Propagation diagram for a 1.3   M_⊙ post-main-sequence model with an ℓ = 1 avoided crossing. The Brunt-Väisälä frequency (black solid line) can be separated in two contributions: the part linked to the temperature stratification (long-dashed blue line) and the one linked to the gradient of mean molecular weight (red solid line). The Lamb frequency for ℓ = 1 modes is represented by the black dashed line. The shaded area indicates the evanescent zone. The radii r₁ and r₂ correspond to the turning points of the g-mode cavity and r₃ the turning point of the p-mode cavity.