bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectroscopic Study of the Monotropic Forms of Monochloracetic Acid
Authors: Barceló José R. , Jorge M. Pilar , Otero Clara
Published: January 2005

Monochloracetic acid (CClH2–COOH) is a trimorphic substance. Only one of the three forms is stable, viz.: the α form; whereas the β and γ forms are metastable. The infrared spectrum of the forms α and β has been studied; that of the γ form has not been studied because of its extreme instability.

It has been seen that the spectrum of the α form is different from that of the β form. The fundamental frequencies of monochloracetic acid have been assigned, bearing in mind the assignments made by the present authors in another paper for di- and trichloracetic acids.

This assignment makes it possible to determine that the displacements which are observed when passing from form α to β chiefly affect the frequencies bound up with the carboxyl group and more especially those in the OH group. This has been confirmed by the preparation of the deuterated derivatives which likewise present themselves in α and β forms, the same relative differences in frequencies being observed.

It is inferred from this study that the two crystalline forms differ in the structure of the intermolecular dimers (or polymers). The α form is the conventional dimer with two hydrogen bonds. In the β form this intermolecular bond is probably not the double hydrogen bond, since the OH groups show a greater mobility.
Dipole Moment of Ammonia-Borane
Authors: Weaver J. R. , Shore S. G. , Parry R. W.
Published: January 2005

The dipole moment of ammonia-borane, H3NBH3, has been measured as 4.9 debye units in dioxane solution; the results are discussed briefly.
On Das' Theory of Nuclear Magnetic Resonance in Solids
Authors: McGrath J. W. , Silvidi A. A.
Published: January 2005

Das' theory developed the effect of vibratory rotary motion of water molecules in crystalline hydrates on the resonance spectra of the protons. Limitations on applicability of his theory are discussed. The theory is extended to the general case and a further effect on spectra is obtained. This effect is dependent upon the orientation of the proton-proton axis within the crystal, the orientation of the crystal in the magnetic field, the temperature and the height of the twofold potential barrier containing the water molecule. Partial experimental support of the theory is cited. Two methods for measuring proton-proton separations that do not require Das' theory corrections are described. A method for measuring the height of the potential barrier is described.
Enhancement of Infrared Absorption Bands of Charge Transfer Complexes
Authors: Ferguson E. E. , Matsen F. A.
Published: January 2005

An enhancement of infrared absorption bands is shown to be inherent in charge-transfer theory due to change in vertical ionization energy or change in vertical electron affinity during the course of molecular vibration. A semiquantitative calculation of the intensity enhancement of the symmetric ring stretching vibrational mode of benzene in the benzene-iodine complex agrees well with the experimentally observed value.

This result shows that previous investigators' assumptions of charge-transfer complex asymmetry, based on observed infrared absorption bands may not be valid.
Effects of Hydrostatic Pressure on the Intensity of the Singlet-Triplet Transition of α-Chloronaphthalene in Ethyl Iodide
Authors: Robertson W. W. , Reynolds R. E.
Published: January 2005

The extinction coefficient of the singlet-triplet transition of alpha-chloronaphthalene in ethyl iodide is found to increase almost linearly with the density of the compressed mixture. Study of a 1 : 2 volume ratio of these components over a pressure range from 1 to 3644 atmospheres resulted in about a two fold increase in light absorption, with little other changes in band envelope. No increase in absorption coefficient was obtained for pure liquid alpha-chloronaphthalene subjected to comparable increase in hydrostatic pressure. The increase in extinction coefficient is attributed to the increase in collisional frequency resulting from the increase in concentration of the constituents and the corresponding decrease in the liquid ``cage'' dimensions with increased density.
Solubility of Helium and Neon in Liquid Argon. An Approximation to the Entropy of Lattice Vacancy Formation in Liquid Argon
Authors: Karasz F. E. , Halsey G. D.
Published: January 2005

The solubilities of helium and neon in liquid argon have been measured over the temperature range 83.9 to 87.5°K. The observed heat of solution for helium is 1520 cal/mole and for neon is 390 cal/mole. These data have been analyzed by means of a modified LJD treatment to yield an entropy for lattice vacancy formation of approximately 24 eu.
Nuclear Resonance Study of Structure and Molecular Motions in Some Cobalt Complex Salts
Authors: Murray G. R. , Waugh J. S.
Published: January 2005

Line widths and second moments of the proton and F19 resonances in Co(NH3)6X3 (X=Cl, Br, I, NO3, BF4, PF6) were measured from 90° to 400°K. In the first four, unusual and very broad (∼200°K) line-width transitions were observed. These are interpreted by postulating crystal structures containing nonequivalent sites for Co(NH3)6+++ ions in relative abundances 2:1, 1:1, 1:1, and 2:1, respectively. This interpretation was verified in one case by x-ray diffraction. Co(NH3)6(BF4)3 showed a normal line-width transition which is interpreted both by the usual correlation theory and by a very detailed analysis to give ΔE≅12 kcal/mole and τ0≅10—14 sec. At 90°K rapid reorientation of —NH3 groups and of BF4— and PF6— ions occurs in all of these salts. At 330°K and above, rapid tumbling of Co(NH3)6+++ ions occurs.
Excitation of Molecular Vibration on Collision
Authors: Salkoff Morris , Bauer Ernest
Published: January 2005

