bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR of Isotopically Substituted Molecules. A Complete Analysis of the Spectrum of Acrylonitrile
Authors: Freeman R.
Published: January 2005

The nuclear magnetic resonance spectra of 13CH2:CHCN and CH2:13CHCN appearing in their natural abundance in acrylonitrile have many proton transitions obscured by the much stronger proton resonances of CH2:CHCN. Double-irradiation experiments have been used to locate these missing lines and the 13C transitions, and to assign them to the appropriate energy level diagrams. This has made possible three parallel independent analyses by the iterative procedure, the identical proton—proton coupling constants providing a searching test of the validity of the solutions. The relative signs and magnitudes of the 13CCH coupling constants have been determined, and small but significant shifts observed in the proton resonances, attributable to 13C isotope effects. The chemical shifts of the 13C nuclei have been related to the resonance frequency of protons in tetramethylsilane in the same magnetic field, with an accuracy of ±1 in 108.
Heat Content of Molten Uranium
Authors: Levinson L. S.
Published: January 2005

The heat contents of γ-phase uranium from 1205° to 1394°K and of molten uranium from 1415° to 1579°K were measured using a drop calorimeter.
Proton-Transfer Reactions between H3+ and Saturated Hydrocarbons
Authors: Ausloos P. , Lias S. G.
Published: January 2005

The γ-ray radiolysis of H2 has been investigated in the presence of relatively small concentrations of C2D6, C3D8, iso-C4H10, (CH3)3CD, (CD3)4C and n-C5D12. It is shown that, in all cases, the proton-transfer reaction H3++RD→RDH++H1, occurs even when the additive is only 0.01% of the hydrogen. The protonated hydrocarbon decomposes mainly to form a carbonium ion and a neutral alkane molecule. From the radiolysis of D2—CH4—C3D8 mixtures, it could be deduced that CH4D+ is produced, which subsequently transfers a proton or deuteron to C3D8. It is suggested that the study of the radiolysis of H2, in the presence of additives offers the possibility of producing well-specified ions, the reactions of which can be followed in the absence of interfering processes.
Spectrum of Er3+ in Single Crystals of Y2O3
Authors: Kisliuk P. , Krupke W. F. , Gruber J. B.
Published: January 2005

The spectrum of Er3+ in single crystals of Y2O3 has been examined from 0.225 to 2.4 μ in absorption and fluorescence, and energy levels have been assigned. The Slater integrals and spin—orbit coupling parameter have been determined, which give the best over-all agreement between the centers of gravity of the observed groups of levels and the 4f11 SLJ energy levels of the ``free'' Er3+ ion; they are F2=429.583 cm—1, F4=65.012 cm—1, F6=7.136 cm—1, ζ=—2383.17 cm—1. Of the two inequivalent cation sites, C2 and C3i, one can with consistency demonstrate that the site without inversion symmetry (C2) gives rise to the entire observed spectrum.
On the Calculation of the Molecular Friction Constant
Authors: Gray Peter , Rice Stuart A.
Published: January 2005

The use of isotope-separation data to obtain experimental values for the mean-square force acting on a molecule in a liquid and the implications of this data for the theory of self-diffusion are discussed.
On the Kinetic Theory of Dense Fluids. XVII. The Shear Viscosity
Authors: Lowry Bright A. , Rice Stuart A. , Gray Peter
Published: January 2005

In this paper we report a theoretical study of the shear viscosity of dense fluids along with some measurements of the viscosity of liquid Ar. It is found that the theory of Rice and Allnatt leads to predictions of the temperature dependence of the shear viscosity under conditions of constant volume in good agreement with experiment. Also, the magnitudes of the predicted shear viscosity agree very well at T=128°K, p=50 atm (ηcalc=0.727×10—3 P, ηobs=0.835×10—3 P) and moderately well at T=90°K, p=1.3 atm (ηcalc=1.74×10—3 P, ηobs=2.39×10—3 P). The importance of obtaining accurate intermolecular pair potentials and pair correlation functions is discussed briefly.
Charge-Transfer Absorption Spectra of NO in Kr and CH3OH Solutions
Authors: Ferguson Eldon E. , Broida H. P.
Published: January 2005

It is proposed that a broad, structureless absorption previously observed near 2400 Å in the spectrum of NO in condensed krypton is due to charge transfer, probably of the type known as ``contact charge transfer.'' On the basis of energetic considerations, NO should act as the donor in this case. A similar absorption observed in NO dissolved in methanol solution is probably due to the same phenomenon with NO being the donor, and not the acceptor as previously suggested.
Separation of Boron Isotopes. VI. Ethyl Ether, Ethyl Sulfide, and Triethylamine-BF3 Systems
Authors: Palko A. A. , Drury J. S.
Published: January 2005

The BF3 complexes of ethyl ether, ethyl sulfide, and triethylamine were studied. Isotopic equilibrium constants for the reactions B10F3(g)+B11F3·donor(l)⇌B10F3(g)+B10F3·donor(l) were measured at several temperatures for each of the three systems. Vapor pressures of the ethyl sulfide complex, and rates of exchange of boron between BF3 and BF3·Et3N were also determined.
Magnetic Susceptibilities of Several Paramagnetic Salts at Liquid He3 Temperatures
Authors: Schriempf J. T. , Friedberg S. A.
Published: January 2005

