Polarisation labelling spectroscopy has been used to record the excitation spectrum of KCs between 21000 and 23000 cm(1). A strongly perturbed band system is observed in this range and assigned to transition from the ground X-1 Sigma(+) state to the excited 4(1)Pi state. A pointwise potential curve is constructed for the 4(1)Pi state and compared with the predictions of theoretical calculations performed both in Hund's case (a) and (c) models. (C) 2013 Elsevier B.V. All rights reserved.