bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shock Waves in Chemical Kinetics: Further Studies on the Rate of Dissociation of Molecular Iodine
Authors: Britton Doyle , Davidson Norman , Gehman William , Schott Garry 
Published: January 2005

The rate of the dissociation reaction, M+I2[open phi] lim kRkDM+I+I,has been measured by the shock tube method for argon, helium, nitrogen, oxygen, and carbon dioxide as inert gases, M, in the temperature range 1000°—1600°K. The shock wave results by themselves and the comparison of the shock wave measurements with the room temperature measurements of kR by flash photolysis both show that kR has a negative temperature coefficient. The absolute value of this negative temperature coefficient derived from the shock wave measurements is greater than the value derived from comparison of the average high temperature result with the room temperature result for any particular gas. This may be due to experimental error in the determination of dkR/dT at the high temperatures, but it is believed that the values of kR determined in the middle of the temperature range studied are reliable.
The experimental evidence indicates that, for the measurements with CO2, the rate of vibrational equilibration is so fast that the observations made here pertain entirely to vibrationally equilibrated CO2. Evidence from other experiments indicates that the rate of vibrational relaxation in oxygen is such that most of the dissociation reaction occurs in relaxed O2, but that nitrogen remains vibrationally unexcited under the conditions of the dissociation reactions studied here.
The ratio, kR, 12/kR,A, of the efficiencies of iodine and argon as third bodies is not greater than 30 at 1300°K whereas it is 250–600 at room temperature. The hypothesis is proposed that in general the ratio kR, gas/kR,A for complex gases will decrease with increasing temperature.
Shock Waves in Chemical Kinetics. Rate of Dissociation of Molecular Bromine
Authors: Britton Doyle , Davidson Norman 
Published: January 2005

The rate of dissociation of molecular bromine in argon-bromine mixtures has been measured in a shock tube and the rate constants for the reaction Br+Br+M→ lim kRBr2+M, in the temperature range 1400°—2700°K, computed. The data are not sufficiently accurate to reveal the temperature coefficient of kR. However, comparison of the average high temperature result, kR=3.4×108 liter2 mole—2 sec—1 at 1600°K, with the room temperature flash lamp result, kR=2.5×109, shows clearly that dkR/dT is negative. Experiments were performed with bromine: argon ratios of 0.01 to 0.10; the efficiency of Br2 as M, the third body for the recombination of bromine atoms, is not greater than 8 times that of argon. The agreement of the results of this investigation with those of an independent shock tube investigation by Palmer and Hornig is gratifyingly good.
The extinction coefficients of bromine at 436 mμ and 487 mμ were measured as a function of temperature.
Gaseous Detonations. IX. A Study of the Reaction Zone by Gas Density Measurements
Authors: Kistiakowsky G. B. , Kydd P. H. 
Published: January 2005

An x-ray absorption photometer capable of measuring gas densities with extreme rapidity and reasonable accuracy has been developed to study the reaction zone in detonation waves. At low initial gas pressures this zone is readily observable as a density peak at the wave front lasting a few μsec.
In general the results agree with the hydrodynamic theory of the detonation wave. The observed densities at the end of the reaction zone (the Chapman-Jouguet state) compare well with the results of approximate equilibrium calculations and the observed shape of the density profile qualitatively confirms kinetic predictions. However, the observed peak densities are substantially lower than expected and the initial chemical reaction rates are faster. The most plausible explanation at present seems to be a lack of equilibration between translational and internal degrees of freedom in the shocked gas, lasting long enough for a substantial progress of the chemical reactions to take place.
The duration of the reaction zone in the mixtures studied is inversely proportional to the initial pressure of the detonating gas. This is true of the stoichiometric mixtures of hydrogen and oxygen which were studied most intensively. On varying the composition of these mixtures it is found that the duration is inversely proportional to the partial pressure of hydrogen and is independent of that of oxygen. An increase of the total pressure by the addition of a rare gas accelerates the reaction. Nitrogen and water vapor act as inert additives.
Replacement of some hydrogen by carbon monoxide does not alter the duration of the reaction zone. On the other hand, when small quantities of hydrogen are added to stoichiometric carbon monoxide-oxygen mixtures, the reaction times are found to vary as PH2—½. The addition of nitrogen has little effect on these mixtures but carbon dioxide proves to be a strong inhibitor.
Methane reacts with oxygen at a rate which is comparable with that observed for hydrogen, while acetylene oxidation is very much faster.
Theory of Rotational-Vibrational Interaction in Polyatomic Molecules
Authors: Bodi Lewis J. , Curtiss C. F. 
Published: January 2005