A cryostat is described in which magnetic susceptibility measurements may be made by an audio-frequency mutual induction technique at temperatures down to 0.35°K. Below 2°K the specimens are in direct contact with liquid He3. Results of measurements on several compounds are presented. The powder susceptibility of [Cr3(CH3COO)6(OH)2]Cl·8H2O has been found to obey a Curie—Weiss law. Both powdered Co(CH3COO)2·4H2O and powdered Ni(CH3COO)2·4H2O are observed to be paramagnetic to the lowest temperatures attained; the former salt does not exhibit the anomaly at 0.6°K found in earlier studies employing a magnetic cooling technique. The powder susceptibility of Mn(HCOO)2·2H2O suggests the existence of significant coupling among many of the Mn++ moments, but no evidence was found of a cooperative transition above 0.56°K.
Spectral and Magnetic Properties of Some Dithioloxalato Complexes
Authors: Carlin R. L. , Canziani F.
Published: January 2005

The electronic spectra of the tris- (dithioloxalato) complexes of Cr III and Co III are reported and interpreted in terms of the simple crystal field picture. The magnetic susceptibility of the analogous Fe III compound is reported as a function of temperature, and interpreted by means of the theory of Figgis; this leads to an estimate of the parameters describing the covalency and axial field in the compound. Dithioloxalate is not a strong ligand, in the spectrochemical sense, but it does lead to an exceptional lowering of the electron—electron repulsions of the central metal ion.
Many-Parameter Alternant Molecular Orbital Calculations for Large Cyclic Systems with Closed-Shell Structure
Authors: Swalen J. D. , de Heer J.
Published: January 2005

Computer calculations of the energies for various ring systems with closed-shell structure have been carried out within the framework of the many-parameter alternant molecular orbital method. A significant improvement is obtained over the corresponding single-parameter results. Since the explicit energy minimizations are rather time consuming, some semiempirical relations between the relevant parameters are also discussed.
Vibrational Symmetry and Selection Rules for an Ethane-Type Molecule
Authors: Kirtman Bernard
Published: January 2005

The vibrational symmetry and selection rules for an ethane-type molecule are re-examined. It is demonstrated that the kinetic and potential energy matrices can be fully reduced under either D3h or D3d. However, the dipole moment and polarizability tensors do not, in general, show quite as much symmetry, so that certain infrared and Raman coincidences, forbidden by D3d selection rules, become allowed.
Morse Oscillator Matrix Elements for HI Vibration—Rotation Lines
Authors: Benesch William
Published: January 2005

The treatment developed by Herman and Rubin for the calculation of the vibration—rotation matrix elements of the individual lines of a Morse oscillator whose electric dipole-moment function is expressed as a power series has been put into a form suitable for electronic computation. Calculations have been carried out for all of the hydrogen halides, and the results for hydrogen iodide are reported here in detail. Comparison with matrix elements obtained from experimental infrared line intensities indicates that the dipole-moment function coefficients for HI (taking M0=0.42 D) are M1= —0.51×10—11 esu and M2=0.16×10—2 esu/cm. The value for M2 is based primarily on the data of the overtone band from which an accurate determination of M2 is made possible by the accidental weakness of the M1 contribution. The J dependence of the matrix elements provided by the present calculation is qualitatively correct but not sufficiently strong to follow the trend of the data into the wings of the band. The neglect of higher-order terms in the expansion of the centrifugal stretching term is presumably responsible for this sluggish behavior of the calculated matrix elements at high values of J.
Distribution and Relaxation of Vibrationally Excited Oxygen in Flash Photolysis of Ozone
Authors: Fitzsimmons Robert V. , Bair Edward J.
Published: January 2005

Absolute absorption by a sequence of bands in the Schumann—Runge series arising from oxygen molecules in vibrationally excited levels of the ground state formed by secondary processes of the flash photolysis of ozone was measured as a function of time. Measurements of bands arising from states v″ = 13 through v″ = 19 are analyzed in terms of a continuously generated initial distribution which relaxes to room temperature in single quantum steps.

The vibrational relaxation rate constants are large and are interpreted as an efficient transfer of vibrational energy between ozone and excited oxygen. The relaxation process is consistent with a single quantum step model, and if deviations from this model are real, they are secondary. Vibrationally excited oxygen is formed initially in all of the observed states. The analysis does not give the shape of the initial distribution, but in magnitude it is consistent with a normal distribution of the energy of the reaction in all of the available modes of motion. The absolute concentration of excited oxygen in vibrational states 17 and higher is relatively too small for these molecules to have a major role in the chemistry of ozone photolysis.
Density Matrix Description of Nuclear Magnetic Double Resonance
Authors: Baldeschwieler John D.
Published: January 2005

Bloch has given a general density matrix description of the nuclear magnetic double-resonance problem. However, this formalism has not been widely applied to problems of chemical interest because of the generally intractable form of the equations and notation that arise for even the simplest spin systems. The use of the Redfield equation introduces significant simplifications into the treatment so that the density matrix description can be given in a form that is convenient for digital computation. An example of the density matrix description of the double-resonance spectrum of a single nucleus of spin ½ is given in detail, and compared with frequency-sweep double-resonance spectra observed for the proton in CCl3H.
Viscosity of Molten Branched Polymers and Their Concentrated Solutions
Authors: Bueche F.
Published: January 2005

