Superfície de energia potencial molecular para ArHSO2

Abstract

The reaction between OH and SO radicals is a key process in atmospheric chemistry and combustion, with the HSO2 biradical serving as a pivotal intermediate. However, theoretical models based on isolated bimolecular collisions often fail to reproduce experimentally observed formation rates, predicting the premature redissociation of the activated complex. This work investigates the third-body effect on HSO2 stabilization, focusing on the construction and characterization of a Potential Energy Surface (PES) for the ArHSO2 quaternary system. Using the Double-Layer Many-Body Expansion (DMBE) formalism, the intermolecular interaction between the Argon atom and the molecular fragment was mapped. The results revealed a highly anisotropic energy landscape, identifying a global minimum with an interaction energy of −0.44851/Eh at an equilibrium distance of R = 4.15/a0. Vibrational analysis confirmed the dynamic stability of the system, showing no imaginary frequencies (kneg = 0) and the presence of low-energy intermolecular modes (ω ≈ 170 cm−1 ), typical of flexible van der Waals complexes, in which atoms are held together by weak intermolecular forces. It is concluded that Argon acts as an effective microscopic heat bath, facilitating (V − T) energy transfer and promoting the thermal stabilization of the biradical, thus bridging the gap between theory and experimental data.