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Abstract Non-linear photoionization of molecules in the 10–50 eV range is a prerequisite for pump-probe measurements with sub-femtosecond resolution, but hitherto has been limited to femtosecond resolution, low repetition rate and… Click to show full abstract
Abstract Non-linear photoionization of molecules in the 10–50 eV range is a prerequisite for pump-probe measurements with sub-femtosecond resolution, but hitherto has been limited to femtosecond resolution, low repetition rate and high photon flux laser systems. We demonstrate two-photon single ionization of helium atoms using 100 pJ, 1.34 fs pulses (main peak FWHM = 680 as) at 1 kHz repetition rate with a central photon energy of 19.6 eV. We obtained an exponent of 2.27 ± 0.21 for the intensity dependence of the signal and a two-photon ionization cross-section of 5.0 ± 0.5 × 10 −50 cm4 s. Our work opens the possibility of attosecond pump-probe measurements of ultrafast molecular processes.
Journal Title: Chemical Physics Letters
Year Published: 2017
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