Ab initio Calculations on Excited Molecular Ions of Ethylene and Acetylene

Abstract

Ab initio calculations of the energy and wave functions for neutral molecules and excited molecular ions are used to interpret the EMS and PES spectra of acetylene and ethylene. The five satellite regions of acetylene are assigned to intensity borrowed from 2σ_g, 3σ_g and 2σ_u primary hole states by ion states with configurations (π_u)⁻² (δ_g)¹, (π_u)⁻² (3σ_g)⁻¹ (π_g)², and (π_u)⁻¹ (3σ_g)⁻¹ (π_g)¹. The Dyson orbitals for the satellite regions of acetylene and ethylene are shown to differ from the Dyson orbitals of the primary holes. The importance of choosing basis sets appropriate to the excited states of the ion is illustrated.