bluuebunny/crossref_metadata_2025 huggingface dataset:
Quadrupole Coupling of the Deuteron in DCCCl and DCN
Authors: White Robert L.
Published: April 2005

The quadrupole coupling of the deuteron (eqQ) D was measured in DCCCl where it was found to be +175±20 kc/sec. A less accurate determination of the absolute value (eqQ) D in DCN yielded approximately 290 kc/sec. The field gradient, q, at the deuterium nucleus in DCCCl is +8.85±10 percent×1014 esu. A calculation of q based on a Hund-Mulliken molecular model yields a q of the same sign as that observed but approximately twice as large, indicating the insufficiency of the model for such detailed calculations.
Absorption of Bicycloheptane and Bicycloheptene in the Vacuum Ultraviolet
Authors: Stokes Suzanne , Pickett Lucy W.
Published: April 2005

The vacuum ultraviolet absorption spectra of bicycloheptane and bicycloheptene have been investigated in the region from 45 000 to 65 000 cm—1. Two distinct band systems with maxima at 51 125 and 59 715 cm—1 were noted in the case of bicycloheptene, each with an oscillator strength of 0.15. The first observed absorption of bicycloheptane was near 55 000 cm—1 while that of the unsaturated hydrocarbon was displaced more than 8000 cm—1 toward lower frequencies. In both compounds, sharp narrow bands were superimposed on the continuous absorption. In a study of the photodecomposition, it was shown that cyclopentadiene and ethylene were formed as photodecomposition products of bicycloheptane and also of bicycloheptene.
Capacitance and Conductance Effects in Photoconducting Alkali Halide Crystals
Authors: Macdonald James Ross
Published: April 2005

Measurements of the ac and dc response of illuminated F-centered potassium bromide single crystals have been carried out. The dependence of crystal capacitance and conductance on frequency, light intensity, electrode character and separation, F-center concentration, applied voltage, temperature, and optical bleaching time have been investigated. Most of the measurements were made on crystals containing both U and F centers, but a few were also made on additively colored and plain untreated crystals for comparison.

It was found that F centers in U-centered crystals bleached much slower under strong illumination than did those in additively F-centered crystals. The frequency response of the crystals depended significantly upon whether the electrodes were blocking or rectifying, but in both cases it was characterized by a single relaxation time given by the quotient of a series capacitance C0 and G∞, the normal conductance of the crystal. C0 was found to be independent of all variable parameters except dark storage and bleaching time and is thought to arise from a charge-free layer located at one or both electrodes. Space-charge capacitance effects were apparently largely hidden by C0 but did probably produce a small voltage-dependent non-linearity observed at low frequencies with high applied voltages. G∞, and thus the conduction-band electron concentration, depended linearly on light intensity over a wide range but underwent a transition from linear dependence on F-center concentration to independence thereof at high concentrations. Partly bleached crystals in total darkness exhibited appreciable conductivity, probably electronic in character. Most of the results on U-centered crystals can be tentatively explained in terms of electron trapping by negative-ion vacancies, F centers, interstitial hydrogen atoms, and hydrogen atoms in negative-ion vacancies.
Vibrational Spectra of Cyclobutforene (Hexafluorocyclobutene)
Authors: Nielsen J. Rud , El-Sabban M. Z. , Alpert Morris
Published: April 2005

The infrared spectrum of gaseous cyclobutforene has been obtained in the region from 2 to 38μ with the aid of LiF, NaCl, KBr, and KRS-5 prisms. The Raman spectrum of the liquid phase has been photographed with a three-prism glass spectrograph of linear dispersion 15 A/mm at 4358 A. With some uncertainties, especially as to symmetry species, all of the twenty-four fundamental vibration frequencies have been assigned, and the spectra have been interpreted in detail.
A Mass Spectrometric Study of Gaseous Species in the Al–Al2O3 System
Authors: Porter Richard F. , Schissel Paul , Inghram Mark G.
Published: April 2005

The vaporizing species in the Al–Al2O3 system are identified mass spectrometrically. Intense ion currents of Al2O+ formed from gaseous Al2O are observed. At T = 1750°K ions formed from other gaseous oxides are at least 1000 times less intense than Al2O+. The appearance potential of Al2O+ is 7.7±0.2 ev. A thermodynamic treatment of gaseous Al2O gives for Al2O(g) = 2Al(g) + O(g), ΔH298 = 256±7 kcal.
Vibrational Intensities. V. BrCl and ICl
Authors: Brooks Wendell V. F. , Crawford Bryce
Published: April 2005

The intensity coefficients, A1, of the fundamental vibrational bands of BrCl and ICl have been measured. From these, the derivatives p′ have been calculated. An upper limit has been set for the overtone intensity coefficients, A2, and the second derivatives p″. The values are: for BrCl, A1 = 105 cm/millimole, A2<2.5 cm/millimole, p′ = ±0.78 debye angstrom—1, |p″| < 10 debye angstrom—2; for ICl, A1 = 650 cm/millimole, A2<4 cm/millimole, p′ = ±2.1 debye angstrom—1, |p″| < 14 debye angstrom—2.
Some Physical Properties of Plutonium Metal
Authors: Jette Eric R.
Published: April 2005

