title: Strong-Field Photoionization as Excited-State Tunneling.
abstract: We show that, in an intense laser field, ultrafast photoionization can occur through quantum pathways that cannot be categorized as multiphoton ionization or ground-state tunneling. In this regime, the subcycle electron-wave-packet dynamics leading to photoionization occurs via electron excited states, from where the electrons tunnel to the continuum within a tiny fraction of the field cycle. For high field intensities, this ionization pathway is shown to drastically enhance the dynamic leakage of the electron wave packet into the continuum, opening an ionization channel that dominates over ground-state electron tunneling.
authors.affiliation: Physics Department, International Laser Center, M. V. Lomonosov Moscow State University, Moscow 119992, Russia.|Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, USA.|Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 143025, Russia.
authors.forename: E E
authors.initials: EE
authors.lastname: Serebryannikov
authors.affiliation: Physics Department, International Laser Center, M. V. Lomonosov Moscow State University, Moscow 119992, Russia.|Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843-4242, USA.|Russian Quantum Center, ul. Novaya 100, Skolkovo, Moscow Region 143025, Russia.
authors.forename: A M
authors.initials: AM
authors.lastname: Zheltikov