Dissociative photoionization of SF6 via the A/B 2T1u/2T2u ionic state using TPEPICO velocity map imaging and density functional theory calculations

Abstract

Dissociative photoionization (DPI) of sulfur hexafluoride (SF6) is critical for understanding the related plasma etching processes in semiconductor manufacturing. In this study, we have investigated the DPI dynamics of SF6 via the A/B 2T1u/2T2u ionic states using threshold photoelectron–photoion coincidence (TPEPICO) velocity map imaging and density functional theory (DFT) calculations. The near-degeneracy of the A2T1u and B2T2u states complicates their dissociation dynamics. By combining TPEPICO experiments with DFT calculations of potential energy curves along the S–F bond cleavage coordinate, we reveal two competing dissociation pathways: adiabatic predissociation via the A2T1u state and internal conversion (IC) to the repulsive X2T1g state. Bimodal kinetic energy release distributions and anisotropy parameters provide evidence for non-statistical dynamics, where branching ratios change with ionization energy due to competition between intramolecular vibrational redistribution and IC. These findings offer molecular-level insights into the dissociation mechanisms of SF6+ excited states.