Potassium-uracil/thymine ring cleavage enhancement as studied in electron transfer experiments and theoretical calculations

We report experimental and theoretical studies on ring cleavage enhancement in collisions of potassium atoms with uracil/thymine in order to further increase the understanding of the complex mechanisms yielding such fragmentation pathways. In these electron transfer processes time-of-flight (TOF) negative ion mass spectra were obtained in the collision energy range 13.5 – 23.0 eV. We note that CNO– is the major ring breaking anion formed and its threshold formation is discussed within the collision energy range studied. Such decomposition process is supported by the first theoretical calculations in order to clarify how DNA/RNA pyrimidine bases fragmentation is enhanced in electron transfer processes yielding ion-pair formation.