bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of the I2-Catalyzed Decompositions of Acetaldehyde and Propionaldehyde in the Vapor Phase
Authors: O'Neal Edward , Benson Sidney W.
Published: January 2005

The kinetic data of Rollefson and Faull for the iodine-catalyzed decomposition of acetaldehyde are summarized, and the RF mechanism of the reaction is critically reviewed. A new mechanism for the iodine-catalysis reaction is presented. Properties predicted from the new mechanism are compared with the observed reaction rates, reaction orders, and the unusual experimental behavior of the reactive system. Excellent agreement is found. The reaction is initiated by an iodine atom attack on acetaldehyde to abstract a hydrogen atom and produce hydrogen iodide and an acetyl radical. The rate-determining step for the reaction is the decomposition of the acetyl radical, which is a unimolecular pressure-dependent decomposition. The characteristic falloff of the rate of decomposition in the later stages of reaction is shown to be the result of this pressure dependence. The mechanism is also applied to the iodine-catalyzed decomposition of propionaldehyde. Satisfactory agreement with observed reaction orders and reaction rates is obtained. From these data the decomposition kinetics of the propionyl radical is predicted to be pressure-dependent at normal experimental pressures.
Absolute Infrared Intensities of the Fundamental Absorption Bands in Solid CS2
Authors: Yamada Haruka , Person Willis B.
Published: January 2005

Absolute infrared intensities have been measured for ν2 and ν3 of CS2 in the solid phase. Path lengths were measured by counting interference fringes as the solid is condensed onto a cold window. The index of refraction of the solid film is estimated from the intensity of the fringe pattern on different windows of known index of refraction. The problem of choosing a suitable background is discussed. Although two different kinds of films were formed, the intensities were identical within experimental error. The intensities found for ν2 and ν3 were 850±100 and 80 000±14 000 darks, respectively. These values are quite comparable to the intensities found in liquid CS2, and are both higher than found in the gas phase. Hence, the intensity sum rule does not hold for this crystal. The observed intensification is compared with that predicted from the simple field effect, using an elliptical cavity, and found to agree quite well. Hence, we conclude that CS2 molecules do not interact strongly in the crystal in ways which affect the intensity. The ``ideal'' behavior is tested further in a comparison of the observed frequency shift with that calculated from the Kirkwood—Bauer—Magat theory; again the agreement is quite good for ν3 where the predicted shift is large. For ν2, with a smaller predicted shift, the agreement is poor, indicating that other forces are at least as large.

Finally, the infrared spectra and x-ray powder pattern are used in combination to estimate the crystal structure. Both are consistent with an orthorhombic space group D2h12, with two molecules per unit cell (a=5.45, b=8.16, and c=3.74 Å). Although this space group is not determined uniquely, the crystal splitting was calculated from the dipole—dipole model, assuming that the structure was approximately correct in locating the molecules. The calculated splitting for ν3, where it is large, agrees very well with the observed splitting; for ν2, where the calculated dipole—dipole splitting is small, the agreement with experiment is poor.
Solid Infrared Spectra, Assignment and Vibrational Potential Function of Diazomethane
Authors: Moore C. Bradley , Pimentel George C.
Published: January 2005

Infrared spectra of pure solid diazomethane and diazomethane in nitrogen or argon are given here for the molecules CH2N2, CD2N2, CHDN2, and CH2N15N. These data combined with the gas-phase spectra reported earlier provide a basis for a reassignment of the vibrational spectrum. The vibrational potential function, centrifugal distortion constants, Coriolis coupling constants, and thermodynamic functions of diazomethane have been calculated. The out-of-plane hydrogen bending force constant is found to be unusually low, 0.045×10—11 erg rad—2. This is about one-fifth of that for ethylene and about one-half of that for ketene. The observed divergence of the energy levels of the out-of-plane hydrogen bending mode shows that there must be a large positive quartic contribution to the potential function for this motion.
Stabilization of Free Radicals and Reactive Molecules in Cavities of the Water Clathrate Lattice
Authors: Goldberg Paul
Published: January 2005

Experimental methods are described for placing free radicals and reactive molecules in cavities of the water clathrate lattice. When located at cavity sites, diffusion and recombination of the active species is markedly reduced up to relatively high temperatures. The experimental procedure begins with the synthesis of water clathrates of H2S, CH3SH, and C2H5SH. Ultraviolet photolysis of CH3SH and C2H5SH produces H atoms which diffuse away leaving the CH3S and C2H5S radicals trapped in the cavities. The H atoms react with other guest molecules to produce additional stabilized radicals and H2. Photolysis of H2S clathrates is more complex, producing probably S2 as the stabilized species. The presence of the active species is monitored by diffuse reflectance spectrophotometry. Temperatures at which stabilization is achieved extend to —20°C and above, thus exceeding the range attainable by other matrix isolation techniques for small reactive molecules.
Ion—Ion Recombination
Authors: Brueckner Keith A.
Published: January 2005

The three-body recombination rate for molecular ions is calculated at low density, including the effect of dissociative collisions on the molecular complex initially formed by the recombination process. The effect of an increase in ionic mass due to the attachment of neutral molecules to the ion is also determined. The recombination rate is found to be markedly reduced, by either effect, from that predicted by the elementary Thomson theory.
Theory of the Vibrational Structure of Molecular Exciton States
Authors: Merrifield R. E.
Published: January 2005

