High resolution study of the B1Π–X1∑+ band system of KLi and the isotopic effect

The Doppler-free polarization spectrum was measured for the B1Π–X1∑+ band system of the 39K7Li molecule. The Dunham coefficients describing the X state and f-parity levels of the B state are reported. Numerous transitions were observed for the 41K7Li and 39K6Li isotopomers, the latter ones displaying anomalous isotopic shifts. The anomalies are discussed in terms of mass-independent `reduced' Dunham coefficients and mass-scaling factors.