bluuebunny/crossref_metadata_2025 huggingface dataset:
An NMR Study of Indene Using a Proton-Proton Decoupling Technique
Authors: Elleman Daniel D. , Manatt Stanley L.
Published: January 2005

The 60 Mc/sec high-resolution NMR spectrum of the protons of the five-membered ring of indene[Complex chemical formula]has been studied with the aid of the audio sideband phase detection proton—proton spin decoupling technique. The chemical shifts and the spin—spin coupling constants have been measured. The relative sign of the spin coupling constant JAX was determined to be different than that of JAK and JKX by double irradiation experiments. Certain long-range couplings of the aromatic protons with the five-membered ring protons were detected.
Ring Currents in Aromatic Molecules
Authors: Maddox I. J. , McWeeny R.
Published: January 2005

Pauling's semiclassical model, in which the diamagnetic susceptibility of an aromatic molecule is attributed to ring currents, is re-examined. The ring currents in a family of hexagonal polycyclic systems are inferred from quantum-mechanical calculations and are compared with the semiclassical estimates. The Pauling model is found to be unsatisfactory for systems containing more than two or three rings, giving currents which are much too large.
On the Application of Bethe's Method to the Grand Canonical Ensemble for a Fluid
Authors: Baer Shalom
Published: January 2005

The grand partition function for a large fluid system is expressed in a form equivalent to a grand partition function for a small volume v including factors representing the effect of the surroundings on the distribution inside v. An explicit expression for these factors is found by making a general assumption concerning the interaction of molecules inside v with the rest of the fluid. The molecular distribution inside v is then completely determined by one function which is a solution of an integral equation containing in its terms up to n-time integrals, where n is the maximum number of molecules which can occupy v simultaneously. The nature and efficiency of the approximation are discussed.
On the Self-Diffusion of Ions in a Polyelectrolyte Solution
Authors: Lifson Shneior , Jackson Julius L.
Published: January 2005

The self-diffusion of ions in a polyelectrolyte solution is investigated both with respect to the average time an ion is associated with a particular polyelectrolyte molecule and with respect to the effect of the electrostatic field of the macro-ions on the macroscopic self-diffusion constant. The results on the macroscopic self-diffusion constant are shown to be generally compatible with experiments on self-diffusion of counterions in polyelectrolyte solutions. On the other hand, the study of the time of association of a counterion with a particular macro-ion yields results which cannot be reconciled with the common interpretation of transference experiments on the same solutions.
Heat Capacities and Thermodynamic Properties of Two Tetramethylammonium Halides
Authors: Chang Shu-Sing , Westrum Edgar F.
Published: January 2005

Heat capacities of tetramethylammonium chloride and bromide were determined by low-temperature adiabatic calorimetry from 5° to 350°K. Derived thermodynamic properties were then calculated. Two transitions were found in the chloride: a sharp, apparently first-order transition occurs at 75.76°K with an entropy of transition of 0.37 cal mole—1 °K—1 and a lambda-shaped transition at 184.85°K with an entropy increment of 0.14 cal mole—1 °K—1. No anomaly has been observed in the bromide. Molal values of heat capacity, entropy, and free energy function at 298.15°K for the chloride and the bromide are: 37.51, 38.64, 45.58, 47.99, and —23.36, —25.36 cal mole—1 °K—1, respectively.
Two-Center, Nonintegral, Slater-Orbital Calculations: Integral Formulation and Application to the Hydrogen Molecule-Ion
Authors: Geller Murray
Published: January 2005

Integrals over Slater orbitals of nonintegral principal quantum numbers centered at two nuclei are investigated, with special reference to the hydrogen molecule-ion. All the one-electron integrals for s orbitals are evaluated in closed form. For the hydrogen molecule-ion, a wave function of the generalized Finkelstein—Horowitz form ψ=nsa+nsb, where ns=Nrn—1e—ζr, N being the normalization constant, n the principal quantum number, and ζ the orbital exponent, is shown to give a total energy E=—0.588085 a.u. for n=1.05759 and R=1.9866 a0 as compared with the corresponding Finkelstein—Horowitz calculation E=—0.586507 a.u. at n=1 and R=2.0033 a0, where the exact values are E=—0.60263 a.u. at R=2.000 a0. More general one-electron integrals and some two-electron integrals are discussed.
Dielectric Relaxation in Liquid Alcohols and Diols
Authors: Sagal Matthew W.
Published: January 2005

The temperature dependence of the dielectric relaxation time has been investigated from —5° to 50°C for ethanol—cyclohexane solutions from 1.0 to 0.25 mole fraction ethanol. The previously observed maximum in the relaxation time around equimolar composition is explained by a hydrogen-bonded switching mechanism.

Measurements of dielectric relaxation from 5° to 50°C have been carried out on three isomeric butanediols which differ in the separation of the two OH groups along the carbon skeleton. The differences in relaxation times among the three isomers can be explained by the switching mechanism suggested by the results for the ethanol—cyclohexane solutions.

