Reaction of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O. Examination of the translational energy dependence of the cross sections of endothermic reactions

Reactions of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O to yield metal oxide ions are examined using an ion beam apparatus. Reaction cross sections sigma as a function of ion translational energy E are reported. With one exception, Fe + +N2O, the cross sections exhibit an energy threshold Eo. Several models are used to interpret the excitation functions for the O2 reactions and it is concluded that the classical line-of-centers form sigma alpha (1–Eo/E) is most useful. Bond energies derived in this manner are D°(CrO + ) = 3.45±0.1 eV, D°(MnO + ) = 2.48±0.1 eV, D°(FeO + ) = 3.01±0.1 eV, D°(CoO + ) = 2.76±0.1 eV, and D°(NiO + ) = 1.95±0.1 eV. Since these bond energies are all greater than D°(N2–O) = 1.7 eV, the observation of energy thresholds for the reactions with N2O are surprising. These results are explained in terms of a qualitative view of the electronic potential energy surfaces involved

New Indicators for AGN Power: The Correlation Between [O IV] lambda 25.89 micron and Hard X-ray Luminosity for Nearby Seyfert Galaxies

We have studied the relationship between the [O IV] lambda 25.89 micron emission line luminosities, obtained from Spitzer spectra, the X-ray continua in the 2-10 keV band, primarily from ASCA, and the 14-195 keV band obtained with the SWIFT/Burst Alert Telescope (BAT), for a sample of nearby (z < 0.08) Seyfert galaxies. For comparison, we have examined the relationship between the [O III] 5007, the 2-10 keV and the 14-195 keV luminosities for the same set of objects. We find that both the [O IV] and [O III] luminosities are well-correlated with the BAT luminosities. On the other hand, the [O III] luminosities are better-correlated with 2-10 keV luminosities than are those of [O IV]. When comparing [O IV] and [O III] luminosities for the different types of galaxies, we find that the Seyfert 2's have significantly lower [O III] to [O IV] ratios than the Seyfert 1's. We suggest that this is due to more reddening of the narrow line region (NLR) of the Seyfert 2's. Assuming Galactic dust to gas ratios, the average amount of extra reddening corresponds to a hydrogen column density of ~ few times 10^21 cm^-2, which is a small fraction of the X-ray absorbing columns in the Seyfert 2's. The combined effects of reddening and the X-ray absorption are the probable reason why the [O III] versus 2-10 keV correlation is better than the [O IV] versus 2-10 keV, since the [O IV] emission line is much less affected by extinction. Overall, we find the [O IV] to be an accurate and truly isotropic indicator of the power of the AGN. This suggests that it can be useful in deconvolving the contribution of the AGN and starburst to the spectrum of Compton-thick and/or X-ray weak sources.Comment: Accepted for publication in the Astrophysical Journal. 31 pages, 6 figures, 4 table

Cobalt carbene ion: Reactions of Co+ with C2H4, cyclo-C3H6, and cyclo-C2H4O

An ion beam apparatus is employed to study the formation of the cobalt carbene ion, CoCH + 2. This ion is produced in the endothermic reaction of cobalt ions with ethene and cyclopropane and in an exothermic reaction with ethylene oxide. A model is proposed to account for the dependence of experimental cross sections on relative kinetic energy for the endothermic reactions. Using this model to interpret the experimental results, a bond dissociation energy D°(Co+–CH2)=3.7±0.3 eV is derived

Reaction of O_2 ^+(X ^2Π_g) with H_2 , D_2 , and HD: Guided ion beam studies, MO correlations, and statistical theory calculations

Absolute cross sections are measured for the reactions of O_2 ^+(X ^2Π_g) with H_2 , D_2 , and HD from thermal energies to over 4 eV. The OH^+ + OH, HO_2^+ + H, O^+ + H_2O, and H_2O^+ + O product channels (and the corresponding isotopic analogs) are observed, although H_2^+ + O_2 is not. While the first three products appear at their thermodynamic thresholds, formation of H_2O^+ + O, the least endothermic channel, exhibits a barrier to reaction. In the HD system, the DO_2^ + product ion is strongly favored over the HO^2^+ product. Results for internally excited O_2^+ reactants, probably the a  ^4Π_u state, are also presented. Analysis of the excitation functions, molecular orbital arguments, and statistical kinetic theories are used to understand the mechanisms and dynamics of this reaction. It is shown that the inefficiency of the O^+ product channel is due to spin and symmetry constraints. The other three product channels proceed through a long‐lived intermediate, but formation of this intermediate from reactants requires surmounting a barrier measured to be 1.1±0.1 eV. The intramolecular isotope effects are shown to be due to statistical and dynamic effects

Reaction of Zn^+ with NO_2. The gas-phase thermochemistry of ZnO

The homolytic bond dissociation energies of ZnO and ZnO^+ have been determined by using guided ion‐beam mass spectrometry to measure the kinetic‐energy dependence of the endothermic reactions of Zn^+ with nitrogen dioxide. The data are interpreted to yield the bond energy for ZnO, D^0_0=1.61±0.04 eV, a value considerably lower than previous experimental values, but in much better agreement with theoretical calculations. We also obtain D^0_0(ZnO^+)=1.67±0.05 eV, in good agreement with previous results. Other thermochemistry derived in this study is D^0_0(Zn^+–NO)=0.79±0.10 eV and the ionization energies, IE(ZnO)=9.34±0.02 eV and IE(NO_2)=9.57±0.04 eV

Endothermic reactions of uranium ions with N2, D2, and CD4

An ion beam apparatus is employed to study the reactions of uranium ions with N2, D2, and CD4 at laboratory energies up to 335 eV. The endothermic reaction of U + with nitrogen leads to the product UN + for which a bond dissociation energy D (UN + ) =4.7±0.2 eV is determined, corresponding to DeltaHf(UN + ) =272±7 kcal/mole. Endothermic reactions of U + with D2 and CD4 lead to formation of UD + with D (UD + ) =2.9±0.1 eV and DeltaHf(UD + ) =254±6 kcal/mole. The dependence of experimental reaction cross sections on relative kinetic energy is discussed in terms of simple models for reaction. The proton affinity of uranium is determined, P.A.(U) =238±5 kcal/mole, and this exceptionally high value is compared to other atomic and molecular base strengths

Analyses of Failure Mechanisms and Residual Stresses in Graphite/Polyimide Composites Subjected to Shear Dominated Biaxial Loads

This research contributes to the understanding of macro- and micro-failure mechanisms in woven fabric polyimide matrix composites based on medium and high modulus graphite fibers tested under biaxial, shear dominated stress conditions over a temperature range of -50 C to 315 C. The goal of this research is also to provide a testing methodology for determining residual stress distributions in unidirectional, cross/ply and fabric graphite/polyimide composites using the concept of embedded metallic inclusions and X-ray diffraction (XRD) measurements