bluuebunny/crossref_metadata_2025 huggingface dataset:
Force Parameters for Some Nonpolar Molecules on the Exp 6–8 Model
Authors: Barua A. K.
Published: January 2005

Force parameters for the Buckingham-Corner (exp 6–8) potential have been calculated for Kr, Xe, and C2H4. For Kr and Xe, crystal data and second virial data have been used. Crystal data could not be used for C2H4. For these substances the exp 6–8 potential has been compared with the other potential forms. It has been observed that the second virial coefficient is not sensitive enough to show the relative importance of the contributions of the r—6 and r—8 terms to the London attractive potential.
Equation of State and Thermodynamic Properties of Gases at High Temperatures. I. Diatomic Molecules
Authors: Sinanoğlu O. , Pitzer K. S.
Published: January 2005

Methods for evaluating the thermodynamic properties of assemblies of chemically reacting unionized atoms are discussed. The desirability of using the virial coefficients at high temperatures instead of the customary use of the molecular partition functions with anharmonicity corrections is emphasized. The most realistic three-parameter diatomic potential energy function that is available at present, i.e., the Rydberg potential, U/Ue=−(1+b′ξ) exp(−b′ξ) with ξ=(r/re)−1 is selected for the evaluation of the classical second virial coefficient. B(T), T(dB/dT) and T2(d2B/dT2) are obtained as linear combinations involving the five functions: Ak(θ)= ∑ n=1∞[(θe) n/nn+k],[k= —1, 0, 1, 2, and 3, and θ=(Ue/kT)] with only the coefficients that multiply Ak depending on b′. Ak is tabulated for 0.05≤θ≤10. A simple expression for estimating the quantum correction to B(T) is given. The inclusion of the contribution of the higher diatomic electronic states to B(T) is considered. The treatment is applied to sodium (including the 3Σ repulsive state), and B(T) and thermodynamic properties calculated at two temperatures by several methods are compared.
Activity Concept in Radiation Chemistry
Authors: Mahlman H. A.
Published: January 2005

The decomposition of aqueous solutions by ionizing radiations has been interpreted by assuming an initial solvent decomposition into H atoms and OH radicals. Radical recombination gives rise to the observed molecular products H2 and H2O2. Substantiating this hypothesis, it has been demonstrated that reaction of solutes with the radicals depress the yields of the molecular products. The linear dependence of the molecular yields on the cube root of the solute molarity applies very well for dilute solutions of strong electrolytes, i.e., where the molarity and the activity are essentially equal; however, in more concentrated solutions considerable deviation is observed. It is in this region that the activity of an electrolyte manifests itself, and therefore the cube root of the activity is the criterion rather than the molarity.

For this study particular attention was addressed to the depression of hydrogen yields by aqueous sodium nitrate solutions. Alteration of the molecular hydrogen yield was demonstrated by varying the scavenging solute concentration and the activity of the scavenging solute. The addition of three different salts representing uni-univalent, di-univalent, and tri-univalent electrolytes was used to alter the ionic strength of the solutions.
Use of Paramagnetic-Resonance Techniques in the Study of Atomic Oxygen Recombinations
Authors: Krongelb S. , Strandberg M. W. P.
Published: January 2005

A method of making measurements of atomic recombination times with the use of a paramagnetic-resonance spectrometer and its advantages are described. The theory of the paramagnetic-resonance spectrometer applied to these measurements is presented. Methods for using both diffusion and flow systems for determining surface and volume recombination coefficients are analyzed. The operation of the system that was used is illustrated for atomic oxygen recombination. The surface recombination coefficient for oxygen atoms on a quartz surface is shown to be 3.2×10—4 per collision, and the second-order volume recombination coefficient was less accurately determined as 5×1015 cm6 mole—2 sec—1. The measurement of the diffusion coefficient of atomic oxygen is described. The possible application of these methods to further study of reaction rates is discussed.
Hydrates of the Tetra n-butyl and Tetra i-amyl Quaternary Ammonium Salts
Authors: McMullan Richard , Jeffrey G. A.
Published: January 2005

The compounds [(n−C4H9)4N+]nXn−·nyH2O have been prepared where X is F-, Cl-, Br-, CH3CO2-, CrO42-, WO42-, C2O42-, HCO3-, HPO42-, and y is approximately 32. They form an isomorphous crystal series which is tetragonal with a=23.65±0.15 A, c=12.40±0.15 A.

A similar series of the type [(i−C5H11)4N+]nXn−⋅ny′H2O has been prepared where X is F-, Cl-, CrO42-, WO42-, and y′ is approximately 40. They also form an isomorphous group which is orthorhombic with a=12.10±0.10 A, b=21.50±0.15 A, c=12.65±0.15 A.

These compounds are believed to be of the clathrate type, similar in general character to the gas hydrates.
Electrical Conductivity of Single Crystals of MgO
Authors: Mitoff S. P.
Published: January 2005

The electrical conductivity of magnesium oxide at temperatures in the region of 1300°C is observed to depend upon the partial pressure of oxygen surrounding the sample. The conductivity increases at oxygen pressures both higher and lower than 10—5 atmospheres. At this pressure the conductivity is a minimum. This effect is increased as the iron content is increased and is almost absent in the purest samples.