The interaction of excitons with molecular vibrations is formulated in the second quantization formalism. The Hamiltonian which describes interacting excitons and molecular phonons is derived. The exciton creation and destruction operators can be eliminated resulting in a reduced Hamiltonian which contains phonon operators only. A natural variational function for the lowest state of the reduced Hamiltonian is suggested by the forms of the eigenstates for the two exactly soluble limiting cases of vanishing exciton—phonon coupling and vanishing exciton bandwidth. Numerical calculations of the properties of the exciton in the lowest state are carried out for a simple one-dimensional nearest-neighbor interaction model.
Influence of Hydrodynamic Interaction on the Viscoelastic Behavior of Dilute Polymer Solutions in Good Solvents
Authors: Tschoegl N. W.
Published: January 2005

The treatment by Ptitsyn and Eizner of the dynamics of dilute polymer solutions for dominant hydrodynamic interaction, taking into account excluded volume effects, is extended to the general case for changing hydrodynamic interaction. The function Φ (h, ε) is tabulated for selected values of ε, the parameter which accounts for the expansion of the coil due to excluded volume effects.

An approximate derivation of the storage and loss moduli from this theory is proposed. According to this calculation, an increase in ε causes a shift of the frequency dependence of the moduli from Zimm-like toward Rouse-like behavior. The determination of ε from experimental data is discussed.
Theoretical Investigations on the Light Scattering of Spheres. XIV. Wavelength Exponent of Differential Scattering Spectra for an Angle of Observation of 90°
Authors: Bhatnagar Hari L. , Heller Wilfried
Published: January 2005

Exact equations are given for the wavelength exponent of experimental differential scattering spectra (n90)0 observed at an angle of 90° with respect to an incident unpolarized beam. Numerical values of the theoretical exponent n90 are derived from the Mie functions for α=0.5 (0.1) 0.8 (0.2) 6.4 and m=1.05 (0.05) 1.30. Values of the quantity [∂ln(I90/Ioc)/∂m] are also computed for α=0.8 (0.4) 2.4 and the above m values. Advantages and disadvantages of a practical application of (n90)0 for particle size determination are enumerated.
X-Ray Diffraction Refinement of the Calcium Tungstate Structure
Authors: Zalkin Allan , Templeton David H.
Published: January 2005

The crystal structure of CaWO4 (scheelite) has been refined with single-crystal x-ray diffraction data. For the tetragonal cell a=5.243±0.002, c=11.376±0.003 Å. Oxygen coordinates 0.1504, 0.0085, and 0.2111 correspond to Ca–O distances 2.44 and 2.48 Å and W–O distances 1.78 Å.
External Heavy-Atom Spin—Orbital Coupling Effect. V. Absorption Studies of Triplet States
Authors: McGlynn S. P. , Azumi T. , Kasha M.
Published: January 2005

The lowest energy T1←S0 transitions of the molecules chlorobenzene, 1-chloronaphthalene, anthracene, 9,10-dichloroanthracene, 9,10-dibromoanthracene, naphthacene, pyridine, and phenazine have been investigated in a variety of solvents, some of which contain atoms of large atomic number (henceforth called ``heavy atoms''). It is shown that in heavy-atom solvents an increase of the T1←S0 absorptivity occurs, and the technique of external heavy-atom perturbation is demonstrated as a method of conveniently locating and validating T1←S0 transitions. Monitoring experiments in which nonspin-intercombination transitions, such as S1←S0 transitions of the molecule being investigated, and S1←S0 transitions of low-level contaminants have been subjected to external heavy-atom perturbation, have permitted the conclusion that the method is unique for T1←S0 transitions. It is further verified that the external heavy-atom effect is a spin-orbital perturbation in nature. Much new data on triplet-state energies and lifetimes has been obtained and is contained herein.
Pressure Broadening of DCl by HCl and of HCl by DCl. A Comparison of Experimental Results with Anderson's Theory
Authors: James Thomas C. , Thibault Robert J.
Published: January 2005

Linewidths in the 1–0 band of DCl broadened by HCl and in the 1–0 band of HCl broadened by DCl are reported for rotational levels up to | m | = 15 and 13, respectively. These experimental results are compared with calculated values using Anderson's theory as amplified by Tsao and Curnette. Calculations are made at 300°K for quadrupole moments of 2, 4, and 6 D·Å and calculations at 194.5°K are also made for a Q of 6 D·Å.
Hole Theory of Fluids and the Quasichemical Approximation
Authors: McLellan A. G.
Published: January 2005

The assumption of a linear relation between the free volume and the number of neighboring holes is used in the hole theory of fluids and the partition function is evaluated using the quasichemical approximation. This method introduces the number of neighboring molecules and the cell volume as independent parameters with respect to which the free energy is minimized. On this theory the assumption of the random distribution of neighboring holes is found not to be satisfied under all conditions. Thermodynamic functions are evaluated and shown to give improved agreement with experiment over the results of previous theories.
Mass-Spectrometric Investigation of the Nickel—Bromine Surface Reaction
Authors: McKinley John D.
Published: January 2005

Mass-spectrometric measurements have been made of the volatile products of the reaction between nickel and bromine at nickel temperatures between 300° and 1600°K, and at bromine pressures between 10—7 and 10—4 mm Hg. Bromine dissociates on the surface at a temperature-dependent rate; the fraction dissociated is much less than that corresponding to equilibration of the incident bromine with the hot nickel surface. NiBr2 and NiBr are formed in surface reactions at rates proportional to the bromine pressure. The former product is formed between 600° and 1200°K with a maximum in the rate at 900°; the latter is formed above 1200° at a rate increasing with nickel temperature.
Isotopic Exchange of the Excited Oxygen Atoms with CO218 and Their Collisional Deactivation
Authors: Yamazaki H. , Cvetanovic R. J.
Published: January 2005

