A multireference configuration interaction study of the low-lying electronic states of ClO+2 and the X 1A1 state of ClO−2

Abstract

Near-equilibrium two-dimensional (C2v symmetry) potential energy functions of the first seven electronic states of ClO2+ and the ground X 1A1 electronic state of ClO2− have been calculated using internally contracted multireference configuration interaction (CMRCI) wave functions. In the case of ClO2+, five electronic states (3B2, 3A2, 1A2, 3B1, and 1B1) are predicted to lie within 3 eV of the X 1A1 ground state, while a 1B2 state has a calculated Te of just over 5 eV. In the X state, the equilibrium geometry is calculated by CMRCI to be re=1.423 Å and θe=120.8°. Harmonic vibrational frequencies of 1012 (ω1), 511 (ω2), and 1283 cm−1 (ω3) were derived from the computed potential energy function, and ω1 and ω2 were found to be in good agreement with the values estimated from the photoelectron spectrum of ClO2. For the X 1A1 state of ClO2−, calculated spectroscopic constants include re=1.573 Å, θe=113.9°, ω1=789 cm−1, ω2=378 cm−1, and ω3=848 cm−1. Electric dipole moment functions have also been derived for both species in their electronic ground states. The calculated equilibrium dipole moments for ClO2+ and ClO2− 1.46 and 2.55 D, respectively, make them good candidates for observation by pure rotational spectroscopy. Within the double harmonic approximation, fundamental infrared intensities have also been derived, and these results predict a relatively intense infrared vibrational spectrum in the ν3 mode of ClO2−.