When heavy negative particles ( ) are stopped in matter, like hydrogen, helium etc …, they usually form exotic atoms in highly excited states. The exotic atom formation is followed by an atomic cascade consisting of multistep transition to the lower atomic states. One of the most important sources of information on atomic cascade and strong hadron - nucleus interaction is the measurement of X-ray yields (intensities) due to radiative transition. In this thesis in addition to calculation of cascade transition rates of atoms, these processes have been simulated by Monte Carlo method. Almost all of the desired quantities can be obtained from this simulation. X-ray yields, absorption fraction from each atomic states and number of Stark process that occur during the life of are quantities of interest in this work. Among these quantities, the L line X-ray yields have been compared with the experimental data.