Group theoretical considerations show that an eigenfunction of the Schroedinger equation for a polyatomic molecule may be written as a sum of products of representation coefficients of the group of three-dimensional rotations and functions which depend only upon the relative configuration of the atoms and hence only upon the normal coordinates. A perturbation solution of the Schroedinger equation is described which is based on zero-order wave functions which are consistent with this group theoretical result. All of the angular momentum operators appearing in the wave equation are shown to be recursion operators in the representation coefficients. Subsequent utilization of the orthogonality of the representation coefficients then leads to a set of coupled differential equations for the functions which depend only on the normal coordinates. This set of coupled differential equations is a generalization of the matrix equations for the rotational motion of a rigid body.
The functions of the normal coordinates are then expanded as sums of products of Hermite functions of the individual normal coordinates. Use of the orthogonality relations of the Hermite functions then yields a set of equations for the expansion coefficients. The eigenvalues of the associated matrix are then, of course, the exact rotational-vibrational energy levels of the polyatomic molecule. These energy levels are obtained approximately by a diagonalization in the rotational quantum numbers followed by a perturbation technique in which the coupling between vibrational levels is assumed to be small (except in the case of degeneracy). The lowest approximation to the energy levels contains terms which may be interpreted as due to coupling effects which in previous solutions appear only in higher order approximations.
Energy Levels of the Coaxial Internal Rotator with Rectangular Potential Function
Authors: Halford J. O. , Vidale G. L. 
Published: January 2005

For the coaxial internal rotator with rectangular potential function and freely variable valley breadth at constant periodicity, conditions are specified for an infinite number of points at which the borders of consecutive bands of energy levels must be exactly degenerate. As the valley breadth is changed through a degeneracy, the level of one symmetry relative to the potential function moves from the upper to the lower band of energy levels, or vice versa.
It follows that in the rotational region above the potential maximum the levels at the band limits can repeatedly cross and re-cross when the potential maximum is increased with all other factors constant.
Similar behavior will presumably occur with other potential functions.
Calculation of Compressibilities of High Polymers from the Energy of Interaction between Chain Groups
Authors: Brandt Werner 
Published: January 2005

A potential function for the interaction of long chain molecules in polymer lattices is formulated. The adopted model assumes polymeric substances to consist of imperfect assemblies of perfect chain crystals. The chains are infinitely long compared to the range of intermolecular forces so that end effects can be neglected. Each chain is composed of evenly spaced dipolar dispersion force centers, with dipole orientations perpendicular to and alternating along the chain axes. Pairs of force centers in neighboring chains interact according to a Lennard-Jones (12–6) potential and the electrostatic interaction terms. The interaction between neighboring force centers within a chain is assumed to be Hookian with a force constant calculated from combined valence bond distortions and valence angle deformations.
The lattice energies of five linear polymers are calculated. It is found that the contributions from induction terms are negligible. The contributions from dipole interaction terms depend on the mutual orientation of the chains and amount to only ca 0.1–1% of the lattice energies. To this accuracy, certain ``structure insensitive'' properties can be described by an equation of corresponding intermolecular states. This approach is shown to fail, if applied to ``structure sensitive'' properties, which depend strongly on the interplay of inter- and intramolecular degrees of freedom. Absolute calculations of specific polymer volumes over large pressure ranges are in agreement with experiment.
Lifetime Measurements of Metastable States in Molecular Nitrogen
Authors: Lichten William 
Published: January 2005