The dielectric relaxation times of n-butanol from 5° to 50°C have also been determined. The chain-length dependence of the dielectric relaxation time of the normal aliphatic alcohols is discussed in terms of the proposed mechanism.
Chemical Shifts and Ring Currents in Condensed Ring Hydrocarbons
Authors: Jonathan Neville , Gordon Sidney , Dailey B. P.
Published: January 2005

A complete analysis has been made for each of the high-resolution proton magnetic resonance spectra of naphthalene, anthracene, pyrene, perylene, triphenylene, and coronene at infinite dilution in CS2 or CCl4. A partial analysis has been made for phenanthrene. The analyses yield absolute values for the chemical shifts and spin coupling constants. A correlation has been made between the π-bond order of the particular (C–C) bond and the spin coupling constant. Theoretical values for the ``ring current shifts'' were obtained using London type molecular orbital calculations. The agreement between experimental and theoretical values is satisfactory in that the relative positions of the proton shifts are correctly predicted in all cases.
Electronic Spectrum of Adsorbed Benzene
Authors: Ron A. , Folman M. , Schnepp O.
Published: January 2005

The electronic absorption spectrum of benzene adsorbed on porous Vycor glass was investigated in the near ultraviolet between room and liquid-hydrogen temperatures. The spectrum consists primarily of absorptions characteristic of the gas phase with additional features which are interpreted as characteristic of the adsorbed state. Adsorption isotherms for the system were measured and from these the isosteric heat of adsorption and entropies of adsorption for two models calculated. The entropies of adsorption for the same two models were calculated statistically and from comparison between experimental and theoretical entropy values it is concluded that the ``mobile gas'' model is more nearly applicable here.
Effect of Anharmonic Vibrations on the Bond Lengths of Polyatomic Molecules. I. Model of Force Field and Application to Water
Authors: Kuchitsu Kozo , Bartell L. S.
Published: January 2005

The detailed information on molecular force fields required for precise determinations of molecular structure is only rarely available for polyatomic molecules. A model of the force field is therefore proposed from which the cubic potential constants may be estimated from commonly available data. The potential energy is represented by a modified, anharmonic Urey-Bradley field in which the stretching and nonbonded potentials are assumed to have the Lippincott and Buckingham forms, respectively, and in which stretch-stretch interactions are included.

The model is applied to H2O and D2O, for which exceptionally complete spectroscopic data are available for comparison, and is found to give cubic constants in satisfactory agreement with experiment. The cubic constants thus estimated are used to evaluate the effect of zero-point vibrations on the internuclear distances and rotational constants of water by a first-order perturbation treatment. The resultant mean distances and mean amplitudes are in good agreement with those of Reitan's second-order treatment using the experimental cubic constants, and the rotation-vibration constants α agree satisfactorily with Benedict's experimental values.
Higher Ionization Potentials of NO2
Authors: Tanaka Y. , Jursa A. S.
Published: January 2005

The spectrographic method of observing Rydberg series has been used to investigate higher ionization potentials of NO2. The most significant result was the determination of a new ionization potential at 18.87 ev. Four Rydberg series which converged to this limit were identified.

Other ionization potentials at 11.62 and 12.3 ev are discussed. No evidence was obtained which would indicate the existence of an ionization potential at 13.98 ev reported by others, nor was there any indication of an ionization potential at 17.5 ev, which is predicted theoretically.
Relation between Ultrasonically Measured Properties and the Coefficients in the Solid Equation of State
Authors: Overton William C.
Published: January 2005

A relation is found by straight forward thermodynamic methods between the derivatives with respect to pressure of the isothermal and adiabatic bulk moduli which gives (∂BT/∂p)T at zero pressure from the experimental (∂Bs/∂p)T plus temperature-dependent-only thermodynamic properties. Although BT(∂Bs/∂p)T for Cu, Ag, Au, Al, NaCl, and Na. The coefficients a1 and a2 in the equation of state are evaluated from ultrasonic experimental data and compared with those obtained by experiments in high pressure physics. Agreement between the a1's is good but between the a2's it is poor.
Conductance of NaI–C2H5OH Systems in the Vicinity of the Critical Temperature
Authors: Allen Peter E. M. , Benson Sidney W. , Copeland Charles S.
Published: January 2005

Measurements are reported for the conductivities of liquid- and vapor-phase solutions of NaI in C2H5OH in the range of the critical temperature of C2H5OH and for very dilute NaI solutions. The equivalent conductance Λ is always much lower than the estimated value at infinite dilution. In the supercritical solutions, Λ is a very strong function of the solvent density. It is concluded that NaI is a very weak electrolyte in the supercritical solutions with a dissociation constant of less than 10—8.
Energy Moment Method Applied to Nuclear Quadrupole Splitting of Nuclear Magnetic Resonance Lines
Authors: Frank V.
Published: January 2005

Expressions giving the sum of the energy values, raised to the second and third power, for a nucleus interacting with a static magnetic field and a static electric field gradient are derived. Several applications of this method for obtaining the values of the components of the electric field gradient tensor from observed NMR spectra are suggested.
Phase Transitions in One-Dimensional Order—Disorder Systems: Application to Helix—Random-Coil Transition in Polymers
Authors: Baur M. E. , Nosanow L. H.
Published: January 2005

