Electron attachment to gas-phase uracil.
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.
Denifl
S
S
Institut für Ionenphysik, Leopold-Franzens Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria.
Ptasińska
S
S
Hanel
G
G
Gstir
B
B
Probst
M
M
Scheier
P
P
Märk
T D
TD
D000465:Algorithms; D004583:Electrons; D005740:Gases / Q000737:chemistry*; D007536:Isomerism; D014498:Uracil / Q000737:chemistry*
D005740:Gases; D014498:Uracil