G. Naresh Patwari | Searcharxiv

arXiv2025

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

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.

physics.chem-ph↗

arXiv2022

Outer Valence Intermolecular Coulombic Decay in Hydrogen-Bonded Complexes Induced by Resonant Two-Photon Excitation by 4.4 eV Photons

Photoexcitation of van der Waals complexes can lead to several decay pathways depending on the nature of the potential energy surfaces. Upon excitation of a chromophore in a complex, ionization of its weakly bound neighbour via energy transfer happens via a unique relaxation process known as intermolecular Coulombic decay (ICD); a phenomenon of renewed focus owing to its relevance in biological systems. Herein, we report an experimental evidence of outer-valence ICD induced by multiphoton excitation by near UV radiation of 4.4 eV photons, hitherto unknown in molecular systems. In the binary complexes of 2,6-difluorophenylacetylene with aliphatic amines such as dimethylamine and trimethylamine a resonant two-photon excitation is localized on the 2,6-difluorophenylacetylene chromophore. The absorbed energy is then transferred to its hydrogen-bonded partner amine and resulting in the formation of an amine cation. The kinetic energy distribution of the amine cations is invariant with respect to the initial geometry of the binary complex. The present experimental results combined with electronic structure calculations provide valuable insights into the nature of ICD in van der Waals complexes and more importantly, the role of ICD as a fast, efficient, and prominent decay channel following excitation at modest (4.4 eV) photon energies.

physics.chem-ph↗