Measurement Of The Strontium Triplet Rydberg Series By Depletion Spectroscopy Of Ultracold Atoms

We report on the atom loss spectroscopy of strontium Rydberg atoms in a magnetooptical trap, using a two-photon excitation scheme through the intermediate state 5s5p P-3(1). Energies of the 5sns S-3(1) and 5snd D-3(1,2) Rydberg series of Sr-88 in the range 13 <= n <= 50 are determined with an absolute accuracy of 10 MHz, including the perturbed region where the 5 snd D-3(2) series couples to the 5snd D-1(2) series. This represents an improvement by more than two orders of magnitude compared to previously published data. The quantum defects for each series are determined using the extended Rydberg-Ritz formula in the range where there is no strong perturbation. A value of 1 377 012721(10) MHz for the first ionization limit of Sr-88 is extracted.