Freiburg 2024 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 19: Precision Spectroscopy of Atoms and Ions II (joint session A/Q)
A 19.5: Vortrag
Mittwoch, 13. März 2024, 12:00–12:15, HS 1098
Characterization of an XUV Frequency Comb by Spectroscopy of Rydberg States — •Lennart Guth, Jan-Hendrik Oelmann, Tobias Heldt, Nick Lackmann, Janko Nauta, Thomas Pfeifer, and José R. Crespo López-Urrutia — Max-Planck-Institut für Kernphysik, Heidelberg, Germany
We aim to exploit ultra-narrow transitions in highly charged ions (HCIs) for novel frequency standards and fundamental physics studies. Due to the strong binding of electrons to the nucleus, these transitions are in the extreme ultraviolet (XUV), where narrow-bandwidth laser sources are not commercially available. Therefore, we have built an XUV frequency comb that transfers the coherence of a near-infrared (NIR) comb to the XUV by high harmonic generation (HHG) [1]. To achieve the required intensity (Ipeak > 1013 W/cm2) for HHG, we amplify an NIR comb to 80 W in a chirped pulse fiber amplifier and resonantly overlap them in a passive femtosecond enhancement cavity. Our system generates harmonics up to 40 eV and with µW of power each.
We will give an overview of the current status of our experiment and discuss our plans for resonance-enhanced two-photon ionization to resolve the XUX-comb structure. In our spectroscopy approach, we excite argon with one photon from a referenced comb tooth of the 13th harmonic, followed by ionization with a narrow-bandwidth NIR cw-laser. We record the momentum of the released electrons using the velocity map imaging technique to ensure the correct Rydberg state. [1]J. Nauta et al., Opt. Lett. 45, 2156-2159 (2020)
Keywords: High-Harmonic-Generation; femtosecond; frequency comb spectroscopy; high-repetition rate; enhancement cavity