def _sigma_ee_nonrel(self, gam, eps):
        """
        Eq. A5 of Baring et al. (1999)
        Use for Ee < 2 MeV
        """
        s0 = 4 * r0 ** 2 * alpha / (15 * eps)
        x = 4 * eps / (gam ** 2 - 1)
        sigma_nonrel = s0 * self._F(x, gam)
        sigma_nonrel[np.where(eps >= 0.25 * (gam ** 2 - 1.0))] = 0.0
        sigma_nonrel[np.where(gam * np.ones_like(eps) < 1.0)] = 0.0
        return sigma_nonrel / mec2_unit
Eq. A5 of Baring et al. (1999)
        Use for Ee < 2 MeV