The B²Σ+ - X²Σ+ 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.