The muon is captured into a high orbital angular momentum state. Once captured in this state an excited muonic atom is formed. Since the muon mass is 207 times larger than the electron's mass, the muon is actually captured between the electron orbits and the nucleus. Since the muonic atom is formed in an excited state, the muon will cascade down to its ground state, namely the 1s state. In the first stage of this cascade the muonic atom de-excites by giving off Auger electrons.
Auger electrons are outer atomic electrons which take the energy released by the muon's transitions.
These Auger electrons leave the atom in an ionized state. As the muon cascades down, the energy given off in each transition increases to the point where the Auger effect is small compared to X-ray transistions. So for the rest of the muon's cascade, X-rays are given off until the muon reaches the 1s state. This program is stored at Computer Physics Communications. Once the muon reaches the 1s state, the muon has 2 options.