Intracluster ion-molecule reaction in quinoline and isoquinoline dimers under the influence of diverse ionizing radiations

TL;DR

This study investigates how quinoline and isoquinoline dimers undergo ion-molecule reactions under various ionizing radiations, revealing potential pathways for molecular growth relevant to astrochemical environments.

Contribution

It demonstrates that diverse energetic radiations can induce intracluster reactions in PAH isomers, offering new insights into astrochemical molecular growth mechanisms.

Findings

Dimers form under ambient conditions but are low in population.

Radiation induces observable intracluster ion-molecule reactions.

Reactions depend on radiation type and intensity, revealing energetics.

Abstract

This work demonstrates the tendency of two model PANH isomers to dimerize under pure ambient evaporative conditions and then undergo complex intracluster ion-molecule reactions to produce rich chemistry. Despite the population of such dimers at room temperature is found to be relatively low, they are found to produce observable effects in typical stellar radiation conditions. It is also demonstrated that various types of energetic radiation (UV radiation at 266 nm, synchrotron VUV radiation and high-energy protons) can induce intracluster ion-molecule reactions in the dimers. The existence of such dimers is confirmed via the analysis of the mass-selected photoelectron spectra of various species observed in the mass spectra. The signal from such processes is enhanced by UV multiphoton ionization/dissociation and is analysed using energy-correlated time-of-flight mass spectrometry. These measurements, together with the dependence on laser intensity, disclose the reaction energetics as well as the hierarchy of the decay of the reaction products. The findings of this work on dimer-driven ion-molecular reactions in quinoline and isoquinoline provide an alternative to the path for molecular growth in the astrochemical environment through cluster dynamics, which is otherwise attributed to dust and ice-driven processes.