Isotopic exchange of the excited oxygen atoms produced by photolysis of N2O at 1849 Å with CO218 has been studied at room temperature. The exchange is strongly suppressed by addition of xenon, and is not affected by SF6. This provides further evidence for the effective deactivation of the electronically excited oxygen atoms by collisions with xenon atoms, and lack of deactivation on collisions with SF6 molecules. Relative values of the rates of exchange and deactivation have been obtained as well as the relative rate of reaction of the excited atoms with N2O.
First-Order Dispersion Forces
Authors: Stephen M. J.
Published: January 2005

The interaction energy between two atoms, one of which is excited, is investigated. The form of the interaction depends on the relation between the distance R separating the atoms and the wavelength k1—1 of the transition from the ground state to the excited state. If k1R<1 the photon may be trapped between the two atoms leading to the well-known dipole—dipole interaction. If k1R>1 the interaction is small, the state of the interacting atoms is not a stationary state and the photon is emitted after a time determined by the spontaneous emission probability.
Optical Activity of Coordination Compounds. II. A Molecular Orbital Model and an Analysis of Experimental Data for Complexes of Trigonal Symmetry
Authors: Karipides A. G. , Piper T. S.
Published: January 2005

A molecular orbital model for the optical activity of trigonal coordination compounds is developed. It is shown that the combination of intensity data from solution and crystal spectra with optical activity data from solution allows one to calculate empirical values of the electric moment matrix elements for the one-electron transition t2→e. This empirical electric moment matrix is in good agreement with that predicted by the molecular-orbital model, and it is in nearly as good agreement with that of the ionic model as far as the ratios of the matrix elements are concerned. Empirical values of the magnetic moment of the electronic transitions are interpreted qualitatively in terms of metal—ligand covalency. The problem of determining the absolute configuration from the sign of the rotational strength is discussed.
Absorption Spectrum of the ``Pink'' Afterglow of Nitrogen in the Vacuum Ultraviolet
Authors: Bass Arnold M.
Published: January 2005

The absorption spectrum of the short-lived ``pink'' afterglow in nitrogen was photographed in the vacuum ultraviolet from 1600 to 1150 Å. A large number of relatively intense absorption bands were observed. It is suggested that these may result from transitions between the ground state (X 1Σg+) and several excited electronic states (b 1IIu, b′ 1Σu+, and others) in which ground-state vibrational levels of the ground electronic state are populated to very high levels (up to about v″=20). It appears that more than 10% of the nitrogen molecules are excited to vibrational levels greater than v″=8.
Oxygen-17 Nuclear Magnetic Resonance in Paramagnetic MnO and CoO
Authors: O'Reilly D. E. , Tsang Tung
Published: January 2005

A nuclear magnetic resonance study of O17 resonance in paramagnetic MnO and CoO is reported. The internal fields at the oxygen nuclei were measured. Interpretation of the measured fields showed that the spin densities in the oxygen 2s orbitals were 0.76% for MnO and 0.66% for CoO. Nuclear relaxation times have also been measured and compared with Moriya's theory.
Effect of Molecular Shape on Nuclear Magnetic Relaxation. II. Quadrupole Relaxation
Authors: Shimizu Hiroshi
Published: January 2005

The dependence of quadrupole relaxation in NMR upon molecular shape is examined by regarding the molecule as a rigid ellipsoidal body which shows anisotropic rotational Brownian motions. Dependence of relaxation times upon the angle between the direction of the maximum field gradient and that of the molecular axis is considered also; the complex angular dependence of the relaxation times is derived, which suggests that careful examinations must be taken when we use the information on molecular motion from the other measurements. For example, the effective correlation time obtained from the quadrupole relaxation cannot be used directly to compute the proton relaxation times in an accurate precision.

The use of the ordinary theory of anisotropic Brownian motion in molecular system is examined, where the constituents of the ``liquid'' have comparable dimension with that of the solute molecule and they are by no means ``homogeneous.'' The improved theory is applied to the quadrupole relaxation in the system of axial ratio=2, which predicts that the spectral density is about 2∼8 times larger than the one given by the Debye—Bloembergen—Perrin—Favro theory.
Paramagnetic Resonance Spectrum of Irradiated Single Crystals of L-Cystine Dihydrochloride
Authors: Box Harold C. , Freund Harold G.
Published: January 2005

The principal absorption in the ESR spectrum of single crystals of cystine dihydrochloride irradiated at 77°K is attributed to the free radical ([–S–CH2–CH(NH3+Cl−)COOH]2)+in which the unpaired electron is localized primarily on the sulfur atoms. The principal values of the g tensor are 2.017, 2.018, and 2.002. Each of the four CH2 protons contributes a nearly isotropic hyperfine splitting of approximately 8.5 G.
Strengths and Self-Broadened Widths of the Lines of the Hydrogen Bromide Fundamental Band
Authors: Babrov Harold J.
Published: January 2005

