Dissociative electron attachment to gas-phase 5-bromouracil

We report measurements of dissociative electron attachment (DEA) to gaseous 5-bromouracil (BrU) for incident electron energies between 0 and 16 eV. Low energy electron impact on BrU leads not only to the formation of a long lived parent anion BrU-, but also various anion fragments resulting from endo- and exo-cyclic bond ruptures, such as Br-, uracil-yl anions, i.e., (U-yl)(-), OCN-, and a 68 amu anion tentatively attributed to H2C3NO-. The incident electron energy dependent signatures of either the Br- and (U-yl)(-) yields (at 0, 1.4, and 6 eV), or the OCN- and H2C3NO- yields (at 1.6 and 5.0 eV) suggests competing DEA channels for anion fragment formation. The production cross sections, at 0 eV incident electron energy, for BrU-, Br-, and (U-yl)(-) are estimated to be about 6 x 10(-15), 6 x 10(-14), and 1.0 x 10(-15) cm(2), respectively. (C) 2000 American Institute of Physics. [S0021-9606(00)01031-X].