bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass-Spectrometric Study of the Reaction of Atomic Hydrogen with Acetaldehyde
Authors: McKnight Charles , Niki H. , Weinstock Bernard 
Published: January 2005

The reaction of atomic hydrogen with acetaldehyde has been studied with a discharge-flow system coupled to a time-of-flight mass spectrometer. The results are consistent with the mechanism Primary step: CH3CHO+H→CH3CO+H2;Secondary steps: CH3CO+H→CH2CO+H2,CH2CO+H→CH3CO*→CH3+CO,and CH3+H→ lim wallCH4.
The rate constant for the abstraction of the aldehydic hydrogen in the primary step (1) for the isotopic modification CD3CDO+D has been determined directly to be 3.2±0.5×10−14 cc molecule−1·sec−1 at 300°K. Under the conditions studied, the major reaction of the acetyl radical is its further reaction with hydrogen atoms to form ketene (6). The final carbon containing products, CO and CH4, are formed from subsequent reactions of ketene with hydrogen atoms (10). The kinetic behavior of the products, CH2CO and CH4, confirms the role of ketene as a major intermediate species in this system. Isotopic studies further confirm that methane is formed from a reaction sequence of ketene with H atoms. The above mechanism is compatible with previous studies of this system, with the exception of a recent communication by Lambert, Christie, and Linnett (Chem. Commun. 1967, 338), who suggest a primary step that yields methane and the formyl radical, CHO, rather than Reaction (1).
Microwave Studies of Collision-Induced Transitions between Rotational Levels. II. Observations in H2CO, HCN, and H2CCO
Authors: Oka Takeshi 
Published: January 2005

The technique of high-power microwave double resonance is applied to study collision-induced transitions between rotational levels in H2CO, HDCO, HCN, DCN, and H2CCO. The K-type doublets (or l-type doublets) of these molecules for selected J levels have been ``pumped'' by high-power microwave radiation and the decreases in the intensities of the absorption lines of K-type doublets (or l-type doublets) of other J levels have been observed. The ``preferred'' collision-induced transitions previously observed for ethylene oxide have been more strikingly confirmed. Also multiple transitions with ΔJ≥2 have been observed. An approach by the use of steady-state equations is developed and used for the analysis of the observed results. Relative values of the rate constants for various collision processes (such as the ΔJ=1 collision-induced transitions versus the ΔJ=0 collision-induced transitions or collision-induced transitions with dipole selection rules vs collision-induced transitions with quadrupole-type selection rules) have been determined. The analysis has led to the following conclusions.
(1) The collision-induced transitions follow selection rules. For the molecules studied in this paper, the dipole selection rules (ΔJ=0, ±1, parity +↔—) are dominant although not always by a very large factor [see Conclusion (3) below].
(2) The rate constants for the collision-induced transitions with ΔJ=1 are of the same order of magnitude as those with ΔJ=0, although, molecules make transitions between more widely spaced energy levels in the former case. This result is evidence which supports the idea of ``rotational resonance'' introduced by Anderson for explaining the pressure broadening of ammonia.
(3) For HCN, DCN, and H2CCO, rather large rate constants have been obtained for the ΔJ=2 transitions. This suggests that the collision-induced transitions with quadrupole-type selection rules or possibly those with even higher multipole-type selection rules also play a role in these molecules.
Antiferromagnetic and Crystal Structures of Alpha-Oxygen
Authors: Barrett C. S. , Meyer L. , Wasserman J. 
Published: January 2005

X-ray diffractometer data from polycrystalline samples of alpha-oxygen frozen from the liquid are accounted for by a monoclinic structure: space group C2/m, b axis unique, a = 5.403±0.005, b = 3.429±0.003, c = 5.086±0.005 Å; β = 132.53±0.04°; volume = 69.44 Å3; calculated density = 1.530 g/cm3. The cell contains two molecules centered at the lattice points 000 and ½½0, which are symmetry centers. The atoms are at positions x, 0, z; x̄, 0, z̄; ½+x, ½, z; ½—x, ½, z̄, with x = 0.089±0.01, z=0.153±0.015. The nearest center-to-center distances between molecules is 3.20 Å and the 0–0 bonds are found to be perpendicular to the ab plane within an experimental accuracy of a few degrees.
The published neutron diffraction data, interpreted on the basis of the structure, imply that the antiferromagnetic structure consists of antiparallel moments at 000 and ½½0.
Vibration Frequencies of NO2− and NO3− Ions in KBr Crystals
Authors: Kato R. , Rolfe J. 
Published: January 2005