The conductivity is electronic rather than ionic and the number of charge carriers is controlled by the number of lattice vacancies. The dependence of conductivity on oxygen pressure may be satisfactorily explained by changes in stoichiometry and thus lattice defects in magnesium oxide. These changes in stoichiometry are larger when the magnesium oxide is contaminated with a variable valence impurity like iron than when it is pure.

If an explanation based on iron changing valance state is accepted, then it may be demonstrated by an analysis of the chemical equilibria involved that anion deficiencies must appear at low oxygen pressures, cation deficiences at high oxygen pressures, and that all defects must lie close to the variable valence impurity ions.
Probability of Double Ionization by Electron Impact for Neon, Argon, and Xenon
Authors: Morrison J. D. , Nicholson A. J. C.
Published: January 2005

The ionization efficiency curves for the double ionization by electron impact of Ne, Ar, and Xe have been re-examined. It is shown that, near the threshold, the probability of double ionization varies as the square of the excess electron energy. Upper states of the ions are detected and the determination of appearance potentials for such processes is discussed.
Probability of Multiple Ionization by Electron Impact
Authors: Dorman F. H. , Morrison J. D. , Nicholson A. J. C.
Published: January 2005

The ionization efficiency curves for the 3-fold ionization of Ar, and the 3, 4, 5, and 6-fold ionization of Xe have been examined. It is shown that, near the threshold, the probability of n-fold ionization varies as the nth power of the excess electron energy for n = 3 and 4, and probably also for n = 5 and 6. The determination of appearance potentials for such processes is discussed.
Diffusion and Chemical Reaction in a One-Dimensional Condensed System
Authors: Prigogine I. , Bak Thor A.
Published: January 2005

A theory of diffusion processes and chemical reactions based on an integration of the Liouville equation is proposed. A diffusion equation for the probability density in phase space is obtained, and the equation is integrated for a special set of boundary conditions which express that the particle disappears when it reaches a critical energy. It is shown that the rate with which it is annihilated, which is an estimate of the rate of escaping a potential minimum, is characterized by an activation energy, and that the pre-exponential factor is strongly dependent on the frequency for the motion of the particle in the potential minimum. For the special case of an unperturbed potential which is harmonic this can be interpreted as a mass dependence, and it is found that the pre-exponential factor is inversely proportional to m2.
Comparison of Hot and Thermal Reactions
Authors: Magee J. L. , Hamill W. H.
Published: January 2005

Recent experimental studies of the reaction probability of ``hot'' reactions make possible a detailed comparison of collision yields of hot and thermally activated H and CH3 radicals. The theoretical basis of the comparison is first examined using the absolute reaction rate theory. It is found that there is a formal similarity of the rate constant for an energetic complex and a thermally activated complex in terms of a ``temperature'' θ for the former. The concept of ``temperature'' of an energetic complex is considered. The existing experimental data are in agreement with the theory if the assumption is made that a minimal number of degrees of freedom are effective.
Quantum-Mechanical Calculation of the Probability of an Exchange Reaction for Constrained Linear Encounters
Authors: Mazur J. , Rubin Robert J.
Published: January 2005

A numerical procedure suitable for use with a high-speed computing machine is developed for calculating the average quantum-mechanical probability of the exchange reaction BC+A→B+CA for constrained linear encounters at temperature T when BC is initially in its ground or first excited vibrational state. The average refers to the average over the relative momentum frequency distribution of collisions between BC and A at temperature T. The procedure, which involves the numerical solution of the time-dependent Schrödinger equation, is sufficiently general so that any three-atom potential energy surface may be used. Two sample calculations have been performed using a simple potential energy surface. The results of these quantum-mechanical calculations for the average probability of reaction are compared with the corresponding classical quantities which are obtained in an elementary fashion.
Potential Function of Boric Acid
Authors: Pistorius Carl W. F. T.
Published: January 2005

A normal coordinate treatment was carried out for the planar X (YZ)3 molecule (symmetry point group C3h) by means of Wilson's F-G matrix method, using the most general harmonic force field. Ten of the most important force constants of boric acid were determined from existing infrared and Raman data.
C13 Splittings in Proton Magnetic Resonance Spectra. II. Bonding in Substituted Methanes
Authors: Muller Norbert , Pritchard Donald E.
Published: January 2005

We have measured indirect spin-spin couplings between protons and C13 nuclei in a variety of substituted methanes. As found earlier for hydrocarbons, the coupling constants, JC–H, appear to be linearly related both to the percent s character of the carbon atomic orbital participating in the C–H bond and to the bond length. On the basis of the large variations of the JC–H values and of the C–H bond lengths in these compounds we conclude that the state of hybridization of the carbon atom cannot be reliably inferred from the observed, essentially tetrahedral valence angles. This means that the bonds must in many cases be considered as somewhat bent.