The viscosity of molten polymers and their concentrated solutions is investigated theoretically. Both linear and branched polymers are considered. Two methods are used, one being merely an extension of a previous computation for linear polymers. Essential agreement is found between the results of the two methods. It is found that the viscosity of a branched polymer ηb is related to the viscosity of a similar linear polymer of identical molecular weight by the equation ηb/ηl=g7/2 if the chains are highly entangled. For nonentangled chains the ratio is merely equal to g. The quantity g is the square of the ratio of the radius of gyration of the branched molecule to that of the linear molecule.
Linear Ising Models and the Antiferromagnetic Behavior of Certain Crystalline Organic Free Radicals
Authors: Edelstein A. S.
Published: January 2005

Linear Ising models including molecular fields and impurities are employed to interpret the susceptibility and specific heat data of picryl amino carbazyl (PAC), 1,3-bisdiphenylene 2-phenyl allyl (BDPA), and Wurster's blue perchlorate (WB). Data taken below 1°K on the linewidth and susceptibility of diphenyl picryl hydrazyl (DPPH) and BDPA is presented. A possible criterion is suggested for distinguishing whether impurities or dislocations are responsible for a low-temperature susceptibility rise in an antiferromagnetic system. Expressions determining the long-range order and the correlations between the spins are found.
Hole Mobility in Organic Molecular Crystals
Authors: Raman R. , McGlynn S. P.
Published: January 2005

Adoption of a simple crystal counter technique has made possible a study of carrier mobilities in organic molecular crystals. The results give a mean value of 0.48 cm2/V·sec for the mobility of holes in anthracene in the low-field region. The data indicate that study of pulse rise times at high electric field strengths will provide information on charge-carrier scattering mechanisms in these materials.
Nuclear Magnetic Resonance Study of Interlayer Water in Hydrated Layer Silicates
Authors: Graham J. , Walker G. F. , West G. W.
Published: January 2005

Resonance data have been obtained for the intracrystalline water in homo-ionic vermiculite, montmorillonite, and hectorite in both the crystalline and osmotic swelling regions, but interpretation is complicated by the anisotropic susceptibility of the crystals and the effects of particle size, discussed briefly in an appendix. Because of this, only a minimum value can be obtained for the proton mobility, and it is shown that in the osmotic swelling region molecular motion may not be very different from that in free water. The proton mobility in the crystalline swelling region varies with the water content. A single-crystal study of vermiculite containing two sheets of water between silicate layers shows that the water molecules are in hindered rotational movement. A transition to a freely reorienting phase is dependent on particle size. The results are applied to some aspects of the theory of gels and of interparticle forces.
Linewidth of the Exciton Absorption in Naphthalene Crystals
Authors: Maria H. J.
Published: January 2005

The crystal spectrum of naphthalene near 3200 Å is studied in the temperature range 4° to 80°K. The intensity and half-linewidth of the a band of the first purely electronic transition are found to be strongly dependent upon temperature and proportional to the density of phonons with energy of 14 cm—1. The b band shows very little temperature dependence. It is concluded from the line shape and linewidth of the a band that mobile excitons are possible in naphthalene.
Resonant and Near-Resonant Vibrational—Vibrational Energy Transfer between Molecules in Collisions
Authors: Rapp Donald , Englander-Golden P.
Published: January 2005

A semiclassical calculation of the probabilities of resonant and near-resonant vibrational energy interchange in molecular collisions is accomplished by means of a collision model similar to that used in vibrational—translational energy transfer. The results indicate that transition probabilities are of the order of ½ in resonant and near-resonant processes at room temperature.
Influence of Vibration—Rotation Interaction on the Rotational ``Temperature'' Determined from an Electronic OH Transition
Authors: Zinman Walter G. , Bogdan Stanley I.
Published: January 2005

The R2 (1, 0) and R2 (0, 0) bands of the 2Σ+—2Π electronic band of OH have been used both in emission and absorption to determine the rotational ``temperature'' of various hydrogen flames. The temperatures obtained using the Learner correction are self-consistent, while the temperatures obtained using the James correction are not. The temperatures obtained from absorption spectra using the Learner correction were in good agreement with the sodium-line reversal temperature. For a hydrogen—oxygen flame at 1 atm the temperature in emission was significantly higher than the temperature in absorption.
Time-Dependent Perturbation-Variation Method. II
Authors: Yaris Robert
Published: January 2005

It is shown that the time-dependent perturbation-variation method recently developed by the author and that previously developed by Karplus and Kolker are equivalent.
Electron Spin Resonance of the Acetophenone and Benzaldehyde Anion Radicals
Authors: Steinberger Naomi , Fraenkel George K.
Published: January 2005

The electron spin resonance spectra of radicals obtained from acetophenone, benzaldehyde, and 4-fluoroacetophenone were found in a previous investigation to be inconsistent with those of other carbonyl-anion radicals. These compounds have been reinvestigated using new techniques for the electrolytic generation of the radicals. For the first two substances, unstable radicals were detected with spectra that were different from those previously obtained. The new spectra are completely consistent with the results for the other related radicals, and also show that the carbonyl groups are locked into the plane of the aromatic ring. The nature of the radicals investigated previously has not been ascertained. A new spectrum was not obtained for the 4-fluoroacetophenone radical under the new conditions employed for the other two radicals presumably because this species is too unstable. A preliminary interpretation has been given to linewidth variations found in the spectra.
Intensity of the Forbidden X Π322 — X 2Π½ Satellite Bands in the Infrared Spectrum of Nitric Oxide
Authors: James Thomas C.
Published: January 2005

