Theoretical investigation of the vibrational structure of the Ar–CO2 complex

Abstract

We develop a new flexible-monomer two-body ab initio potential energy surface (PES) for the Ar−CO2 complex. The accuracy of this new potential function is validated by its agreement in the vibrational spectrum of the complex. Vibrational self-consistent field theory (VSCF) and vibrational configuration interaction (VCI) theory were employed to solve the complete vibrational Hamiltonian, including both intermolecular and intramolecular degrees of freedom. We observe excellent agreement with theoretical and experimental results for the vibrational energy levels in the Terahertz region. In the intramolecular region, we confirm the slight splitting of the bending modes of the CO2 monomer, where the in-plane bend is 0.83 cm−1 less energetic than the out-of-plane mode. We also explore the combination bands in the asymmetric stretching region of the CO2 monomer that involve the intermolecular motions, and show that these results compare favorably to the fundamental intermolecular vibrational energy levels.