Triple differential cross-section for Laser-assisted (e,2e) process on H2O molecule by Plane and Twisted electrons Impact

Twisted electron-impact single ionization ((e,2e) process) of water molecule is theoretically studied in the presence of an external laser field. Calculations have been performed in the framework of the first Born approximation in coplanar asymmetric geometry. The wave functions for the fast (incident/scattered) electron and the ejected electron are described by the Volkov and Coulomb–Volkov wave functions respectively which take into account the interaction of the laser field with incident/scattered and ejected electrons respectively. We calculate the triple differential cross section (TDCS) corresponding to the laser-assisted (e,2e) process for different orientations of the linearly polarized laser field. We describe the molecular state of H₂O by the linear combination of atomic orbitals (self-consistent field LCAO method). The angular profile of the TDCS for plane wave electrons is strongly modified by the laser field compared to that of without laser field. However, for the twisted electrons with laser field the angular distribution is slightly changed from those of without laser field. We study the angular distribution of TDCS for laser field polarization parallel to the incident momentum (${\varepsilon }_0$ $\parallel$ $k_i$), parallel to momentum transfer (${\varepsilon }_0$ $\parallel$ $\Delta$) and perpendicular to the momentum transfer (${\varepsilon }_0$ $\perp$ $\Delta$) and we observe that the ${\varepsilon }_0$ $\parallel$ $\Delta$ has the highest magnitude of TDCS. For the orientations ${\varepsilon }_0$ $\parallel$ $k_i$ and ${\varepsilon }_0$ $\perp$ $\Delta$, the laser-assisted plane wave studies shows oscillatory nature of TDCS but for the orientation ${\varepsilon }_0$ $\parallel$ $\Delta$ we observe only recoil peak for $p-like$ character orbitals and dual peak, a recoil and binary peaks for the $s-like$ character orbital. For laser-assisted twisted electron beam we observe two peaks a forward and backward peaks for all three orientations of laser-field polarization.