Theoretical studies for the infrared spectra of Ar–CO2 complex: Fundamental and combination bands

Abstract Two potential energy surfaces (PESs) were constructed for the ground and excited states of Ar–CO 2 complex at the rigid rotor approximation. Besides the notable T-shape structure, two equivalent linear structures were also found on the PES for the first time. Based on the PESs of ground and excited states, the bound state calculations were performed to determine the rotational energy levels for the ground and excited states. In combination of the experimental spectroscopic parameters of ground state and the differences of rotational energy levels, we give a theoretical prediction of infrared spectra including one fundamental band and two combination bands for two isotopomers Ar– 12 C 16 O 2 and Ar– 12 C 18 O 2 in the ν 3 region of CO 2 monomer. The predicted transition frequencies and spectroscopic parameters of excited states are in excellent agreement with the available experimental data, and these results can also be used as a guide to perform the further investigation for the infrared spectra of combination bands experimentally.