Knowledge Bank

The $B2\Sigma +-X2\Sigma +$ system of strontium monobromide produced in a gas phase reaction was investigated by using Doppler free laser polarization spectroscopy. The extremely dense spectra could only be assigned with the help of microwave polarization $labeling1$) and additional band selective detection of the laser induced fluorescence. About 1500 lines from the (0,0), (1,1), and (2,2) bands were identified and fitted together with the results of independent microwave measurements of the $X2\Sigma +$ state in a weighted least squares fit. Local perturbations were found in all vibrational states of both isotopic species and attributed to the interaction of $B2\Sigma +,vB$ with $A2\pi 1/2,vA=vB\mathrm{<mrow\; data-mjx-texclass="ORD">+3</mrow>}$. Band head positions of $\Delta v=\pm 1$ bands were used for the vibrational analysis. Applying microwave optical polarization spectroscopy (MOPS)2) we were able to resolve the hyperfine structure in the $X2\Sigma +$ state and determine ground state hfs parameters of $Sr79Br$ and $Sr81Br$. This way the hfs in the sub-Doppler optical spectra of the B-X system could be interpreted and hfs parameters for the $B2\Sigma +$ state be derived.