Observing Rydberg Atoms to Survive Intense Laser Fields

Abstract

The idea of atoms defying ionization in ultrastrong laser fields has fascinated physicists for the last three decades. In contrast to extensive theoretical work on atoms stabilized in strong fields only few experiments limited to intermediate intensities have been performed. In this work we show exceptional stability of Rydberg atoms in strong laser fields extending the range of observation to much higher intensities. Corresponding field amplitudes of more than 1 GV/cm exceed the thresholds for static field ionization by more than 6 orders of magnitude. Most importantly, however, is our finding that a surviving atom is tagged with a measure of the laser intensity it has interacted with. Reading out this information removes uncertainty about whether the surviving atom has really seen the high intensity. The experimental results allow for an extension of the investigations on the stabilization and interaction of a quasifree electron with a strong field into the relativistic regime.

Quantum dynamics of atomic Rydberg excitation in strong laser fields

“…The model is also applied to the investigation of RSE of He and Xe atoms. For He, we reproduce the experimentally observed distributions of the principal quantum number of the Rydberg states [9,21]. For Xe, we present to our knowledge the first measurements of RSE for 800-nm laser wavelength that display the peak structure.…”

Strong-field assisted extreme-ultraviolet lasing in atoms and molecules

“…This ionization process takes place over multiple laser cycles. Second, the IR field populates excited electronic states through frustrated tunneling [33][34][35]. These excited states experience stabilization and oscillate as a nearly free Kramers-Henneberger-like quasi-bound wavepacket in the IR driving field [31,[36][37][38].…”

“…We have, for the first time, identified a clear gain mechanism in HHG at the single atom level: the strong IR driving pulse creates an effective population inversion between the IR depleted ground state and the laser dressed excited states, enabling intra IR-pulse XUV lasing between such virtual states and the ground state. The former are populated by the frustrated tunneling mechanism [33][34][35]. For the hydrogen atom, our results are based on the numerically exact solution of the time-dependent Schrödinger equation, combined with a rigorous evaluation of the XUV absorption cross sections.…”

Time-resolved high harmonic spectroscopy of dynamical symmetry breaking in bi-circular laser fields: the role of Rydberg states

“…In general, the emergence of strong, symmetry forbidden, lines in high harmonic spectra is a tell-tale sign of symmetry breaking induced by the underlying attosecond electronic [54,55] or vibronic dynamics [56][57][58]. Specifically, we show that symmetry forbidden lines in high harmonic spectra generated in bi-circular fields are sensitive to frustrated tunnel ionization [59][60][61][62][63][64] and the presence of strongly laser-driven Rydberg states, the so-called 'bound states of the free electron' [65], which are able to survive intense laser fields [60][61][62][63][64][66][67][68][69] even when the ground state of the neutral is completely depleted [61,70].…”