Spectroscopy of the Rydberg states of neutral ytterbium
Henri Lehec (Laboratoire Aimé Cotton, Orsay, France)

Rydberg atoms offers an ideal platform for the study of strongly interacting systems. However, usual techniques for imaging or trapping atoms are unavailable in alkali Rydberg atoms. The aim of this experiment is to optically manipulate atoms in Rydberg states using a divalent atom: ytterbium. We present our results of laser and microwave spectroscopy of highly excited Rydberg levels of ytterbium. We have improved the precision over previous absolute measurements by two or more orders of magnitude, now reaching around 10 MHz, which opens new perspectives on two-electron atoms. Our analysis based on Multichannel Quantum Defect Theory (MQDT) demonstrates a good understanding of the interactions between the two electrons in such levels. In particular, we need for the first time to include in the theory a channel with no bound state to account accurately for the level perturbations. Once excited to the Rydberg state, the atom has still a valence electron to optically manipulate its external degrees of freedom. However, autoionization can occur when this 2nd valence electron is optically excited. In the purpose of studying this autoionization process, we have recently performed ionic core spectroscopy. These results will also be presented.