Gas-phase Hydrogen/Deuterium Exchange on Large, Astronomically Relevant Cationic PAHs

Abstract To examine the gas-phase hydrogen/deuterium exchange on large, astronomically relevant cationic polycyclic aromatic hydrocarbons (PAHs), ion-molecule collision reaction between C 42 H 18 + (hexa-peri-hexabenzocoronene cations, HBC ) and D atoms is studied. The experimental results show that deuterated cations ([C m n ] , +2 ∗ up to ∼54) are efficiently formed, an effective determined. structure of newly formed bonding energy for these pathways investigated with quantum theoretical calculations. exothermic each pathway relatively high, existence competition deuteration dedeuteration confirmed. A kinetic model constructed simulate hydrogenation processes as a function time over typical astrophysical conditions. We infer if we do not consider other chemical evolution (e.g., photoevolution), then PAHs will reach final equilibrium state (reaction H/D atoms) very quickly regardless initial PAHs, scarce in interstellar medium.