We have calculated the cross section for excitation of the first vibrational level in the collision of two hydrogen molecules in the ground state. A partial wave analysis is used, and the radical equation is solved for many values of angular momentum using the high speed computer Univac. We find that the major contribution to the total cross section comes from large values of the angular momentum, of the order of 10 to 20, and that values of the angular momentum up to about 80 must be considered. In the energy range of interest, 0.5 to 2 ev, the total cross section is obtained, and the vibrational relaxation time is also computed. The value of the cross section is found by calculation to be very sensitive to the precise values of the intermolecular potential used.
Electron Spin Resonance in Transition Metal Chelates. II. Copper(II) Bis-Salicylaldehyde-Imine
Authors: Maki A. H. , McGarvey B. R.
Published: January 2005

The electron spin resonance at 3.2 cm has been observed for single crystals of copper(II) bis-salicylaldehyde-imine diluted to ½ mole percent with the corresponding nickel chelate. Analysis of the spectrum by methods given in the preceding article indicate that the sigma bonding and in-plane II-bonding are appreciably covalent, whereas the out-of-plane π bonding is ionic. Hyperfine interactions in addition to that resulting from the copper nucleus were observed and shown to be attributable to interactions with the nitrogen nuclei adjacent to the copper ion and with the two protons bonded to the carbon atoms directly adjacent to the nitrogen atoms. The two protons bonded directly to the nitrogen atoms do not contribute to the hyperfine interactions. Bonding information obtained from the magnitude of the hyperfine interaction due to the nitrogen nucleus agrees with that obtained from the g tensor and hyperfine interaction of the copper nucleus.

In addition structural information about nickel(II) bis-salicylaldehyde-imine is obtained. The Ni-O distance is 1.92±0.07 A while the Ni-N distance is 1.94±0.05 A. The angle between these bonds is found to be 93±3°.
Free-Radical Stabilization in Condensed Phases
Authors: Golden Sidney
Published: January 2005

The formation of stabilized free-radical mixtures by the low-temperature condensation of gases containing such species is considered. A primary concern is the amount of free radicals resulting from such a process.

The over-all process of formation of condensed phase stabilized free-radical mixtures involves the original means of their production as gases, the recombination of free radicals as the gaseous mixtures are transported to the seat of condensation, and the recombination which occurs in the immediate vicinity of and within the condensed phase which is formed. For the present purpose only the latter aspect is considered in any detail, the effects of production and prior recombination being summarized in a stated composition for the condensing gas. For simplicity, only mixtures consisting of a single species of atomic free radicals, diatomic molecules which may be formed from their recombination, and inert atomic species are treated.

The basis for stabilization is taken to be isolation. Thus, those condensed phase mixtures are regarded as stable which do not permit free radicals to come in contact with one another. It is assumed, therefore, that condensation occurs at a temperature sufficiently low to render the effect of diffusion negligible. Such recombination which does occur is presumed to do so as a result of the juxtaposition of the atomic free radicals.

Several models of the stabilization process are considered from a statistical viewpoint. In each instance no explicit reference is made to the kinetics of the recombination process. The effects of coordination number, surface condensation versus bulk condensation, condensation coefficient and clustering are treated. In each of the models the dependence of the condensed phase composition upon the gas phase composition and the statistical properties of the constituents is determined.
Sputtering of Silver by Neutral Beams of Hydrogen and Helium
Authors: Weiss Alarich , Heldt Lloyd , Moore Walter J.
Published: January 2005

When the unanalyzed beam from a radiofrequency ion source strikes a silver target, sputtering is caused by both the ions and the neutral particles in the beam. The sputtering due to neutrals alone has been measured by removing the ions from the beam magnetically. For a beam of 40 μA at normal incidence and 10 kv energy, in the case of hydrogen over 90%, and in the case of helium about 50% of the sputtering is due to neutrals.
Hindered Rotation in Adsorbed Hydrogen. Adiabatic Cooling by Adsorbed Parahydrogen
Authors: Sandler Y. L.
Published: January 2005

Hindrance to rotation of hydrogen molecules in the adsorbed state is discussed. The possibility is pointed out that in some cases the lowest para-level may lie close to the lowest ortho-level. It is proposed that a simple adiabatic cooling method be obtained by allowing adsorbed parahydrogen to convert to equilibrium hydrogen at low temperatures under adiabatic conditions. It is shown that very low temperatures might be obtained under favorable conditions by relatively simple means.
Quantum Statistical Theory of Plasmas and Liquid Metals
Authors: Cowan Robert D. , Kirkwood John G.
Published: January 2005

A Debye-Hückel-type theory is described for an assembly of completely ionized atoms, the nuclei being treated classically and the electrons by the Thomas-Fermi method. The thermodynamic functions are derived by considering the Debye charging process, and the virial theorem is shown to hold. Numerical results are given for hydrogen and iron near normal solid densities, and are probably accurate only at high temperatures (kT>5 ev for hydrogen and kT>100 ev for iron). At these temperatures, the results do not differ greatly from those of the ordinary Thomas-Fermi theory of the atom except for the additional contributions of the nuclei.
Radial Distribution Functions in Binary Gas Mixtures
Authors: Rubin Ephraim L. , Sundheim Benson R.
Published: January 2005

