Energy analysis of ejected electrons in the region of the Ar L₁-L_2,3M Coster-Kronig transitions (25–56 eV) induced by electron impact

Highlights: • High resolution L₁-L_2,3M Coster-Kronig spectra in Ar are obtained by electron impact. • Many features are due to the autoionizing decay of neutral doubly excited states. • Energy analysis of ejected electrons ruled out hypothesis of the state origins. - Abstract: The ejected electron spectra between 25 and 56 eV kinetic energy in Ar have been measured at several electron impact energies. When the incident energy is above the Ar 2s ionization potential the peaks due to the L₁-L_2,3M₁ and L₁-L_2,3M_2,3 Coster-Kronig (CK) transitions are expected to occur in this region of kinetic energy, but we observe a series of other narrow structures that overlap and sometime dominate the spectrum due to the CK transitions. These features have been attributed to the autoionizing decay of inner valence doubly excited states to the Ar ⁺ ground state.