title: Electron attachment to gas-phase uracil.
abstract: We present results about dissociative electron attachment (DEA) to gas-phase uracil (U) for incident electron energies between 0 and 14 eV using a crossed electron/molecule beam apparatus. The most abundant negative ion formed via DEA is (U-H)-, where the resonance with the highest intensity appears at 1.01 eV. The anion yield of (U-H)- shows a number of peaks, which can be explained in part as being due to the formation of different (U-H)- isomers. Our results are compared with high level ab initio calculations using the G2MP2 method. There was no measurable amount of a parent ion U-. We also report the occurrence of 12 other fragments produced by dissociative electron attachment to uracil but with lower cross sections than (U-H)-. In addition we observed a parasitic contaminating process for conditions where uracil was introduced simultaneously with calibrant gases SF6 and CCl4 that leads to a sharp peak in the (U-H)- cross section close to 0 eV. For (U-H)- and all other fragments we determined rough measures for the absolute partial cross section yielding in the case of (U-H)- a peak value of sigma (at 1.01 eV)=3 x 10(-20) m2.
authors.affiliation: Institut für Ionenphysik, Leopold-Franzens Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Denifl
authors.forename: S
authors.initials: S
authors.lastname: Ptasińska
authors.forename: G
authors.initials: G
authors.lastname: Hanel
authors.forename: B
authors.initials: B
authors.lastname: Gstir
authors.forename: M
authors.initials: M
authors.lastname: Probst
authors.forename: P
authors.initials: P
authors.lastname: Scheier
authors.forename: T D
authors.initials: TD
authors.lastname: Märk
mesh_terms: D000465:Algorithms; D004583:Electrons; D005740:Gases / Q000737:chemistry*; D007536:Isomerism; D014498:Uracil / Q000737:chemistry*
chemical_list: D005740:Gases; D014498:Uracil