The equations of Born and Green are generalized to the two component case. An approximate solution is formally obtained by a linearization procedure and is found to contain a singularity which is tentatively identified with the gas-liquid branch point of the radial distribution function. Temperature-density relations are found in the critical region by roughly locating this singular point. The results lend weight to the hypothesis that the singularity corresponds to the branch point.
Evaluation of Two-Center Exchange Integrals
Authors: Tauber G. E.
Published: January 2005

The evaluation of two-center exchange integrals for any homonuclear molecules using Slater-type wave functions is reduced to the solution of Poisson's equation. An expression is obtained for the exchange integrals in terms of integrals which can be evaluated analytically. In particular, all cases which arise from 2s and 2p wave functions are discussed in detail and the auxiliary integrals evaluated. The pertinent results are collected in tables, and the final result for a particular exchange integral is given explicitly.
Theory of Dilute Polymer Solution. II. Osmotic Pressure and Frictional Properties
Authors: Kurata Michio , Yamakawa Hiromi
Published: January 2005

The osmotic second virial coefficient of flexible polymer solutions is calculated on the basis of the pearl-necklace model with continuous medium approximation. Proper account is taken not only of the intermolecular interaction but also of the intramolecular interaction of segments or the so-called ``excluded volume effect.'' Evaluation is carried out to the triple contact approximation. The results show that the intramolecular interaction has a marked influence on the molecular weight dependence of the coefficient.

Then, theories of the intrinsic viscosity and frictional coefficient are developed on the same model as above, following the Kirkwood and Riseman scheme. The results show that, if α is the linear expansion factor of the polymer coil, the intrinsic viscosity is asymptotically proportional to α2 for the free-draining case and α2.43 for the impermeable case. This implies that even in the limit for impermeable molecule, the hydrodynamic radius of the polymer coil is not proportional to its statistical radius.

Finally a thorough comparison of the present theories with experimental data is made, taking solutions of polystyrene in cyclohexane as an example. The results prove that the theories are very fitted for structural interpretation of experimental data.
Electric Field Gradients in Ionic Crystals. I. Nuclear Quadrupole Coupling Constants
Authors: Bersohn Richard
Published: January 2005

In ionic crystals and metals the coupling constant of a quadrupolar nucleus can often be written in the simplified form eQ(Δε)(1—γ∞). The polarization factors 1—γ∞ were calculated in previous work by T. P. Das, E. G. Wikner, and R. Bersohn. In the present work the factors Δε are calculated in the form of lattice sums. Under favorable circumstances a good estimate of the nuclear quadrupole moment Q can be made. When Q is known by other means, information about the distribution of charges in crystals may be obtained. It is shown, for example, that Al2O3 is essentially ionic. The agreement between experimental and observed coupling constants proves that the field gradients in ionic crystals and metals is of long-range origin in contrast to molecular crystals.
Determination of the Binding Energy of He2+ from Ion Scattering Data
Authors: Mason Edward A. , Vanderslice Joseph T.
Published: January 2005

Data on the elastic and the charge exchange scattering of beams of He+ ions in He gas between 4 and 400 ev are analyzed to determine precisely the interaction energies for the lowest 2Σu and 2Σg states of He2+. A Morse function is used to represent the energy for the attractive 2Σu state and an exponential is chosen for the repulsive 2Σg state. An attempt is made to determine the three disposable parameters strictly from the scattering data, but does not lead to a unique result. However, use of the spectroscopic value of the equilibrium distance for the 2Σu state permits a unique determination, leading to interaction energies valid from about 0.9 A to 3.8 A. The energies are in good agreement with available quantum-mechanical calculations and give a dissociation energy of 2.16 ev for the 2Σu state. The cross-section calculations are given in reduced units in a form readily applicable to the calculation of binding energies for similar systems as data may become available.
Infrared Absorption of Cyanogen in the Cesium Iodide Region and CN Bond Moment
Authors: Miyazawa Tatsuo
Published: January 2005

A spectrometer with cesium iodide optics has been built, and used to measure the ν5 bands of the normal and C13-enriched cyanogen. By the use of molecular data, the thermodynamic functions of cyanogen were calculated. The bending frequencies and normal modes were calculated by a normal coordinate treatment. The absolute intensity of the ν5 band was measured and the derivative of dipole moment with respect to the symmetry coordinate was determined. On the assumption of independent rigid bond model the effective CN bond moment was calculated to be 1.2D.
Vibrational Spectrum and Structure of Metal-Cyanide Complexes in the Solid State. IV. K3Cu(CN)4
Authors: Jones Llewellyn H.
Published: January 2005

The polarized infrared spectrum of single crystals of K3Cu(CN)4 has been observed. The fundamental frequencies of Cu(CN)4—3 under point group Td have been assigned as 2094, 288, 324, 63, 2079, 364, 306, 74, and 250 cm—1. From these frequencies, valence force symmetry force constants were calculated. Both the CN and CuC stretching force constants were found to be quite low (16.2 and 1.3 md/A, respectively). The CuC force constant, along with Badger's rule, gives a CuC distance of 2.05 A, somewhat shorter than the single bond distance of 2.12 A, predicted from the tetrahedral radii.
Volumes of Activation for Diffusion in Solids
Authors: Keyes Robert W.
Published: January 2005

