Polarization spectroscopy of Sr79Br and Sr81Br: Analysis of the X2Σ+ and B2Σ+ hyperfine structure

Microwave optical polarization spectroscopy has been used to measure the hyperfine structure in the X2Σ+ (v=0) electronic ground state of Sr79Br and Sr81Br. Optical hyperfine structure in the B2Σ+-X2Σ+ (0,0) system was resolved by Doppler-free laser polarization spectroscopy. The magnetic hyperfine parameters b and c and the electric-quadrupole hfs parameter eqQ were determined for the X2Σ+ and B2Σ+ states of both molecules. The magnetic hfs has been interpreted as an effect of halide electron spin polarization. The electric quadrupole coupling constants are compared with the alkali halides and discussed in terms of Sternheimer antishielding in polar molecules. (orig.)