That's a useful article, which includes a more mundane example of "forbidden" light: "Phosphorescent glow-in-the-dark materials, which absorb light and form an

That's a useful article, which includes a more mundane example of "forbidden" light: "Phosphorescent glow-in-the-dark materials, which absorb light and form an excited state whose decay involves a spin flip, and is therefore forbidden by electric dipole transitions. The result is emission of light slowly over minutes or hours."