Activation volumes for the following simple models of lattice defects are calculated: (a) simple vacancy in a monatomic lattice, (b) simple vacancy with elastic theory of relaxation, (c) Schottky defect in an ionic crystal with dielectric theory of relaxation, (d) surface tension model of a vacancy in a metal, (e) elastic sphere model of an interstitial atom, and (f) strain energy theory of defect motion. The calculations are compared with experimental measurements. The comparison is satisfactory in many cases. In particular, it is observed that most of the data can be represented by the equation ΔV=4βΔH (β=compressibility, ΔH=activation energy), and that an equation of this type can be derived from several of the models. This equation can be used with a result of Lawson's to derive Zener's expression for the activation entropy of diffusion.
Improved Simple Analytical Wave Functions for Atoms
Authors: Saturno Antony F. , Parr Robert G.
Published: January 2005

Approximate wave functions for the ground states of He, Be, Ne, and Na+ are constructed which are antisymmetrized products of single Slater orbitals of nonintegral principal quantum numbers, ns,ns′,np, and variable orbital exponents, ζs,ζs′,ζp. Best values for the several parameters n and ζ are determined by the variational method, and the corresponding energies are computed. Significant improvements over the usual integral-n approximations are found; for Na+ there is obtained an energy — 161.44 a.u., compared with the integral-n result — 160.94 a.u. and the Hartree-Fock value — 161.88 a.u. The ground states of the two-electron ions H— through NaX are similarly treated, and the diamagnetic susceptibilities of He, Be, Ne, and Na+ are computed theoretically and compared with observed and other theoretical values.
Theory of Diffusion near Walls
Authors: Fixman Marshall
Published: January 2005

A model previously proposed for momentum transport in fluids, in which momentum and energy are carried by dipole density waves centered on the molecule of interest, is here applied to a calculation of the hindering effect of a wall on diffusion. Consideration is given to both specular and diffuse reflection of the density waves by the wall. The ratio γ of the diffusion constant at a distance l from the wall to the bulk fluid diffusion constant is calculated for diffusion parallel to the wall (γx), and perpendicular to the wall (γz). For the diffuse reflection case γx=(1+l02/8l2)/N,γz=1/N,N=1+(l02/4l2)+(3l04/288l4) and l0 is estimated as 9η(m0/kT)12/2ν where η is the shear viscosity, m0 the molecular mass, and ν the mass density of solvent; l0 may be as large as several hundred angstroms for simple liquids at room temperature.
Additivity Rules for the Estimation of Molecular Properties. Thermodynamic Properties
Authors: Benson Sidney W. , Buss Jerry H.
Published: January 2005

A general limiting law is proposed which can be used to systematize the various laws of additivity of molecular properties. This can be stated as follows: ``If φ is a molecular property, then for the disproportionation reaction: RNR+SNS⇄2RNS, Δφ→0 as the separation between R and S becomes large compared to their dimensions.

It is shown that the zero-order approximation is equivalent to the law of additivity of atomic properties, the first-order approximation to the law of additivity of bond properties, the second-order approximation to the law of additivity of group properties, and so forth. It is shown that for Cp and S° (ideal gases), the additivity of atomic properties works to about ±2 cal/mole-°K, while the additivity of bond properties is usually good to about ±1 cal/mole-°K. The latter also estimates ΔHf° to about ±3 kcal/mole. The group additivity relation is generally obeyed to within ±0.5 cal/mole-°K for Cp and S° and about ±0.6 kcal/mole for ΔHf°. Tables are presented for each of the partial properties at 25°C.

The agreements found for the various additivity rules is examined from a molecular point of view and certain extensions and limitations indicated. The application and utility of the rules in estimation of thermodynamic properties is discussed.

The estimation of bond dissociation energies is possible with the additivity rules as are the thermodynamic properties of free radicals. An application of the rules to species NR2 and NS2 show that R and S may be ordered according to their general bond-weakening or bond-strengthening properties. For systems where N is C2H4 it is shown that the first and second bond dissociation energies for RC2H4R is very likely a constant = 59.5 kcal, the excitation energy of C2H4.
Microwave Studies of the Structure of Cyclopropyl Derivatives
Authors: Friend James P. , Dailey B. P.
Published: January 2005

The microwave spectra of cyclopropyl chloride and cyclopropyl cyanide have been studied and rotational constants for the Cl35 and Cl37 molecules of the chloride and for the normal molecule and two deuterated species of the cyanide have been determined. The two deuterated species are the cis and trans forms of C lim |H2–CHD–C lim |¯H–CN.

For C3H5Cl35, A = 16 625±145 Mc, B = 3905.4±0.3 Mc, and C = 3622.5±0.3 Mc. For C3H5Cl37, A = 16085±415, B = 3810.4±0.5 Mc, and C = 3540.8±0.5 Mc. The following structure fits the rotational constants within the experimental errors: dC–C = 1.5131 A, dC–Cl = 1.7780 A, dC–H = 1.105 A, ≰HCH = 114°36′, ≰HCCl = 120°52.9′.

For C3H5CN, A = 15 917 Mc, B = 3465.06 Mc, and C = 3286.22 Mc. For cis C3H4DCN, A = 14 543 Mc, B = 3419.34 Mc, and C = 3229.15 Mc. For trans C3H4DCN, A = 15 367 Mc, B = 3358.79 Mc, and C = 3161.26 Mc.

