Repulsive potentials and their difference. Top: potential energy V of the repulsive states of Lyman-α (dashed black curve), Balmer-α (dashed red curve), and Balmer-β (blue curve). Bottom: difference potential ΔV(R) for the Lyman-α transition X → C (dashed black curve), for the Balmer-α transition C → 6²Σ⁺ (dashed red curve), and for the Balmer-β transitions C → 10²Σ⁺ (blue curve).