Hyperfine splitting of the 3 2S state of Li7 measured using Stark spectroscopy of Rydberg states

Precision measurements of Rydberg Stark levels of Li7 atoms are used to determine the 3 2S hyperfine separation, ΔEhf(3 2S). Three diode lasers at λ=671 nm, 813 nm, and 633 nm excite Li7 atoms to n=15 sublevels in the presence of an electric field. Photoionization resonances at fields below the saddle point are used in conjunction with matrix diagonalization calculations to determine the binding energy of levels excited from each 3 2S hyperfine sublevel. The difference between the two fitted binding energies excited from 3 2S (F=1) and 3 2S (F=2) yields 189.36(43) MHz for ΔEhf(3 2S;7Li).