The following structure fits the rotational constants B and C to an average of 1.5 Mc: dC–C(ring) = 1.5131 A, dC–C(CN) = 1.4679 A, dC–H = 1.112 A, dC≡N = 1.1574 A, ≰H–C–H = 115°35′, and ≰C(CN)−C−−H=119∘35′.

Analysis of the quadrupole structure in C3H5Cl shows that eqQ along the C–Cl bond axis is —71.7 Mc for Cl35, indicating 23% ionic character. The asymmetry η = 0.156 for Cl35 indicates a double bond character of 4%.
Overhauser Effect in Manganese Solutions in Low Magnetic Fields
Authors: Codrington R. S. , Bloembergen N.
Published: January 2005

The sign of the Overhauser effect for protons in Mn++ aqueous solutions in external fields between 5 and 20 gauss is such, that the dominant relaxation mechanism is scalar coupling between the protons and electron spins.

The electronic ΔF = 0, ΔmF = ±1 transitions in the hyperfine multiplet were saturated and the enhancement of the proton resonance signal with increasing electronic saturation was observed up to a factor of about 300 times. The dependence of the proton and electron relaxation times on external field agree well with a theory which takes due account of the hyperfine multiplet in the Mn++ ion.
Screened Interactions of Neighbor Ions and Symmetry Properties of Titration Curves in Polyelectrolytes
Authors: Warga J. , Lifson Shneior
Published: January 2005

A model of neighbor ions interactions in polyelectrolytes is treated, in which it is assumed that a fixed ion inserted between two other fixed ions acts as a screen, so that two fixed ions may interact only if there are no other fixed ions inserted between them. It is shown that the effect of screening is to increase the buffering capacity at higher degrees of ionization. The results of the present model are compared with those of other models of neighbor interactions.
Polymeric Gaseous Molecules in the Vaporization of Alkali Halides
Authors: Berkowitz Joseph , Chupka William A.
Published: January 2005

The molecular species of alkali halide vapors in equilibrium with their respective condensed phases have been deduced by a mass spectrometric analysis of the ions produced by electron impact. Dimers, trimers, and in some instances tetramers MnXn were observed, with the lithium halides exhibiting more dimeric than monomeric species. The results are in substantial agreement with earlier molecular beam velocity selector experiments, and discordant with some recent infrared spectral studies. Some oddities in the ionization efficiency curves are also discussed.
Free-Convectional Heat Transfer from a Single Horizontal Wire
Authors: Arajs Sigurds , Legvold Sam
Published: January 2005

Free-convectional heat transfer from single, horizontal, heated, 2-, and 3-mil platinum wires was measured in gaseous A, N2, O2, CO2 and in liquid (CH3)2CO, CH3OH, C6H5CH3. The measurements, extending approximately from GrPr=1 to GrPr=10—5, satisfied the Senftleben correlation.
Effect of Pressure on Viscosity of Higher Hydrocarbons and Their Mixtures
Authors: Griest Edward M. , Webb Wayne , Schiessler Robert W.
Published: January 2005

Using the rolling-ball method the viscosity of seven pure hydrocarbons, having 25 or 26 carbon atoms, and three binary mixtures of them has been measured to 3450 bars at 37.8°, 60.0°, 98.8°, and 135°C. The compounds included isoparaffinic, cycloparaffinic, and aromatic types. The increase in viscosity with pressure was found to be strongly dependent on molecular structure. The viscosity-temperature coefficient 1/η(∂η/∂T)p increased with increased pressure while the viscosity-pressure coefficient 1/η(∂η/∂P)T decreased with increased temperature. The behavior of the binary mixtures corresponded within 5% over a range of 50–100 fold change in viscosity to that of the pure compounds equivalent to them in molecular weight and average molecular structure. This remarkable agreement is interpreted to mean that the viscosity of these compounds is some additive function of their constituent groups whether these groups are combined in the same or different molecules as long as the basic molecular symmetry is unchanged. The values of the Eyring theory ΔF±, ΔH±i, ΔS±, and ΔV± for these data are discussed. For the saturated compounds at constant temperature, an approximately linear relation was found between log η and [(v/v0)4—(v/v0)2] where v is the specific volume and η the absolute viscosity.
Delayed Fluorescence in Naphthalene Crystals at 4°K
Authors: Sponer H. , Kanda Y. , Blackwell L. A.
Published: January 2005

The fluorescence of naphthalene crystals has been observed through a phosphoroscope indicating that a part of this emission has a lifetime greater than 10—3 sec at 4.2°K. It is suggested that this phenomenon is connected with the photoconductivity observed in crystals of aromatic compounds and has its origin in the storage of energy by an electron trapping mechanism.
Fluorescence Spectrum of PrCl3 and the Levels of the Pr+++ Ion
Authors: Dieke G. H. , Sarup R.
Published: January 2005

PrCl3 shows strong fluorescence from the 3P0, 3P1, and 1D levels to all low-lying levels of the Pr+++ ion (3H, 3F, 1G). This makes it possible to obtain all multiplet components of 3H and 3F. Previously unreported lines in the absorption spectrum are interpreted as transitions to the hitherto unknown 1I6. Zeeman effect data corroborate this. All levels to be expected from a 4f2 configuration are now known for PrCl3 except 1S0 which should give a line in a different part of the spectrum.
Thermodynamics for Nonisothermal Systems. The Classical Formulation
Authors: Li James C. M.
Published: January 2005

