Two-photon sequential double ionization of argon in the region of Rydberg autoionizing states of Ar+ Elena V. Gryzlova, Alexei N. Grum-Grzhimailo, Maksim D. Kiselev and Sergey M. Burkov Eur. Phys. J. D, 73 5 (2019) 93 Published online: 07 May 2019 DOI: 10.1140/epjd/e2019-90678-x