Infrared-absorption spectra of doped KBr crystals at temperatures of approximately 8°K were measured in the wavelength range 2 to 15 μ. From the absorption spectra of crystals doped with NO2− and NO3− ions, and with ions enriched in the isotopes 15N and 18O, frequencies of normal vibrations of six isotopic NO2− molecules, and eight isotopic NO2− molecules were determined. These frequency values were used to calculate a set of force constants for NO2− and NO3− ions in the KBr lattice, using the most general harmonic force field (GFF). In mdyn/Å units, values obtained for NO2− were: fr=7.50, frr=1.66, frα=0.39, fα=1.67, and for NO3−: fr=7.62, frr=1.43, (fα—fαα)=1.09, (frα—frα′)=−0 .48, fγ=1.506.
In crystals doped with divalent metal ions as well as NO2− and NO3− ions, new absorption bands appeared. These were perturbations of the vibrational frequencies of NO2− and NO3− ions, caused by association between divalent metal ions and NO2− and NO3− ions. In the case of NO3−, the doubly degenerate asymmetric stretching band was split into two nondegenerate bands by the perturbation, which is thus almost certainly caused by a nearest-neighbor association between metal and nitrate ions. While the other frequency shifts of nondegenerate vibrations can give no information about the symmetry of the surrounding lattice, they can also be explained by a nearest-neighbor interaction between divalent metal and NO2− and NO3 ions.
Paramagnetic Relaxation of Triplet Molecules Randomly Oriented in a Rigid-Glass Matrix
Authors: Brown I. M. , Sloop D. J. 
Published: January 2005

Investigations have been made of the paramagnetic relaxation of the triplet molecules zinc 2,2′-biquinoline randomly oriented in a rigid-glass matrix of 2-methyltetrahydrofuran. The saturation and relaxation behavior of these molecules is qualitatively consistent with the inhomogeneous nature of the ΔM=1 line-shape. The relaxation times are such that a hole burned in the line can recover by spin—lattice relaxation and by cross relaxation to adjacent spin packets. The temperature dependence of the spin—lattice relaxation time is given by T1−1=1.37×105 exp(−22/T)+2.94T2.
We interpret the exponential as indicating an Orbach process between the ground-state triplet and the first excited singlet. The Orbach exponent implies that the triplet—singlet separation, which is determined by the value of the intramolecular exchange integral, is 15.5±1 cm−1. An expression for T1 similar to that derived by Scott and Jeffries has been used to identify the dominant interaction participating in this process. From crude estimates of the spin-vibronic matrix elements it seems unlikely that this interaction is large enough to account for the experimental value of T1=1.3 msec at 4.2°K. The only interactions which are large enough to explain this value are second-order vibronic effects which involve singlet—triplet mixing through static spin—orbit coupling. At this time we can offer no explanation of the T2 dependence which predominates below 2°K.
Theory of Diffusion-Controlled Processes. II. Consideration of Conceptual Framework
Authors: Yguerabide Juan 
Published: January 2005

The fundamental concepts and equations used in describing diffusion-controlled processes in liquids are defined and analyzed in terms of the behavior of an ensemble of reacting molecules. Rate equations are derived and written in forms familiar in reaction kinetics. The physical meaning of the various forms of these equations is discussed in terms of a priori and a posteriori probabilities. The probabilistic equations are also expressed in terms of particle concentrations; the measurables of experiments, in reaction kinetics. The final equations constitute the correct formal description of the reaction of molecules in liquids under conditions explicitly specified.
The results derived here are compared with those of a previous paper in which the macroscopic behavior of a system of reacting molecules is expressed in the form of a power series derived from consideration of molecular diffusion and microscopic molecular distribution. It is shown that the fundamental rate equation previously used is only approximately correct and that higher-order terms of the power series arise from the approximate nature of the rate equation.
Scintillation Studies of Organic Compounds in a Supercooled Molten State
Authors: Horrocks Donald L. , Wirth Hermann O. 
Published: January 2005

