High-resolution spectroscopy of Dy-162 Rydberg levels

Highly excited Rydberg states of lanthanides are a promising, yet largely unexplored, playground for quantum studies. Here we report on the first high-resolution spectroscopy of 162Dy obtained by two-color trap depletion spectroscopy in a magneto-optical trap. The absolute excitation frequency of over 700 states with effective principal quantum number 21 ≤ n ≤ 130 is measured with an accuracy of 20 MHz. Most states are assigned to the eight different series converging to the first 4f10(5I8)6s(2S1/2) 6I17/2 ionization potential. This energy is measured at EIP = 47 901.8265 ± 0.0008 cm−1, improving the precision of the literature value by over an order of magnitude. A multichannel-quantum-defect-theory approach is used to benchmark and refine the assignments and to characterize six observed perturbing states belonging to higher ionization limits. These results pave the way for using dysprosium in Rydberg-based quantum architectures, leveraging the unique properties arising from its complex electronic structure. They also represent a compelling benchmark for ab initio calculations of open-shell atomic systems.