Precision radio-frequency measurements of the high-LRydberg states of lithium

The n=10 G-to-H and H-to-I intervals in lithium atoms have been measured to an accuracy of approximately 10 parts per million. The experiment utilizes a beam of Rydberg lithium atoms produced via a resonant charge-exchange technique and the measurements were performed using precision rf spectroscopy coupled with a laser-excitation and Stark-ionization detection technique. The results are compared with recently published polarization-model calculations of the fine structure of lithium and with a hydrogenic model of its spin structure. With the availability of more precise theory, further tests of relativistic and QED effects in this simple three-electron atom will be possible. Such tests could shed light on the discrepancies found between similar high-precision measurement and theory in helium. The measured values are 338.4778(33), 341.4027(35), 108.4819(51), and 110.1566(54) MHz for the intervals 10${\mathit{G}}_{9/2}$ to 10${\mathit{H}}_{11/2}$, 10${\mathit{G}}_{7/2}$ to 10${\mathit{H}}_{9/2}$, 10${\mathit{H}}_{11/2}$ to 10${\mathit{I}}_{13/2}$, and 10${\mathit{H}}_{9/2}$ to 10${\mathit{I}}_{11/2}$, respectively.