The strengths and self-broadened half-widths of the lines of the fundamental band of HBr have been measured by a curve-of-growth method. The method uses a correction for two overlapping lines recently devised by Sakai. The squares of the electric dipole matrix elements, |M01(m)|2, for the lines have been calculated from the strengths. From the theory of Herman and Wallis and |M01(0)|2, the dipole moment derivative M1 is found to be 0.468×10—10 esu. From the slope at m = 0 of |M01(m)|2 the vibration—rotation interaction parameter, θ, is found to be 1.20. The dependence of the strengths on rotational quantum number J is compared to the J dependence of the strengths of the other hydrogen halides and is compared to theory. A similar comparison is made for the J dependence of the half-widths.
Vibrational Analysis of Substituted and Perturbed Molecules. I. The Exact Isotope Rule for Molecules
Authors: DeWames R. E. , Wolfram T.
Published: January 2005

The Green's function and partitioning techniques developed for treating the lattice-impurity problem have been applied to molecular systems. The vibrational frequencies of isotopically substituted molecules are obtained exactly and explicitly without recourse to a force constant model. It is shown that the mixing of the symmetry coordinates of the unperturbed molecule is determined uniquely from the experimental frequencies. The usual product rule is obtained; however, it does not involve the moments of inertia. The more general problem involving changes in the bond strength is formally presented. Explicit expressions for the vibrational frequencies for any isotopic substitution of a nonlinear XY2 molecule are derived. Numerical results for H2O and H2S are given.
Radiolysis of Simple Aromatics in Boric Acid Glass
Authors: Hughes Floyd , Kirk Russell D. , Patten Frank W.
Published: January 2005

Electron paramagnetic resonance studies have been made of the stable free radicals produced by x irradiation of aromatic hydrocarbons dissolved in partially dehydrated boric acid glass. In general, singly charged molecular ions were not found to be the sole species.

Deuterium substitution in the boric acid glass showed that all end point radicals contained hydrogen from the matrix. All glasses exhibited a 100–140 G EPR pattern, which has been interpreted as that of radicals produced by formation of a —CH2— group in a benzene ring.
Variational Method for Classical Statistical Mechanics
Authors: Girardeau M. D.
Published: January 2005

The classical analog of Bogolubov's variational principle for quantum statistics is derived, and some applications are suggested.
Electron Spin Resonance Studies of Irradiated Single Crystals of Creatinine and Creatine
Authors: Ueda Hisashi
Published: January 2005

The electron spin resonance spectra of x-irradiated single crystals of creatinine: creatinine HX (X=HO2, F, Cl, Br, I, and NO3): Ca creatine, and creatine phosphate, have been studied at room temperature. The ESR spectrum of an x-irradiated single crystal of creatinine at 77°K has also been studied. The free radicals formed in these compounds have similar structures to those formed in irradiated N-acetylglycine, glycylglycine, and diketopiperazine. The unpaired electron spin density distribution was computed by a Hückel molecular orbital method using an electronic computer, and was compared with the experimental results.

The anisotropic components of the observed splitting factors were relatively smaller in these compounds than those found in N-acetylglycine, glycylglycine, diketopiperazine, and malonic acid. This can be explained by considering the effective nuclear charge on the vicinal nitrogen atom which will affect the s character of the unpaired electron on the carbon atom, where the electron has main spin density of some 0.5.

The free radical, first formed, has a structure in which the unpaired electron is localized on three atoms. This, then, transforms to a delocalized species with a larger conjugated system. The delocalization energy for this transformation is about 8.3 kcal/mole.
Microwave Spectrum, Molecular Structure, and Quadrupole Coupling Constants of 2-Chloropropane
Authors: Tobiason F. L. , Schwendeman R. H.
Published: January 2005

The microwave spectra of (CH3)2CHCl35, (CH3)2CHCl37, (CH3)2CDCl35, (CH3)2C13HCl35, C13H3CHCl35CH3, CH2DCl35CH3 (3 species), and CD3CDCl35CH3 have been examined and a complete structure has been obtained by the substitution method. The parameters obtained are as follows: r(CC) = 1.522 Å, r(CCl) = 1.798 Å, r(CHsec) = 1.091 Å, r(CHmethyl) = 1.092 Å, ∠CCC = 112.7°, ∠CCCl = 109.4°, ∠CCHsec = 109.9°, ∠CCHα = 110.9°, ∠CCHβ,γ = 109.7°.

The quadrupole coupling constants in the principal axis system of (CH3)2CHCl35 have been determined to be χaa = —61.49 Mc/sec, χbb = 34.81 Mc/sec, and χcc = 26.68 Mc/sec. These values are consistent with χzz = —69.61 Mc/sec assuming a cylindrical charge distribution near the Cl nucleus, or with χzz = —67.82 Mc/sec and η = 0.0275 assuming that the z axis and the CCl internuclear line coincide.

From the absence of observable splitting in certain high J transitions in CD3CDCl35CH3, it has been concluded that the potential barrier hindering internal rotation of the methyl groups is greater than 3450 cal/mole.
Determination of the Efficiency of Triplet Energy Migration in Benzophenone Crystals
Authors: Hochstrasser Robin M.
Published: January 2005

The total emission—phosphorescence plus fluorescence—spectra of benzophenone crystals containing small quantities of 1,2-benzanthracene (BA) are described. The electronic states of BA and benzophenone are such that the lowest triplet state but not the lowest singlet state of BA can be populated directly by energy transfer from the lowest triplet of benzophenone. The relative efficiencies of fluorescence and phosphorescence of the BA provide evidence that triplet exciton migration is occurring in the host lattice. The fact that the host-crystal phosphorescence yield is temperature-dependent provides another experimental probe into the energy transfer probabilities for this crystal. The combination of these two types of experiment gives some indication of the interaction energy between an excited molecule of benzophenone in the lattice and neighboring excited molecules.
Polarized Emission and Triplet—Triplet Absorption Spectra of Aromatic Hydrocarbons in Benzophenone Crystals
Authors: Hochstrasser Robin M. , Lower Stephen K.
Published: January 2005

The polarization of the phosphorescence of naphthalene, anthracene, pyrene, and chrysene as guest in the benzophenone lattice have been examined. Considerable out-of-plane intensity has been shown to be present in these transitions. The results have confirmed conclusions from previous experimental observations and have led to certain assignments for the lowest triplet states which are in agreement with theoretical predictions.