We investigated the dependence of the C–H bond hybridization in compounds of type CH3X upon the properties of the substituent group. The results can be correlated on the assumption that the effective electronegativity and the size of the atom directly attached to the methyl carbon primarily determine the hybridization.
Thermionic Properties of Uranium
Authors: Rauh E. G. , Thorn R. J.
Published: January 2005

Thermionic measurements were made on uranium metal in the form of drawn wire and on films of uranium deposited on tungsten by evaporation in ultrahigh vacua. Measurements of the emission current as a function of accelerating potential and of the work function of the bulk material indicated that the surface was never completely freed of oxide. Measurements of the work function and emission constant A as a function of the thickness of the evaporated films showed both φ and A to increase with increasing depth of deposit up to 15 atom layers and to reach constant values of 3.47±0.03 ev and 114±12 amp cm—2 deg—2, respectively, for deposits 15–200 atom layers deep. Qualitative measurements of the ionization potential of uranium by means of surface ionization showed the positive ion current to increase with increasing temperature indicating the ionization potential to be greater than 4.53 ev. The magnitude of the positive ion currents suggested an ionization potential of 4.5–5.0 volts.
Negative Ion Mass Spectra of Hydrocarbons and Alcohols
Authors: Melton C. E. , Rudolph P. S.
Published: January 2005

The complete negative ion mass spectra and relative sensitivity for positive and negative ion formation in various organic compounds are herein reported for the first time. These compounds include methane, the C2— hydrocarbons, n-butane, and all of the alkyl alcohols through the butyls. A limited comparison of the observed ionic patterns with molecular structure and chemical properties manifests a correlation. Relative sensitivities for positive and negative ion formation in these compounds show that formation of positive ions is about four orders of magnitude more probable than formation of negative ions under the conditions used in this study.
Diffusion in Liquids
Authors: McCall David W. , Douglass Dean C. , Anderson Ernest W.
Published: January 2005

Self-diffusion coefficients have been measured for water, nitromethane, acetone, benzene, cyclohexane, isopentane, and neopentane. Temperature and pressure dependences have been determined for nitromethane, acetone, cyclohexane, and isopentane. The temperature dependence has been determined for neopentane and the pressure dependence has been determined for water and benzene. The results are discussed in terms of a semiempirical theory for transport in liquids and it is shown that semiquantitative predictions of self-diffusion, viscosity, and thermal conductivity coefficients can be made.
Ion Binding by Spherical Polyelectrolyte Molecules
Authors: Wall Frederick T. , Cote James A. , Rucker Sylvia M.
Published: January 2005

Additional numerical solutions have been obtained for the Poisson-Boltzmann equation applied to spherical polyelectrolyte molecules. The results now reported deal with cases involving smaller charge densities and smaller polyion radii than heretofore. Calculations have also been made for a model of a polyelectrolyte immersed in a sea of multi-multivalent electrolyte. In addition to computing the electrical potential in and about the polyion, the extent of counter-ion binding has also been calculated. It is found that the binding of counter-ions is determined principally by the charge of the ion of sign opposite that of the polyelectrolyte and that it depends very little on the magnitude of the charge of the ion with sign like that of the central sphere.
Electron Affinities of Some Halogen Molecules and the Charge-Transfer Frequency
Authors: Person Willis B.
Published: January 2005

In an attempt to fix the value of the vertical electron affinity of the iodine molecule EI2v the potential curve for I2— has been constructed from semiempirical considerations. From this curve the value of EI2v is estimated to be 1.7±0.5 eV, in apparent contradiction to the value around 0 eV indicated by the electron-capture experiments. It is suggested that the electron-capture experiment may measure the vertical energy for capture to give an excited state of the I2— ion, thus explaining the discrepancy.

Having fixed the value for EI2v, the relationship predicting the charge transfer frequency for iodine complexes is reexamined critically. By fitting curves to the data for three different types of complexes (π donors with I2, amine donors with I2, and complexes with I atoms), three sets of empirical constants required to force the fit are determined. An attempt is then made to calculate these sets of constants from a priori considerations. The success of this treatment supports the general theory, indicating especially that no major terms have been omitted from the estimation of the energy difference, W1—W0. Furthermore, the general argument supports the value of EI2v obtained in the earlier part of the paper as well as the reliability of the estimation of the other parameters. The analysis supports the perpendicular model for the geometry of the complexes between I2 and π donors.

Finally, similar analyses are presented for other halogens; Br2, Cl2, and ICl. Estimates of the vertical electron affinity for these halogens from the empirical potential curves agree reasonably well with estimates from the charge transfer frequency, in support of the results for I2.
Effects of N15 on the Nuclear Quadrupole Resonance of N14 in Solid N2
Authors: Haigh Paul J. , Scott Thomas A.
Published: January 2005

Solid nitrogen, which consists of 99.6% N14 (I=1) at natural abundance has previously been observed to exhibit a single, strong pure quadrupole resonance line in the α phase below 35.5°K. This has been discussed by Scott in the first of this series of papers. When the sample is enriched with N15 (I=½) the N14 resonance is split into two distinct lines. For an approximately equal isotopic mixture, the splitting is 8.2 kc at 4.2°K and decreases with increasing temperature. Using the Bayer—Kushida theory as a basis, the two resonance frequencies may be attributed to the presence of two types of molecules N14–N14 and N14–N15. The former molecule has a resonance frequency close to that of pure N214 whereas the latter molecule, being heavier and thus vibrating with a smaller amplitude, has the higher frequency. The data are discussed on the basis of present theoretical and experimental understanding.
Urey—Bradley Force Constants of Methanol
Authors: Zerbi Giuseppe , Overend John , Crawford Bryce
Published: January 2005