When the crystals (obtained by crystallization from certain solvents) of a number of low-molecular-weight organic compounds (11 derivatives of 2-phenylindole and two derivatives of p-quaterphenyl) were melted and recooled to room temperature, rather stable nonrecrystallizing, supercooled melts were obtained. The consistency of these at room temperature varied from rather viscous oils to rigid glasslike masses. Their stability also varied over a wide range; from one day to at least several years.
The response of these amorphous, pure scintillators to excitation by energetic electrons was measured relative to a standard liquid scintillator solution (gas-free, 3-g/liter PPO—toluene solution) which was assigned a value of 100. The very stable (at least several years) and rather rigid melt of 12,23,32,43-tetramethyl-p-quaterphenyl exhibited a relative response of 92. The supercooled melt of N-isoamyl-3,2′-ethyleno-2-phenylindole showed a relative response of 125 and remained amorphous with a consistency at room temperature of a thick grease for greater than nine months if maintained under evacuated conditions.
The fluorescence spectra of these compounds in the undiluted, supercooled state and in a toluene solution (mole fraction of about 0.001) were measured for excitation by 315-mμ radiation. In some cases there were differences in the measured spectra depending on the type of sample.
40-kV Electron Scattering from Ne, Ar, Kr, and Xe Measured by the Sector-Microphotometer Electron-Diffraction Method
Authors: Bonham R. A. , Cox H. L. 
Published: January 2005

Experimental differential cross sections for 40-kV electrons scattered by Ne, Ar, Kr, and Xe were measured using the gas electron-diffraction sector-microphotometer method. Three different camera distances (11, 28, and 62 cm) were used to collect experimental intensity data over a range of the scattering variable s from s=0.9 to s=26.
The experimental-intensity curves were compared with theoretical-intensity curves where the elastic portion of the scattered intensity was calculated using both partial-wave and first Börn scattering amplitudes. Hartree—Fock inelastic scattering factors calculated by Tavard were used for the inelastic portion of the scattered intensity, as well as inelastic scattering factors calculated using the plane-wave approximation suggested by Liberman. In the case of Kr and Xe the agreement between the experimental and theoretical intensity curves was better when the partial-wave amplitudes were incorporated in the elastic portion of the intensity than when the first Börn amplitudes were used. In the case of Ne and Ar, the difference in the agreement using partial-wave and first Börn amplitudes was too small to be significant. The total electronic energies for the atoms studied were also estimated.
Kinetics of the Isotopic Exchange Reaction Between Carbon Monoxide and Carbon Dioxide
Authors: Brandner John D. , Urey Harold C. 
Published: January 2005

The rate of exchange of the C13 isotope between carbon monoxide and carbon dioxide has been studied. It has been found to be a surface catalyzed reaction on quartz, gold, and silver surfaces. Within the limits of experimental error, which are rather large because of change of surface activity, the reaction is independent of pressure and composition of the gas mixture. The exchange is accelerated by hydrogen or water vapor. Oxygen produces a rapid initial exchange attributed to a chain process of oxidation of carbon monoxide, but is without effect on the subsequent exchange. Isotope exchange takes place with a velocity convenient for study around 900°C, and at this temperature the apparent energy of activation is about 100 kcal.
Several mechanisms for the exchange of C13 have been examined. One which is not entirely free of difficulties accounts for the experimental data. This assumes the presence of H and OH molecules (or other activated forms of H2 and H2O) on the surface with the condition that the total amounts of these molecules is constant.
Experimental Determination of the Field Gradient at the Deuteron in Formaldehyde
Authors: Flygare W. H. 
Published: January 2005

A high-resolution microwave spectrograph has been constructed to observe small perturbations in rotational energy levels. High-resolution spectroscopy on OCD2 yielded the following values of the quadrupole coupling constants in the OCD2 principal inertial axis system: χaa = —13±4 kc/sec, χbb = 98±4 kc/sec, and χcc = —85±4 kc/sec. The spin—rotation coupling constants in OCD2 were calculated from the values for the proton obtained from the beam-maser spectroscopy on OCH2. Data on the 212→211 transition in OCHD is then analyzed yielding the following coupling constants in the OCHD principal inertial axis system: χa′a′ = 9±2 kc/sec, χb′b′ = 76±2 kc/sec, and χc′c′ = —85±2 kc/sec.
The above data show that the principal field-gradient axis system coincides with the bond axis system within experimental error. The principal field-gradient components all in units of esu cm—3 are qαα (C–H bond axis) = 8.45×1014, qββ = —4.15×1014, and qγγ (perpendicular to molecular plane) = —4.30×1014.
Lattice Heat Capacity of Solid Hydrogen
Authors: Ahlers Guenter 
Published: January 2005