The triplet—triplet absorption spectra of naphthalene, anthracene, and chrysene have been detected using polarized light and the mixed crystals. All these T—T transitions were polarized in the aromatic molecular planes, in accordance with theory.

The phosphorescence of pyrene in benzophenone has been analyzed and tentatively interpreted as triplet—singlet emission of the pyrene dimer.
Nuclear Magnetic Resonance Study of the Solvation of Co++ in Methanol and Methanol—Water Mixtures
Authors: Luz Z. , Meiboom S.
Published: January 2005

Proton magnetic resonance spectra of solutions of Co(ClO4)2 in acidified methanol, and in methanol—water mixtures are reported. At temperatures below about —50°C separate peaks for the bulk methanol and for the methanol bonded to Co++ are observed, and methanol exchange is too slow to contribute appreciably to the observed linewidths. Peak intensity measurements give a coordination number of six for Co++ with respect to methanol. From the temperature dependence of the peak frequencies, values of the hyperfine interaction between the bonded methanol protons and the Co++ ion were obtained. The results are +8.8×105 cps for the OH protons and +3.9×105 cps for the CH3 protons. The linewidths are shown to be predominately determined by electron—proton dipole—dipole interaction. The relevant correlation time is the electron relaxation time, which is approximately 5×10—13 sec at —60°C. This time decreases with increasing temperature, with an apparent activation energy of 0.9 kcal mole—1.

In methanol—water solutions, additional lines, due to mixed methanol—water complexes of cobalt, are observed. Equilibrium constants for the formation of the mono- and dihydrated mixed complexes were obtained from measurements of peak intensity as function of water concentration.

At temperatures above about —50°C the rate constant of methanol exchange between complexes and bulk solvent was obtained from the excess widths of the peaks. Comparison of the OH and CH3 linewidths shows that whole methanol molecules exchange, i.e., proton exchange between the complexes and the solution is relatively unimportant.
Classical Model for the Study of Isotope Effects in Energy Exchange and Particle Exchange Reactions
Authors: Rubin Robert J.
Published: January 2005

An idealized model of a colinear collision between a diatomic molecule AB and an atom C is studied. The three-atom potential-energy surface is an L-shaped region consisting of two flat-bottomed troughs with vertical walls; and the rectangular corner region of the L is at a higher uniform potential. The dependence of the classical energy exchange probability on the relative masses of the three particles is investigated systematically for this model. All possible collisions are considered in which the initial distribution of energy between the vibrational and relative translational components is fixed. Formulas are derived which express the average fraction of vibrational energy after collision as a function of the fraction of vibrational energy before collision. In the reaction AB+C→A+BC, the dependence of the classical particle-exchange probability on the relative mass of Particles A and C is determined in the limiting case where the mass of Particle B is infinite. In addition to the relative mass parameter, the particle exchange probability depends upon the initial vibrational and relative translational energies and the height of the potential barrier in the corner region VII. A thermal average probability for particle exchange is determined which depends upon two parameters: the relative mass of A and C and VII/kT. This dependence on the relative mass, an isotope effect, is a product of classical mechanics.
Crystal Structure of HI3·2C6H5CONH2: A Model of the Starch—Iodine Complex
Authors: Reddy J. M. , Knox K. , Robin M. B.
Published: January 2005

The lattice of the HI3·2C6H5CONH2 inclusion complex is triclinic (a=20.828 Å, b=9.885 Å, c=9.588 Å, α=95°46′, β=101°54′, γ=94°44′) with four molecules per unit cell. The host structure consists of dimerized benzamide molecules stakced in such a way as to form long channels in which the guest tri-iodide ions are aligned. Each channel is filled with two chains of tri-iodide ions polymerized end to end, the chains being separated by the van der Waals distance, 4.6 Å. Within the chains, the tri-iodide ions are bent about 3° from linear and are asymmetric with one bond being 0.02 Å longer than the other. The distance between ends of adjacent tri-iodides within a chain is only 3.8 Å, indicating a strong attractive interaction between the ions. It is postulated that a single chain of tri-iodide ions of the above description is the chromophore in the blue starch—iodine complex.
Spin Relaxation of Optically Pumped Rubidium Atoms in Molecular Buffer Gases
Authors: McNeal Robert J.
Published: January 2005

Short spin relaxation times for rubidium atoms, oriented by optical pumping, have been observed in the presence of benzene, ammonia, and dimethyl ether buffer gases. The disorientation cross sections of these gases in rubidium are obtained from relaxation times measured in mixtures with molecular nitrogen. The partial pressures of the gases were low compared to the nitrogen pressures in the mixtures, and the diffusion coefficient of rubidium in the mixtures was assumed to be the same as in pure nitrogen. The disorientation cross sections at 55°C are 7±1×10—19 cm2 for benzene, 8±2×10—18 cm2 for ammonia, and 3±1×10—18 cm2 for dimethyl ether. The cross section of carbon monoxide has also been obtained from the longer rubidium spin relaxation time in this gas. These measurements, complicated by a slow reaction of carbon monoxide with liquid rubidium, yield a cross section of 1±0.5×10—22 cm2 for carbon monoxide.

