## Partial double differential cross sections for the Compton scattering equation (2) of a linearly polarized (perpendicular to the plane of scattering, ⊥) x-ray photon by the Mn atom without the autoionization channel equation (7) (theory of this paper): *n*_{1}*l*_{1} = 3s (dash dotted curve), 3p (dashed curve), 3d (dotted curve), 4s (solid curve)

**Figure 2.** Partial double differential cross sections for the Compton scattering equation (2) of a linearly polarized (perpendicular to the plane of scattering, ⊥) x-ray photon by the Mn atom without the autoionization channel equation (7) (theory of this paper): *n*_{1}*l*_{1} = 3s (dash dotted curve), 3p (dashed curve), 3d (dotted curve), 4s (solid curve). ω_{1} = 5 keV (a), 8 keV (b), θ = 90°, Γ_{beam} = 10 eV. The contribution of the deep 1s, 2s and 2p shells is defined outside of energy scales in the figure (ω_{2} ≤ 4.35 keV (a) and ω_{2} ≤ 7.35 keV(b)).

**Abstract**

The existence of the giant autoionization resonance in a double differential cross section of the nonresonant Compton scattering of hard x-ray photons by an atom with an open shell in the ground state is theoretically predicted on the example of the Mn atom. The developed mathematical formalism is based on the multiconfiguration generalization of the nonrelativistic quantum theory of contact inelastic scattering of a photon by an atom, constructed in the work by Hopersky and Nadolinsky (2012 *J. Exp. Theor. Phys.* **115** 402).