Data on some of the physical properties of plutonium metal are given, including allotropic modifications, crystal structures, transformation temperatures, melting point, densities, expansion coefficients, electrical resistance, and magnetic susceptibility.
Pressure Broadening of Linear Molecules. II. Theory
Authors: Smith William V. , Lackner H. A. , Volkov A. B.
Published: April 2005

The large collision diameters for the self pressure broadening of OCS and BrCN can be explained in terms of P. W. Anderson's general theory as due to the first order dipole-dipole interaction. The temperature dependence of the pressure broadening requires the introduction of other interactions. It is possible to obtain both the magnitude and temperature dependence of the pressure broadening by considering both the first order dipole-dipole and quadrupole-dipole interactions.
Scattering of High Velocity Neutral Particles. V. Neon-Neon
Authors: Amdur I. , Mason E. A.
Published: April 2005

Total collision cross sections have been measured for neon atoms with energies between 500 and 2100 ev scattered in room temperature neon. The experimental results have been treated to obtain potential energy information for the interaction of two neon atoms. The analytical relation, which may be represented by V(r)=5.00×10−10/r9.99ergfor r between 1.76 A and 2.13 A, is consistent with the potential, valid at larger separation distances, which has been derived from measurements of gaseous compressibility, viscosity, and crystal properties.
Magnetic Shielding of Nuclei in Molecules by a Variational Method
Authors: Hornig James F. , Hirschfelder Joseph O.
Published: April 2005

The accurate measurement of nuclear magnetic moments requires a calculation of the magnetic field at the nucleus arising from the orbital motions of the electrons in the external magnetic field. In this note we outline a solution of the ``magnetic shielding effect,'' using the quantum-mechanical variation principle. Since all results are in terms of ground-state wave functions, such an approach may facilitate a purely theoretical evaluation of shielding constants. As a variation function we take a function of the type suggested by Hylleraas and Hassé and applied successfully to calculation of polarizabilities. Previously, Ramsey used a second-order perturbation method to calculate the magnetic shielding. His results are difficult to apply since the wave functions of excited electronic states of molecules are seldom available.
Infrared Emission and Absorption in an Ammonia-Oxygen Diffusion Flame
Authors: Dows David A. , Whittle Eric , Pimentel George C.
Published: April 2005

An ammonia-oxygen diffusion flame has been studied spectroscopically in the infrared region using a flat diffusion flame of the kind described by Wolfhard and Parker. The emissions of OH, NH3, and H2O and the absorptions of NH3 and H2O have been studied as a function of position in the flame. Combined with the information obtained earlier by Wolfhard and Parker concerning the distributions of OH, NH, NH2, and O2, a complete description of the flame is possible. Evidence is presented that OH is in vibrational as well as rotational equilibrium in the flame.

No evidence of infrared emission by NH or NH2 could be found.
Luminescence Produced as a Result of Intense Ultrasonic Waves
Authors: Griffing Virginia , Sette Daniele
Published: April 2005

The luminescence produced by intense ultrasonic waves has been investigated in a number of water solutions and organic liquids in the frequency range 0.66—2.0 mc/sec. Together with direct visual tests, quantitative measurements have been performed for which a photometric method has been developed. The results show that luminescence, when it does occur, is always present with cavitation and starts at the same sound intensity as cavitation. A quantitative relationship is established between intensity of luminescence and chemical yield induced by ultrasonics. From this it is concluded that, at least in some of these cases, the phenomenon is chemiluminescence. None of the organic liquids tested showed any luminescence except for nitrobenzene in which the luminescence was very weak in the frequency range and under the physical conditions examined. It is not possible at present to conclude whether this weak luminescence is due to some chemical reaction occurring in it or to a different process. An apparent frequency dependence for the intensity of luminescence was observed; however, it is shown that the threshold of cavitation is the frequency-dependent phenomenon.
Compressibility of Gases. I. The Burnett Method. An Improved Method of Treatment of the Data. Extension of the Method to Gas Mixtures
Authors: Pfefferle William C. , Goff John A. , Miller John G.
Published: April 2005

The theory of the Burnett method of measuring the compressibility of gases is discussed, and an analytical method of treating the data is presented. Determinations of the compressibility factor at 30°C for helium, nitrogen, and carbon dioxide show the convenience of the analysis and the precision that may be obtained by the method. Extension of the Burnett measurement to gas mixtures is also reported for some binary combinations of the three gases.
Electron Interaction in Hydrocarbon Multiple Ions
Authors: Hush N. S. , Blackledge J.
Published: April 2005

The relative ground-state electronic energies of singly and doubly-charged negative ions of unsaturated hydrocarbons are discussed in terms of systematically-approximated self-consistent molecular orbital theory. It is concluded that in the gas phase and in solution, R— ions will be stable by several ev to disproportionation into R and R=, which accords well with the recent paramagnetic resonance measurements of Lipkin et al. Further implications relevant to the solution chemistry of these ions are briefly discussed.
Paramagnetic Species in Gamma-Irradiated Ice
Authors: Matheson Max S. , Smaller Bernard
Published: April 2005