The classical theory of Thomson, Eastman, and Wagner of the thermodynamics of nonisothermal systems is studied in the light of the Gibbs formulation of heterogeneous equilibrium. It is found that an extension of Gibbs' derivation will include the classical theory of nonisothermal equilibrium as a special case. The Onsager reciprocal relations can be obtained from macroscopic considerations which also give a relation between the second-order phenomenological coefficients. The concept of second-order independence is introduced, which provides a way of finding the actual processes.
Diffusion of Hydrogen in Palladium
Authors: Silberg P. A. , Bachman C. H.
Published: January 2005

The rate of flow of hydrogen through palladium has been measured in a range of temperatures 200°C to 600°C over the pressure range 10 to 70 cm Hg. The flow rate is found insensitive to palladium wall thickness. The data do not seem to be explainable in terms of existing theory.
Shock-Tube Study of Luminosity in Xenon
Authors: Roth Walter , Gloersen Per
Published: January 2005

Shock waves in xenon producing temperatures in the range 6000–11 000° K have been found to result in emission of a visible continuum after an induction period. An activation energy for continuum emission has been found to correspond to the energy of the metastable state of the xenon atom. This energy can only be associated with visible continuum emission if ground state and metastable state atoms interact to form stable diatomic molecules in an excited state which subsequently make dissociative transitions to a repulsive ground state.
Energies Involved in Reorienting Hydration Shells of Ions
Authors: Reynolds Warren L.
Published: January 2005

Free energies for reorientation of solvent molecules about ions have been calculated using Marcus' equation for the electrostatic potential and compared with values derived from charge transfer spectra. The low values obtained suggest that electron tunneling between fully hydrated ions is a feasible mechanism contrary to the conclusions of Platzman and Franck.
Determination of Molecular Structures from Ground State Rotational Constants
Authors: Costain C. C.
Published: January 2005

Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero-point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.

In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure only from the rs coordinates and make no attempt to reproduce the I0 values, the structure is virtually independent of the isotopic species used in the determination. The variation in the structures obtained from different sets of isotopic species appears to depend only on the uncertainties in the rotational constants. In addition, the accuracy is independent of the mass of the substituted atom, and therefore H atoms are located just as accurately as the heavier atoms.

The rs structures of HCN, N2O, OCS, CH3CCH, CH3CN, CH3NC, and the methyl halides have been determined by the isotopic substitution method. For the first three molecules comparisons can be made with equilibrium data, and it is found that the rs bond lengths are no more than 0.002 A greater than the re. The primary interest in the other molecules studied is in the structure of the methyl group. The anomalous separation of the H and D coordinates previously found is readily explained and does not appear in the rs structures. The consistency of the results is such that comparisons between molecules can be made with confidence.
Ground-State Inversion Spectrum of N14D3
Authors: Herrmann Gabriel
Published: January 2005

The inversion spectrum of N14D3 has been investigated between 1500 and 1620 mc/sec. A revised formula for the rotational fine structure was obtained to fit 17 observed lines. Splitting of K = 3 lines into two components was found in good agreement with predicted values. Nitrogen satellites were observed and the values (eQq)N = 4080–3 kc/sec and α = 2±2 kc/sec were assigned to the nitrogen quadrupole and magnetic coupling constants, respectively. Hyperfine structure due to removal of the K degeneracy was observed in K = 1 lines. Applying the theory of Hadley, calculated and observed line contours were brought into agreement. Assuming cylindrical symmetry about bonds, the value (eQq)D = 200±20 kc/sec was obtained for the deuteron quadrupole coupling constant. A value ε = 1.9±0.5 kc/sec was obtained for the magnetic coupling constant between deuteron spins and molecular rotation.
Photolysis of Nitromethane and of Methyl Nitrite in an Argon Matrix; Infrared Detection of Nitroxyl, HNO
Authors: Brown Harmon W. , Pimentel George C.
Published: January 2005

The photolysis of nitromethane in solid argon at 20°K gives methyl nitrite. All other products can be explained in terms of the secondary photolysis of methyl nitrite. This work provides a definitive basis for segregating the vibrational frequencies of the cis- and trans-isomers of methyl nitrite. The primary products of photolysis of methyl nitrite under these conditions are formaldehyde and nitroxyl, HNO. The identification of HNO, detected by its infrared spectrum for the first time, is confirmed by the band shifts occurring upon deuteration. The vibrational frequencies of HNO (1570 and 1110 cm-1) and DNO (1560 and 822 cm-1) correspond to a bent molecule with a double bond between the nitrogen and oxygen atoms, thus supporting the structure HNO over the possible arrangement HON. The bending force constant, 0.67·10-11 dyne-cm, suggests that the HNO angle is near 110°, larger than the earlier estimate of 102° based on electronic spectra.
Comparison of Theoretical and Experimental Electron Collision Cross Sections for Three Excitations in Helium
Authors: Silverman S. M. , Lassettre E. N.
Published: January 2005

A comparison of theoretical and experimental electron collision cross sections is made for transitions from the ground state of the helium atom to the 21S, 21P, and 31P excited states.
High-Speed Computations in the Kinetics of Free-Radical Degradation. I. Random Initiation
Authors: Simha R. , Wall L. A. , Bram J.
Published: January 2005