The lattice heat capacity of solid hydrogen was measured at zero pressure, and at three constant volumes. The measurements extend from 2°K to the triple point for the zero-pressure data, from 2°K to the melting temperature at 22.56 cc/mole, and from 4° to 20°K at 19.83 and 18.73 cc/mole. The Debye thetas at 0°K are 128°, 169°, and 189°K at 22.56, 19.83, and 18.73 cc/mole, respectively. The temperature dependences of the Debye thetas are similar to those for other simple solids.
Some information about other thermodynamic properties was obtained from the heat capacities. The isothermal compressibility at 16.35°K at the melting pressure is essentially the same as at 4.2°K at the same pressure. The thermal expansion coefficient at 82 atm appears to have a maximum at about 12°K. At zero pressure the thermal expansion coefficient is approximately proportional to the temperature. The thermodynamic expression for the Grüneisen relation is not obeyed in solid hydrogen.
Integrated Intensity Measurements of the 5.3-μ Fundamental and 2.7-μ Overtone Bands of NO between 1400° and 2400°K
Authors: Breeze J. C. , Ferriso C. C. 
Published: January 2005

Measurements have been made of the total integrated band intensities of the 5.3-μ fundamental and the 2.7-μ first overtone bands of NO in the temperature range 1400° to 2400°K. The NO gas sample was studied at high temperatures using a reflected shock-wave technique.
Within the temperature range used in the present experiments, the integrated band intensity of the NO fundamental does not vary. However, the integrated intensity of the first overtone band of NO shows a small temperature dependence. The temperature dependencies of the two bands are in agreement with theoretical temperature dependencies determined assuming a harmonic oscillator approximation to the NO molecule. Using the theoretical temperature dependencies the experimental data have been extrapolated to give values of the integrated intensities α° at STP. The values of α° obtained for the fundamental and first overtone bands of NO are 76±7 cm—2·atm—1 and 2.8±0.5 cm—2·atm—1, respectively.
Ionization Potentials of Alkyl Free Radicals and of Benzene, Toluene, and Triethylamine by the RPD Technique
Authors: Melton Charles E. , Hamill W. H. 
Published: January 2005

A time-of-flight mass spectrometer with a source of effectively monoenergetic electrons has been utilized to determine the ionization potentials and ionization-efficiency curves of the stable compounds benzene, toluene, triethylamine and of the free radicals, methyl, ethyl, n-propyl, and isopropyl. The appearance potentials in electron volts observed for the stable compounds were C6H6: 9.20, 9.40, 9.65; C6H5CH3: 8.80, 9.20, 9.50; (C2H5)3N: 7.68, 8.18, 8.55, 8.95, 9.40. Published values for the appearance potentials by electron impact of these compounds tend to converge upon one of the higher values observed in this work.
The radicals were produced by thermal—catalytic decomposition of appropriate alkyl nitrites, isopropyl ether, and isobutane. Appearance potentials (electron volts) determined for the free radicals were as follows: methyl—9.80, 10.3, 10.7, 11.4; ethyl—8.25, 8.7, 9.3; n-propyl—8.15, 8.6, 8.8, 9.2, 9.6; isopropyl—7.52, 8.1, 8.6. The measured ionization potentials of methyl, ethyl, and propyl free radicals were considerably lower than published values by electron impact.
Molecular Motion in Solid HCl and DCl. Quadrupole Coupling in the Low-Temperature Phase
Authors: Marram E. P. , Ragle J. L. 
Published: January 2005

The 35Cl pure quadrupole spectra of HCl and DCl have been examined by pulse techniques between 50°K and the phase transformations at 98.36° and 105.03°K. In these materials, T1 is shorter than about 400 μsec above about 63° and 77°K, respectively, but shows behavior typical of a thermally activated rate process at lower temperatures. Activation energies for both compounds are 2.70±0.05 kcal/mole, in good agreement with values obtained from dielectric constant data. In HCl, T2, probably determined by the proton moment, is of the order of two to three times T2*, while in DCl T2 is 40 to 50 times T2* in the temperature range for which it is not controled by T1.
The data are discussed in terms of possible molecular motions in the solids in the low-temperature phase.
Motion of the H2O Molecule in Potassium Oxalate Monohydrate
Authors: McGrath J. W. , Paine A. A. 
Published: January 2005