Urey—Bradley force constants of methanol have been calculated by a least-squares technique using vibrational-frequency data from CH3OH, CH3OD, CD3OH, and CD3OD. The results show that the vibrational assignment recently proposed by Margottin—Marclou is consistent with the Urey—Bradley field, whereas that of Falk and Whalley is not.
Rotational, Vibrational, and Electronic Energy Transfer in the Fluorescence of Nitric Oxide
Authors: Broida H. P. , Carrington Tucker
Published: January 2005

A sharp emission line of ionized cadmium from an electric discharge excites NO molecules to the K′=13 rotational level of the v′=1 vibrational level of the A 2Σ+ electronic state. Steady-state fluorescence has been observed from this level and from neighboring levels populated by collisional interaction between the excited and added inert molecules. Cross sections have been measured in He, Ar, H2, N2, NO, and CO2 for electronic deactivation to the ground X2II state, for vibrational deactivation to the v′=0 level of the A 2Σ+ state, and for rotational exchange in the A 2Σ+ state. It has been established that rotational transitions having changes in rotational quantum number greater than unity take place with high probability, contrary to the optical selection rule.
Viscosity of Nitrogen, Helium, Neon, and Argon from —78.5° to 100°C below 200 Atmospheres
Authors: Flynn G. P. , Hanks R. V. , Lemaire N. A. , Ross J.
Published: January 2005

A new capillary-flow viscometer has been developed for the measurement of the absolute viscosity of gases as a function of temperature and pressure. In the viscometer a steady flow of gas is maintained through a capillary of known dimensions, and the pressure difference developed across the capillary is measured as a function of the flow rate. From these measurements there are obtained by extrapolation to zero flow rate the absolute viscosity and information on the deviation from Poiseuille flow.

The viscosities of nitrogen, helium, neon, and argon have been determined in this viscometer from —78.5° (—50° for helium and neon) to 100°C and up to 200 atm. The experimental results are believed to be accurate within 0.1%. Agreement with previous results, where available, is generally satisfactory. All the viscosity data for each gas can be represented adequately by the sum of two functions, one dependent on temperature only, the other dependent on density only.
Pressure Dependence of the NMR Chemical Shifts in Cesium and Rubidium Halides
Authors: Baron Robert
Published: January 2005

The chemical shifts, line shapes, linewidths, and line intensities have been measured as a function of pressure and crystal structure from 1 to 104 kg/cm2 at room temperature for both metal and halide nuclei in alkali halide pressed powder pellets. Measurements were made on Rb87, Cs133, Cl35, Br81, and I127 in RbCl, RbBr, RbI, CsBr, and CsI. The chemical shifts become more paramagnetic with increasing pressure within any one phase. At the transition from NaCl to CsCl-type crystal structure exhibited by the rubidium halides, the Rb87 chemical shifts become less paramagnetic, and the halide chemical shifts become more paramagnetic. As usual, the magnitude of the effects increases with increasing atomic number. The correction of the chemical shifts for second-order quadrupole interactions is discussed. The data are compared to chemical shifts calculated from a covalent model of Yosida and Moriya, and an overlap model of Kondo and Yamashita. The overlap model is found to give reasonably good agreement with the data if it is modified to include next-nearest neighbor effects in order to explain the behavior of the chemical shifts at the transition. The covalent model is by itself inadequate to explain the data, but an improvement in the agreement with the data is possible if the covalent model is used to modify the overlap model. However, the predicted chemical shifts and their changes with pressure for the CsCl-type crystal structure are still too large compared to the data. The absolute values of the chemical shifts are in doubt; Itoh and Yamagata have advanced the possibility that the ion in dilute aqueous solution, which is used as the reference from which the chemical shift is measured, has a nonzero chemical shift with respect to the isolated ion. This difficulty is avoided by comparing with the models only relative changes in the chemical shifts. Further evidence is advanced for the existence of this shift.
Diffusion Coefficients of the Systems CO–CO and CO–N2
Authors: Amdur I. , Shuler L. M.
Published: January 2005

Self-diffusion and mutual diffusion coefficients in the range 195° to 373°K have been measured for the isostere systems, CO–CO and CO–N2. The self-diffusion coefficients are consistently higher than the mutual diffusion coefficients, with differences two- to fourfold greater than the experimental error. On the assumption that the classical Chapman—Enskog transport relations are applicable, parameters have been obtained for intermolecular potentials of the Lennard-Jones (12–6) and the exp-six types.