Satellite lines in the spectrum of nitric oxide which correspond to transitions Π322, v=1, J′←2Π½, v=0, J were observed. Intensity measurements show that these lines are of the order of 10—4 times less intense than the fundamental and have intensities which agree with theoretical predictions. From line-frequency measurements the multiplet splitting parameter is obtained for both the v=0 and v=1 vibrational levels. The values obtained are A0=123.1 cm—1 and A1=122.9 cm—1. The intensity of the fundamental is found to be 138 cm—2/atm at 273°K, which corresponds to a dipole moment derivative of 2.32 D/Å.
Triplet—Singlet Luminescence from Methylated Benzenes in the Crystalline State and in Rigid Glass Solutions
Authors: Sponer H. , Kanda Yoshiya
Published: January 2005

In continuation of earlier studies, triplet—singlet emission of the following methylated benzenes is reported in their solid phases: mesitylene, durene, hexamethylbenzene. The spectra were obtained in rigid EPA solutions at 77°K, and in the crystalline state at 77° and at 4°K. Two different spectra were found for mesitylene and durene crystals, one at shorter wavelengths representing the genuine triplet—singlet emission of the substance, and the other at longer wavelengths belonging to the lowest phosphorescence of an oxidation product. Hexamethylbenzene crystal apparently exhibits only one spectrum at any temperature. No solution spectrum was obtained for it because of its poor solubility. For an interpretation of the observations, various processes which take place in these crystals upon light illumination are discussed.
Crystal Structure of Cu2Cl4(CH3CN)2, Cu3Cl6(CH3CN)2, and Cu5Cl10(C3H7OH)2
Authors: Willett Roger D. , Rundle R. E.
Published: January 2005

The crystal structures of three red complexes of copper (II) chloride with the molecular formulas Cu2Cl4(CH3CN)2, Cu3Cl6(CH3CN)2, and Cu5Cl10 (C3H7OH)2 have been determined. Each compound contains discrete molecules in which the copper atoms and their ligands lie essentially in a plane. Within each molecule, adjacent copper atoms are bridged by two chlorine atoms equidistant from the copper atoms. Each copper atom forms four bonds, with Cu–Cl≃2.3 Å while Cu–O or Cu–N bonds are just less than 2.0 Å. Bond angles are approximately 90°. In all cases the organic molecules are bonded to copper atoms in positions which are trans for the entire molecule. Molecules are bridged together by longer Cu–Cl bonds which vary from 2.6 to 3.2 Å.
Molecular and Crystal Structure of B20H16
Authors: Dobrott Robert D. , Friedman Lawrence B. , Lipscomb William N.
Published: January 2005

A single-crystal three-dimensional x-ray diffraction study has established the chemical composition and molecular structure of B20H16, which has D2d symmetry. Two B10H14 cages are joined together at the open faces, with the loss of all bridge H atoms, and loss of terminal H atoms on the four B atoms which join these cages. There are eight molecules in the tetragonal unit cell which has dimensions of a=9.650 and c=29.64 Å. The space group is I41/acd, and the molecules occupy sites of symmetry S4.
Effect of Cl— and SO42— on the Paramagnetic Resonance Linewidth of Mn2+ in Aqueous Solution and the Rates of Formation of the Complex Ions
Authors: Hayes Robert G. , Myers Rollie J.
Published: January 2005

The linewidth of one of the hyperfine components in solutions of Mn(ClO4)2 containing added NaCl and Na2SO4 was studied from 20°—200°C at 9000 Mc/sec. The chloride ion contributes little broadening at 0.1M below 80°C but considerable broadening is obtained above this temperature. The sulfate contributes broadening at all temperatures. The rates of formation of ``inner-sphere'' and ``outer-sphere'' complexes are discussed together with their rates of relaxation. At the lower temperatures the ``outer-sphere'' complexes primarily contribute to the broadening while at the higher temperatures the ``inner-sphere'' complexes also contribute. From the broadening above 80°C the rate of formation of the ``inner-sphere'' complexes are evaluated.
Lyman Alpha Lamps and Reaction of Deuterium Atoms in the 2P State with Molecular Nitrogen
Authors: Koyano Inosuke , Tanaka Ikuzo
Published: January 2005

Characteristics of hydrogen- and deuterium-Lyman alpha, emitted from their respective electrodic discharge lamps, were investigated, and the optimum conditions were determined for the production of resonance lines of sufficient intensity and sharpness for producing H(2P) or D(2P) atoms by irradiation of the ground-state atoms. Reactions between H(2P) or D(2P) atoms and molecular nitrogen were also studied by irradiating the mixtures H+N2 or D+N2 with H Lyman alpha or D Lyman alpha, and the following results were obtained: H+N2+H Lyman alpha→NH3,H+N2+D Lyman alpha→no product,D+N2+H Lyman alpha→no product,D+N2+D Lyman alpha→ND3.Moreover, the relation between the amount of the product and the rate of 2P atom formation was examined, and it was found that the former is strongly affected by the latter.
Statistical Thermodynamics of the Lattice Model of a Polymer Molecule
Authors: Mazur Jacob
Published: January 2005

Introduction of a potential energy of interaction between nonbonded neighbors of a lattice-simulated random-walk polymer enables us to study the thermodynamic properties of such a polymer. When the potential energy over a given range of intramolecular separations becomes infinitely large, the free energy and the entropy per unit step can be computed directly either from the attrition data using the Monte Carlo method of generating random walks, or from the exact numerical calculations for short chains. The transition to rodlike molecular configurations and the accompanying change in the free energy per unit step can be followed by gradually extending the range of the infinitely large intersegment interactions.