In this work a discussion is given of the present theory of the helix—random-coil transition in polypeptides. The seeming conflict between the description of this transition in terms of a one-dimensional model and the proofs that a phase transition cannot occur in a one-dimensional system is resolved. It is shown that the kind of interaction introduced in such models is singular and therefore falls outside the class for which the aforementioned proofs hold. A discussion is given of the mechanism of helix formation in the actual polymers, and it is shown how the description of the transition requires the use of such interactions. The properties which the singular interaction must have in order to cause a phase transition to occur in a one-dimensional discrete system are precisely stated and illustrated by simple examples. A general treatment of one-dimensional discrete systems with an arbitrary (but finite) range of interaction is given.
Chemical Bonding in the Perchromate Ion
Authors: Swalen J. D. , Ibers James A.
Published: January 2005

The perchromate ion, CrO83—, in K3CrO8 has D2d(4̄2m) symmetry and consists of a central pentavalent chromium ion surrounded by four peroxide groups. On the basis of a refinement of the previous structure determination, the chromium ion is nearer to one oxygen of each peroxide group than to the other and the peroxide oxygen—oxygen distance is shorter than normal. A ligand field calculation, based on the optical spectrum and the electron paramagnetic resonance spectrum, accounts for these structural features and leads to a description of the bonding in the perchromate ion.
Phase Studies of the Group IV-A Tellurides
Authors: Mazelsky R. , Lubell M. S. , Kramer W. E.
Published: January 2005

The mutual solubility of GeTe, SnTe, and PbTe was examined by x-ray diffraction techniques. The rhombohedral to cubic phase transformation of GeTe and GeTe in various solid solutions were determined. The transformation temperature is shown to vary inversely with cation mass.
Absorption Spectra of Gaseous Species Formed at Flash-Heated Solid Surfaces
Authors: Nelson L. S. , Kuebler N. A.
Published: January 2005

A method is described for recording the absorption spectra of gaseous atoms and molecules produced at strongly heated solid surfaces. A very intense pulse of light from a capacitor discharge lamp falls on light-absorbing grids placed in the absorption path of a spectrograph. The diameter of the grid windings is sufficiently small that their temperatures rise several thousand degrees very rapidly. The gaseous thermal species that are formed in the optical path arise from the following reactions: (1) vaporization of the grid material; (2) vaporization of coatings applied to the grids; and (3) reactions of the grids with a surrounding gas. Flash spectroscopic recording is used.

The following illustrations of the technique are presented: the formation of atomic tungsten by the vaporization of tungsten grids; the formation of AlCl by the evaporation of AlCl3 from carbon grids; and the formation of CH3, CD3, and CF2 by the reaction of heated carbon grids with CH4, CD4, and CF4, respectively.

Flash heating compares favorably with flash photolysis as a way to produce labile species for kinetic absorption spectroscopy. Parent molecules need not absorb in the near ultraviolet since the dissociative processes that occur are thermal rather than photolytic. Container problems for high-temperature studies are virtually eliminated because of the pulse nature of the experiment.
Recombination of Ions in Flames
Authors: King I. R.
Published: January 2005

A technique for measuring recombination rates in flames is described and some results showing the effect of temperature, pressure, and the presence of electronegative gases on recombination are presented. Experimental results are compared with predictions based on present-day theories of recombination. Results are interpreted in terms of an ion—ion process with recombination occurring most probably between an OH— and an H3O+ ion. The importance of electron attachment in such a process is emphasized.
Influence of a Second Radiofrequency Field on High-Resolution Nuclear Magnetic Resonance Spectra
Authors: Anderson W. A. , Freeman R.
Published: January 2005

A theoretical treatment of nuclear-magnetic double-irradiation experiments is given which is applicable to two groups of nuclei of arbitrary spin, either of different nuclear species or in a situation where the chemical shift is large in comparison with the spin-coupling constant. A convention is introduced whereby the group which experiences the ``strong'' rf field H2 is given the symbol X, while the group to be investigated is represented by A. Particular attention is given to groups of spin ½ nuclei in AnXm type molecules where m, n≤3, and their spin-decoupling behavior is presented in graphical form. Good correlations are observed with the experimental proton double-resonance spectra of acetaldehyde, diethyl succinate, and 1,1,2 trichloroethane. When a single X transition is irradiated with a very weak H2 a splitting of the A spin-multiplet lines into submultiplets is observed; at the same time an Overhauser-type redistribution of intensities may occur in certain molecules. Intermediate strengths of H2 centered on the X multiplet coalesce the A spectrum to what is essentially a single line for AXm molecules, but for AnXm molecules where n>1 there is a ``residual splitting'' which, although it decreases as H2 is made stronger, may never disappear completely. At high powers it is necessary to displace H2 slightly off resonance for group X towards the A resonance in order to obtain optimum decoupling, a correction which can be important in the accurate measurement of proton chemical shifts by spin-decoupling techniques.
Polyhedral Clathrate Hydrates. III. Structure of the Tetra n-Butyl Ammonium Benzoate Hydrate
Authors: Bonamico M. , Jeffrey G. A. , McMullan R. K.
Published: January 2005

The compound (n-C4H9)4N·C6H5COO·39½H2O forms tetragonal crystals with four molecules in the unit cell. The water structure is a hydrogen-bonded clathrate framework, in the cavities of which are located the tetra alkyl ammonium cations. The oxygen atoms of the benzoate anions are hydrogen-bonded to the water framework and form part of the polyhedral structure. This structure contains 10 pentagonal dodecahedra, 16 tetrakaidecahedra, and four pentakaidecahedra per unit cell. The 20 larger polyhedra are occupied by the 16 alkyl and four benzyl groups with a statistical disorder over two sets of equivalent cation and anion positions. There is evidence of additional hydrogen-bonded water inside some of the dodecahedra which are distorted due to the presence of the ions.

