Stuttgart 2012 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 13: Photoionization
A 13.4: Vortrag
Dienstag, 13. März 2012, 11:15–11:30, V55.01
High-resolution time-resolved transient-absorption spectroscopy with continuous VUV spectrum around the first ionisation threshold of helium — •Andreas Kaldun, Christian Ott, Philipp Raith, Kristina Meyer, Martin Laux, Yizhu Zhang, and Thomas Pfeifer — Max-Planck Institut für Kernphysik, Heidelberg
Attosecond time-resolved spectroscopy on helium in the energy range around the first ionization threshold has been performed (see e.g. [1, 2]) however without simultaneous access to a broad energy range at high spectral resolution. In our work, we use a continuous coherent vacuum-ultra-violet (VUV) high-harmonic generation (HHG) spectrum together with our high-resolution VUV spectrometer to resolve the helium absorption lines of the transitions corresponding to the 1s2 ↔ 1snp states with n ranging from 2 up to 9. By spatially and temporally superimposing the VUV-pulse at variable time delays with a moderately intense few-cycle near-visible (VIS) pulse (precission measured interferometrically to be 10 as) we observe a switching from absorption to emission in the measured spectra. The Data were recorded by scanning the time delay in steps of 170 as and for different VIS laser intensities. Characteristic energy shifts of the resonance lines in the temporal overlap region of VUV and VIS pulse are identified and provide information about the dipole coupling of these excited states with surrounding bound as well as continuum states.
[1] Holler et al. PRL 106 , 123601 (2011)
[2] Mauritsson et al.PRL 105 , 053001 (2010)