@article{f76d0bf51a54446eae3ab348cd07ad97,
title = "Bound-Electron Nonlinearity beyond the Ionization Threshold",
abstract = "We present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to ionization fractions of a few percent. These measurements enable determination of the strongly nonperturbative bound-electron nonlinear polarizability well beyond the ionization threshold, where it is found to remain approximately quadratic in the laser field, a result normally expected at much lower intensities where perturbation theory applies.",
author = "Wahlstrand, {J. K.} and S. Zahedpour and A. Bahl and M. Kolesik and Milchberg, {H. M.}",
note = "Funding Information: The authors thank I. Larkin, E. Rosenthal, N. Jhajj, and K. Y. Kim for discussions and technical assistance. J. K. W., S. Z., and H. M. M. acknowledge support by the Air Force Office of Scientific Research (FA9550-16-10284, FA9550-16-10121), the Army Research Office (W911NF1410372), the Office of Naval Research (N00014-17-1-2705, N00014-17-1-2778), and the National Science Foundation (PHY1301948). A. B. and M. K. acknowledge support by the Air Force Office of Scientific Research (FA9550-16-10121). Publisher Copyright: {\textcopyright} 2018 American Physical Society.",
year = "2018",
month = may,
day = "2",
doi = "10.1103/PhysRevLett.120.183901",
language = "English (US)",
volume = "120",
journal = "Physical Review Letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "18",
}