Millimeter-wave spectroscopy of neutral mercury in Rydberg F states

To our knowledge, this is the first study to report the quantum defects of F31 and F33 highly-excited states of neutral mercury. The frequencies of 36 measured two-photon Rydberg–Rydberg 6snfFJ1,3→6s(n+1)fFJ1,3 transitions were fitted by Rydberg–Ritz formula to derive the quantum defect values. The transitions were driven from Rydberg singlet and triplet F levels selectively populated via two-step laser excitation scheme. The observed transitions spanned the frequency range 49–81 GHz and the range of the principal quantum number n=35−42. The details of the experiment are presented.