Ultraviolet surprise: Efficient soft x-ray high-harmonic generation in multiply ionized plasmas

Popmintchev, D; Hernandez-Garcia, C; Dollar, F; Mancuso, C; Perez-Hernandez, JA; Chen, MC; Hankla, A; Gao, XH; Shim, B; Gaeta, AL; Tarazkar, M; Romanov, DA; Levis, RJ; Gaffney, JA; Foord, M; Libby, SB; Jaron-Becker, A; Becker, A; Plaja, L; Murnane, MM; Kapteyn, HC; Popmintchev, T