High-resolution photoabsorption spectra of CO B.lld NO below the 0 Is ionization threshold are presented. For both molecules, the vibrational finestructure of the 0 ls-t 'II"• a.nd 0 ls-1 Ryd (Rydberg) excitations could be resolved, allowing a derivation of the vibrational energies and intra.moleculal' distances of the core-excitation states in CO and NO from Ftanck-Condon analyses. The spectral features of the 0 ~s-1 Ryd region in CO are reassigned on the basis of the new experimental results. The results obtained for the 0 ls-1 3s Rydberg state in NO support the idea of a WP.akt>.nihg of the molecular bond upon an 0 15-J. ionization process.

Absolute photoionization cross sections have been measured for a mixture of ground-state and metastable O ii (O +) ions at photon energies ranging from 29.9 to 46.0 eV (414.7 to 269.5 Å). All measurements were performed by merging an O + beam with synchrotron radiation from an undulator beam line at the Advanced Light Source (ALS). At a resolution of 17 meV, more than 70 spectral features have been resolved, most of them identified and characterized. These measurements are compared with two independent R-matrix calculations and the data in TOPbase. All three calculations agree within 25% on the direct photoionization cross section, and with the absolute measurements within 40%. Some differences are noted in the predicted resonance positions among the three close-coupling R-matrix calculations, the TOPbase data being the least accurate. The estimated total experimental uncertainty varies from 15% to 20%. Such measurements benchmark theoretical photoionization cross section calculations performed within the framework of the Opacity Project and the Iron Project. Subject headings: atomic data-atomic processes-methods: laboratory

High-resolution absolute experimental measurements and two independent theoretical calculations were performed for photoionization of O 1 ions from the 2 P o and 2 D o metastable levels and from the 4 S o ground state in the photon energy range 30-35.5 eV. This is believed to be the first comparison of experiment and theory to be reported for photoionization from metastable states of ions. While there is correspondence between the predicted and measured positions and relative strengths of the resonances, the cross-section magnitudes and fine structure are sensitive to the choice of basis states.

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In this study, a solid solution of arsenical ammonium-sodium jarosite, with the approximate formula [(NH4)0.72 Na0.06(H3O)0.21]Fe3(2.52)(SO4)1.85 (AsO4)0.15 [(OH)4.41 (H2O)1.59], was synthesized. The precipitate particle main size was 38 µm, with spherical morphology. A decomposition reaction in alkaline media was carried out; this decomposition comprised three stages: an induction period, a progressive conversion and a stabilization period. The process was controlled by the chemical reaction, and the progressive conversion period was consistent with the shrinking core model. The dissolution reactions of the compound in NaOH media were characterized by an ash layer formed by solid residues made of Fe(OH)3 with adsorbed arsenate surrounding an unreacted core through which Na+, NH4+ and SO42− ions diffused into the solution. At the same time, OH− ions diffused from the solution into the reaction front until the core disappeared, indicating the end of the reaction.