LaserDriven Recollisions under the Coulomb Barrier
Abstract
Photoelectron spectra obtained from the ab initio solution of the timedependent Schrödinger equation can be in striking disagreement with predictions by the strongfield approximation (SFA), not only at low energy but also around twice the ponderomotive energy where the transition from the direct to the rescattered electrons is expected. In fact, the relative enhancement of the ionization probability compared to the SFA in this regime can be several orders of magnitude. We show for which laser and target parameters such an enhancement occurs and for which the SFA prediction is qualitatively good. The enhancement is analyzed in terms of the Coulombcorrected action along analytic quantum orbits in the complextime plane, taking soft recollisions under the Coulomb barrier into account. These recollisions in complex time and space prevent a separation into subbarrier motion up to the "tunnel exit" and subsequent classical dynamics. Instead, the entire quantum path up to the detector determines the ionization probability.
 Publication:

Physical Review Letters
 Pub Date:
 December 2016
 DOI:
 10.1103/PhysRevLett.117.243003
 arXiv:
 arXiv:1608.03844
 Bibcode:
 2016PhRvL.117x3003K
 Keywords:

 Physics  Atomic Physics;
 Quantum Physics
 EPrint:
 5 pages, 2 figures, RevTeX 4.1