Rotational splitting of multiplets

What you are seeing: a degenerate $(2\ell+1)$-fold mode splits into a multiplet under rotation with $\Omega$. p-modes (Ledoux $C \to 0$) split fully as $m\Omega$; g-modes split by $m(1 - 1/\ell(\ell+1))\Omega$ for slow rigid rotation.