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Total and single differential cross sections have been calculated for electron impact ionization of Ar¹⁰⁺(1s²²s²²p⁴)³P^e using a method that combines the distorted-wave Born approximation and R-matrix theory. In this method, the incident/scattered electron is described by the distorted-wave Born approximation, while both the initial bound state and the final continuum states are expanded in terms of an R-matrix basis. Eight states of the final Ar¹¹⁺ ion are considered, namely 1s²2s²2p³⁴S^o2D^o2P^o and 1s² 2s2p⁴⁴P^e2D^e2S^e2P^e2P^o .

Up to the 2⁴- pole components of the interaction with ionizing electron were included, giving ten distinct Ar¹⁰⁺ continuum symmetries. We calculated single differential cross sections summed over final ionic states, as a function of the energy loss. These cross sections exhibit considerable structure due to autoionizing resonances. Total cross sections for production of Ar¹¹⁺ in each of the eight states are presented for impact energies from threshold energy at 19.8 au to 200 au. Our theoretical values for the total cross section are in good agreement with recent experimental results.