Instead of using computational methods for estimating the free energy of a polymer with a hard-core potential energy, one can approximate the free energy by limiting the intramolecular interactions to the nearest neighbors only. These interactions are limited to configurations separated by the smallest number of steps needed to bring two polymer segments within a specified range of a hard-core potential energy. The free energy can be calculated analytically, using certain recurrence relations constructed for the number of permissible configurations. A comparison is made of the results obtained on the basis of nearest-neighbor approximation to the more accurate data obtained from the numerical calculations.
Kinetics of Pyrolysis of Alkyl Hydroperoxides and Their O–O Bond Dissociation Energies
Authors: Benson Sidney W.
Published: January 2005

It is shown that group additivity rules lead to very reliable estimates (±1 kcal) for the ΔHf° of both alkyl peroxides and hydroperoxides. Previously published data for t-BuO2H are unique in showing a discrepancy of 6.3 kcal/mole from the estimated data. From the ΔHf° for the ROOH and the activation energies of pyrolysis of ROOR it is shown that the bond dissociation energies D(RO–OH) are about 42 kcal/mole for alkyl R. On this basis the direct split ROOH→RO+OH is shown to contribute negligibly to the observed kinetics of decomposition of t-BuOOH in solution. Instead the decomposition is shown to be compatible with a chain involving t-BuO2 and t-BuO radicals via the fairly well established reaction: 2 t-BuO2→2 t-BuO+O2.

The rate law for such a chain is shown to lead to 43 power dependence on t-BuO2H in good accord with the kinetic data. Absolute values of the chain rate are also in good accord with the data. It is further shown that very reactive solvents (olefins, etc.) may convert RO2 to RO directly, changing the rate to 32 order with a lower activation energy (∼28 kcal). Published data from studies of tetralin-OOH and cyclohexane-OOH are shown to be in good accord with the proposed mechanism.

Allylic hydroperoxides are discussed briefly and considered from the standpoint of good H-atom donors. The styrene induced decomposition of cyclohexane-OOH is considered in detail and a new, fast initiation step is discussed: 2φCH=CH2+ROOH→φĊH–CH2–CH2–CH2φ+RO2·.
Statistical Theory of the Hydrogen Molecule-Ion
Authors: Golden Sidney , Chernin Judith G.
Published: January 2005

A version of statistical theory is applied to the hydrogen molecule-ion, with good results for the electronic energies of the lowest attractive and repulsive states. For the former, a binding energy of 0.085 a.u. is obtained with an internuclear distance of 2.10 a.u., to be compared with 0.103 and 2.00 a.u. obtained from the exact solution of Schrödinger's equation. The method employed involves the use of hydrogen atomic orbitals, although when the latter refer to unbound states they are approximated by plane waves.
Reaction of Electronically Excited O2 with CO
Authors: Raper O. F. , DeMore W. B.
Published: January 2005

Photolysis of solutions of O2 in CO at 77°K with 2537-Å radiation has been found to produce O3 and CO2. Absorption of radiation in this wavelength region by O2 corresponds to the forbidden transition 3Σu+←3Σg—, the Herzberg bands of O2. Since O2 but not CO absorbs 2537-Å radiation and since O2 cannot dissociate directly, the reaction must occur between excited O2 and CO. The quantum yield for O3 formation in the limit of low O2 concentration is of the order of 0.33 and increases slightly with increasing O2. In the concentration range studied CO2 is formed somewhat faster than O3. These results suggest that an intermediate is involved in the reaction which is capable of direct reaction with CO and O2 to form products. This intermediate is proposed to be CO3*, and a mechanism involving this species is postulated.
Nuclear Magnetic Resonance Study of the Solvation of Ni++ in Methanol and Methanol—Water Mixtures
Authors: Luz Z. , Meiboom S.
Published: January 2005

Proton magnetic resonance spectra of solutions of Ni(ClO4)2 in acidified methanol and in methanol—water mixtures are reported. Separate peaks for the bulk methanol and for the methanol bonded to Ni++ are observed. From the temperature dependence of the peak frequencies a hyperfine interaction constant between the Ni++ and the methyl protons of the bonded methanol of +7.9×105 cps was obtained. At low temperatures, the linewidth is determined predominantly by electron—proton dipole—dipole interaction. The relevant correlation time is the electron relaxation time, which is about 3×10—12sec. This time decreases with increasing temperature, with an apparent activation energy of 1.3 kcal mole—1. At the higher temperatures methanol exchange contributes to the linewidth. The addition of water to the solvent increases the rate of exchange. This is ascribed to the formation of mixed water—methanol complexes.
Mechanism of the Photolysis of Ethane at 1470 Å
Authors: Hampson R. F. , McNesby J. R. , Akimoto H. , Tanaka I.
Published: January 2005

A complete analysis of the products of the photolysis of ethane at 1470 Å has been carried out. Isotopic analyses of products of the photolysis of C2H6+C2D6 and of CH3CD3 have led to the following conclusions.

(1) It is possible to explain the data on the basis that nearly all molecular hydrogen produced in the primary process comes from the end carbon atom. CH3CD3→H2+CHDCD2*,CH3CD3→D2+CH2CHD*.The HD can be accounted for by the decomposition of excited CHDCD2* and CH2CHD*. CH2CHD*→HD+CHCH,CD2CHD*→HD+CDCD.(2) Other primary processes are CH3CD3→CH3+CD3,CH3CD3→H+D+CH2CD2.The importance of the latter, relative to the molecular elimination, is about 15:85.

(3) Propane and butane arise from ethyl radicals formed by addition of H and D atoms to ethylene.