The theory of free-radical degradation leads to large sets of difference-differential equations for the reacting species, which can be solved analytically for practical purposes only in the extremes of preponderant chain depropagation and random or terminal scission, respectively. Moreover, the equations are linearized by neglecting the variation of the steady-state radical concentration with degree of volatilization. Numerical solutions of the linearized set were obtained on the SEAC and the resulting zeroth and first moments of the distribution tabulated for the case of random initiation. Thus the rate of volatilization and the number-average degree of polymerization can be computed as functions of conversion. Initially monodisperse systems and a maximum chain length of 400 C atoms, which determines the size of the set, were assumed. In addition to the latter there are three parameters, viz., the average ``zip'' length, (1/ε—1), a transfer constant, σ, and the maximum size of vaporizing chain fragments. All of these were varied over a wide range so as to reproduce the wide spectrum of behavior found experimentally. Where applicable, earlier analytical results were confirmed. The errors inherent in the linear approximation can be estimated and are found not to affect the results significantly over a useful extent of reaction. For a certain range of parameters, ``corresponding states'' rules can be established and the results applied regardless of the absolute magnitude of the initial chain length. Depending on the parameter values, and hence on the molecular structure, the initial rates also exhibit wide variations in absolute magnitude and sensitivity to initial molecular weight. The kinetics in polystyrene and particularly poly-α-methyl styrene are discussed in the light of the theory. For the latter polymer, both the decrease in molecular weight, and the dependence of initial rates on the initial chain length lead to a consistent picture of a long average zip length, approximately 1.3×103 monomer units, combined with a random initiation. The upper limit for the initiation constant is 3.42×10—6 sec—1 at 272°C.
Thermal Diffusion of Vacancies in Zinc
Authors: Shewmon Paul
Published: January 2005

Thermal diffusion, or the Ludwig-Soret effect, can be described by adding, to the isothermal flux equation, a second term proportional to the product of the temperature gradient and Q*, the heat of transport. The magnitude of Q* for vacancies in zinc, was determined by placing markers in a piece of pure zinc, which was then held in a temperature gradient near its melting point. No marker movement was observed in twenty days. Thus the net flux of vacancies was effectively zero so that the effect of the strong concentration gradient was canceled by the thermal-diffusion force. This result is rationalized in a discussion of Q*. A brief analysis of Q* for solutes, other than vacancies, shows that in general Qi* will be approximated by the partial molar heat of solution of the solute, H̄i, where the pure solute is taken as the standard state. A survey of the available data for Q* shows that one obtains the experimentally observed sign for Q* in each case if one takes simply Qi*=—H̄i.
Vibrational Intensities. X. Integration Theorems
Authors: Crawford Bryce
Published: January 2005

The advantages of integrating absorption intensities against the logarithm of the frequency, rather than against the frequency itself, are presented.
Concerning Reconstructive Transformation and Formation of Glass
Authors: Turnbull David , Cohen Morrel H.
Published: January 2005

An explanation based on kinetic considerations is developed for the failure of some pure liquids to crystallize. The important parameters are (1) α, the ratio of the molar liquid-solid surface tension to the heat of fusion ΔHf, (2) β, the ratio of the entropy of fusion to R, (3) ΔG′, the kinetic barrier to nucleation, and (4) ΔG″, the kinetic barrier to the growth of the finite crystal. In the absence of foreign nucleating agents sensible crystallization will not occur if αβ⅓≲0.9 and ΔG′≤0, or if ΔG′ or ΔG″≤30(ΔHf/β) = 30 RTm.

In nonreconstructive crystallization the molecules incorporated into the crystal are the same as those existing in the liquid. In this case ΔG′ and ΔG″ are likely to be the same and of the order of magnitude of the free energy of activation for fluid flow, ΔGf. Usually, αβ13∼12 and ΔGf≪30 RTm, in nonreconstructive crystallization and the nucleation of crystals in clean liquids, is sensible at some undercooling. There are some organic liquids in which crystallization is nonreconstructive and that do not crystallize when clean. We have found that the ratio Tb/Tm of the normal boiling point to the melting point is abnormally large in these cases and near two or more for those compounds that clearly form glasses. Since β and ΔG′/RTm are both likely to increase with Tb/Tm, the difficulty of crystallization would increase with this ratio. It is probable that this correlation also holds for inorganic molecular liquids.

In reconstructive crystallization the molecular entities in the crystal differ from those which predominate in the liquid and bonds between atoms must be broken in order for nucleation to occur. Thus ΔG′ can be of the order of the bond energy, which often exceeds 30 RTm, and, excepting in network liquids, much greater than ΔGf.

