Multiphoton double ionization of barium

The multiphoton double ionization of Ba from ~280 to 700 nm was investigated using laser pulses 5 ns long of peak intensity ~10¹⁰ W/cm². The spectrum consists of a number of strong resonances, which can be assigned to Ba⁺ transitions. Most of the assignments have been verified by pump-probe techniques. Thus, the Ba⁺⁺ observed is due to sequential ionization. The multiphoton ionization probability is highest for λ~500 nm, which matches a series of strong Ba and Ba⁺ transitions leading to double ionization     

Purine photoproducts

Abstract— DNA purine modifications by ultraviolet irradiation have not been as extensively studied as those of pyrimidines. However, a number of such reactions have been identified. These include photochemical addition of amino acids, photoalkylation by alcohols, amines and other compounds, photochemical activation of procarcinogens to mutagenic electrophiles, and formation of covalent linkages between DNA purines and adjacent bases. The recent characterization of two adenine-adenine di-adducts and the finding of endonucleases from two sources that incise ultraviolet-irradiated DNA at purine photoproducts indicate the possible biological importance of these moieties.     

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The Arrow-Barankin-Blackwell theorem in a dual space setting

In 1953 Arrow, Barankin, and Blackwell proved that, ifR ⁿ is equipped with its natural ordering and ifF is a closed convex subset ofR ⁿ , then the set of points inF that can be supported by strictly positive linear functionals is dense in the set of all efficient (maximal) points ofF. Many generalizations of this density result to infinite-dimensional settings have been given. In this note, we consider the particular setting where the setF is contained in the topological dualY ^* of a partially ordered, nonreflexive normed spaceY, and the support functionals are restricted to be either nonnegative or strictly positive elements in the canonical embedding ofY inY ^*. Three alternative density results are obtained, two of which generalize a space-specific result due to Majumdar for the dual system (Y,Y ^*)=(L ¹,L ).This research was supported in part by funds provided by the Provident Chair of Excellence in Applied Mathematics at the University of Tennessee, Chattanooga, Tennessee.