Multiphoton transitions for delay-zero calibration in attosecond spectroscopy
The exact delay-zero calibration in an attosecond pump-probe experiment is important for the correct interpretation of experimental data. In attosecond transient absorption spectroscopy the determination of the delay-zero exclusively from the experimental results is not straightforward and may introduce significant errors. Here, we report the observation of quarter-laser-cycle (4ω) oscillations in a transient absorption experiment in helium using an attosecond pulse train overlapped with a precisely synchronized, moderately strong infrared pulse. We demonstrate how to extract and calibrate the delay-zero with the help of the highly nonlinear 4ω signal. A comparison with the solution of the time-dependent Schrödinger equation is used to confirm the accuracy and validity of the approach. Moreover, we study the mechanisms behind the quarter-laser-cycle and the better-known half-laser-cycle oscillations as a function of experimental parameters. This investigation yields an indication of the robustness of our delay-zero calibration approach.
Publication Source (Journal or Book title)
New Journal of Physics
Herrmann, J., Lucchini, M., Chen, S., Wu, M., Ludwig, A., Kasmi, L., Schafer, K., Gallmann, L., Gaarde, M., & Keller, U. (2015). Multiphoton transitions for delay-zero calibration in attosecond spectroscopy. New Journal of Physics, 17 https://doi.org/10.1088/1367-2630/17/1/013007