Study of the A1Σ+ and b3Π0 states in LiCs by a polarization labelling spectroscopy technique

•The A1Σ+~b3Π0←X1Σ+ band system of LiCs is experimentally observed.•Deperturbation analysis done on the interacting A and b states.•The molecular constants and potential curves of the A1Σ+ and b3Π0 states are determined.•The electronic part of the spin-orbit interaction matrix element is estimated.

A polarization labelling spectroscopy technique was used to investigate the A1Σ+←X1Σ+ band system of the 7LiCs molecule in a heat-pipe oven. All 27 observed vibrational levels of the A state were found to be subject to strong perturbations assigned to interaction with the b3Π0 state. The deperturbation analysis provided molecular constants of the A and b states and a value of the electronic part of the spin-orbit interaction matrix element 〈b3Π0∣Hso∣A1Σ+〉.