The paramagnetic resonance spectra of H2O and D2O ice irradiated at 77°K have been examined. The absorbing species have been identified as H and OH (or D and OD), a significant result for the radiation chemistry of aqueous solutions. The yield of radical pairs/100 ev is about 0.14. The hyperfine splittings of the H doublet and D triplet are a factor of 16 less than are observed in the gas phase. This result is attributed to the effect of the solid on the electronic state of the H or D atoms. The spectra of H2O2 in H2O and D2O2 in D2O irradiated at 77°K support the identification of OH (or OD) absorption. In annealing experiments the H and OH disappear near 115°K. Results on solid ammonia and solid formic acid irradiated at 77°K are also described.
Study of Nuclear Resonance of the Supercooled Rotational Transition of 2,3-Dimethylbutane
Authors: Segall Herbert , Aston J. G.
Published: April 2005

The proton magnetic resonance lines during the transition of the supercooled variety of 2,3-dimethylbutane to the normal state have been investigated. An increase in rotational characteristics is followed by an exponential decrease in peak height of the resonance line. This is interpreted in terms of a transition around Frenkel holes. An observed asymmetry in the line shape is treated mathematically on this basis.
Influence of Electrode Material on Oxygen Overvoltage: A Theoretical Analysis
Authors: Rüetschi Paul , Delahay Paul
Published: April 2005

Variations of overvoltage for oxygen evolution from one metal to another primarily result from variations in the energy of the bond M–OH. The overvoltage decreases approximately in a linear manner with increasing bond energy. This relationship is verified experimentally for Ag, Au, Cd, Co, Cu, Fe, Ni, Pb, Pd, and Pt, for electrolysis in one N potassium hydroxide at one amp cm—2; the experimental data are those reported by Hickling and Hill. Bond energies for M–OH are calculated by three different thermodynamic cycles involving, respectively, the standard heat contents of the hydroxide, the oxide, and spectroscopic data for molecules MO. Variations of the energy of the bond M–OH, as the electrode is oxidized to a higher valence, also account for sudden breaks in plots of overvoltage against logarithm of current density. Finally, there is essentially no correlation between the oxygen overvoltage for different metals and the corresponding work functions.
On the Structure of the Configuration Integral in the Statistical Mechanics of Pure Fluids
Authors: Widom B.
Published: April 2005

A form for the configuration integral is postulated. Its most important feature is the location of its zeros and poles in the complex volume plane. These lie on a contour which divides the real axis into distinct regions. The pressure, being expressed as an integral taken over this contour, can have different analytic forms on different parts of the real volume axis. It is shown that the asymptotic nature of a configuration integral of the assumed form is determined by the p—v isotherms it produces, and the theory is worked out for isotherms derivable from a function of the van der Waals type with a classical critical point. The contour on which the zeros and poles of the configuration integral lie, and the density with which they are distributed, are determined explicitly in terms of these isotherms. The theory is illustrated in detail in the case of a simple equation of state.
Normal Coordinate Treatment of Dimethyldiacetylene
Authors: Weber Alfons , Ferigle Salvador M.
Published: April 2005

A normal coordinate treatment for dimethyldiacetylene is carried out, using Wilson's FG-matrix method in conjunction with the ``splitting out'' technique. All the potential constants have been transferred from similar molecules and the agreement between calculated and observed frequencies is good, the largest deviation being 2.3 percent. The observed fundamentals are a1—2914, 2264, 1381, 1228, and 554 K; ā2—2947, 2163, 1379, and 941 K; e—2947, 1458, 1030, 353, and 104 (calculated) K; and ē—2953, 1426, 1022, 475, and 247 K.
Fluorescent Behavior of Solutions Containing More than One Solvent
Authors: Furst Milton , Kallmann Hartmut
Published: April 2005

Fluorescent emission of organic solutions in combinations of solvents is investigated in order to determine the reasons for the suitability or unsuitability of solvents for high-energy induced fluorescence, particularly where these solvents do not influence the emission under ultraviolet irradiation. Basically two types of behavior under high-energy radiation are found in these combined solvent solutions. In type I a considerable drop in emitted intensity occurs only when the amount of the ``poor'' solvent greatly exceeds that of the ``effective'' solvent, whereas in type II small amounts of added ``poor'' solvent produce large decreases in emitted intensity. The fluorescence depends upon the concentration of solute, larger concentrations giving greater light outputs. The results obtained are explained by assuming that energy transfer occurs from the ``poor'' solvent to the ``effective'' one. At the same time a decrease in actual lifetime of excitation in the ``effective'' solvent occurs which is induced by the presence of the ``poor'' solvent molecules. This shows up as a quenching of the gamma-ray induced fluorescence in solutions even with solutes which are scarcely quenched at all under ultraviolet light excitation. For type I behavior this quenching is small while for type II it is considerable.
Surface Tension and Viscosity of Liquids
Authors: Simons J. H. , Wilson W. H.
Published: April 2005

Empirical relationships have been found between energy of vaporization, surface energy, energy of activation of viscosity, and the boiling temperature. This has been done by first considering the inert gases as the simplest type of liquid. ΔEvap=σbAb+12RTb. ΔEvis=1.212RTb1.2. For the simplest type of polyatomic substance the normal fluorocarbons give ΔEvap=σbAb+12RTb+1.212RTb1.2, ΔEvis=1.212RTb1.2. The normal hydrocarbons give, as expected, liquids whose properties differ from those of the normal fluorocarbons. ΔEvap=σbAb+1.212RTb1.2. ΔEvis=1.212RTb1.2−1000. For normal heptane it is shown that ΔEvap=σA+1.212RT1.2 may be taken at temperatures other than Tb. Suggestions are given for theoretical reasons for these equations.
Molecular Clusters in Imperfect Gases
Authors: Hill Terrell L.
Published: April 2005