The clathrate framework is iso-structural with that of other salts in this series, which have a very similar tetragonal lattice but differ in containing five tetra n-butyl ammonium salt molecules per unit cell.
On the Theory of Vibrational Energy Exchange
Authors: Vanderslice Joseph T. , Weissman Stanley
Published: January 2005

The Schwartz—Slawsky—Herzfeld (SSH) theory of vibrational relaxation times assumes that the most effective relative kinetic energy for causing a vibrational transition is much greater than the quantum of energy transferred. For many actual cases, this assumption is not a good one. However, it appears that this approximation can be eliminated with little change in the resulting equations. The force law for N2, determined with the modified equations from the experimental data on relaxation times, does not differ appreciably from previous results.
Infrared Spectra of Liquid and Solid Carbon Monoxide
Authors: Ewing George E.
Published: January 2005

A low-temperature cell suitable for the study of the infrared spectra of pure liquids in the fundamental region is described. Selection rules are derived based on the assumption that diatomic molecules in the liquid state can undergo hindered rotation. The infrared absorption band shape is predicted to resemble the P- and R-branch envelope of the gas phase molecule in the wings, but to have an intense Q branch at the band center. The observed spectra of carbon monoxide as a liquid is in reasonable agreement with these selection rules. It is concluded that a considerable fraction of molecules in the liquid state can undergo nearly free rotation. The spectrum of carbon monoxide just below its freezing point suggests, however, that the rotatory motion of the molecules in the solid can best be described as librational.
Thermal Reactions of Isobutyl Radicals
Authors: Jackson W. M. , McNesby J. R. , Darwent B. deB.
Published: January 2005

Deuterium labeled isobutane (CH3)3CD was pyrolyzed to generate (CH3)3C and CH2CD(CH3)2 radicals. The competition between reactions (5) and (6) was studied by isotopic analysis of the hydrogen, methane, and isobutene fractions. CH2CD(CH3)2→CH2=C(CH3)2+DCH2CD(CH3)2→CH2=CDCH3+CH3.

Reaction (5) was found to be of negligible importance relative to reaction (6) up to 540°C and it is concluded that previous estimates of k5/k6 (in the nondeuterated species) are too high by at least an order of magnitude. The expulsion of molecular hydrogen by isobutyl or t-butyl does not occur in competition with other unimolecular reactions of these radicals.
Porphyrin Charge-Transfer Complexes with Sym-Trinitrobenzene
Authors: Gouterman Martin , Stevenson Philip E.
Published: January 2005

Absorption spectra of porphyrins in solution with trinitrobenzene indicate formation of a fairly strong one-to-one charge-transfer complex. The ΔF and ΔH values are given for etioporphyrin and tetraphenylporphin; a rough ΔF value was obtained for Zn tetraphenylporphin. It was also found that trinitrobenzene strongly quenches the porphyrin fluorescence.
Isotope Effects and the Mechanism of Atom Production in Gamma-Irradiated Ice at 4.2°K
Authors: Judeikis Henry S. , Flournoy John M. , Siegel Seymour
Published: January 2005

The relative intensities of the electron spin resonance (ESR) spectra of H and D atoms were determined for mixtures of H2O and D2O which were irradiated and observed at 4.2°K. A careful analysis of the results indicates that the yield of atoms per unit irradiation dosage exhibits no isotope effect, except for the system containing trace amounts of H2O in D2O. The presence of a large isotope effect for a system of D2O containing approximately 0.1% H2O is discussed in terms of energy transfer in the solid state.
Mechanical Basis of Diffusion
Authors: Truesdell C.
Published: January 2005

Four types of theory of diffusion are distinguished, presented, and compared: kinematical, hydrodynamical, kinetic, thermodynamic. A simple mechanical theory, based upon recognizing the diffusive drags as forces that produce motions, is shown to include and unify all earlier attempts. In this theory a hypothesis of binary drags is formalized and shown to lead to the symmetry relations proposed originally by Stefan. The Onsager relations for pure diffusion are proved to be equivalent to Stefan's relations. Known results show that these relations hold as a first approximation in the kinetic theory of monatomic gas mixtures. Whether or not they hold in higher approximation is unknown.
Vibrational Spectrum of Digermane
Authors: Crawford Victor A. , Rhee Kee H. , Wilson M. Kent
Published: January 2005

Raman spectra of the liquid and infrared spectra of the gaseous and solid phase have been obtained for Ge2H6 and Ge2D6. With the exception of the torsional mode all fundamental frequencies have been located and assigned to the proper normal modes. The coarse rotational structure of the perpendicular bands, ν7 and ν8, has been resolved and the corresponding Coriolis coupling coefficients determined. Comparisons with the spectra of ethane and disilane have been made.
Microwave Spectrum, Barrier to Internal Rotation, and Quadrupole Coupling Constants of trans-1-Chloropropylene
Authors: Beaudet Robert A.
Published: January 2005

