Complete characterization of double photoionization processes

We analyze correlated photoelectron spectra of single-photon two-electron ionization [double photoionization (DPI)] of helium to reconstruct the phase of the spectral amplitude of this process. The phase can be reconstructed reliably in a wide range of photoelectron momenta, thus allowing one to retrieve information about the wave function of the DPI process and its temporal evolution. Our simulation indicates that the proposed phase reconstruction technique can be applied in experiment to trace dynamics of the DPI process with attosecond precision.

Figure 1

Distribution $|f(k_x,k_z)|{}^2$ for DPI of helium driven by the XUV pulse alone (top left), and in the presence of the IR field for $\Delta =6$ (top right), $\Delta =28T$(bottom left), and $\Delta =50T$ (bottom right). $T$ is the optical cycle for the XUV field.

Figure 2

Distribution $|f(k_x,k_z)|{}^2$ for DPI of He in the presence of XUV and IR fields produced by Eq. (10). The time delay between the XUV and IR pulses is is $\Delta =6T$ (left) and $\Delta =50T$ (right).

Figure 3

Distribution $|f(k_x,k_z)|{}^2$ as a function of $k_z$ for the fixed value $k_x=0.9$ a.u. is shown for various delays between the XUV and IR pulses. $\Delta =6T$ (top left), $\Delta =28T$ (top right), $\Delta =50T$ (bottom left), and $\Delta =74T$ (bottom right). The solid (red) line displays the TDSE calculation, the dashed (green) line corresponds to the CVA result.

Figure 4

Phase of the amplitude $f(k_x,k_z)$ relative to the phase of $f(k_x,-1)$ (left panels) and $f(k_x,0.6)$ (right panels) for $k_x=0.9$ a.u. (upper panels) and $k_x=0.4$ a.u. (lower panels). Results given by the TDSE calculation for DPI driven by the XUV pulse alone are shown by the (red) solid line. Results obtained by using Eq. (10) are displayed by the (green) dashed line.