(4) The excited state of ethane has a lifetime smaller than 10—9 sec.
Infrared Absorption Spectra of LiOH Films in the 75- to 650-cm—1 Region
Authors: Buchanan R. A. , Caspers H. H. , Marlin H. R.
Published: January 2005

The infrared absorption spectrum in the 75- to 650-cm—1 region of an evaporated LiOH film is presented. In addition, the spectra from 225 to 650 cm—1 of LiOD and mixed LiOH, LiOD evaporated films are also presented. From this data it is possible to make wavenumber assignments for the 2Eu and 1A2u infrared active fundamental modes. The spectrum of the mixed LiOH, LiOD film demonstrates that coupling exists between motions of the OH— ions in the LiOH lattice. These results are in agreement with the lattice vibration model proposed for explaining the combination bands observed in the near infrared absorption spectrum.
Phase Transitions in Ammonium Fluoride
Authors: Swenson C. A. , Tedeschi J. R.
Published: January 2005

The temperature and pressure dependence of the transitions to two high-pressure modifications of NH4F, one of which is reported for the first time, have been studied. By analogy with NH4I, it would appear that these transitions occur at room temperature from the normal wurtzite structure to an fcc (NaCl) structure at 3.8 kilobars to a bcc (CsCl) structure at 11 kilobars. The respective volume changes, roughly 28 and 11% of the zero pressure molar volume, can be understood quantitatively in terms of a simple hard-sphere ionic picture with reasonable values for the ionic radii. Molar volumes and compressibilities have been obtained for these phases, as well as the transition parameters over a range of temperatures from 200° to 400°K.
Nuclear Spin—Spin Coupling Involving Heavy Nuclei. The Coupling of Tl205 and Tl203 with H1 Nuclei in (CH3)2TlX and (CH3CH2)2TlX Compounds
Authors: Hatton J. V.
Published: January 2005

The nature of the spin-coupling interaction between thallium nuclei and protons in (CH3)2TlX and (CH3CH2)2TlX compounds has been examined. In aqueous solution where the corresponding cations R2Tl+ are present, the coupling constants are characteristic of the alkyl group attached to thallium. In pyridine solution the coupling constants are dependent upon the nature of X and are larger than those in the parent cation. Using a simplified model for contact interaction employing optical hyperfine splitting constants, an estimate of the contact contribution to the total thallium—proton coupling constant has been made for the series R3Tl, R2Tl+, and RTl++. It is found that irrespective of the nature of R the observed proton—thallium coupling constants increase from left to right in the relative proportions predicted by the model. The results are consistent with the conclusion that the thallium and hydrogen nuclei are coupled mainly through the Fermi contact interaction.
Role of Multiple Quantum Transitions in NMR: A Three-Spin System
Authors: Musher J. I.
Published: January 2005

The double and triple quantum (DQ and TQ) transitions in molecules containing three weakly coupled nuclei of spin ½ are examined theoretically and experimentally. Owing to the rapid growth and saturation of these transitions with increasing rf, it is practicable to observe each individual resonance only within a limited rf range. Based on the theory of Yatsiv, expressions at a given T1=T2 are computed for the rf fields at which the various MQ absorption signals will attain their maxima and the intensity of these absorptions relative to the maximum intensity for SQ signals. It is pointed out that the usual MQ signal measured in liquids has a linewidth almost equal to that of a SQ signal, since a considerable saturation of the former is necessary for its easy observation. A frequency shift only significant for high-rf MQ signals is also computed. The DQ spectrum of a camphor derivative containing three weakly coupled protons is examined and the experimental results for the observable peaks agree rather well with the theory. The geminal J is opposite in sign to the vicinal J's.
Theoretical Calculation of Electron Collision Cross Sections for the 1 1S→2 1P Transition in Helium
Authors: Lassettre Edwin N. , Jones Ernest A.
Published: January 2005

Using the Born approximation, collision cross sections for the 11S→21P transition in helium have been calculated. The wavefunctions employed are those used by J. A. Wheeler in the calculation of oscillator strengths.
Inelastic Collision Cross Sections of Carbon Monoxide
Authors: Lassettre E. N. , Silverman S. M.
Published: January 2005

Electron collision cross sections for three transitions in carbon monoxide have been determined as a function of angle. The results are in good accord with the general predictions of the Born approximation.
Additional Collision Cross Sections for Helium Especially in the Ionized Continuum
Authors: Silverman S. M. , Lassettre Edwin N.
Published: January 2005

Additional data on the cross sections for the 1 1S→2 1P transition are reported and compared with extended theoretical calculations. Some additional results on the 1 1S→2 1S transition are also reported.

Collision cross sections and oscillator strengths have been determined for several excitations in the ionized continuum. Oscillator strengths agree well with theory except in the vicinity of the double electron excitations. Two peaks which involve simultaneous excitation of two electrons have been observed. A discontinuity in the ionized continuum on passing through a peak corresponding to a double excitation has been observed.
Higher-Resolution Study of the Electron-Impact Spectrum of Helium
Authors: Skerbele Ausma M. , Lassettre Edwin N.
Published: January 2005

An electron source is described that provides, by means of an electrostatic velocity analyzer, for velocity selection on an electron beam before scattering. The energy width of the electron beam is sufficiently reduced to resolve the transitions to the 5 1P and 6 1P states in helium. These states are separated by 0.17 V. Relative oscillator strengths for two additional members of the Rydberg series 1 1S→m 1P have been determined by study of the zero angle electron scattering.
Improvement of One-Center Wavefunctions over Small Regions
Authors: Bishop D. M.
Published: January 2005

