Intermolecular Charge Transfer Induced Fragmentation of Formic Acid Dimers

Charge Transfer Effect on Relaxation Mechanism in Hydrated Pyrrole-Water Systems Following N-2s Ionization

This study investigates the relaxation mechanisms of pyrrole and pyrrole-water clusters (C4H5N-(H2O)n, wheren = 0 - 3 ${n = 0 - 3}$ ) following N-2s ionization of pyrrole. Using various theoretical methods, we focus on the influence of water molecules and charge transfer on these non-radiative relaxation pathways. Our simulations included pyrrole solvated in 494 explicit water molecules equilibrated at 300 K and also employed a polarizable continuum model (PCM) to make the system more realistic and gain additional insights. In hydrated environments, the hydrogen bonding network between pyrrole and surrounding water molecules facilitates enhanced non-radiative relaxation pathways following inner valence ionization. Since these are hydrogen bonding systems, we have explored the possibility of proton transfer, which could occur in conjunction with other electronic decay processes.

Ultrafast fragmentation dynamics of carbon dioxide trication induced by an intense laser field: Transient deformation route vs direct Coulomb repulsion

We present a combined experimental and theoretical study of the detailed fragmentation process of CO23+→ CO2+ + O+ induced by an intense laser field. Through multicoincidence fragment measurements together with ab initio molecular dynamics (AIMD) simulations, we find that a transient deformation route appears in competition with the expected Coulomb explosion. The AIMD simulations visually demonstrate that CO23+ undergoes several bending vibrations in ∼50-480 fs, and in the final dissociation stages, the electron density distribution in three-dimensional space migrates from the O ion to the C ion, while the bond strength rapidly decreases to 0, resulting in bond breaking assisted by the asymmetric stretching vibrations. The measured kinetic energy releases are in general agreement with AIMD simulations, and the deduced amount of energy transfer into the vibrational and rotational degrees of freedom of CO2+ is about 3 eV less than that estimated by the Coulomb potential.

Interatomic and intermolecular decay processes in quantum fluid clusters

In this comprehensive review, we explore interatomic and intermolecular correlated electronic decay phenomena observed in superfluid helium nanodroplets subjected to extreme ultraviolet radiation. Helium nanodroplets, known for their distinctive electronic and quantum fluid properties, provide an ideal environment for examining a variety of non-local electronic decay processes involving the transfer of energy, charge, or both between neighboring sites and resulting in ionization and the emission of low-kinetic energy electrons. Key processes include interatomic or intermolecular Coulombic decay and its variants, such as electron transfer-mediated decay. Insights gained from studying these light-matter interactions in helium nanodroplets enhance our understanding of the effects of ionizing radiation on other condensed-phase systems, including biological matter. We also emphasize the advanced experimental and computational techniques that make it possible to resolve electronic decay processes with high spectral and temporal precision. Utilizing ultrashort pulses from free-electron lasers, the temporal evolution of these processes can be followed, significantly advancing our comprehension of the dynamics within quantum fluid clusters and non-local electronic interactions in nanoscale systems.

Revealing the Role of N Heteroatoms in Noncovalent Aromatic Interactions by Ultrafast Intermolecular Coulombic Decay

Despite the widely recognized importance of noncovalent interactions involving aromatic rings in many fields, our understanding of the underlying forces and structural patterns, especially the impact of heteroaromaticity, is still incomplete. Here, we investigate the relaxation processes that follow inner-valence ionization in a range of molecular dimers involving various combinations of benzene, pyridine, and pyrimidine, which initiate an ultrafast intermolecular Coulombic decay process. Multiparticle coincidence momentum spectroscopy, combined with ab initio calculations, enables us to explore the principal orientations of these fundamental dimers and, thus, to elucidate the influence of N heteroatoms on the relative preference of the aromatic π-stacking, H-bonding, and CH-π interactions and their dependence on the number of nitrogen atoms in the rings. Our studies reveal a sensitive tool for the structural imaging of molecular complexes and provide a more complete understanding of the effects of N heteroatoms on the noncovalent aromatic interactions at the molecular level.