Polarization-dependent differential cross-section (1/σ_T) dσ₁₁/d cos θ′ as a function of photon energy E = ℏω for a set of incident angles θ and scattered angles θ′. The set of angles is 0, 30, 60, and 90 degrees, with θ changing vertically and θ′ horizontally. The red solid lines are produced from the expression of Sina (1996), while the black dashed ones are produced from the expression of Harding & Daugherty (1991). In all cases, the resonant frequency is given by expression (7). The vertical line indicates the resonant frequency ω_r, which for θ ≠ 0 is smaller than ω_c. Here, E_c = ℏω_c = 15.33 keV.