Spatial orientation of the azimuthal angle φ in the D-state for E = 10²V · m⁻¹ (blue solid line), E = 10⁴V · m⁻¹ (green dashed line), E = 10⁵ V · m⁻¹ (red dashed–dotted line): (a) simplified model for small θ and δ; (b) model of common approach Eq. (7) with boundary conditions (8).