Abstract
We report a theoretical investigation of low-energy electron and positron scattering by the lysine molecule. The calculations were performed using the Schwinger multichannel method with different levels of approximation for each projectile. The static-exchange (SE) and static-exchange plus polarization (SEP) approximations were used for electrons, while the static plus polarization (SP) approximation was used for positrons. Our results for electron scattering show a π* resonance centered at 3.95 eV for SE and 2.73 eV for SEP in the integral cross section, as well as a large structure around 11.0 eV for SE and 9.0 eV for SEP, which may be associated with overlapping σ* resonances. For comparison purposes, since there are no theoretical or experimental cross sections available in the literature, a semiempirical relation was employed to estimate the value of the π* resonance. We also compared the results obtained for electron and positron scattering, showing similar behavior at very low energy due to the dipole interaction and approximately the same order of magnitude from 2 to 6 eV. Differential cross sections for both projectiles also exhibit the same dominant wave pattern. To investigate the connection between the resonance and the dissociative electron attachment (DEA), we calculated threshold energies for hydrogen loss from different sites in the molecule, identifying a low-energy channel (1.85 eV) consistent with previous DEA studies on similar systems. Furthermore, excited electronic states of lysine were obtained by using time-dependent density functional theory (TDDFT), providing additional insight into possible Feshbach-type DEA pathways. These results represent the first theoretical study of scattering processes involving electrons and positrons with lysine and offer a foundation for future experimental and computational investigations.