Fig. 1. KH potential defined in Eq. (3) for α0=13.5 a.u.^[93]

Fig. 2. Ground-state wave function of hydrogen atom varies with α0 in the KH frame^[82]

Fig. 3. Ionization rate of hydrogen atom varies with α0^[93]

Fig. 4. Schematic diagrams of temporal coherence for atomic stabilization^［78］. (a1)(a2) cosϕVt function curves; (b1)(b2) photoelectron momentum as a function of ejection time; The blue lines mark the ejection time of k=1.83 a.u. and k=1.78 a.u.

Fig. 5. Photoelectron momentum spectra of ground-state hydrogen atom in high-inernsity strong XUV laser pulse^[78]. (a) Photoelectron momentum spectrum calculated using TDSE under the electric dipole approximation; (b) photoelectron momentum spectrum calculated using TDSE with non-dipole corrections; (c) photoelectron momentum spectrum obtained from model calculations; (d) angular distribution of photoelectrons with an exit momentum of 1.83 a.u., corresponding to the white horizontal line in Fig. 5(a)-(c)

Fig. 6. Photoelectron momentum spectra of laser propagation along the y-axis directionin^[78]. (a) x-z plane; (b) y-z plane

Fig. 7. AT splitting in photoelectron energy spectra of He atom at three different photon energies^[167]. (a) Experimental measurement; (b) theoretical calculation

Fig. 8. Schematic diagram of dynamic AT splitting^[171]. (a) Photoelectron energy spectra of hydrogen atom varies with the time delay τ between the pump and the probe pulse, the photon energy of the pump pulse ω1=0.375 a.u., and the photon energy of the probe pulse ω2=1.3 a.u.; (b) population of the ground-state (TDSE) is compared with the delay-dependent photoelectron signal at E=0.8 a.u. (three probe pulse durations are shown); (c) AT splitting near E=0.8 a.u. is observed for the vertical cuts at τ=-10.4 a.u. and τ=74.8 a.u. in Fig. 8(a)

Fig. 9. Basic images of dynamic AT splitting. (a) Time-domain coherence; (b) frequency-domain coherence

Fig. 10. Photoelectron energy spectra of hydrogen atom in XUV laser pulses with photon energy 53.6 eV^[184]

Fig. 11. Photoelectron spectra of ground-state hydrogen and helium atoms in XUV laser pulses with different intensities and different pulse durations^[186]. (a)(b) Hydrogen atom; (c)(d) helium atom

Fig. 12. Joint photoelectron energy spectra for double ionization of helium from full-dimensional TDSE calculations^[79]. (a1)(a2)(a3) Fixed photon energy at 54.6 eV, pulse duration of 1 fs, with varying peak intensities; (b1)(b2)(b3) fixed peak intensity at 1×10¹⁹ W/cm², pulse duration of 1 fs, with varying photon energies; (c1)(c2)(c3) fixed peak intensity at 1×10¹⁹ W/cm², photon energy at 75 eV, with varying pulse durations

Fig. 13. Double ionization paths of He atom in a single XUV pulse^[79]

Fig. 14. Sequential two-photon ionization energy spectra of H atom by a Gaussian-shaped pulse with a pulse duration of 30 fs, photon energy of 10.20 eV, and peak intensity of 1.3×10¹³ W/cm^2[190]

Fig. 15. Photoionization spectra of the He atom computed for Gaussian-shaped pulses of 30 fs duration, two carrier frequencies of 1.500 a.u. (left) and 1.528 a.u. (right), and different peak intensities^[198]