The cross sections of ammonia, dimethyl ether, and benzene are much larger than cross sections of other molecular buffer gases. A discussion of the relaxation processes in these gases is given. The large cross sections of polar gases with appreciable dipole moments are found to result from an interaction of the rubidium atoms with the electric field of the polar molecules during a collision. Virtual excitation to the p states of the atom by the electric field gives rise to an interaction of the spin of the valence electron with the orbital angular momentum of the p states. The direct contribution of the magnetic field of the moving polar molecule is also considered and found to be small compared to the electric interaction. The large cross section of benzene is assumed to result from a spin exchange interaction with a charge transfer complex of rubidium and benzene formed in very small amounts. If the assumed complex is responsible for the large benzene cross section, the equilibrium constant for its formation can be calculated from an estimate of the spin exchange cross section.
Existence of Caloric Equations of State in Thermodynamics
Authors: Coleman Bernard D. , Mizel Victor J.
Published: January 2005

Using the principle of equipresence, we treat the thermodynamics of continua sufficiently close to equilibrium so that the basic independent variables in constitutive equations can be taken to be the temperature, the temperature gradient, the deformation gradient (or the ``strain''), and the velocity gradient (or the ``rate of strain''). We derive a set of necessary and sufficient conditions on constitutive equations for the validity of the Clausius—Duhem inequality (i.e., the second law) in such continua. Most of these conditions are familiar; among our necessary conditions, however, is one which guarantees the existence of the caloric equation of state (or, equivalently, of the ``Gibbs relation'' for the entropy differential), and which has not previously been thought justifiable by purely macroscopic arguments. Specializing our general results to fluids, we discuss the thermodynamic restrictions on various possible generalizations and modifications of the classical theory of linearly viscous fluids with linear heat conduction.
Atomic Polarization of Sulfur Hexafluoride and of Carbon Tetrafluoride
Authors: Tipton Ann Baugh , Deam A. P. , Boggs James E.
Published: January 2005

A microwave cavity technique, operating at a frequency of 800 Mc/sec, has been used to measure the dielectric constants of SF6 and CF4 between 295° and 630°K. Over this temperature range the molar polarization has been shown to be independent of temperature within an accuracy of a few tenths of a percent. The atomic polarization is calculated and compared with previous measurements of absolute infrared absorption intensities for the two gases. The use of precise dielectric constant measurements as a check on the accuracy of infrared intensity measurements is discussed.
Rotational Relaxation in Rigid Media by Polarized Photoselection
Authors: Lombardi J. R. , Raymonda J. W. , Albrecht A. C.
Published: January 2005

A study is made of the rotational relaxation of solute molecules in media ranging in viscosity from 106 to 1012 P. Viscosities are determined for various mixtures of 3-methylpentane and isopentane at 77°K The solute relaxation is observed by two distinctly different methods both based on polarized photoselection. At the high viscosities a dichroism is produced by polarized photochemistry and the rotational relaxation is followed by monitoring the collapse of the dichroism. At lower viscosities the steady-state depolarization of long-lived phosphorescence is observed. The latter technique is completely analogous to previous work at much lower viscosities where the depolarization of fluorescence is measured. A theory is presented which links the general photoselection equations to proper solutions of the rotational diffusion equation for an isotropic body. The theory is in a form which permits a variety of relaxation studies where solute molecules may be photoselected along different combinations of molecular axes and the photoproduct or the emission viewed along different combinations of molecular axes. Both the steady-state and transient solutions to the theory are satisfactorily tested here and also a Stokes'-law-type relationship between viscosity and relaxation times appears to hold. With further refinement, especially experimental, such studies hold out promise for considerable insight regarding the local environment of solute molecules in such media.
SCF Theory of Localized Electron Sets
Authors: Schmeising H. N. , Miller R. L.
Published: January 2005

This paper describes a method within the LCAO—MO—SCF approximation for calculating pi electron localization energies for aromatic substitution reactions. Pilot calculations on butadiene, naphthalene, and azulene have been carried out using zero overlap (ZDO). A new result is that the relative reactivities of the unique positions in the azulene radical are found to be in agreement with experiment.

In the general theory we have divided a normally delocalized system into two or more sets of partially delocalized electrons. Each group of electrons is described by a unique set of molecular spin orbitals (MSO). Since, in general, it is impossible to guarantee that the wavefunctions of one set are orthogonal by symmetry to those of every other set, the resultant interset Lagrangian multipliers are taken into account by the introduction of interset coupling operators.
High-Density Equation of State for Hard Parallel Squares and Cubes
Authors: Hoover William G.
Published: January 2005

High-density systems of hard parallel squares and cubes enclosed in rigid containers are considered. Evaluation of the exact volume-dependence of the configurational integral shows that such systems obey the free-volume equation of state. Low order deviations from the free-volume theory, found by Salsburg and Wood in an analogous calculation for hard circles and spheres, are not found for squares and cubes.
Heat Capacities of Cubic and Hexagonal Ammonium Hexafluosilicate from 25° to 300°K
Authors: Stephenson Clark C. , Wulff Claus A. , Lundell O. Robert
Published: January 2005

