Interaction And Collisional Properties Of Ultracold Rydberg Atoms

Rydberg atoms, one electron of atoms is excited in states with high principal quantum number. In contrast to ground-state atoms, Rydberg atoms have many exaggerated properties including the large radius, large dipole moment, long radiative lifetime and so on. Due to their exaggerated properties, the research of Rydberg atoms is one of the important sections in atomic, molecular physics. In recent years, laser cooling and trapping techniques provide the new techniques and methods for studing of Rydberg atoms, and we can further investigate the physical natures of Rydberg atoms. The ultracold Rydberg atoms do not move significanlly during experimental time scales; the interactions between ultracold Rydberg atoms are much larger than their kinetic energy. In particular, and the interaction strength between Rydberg atoms can be tuned and controlled by the external field, The dynamics process of ultracold Rydberg atoms are determined by the interaction between Rydberg atoms and the external field, which make the ultracold Rydberg atoms candidates in quantum information storage, quantum computing and quantum information processing. In this thesis, The Stark structures and the potential of interactions of Cs Rydberg atoms are calculated theoretically. We obtained the ultracold Rydberg atoms by two-steps exciting cold atomic sample. The spectrum and parameters of ultracold Rydberg atoms are obtained, and the collisions between Rydberg atoms and state transfer due to interaction are investigated in detail. Firstly, we measure the Stark spectra and Polarizability of Cs nD states (39<n<50) by using the frequency doubling cw laser, which is in good agreement with the results of the theoretical calculation. Secondly, we measured the Rydberg atomic lifetimes for nS and nD states (30<n<40) and collisioanl cross section of Rydberg nD states (37<n<40) using the dye laser, the experimental results are explained by theoretical model. Thirdly, we measure collisional loss rate coefficients between Rydberg atoms and state transfer induced by interactions.The main innovative points of this paper are as following:1. The variation of effective lifetimes of Rydberg states with Rydberg atomic density was studied experimentally. The Rydberg atomic lifetimes for nS and nD states (30<n<40) were measured in low Rydberg atomic density, which is in agreement with the existing theoretical model.2. We have measured the effective decay rates of Rydberg atoms density, and obtained the collisioanl cross section of Rydberg nD states (37<n<40). The experimental results are explained by theoretical model.3. The collisional effect of Rydberg states were studied in detail, the collisional loss rate coefficients due to collisions with Rydberg atoms and ground-state atoms are obtained by fitting experimental data, and the collisional loss rate between Rydberg atoms is significantly increased by a weak electric field tuning interaction between ultracold Rydberg atoms.4. The quantum state transfer induced by interactions between ultracold Rydberg atoms were studied, including the dynamics evolution of quantum state transfer process under electric field, delay time and laser intensity, respectively.