Energy quantization in double ioinization in strong laser fields
Final Report Abstract
In brief: we consider the project very successful, as we have achieve both our goals: 1. To demonstrate the quantization of the energy in the two electron continuum of Helium ionized by a strong laser pulse. 2. For the first time shown experimentally the long predicted selection rules. We consider this a major scientific achievement as this shows impact of parity and angular momentum quantization in the strong field context, which is otherwise often discussed in classical terms. In more detail the results are, however, puzzling and not completely explained. In particular, we find that for Helium not only the sum energy of both emitted electrons is quantized, but also the energy of the individual electrons. This is surprising as one would have expected, that the two electrons can share the absorbed energy freely, leading to a smooth distribution. This feature is unexplained and remains a challenge to theory. Our project yielded the first fully differential data on strong field double ionization of Helium. i.e. we can select any number of absorbed photons, show how the excess energy is shared among the electrons and then plot the joint angular distribution of this fully entangled two body state. On this level of detail, current theory codes are not fully converged at all angles as we have learned from collaboration with our theory colleagues. Thus, our fully differential rates provide a benchmark for all future theoretical work. Our experiment brings the studies of strong field double ionization finally to the ultimate level of fully differential rates, which have been reached for the single photon process in 1993 by the pioneering work of Volker Schmidt (Freiburg). The importance of this step lies in the fact, that Helium is the only system for which one can hope, that ab initio theory will become available also on this full level of detail, which is testable only by such complete experiments.
Publications
- (2018) Timing Recollision in Nonsequential Double Ionization by Intense Elliptically Polarized Laser Pulses. Physical review letters 120 (22) 223204
Kang, H.; Henrichs, K.; Kunitski, M.; Wang, Y.; Hao, X.; Fehre, K.; Czasch, A.; Eckart, S.; Schmidt, L. Ph H.; Schöffler, M.; Jahnke, T.; Liu, X.; Dörner, R.
(See online at https://doi.org/10.1103/PhysRevLett.120.223204) - Observation of Electron Energy Discretization in Strong Field Double Ionization. Phys. Rev. Lett., 111 (2013) 113003
K. Henrichs, M. Waitz, F. Trinter, H. Kim, A. Menssen, H. Gassert, H. Sann, T. Jahnke, J. Wu, M. Pitzer, M. Richter, M.S. Schöffler, M. Kunitski, and R. Dörner
(See online at https://doi.org/10.1103/PhysRevLett.111.113003) - Doppelionisation in starken Feldern mit einer Wellenlänge von 400 nm. Dissertation, Universität Frankfurt am Main 2017
Kevin Henrichs
- Experimental Evidence for Selection Rules in Multiphoton Double Ionization of Helium
K. Henrichs, S. Eckart, A. Hartung, D. Trabert, J. Rist, H. Sann, M. Pitzer, M. Richter, H. Kang, M. S. Schöffler, M. Kunitski, T. Jahnke, and R. Dörner
