The B 2Σ+-X 2Σ+ system of SrF: Precise spectroscopic constants from a combined fit of microwave and sub-doppler optical spectra

Doppler-free polarization spectroscopy has been used to measure 295 lines in the (0.0), (1.1) and (2.2) bands of the B ²Σ⁺-X ²Σ⁺ system of SrF. These optical data were combined with the results of separate microwave measurements of the X ²Σ⁺ state in a weighted least-squares fit. It is shown that the accuracy of spectroscopic constants of the B ²Σ⁺ state is remarkably improved by the reduction of the upper-state—lower-state correlations. A more reliable determination of the vibrational dependence of rotational and spin—rotation parameters became possible.