An exact, formal method for calculating the number of physical (as contrasted with Mayer's mathematical) clusters in an imperfect monatomic gas is developed. However, although the equations are exact, the definition of a physical cluster is somewhat arbitrary. This arbitrariness does not affect any of the purely thermodynamic properties of the gas. A particular pair-wise definition of physical clusters is discussed in some detail and compared with Mayer's pair-wise definition of mathematical clusters.
Influence of Vibration-Rotation Interaction on Line Intensities in Vibration-Rotation Bands of Diatomic Molecules
Authors: Herman Robert , Wallis Richard F.
Published: April 2005

The influence of vibration-rotation interaction on line intensities in vibration-rotation bands of diatomic molecules had been recognized and treated approximately many years ago. In the present paper matrix elements have been calculated for the P and R branches of the 0—1, 0—2 and 1—2 transitions taking into account the interaction of rotation and vibration as well as the mechanical and electrical anharmonicity. For the 0—1 and 1—2 transitions the intensities of corresponding absorption lines in the P and R branches are proportional, in first order approximation, to [1+4γθJ]J and [1—4γθ(J+1)](J+1), respectively, where J is the rotational quantum number of the initial state, γ=2Be/ωe, θ=M0/M1re and M0 and M1 are the first two coefficients in the electric dipole moment expansion about the equilibrium internuclear distance re. Corrections to the above expressions that are proportional to γ2 have also been obtained. Formulas are given for the total integrated band intensity and for the line intensities summed over each branch taken individually. In the case of certain molecules, such as HCl for which θ≅1, it is possible to determine the magnitude of sign of θ by applying the above analyses to experimental data. For molecules such as CO, where θ≪1, the effect is negligible for the fundamental transition. A semiclassical interpretation of the influence of vibration-rotation interaction on line intensity has also been given.
Experimental Study of the Mechanism of Thermoluminescence in Irradiated Sodium Chloride
Authors: Hill J. J. , Schwed P.
Published: April 2005

The general configuration of the emission spectrum of synthetic NaCl crystals which had been irradiated with 7 × 105r of x-rays at room temperature and were then permitted to luminesce at 500°K was determined, and bands were located with maxima at 362, 418, 432, and 525 millimicrons. The glow curves for NaCl crystals irradiated with x-rays or ultraviolet light were investigated, and eight bursts of light (glow peaks) were found with peaks at temperatures between 334 and 625°K. The relative contribution of the different bursts to the total glow curve was determined as a function of the amount of x-ray irradiation. The activation energies for five of the bursts were measured and in each case turned out to be about 1.25 ev. It is suggested that these results indicate that the thermoluminescence takes place by means of a two-stage process of the following sort. The first stage, which is the same for all the bursts and is thermally activated with the measured activation energy, takes place when trapped electrons are raised from F-centers into the conduction band. In the second stage, electrons in the conduction band fall into different empty energy levels, there being one type of level for each burst. The large observed differences between the peak temperatures of the different bursts is then due to large variations in the probabilities of this second process for different levels.
Equation of State and the Thermal Dependence of the Elastic Coefficients of Crystalline Argon
Authors: Henkel John H.
Published: April 2005

An interaction potential of the form A/R10—B/R6 for two argon atoms is assumed. The values of A and B are evaluated using the heat of sublimation and the lattice constant at temperature T=0°K and pressure p=0. By assuming that each atom moves in a potential field because of all the other atoms at rest in their mean positions, a theory is developed for anharmonic vibrations using the perturbation theory for a harmonic oscillator. The partition function for each argon atom is obtained and the equation of state is calculated. The specific-heat equation obtained represents a correction of the Einstein form. The specific heats at constant pressure are calculated as a function of temperature and deviate from the experimental ones by only 3 percent at low temperatures (15°K—30°K) and only 1 percent at higher temperatures. The isothermal elastic coefficients C11, C12, and C44 are calculated by Born's method without neglecting the part played by the thermal energy. The Cauchy relation is found to be invalid, C44 being about twice C12 at the higher temperatures.
Substituted Methanes. XXV. Potential Constants and Calculated Thermodynamic Properties of Dibromofluoromethane
Authors: Murata Hiromu , Palm Ann , Meister Arnold G.
Published: April 2005

On the basis of previous Raman data, a reasonable set of potential constants was calculated for CHFBr2 by the Wilson method, assuming a most general quadratic potential energy function. The thermodynamic properties—heat content, free energy, entropy, and heat capacity—for the ideal gaseous state at 1 atmos pressure were computed for 12 temperatures from 100 to 1000°K.
On the Electronic Structure and Electronic Spectra of Ethylene-Like Molecules
Authors: Parr Robert G. , Pariser Rudolph
Published: April 2005

A previously given theory of the electronic spectra and electronic structure of complex unsaturated molecules is applied to ethylene-like molecules, molecules such as ethylene itself, propylene or formaldehyde, which have two π electrons and two atomic π orbitals available for π-bond formation. Relations are derived among electronic excitation energies, intensities of electronic transitions, extra-ionic resonance energies and dipole moments of such molecules. Relative electronegativities are shown to play an important role in these relations, where the effective electro-negativity of an atom is Mulliken's electronegativity (the mean of the appropriate atomic valence-state ionization potential and electron affinity) plus the total attraction of the valence electron of the atom for all other atoms in the molecule.

