Auger Process Following 1s-Photoionization: Ne III and Ne IV Line Production

Extract

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 (ω_K = 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 1s²2s^m 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).