Parameters derived from diffusion measurements have been compared with those obtained from measurements of viscosity, compressibility and crystal properties. It was not possible, for either system, to reproduce both the transport and equilibrium properties with a single set of parameters. It is concluded that the failure may be attributed mainly to the use of average spherically symmetric potentials instead of potentials which are functions of both relative molecular orientation and internuclear separation.
Proton Magnetic Resonance Study of the Structure of Two Tutton's Salts
Authors: Chidambaram R. , Rao C. Raghavendra
Published: January 2005

Proton magnetic resonance spectra of single crystals of two Tutton's salts, K2Zn(SO4)2·6H2O and K2Mg(SO4)2·6H2O, have been studied and the orientations of the water molecules in the structure have been determined. Using the heavy-atom structure of (NH4)2Mg(SO4)2·6H2O as determined by x-ray diffraction, a system of hydrogen bonds between the water and sulfate oxygens in Tutton's salts has been proposed. It appears that the x-ray structure needs considerable refinement.
Molecular Interaction and Linewidth of Asymmetric Molecule SO2. I. SO2–N2 Collisions
Authors: Krishnaji  , Chandra Suresh
Published: January 2005

The linewidth of the 91,9→82,6 transition of sulfur dioxide broadened by nitrogen has been measured at different pressures using a double modulation video spectrograph. The measured linewidth for the SO2–N2 collision is 4.19 Mc/mm. The hard-sphere collision diameter corresponding to this is 5.68 Å as compared to the kinetic collision diameter of 4.0 Å. The result has been interpreted on the basis of Anderson's theory assuming a dipole—quadrupole interaction to be responsible for the width. The quadrupole moment of nitrogen so evaluated is equal to 2.79×10—26 esu. The temperature dependence of the linewidth parameter has also been calculated and it has been found that for the temperature range 340°—600°K, Δν varies as T—0·78 and for the temperature range 195°—340°K, Δν varies as T—0·86.
Raman Spectra of Aqueous Solutions of Indium Sulfate, Nitrate, and Perchlorate
Authors: Hester Ronald E. , Plane Robert A. , Walrafen George E.
Published: January 2005

For a series of metal-ion sulfate solutions investigated, only In3+ showed Raman spectral evidence of association with SO4=. The evidence consisted of the appearance in indium sulfate solutions of four new polarized lines in the Raman spectrum. Three of these were accounted for in terms of C3v symmetry for the bound sulfate ion and the assignment thus was: v1(A1)=1125 cm—1, v2(A1)=1000 cm—1, v3(A1)=650 cm—1. The fourth new line, at 255 cm—1, was also present (at 270 cm—1) in indium nitrate solutions and thus assigned to an In–O stretching mode. Raman intensity data, particularly in mixed indium sulfate—indium perchlorate solutions, verified the new species as an indium—sulfate complex; however, these data did not permit a decision between the presence of InSO4+, In(SO4)2—, or a mixture of the two. The fact that the 255 cm—1 line was found to be highly polarized suggested that a linear In(SO4)2— species might be of major importance. Finally, all indium solutions, even those with ClO4— as the only anion, showed a broad polarized band near 400 cm—1 which probably resulted from hydrated In3+.
Strong-Field Stark Effect of Asymmetric-Top Rotator
Authors: West Burnell G. , Mizushima Masataka
Published: January 2005

A computer program is designed to calculate the Stark effect of lower rotational energy levels of an asymmetric top rotator with an arbitrary asymmetry parameter. Instead of using the perturbation expansion formula the program obtains eigenvalues of the secular equation with external electric field. With the available computer capacity, this means calculating up to about 10th order perturbation terms. The procedure is suitable and the only practical way to calculate Stark effect with strong field. Some results on the H2S and the SO2 molecules are shown.
Pressure-Induced Shifts of Infrared Lines due to Polar Molecules
Authors: Plyler Earle K. , Hirschfeld M. A. , Jaffe J. H.
Published: January 2005

The pressure-induced shifts by dimethyl ether of the infrared lines of the 2–0 band of hydrogen chloride have been measured. The shifts in the R branch are similar to those produced by the noble gases, but the shifts for all the J values in the P branch are negative. Large shifts (4×10—2 cm—1 per atm) are observed for P1 and P2 and then the shifts decrease rapidly reaching a minimum at P4. For larger J values the shifts become large again. A qualitative explanation of this type of shift is given.
Gas-Phase Radiolysis of Isobutane
Authors: Borkowski R. P. , Ausloos P. J.
Published: January 2005

The radiolysis of (CH3)3CD—I2 and (CH3)3CH–(CD3)3CD–I2 mixtures has been investigated as a function of pressure (0.2 to 75 cm) and temperature (30° to 225°C). Propane, which is the major product, is mostly formed by a hydride transfer reaction such as sec−C3H7++(CH3)3CH→C3H8+(CH3)3C+. From the distribution of the isotopic propanes produced in the radiolysis of (CH3)3CD it can be concluded that hydrogen atoms in the sec-propyl ion are randomized in various degrees depending on the pressure of isobutane. Ethane is mainly formed by a hydride transfer reactionC2H5++(CH3)3CH→C2H6+C4H9+.. Two distinct processes lead to the formation of ethylene, (a) molecular elimination from isobutane and (b) reaction of vinyl ions with isobutane. The effect of xenon, krypton, and argon on the product distribution and the randomization of the sec-propyl ion is discussed in some detail.
Kinetic Theory of Nonspherical Molecules. V
Authors: Curtiss C. F. , Dahler J. S.
Published: January 2005