The microwave spectra of two isotopic species of trans-chloropropylene, CH3CH=CHCl35 and CH3CH=CHCl37, have been measured and assigned. The quadrupole coupling constants of the chlorine35 nucleus were determined from the hyperfine structure. A few transitions were further split by the linear effect of the barrier to internal rotation of the methyl group. From these separations the barrier height was measured to be 2170±100 cal/mole.
Longitudinal and Transverse Electron Polarizabilities and Magnetic Susceptibilities of the Aliphatic C–C and C–H Bonds
Authors: Zürcher R. F.
Published: January 2005

The mean electron polarizabilities and the mean magnetic susceptibilities of the aliphatic C–C and C–H bonds, together with their anisotropies, have been combined with the Kirkwood and Gans—Mrowka equations, and this set of equations has been solved for the longitudinal and transverse bond polarizabilities and susceptibilities. The best values for these quantities, obtained by a least-squares treatment, as well as the electric and magnetic anisotropies are discussed and compared with the respective quantities derived theoretically and semiempirically.
Metastable Atoms and the Auroral Afterglow of Nitrogen
Authors: Innes F. R. , Oldenberg O.
Published: January 2005

The auroral afterglow of nitrogen is attributed to N atoms in the high metastable level 6S which in binary collisions with normal N atoms produce excited N2+ ions and with normal N2 molecules excite their spectrum. This hypothesis explains (1) the high energy of the levels emitting light, (2) the dominant instantaneous intensity of the brief duration auroral afterglow, (3) the absence of the N2+ bands in Kaplan's ``blue afterglow,'' and (4) the suppression of the same bands by oxygen impurity.
Symmetry of Helical Polymers. Electronic States of Double-Stranded Polynucleotides
Authors: Rhodes William
Published: January 2005

The symmetry properties of a model double-stranded polynucleotide, containing only one type of monomer unit, have been investigated by the application of the theory of space groups. The rotational parts of the symmetry operations of such a helix form a group which is isomorphic to the point group D10, indicating that there is sufficiently high symmetry to make formal treatment by group theory profitable for applications to the molecular dynamics of related helical polymers. A method of developing the irreducible representations of the space group is discussed and some features of the irreducible representations so obtained are described. Electronic spectral properties related specifically to π, π*, and n, π* states are then discussed within the framework of the group theoretical results, particular emphasis being placed on the nature of the exciton bands produced by excitation resonance interaction among the monomer units, selection rules restricting the mixing of states, selection rules for electric-dipole transitions between the ground state and states of the various exciton bands, and the expected effects of state mixing on the electronic spectral intensities of transitions to π, π*, and n, π* exciton bands.
Approximate Excited Eigenfunctions for Pr3+ and Tm3+
Authors: Rajnak Katheryn
Published: January 2005

Approximate 5d, 6s, 6p, and 5f radial wave functions, which are necessary for any investigation of the effect of configuration interaction in rare-earth spectra, have been obtained for Pr3+ and Tm3+. The calculations were based on the ground-state eigenfunctions obtained by Ridley in an SCF calculation without exchange. 〈r2〉, 〈r4〉, Rk(4f4f, 4f6p), and Rk(4f4f, 4f5f) integrals have been calculated.
Multiply Charged Organic Ions in Mass Spectra
Authors: Meyerson Seymour , Haar R. W. Vander
Published: January 2005

Reports and speculation about multiply charged organic ions in condensed phases have appeared in the recent literature. The occurrence and nature of such ions in the gas phase, as revealed in mass spectra, seem relevant. Triply charged ions have been detected in the spectra of 55 compounds; they are evidently far more common that has been generally recognized. Despite the known susceptibility of doubly charged ions to disruption to two singly charged ions, 10 instances are now known in which a metastable peak furnishes evidence for decomposition of a doubly charged ion to a neutral particle and a different doubly charged ion. Relatively stable structures are possible despite the presence of two or three charges in a molecule.
Electron Spin Resonance of the Thioxanthone S,S-Dioxide Mononegative Ion. Conjugation in Sulfones
Authors: Vincow Gershon
Published: January 2005

The electron spin resonance spectrum of the thioxanthone S,S-dioxide mononegative ion is investigated. Proton hyperfine splittings are reported. Moffitt's treatment of the expansion of the M-shell octet in sulfur is employed in the calculation of spin densities and the occurrence of sulfone conjugation in this radical is confirmed. Unpaired spin densities, calculated using one-electron MO theory with variation of Coulomb and resonance integral parameters, are not in close agreement with experiment. The McLachlan SCF theory with variation of parameters is applied. Negative spin densities are predicted at the 2,4 positions and good agreement with the hyperfine spectrum is obtained for reported ranges of the MO parameters.
Absorption Spectra of Hydrogen-Halide—Rare Gas Mixtures
Authors: Rank D. H. , Rao B. S. , Wiggins T. A.
Published: January 2005

The null-gap regions of the 1–0 bands of HCl and HBr have been investigated with a grating spectrograph of very high resolution. The experiments were performed using an absorption tube of 90 cm length and a hydrogen-halide pressure of 25 cm Hg. The hydrogen halide was pressurized with argon, krypton, or xenon of density 2 to 5 amagats. The sensitivity of the apparatus was such that absorption features 10—4 the intensity of the P(1) line of HCl could be observed with ease.

