Figure 1

The excitation scheme of He $1s^2$ ${}^{1}S$ by an intense short Gaussian pulse with ω $=$ 60.17 eV, implemented in the present SSEA computations. Apart from the one-photon direct transition to the He (${}^{\prime }2s2p{}^{\prime }$, $1s\varepsilon p$) ${}^1{P}^o$ stationary state, higher order transitions involving the depicted continua have been included in the expansion.Reuse & Permissions

Figure 2

(a) Quantitative behavior of the main maximum of the reduced differential ionization probability, Eq. (5), for $t_{\mathrm{FWHM}}$ $=$ 2.4 fs, as a function of the pulse peak-intensity, $I$. (b) As in panel (a), for $t_{\mathrm{FWHM}}$ $=$ 10.9 fs. (c) As in panel (a), for $t_{\mathrm{FWHM}}$ $=$ 25.4 fs. (d) As in panel (a), for $t_{\mathrm{FWHM}}$ $=$ 50.8 fs. (e) As in panel (a), for $t_{\mathrm{FWHM}}$ $=$ 100.4 fs. Comparison of the results of these figures demonstrates quantitatively the distinct effect of the pulse duration on the breakdown of FOTDPT for this problem, in conjunction with the dependence on the pulse intensity.Reuse & Permissions