Stark spectra of Rydberg states in atomic cesium in the vicinity of n=18

The Stark structures in a cesium atom around n=18 are numerically calculated. The results manifest that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and that with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in an ultracold atomic cesium. Atoms initially in 6P_3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to field, and Stark spectra with |m|=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.