The basic initial step of rescattering is the tunnel ionization of the electron from the atom or the molecule. The intensity of the returning electron flux critically depends on the ionized orbitals as well as their orientations with respect to the laser polarization direction in the molecular case. The knowledge of the rescattering flux may lead to absolute differential electron-molecular ion collision cross sections in laser-induced electron diffraction (LIED). This flux cannot be measured directly and has to be inferred from models. These models are tested in aligned molecules using a first aligning pulse in the 1012–1013 Wcm-2 intensity range for which ionization is negligible, and an ionization pulse in the 1014 Wcm-2 intensity range. The revivals of the ion signals (for example in the left and right figures for respectively CO2 and C2H2) are analyzed using ionization rates from tunnel ionization (TI strong field approximation (SFA) models, and in the future from the time-dependent Schrödinger equation (TDSE).
Collaboration: ISMO (Université Paris-Saclay)