Heat capacities of cubic and hexagonal ammonium hexafluosilicate were measured between 25° and 300°K. The hexagonal heat capacity showed an anomaly at 38.6°K with an entropy of transition of R ln2. This was attributed to an order—disorder reorientation of the anion. These heat-capacity measurements, when combined with heat of solution measurements, gave a third-law verification with ΔS0°=0.03±0.2 cal deg—1 mole—1 for the change in state (NH4)2SiF6(hex)=(NH4)2SiF6(cub). The heat capacities were analyzed to determine the motions of the ammonium ions in the two polymorphs. These analyses showed that the ammonium ions in the cubic modification are undergoing torsional oscillation with a frequency of 235 cm—1, and that the ammonium ions in the hexagonal modification are undergoing pseudofree three-dimensional rotation at room temperature. The thermodynamic functions CP, S°, (H° — E0°)/T, and — (F° — E0°)/T were calculated. The values, in cal deg—1 mole—1 at 298.15°K are: 59.25, 67.99, 35.21, 32.78 for the cubic modification, and 54.52, 66.98, 33.93, 33.05 for the hexagonal. The entropy of the aqueous hexafluosilicate ion was determined to be 30.3±3 cal deg—1 mole—1.
Cell Model for Quantum Fluids. I
Authors: Henderson Douglas , Reed Robert D.
Published: January 2005

The cell model of Lennard-Jones and Devonshire is modified to include quantum effects. The energy levels are calculated by means of the WKB method with the effects of the first three shells of neighbors taken into account. The thermodynamic properties of hydrogen, deuterium, and tritium are calculated for the reduced volume v*=5/3.
Infrared Spectrum of Carbon Dioxide, Enriched in Oxygen-18
Authors: Berney Charles V. , Eggers David F.
Published: January 2005

The infrared spectrum of a sample of carbon dioxide enriched to about 10 at. % with O18 was examined in the region 1620–5400 cm—1, using an Ebert grating spectrometer with spectral slitwidths ranging from 0.2 to 0.4 cm—1. Ten previously unreported bands were analyzed and assigned to various species of O18 substituted carbon dioxide and Courtoy's results for C12O16O18 in the 2-μ region were confirmed. Courtoy's unexpectedly high value for the Fermi resonance constant of this species was confirmed by the separation of previously unreported Fermi-resonant bands. The positions of the two bands assigned to C12O182 suggest that the resonance constant for this species is larger still. A resonance interaction was found in C12O16O18, dependent on the potential constant k113.
On the Structure of the Three-Particle Scattering Operator in Generalized Boltzmann Equation for Homogeneous Gases
Authors: Stecki J.
Published: January 2005

It is shown that the weak-coupling version of Bogolyoubov theory in a form recently derived leads to a three-particle term in the equation of evolution of the velocity distribution function, in which the finite duration of collisions is taken into account in a way strictly equivalent to the Prigogine theory in the Markovian approximation.
Electron Spectrometer for the Study of Inelastic Electronic Collision Cross Sections
Authors: Lassettre E. N. , Berman A. S. , Silverman S. M. , Krasnow M. E.
Published: January 2005

An apparatus for the study of inelastic electronic collision cross sections of molecules as a function of scattering angle is described. The accuracy of excitation potential and collision cross section measurements is illustrated by means of examples involving helium, carbon monoxide, and oxygen.
Inelastic Scattering of Electrons by Helium
Authors: Lassettre E. N. , Krasnow M. E. , Silverman S.
Published: January 2005

Electron collision cross sections as a function of scattering angle are reported for four transitions in helium including one at the ionization limit. Incident electrons of kinetic energy 511 V are employed.
Integrated Intensity Measurements of the 1.9-μ Bands of CO2 in the Temperature Range 1400° to 2500°K
Authors: Breeze J. C. , Ferriso C. C.
Published: January 2005

Measurements have been made of the total integrated band intensity of the 1.9-μ bands of CO2 in the temperature range 1400° to 2500°K. The gas was heated to the high temperature by a shock wave reflected from the rigid end plate of a shock tube. The experiment determines the total integrated band emission as a function of optical path length. The total emission is related to the integrated band intensity in a simple way.

The intensity in the 1.9-μ region of the CO2 spectrum arises from three combination bands, namely the (v3+4v2), (v3+2v2+v1), and (v3+2v1) bands. These band systems are in strong Fermi resonance. The bands have not been resolved; the total integrated intensity of the three bands was measured as a function of temperature. The temperature dependence of the absolute intensity is discussed in terms of a simple model using the harmonic oscillator approximation to the CO2 molecule. The results indicate that the intensity in the 1.9-μ resonant triplet of CO2 originates in the (v3+2v1) band. An extrapolation of the data using the derived temperature dependence gives an integrated band intensity of 2.07 (cm—2 atm—1) at STP for the total 1.9-μ CO2 band.
Spectroscopy of Carbon Vapor Condensed in Rare-Gas Matrices at 4° and 20°K. I
Authors: Weltner W. , Walsh P. N. , Angell C. L.
Published: January 2005

