Function ζ(ν) for different sets of q and ΔΠ₁ values representative of various evolutionary stages, obtained with the method illustrated in Fig. 1. Top: typical ΔΠ₁ values on the RGB, with different values of q, Δν = 8 μHz, and ΔΠ₁ = 70 s. Compared to high q, low q values correspond to deeper minima and ζ near to 1 for gravity-dominated mixed modes. Middle: Δν = 8 μHz, q = 0.15, and different values of ΔΠ₁ found on the RGB. All curves are very similar. Bottom: Δν = 8 μHz, q = 0.15, and different values of ΔΠ₁ found either on the RGB, or in the red clump. Even if large variations are seen in that case, the bijection (Eq. (8)) ensures a correction that is efficient enough to iterate the value of ΔΠ₁. The minimum and maximum values of ζ, respectively reached for pressure or gravity-dominated mixed modes, are plotted in dashed and dotted lines.