The analysis yields the result that the dipole moment due to a slight bond heteropolarity is proportional to the electronegativity difference of the bonded atoms, the extra-ionic resonance energy to its square. Proportionality factors are given absolutely by the theory. It is pointed out that the theory of a two-electron σ bond is formally the same, moreover, so that a derivation is provided for the familiar electronegativity relations of Pauling. Theoretical and empirical values for the proportionality factors are found to agree reasonably well for both π bonds and σ bonds.

The formulas given cover multiple perturbations of any type which may be considered not to add (or subtract) π electrons or π orbitals. They thus provide a scheme for quantitative evaluation of inductive effects in ethylene-like molecules. Systematic consideration of mesomeric effects is deferred, but an outline of the procedure which may be used for their study is given, using mono-substituted ethylene as an example.

To illustrate the use of the formulas, to bring out the relationships between the method and the work of other authors, and to see whether the method has promise for σ-electron systems, calculations are made of the electronic spectrum of ethylene, the twisting force constant of ethylene, the ionization potential and electron affinity of ethylene, the electronic spectrum and dipole moment of formaldehyde, and the electronic spectrum, ionization potential, and binding energy of the hydrogen molecule.
Measurement of Bond Moments in C2H2 and C2D2 from Infrared Intensities
Authors: Wingfield Edward C. , Straley Joseph W.
Published: April 2005

The absolute infrared absorption intensities in the active bending vibration ν5 in C2H2 and C2D2 have been measured using the extrapolation method of Wilson and Wells. The intensities observed are A5(C2H2) = 2170×1010 cycles/sec cm at NTP and A5(C2D2) = 1040×1010 cycles/sec cm at NTP. These values indicate the bond moment associated with the CH and the CD bonds are μCH=0.999±0.035 debye and μCD=0.941±0.033 debye, respectively.
Mean Amplitudes of Thermal Vibrations in Polyatomic Molecules. III. The Generalized Mean Amplitudes
Authors: Morino Yonezo , Hirota Eizi
Published: April 2005

James' theory of the effect of molecular vibrations upon the diffraction pattern is revised and extended, including the parallel as well as perpendicular vibrations of atom pairs. Corresponding to these vibrations the mean square amplitudes, parallel and perpendicular, and the mean cross products are defined, and a method of calculating them by means of normal modes of vibration is derived. At the same time the effect of molecular symmetry upon mean amplitudes is discussed with the result that some of them are essentially reduced to zero because of the symmetry.
Theory of the Lower Excited Electronic States of the Benzene Crystal
Authors: Fox David , Schnepp Otto
Published: April 2005

For the two lowest exciton bands of benzene, calculations have been carried out for the band widths and for the energies of the levels to which dipole transitions from the ground state are allowed. Expressions have been derived for the intensities of crystal transitions corresponding to both allowed and forbidden molecular transitions and have been applied to the case of the benzene crystal. Comparison is made with available experimental data and additional experiments are suggested so that further comparison may be made. From the band widths, evidence is obtained that the lowest excited state of the benzene molecule belongs to the B2u representation of the molecular group, D6h.
Charge Transfer Reactions in Monatomic and Diatomic Gases
Authors: Dillon J. A. , Sheridan W. F. , Edwards H. D. , Ghosh S. N.
Published: April 2005

Cross sections for charge transfer reactions between ions and neutral atoms and molecules have been measured in the energy range from 50 to 850 ev. Charge transfer cross sections for symmetrical reactions in monatomic and diatomic gases increase with increasing viscosity cross sections. The charge transfer cross sections decrease with increasing incident ion energy in conformity with the adiabatic criterion. For reactions in diatomic gases the charge transfer cross sections decrease as the changes in internuclear distance for the processes increase.
Crystal Structure and Quadrupole Coupling of Cyanogen Bromide, BrCN
Authors: Geller S. , Schawlow A. L.
Published: April 2005

The crystal structure of BrCN has been determined from single-crystal x-ray data. BrCN belongs to space group D2h(13) — Pnmm, with two molecules in a unit cell of dimensions: a=5.80, b=6.02, c=4.12 A (all ±0.03 A). All atoms are in positions 2(a): ±(x, ¼, ¼) with parameters xbr=0.144, xC=0.45, and xN=0.65. The structure is made up of straight chains of BrCN molecules directed along the a-axis with the bromine atom of one molecule bonding weakly to the nitrogen of the next molecule in the same chain. The structure is consistent with recent measurements of quadrupole coupling for the Br and N nuclei.
On First-Order Phase Transitions in Canonical and Grand Ensembles
Authors: Hill Terrell L.
Published: April 2005

