Many-Electron Dynamics of a Xe Atom in Strong and Superstrong Laser Fields

We report on detailed investigations of ionization dynamics of a Xe atom exposed to intense 800-nm pulses of 20-fs duration in the extensive intensity range from ${10}^{13}–{10}^{18}\mathrm{W}/{\mathrm{cm}}^2$. Ion yields of ${\mathrm{Xe}}^{+}–{\mathrm{Xe}}^{20+}$ were observed as a function of laser intensity and compared with the results from a single active electron based Ammosov-Delone-Krainov model. Unexpected ionization probabilities for lower charge states and no interplay between the inner and outer shells by screening are inferred. Suppression of nonsequential ionization towards higher intensity and few optical cycle regimes is also proved.

Figure 1

Comparison of experiment and theory for tunneling ionizations in Xe as a function of laser intensity. Experiment: $\lambda =800\mathrm{nm}$; $\tau =20\mathrm{fs}$. Theory: the quasiclassical tunneling theory (solid curves) with no shift in laser intensity. Three sets of intensity scans are indicated: (1) $6\times {10}^{13}–9\times {10}^{15}\mathrm{W}/{\mathrm{cm}}^2$; (2) $6\times {10}^{14}–1.5\times {10}^{17}\mathrm{W}/{\mathrm{cm}}^2$; (3) $1\times {10}^{17}–1.5\times {10}^{18}\mathrm{W}/{\mathrm{cm}}^2$.

Figure 2

Comparison of experiment and theory for tunneling ionizations in Xe as a function of laser intensity that is identical to Fig. 1, but with shift of the theoretical curves along the laser intensity scale to match the experimental data. The solid curves (theory) represent the “best fit” to the data based on the shift factor listed in Table .