The molecular beam method for the measurement of the lifetime of metastable states has been improved by the introduction of differential pumping, control of the energy of the bombarding electrons, and use of a movable detector.
A lower limit of 10—2 sec is obtained for the lifetime of the A 3Σu+ state of N2, in closer agreement with spectroscopic observations than the previous work of Muschlitz and Goodman.
The measured value of the lifetime of the a 1IIg state of N2 is (1.7±0.3)×10—4 sec.
Some new observations on metastable states of the rare gas atoms, A, Kr, and Xe; CO and H2 are mentioned briefly.
Reaction Products of γ Picoline and Iodine
Authors: Glusker Donald L. , Miller Arthur 
Published: January 2005

From the reaction products of γ picoline and iodine two distinct addition compounds have been isolated and studied by chemical, spectroscopic, and x-ray radial distribution methods. The second of these compounds to be isolated is an intermediate in the formation of the first, and is analogous to the addition compound of pyridine and iodine prepared by many workers. The x-ray radial distribution analysis of the first compound showed that the covalent bond in the iodine molecule had been broken, and the corresponding analysis of the second compound showed that the covalent bond was still present. A mechanism has been postulated for the reaction of the second compound with excess γ picoline to form the first compound.
The applicability of the Geiger counter x-ray diffractometer to the radial distribution method is discussed, and the theory for the radial distribution analysis of diffraction data consisting of discrete peaks is presented.
C13-Isotope Effect in the Photolysis of Ethyl Bromide
Authors: Friedman H. L. , Bernstein R. B. , Gunning H. E. 
Published: January 2005

The photolysis of ethyl bromide in a tenfold excess of cyclopentane has been studied over the temperature range, 30 to 250°C.
Ethane is the principal volatile product of reaction. The quantum yield of ethane formation has been found to be unity at 30°C. An increase in apparent quantum yield to 1.5 at 250°C was observed. This increase is attributed to the greater absorption of the incident radiation at high temperatures.
The C12 enrichment in the ethane product was 1.0070±0.0008, and invariant in temperature. The isotope fractionation effect is explained on the basis of the higher absorption of C12–C12–Br over C12–C13–Br in the long wavelength region.
Infrared Spectra of the Alkali Halides. I. Lithium Halides
Authors: Klemperer William , Rice Stuart A. 
Published: January 2005

The infrared spectra of LiI, LiBr, and LiCl in the gas phase have been measured in the region of the fundamental vibration frequency. The vibrational frequencies are calculated from the observed spectra to be LiI  ωe=501 cm−1LiBr ωe=576 cm−1LiCl ωe=662 cm−1.There is no evidence in the spectra for the existence of appreciable quantities of dimeric molecules, the estimated dimer concentration being thus restricted to less than 15%.
The apparatus used appears suitable for absorption measurements above 2000°C.
Rotation-Vibration Spectra of Methyl Amine and Its Deuterium Derivatives
Authors: Gray Allan P. , Lord R. C. 
Published: January 2005

Methyl amine, methyl amine-d2, methyl-d3 amine and methyl-d3 amine-d2 of high chemical and isotopic purity have been synthesized and their infrared spectra studied at both prism and grating resolution. The rotation-vibration band centers of methyl amine have been measured with improved accuracy over previous investigations and with the aid of the spectra of the deuterium analogs a vibrational assignment differing in some important respects from those hitherto suggested has been made.
The grating spectra in some cases show irregularities in the rotational fine structure but none which can be associated with effects due to hindered internal rotation. Recent studies in the microwave region have shown that these effects should not be observed within the resolution limits of the grating spectrometers used in this work. However, the first overtone of the torsional frequency in methyl amine, methyl amine-d2 and methyl-d3 amine has been observed in a position consistent with calculations based on a barrier height of 690 cm-1.
The rotational structure of a number of unperturbed vibrational bands has been analyzed in terms of equations applicable to an approximate symmetric top and rotational constants have been obtained in good agreement with values calculated from parameters obtained from microwave investigations.
Dynamic Compression of Liquids from Measurements on Strong Shock Waves
Authors: Walsh John M. , Rice Melvin H. 
Published: January 2005

