I skimmed the article looking for something about the spectroscopy of antiprotonic helium. I’d assume that the spectroscopy of such an atom is very different

I skimmed the article looking for something about the spectroscopy of antiprotonic helium. I’d assume that the spectroscopy of such an atom is very different from normal helium but the article says nothing about how the spectroscopy is different or if the spectroscopy observed is what we expect (thinking of anti Hydrogen here). The article does point to Helium made from a pion though where the atoms spectroscopy was observed.