Optical and microwave study of very weak perturbation in high Rydberg states of lutecium

A very weak perturbation around the 6s 2 52d 2 D 3/2 high Rydberg series of Lu has been studied. An intensity distribution of the optical spectrum around the perturber exhibits well developed Fano profile with significant decrease of radiative life time by the perturbation. Microwave two-photon transitions among the 6s 2 nd 2 D 3/2 series are measured to determine the accurate energy level structure of the perturbed series. Analysis of the microwave spectrum as well as the intensity profile and its delay-time dependence has led to the determination of accurate spectroscopic parameters.