abstract
- A relativistic coupled-cluster study on the ytterbium monosulfide molecule (YbS) in synergy with a high resolution microwave spectroscopy study is reported. The quality of the potential energy surfaces and the surfaces of the nuclear electric quadrupole coupling constants (eQq's) computed using relativistic exact two-component (X2C) coupled-cluster singles and doubles (CCSD), CCSD augmented with a noniterative treatment of triple excitations [CCSD(T)], and the "Λ"-version of CCSD(T) [CCSD(T)Λ] is carefully assessed, comparing computed structure parameters and eQq values to precise experimental benchmark values derived from the microwave rotational spectrum of vibrationally excited YbS. The X2C-CCSD calculations are shown to provide qualitatively accurate results, while CCSD(T)Λ calculations provide reliable triples corrections. The inaccuracy of the corresponding CCSD(T) calculations is attributed to a strong variation of orbital rotation due to the coupling between the Yb[4f146s0]S[2s22p6] and Yb[4f136s1]S[2s22p6] configurations along the potential energy surface.