The absorption features observed are complex, relatively sharp, and totally different when argon, krypton, or xenon is used as the pressurizing gas. It is suggested that the hydrogen-halide molecule forms a molecular complex with the rare-gas atoms used as pressurizing agents. The discrete induced absorption features have an intensity considerably less than 10—3 of the intensity of the P(1) line of HCl per amagat density of pressurizing gas. In HBr the ``induced absorption features'' have approximately two to three times the relative intensity observed in HCl.
Electronic Spectrum of 2,2′-Paracyclophane
Authors: Ron Arza , Schnepp O.
Published: January 2005

The polarized absorption and fluorescence spectra of single crystals of 2,2′-paracyclophane at 20°K were recorded in the region 3300–3100 Å. The spectra consist of narrow lines of which 87 could be measured in absorption and nine in emission. Single crystals having two different planes developed could be prepared sufficiently thin for measurements. The spectra obtained could be divided into two components, one characteristic of a transition moment parallel and the other perpendicular to the unique axis of the tetragonal crystal. These polarization directions are characteristic of molecular directions since in this case no Davydov splitting is to be expected in view of the high symmetry of the crystal. The absorption system is analyzed satisfactorily as representing the forbidden component of the benzene 1A1g→1B2u transition in the ``dimer'' molecule. A totally symmetric progression-forming frequency of 240 cm—1 is assigned as the intermoiety vibration. The appearance of a weak 0–0 transition is interpreted as due to a small-amplitude twist of the moieties relative to one another.
Optical Spectrum of K3IrCl6
Authors: Schroeder Keith A.
Published: January 2005

The complete matrices of the spin-orbit interaction for the d4, d6 configurations are given in a strong cubic field scheme. Intermediate coupling calculations have been carried out for the energy levels of K3IrCl6, and lead to a satisfactory interpretation of the observed optical spectrum.
Lattice Combination Bands in Infrared Spectra of Molecular Solids
Authors: Gordon R. G.
Published: January 2005

It is customary in the discussion of infrared spectra of molecular solids, and of ionic solids containing polyatomic ions, to divide the normal vibrations of the nuclei into two classes: (1) Lattice or external modes, low-frequency vibrations which are approximately motions of whole molecules, and (2) molecular or internal modes, high-frequency vibrations similar to the vibrations of free molecules. The observed spectra are then interpreted in terms of absorption by these fundamentals, and combination bands involving two or more fundamentals. In this paper we discuss combination bands between lattice modes and internal modes. It is shown that a certain amount of information about the intensity of such bands and their temperature dependence can be predicted without a solution to the complete dynamical problem of the lattice vibrations.
Proton NMR Spectra of Disubstituted Benzenes
Authors: Martin J. , Dailey B. P.
Published: January 2005

Precise values of the coupling constants and chemical shifts at infinite dilution in cyclohexane have been determined for an extensive series of related disubstituted benzenes. A method of rigorous analysis of the A2B2 proton spectra of the para-disubstituted benzenes is presented.
HCl-Catalyzed Decomposition of Di-Tertiary Butyl Peroxide in the Gas Phase
Authors: Flowers Michael , Batt Leslie , Benson Sidney W.
Published: January 2005

The homogeneous, gas-phase decomposition of di-tertiary butyl peroxide (dtBP), catalyzed by small amounts (1–16 mole %) of HCl, has been studied in the temperature range 90°—120°C and about 50 mm Hg pressure. Under these conditions, the rate of the uncatalyzed process is negligibly slow. The principal products may be represented by the two stoichiometric equations: dtBP→isobutene oxide+t−BuOH(20%−50%)→isobutene oxide+acetone+CH4(80%−50%).Very small amounts of C3H8, CO, isobutyraldehyde, and C2H6 are also observed. HCl is not consumed. The over-all kinetics may be represented by a simple scheme in which t-BuO and Me radicals abstract H from HCl, and the HCl is regenerated by Cl-atom attack on peroxide. Acetone and isobutene oxide (i-BuOx) act as inhibitors for the Cl-atom chain, yielding the inert CH3COCH2 and Me2CCHO radicals, respectively. The latter is probably responsible for a slow radical isomerization of i-BuOx to the isobutanal. This reaction provides a very fast isomerization path for the conversion of epoxides to aldehydes.

A derived rate law consistent with the data is given by −d(dtBP)dt∼2k1k5(dtBP)2k6(acetone),in which k1 is the rate constant for the splitting of dtBP into two t-BuO radicals, and k5/k6 is the ratio of rate constants for attack of Cl atoms on dtBP or on acetone (and/or i-BuOx), respectively. As predicted, the rate is independent of HCl. The chain length is given by λ=k5(dtBP)/k6(acetone) and is equal to about 25 at 10% decomposition and is almost independent of temperature.