A generalized Boltzmann equation for fluids composed of molecules with arbitrary internal degrees of freedom and which interact according to classical mechanics through arbitrary, noncentral pair-additive forces is developed using techniques similar to those used by Hollinger and Curtiss. Several special cases are considered: (1) molecules which interact only through impulsive forces of repulsion, (2) molecules for which the only internal degrees of freedom are rotational degrees, and (3) a combination of both special cases. The third special case leads to a Boltzmann equation appropriate to a fluid composed of rigid nonspherical molecules, and provides a firm basis upon which to develop a formal kinetic theory. As a special example we consider a gas made up of rigid, convex, nonspherical molecules with symmetric-top mass distributions. Rigorous equations of hydrodynamics are presented for such a fluid. It is shown that the kinetic theory of a dilute multicomponent system of these molecules is formally the same as that for the loaded-sphere system recently studied by Dahler and Sather. Finally, it is shown how the methods developed by these authors can be applied to the problems of solving the Boltzmann equation and of calculating the transport coefficients for the nonspherical molecular species considered in the present paper.
Kinetic Theory of Loaded Spheres. I
Authors: Dahler John S. , Sather Norman F.
Published: January 2005

A rigorous formalism is developed for the theory of transport in fluids composed of loaded-sphere molecules. From this theory formulas are derived for the fluxes of mass, linear momentum, internal or spin angular momentum, and energy. The existence of inverse collisions is established and used to prove a weak form of the Boltzmann H theorem. Finally, we present a kinetic theory for dilute multicomponent mixtures of loaded spheres and derive explicit formulas for the phenomenological gas transport coefficients. Since the only critical assumption imbedded within this treatment is that of molecular chaos, it appears that our theory for loaded spheres shares the ``rigor'' of the Chapman—Enskog theory for structureless molecular species. Detailed numerical calculations of transport coefficients will be communicated in a subsequent paper of this series.
Molecular Reorientation in Liquids. I. Distribution Functions and Friction Constants
Authors: Steele William A.
Published: January 2005

The orientational motion of rigid molecules in liquids obeying classical mechanics is considered. The equations of motion of these systems are Euler's equations. It is assumed that the torque on a molecule can be represented by a friction term proportional to angular velocity plus a randomly fluctuating torque. It is then shown that the equations of motion for a spherical top have solutions of the form of the solutions of the Langevin equation. The components of the diagonalized rotational friction constant tensor are given as time integrals of the autocorrelation functions of the components of the angular velocity and an approximate expression is obtained which gives the rotational friction constants in terms of ensemble averages of the angular derivatives of the intermolecular potential function. A differential equation is derived for the time-dependent distribution function for the Eulerian angle displacements. The solutions of this equation can be written in terms of the solutions of the Schrödinger equation for the asymmetric top multiplied by exponentially decaying functions of time. Molecules possessing elements of symmetry in their interaction potential functions are considered, and it is shown that the components of the rotational friction tensor approach zero in these systems and that the rotational motion over relatively long time intervals is then determined by the inertial terms in the equation of motion. The application of these results to the theory of rotational nuclear magnetic and dielectric relaxation in liquids is briefly discussed.
Molecular Reorientation in Liquids. II. Angular Autocorrelation Functions
Authors: Steele William A.
Published: January 2005

The normalized angular autocorrelation functions which appear in the theories of rotational nuclear magnetic and dielectric relaxation are considered in the light of the results presented in Paper I of this series. The time-dependent spherical harmonics in the equations for the autocorrelation functions are written as functions of the molecular Eulerian angular displacements. The time dependence of the autocorrelation functions is calculated using the distribution functions obtained in I, and it is shown that the results are strongly dependent upon the magnitude of the components of the diagonalized rotational friction tensor. If all components are large and unequal, five relaxation times appear in the autocorrelation function for nuclear relaxation and three times appear in the function for dielectric relaxation. If one or more of the components are small, the autocorrelation functions are found to be dependent upon the inertial terms in the molecular equations of motion. Autocorrelation functions are evaluated in the case that all the components of the rotational friction tensor of a spherical top are zero, and an approximate equation for the autocorrelation function is suggested for systems in which dynamical coherence is the predominant factor in the reorientational motion. These equations are Gaussian functions of time, with time constants which depend only upon the inertial properties of the molecule. In principle, the results of this paper, together with the results of I, allow one to compute rotational relaxation behavior in liquids from molecular interaction potential functions.
Crystal Structures of KCuCl3 and NH4CuCl3
Authors: Willett Roger D. , Dwiggins Claudius , Kruh R. F. , Rundle R. E.
Published: January 2005

The crystal structures of the isomorphous garnet-red copper salts, KCuCl3 and NH4CuCl3, have been determined. Each compound contains discrete, planar, Cu2Cl6= dimers. These dimers are stacked above each other along the crystallographic a axis. The cation exhibits a ninefold coordination.

