Microwave observation of 41K79Br and 41K81Br from laser-ablated potassium bromide

► The 41K isotopologs of KBr have been observed by microwave spectroscopy. ► Molecules were produced by laser ablation and the experimental design is described. ► A set of isotopically invariant parameters are determined. ► Previously unobserved transitions of NaCl and KI are also reported.