High explosives were used to drive strong shock waves into various liquids, and a moving-image camera was employed to determine velocities associated with the shock waves. The measured velocities are transformed to pressure-compression points by applying the conservation relations. The pressures attained vary among the 15 liquids studied but are typically in the range 50 kilobars to 150 kilobars. For water, more extensive experimentation suffices to determine the Hugoniot curve from 30 kilobars to 450 kilobars. The highest pressure for each of the liquids extends the available data range from static experimentation several fold.
A shock-wave-reflection experimental method is described, the purpose of which is to measure the useful thermodynamic variable (ΔH/ΔV)P at high pressures. Results are given for water.
Qualitative experiments to study the transparency of shocked water, carbon tetrachloride, ethyl alcohol, and benzene are reported.
Partition Function for Internal Rotation in Methanol and Similar Molecular Models
Authors: Halford J. O. 
Published: January 2005

Methanol falls outside the range of variables within which the internal rotator partition function and its required derivatives have been dependably calculated by the relatively simple methods of Pitzer and Gwinn. For such cases, Ivash, Li, and Pitzer have proposed a detailed, general formulation of potential extreme accuracy.
It is shown here that their partition function, obtained by integration over functions which are not unique for the model, can have two formally different values. Elimination of an ambiguity from their derivation leads back to an earlier and simpler method developed empirically by Halford, without, however, establishing this method for the general case.
A very simple derivation, which obviously gives answers of readily determined accuracy for a widely distributed set of special cases, is presented. It is shown that the Ivash-Li-Pitzer formulation gives accurate answers under specifiable conditions. It is also deduced that a considerable extension of the Pitzer-Gwinn Tables, at a high level of accuracy, sufficient to cover all likely cases of interest, is possible without serious increase in the detail of calculation.
Such an extension would solve the general case in a practical sense.
Crystal and Molecular Structures of Heterocyclic Compounds. III. α-Phenazine near 80°K
Authors: Hirshfeld F. L. , Schmidt G. M. J. 
Published: January 2005

A partial three-dimensional analysis of the crystal structure of α-phenazine at the temperature of boiling nitrogen has yielded, after refinement by a weighted least-squares procedure, carbon and nitrogen coordinates accurate to 0.003 A as well as approximate hydrogen positions. Within the experimental error, the C–C bond lengths are identical with those in anthracene. This agrees with theoretical predictions, for direct molecular-orbital calculations, with allowance for overlap of adjacent atomic orbitals, indicate a maximum difference between corresponding C–C bond lengths in phenazine and anthracene of about 0.01 A, which is of the order of the error in the latter structure. The results imply that neither inductive effects due to chemical substitution nor crystal forces can have any great influence on bond lengths in an alternant hydrocarbon such as anthracene.
The C–H bond lengths average 1.00 A but are not to be compared with direct measurements of the internuclear distance such as are given by electron-diffraction or magnetic-resonance data.
Deviations from molecular symmetry mmm exceed the experimental error only in the direction normal to the mean molecular plane. These displacements from the plane are of the order of 0.01 A and appear to arise from an electrostatic attraction between overlapping atoms in adjacent parallel molecules. Electrostatic interaction, however, is probably not important in determining the type of crystal packing, for a survey of other aromatic structures indicates that the packing type is, in most instances, approximately independent of electrostatic forces.
Interaction between Sulfur Dioxide and Polar Molecules. II. Systems Containing Ethanol, and Benzene or Hydroquinone
Authors: de Maine P. A. D. 
Published: January 2005