KCuCl3 is antiferromagnetic below 30°K. Both KCuCl3 and NH4CuCl3 are pleochroic with maximum visible absorption when the electric vector is parallel with the Cu–Cu vector of the dimer.
Radiolysis of Propane-d8 in the Presence of Organic Compounds Other Than Hydrocarbons
Authors: Sandoval I. B. , Ausloos P. J.
Published: January 2005

The gas phase radiolysis of propane-d8 has been investigated in the presence of dimethylmercury, azomethane, acetone, methyliodide, methanol, nitromethane, and methylamine. The cross section of the hydride-transfer reactionC2D5++RH→C2D5H+R+is, in all cases, at least 10 times smaller than that of the reactionC2D5++C3D8→C2D6+C3D7+.Evidence for the occurrence of the proton-transfer reactionC2D5++RH→C2D4+RHD+has been obtained. For the mixtures containing methanol, the cross section of this proton-transfer reaction is about 50 times that of the hydride-transfer process. Approximate values of G (CH3+) have been determined for most of the additives.
Computations to Evaluate Dewar's Split P-Orbital (SPO) Method
Authors: Saturno Antony F. , Joy Hubert W. , Snyder Lawrence C.
Published: January 2005

The split p-orbital (SPO) wavefunction derived from the single determinant | 2pz2p̄z | corresponding to the singlet state in which a single 2pz orbital is doubly occupied, correlates the electronic motion so that the electrons always occupy opposite lobes of the 2pz orbital. This SPO singlet wavefunction may be written as 2—½{— | 2pz2p̄z | + | | 2pz | | 2p̄z | |} and is the lowest-energy linear combination of this pair of two-electron determinants. In this two-electron context, the triplet function | 2pz | 2pz | | is degenerate with the SPO singlet. In order to test the persistence of this qualitative picture when occupied sigma core orbitals are explicitly included, we have performed analogous rigorous computations on the 1s22s22pz2 nonstationary state of carbon, using corresponding determinants | 1s1s̄2s*2s̄*2pz2p̄z | and | 1s1s̄2s*2s̄* | 2pz | | 2p̄z | |, which include occupied 1s and 2s core orbitals. The lowest-energy singlet linear combination is found to be almost entirely composed of the first determinant and corresponds to a conventional, rather than an SPO wave-function. The triplet determinant | 1s1s̄2s*2s̄*2pz | 2pz | | is of 2.5 a.u. higher energy than the lowest singlet. While these calculations do not support the SPO method as stated for this one-center problem, it is possible that computations with other basis functions will suggest vertical correlation of pi-electronic motion.
Boundary Effect Corrections for the Thomas—Fermi Atomic Interaction Potential
Authors: Townsend J. R. , Keller J. M.
Published: January 2005

The electronic energies of a neutral diatomic molecule with noninteracting electrons are calculated by two methods: first, using solutions of Schrödinger's equation for a hydrogenlike molecular ion; second, using the assumption of a slowly varying potential, characteristic of the Thomas—Fermi method. Comparison of these solutions serves both as a test of the TF method and as a means of correcting partially for the TF shortcomings. Based on the success of this method as applied by Scott to the TF atom, the corrected interaction energy is believed correct to within 20% for separations up to Z—⅓ Å. Of qualitative interest is the prediction of bound molecules at large separations except for the rare gases which remain repulsive.
Multistage Radiative Transitions in CaF2:Er3+
Authors: Pollack S. A.
Published: January 2005

The theory of multistage transitions is reviewed. A brief account of the fluorescence spectrum of CaF2:Er3+ 0.1% concentration of Er3+ ion per mole is given. The principal regions of excitation are around 2550 and 3750 Å, which produce basically different spectra. The fluorescence groups excited with 2550-Å monochromatic radiation are tabulated. Most of the groups are found to be parts of multistage radiative relaxation processes. The stages of these mostly two-stage processes are identified, and the decay curves of two-stage transitions are analyzed. The nonexponential decay curves of the second-stage transitions are resolved into the difference of two exponentials, and the time constants are determined. The agreement with the time constants obtained for the first and the second stages excited separately is satisfactory. The occurrences of the maxima of the decay curves for the second-stage transitions are in agreement with calculations. The temperature and concentration dependence of the transition probabilities is investigated. The decay curves for transitions excited with several wavelengths are analyzed. All experimental results are accountable by the theory.
Solution of Plane Ising Lattices by the Pfaffian Method
Authors: Hurst C. A.
Published: January 2005

The partition function for the Ising problem for a general class of plane lattices is evaluated exactly using the Pfaffian method. A classification of plane lattices in terms of basic lattices with vertices decorated by sublattices is given, and the most general class which can be solved by the Pfaffian method described. The solutions given in this paper are for the special case when neighbouring lattice points of a basic rectangular lattice are connected by single bonds only. All of the exact solutions known so far are obtained as special cases. The critical points are defined as singularities of an analytic function and equations to determine their location are found. The derivatives of the partition function are evaluated in terms of elliptic integrals.
Investigation of a Fragmentation Model for n-Paraffins
Authors: Schug John C.
Published: January 2005

