Theoretical Femtosecond Physics by Frank Grossmann

Author:Frank Grossmann
Language: eng
Format: epub, pdf
Publisher: Springer International Publishing, Cham

4.4.2 Low-Energy Structure

In an experimental study of electron emission on rare gas atoms, using 40 fs laser pulses with 630 nm central wavelength and peak intensities up to 4.4 10 W/cm, the results displayed in Fig. 4.23 have been found. The sharp ATI peaks are blurred into a continuous distribution at this high laser intensity and a plateau in the generation of the photo-electrons builds up (see inset in Fig. 4.23), which is most clearly visible for Ar and Xe gases [47]. It was lateron shown that the cutoff of this so-called ATI plateau is at around 10 [48], because this is the maximal energy that an electron can acquire after recollision (see also Fig. 4.22).

A surprising detail in the photo-electron emission was measured in the forward direction along the laser polarization axis for atoms (and also molecules) irradiated by long wavelength lasers (m) such that the Keldysh parameter is well below unity [49]. On top of the prediction of the strong-field KFR approximation, a maximum is located at low energies, see Fig. 4.23. This maximum has been dubbed “low-energy structure” (LES).

Fig. 4.23Low-energy structure (LES) in photo-electron yield under 150 TW/cm, 2 m pulses with on top of the strong field (KFR) prediction in the photo-electron spectrum of atomic argon and two molecular species. The inset shows a wider energy range with the recollision induced ATI plateau [49]. is the high energy limit at which a break in the slope of the yield curve exists

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