New ab initio adiabatic potential energy surfaces and bound state calculations for the singlet ground X1A1 and excited C1B2(21A′) states of SO2

We report new and more accurate adiabatic potential energy surfaces (PESs) for the ground X̃(1)A1 and electronically excited C̃(1)B2(2(1)A(')) states of the SO2 molecule. Ab initio points are calculated using the explicitly correlated internally contracted multi-reference configuration interaction (icMRCI-F12) method. A second less accurate PES for the ground X̃ state is also calculated using an explicitly correlated single-reference coupled-cluster method with single, double, and non-iterative triple excitations [CCSD(T)-F12]. With these new three-dimensional PESs, we determine energies of the vibrational bound states and compare these values to existing literature data and experiment.