A fragmentation model is postulated for the interpretation of n-paraffin mass spectra. It is assumed that primary dissociations of molecule ions yield fragment ions containing at least half the total number of available carbon atoms. Any fragment ions retaining sufficient excitation energy can dissociate further, with the same product size limitations as in the primary processes. At each step, all possible dissociations are assumed to be in competition. Rate constants are calculated by the statistical theory. Breakdown curves are given for n-decane, and described for other cases. The model can successfully account for observed patterns, their dependence upon the ionizing voltage, and the occurrence of several metastable ion peaks. However, other expected metastables do not appear, the requisite internal energy distributions cannot presently be reconciled, and the calculated amounts of fragment-ion labeling from C13-enriched molecules are in disagreement with experimental results.
Corrosion of Tungsten and Iridium by Field Desorption of Nitrogen and Carbon Monoxide
Authors: Mulson J. F. , Müller E. W.
Published: January 2005

By using an ultra-high-vacuum processed field ion microscope, two atomic adsorption sites of nitrogen and carbon monoxide were observed on tungsten and iridium surfaces. Field desorption of a nitrogen atom from a single site also removes the underlying tungsten or iridium atom. Field desorption of an adsorbed nitrogen molecule does not corrode the iridium substrate. Corrosion of both metals by field desorbing carbon monoxide is attributed to oxygen dissociated from the molecule by electron impact.
YH3 and YD3: Heat Capacities and Thermodynamic Functions from 15° to 350°K and Infrared Absorption Spectra
Authors: Flotow Howard E. , Osborne Darrell W. , Otto Klaus , Abraham Bernard M.
Published: January 2005

The heat capacities of YH3 and YD3 were determined in an adiabatic calorimeter from 15° to 350°K. The heat capacity, entropy, enthalpy, and Gibbs free-energy function for YH3 at 298.15°K are 10.363±0.021 cal deg—1 mole—1, 10.019±0.020 cal deg—1 mole—1, 1613.3±3.2 cal mole—1, and —4.608±0.009 cal deg—1 mole—1, respectively. The corresponding quantities for YD3 are 13.727±0.028, 12.028±0.024, 2024.8±4.0, and —5.237±0.010.

The infrared absorption spectra of YH3 and YD3 were taken in the range 400 to 4000 cm—1. Maxima in the absorption bands of YH3 were observed at 1295, 920, and 640 cm—1 and in the absorption bands of YD3 at 1295/√2, 920/√2, and 640/√2 cm—1. A reasonable assignment of these frequencies to Y—H and Y—D vibrations satisfactorily accounts for the difference between the heat capacities of YH3 and YD3 in the temperature range 50° to 350°K. The lattice parameters as determined by x-ray diffraction for the hexagonal close-packed trihydrides were a0 = 3.672±0.002 Å and c0 = 6.625±0.018 Å for YH3 and a0 = 3.659±0.002 Å and c0 = 6.586±0.019 Å for YD3.
Use of Catalytic Probes to Determine Atom Concentrations and Atom Diffusion Coefficients
Authors: Morgan J. E. , Schiff H. I.
Published: January 2005

A simple analysis is presented for the perturbation of a stream of partially dissociated gas by a catalytic probe capable of completely removing all the atoms from the stream. The results of this analysis were confirmed by experiments on discharged O2, which showed that for linear flow rates of several meters per second the atom concentration reaches 99% of the unperturbed value within 2.5 cm upstream from the probe. It is shown that such a probe can be used to measure atom concentrations, since the flux to the probe remains finite even though the atom concentration at its surface is virtually zero. No appreciable errors are introduced into relative concentration measurements required to obtain first order rate constants. Under suitable experimental conditions, absolute concentrations can be obtained which are negligibly different from the unperturbed values regardless of the order of the recombination processes. A method is described for using such a probe to obtain accurate values of atomic diffusion coefficients which does not require accurate knowledge of heterogeneous or homogeneous recombination rates.
Rectification Phenomena in Polycrystalline Phthalocyanines
Authors: Haak Fred A. , Nolta James P.
Published: January 2005

Rectification was observed on polycrystalline samples of metal-free, copper, nickel, and molybdenum phthalocyanines when these materials were sandwiched between different metal electrodes. The presence of a small amount of a liquid polar impurity proved essential for rectification, and it is suggested that the observed rectification is caused by the formation of an ionic space-charge barrier in the vicinity of the least noble electrode. The highest rectification ratio observed was 500 and was obtained with copper phthalocyanine between a platinum and a silver electrode and also between a silver and an aluminum electrode. The effects of temperature, electrode material, and electrode size on the rectification ratio are given.
1–0, 2–0, 3–0, Absorption Bands of Dense Forms of Pure CO and Its Solutions in N2 and Ar
Authors: Vu H. , Atwood M. R. , Vodar B.
Published: January 2005

The first overtone and the second overtone bands of pure CO as well as the first overtone band of CO in solution in the gaseous, liquid, and solid states of N2 and Ar have been studied. The method for obtaining under pressure long lengths of transparent solids is described. A principal band due to C12O16 and a weak satellite due to the isotopes C13O16 and C12O18 have been found, and displacement of the maximum of the principal band and this satellite have been measured. The results are compared with those found for the fundamental by the condensed matrix method. The form of the band, in particular, its half-width, as a function of temperature and density is discussed.