Microwave spectroscopy of high-Lhelium Rydberg states. II. The 10F–10Gand 10G–10Hintervals

The frequencies of the four strongest magnetic-fine-structure components of the 10F–10G and 10G–10H transitions in atomic helium have been measured to within a precision of a few kHz. The measurements are made with fast-beam microwave-optical techniques similar to previous measurements. Two significant experimental improvements are (1) the use of a new scheme to select a single magnetic-fine-structure component for careful study, and (2) improved control over systematic errors due to stray electric fields. The measured intervals can be combined with other measurements and with precise calculations of high-L states to yield absolute binding energies of the 10F and 10G states of helium with a precision of about 4 kHz (2×${10}^{\mathrm{-}13}$ a.u.). These energies are compared to calculations of the structure, and when combined with expected calculations, will give a high-precision test of the calculated structure of these states, including a 1% test of retardation effects.