S. Katsura has found evidence from exact calculations on finite systems that has led him to suggest that, contrary to the generally accepted view, a van der Waals type loop will be found in an exact application of the canonical ensemble to a first-order phase transition. It is shown here that Katsura's results can be understood in terms of interfacial free energy in the two-phase region. A loop is indeed obtained, but it is not of the van der Waals type. In particular, the loop vanishes in the limit of an infinite system. The well-known argument of van Hove showing that a loop does not exist in an infinite system (canonical ensemble) is discussed in this connection.
Photochemical Decomposition of Aqueous Permanganate Ion
Authors: Zimmerman George
Published: April 2005

Quantum yields for the photochemical decomposition of aqueous MnO4— have been measured under a variety of conditions using a sensitive method for measuring O2 production, first developed by Pringsheim and co-workers. The quantum yield was found to depend strongly on the wavelength of the light, slightly on temperature at the longer wavelengths, and not at all on the composition of the solution or on light intensity. Additional experiments were carried out which showed that the isotopic composition of photochemically produced O2 was independent of the O-isotopic composition of the solvent water. These results lead to the conclusion that the radiant energy absorbed by the MnO4— ion is converted with high probability into vibrational energy of the ground state, after which the ion dissociates thermally into MnO2 and O2 (in a single act) or cools down without dissociation (the position of the extra electron is uncertain). A possible quantitative theory which predicts fairly successfully the dependence of the quantum yield on wavelength is outlined.
Substituted Methanes. XXVI. Raman and Infrared Spectral Data, Assignments, Potential Constants, and Thermodynamic Properties for CHBrCl2 and CDBrCl2
Authors: Polo Santiago R. , Palm Ann , Voelz Fred L. , Cleveland Forrest F. , Meister Arnold G. , Bernstein Richard B. , Sherman Robert H.
Published: April 2005

Raman displacements, semiquantitative relative intensities, and quantitative depolarization factors for liquid bromodichloromethane and deuterobromodichloromethane, as well as infrared wave numbers and percent transmission curves for both the liquid and gas in the region 400—4000K (K = kaysers = cm—1), were obtained and compared with previous data. Assignments were made for both molecules and a reasonable set of potential constants was determined by use of Wilson's FG matrix method. The heat content, free energy, entropy, and heat capacity were calculated for 12 temperatures from 100° to 1000°K.
Interrelation of Gaseous Viscosity, Self-Diffusion, and Isotopic Thermal Diffusion
Authors: Holleran Eugene M.
Published: April 2005

The general interrelation of the theoretical first approximations to viscosity, self-diffusion, and thermal diffusion previously derived is modified to conform with a simpler and more accurate approximation for the thermal diffusion ratio due to Kihara. The accuracy and limitations of this interrelation are discussed, with particular regard to the effect of considering higher approximations to the transport properties. With the recently published results for the modified Buckingham potential as a guide, the relation is further simplified, leading in particular to an approximate relation between viscosity and thermal diffusion which is shown to be in good agreement with the experimental data for argon.
Spectra and Electronic Structure of Fluorochromate Ion, Chromyl Chloride, and Some Related Compounds
Authors: Helmholz Lindsay , Brennan Harry , Wolfsberg Max
Published: April 2005

A semiempirical treatment, which gives satisfactory agreement between calculated and observed spectra for chromate and permanganate ions, has been employed to calculate the excited state energies and transition moments for the related molecules of the chemical formulas CrO3X— and CrO2X2. The results show agreement with experimental data which unfortunately are not extensive for these molecules. The calculations indicate an absorption for SO2Cl2 in the farther ultraviolet in agreement with experiment. The qualitative significance of the results, so far as the relative importance of σ and π bonding, is discussed.
Thermal Accommodation Coefficient of Helium on a Bare Tungsten Surface
Authors: Thomas Lloyd B. , Schofield E. B.
Published: April 2005

The accommodation coefficient of helium on a presumably clean tungsten surface is determined from 83° to 303°K. A getter technique is applied in which, after thorough baking of the tube and vacuum system, aluminum is evaporated in vacuum over the inner walls of the measuring tube. The technique appears to be superior to the circulation over charcoal used by Roberts. Clean surface values of the accommodation coefficient, found by linear extrapolation to time of flashing the filament, lie between 0.0151 and 0.0172 (with small positive corrections probably to be applied). The variation with temperature is small and the values themselves are much lower than any heretofore reported.
Proton Magnetic Resonance in Liquid Crystals—Orientation Effects
Authors: Jain P. L. , Lee J. C. , Spence R. D.
Published: April 2005

This communication reports a study of the proton magnetic resonance signal from the liquid crystal phase of 4-4′ methoxyazoxybenzene, 4-4′ methoxy D3 azoxybenzene, and 4-4′ ethyoxyazoxybenzene in an effort to obtain information concerning the temperature dependence and relative extent of the molecular orientation in such phases. The experimental results lead to a qualitative picture of the distribution of molecular orientations for the first two compounds and show that the extent of orientation in the last compound is greater than in the first two.
Infrared Spectrum of Trideuterosilane and the Structure of the Silane Molecule
Authors: Boyd D. R. J.
Published: April 2005

