Removal of a 1s electron from atomic neon by highly energetic photons, gives rise mainly to the 1s2s22p6 state of singly ionized neon. This state c decay mostly by ejection of an Auger electron to form various excited terms of Ne+2. This process dominates largely the radiative Kα decay (ωK = 0.018). The main route to Ne+2 is 1s22s22p41D (61%) and there is no Auger decay to the ground final term (Krause et al, 1971). Shake up processes, i.e excitations of outer shells accompagning the 1s–electron ejection, produce mainly 1s2s22p5 np 2S states (n=3,4), 5% relatively to all processes (Krause, 1971). These np states radiationless decay producing numerous Ne+2 states. Shake off processes, i.e. ionizations of outer shells by the photoelectron, are not negligible, nearly 14% relatively to all processes (Krause, 1971) for photons with energy greater than 1 keV. Shake off process leads by radiationless transitions to three or four times ionized neon. The 1s2s2p5 state is strongly favoured by shake off process and decay to the main configurations of Ne+3 1s22sm 2pn (Krause, 1971). In an analagous way, the case of oxygen presents the same interesting features but there is actually a lack of experimental and theoretical data (Caldwell and Krause, 1993, Petrini and Araújo, 1993).