  The impacts of both exchange interaction and electron correlation, as well as
their combined impact, on electron elastic scattering off a semifilled shell
Mn(...$3d^{5}$$4s^{2}$, $^{6}S$) atom are theoretically studied in the electron
energy range of $\epsilon= 0-25$ eV. Corresponding elastic scattering phase
shifts $\delta_{\ell}(\epsilon)$ as well as partial $\sigma_{\ell}(\epsilon)$
and total $\sigma(\epsilon)$ cross sections are found to be subject to a strong
correlation impact. The latter is shown to be drastically different for
oppositely spin-polarized scattered electrons, in some cases, thereby bringing
significant differences in corresponding $\delta_{\ell}(\epsilon)$s,
$\sigma_{\ell}(\epsilon)$s, and $\sigma(\epsilon)$s between said electrons.
This is proven to be an inherent features of electron scattering off a
semifilled shell atom in general. Electron correlation is accounted for in the
framework of the self-energy part $\Sigma$ of the Green function of a scattered
electron concept. The latter is calculated both in the second-order
perturbation theory in the Coulomb interelectron interaction as well as beyond
it by solving the Dyson equation for $\Sigma$. The significance of the "Dyson"
correlation corrections in e$^{-}+$Mn scattering is unraveled. They are shown
to aggravate noticeably the inherent differences between elastic scattering
phase shifts and cross sections of spin-up ($\uparrow$) and spin-down
($\downarrow$) polarized electrons scattered off a spin-polarized Mn atom, in
some cases. In particular, the existence of a narrow resonant maximum in
$\sigma^{\downarrow}(\epsilon)$ near $\epsilon \approx 8$ eV but the absence of
such in $\sigma^{\uparrow}(\epsilon)$ in e$^{-}+$Mn scattering is predicted.
