Twisted electron impact elastic cross sections of polyatomic molecules: All active electron multicentered approach

Abstract

The methodology and computation of absolute elastic differential and integral (total) cross-sections of polyatomic molecules by twisted electron beam (Bessel Beam) impact is presented with CO2 as an example. The target molecule is modeled using multicentered wavefunctions with the correlation consistent quadruple zeta basis set cc-pVQZ and optimized by the post-Hartree-Fock Coupled Cluster CCSD method. The electron density is obtained as a function of spatial coordinates and is used to calculate the elastic form factor while considering the active role of all electrons in the molecule. Coulomb direct potentials are used for the interactions of the incident beam with all electrons and nuclei in the First Born Approximation. Orientation averaging of the differential cross-section is performed to mimic experimental situations. The cross sections are calculated at intermediate energies ranging from 300eV to 1keV. The proposed methodology could be applied to any polyatomic molecule. The interactions of Bessel beams (Twisted Electron Beam) with topological charges ml = 1, 2, and 3 are analyzed. The average over-impact parameters of the differential cross-sections representing the beam's interaction with a large number of uniformly transversely distributed molecules are also studied and presented. Finally, the molecules' Integral elastic cross-section (ICS) by plane waves and twisted beams is calculated and presented.