State Transfer And Interference Of NS Ultracold Rydberg Atoms In External Electric Fields

The Rydberg atom is the atom that one of outer electrons is excited to a high principal quantum number n. Compared with normal atoms, Rydberg atoms possess many advantages in study of the field of atomic spectrum. For example, Rydberg atoms are very sensitive to external field because of large polarizability (～n7), Rydberg atoms, therefore, are used to research the atomic energy level and interactions of energy levels by adding external field. Rydberg atoms also have long-range interactions, including dipole-dipole interactions and van der Waals interactions, which offers many facilities in search of the dipole blockade effect. Moreover, some characters, such as long lifetime and large electric dipole moment, make Rydberg atoms enduring in search of atomic and molecular physics.Three aspects are included in this paper:The first is that the Stark effect of ultra-cold Cs Rydberg atoms is investigated and the avoided crossing between nS state and (n-4) manifolds is observed. The second is that the state transition from cesium nS states to Stark states induced by a weak electric-field pulse is investigated. The external electric-field pulse shifts the nS Rydberg states that anticross with the (n-4) hydrogen-like manifolds, causing the state transitions from the initial excited nS state to the Stark states. The third includes that the interference between the initial nS state and the high-l states is investigated by two time-delayed short electric-field pulses. The trapped atoms are excited to the nS Rydberg state by using the two step excitation scheme in a magneto-optical trap. The ion spectrum near the avoided crossing is obtained by using state-selective field pulse ionization technique. By changing the intensity of the applied electric field, we find that the relative intensities of two Stark states near the avoided crossing exchange obviously. State transfer from nS Rydberg state to high-l states due to the avoided crossing is also obtained and the mechanism of this transfer is investigated. Furthermore, the interference behavior of high-l Rydberg states is investigated in external fields. The innovations of this work are shown four aspects as followed:1 Applying a weak electric-field pulse, the state transition from cesium wS states to Stark states is investigated using the state-selective field ionization method. Exciting atoms to selected Stark states (l> 4) directly by dc fields, we find that the present product states and the high-l states occupy the same position in the TOF spectrum, which means that the product states are high-l state. In addition, the mechanism of forming the product states is also investigated.2 We prepare high-l states from an initial excited nS Rydberg state by applying one electric-field pulse. The interference between the initial nS state and the high-l states is investigated by two time-delayed short electric-field pulses. The visibility of interference is defined to describe interference and the results show that a relative long duration of electric-field pulse will weaken the interference.