The ratio of yields of acetone to t-BuOH is a direct measure of the kinetics of spontaneous decomposition of the t-BuO radical, and the data show that it is a pressure-dependent process. Unfortunately, the scatter in the data is too great to derive quantitative step constants for the relevant energy-transfer processes.
Carbon Monoxide—Oxygen Atom Reaction
Authors: Mahan Bruce H. , Solo Richard B.
Published: January 2005

The kinetics and light emission of the carbon monoxide—oxygen atom reaction have been investigated. At pressures above 0.2 mm, carbon dioxide is formed by a bimolecular association reaction which appears to violate the electron spin conservation rule. The quantum yield of the reaction is 1/350 at 298°K, and increases with increasing temperature. Evidence has been found that excited carbon dioxide molecules can participate in chain branching processes.
Line Strengths and Widths in Hydrogen Iodide
Authors: Ameer George , Benesch William
Published: January 2005

Measurements on 13 lines in the hydrogen iodide fundamental vibration—rotation band have yielded a set of line strengths of considerable accuracy. From these strengths a total band intensity of 0.37 cm—2 atm—1 at 300°K has been computed, as well as a value for the vibration—rotation interaction parameter θ which is found to be —5. Both of these figures indicate that the ``effective charge'' of this molecule is remarkably small, which fact is reflected in a great dominance of the R branch over the P branch. Using the line strengths as input data, linewidths have been computed from equivalent width measurements. Finally, the linewidths have been converted to optical collision cross sections. The J dependence of the linewidths and the collision cross sections is not typified by the other hydrogen halides. The usual resonance peak is absent and a lower limiting value seems to be reached by | m |=3. Furthermore, the collision cross sections for the lines of higher J are much larger than might be inferred from the other hydrogen halides.
Studies on the Alternant Molecular Orbital Method. IV. Generalization of the Method to States with Different Multiplicities
Authors: Pauncz Ruben
Published: January 2005

A general formulation of the alternant molecular orbital method, applicable to states of different multiplicities in systems with an even number of atoms, is presented. The treatment is formulated in such a way that the same integral sums appear in the energy expression for the states belonging to different multiplicities. The resultant energy expressions show a simple dependence on the mixing parameter λ.

Application to cyclic systems shows that the best λ values decrease slowly with increasing multiplicity. Comparison with the configuration interaction treatment reveals that the AMO method corresponds to a restricted CI treatment, but it is capable of yielding a considerable part of the energy improvement obtained by the latter method.
Formation of F18-Labeled Fluoro-Organic Compounds by the F19(n, 2n) Reaction
Authors: Anbar M. , Neta P.
Published: January 2005

Fluoro-organic compounds were subject to irradiation by fast neutrons produced in a nuclear reactor; fluoroderivatives labeled with F18 were produced and their yield was determined. It was found that labeling yields of fluoro-organic compounds were substantially higher than those of other organic compounds exposed to fluorine 18 produced extramolecularily, either by the O16(H3, n) or by the F19(n, 2n) reactions. The extent of substitution of a hydrogen atom by radiofluorine was found more than 100 times higher than that of a fluorine atom. It was shown that the labeling occurs mainly in the same part of the molecule which carried the original fluorine atom. In some cases it was shown that it is the same atom which is transformed to a radionuclide.

When fluoroorganic compounds were irradiated in solution, a constant molecular labeling yield was observed. This yield which was obtained in dilute solutions in water, acetic acid or ethanol, was found independent of solute concentration; moreover, it was not affected by the presence of scavengers. The labeling yield of the aliphatic solvents was lower when exposed to fluorine 18 produced from an organically bound fluorine than from a fluoride ion.

It is difficult to interpret the experimental results without assuming that a genuine retention of the transformed fluorine 18 in the parent molecule takes place. It is suggested that the (n, 2n) reaction proceeds, in part at least, as a spallation-type reaction, forming an excited F18 nucleus which does not undergo any recoil. The excited F18 is subsequently converted to the ground state following gamma emission; the recoil energy of many of these gammas is not sufficient to cause an irreversible cleavage of the C–F bond.
Empirical Relations of Thermodynamic ``Constants'' to the Activation Parameters of Polymer Relaxations
Authors: Eby R. K.
Published: January 2005

Experimental data are analyzed to show that for some polymer relaxations observed in dynamic mechanical experiments, the activation enthalpy and entropy appear to follow a series of empirical relations. These relations, which also apply to inorganic solids, indicate that melting temperature, thermal volume expansion coefficient, glass transition temperature, and the relaxations are interrelated in polymers. Also, the modulus and internal friction of polypropylene and polyoxymethylene are reported. Measurements made between —65° and 165°C with longitudinal waves at a frequency of 12 Mc show relaxations to occur at 60°C in polypropylene and at 0° and 145°C in polyoxymethylene.
Solvent Effects in Electron Spin Resonance Spectra
Authors: Gendell Julien , Freed Jack H. , Fraenkel George K.
Published: January 2005

It has been shown that a simple model can account for the available data on the solvent dependence of the hyperfine splittings in the ESR spectra of organic free radicals. We have assumed that the changes in splittings arise entirely from a redistribution of the pi-electron spin density, and that the spin density is affected only by localized complexes between the solvent and polar substituents or heteroatoms in the radical. This model predicts that the magnitudes of the changes in proton splittings should often be small, although large fractional changes at positions of small spin density can sometimes occur. The large variations found for the nuclei of many electron atoms are shown to arise because their splittings are very critical functions of the spin density.

The effect of the solvent on the proton hyperfine splittings in the semiquinones has been treated by assuming that the solvent alters the electronegativity of the oxygen atoms and by performing molecular-orbital calculations to estimate spin density changes. These calculations reproduce both the directions and magnitudes of the changes in proton splittings with solvent and are in agreement with the very large fractional changes observed at some positions with small splittings.

