Measurements ofG-HandH-Ifine-structure intervals inn=7,9, and 10 helium Rydberg states

We have made measurements of the $7G-H,$ $7H-I,$ $9G-H,$ $9H-I,$ and the $10G-H$ intervals in helium. These measurements are in good agreement with theoretical calculations up to the level of about 1 kHz precision. This confirms the importance of retardation to the intervals with about 1% precision. At the 1 kHz level, however, systematic discrepancies are seen which cannot be accounted for by suggested additional retardation corrections.