A method of improving one-center wavefunctions for molecules containing hydrogen atoms is given. It is shown that the mixing of a novel type of wavefunction centered at each proton [Ψ = (15/2πP5) ½ (P—ρ) for ρ<P and zero elsewhere, where ρ is the distance from the proton and P is a constant] can lead to a significant improvement in both the molecular energy and the wavefunction for the four simple systems considered.
On the Kinetic Theory of Dense Fluids. XV. Some Comments on the Rice—Allnatt Theory
Authors: Berne Bruce , Rice Stuart A.
Published: January 2005

In this paper it is shown that, within the framework of the Rice—Allnatt theory of transport phenomena in simple dense fluids, the cross-correlation functions of the soft and hard forces are exactly zero. A relation is found between the soft doublet and soft singlet friction coefficients, and an approximate theory is developed for the soft components of the shear viscosity and the thermal conductivity. The main assumption in this approximation is that of small step diffusion. The soft doublet friction coefficient which is derived in the first part of the paper is then used to calculate values for the soft force contribution to the viscosity and thermal conductivity. It is shown that the equilibrium properties of simple liquids are not known with sufficient accuracy to allow a complete test of the R—A theory, but that the expressions in this theory seem to be moderately insensitive to the equilibrium properties used.
Investigation of the Low-Frequency Motions in Isotactic and Atactic Polypropylene by Neutron Inelastic Scattering
Authors: Safford G. J. , Danner H. R. , Boutin H. , Berger M.
Published: January 2005

The vibrational spectra between 1000 and 30 cm—1, derived from measurements of the inelastic scattering of ``cold'' neutrons, are presented for isotactic polypropylene at sample temperatures below and above both the glass transition and the melting point. A tentative assignment of the observed modes is suggested by comparison with recent calculations by Miyazawa, Ideguchi, and Fukushima of the optically active phases of the fundamental vibrations for an isotactic helical polypropylene chain and with the neutron measurements of the low-frequency modes in highly crystalline polyethylene. In addition to the skeletal optical modes, the neutron spectra for isotactic polypropylene indicate the existence of two acoustic modes—skeletal deformation and skeletal torsion—with high-frequency limits at 620±50 cm—1 and 110±10 cm—1, respectively. As in polyethylene, these modes appear to be strongly influenced by the presence and phase of the disorder in the sample. Similar spectra for atactic polypropylene above and below the glass transition show a much less pronounced structure, although weak bands are observed which correlate well with the skeletal optical modes observed in the isotactic polymer.
Second-Order Perturbation Theory in Atomic and Molecular Quantum Mechanics (Application to the Electric Dipole and Quadrupole Polarizabilities and Shielding Factors of the Beryllium Atom)
Authors: Kelly Hugh P. , Taylor Howard S.
Published: January 2005

A new method, previously used in calculating atomic correlation energies, is shown to be applicable to a wide variety of atomic and molecular problems. Use is made of the fact that it is possible in many problems to calculate exactly the first-order perturbation correction to uncoupled Hartree—Fock wavefunctions and also second-order energy expressions. Particular application is made to the numerical calculation of dipole and quadrupole polarizabilities and shielding factors for the beryllium atom.
Intrinsic Viscosity of Stiff-Chain Macromolecules
Authors: Hearst John E.
Published: January 2005

A general theory for the intrinsic viscosity of any segment distribution with cylindrical symmetry is developed. The theory avoids the substitution of a scalar for the Oseen tensor. Application is made to the wormlike coil and the weakly bending rod. The Flory φ for the random coil calculated by this method is 2.20×1021. The theory is in agreement with the results of Kirkwood and Auer in the limit of the rigid rod.
Infrared Spectrum of ν2 of Dichloroborane and Dichloroborane-d
Authors: Lynds L. , Bass C. D.
Published: January 2005

The ν2 fundamental of HBCl2 and DBCl2 has been observed under high resolution. A series of evenly spaced lines occurs, which has the appearance of a ⊥ band of a symmetric top molecule. Analysis of the spectra gives an approximate value for the smallest moment of inertia, from which the following molecular dimensions are calculated: B–H bond length=1.13±0.2 Å and Cl–B–Cl bond angle=119.7±3°. The position of the band center, 2616.9 cm—1, for HBCl2, has also been determined.
Paramagnetic Resonance of Divalent Iron in Calcium Oxide
Authors: Shuskus Alexander J.
Published: January 2005

Paramagnetic resonance of divalent iron in single crystals of CaO has been observed at 4.2° and 2°K. The features of the resonance spectrum are: (1) a broad line at g≃3.30; (2) a narrow resonance superimposed upon the broad line at g=3.298±0.002; (3) an asymmetric line at half field with a high-field cutoff at g≃6.58. At 4.2°K the double quantum transition exhibits an anisotropic behavior with microwave power and orientation. There is evidence of tetragonal distortions about the Fe2+ ion which coincide with the cubic crystal axes. These distortions cannot be ascribed with any degree of certainty to Jahn—Teller splitting.
Cubic Cell Model for Self-Diffusion in Liquids
Authors: Houghton Gerald
Published: January 2005

