title: Unified Time and Frequency Picture of Ultrafast Atomic Excitation in Strong Laser Fields.
abstract: Excitation and ionization in strong laser fields lies at the heart of such diverse research directions as high-harmonic generation and spectroscopy, laser-induced diffraction imaging, emission of femtosecond electron bunches from nanotips, self-guiding, filamentation and mirrorless lasing during propagation of light in atmospheres. While extensive quantum mechanical and semiclassical calculations on strong-field ionization are well backed by sophisticated experiments, the existing scattered theoretical work aiming at a full quantitative understanding of strong-field excitation lacks experimental confirmation. Here we present experiments on strong-field excitation in both the tunneling and multiphoton regimes and their rigorous interpretation by time dependent Schrödinger equation calculations, which finally consolidates the seemingly opposing strong-field regimes with their complementary pictures. Most strikingly, we observe an unprecedented enhancement of excitation yields, which opens new possibilities in ultrafast strong-field control of Rydberg wave packet excitation and laser intensity characterization.
authors.affiliation: Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Zimmermann
authors.affiliation: Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Patchkovskii
authors.affiliation: Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany.|Department of Physics, Humboldt University, Newtonstrasse 15, 12489 Berlin, Germany.|Blackett Laboratory, Imperial College London, South Kensington Campus, SW7 2AZ London, United Kingdom.
authors.forename: M
authors.initials: M
authors.lastname: Ivanov
authors.affiliation: Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Eichmann