Observation of D(2)1Π∼(2)3Π∼(2)3Σ+ states in KCs by polarisation labelling spectroscopy technique. Modelling of the D(2)1Π ∼ (2)3Π1 system

A first attempt towards analysis of three strongly interacting electronic states in KCs molecule, D(2)1Π, (2)3Π, and is presented. In this attempt a two-channel model is built for the D(2)1Π ∼ (2)3Π1 system. Our description results in two sets of Dunham-type coefficients and effective coupling terms, which allow to reproduce 2008 experimental values of energy levels for both states with an accuracy 0.029 cm in the range of vibrational levels below where no influence from the state is observed.