SiD3H has been prepared by the action of lithium aluminum deuteride on SiCl3H. A parallel type absorption band has been studied with a high-resolution infrared spectrometer. Analysis of the rotational fine structure of the band gave B0 = 1.7755±0.0008 cm—1. If the assumption is made that the structural parameters of the ground state of SiH4 are unaltered by the substitution of D for H, the Si–H internuclear distance is found to be 1.4798±0.0004 A. This is appreciably greater than 1.456 A which is accepted at present.
Ultraviolet Absorption Spectra of Methylnaphthalenes at 77°K
Authors: McConnell H. M. , Tunnicliff D. D.
Published: April 2005

A simple and reliable apparatus has been developed for the determination of low-temperature ultraviolet absorption spectra in rigid glass media. This apparatus is particularly suitable for the measurement of accurate absorption intensities and has been used for the determination of the ultraviolet absorption spectra of naphthalene, 2-methylnaphthalene, and 2,6-dimethylnaphthalene at the temperature of boiling nitrogen (77°K). A comparison of these low-temperature spectra provides evidence that the electronic transition of naphthalene in the 2900—3200 A range is symmetry allowed.
Infrared Spectra and Structure of NaOH and NaOD
Authors: Busing William R.
Published: April 2005

The infrared spectra of NaOH, NaOD, and mixtures of these compounds have been studied at room and liquid air temperatures. The results at room temperature, taken together with the Raman spectrum of NaOH, are consistent with the x-ray structure and hydrogen positions postulated in the present work. At liquid air temperature the spectrum of NaOD shows an unexpected complexity which cannot be explained at present.
Electronic Structure of Metal bis-cyclopentadienyls
Authors: Dunitz J. D. , Orgel L. E.
Published: April 2005

Molecular orbital theory has been used to describe the electronic structure of ferrocene and related compounds. It is shown that, provided the valence-state promotion energies are considered, the thermochemistry and magnetic properties may be understood.
Measurement of the Magnetic Susceptibility of Manganese Nitride Mn5N2 by a Microvibration Method
Authors: Yousef Y. L. , Girgis R. K. , Mikhail H.
Published: April 2005

The susceptibility-temperature relationship of carefully prepared manganese nitride Mn5N2 was measured over the temperature range —180°C to 530°C. The Curie-Weiss law χ=C/(T—θ) was found to hold, with θ=—1070 and C=0.0316 emu deg/g. The effective Bohr magneton number is 3.94 per Mn, and is in reasonable agreement with the theoretical value 3.87 for 3 unpaired electrons. This suggests that Mn5N2 behaves as a coordination compound with 4 electron-pair bonds.

A new microvibration technique, particularly suitable for susceptibility investigations of materials available in small amounts, has been developed for the present work. The underlying principle is to modulate the magnetic field and to translate the periodic force on the material into a periodic displacement of an elastic strip. The force is measured dynamically in terms of a compensating electrostatic force, an electronic circuit being used as a null detector. Accuracy to 10—4 dyne is claimed.
Studies of the Interaction between Stable Molecules and Atoms. I. A Molecular Orbital Theory of the Activation Energy between Molecules and Atoms
Authors: Griffing Virginia
Published: April 2005

The molecular orbital method of calculation is applied to the interaction between closed-shell species; the results discussed in this paper and presented in the following papers of this series indicate that this method will yield quantitative results for energies of a system as function of internuclear parameters if one is interested in the differences in energy for two different geometric ground state configurations of the system. The molecular orbitals are used as a basis of constructing correlation diagrams for predicting mechanisms and calculating activation energies for chemical reactions. The orbitals of the reactants and products are correlated with the orbitals of a state defined as the ambivalent complex. The low-lying excited states of the interacting molecules seem to be of importance in determining the activation energy of a chemical reaction. Considerable qualitative insight into the activation process is gained by this method; the relative values of the activation energies for the interaction between two closed-shell molecules, a molecule and a radical, and two radicals are predicted in agreement with experiment.
Studies of the Interaction between Stable Molecules and Atoms. IV. The Energy of the Linear H4 Complex
Authors: Griffing Virginia , Vanderslice Joseph T.
Published: April 2005

Roothaan's LCAO—SCF treatment has been applied to the linear symmetrical H4 complex in an attempt to test this method for calculating the energies of activated complexes. Calculations have been made for internuclear distances of 1.4, 1.6, 2.0, and 2.2 a.u. The SCF method gives a lower value for the energy of 1.4 a.u. than was obtained by a simple molecular orbital method without configuration interaction, but gives a higher value than the best configuration interaction treatment. The values of the energies that were obtained are —55.48, —55.99, —56.50, and —56.54 ev at distances of 1.4, 1.6, 2.0, 2.2 a.u., respectively. The changes in the wave functions as one adiabatically changes the internuclear distance are of particular interest. Although the results cannot be directly compared with experiment, reasonable values for the energy are obtained indicating that the molecular orbital SCF method with a limited amount of configuration interaction is a promising method for treating closed-shell molecules and interactions between such molecules for small values of the internuclear parameters.
Studies of the Interaction between Stable Molecules and Atoms. V. Molecular Orbital Approach to the H+H2 Reaction
Authors: Griffing Virginia , Vanderslice Joseph T.
Published: April 2005

