnetic resonance of Mn++ in single crystals of NaN3, KN3, and RbN3 is studied at 9.1 Gc/sec as a function of crystal orientation in the magnetic field. In KN3 and RbN3 containing Mn++ the crystalline electric field is the resultant of a large axial field in the [001] direction plus a small cubic field. The g values for Mn++ in KN3 are g∥ = 1.9961±0.0005, g⊥ = 1.9878±0.0050; and for Mn++ in RbN3 g∥ = 2.0005±0.0005, g⊥ = 1.9971±0.0050. The axial electric field parameter D is —534±3.0 G for KN3 and —278±3.0 G for RbN3 at 25°C. The cubic field parameter a0 is 10±0.5 G for KN3 and 8.7±0.5 G for RbN3. The Mn++ hyperfine coupling constants A and B are —89.7 and —91.1±0.5 G, respectively, in KN3. In RbN3, A and B are —88.0 and —88.9±0.5 G, respectively. The large magnitudes of D, A, and B allow the forbidden ΔM = ±1, Δm = ±1 transitions to be intense. Two inequivalent sites result from the displacement of the Mn++ from a cation site toward a bound nearest-neighbor cation vacancy.

For an unheated crystal of NaN3, the main Mn++ resonance is a single broad line at g = 1.95±0.01. Heating the NaN3 crystal changes this broad line into multiple sets of 30-line spectra. At 25°C these sets of 30-line spectra decay slowly and the original broad line regrows. A similar effect previously found for Mn++ in NaCl has been attributed to mobility of Mn++-cation vacancy complexes. One type of Mn++ spectrum in NaN3 is due to the vacancy-associated complex and another type is due to the dissociated or excited complex. For both types of spectra g∥ = g⊥ = 2.001±0.002 and A≈B = 87±1.0 G. For the dissociated Mn++ complex state the spectrum has axial symmetry about the c axis and D = —240 G. For the vacancy-paired Mn++ spectrum an additional rhombic distortion occurs, and D = —265 and E = +57 G.

The variation of linewidth with temperature is used to show that the KN3 spectra result from charge compensation by vacancy pairing. Additional effects produced by vacancy jumping are noted. Differences between the high-temperature properties of Mn++ in NaN3 and KN3 are related to cation size effects. A low-temperature line broadening of the Mn++ spectrum in KN3 and RbN3 is reported, and the similarity to the Mn++ resonances in solution-grown KCl and KBr is noted.