Theoretical Studies Of Potential Energy Surface And Microwave Spectrum Of Ar-SO₂ Van Der Waals Complex

Van der Waals(vdW)complexes have been one of the important topics in both experiment and theory.In this thesis,theoretical studies of the potential energy surface(PES)and bound states are performed for Ar-SO2 van der Waals(vdW)complex.The main results are as follows:(1)A three-dimensional intermolecular potential energy surface is constructed from 2093 ab initio data points which are calculated at the level of single and double excitation coupled-cluster method with a non-iterative perturbation treatment of triple excitations[CCSD(T)]using aug-cc-pVTZ basis set supplemented with bond functions(3s3p2d2flg).Lagrange polynomial formula is used to construct the IPES of Ar-SO2.We analyzed the potential energy surface global minima and saddle points,and found that Ar-SO2 van der Waals complex at the global minimum has a non-planar structure.(2)The bound states energies are calculated based on the PES and the rovibrational levels are assigned.The tunneling splitting of each energy level is about 0.02 cm-1.Seventy-three pure rotational transition frequencies are calculated,including both a-type and c-type transitions.The root-mean-square deviation between experimental data and calculated values is 0.0042 cm-1 for a-type transitions and 0.0120 cm-1 for c-type transitions,respectively.Fourteen spectroscopic parameters are derived by fitting a standard asymmetric top Hamiltonian.The good agreement between the parameters obtained from the calculated transitions and the experimental observations shows the high accuracy of our ab initio PES.