Utilizing Stark effect in Rydberg atoms for electric-field sensing in cold ion clouds*

Rydberg atoms are actively utilized for electric-field measurements and sensing in cold-atom environments and in room-temperature vapors. In the current work, we explore the potential of the Rydberg-atom electric-field sensing method to diagnose cold-ion clouds subjected to a controllable dc external ion extraction field. An emphasis of the work is to quantify the significance of microfields relative to that of external and macroscopic fields. Our ion clouds are generated by photoionization of rubidium 5D_3/2 atoms prepared in an optical dipole trap. We obtain and analyze Stark spectra of cold Rydberg atoms seeded into the ion clouds, for cases of both high- and low-orbital-angular-momentum Rydberg states. A numerical model used to explain the observations and its interpretation will be discussed. The data overall show that Rydberg-atom-based electric-field sensing is a practical method to quantify the significance of the microfields. Our results on Rydberg-atom Stark spectroscopy in the presence of ions are of interest for monitoring electric fields in focused ion beam sources and in cold plasmas.