Ab initio Calculation of the Double Ionization of Helium in a Few-Cycle Laser Pulse Beyond the One-Dimensional Approximation

We present ab initio computations of the ionization of two-electron atoms by short pulses of intense linearly polarized Ti:sapphire laser radiation beyond the one-dimensional approximation. In the model the electron correlation is included in its full dimensionality, while the center-of-mass motion is restricted along the polarization axis. Our results exhibit a rich double ionization quantum dynamics in the direction transversal to the field polarization, which is neglected in the previous models based on the one-dimensional approximation.

Figure 1

Shown is the expectation value $⟨\rho ⟩$ (solid line) as function of time along with the electric field (dotted line) at $\lambda =800\mathrm{nm}$ and $I_0=2.6\times {10}^{15}\mathrm{W}/{\mathrm{cm}}^2$.

Figure 2

Probability distributions at different time instants between $t=1T$ and $t=2T$: (a) $t=(1+6/16)T$, (b) $t=(1+10/16)T$, (c) $t=(1+14/16)T$, and (d) $t=(1+15/16)T$. Left hand column: $(Z,\rho )$ distributions, right hand column: $(Z,z)$ distributions.

Figure 3

(a) Slices of the three-dimensional probability distribution. The horizontal plane corresponds to $\rho =0$, vertical planes are planes at $Z=0$ and at $z=0$. (b) Enlarged view, which shows the interference patterns in the single and double ionization region. This snapshot is taken at $t=(1+15/16)T$.

Figure 4

Distribution of the center-of-mass momentum along the polarization direction in the double ionization region.