The molecules vaporizing from graphite at 2300° to 2600°K have been trapped in neon, argon, and xenon matrices at 4° and 20°K. The near-ultraviolet bands of C3, beginning at 4050 Å in the gas, have been observed in the absorption spectra of these matrices but shifted to 4057 Å in neon, 4102 Å in argon, and 4226 Å in xenon. The neon spectrum is strikingly similar to low-temperature gaseous spectra, including cometary spectra, but the matrix bands occur in groups about 100 cm—1 wide. The infrared spectrum yields a strong band at 2038 cm—1 in argon (2042 cm—1 in neon) which is assigned to v3″, the asymmetric stretching frequency of C3 in the ground electronic state. When the argon matrix is allowed to warm up, diffusion occurs, and larger carbon molecules, C4, C5, C6, etc., are formed, causing the appearance of many new bands in the infrared. The Swan bands of C2 are observed in neon and argon matrices, but only after some annealing of the matrix has occurred by warming. The vibrational frequency of C2 in the excited 3Πu state in a neon matrix is 2094 cm—1, exceeding the value found in any other matrix or in the gas (1750 cm—1). The possible appearance of C2 in its 1Σg+ ground state in neon and argon matrices is briefly discussed.
Optically Active Lattice Vibrations of Zinc Blende Type and Wurtzite Type Crystals
Authors: Tsuboi Masamichi
Published: January 2005

Normal coordinate treatment has been made of the optically active lattice vibrations of zinc-blende-type and wurtzite-type crystals. Based upon the results of this treatment and upon the observed lattice frequencies, discussions are given on the force constants of cubic and hexagonal silicon carbides, zinc blende, wurtzite, and a few other crystals having the same type of crystal structure with either one of the above two. The hydrogen-bond stretching force constant in hexagonal ice whose crystal structure is similar to that of wurtzite has been estimated to be 0.18 mdyn/%Aring;.
Al27 Quadrupole Coupling in Solid AlCl3
Authors: Casabella P. A. , Miller N. C.
Published: January 2005

The nuclear quadrupole coupling constant of Al27 in solid anhydrous AlCl3 was found to be 472±24 kc/sec with an electric field gradient asymmetry parameter of zero. Assuming the crystal to be completely ionic, the electric field gradient was calculated for the layered AlCl3 structure by summing the contributions of the near ions, and treating the rest of the crystal as being made up of uniformly charged planes. This calculation gives an Al27 quadrupole coupling constant of —2.78 Mc/sec and an electric field gradient asymmetry parameter of zero. The addition of some covalent bonding tends to reduce the magnitude of the coupling constant and bring it into better agreement with the experimental value. It is estimated that the crystal is two-thirds ionic and one-third covalent.
Role of Benzene in the Radiolysis of Cyclohexane—Benzene Mixtures
Authors: Burr J. G. , Goodspeed F. C.
Published: January 2005

Benzene consumption, G(-benzene), has been measured in irradiated cyclohexane solutions containing 1%, 5%, and 10% benzene as a function of dose from 8×1020—80×1020 eV/g. G(-benzene) is found to decrease with increasing dose and to be approximately proportional to the square root of the initial benzene concentration. The composition of the polymer and dimer fractions obtained in the radiolysis of cyclohexane-5%—benzene-C14 mixtures shows that 25% of the consumed benzene appears as phenylcyclohexane and the rest as polymer. The magnitude of the G(-benzene) values suggests that radical scavenging by benzene is significant, although not the most important interaction.
Interaction Potential of the Inert Gases. I
Authors: Munn R. J.
Published: January 2005

The shape of the interaction potential of the inert gases is reconsidered using experimental second virial coefficient data. The potential is represented by an expansion containing four adjustable constants which may be used to reproduce a variety of potential shapes. The experimental and theoretical second virial coefficients are compared using the principle of corresponding states and the Boyle point properties. It is shown that second virial coefficient data alone cannot determine the potential; by making an assumption concerning the absolute separation at the argon potential minimum, however, the over-all shape of the potential can be quite closely defined. The possible potentials are then shown to have a number of features in common with the potential proposed by Guggenheim and McGlashan; they differ considerably from the usual 6–12 form. The various quantal calculations of the London attractive coefficient are also discussed.
Mass Spectrometric Studies of Reactions in Flames. I. Beam Formation and Mass Dependence in Sampling 1-Atm Gases
Authors: Greene Frank T. , Brewer Jerome , Milne Thomas A.
Published: January 2005

The pertinence of the Kantrowitz and Grey theory of aerodynamic molecular beams to the problem of sampling high-pressure systems with a mass spectrometer is discussed. A simple differentially pumped molecular beam system is described, which gives molecular beams of intensities of about 1017 molecules/cm2/sec from 1-atm sources. The behavior of this sampling system with pure gases, mixtures, and reactive systems is presented. In beams from gaseous mixtures the mass spectrometer gives a response which depends on the first power of the component molecular weight: Ix+=kPxmx.
Thermal Decomposition of Some Tert-Butyl Compounds at Elevated Temperatures
Authors: Tsang Wing
Published: January 2005

A single-pulse shock tube has been used to study the kinetics of the thermal decomposition of tert-butyl chloride, bromide, alcohol, and mercaptan. The results are compared with those obtained by earlier workers who used static reaction vessels at lower temperatures. The rate constants for the unimolecular elimination reactions are kC4H9Cl=1013.9e−46 200/RT(750∘−950∘K),kC4H9Br=1013.5e−41 500/RT(700∘−900∘K),kC4H9OH=1013.4e−61 600/RT(1050∘−1300∘K),kC4H9SH=1013.3e−55 000/RT(950∘−1230∘K).The results for the chloride and the bromide are in good agreement with those of other workers. The slight discrepancies that are present indicate that in the present work, in the temperature range 700°—950°K, the true reaction temperature behind the reflected shock is 10°—25°K lower than that computed in the usual manner.