Probing the molecular structure and properties of neutral and anionic ground states of SO2 and CO2

Abstract

In this present investigation, the structures of SO2, SO2−, CO2 and CO2− as well as the adiabatic electron affinities of the corresponding SO2 and CO2 neutral parents are computed using the infinite-order coupled-cluster method with all singles and doubles and non-iterative inclusion of triple excitations (CCSD(T)) and the Moller–Plesset perturbation theory up to the second order (MP2). The molecular structure, fundamental frequencies with their corresponding intensities and electron localization functions of SO2 and SO2− are interpreted from respective ground-state optimized electronic structures calculated and compared with other simple tri-atomic molecules CO2 and CO2−, respectively. The electron localization function are then quantified and the second-order perturbation energies for different oxygen lone pairs (n) to σ* and π* interactions of S–O and C–O bond orbitals have been calculated by carrying out NBO analysis and the results are compared. The change in the electronic structure of the molecule after the attachment of a low-energy (≤15 eV) electron, thus forming a transient negative ion (TNI), can be interpreted from the n → σ* and n → π* interactions. The potential energy curves of SO2–SO2− and CO2– CO2− pairs are calculated as a function of S–O and C–O bond distance and bending angle. The adiabatic electron affinity of SO2 is calculated to be positive while that of CO2 is negative.