An analysis of the effects on the ESR spectra of the exchange reactions between the different solvent complexes has shown that the spectra normally observed result from systems undergoing rapid exchange. A simple model for a radical with only one functional group which can interact with the solvent (e.g., the nitrobenzene anion), is shown to account very well for the observed variations in hyperfine splittings as a function of the composition of a binary solvent mixture. The treatment of the exchange reactions by use of the modified Bloch equations is compared with the spectral density method. The contribution to the linewidth from solvent-induced fluctuations in the spin-density distribution is calculated for a simple two-jump case, and other factors affecting the linewidths of radicals subjected to random solvent interactions are discussed.
Thermogravitational Thermal Diffusion in Liquids. I. The Formal Theory
Authors: Horne Frederick H. , Bearman Richard J.
Published: January 2005

The formal theory of the steady state of thermogravitational thermal diffusion in binary liquid mixtures is developed with the object of using a thermogravitational column of small annular separation to determine thermal diffusion factors quantitatively. Although the general approach of Furry, Jones, and Onsager is followed, full use of all hydrodynamic and thermodynamic transport equations permits the explicit statement and the subsequent re-examination of the simplifying approximations. The resulting differential and integral equations, which are expressed in cylindrical coordinates, are solved subject to boundary conditions imposed by the vanishing of all velocities at the apparatus walls. Inclusion of the temperature and composition dependences of the thermodynamic properties (density, viscosity, etc.) of the fluid leads to the appearance in the final equations of a term which quantitatively takes account of the ``forgotten effect'' as well as of ordinarily negligible correction terms. The final working equation is valid for the arithmetic mean experimental temperature and the initial uniform composition of the mixture. It is shown that an easily measured composition difference can be substituted for the steady-state vertical composition gradient.
Thermogravitational Thermal Diffusion in Liquids. II. Experimental Thermal Diffusion Factors for Carbon Tetrachloride—Cyclohexane at 25°C
Authors: Horne Frederick H. , Bearman Richard J.
Published: January 2005

An experimental investigation of thermogravitational thermal diffusion in carbon tetrachloride—cyclohexane at 25° is described, and thermal diffusion factors for this system are calculated on the basis of the formal theory derived in the preceding paper. The procedure for determining the required compositions involves a special weighing technique and Rayleigh interference refractometry. A new method for using the latter is presented. The design, construction, and use of a cyclindrical thermogravitational apparatus are discussed. Small numerical corrections are made for the production and thermal diffusion of impurities, one of which is apparently cyclohexylhydroperoxide. Calculated thermal diffusion factors agree well for most compositions with results of pure thermal diffusion measurements.
Molecular Constants of Chlorodifluoromethane from Microwave Spectrum Analysis
Authors: Beeson Edward L. , Weatherly T. L. , Williams Quitman
Published: January 2005

The microwave spectrum of CHClF2 has been studied in the region 14 to 38 kMc and an analysis made for six transitions of each isotopic species. The following molecular constants were obtained: Rotational constants (Mc/sec)CHCl35F2CHCl37F2A10 234.6410 233.80B4861.244717.14C3507.313431.88Asymmetry parameterκ−0.597482−0.622091Quadrupole coupling constants (Mc/sec)χaa−64.96−51.07χbb35.6127.92χcc29.3523.15The C–H distance was assumed to be 1.09 Å, and the following structural parameters were computed: d(C–Cl)=1.74 Å, d(C–F)=1.35 Å, 〈HCCl=107°, 〈ClCF=110°30′, and 〈FCF=107°.
Monte Carlo Calculations on the Cell-Cluster Theory of Fluids
Authors: Weissmann Mariana , Mazo Robert M.
Published: January 2005

Double-cell integrals of the cell-cluster theory have been evaluated by Monte Carlo numerical integration for hard spheres, and for molecules interacting with a Lennard-Jones potential at three temperatures. The volumes studied are rather higher than normal liquid volumes, the lowest being V*=2. Under these conditions, cell-cluster theory based on only single- and double-cell contributions gives poorer agreement with experiment than single-cell theory. The question of whether these conclusions extend to the region of normal liquid densities is unanswered at present.
Single-Crystal X-Ray Diffraction Study of β Nitrogen
Authors: Streib William E. , Jordan Truman H. , Lipscomb William N.
Published: January 2005

Three-dimensional x-ray diffraction data have been collected from single crystals of nitrogen at 50°K. The observed general condition, l=2n for hh2h̄l reflections is in agreement with the previously assigned space group, P63/mmc, and there are two molecules in the unit cell. The data agree equally well with two nearly physically indistinguishable models, in each of which the molecular centers form a hexagonal closest packed (hcp) lattice. In one, the molecule is precessing about the z axis passing through its center, at an angle of 54.5±2.5° between z and the N–N bond, while in the other the nitrogen atoms are statistically distributed among the 24-fold positions with the molecular axis again at an angle of 54.5° relative to z.
Natural Expansion of Exact Wavefunctions. II. The Hydrogen-Molecule Ground State
Authors: Davidson Ernest R. , Jones Leon L.
Published: January 2005

The Kolos and Roothaan wavefunction for H2 has been analyzed into natural orbitals. It was found that the first natural orbital is nearly the SCF function. The first four natural orbitals provide a good description of the molecule and give a total energy of —1.169884 hartrees. Beyond the first four terms, the natural expansion becomes more slowly convergent.