1. Towards XUV pump-probe experiments in the femtosecond to sub-femtosecond regime: New measurement of the helium two-photon ionization cross-section
- Author
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Paloma Matia-Hernando, Jon P. Marangos, D. Greening, T. Barillot, D. J. Walke, John W. G. Tisch, Leszek J. Frasinski, Tobias Witting, Engineering & Physical Science Research Council (EPSRC), and Commission of the European Communities
- Subjects
HE ,Attosecond ,PHASE ,General Physics and Astronomy ,Physics::Optics ,Photoionization ,Photon energy ,Physics, Atomic, Molecular & Chemical ,01 natural sciences ,law.invention ,Atmospheric-pressure laser ionization ,010309 optics ,law ,Ionization ,PHOTOIONIZATION ,10 Technology ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,ABSORPTION ,PHOTOELECTRON ,Physics::Atomic Physics ,Physical and Theoretical Chemistry ,010306 general physics ,ATTOSECOND PULSE-TRAIN ,SCALE ,Physics ,ELECTRON DYNAMICS ,Science & Technology ,02 Physical Sciences ,Chemical Physics ,Chemistry, Physical ,Laser ,CHARGE MIGRATION ,Chemistry ,RESOLUTION ,Femtosecond ,Physical Sciences ,Atomic physics ,03 Chemical Sciences ,Ultrashort pulse - 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.
- Published
- 2017