In an attempt to find a relatively simple way of calculating activation energies for chemical reactions, Roothaan's LCAO-SCF method has been applied to the linear H3 complex. Since Roothaan's method has been developed for closed shells, a self-consistent field treatment has been done on the linear H3— complex. According to Roothaan, the energy of the H3 should be equal to a first approximation to the energy of the H3— minus the energy required to remove one electron. Calculations have been made at distances ranging from 1.4 to 2.5 atomic units and for various values of the screening constant. Correlation diagrams for the reaction H+H2 have been constructed and the activation energy calculated. The method gives considerable insight into charge distribution but is unsatisfactory for calculating good energy values. The results are compared with experiment and with values calculated by the MO-configuration interaction method which yields a value of 8.76 kcal/mole.
Long Time Phosphorescence of Organic Crystals
Authors: Kallmann Hartmut , Kramer Bernard , Sucov Eugene
Published: April 2005

Long time phosphorescence (of the order of minutes) of anthracene, stilbene, durene, and naphthalene crystals at room temperature is reported. The decays are approximately hyperbolic and the observed phosphorescence is shifted to longer wavelengths than the usual fluorescent emission. This phosphorescence is not induced by the light strongly absorbed in the substance but mainly by the weak absorption of light of wavelengths corresponding to their own fluorescent light. There are indications that this phosphorescence stems from an approximately uniform, continuous trap distribution and that such a mechanism permits a description of some of the observed behavior. Wavelength measurements seem to indicate that this phosphorescent light emission does not originate from triplet to ground transitions.
Calculation of Thermodynamic Properties of Polyelectrolytes
Authors: Marcus R. A.
Published: April 2005

Expressions are derived which introduce an appreciable simplification into the calculation of the thermodynamic properties of solutions of polyelectrolytes in certain cases. For example, for a certain class of theoretical models of these systems it is found that the square of the mean ion activity coefficient of a uni-univalent salt in the presence of polymeric ions is V2/ ∫ e−eψ/kTdV· ∫ eeψ/kTdV, the integration of the potential ψ being over a region whose volume is the volume of solution per macro-ion, V, and whose symmetry is that assumed for the polyelectrolyte. The osmotic pressure of a salt-polyelectrolyte system is, ignoring the contribution of the macro-ion, estimated to be Σi ciskT, where Σi cis is the sum of the concentrations of all ions at the surface bounding the previously defined volume V. Other relations and various applications are given. The activity coefficient of salt in the presence of polyelectrolytes, calculated by extending the ``parallel rod'' picture of polymeric ions, is found to be in reasonable agreement with the experimental data. The use of the Poisson-Boltzmann equation to estimate ψ in these systems is shown not to render inconsistent several alternative expressions for the electrostatic contribution to the free energy.
Photochemical Studies of the Porphyrins. III. Photoreduction of a Porphyrin by Benzoin
Authors: Seely Gilbert R. , Calvin Melvin
Published: April 2005

An examination of the kinetics of the photoreduction of zinc tetraphenylporphin by benzoin is reported. The products are successively the dihydro- (chlorin) derivative; a tetrahydro-derivative and possibly a hexahydro compound as well. It is demonstrated that the primary requirement is the photoactivation of the benzoin; a secondary reaction, involving photoactivated porphyrin as well, is also demonstrated. The quantum yield based on light absorbed by benzoin varies between 0.01 and 0.06.
On the Logarithmic Rate Law in Chemisorption and Oxidation
Authors: Landsberg P. T.
Published: April 2005

It is shown that the logarithmic rate law is found very widely in chemisorption and oxidation. A theory of this law is offered, and comparison with experiment leads to reasonable values for the parameters. Although the theory is very elementary, it is hoped that the physical interpretation it provides of experimentally determined parameters will encourage a more detailed study of these, for instance as a function of temperature and ambient pressure.
One-Dimensional Model of the Hydrogen Bond
Authors: Lippincott Ellis R. , Schroeder Rudolph
Published: April 2005

A one-dimensional model for hydrogen bonding is proposed based on the potential function V = D[1—exp(—nΔr2/2r)]. The energy associated with both the weak and strong bonds of the configuration RO – H – – – OR2 is obtained through application of this function. A repulsive Van der Waals potential and an attractive electrostatic potential are also assumed to exist between the two electronegative atoms of the hydrogen bond. Through application of the conditions describing a stable equilibrium, relations are obtained which permit a calculation of OH frequency shifts, OH bonded distances, hydrogen bond energies and ko — — — o force constants, all as a function of the O – – – O distance R. The calculated quantities agree well with those obtained from neutron diffraction, infrared, and other experimental studies. Because of the assumptions involved, this model is best used to describe the properties of hydrogen bonds in crystals. The model is also capable of extention to describe the properties of other types of hydrogen bonds such as HFH, NHN, NHO, OHN, etc.
Treatment of Isotopic Exchange Reactions Having Complex Mechanisms
Authors: Marcus R. A.
Published: April 2005

The reaction rate vs time data of isotopic exchange reactions have been shown by previous work to obey a first-order rate law, neglecting differences in isotopic reactivity. A simple method, of use in reactions having complex mechanisms, is developed for relating this first-order rate constant to the rate constants of elementary steps in the process. The method involves examining the progress of specified atoms through the reaction sequence, and is applicable regardless of the number of exchange positions of the reactants, or of whether or not one isotope is present in tracer amounts. These results are used to reinterpret some data on the deuteration of diborane.