In current study, a non-stoichiometric bromine-doped potassium K2Br+and K3Br+clusters are generated by combining a Knudsen effusion cell as a chemical reactor with thermal or surface ionization,and selected by a magnetic sector mass spectrometer. Furthermore, their ionization energies (IEs) are calculated for the first time using B3LYP/9-ve PP(K),cc-pVTZ-PP(Br) level of theory. Herein, presented results indicate that experimentally obtained IEs by Ionov equation, 4.10 ± 0.20 eV for K2Br+, and 4.03 ± 0.20 eV for K3Br+, are in consistence with their theoretically determined IEs.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 2016