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A: Fachverband Atomphysik
A 40: Strong laser fields - III
A 40.5: Talk
Thursday, March 8, 2018, 15:30–15:45, K 2.019
Suppression of strong-field effects in photoionization of ultracold alkali atoms — •Tobias Kroker1,2, Philipp Wessels1,2, Bernhard Ruff1,2, Klaus Sengstock1,2, Markus Drescher1,2, and Juliette Simonet1,2 — 1Zentrum für Optische Quantentechnologien (ZOQ), Luruper Chaussee 149, 22761 Hamburg — 2The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg
We investigate experimentally the ionization of genuine single active electron atoms in strong light fields accessing a regime where the Keldysh parameter is close to unity and nominally all transition scenarios of multiphoton-, tunnel-, and over-the-barrier ionization can take place. Surprisingly, we observe a clear dominance of multiphoton ionization even at high peak intensities exceeding the over-the-barrier-ionization threshold.
Our fully quantitative approach relies on exposing trapped ultracold 87Rb atoms to intense femtosecond laser pulses. Such targets indeed allow for the exact determination of atom numbers and densities and thus the atomic loss fraction can be directly measured.
This novel methodology enables the extraction of absolute ionization probabilities and cross-sections for testing the validity of theoretical models under debate in the so-called transitional non-adiabatic tunneling regime.