A cubic cell model for viscous flow and self-diffusion in liquids has been developed such that a linear Langevin equation for condensed systems can be deduced directly from the corresponding Navier-Stokes equation, the molecular friction coefficient being then related to the viscosity and cell size. On restricting interactions to nearest neighbors in cubic symmetry involving an arbitrary choice of the number of nearest molecules and linking the friction coefficient and diffusivity by stochastic considerations, an expression has been produced that predicts self-diffusion coefficients from viscosity and density data with an average deviation of 9%.
Optical Pumping and Chemical Reactions
Authors: McNeal R. J. , Bernheim R. A. , Bersohn R. , Dorfman M.
Published: January 2005

Optical pumping in this paper refers to the orientation of the angular momenta of atoms and molecules by light. The phenomenon of spin exchange raises the possibility of the use of a gas of pumped atoms as a highly sensitive detector of free radicals. It is shown, however, that a suitable buffer gas may not have atoms of high atomic number, and may not be polar or aromatic and must be extraordinarily inert chemically. Examples are He, Ne, Ar, H2, N2, CH4, C2H6, C2H4, and—for a short time—CO. These highly stable molecules decompose into radicals at ordinary temperature only under irradiation with vacuum ultraviolet photons or with particles. Optically pumped gases may be useful, therefore, in studying the reactions involved in vacuum uv photolyses of simple hydrocarbons.
Ionization of Molecular Excitons
Authors: Choi Sang-il
Published: January 2005

As a study of the role of photons in the creation of charge carriers, we considered the relative rate of ionization of molecular excitons through the absorption of photons compared to the two-exciton autoionization mechanism. The ratio is estimated to be less than 4×10—2 in Silver's experiment on photoconduction. We also considered a general case in which two beams of light are used. A simple formula is obtained when one of the beams is incapable of creating excitons but capable of ionizing excitons.
Infrared Spectrum of Diazirine
Authors: Ettinger Raymond
Published: January 2005

The infrared spectra of diazirine, diazirine-d1, and diazirine-d2 have been obtained and analyzed in the light of their cyclic structure. In contrast to the linear isomer diazomethane, the N=N bond in diazirine behaves as a normal azo linkage and absorbs in the region of 1600 cm—1 in all three isotopic derivatives. A normal coordinate analysis, derived from a potential function previously used with cyclopropane, lends reasonable support to the assignments made.
Raman Spectra of Simple Ionic Mixtures in Molten Nitrates
Authors: Janz George J. , Kozlowski Theodore R.
Published: January 2005

Investigations of ionic mixtures in molten NaNO3 and KNO3 by Raman spectroscopy are reported. The solute species include AgNO3, TlNO3, Mg(NO3)2, Ca(NO3)2, Sr(NO3)2, Ba(NO3)2, NaCl, and NaBr. The Raman data show a continuous but gentle shift in certain vibrational frequencies (e.g., ν1). Loss of degeneracy of ν3 in certain mixtures (e.g., Ca++, Sr++, Ba++), and the appearance of the Raman forbidden frequency, ν2, as a weak line (in presence of Tl+) are also observed. The Raman data are discussed relative to current structural concepts for molten inorganic mixtures.
Absorption Intensity and Fluorescence Lifetimes of Molecules
Authors: Ware William R. , Baldwin Bernard A.
Published: January 2005

The fluorescence lifetimes of a series of molecules have been measured using a nanosecond flash. The purpose of the measurement was to permit a comparison between the natural lifetime calculated from the theory of Strickler and Berg and that calculated from the quantum efficiency and the observed lifetime.
Pressure-Induced Shifts of DCl Lines Due to HCl: Shift Oscillation
Authors: Jaffe J. H. , Hirshfeld M. A. , Ben-Reuven A.
Published: January 2005

Pressure-induced shifts of DCl lines (2–0 band) due to HCl have been observed. In addition to the expected J dependence there is a striking oscillation from line to line of the magnitude of the shift. It is suggested that this phenomenon is due to near-resonant dipole interactions between HCl and DCl.
Calculation of Chemical Shifts. I. General Formulation and the Z Dependence
Authors: Jameson Cynthia Juan , Gutowsky H. S.
Published: January 2005

Explicit expressions for the paramagnetic contribution σ(2) to the nuclear magnetic shielding are derived in the valence bond and the LCAO—MO framework including d as well as p orbitals on the atom in question. A survey of published experimental data reveals a periodic dependence of the range of chemical shifts on atomic number, which is explained in terms of the paramagnetic contribution to the chemical shift and its dependence on 〈1/r3〉 for the bonding electrons.

A brief discussion is given of related but more complex periodicities in the electron coupling of nuclear spins, using the M—H coupling in Group IV hydrides as an example. It is suggested that the anisotropy in the nuclear shielding and internuclear coupling tensors may combine to give observable linewidth differences in the high-resolution NMR spectra of directly bonded nuclei of large Z.
Quasichemical Approximation and Hole Theory of a One-Dimensional Fluid
Authors: McLellan A. G.
Published: January 2005

In a one-dimensional lattice whose sites are occupied by a mixture of A molecules and B molecules an exact formula is derived for the number of configurations for which specified numbers of A molecules have 0, 1, or 2 nearest-neighbor A molecules. A hole theory is derived for a one-dimensional fluid, approximate only to the extent that the formula for the free volume per cell may not be exact, and is applied to the case of rigid spheres. Comparison in this case may be made with the exact formulas for the equation of state and the entropy. The solution obtained by using the above exact enumeration of configurations is also com-with that obtained using the approximation of Grindlay.

In deriving the formulas enumerating configurations, it is shown that in one-dimensional lattices, the quasichemical formula is exact, apart from a factor dependent only on the total numbers of A and B molecules.