Gas-phase laboratory formation of large, astronomically relevant PAH-organic molecule clusters

Abstract

Polycyclic aromatic hydrocarbon (PAH) molecules may play an essential role in the prebiotic compound evolution network in interstellar clouds. In this work, an experimental study of large, astronomically relevant PAH-organic molecule clusters is presented. With the initial molecular precursors dicoronylene (DC; C48H20)-pyroglutamic acid (Pga, C5H7NO3), DC-proline (Pro; C5H9NO2), and DC-pyroglutaminol (Pgn; C5H9NO2), our experiments indicate that PAH–organic molecule cluster cations (e.g., (Pga)(1−2)C48Hn+, (Pro)(1−2)C48Hn+, and (Pgn)(1−6)C48Hn+) and carbon cluster–organic molecule cluster cations (e.g., (Pga)C48+, (Pro)(1−2)C48+, and (Pgn)(1−6)C48+) are gradually formed through an ion-molecule collision reaction pathway in the presence of a strong galactic interstellar radiation field. These laboratory studies provide a gas-phase growth route toward the formation of complex prebiotic compounds in a bottom-up growth process, as well as insight into their chemical-evolution behavior in the interstellar medium.