When heavy particles like and are stopped in matters, exotic atoms are formed in high excited states. Then, atomic cascade processes consisting of multistep transitions to the lower atomic states are taken place. Cascade processes study could lead to important information on hadrons and nuclei interactions in low energies. Measurment of the x-ray spectrum of these transitions would give lots of data about strong interaction. In this thesis, at first Kaon capture and internal Auger rates in K 3 He and K 4 He liquid and gaseous targets have been calculated. Radiative transition, Coulomb dexcitation, Stark and external Auger effects are studied subsequently and the rates of each processes in these atoms are calculated. Finally, the calculated results for K 3 He and K 4 He were compared in gaseous and liquid targets. These calculations could be used for simulation of the competetive cascade processes and also to calculate the x- ray yields from gaseous and liquid 3 He and 4 He targets.
