On Ambient-light-induced intermolecular Coulombic decay in unbound pyridine monomers

TL;DR

This paper critically examines ambient-light-induced intermolecular Coulombic decay in unbound pyridine monomers, arguing that previous claims are unlikely due to low probabilities and proposing an alternative dissociative ionization mechanism.

Contribution

The study challenges prior reports by analyzing collision-free conditions and introduces a new mechanism involving pyridine dimer dissociation for pyridine cation formation.

Findings

ICD unlikely in unbound pyridine monomers due to low excitation probabilities

Proposes dissociative ionization of pyridine dimers as the cation source

Highlights the importance of collision conditions in ICD processes

Abstract

A recent report by Barik et al. [Nature Chemistry 14, 1098, 2022] on ambient-light-induced intermolecular Coulombic decay (ICD) in unbound pyridine monomers proposes the formation of a pyridine cation via intermolecular Coulombic decay following a three-body association/collision, wherein all the three pyridine molecules are in the excited state. The collision-free conditions of the free-jet expansion, an abysmally low probability of finding three independently excited pyridine molecules in the vicinity of each other, and extremely low excited state lifetimes negate the possibility of ICD in unbound pyridine monomers. An alternate mechanism, wherein the pyridine monomer cation originates from the dissociative ionization of pyridine dimers following a three-photon absorption process, based on the translational energy measurements of pyridine cation is proposed.