The near ultraviolet absorption for sulfur dioxide in benzene-ethanol solvent is adequately explained as arising from the superimposed bands for the systems: EtOH+SO2[open phi] lim K1(complex)1;  Benzene+SO2[open phi] lim K2(complex)2,if it is assumed that in passing from nonpolar to polar solvents there is no change in K1, K2, and in the molar extinction coefficients of the two complexes and of the uncombined sulfur dioxide. Extinction coefficients and equilibrium constants for the benzene complex must be obtained from analysis of solutions with high benzene concentration. It was found that the thermodynamic constants of both complexes, calculated from data for the mixed system, are identical with values obtained for the separate systems with carbon tetrachloride.
A similar analysis of the absorption spectra of hydroquinone-sulfur dioxide-ethanol solutions gives a value of 14.0±1.0 kcal per mole for the heat of formation of the hydroquinone-sulfur dioxide complex in ethanol. The heat of decomposition of the solid hydroquinone-sulfur dioxide clathrate compound was found, by Wynne-Jones and Anderson, to be 14.2±0.1 kcal. These results demonstrate the importance of lattices in polar solvents.
Iodine Complexes in Inert Solvents. II. Complexes of Iodine with Some Aromatic Ethers and Biphenyl in Carbon Tetrachloride
Authors: de Maine P. A. D. 
Published: January 2005

Characteristic constants and absorption spectra are given for anisole, p-dimethoxy-benzene, o- and p-methoxy-biphenyl, and biphenyl complexes with iodine, as determined in carbon tetrachloride solution near room temperature. Three absorption maxima are found for the anisole-iodine complex: at 4900 A, 3450 A, and 2950 A. The band near 4900 A is attributed to a modified iodine transition, while the two ultraviolet bands are attributed to the formation of two isomeric charge-transfer complexes. The two non-degenerate anisole donor orbitals, with different ionization potentials, are supposed to correspond to the degenerate pair of benzene e1g molecular orbitals. The ultraviolet absorption spectra found for the other iodine complexes are interpreted similarly.
A method for estimating the two equilibrium constants and the two extinction curves for such complexes, having isomeric forms, is suggested.
Iodine Complexes in Inert Solvents. III. Iodine Complexes with Methanol, Ethanol, or Diethyl Ether in Carbon Tetrachloride
Authors: de Maine P. A. D. 
Published: January 2005

Thermodynamic and spectroscopic constants, obtained by a spectrophotometric method, are reported for complexes of methanol, ethanol, and diethyl ether with iodine in carbon tetrachloride. It is shown that the heats of formation of the complexes are nearly identical with values obtained by a nonspectroscopic method.
From the spectroscopic and nonspectroscopic data for solutions of methanol, ethanol, and diethyl ether with iodine or with iodine and carbon tetrachloride, it is concluded that the activity coefficients for the iodine and the alcohols are independent of their concentrations and that in these cases the alcohols do not solvate the complexes even at concentrations of nearly one hundred percent alcohol.
Exact molar extinction coefficients for iodine in n-heptane and in carbon tetrachloride are given in Table I, and related data in Fig. 2.
There is a detailed discussion of errors due to the neglect of temperature effects, underlying bands, and volume changes on mixing the solvents. Evidence in support of ``Liquid Lattice Penetration Complex'' theory, in which it is assumed that the stabilizing forces arise from ``donor-acceptor'' interaction, is also discussed.
It is found that Andrews and Keefer's linear relations between ΔF and ΔH or ΔS, for the aromatic complexes of iodine, do not hold for all iodine complexes.
Microwave Spectrum, Dipole Moment, and Structure of Difluorosilane
Authors: Laurie Victor W. 
Published: January 2005

The microwave spectra of several isotopic species of difluorosilane, SiH2F2, have been investigated in the region from 12 000 to 38 000 mc. Rotational constants have been determined and the following structural parameters calculated for SiH2F2: rSiH=1.471±0.007 A, rSiF=1.5767±0.001 A, ∠HSiH=112°1′±30′, ∠FSiF=107°56′±6′. An independent determination of the structure of SiD2F2 was also carried out with the following results: rSiD=1.469±0.010 A, rSiF=1.5764±0.001 A, ∠DSiD=113°11′±45′, ∠FSiF=107°57′±10′. Rotational constants for the vibrationally excited state ν4 have been determined for both SiH2F2 and SiD2F2, and certain structural parameters determined. The variation of effective structure upon isotopic substitution is discussed.
Measurements on the Stark effect of the ground vibrational state of SiH2F2 give a value of 1.54±0.02D for the dipole moment. Values for the excited state v4=1 and for SiD2F2 were also measured and agree within the experimental error with the SiH2F2 ground-state value.