“…However, until now, direct observations of satellites in conventional photoelectron spectroscopy have been limited to cases where only inner or outer valence electrons are involved in the shake-up process. Core-hole photoemission satellites (i.e., DCH states) have been observed only indirectly using photoabsorption [15,16] or x-ray emission [17,18], in coincidence studies [2][3][4], or in multiphoton experiments [6,7]. Specifically for argon, three early photoabsorption studies focused on the 1s −1 2l −1 4p 2 doubly excited states [15,16,19].…”