Dissociative ionization of pyrazine: A pathway to reactive interstellar ions

Abstract

Nitrogen-bearing cyclic compounds play a decisive role in the astrochemistry that prevails during the initial phases of star formation. Photoionization of these species under ultraviolet (UV) radiation leads to the formation of smaller cations. Reactions involving these highly reactive small cations could then form new molecules in the interstellar and circumstellar environments. Here, we report an interesting dissociative ionization pathway of pyrazine under UV irradiation, revealing a pronounced formation of the interstellar C3H3N+ ion compared to the parent cation. The C3H3N+ ion is identified as a key precursor for the synthesis of aromatic hydrocarbons containing nitrogen, such as pyridine and pyrimidine, which are of astrobiological significance. In addition, we also observed other nitrogen-bearing reactive cations and C2H2+. Our findings on the dissociative ionization pathways of pyrazine have implications for the abundances of reactive species in astrophysical media and concern both the top-down and bottom-up approaches of astrochemistry.