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

¹ CAS Key Laboratory of Crust-Mantle Materials and Environment, University of Science and Technology of China, Hefei 230026, PR China
e-mail: jfzhen@ustc.edu.cn
² CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei 230026, PR China
³ CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, PR China
⁴ CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China

Received: 28 May 2021
Accepted: 23 September 2021

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₎C₄₈H_n⁺, (Pro)₍₁₋₂₎C₄₈H_n⁺, and (Pgn)₍₁₋₆₎C₄₈H_n⁺) 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.