Low energy electron impact on gas phase 5-nitrouracil

Excitation of the first electronic states, vibrational excitation between 1 and 3 eV, and negative ion formation (0–2 eV) in gas phase 5-nitrouracil are presented. Five singlet states are clearly identified at 4.76; 5.72; 6.82; 7.82 and 9.2 eV. A band at 3.7 eV could be assigned to a triplet state. The vibrational modes observed indicate resonant states having both π∗ and σ∗ character. The most intense anions (M−NO2)−, (M−H)− appear at zero energy with huge cross sections (⩾10−18 m2). Anion cross sections versus electron energy reveal structures interpreted using the anion energy thresholds found by DFT calculations.