Re-analysis of the 000 – 000 and 000 – 100 bands in the Ã2Π1/2-X̃2Σ+ system of YbOH: Revised estimates of the ground state spin-rotation splitting parameters

In the first observed spectrum (Melville and Coxon, 2001) of the 000 – 000 band of the A 2 Π 1 / 2 - X 2 Σ + transition of YbOH, spin-doublets were resolved only at high-N and yielded a ground state spin-rotation constant, γ, that differs in both sign and magnitude from that obtained from recent higher resolution low–N data (Steimle and co-workers, 2018–2019). This note re-examines the original 2001 data and shows that the discrepancy is resolved by rearrangement of the original Q11 and R12 branch and isotopologue assignments of the 000 – 000 origin band. Re-analysis of the 000 – 100 band results in a revised negative γ for the υ1 = 1 (Yb-O stretch) level of the X 2 Σ + state which is close to that obtained from the 2018–2019 data.