If a core electron is missing, a positive ion can autoionize further and lose a second electron in the Auger effect. In neon, X-ray excitation can remove a 1s electron, producing an excited Ne ion with configuration 1s 2s 2p. In the subsequent Auger process a 2s → 1s transition and simultaneous emission of a second electron from 2p leads to the Ne 1s 2s 2p ionic state.