Energies and Relativistic Corrections for the Metastable States of Antiprotonic Helium Atoms

We present accurate results for the energy levels of antiprotonic helium atoms with the relativistic and QED corrections of order α⁴mc² taken into account. These results reduce the discrepancy between theory and experiment to about 5--10 ppm and rigorously confirm Condo's model of metastability for the long-lived fraction of antiprotonic helium. The present level of precision enables the unambiguous ascription of quantum numbers to all of the transition lines observed so far.