The proton magnetic resonance doublet splitting was measured for potassium oxalate monohydrate in the range from 74° to 395°K. The equilibrium position of the proton—proton vector was always perpendicular to the magnetic field. The measurements were made for orientations of the crystal such that the H–O–H bisector was parallel or perpendicular to the field. The doublet splitting is virtually independent of the temperature up to 395°K. However, the H2O molecules is in zero-point vibration. The angular amplitudes of the torsional and rocking motions are about 11° and 10°, respectively.
The orientational potential energy of the H2O molecule appears to be made up of a hydrogen-bond component and an electrostatic component due to nearest potassium ion neighbors. A reasonable, nominal H-bond energy and a reasonable, simple charge model for the H2O molecule yielded computed torque constants of 28 and 36 kcal/mole for the torsional and rocking motions, respectively. The proton—proton separation is found to be 1.54 Å when the raw value is corrected for the effects of molecular vibration. The results favor the crystal structure given recently by Pedersen.
Line-Reversal Studies of the Sodium Excitation Process Behind Shock Waves in N2
Authors: Hurle I. R. 
Published: January 2005

Spectrum-line reversal measurements of the time variation of Na excitation temperatures behind shock waves in N2 over the range 1720°—4340°K are described. From a comparison of the results with recent interferometric and infrared measurements of N2 vibrational relaxation, made also behind shock waves, it is shown that the observed Na excitation temperature is identified with the vibrational temperature of the relaxing nitrogen molecules. The present measurements thus confirm that the thermal excitation of Na by energy transfer from the N2 vibrational mode occurs with a much higher probability than by transfer from the rotational or translational modes. This result removes recent doubts concerning the interpretation of Na-line reversal temperatures in terms of N2 vibrational temperatures in earlier shock-tube studies. The probability of Na excitation by vibrationally excited N2 at the temperatures concerned is shown to be close to unity. The Na–N2 interaction process in various environments is briefly discussed in the light of this and other quenching measurements at low temperatures.
The measurements were made with a double-beam spectrum-line reversal system in which the sodium emission and absorption intensities are both recorded in the same optical path. The high-temperature measurements were made using a calibrated xenon arc as the background source for reversal. For the low-temperature measurements a tungsten strip lamp was employed. The system is able to measure Na-line reversal temperatures from 1500° to 5500°K to within an accuracy of ±2% and with a time resolution of 1 μsec. The optical arrangement and xenon source characteristics are described in detail.
Gas-Phase Radiolysis of n-Pentane. A Study of the Decompositions of the Parent Ion and Neutral Excited Pentane Molecule
Authors: Ausloos P. , Lias Sharon G. 
Published: January 2005

The direct and inert-gas-sensitized radiolyses of equimolar n-C5H12–C5D12–NO mixtures have been investigated in the absence and presence of an applied electrical field. It is shown that the partially deuterium-labeled products remain essentially unchanged upon the application of an electrical field, while the yields of the fully deuterated and nondeuterated species increase indicating that the former entirely originate from ionic processes. Comparison of the ion-pair yields of these partially labeled products, which can be ascribed mainly to hydride ion transfer from pentane to carbonium ions, with the ion-pair yields deduced from the 70-eV mass spectral pattern shows that, in the direct radiolysis, those fragment ions which are formed with a high activation energy are produced in a lower yield than in the mass spectrometer and are also reduced most strongly by an increase in pressure. In all experiments, both the propyl and butyl ions formed in the decomposition of the pentane ion acquire the secondary configuration either prior to or during reaction. In the inert-gas-sensitized radiolysis, the fragment ions which are formed with a high appearance potential are seen to increase with an increase in the recombination energy of the added inert gas.
From the applied-field experiments, it was possible to determine the modes of decomposition of neutral excited pentane molecules formed by electron impact. These were found to be analogous to those deduced from vacuum-ultraviolet photolysis experiments carried out at 1470 or 1237 Å. On the basis of the information gained from these experiments, and a detailed isotopic analysis of the products formed in the radiolysis both in the presence and absence of benzene, a value of 0.3±0.05 could be deduced for the number of neutral excited molecule decompositions per ion pair. Neutral excited pentane molecules are also seen to be formed in the inert-gas-sensitized radiolysis.