Bonds between atoms also must be broken for the reconstructive growth of finite crystals. However, this process can be promoted by impurities and molecular fragments in ways not possible in homogeneous nucleation so that ΔG″ as well as ΔGf can be much less than ΔG′. The reconstructive growth of finite crystals at the expense of a different crystal phase can be enhanced similarly so that ΔG″ may be much less than ΔG′ in this case also.
Use of 4p Orbitals in Metal-Aromatic Complexes
Authors: Brown David A.
Published: January 2005

The use of 4p orbitals of the central metal atom in metal-aromatic complexes is discussed. It is shown that, within the usual assumptions of the semiempirical molecular-orbital method, it is necessary to use Slater orbitals of a nonintegral power and with an exponent close to that calculated by the Slater rules. The electroneutrality principle of Pauling is also discussed and a large charge transfer within these complexes is found to contradict the original assumptions of the molecular-orbital theory.
Small-Angle X-Ray Scattering from Solutions of Aerosol OT in Nonaqueous Media
Authors: Siegel L. A.
Published: January 2005

The small-angle scattering of solutions of di(2-ethylhexyl) sodium sulfosuccinate in n-dodecane has been investigated for the concentration range 6%—75%. The results agree with earlier work of Mattoon and Mathews and of Philippoff, in that a gradual decrease of scattered intensity with angle is found for the low concentrations, while a pronounced intensity maximum at a nonzero angle is found at the higher concentrations. The data further show that there is a gradual transition of the shape of the scattering curve between extremes as the concentration is varied.

It is proposed that the observed changes in shape of the experimental curves represent the transition from gas-type to liquid-type scattering. The x-ray data are consistent with the existence of only one type of micelle over the entire concentration range. It is not necessary to postulate any special intermicellar arrangement to explain the high-concentration scattering maximum.

While no detailed statement as to individual micellar structure can be made with the present data, they are consistent with an inverted structure in which the polar, more heavily scattering ends, are in the interior of the micelle.

It is suggested that the exponential scattering observed in the low-concentration limit may have been overlooked in some earlier investigations of colloidal systems; conclusions drawn in these cases as to inability of the systems to form micelles because of molecular shape may be incorrect.
N14 Quadrupole Interaction with an Asymmetric Field Gradient
Authors: Casabella P. A. , Bray P. J.
Published: January 2005

N14 pure quadrupole resonances have been found in three compounds having a nonzero asymmetry parameter for the electric field gradient at the resonating nuclei. The shapes of these resonances demonstrate a decrease in the effectiveness of Zeeman modulation as the asymmetry increases, in agreement with theory.
Molecular Diffusion Studies in Gases at High Temperature. I. The ``Point Source'' Technique
Authors: Walker R. E. , Westenberg A. A.
Published: January 2005

Experimental apparatus and technique for a new method of measuring the diffusion coefficients of gases are described and critically discussed. The method makes use of the steady injection of a trace gas from a fine, hypodermic tube (essentially a ``point source'') into a slow, uniform, laminar stream of a second (carrier) gas. Measurements of the trace gas concentration downstream of the source by means of precise gas sampling permit the binary diffusion coefficient to be determined. By heating the carrier gas the measurements may be extended to fairly high temperatures. Another advantage offered by the method is that the trace gas concentrations involved are essentially zero, so that uncertainties regarding the concentration dependence of the diffusion coefficient are avoided. Results of about ±1% precision over the temperature range 300–1150°K are presented for the systems He–N2 and CO2–N2.
Evaluation of Force Constants of Plane XY3 Molecules from Vibrational Data
Authors: Pistorius C. W. F. T.
Published: January 2005

All five force constants of the most general harmonic potential field are evaluated for 4 molecules and 4 ions of the plane XY3 type (symmetry group D3h) by means of Wilson's F—G matrix method. In the cases where no isotopic data are available, this is made possible by the introduction of an approximation from Heath and Linnett's OVFF treatment. Semiquantitative corrections are made for anharmonicity and for the product rule wherever possible. In the case of BF3, the results are compared with those of a previous worker.
Mobile Bond Orders in the Resonance and Molecular Orbital Theories
Authors: Ham Norman S.
Published: January 2005

The bond orders of the resonance theory are shown to be identical with certain molecular orbital quantities which are similar to the usual MO bond orders. This equivalence, related to similar results of Dewar and Longuet-Higgins, suggests that the two theories, also in their simplified forms, are not so widely different as it is sometimes supposed.
Theorem on the Mobile Bond Orders of Alternant Conjugated Systems
Authors: Ruedenberg Klaus
Published: January 2005

A generalization of Hall's theorem for Coulson bond orders in alternant molecules is derived. The new relation expresses general bond order-like quantities in terms of the topological molecular matrix. Specialization to the Mulliken bond orders furnishes an exact relation between the Coulson and the Mulliken bond order matrices in the ground state of alternants.
Interpretation of Chain-Ring Equilibria in the Polymerization of Substituted ε-Caprolactam
Authors: Yumoto Hirosuke
Published: January 2005

If one of the hydrogens in ε-caprolactam is substituted by a methyl or an ethyl group, the quantity of the lactam monomer remaining in its polymerization reaction is greater than that for the unsubstituted one. When the alkyl groups higher than ethyl are introduced, the lactam ring can hardly be polymerized. These shifts in chain-ring equilibria are explained by the change in the thermodynamical properties caused by the existence of rotational isomers. The heat of reaction and the quantity of the remaining lactam ring at the equilibrium for α−,β−,γ−,δ−, and ε-monomethyl and γ-ethyl derivatives were estimated from this point of view. The calculated and the observed values are in good agreement.
Thermal Conductivity of Multicomponent Gas Mixtures
Authors: Muckenfuss Charles , Curtiss C. F.
Published: January 2005

An equation is derived for the complete second approximation to the thermal conductivity of multicomponent gas mixtures. The result is found to be identical with an ``approximate'' formula for the thermal conductivity derived on the assumption that the thermal diffusion coefficients are negligibly small.