Electrical Effect Research Of Ultracold Cesium Rydberg Atoms

Rydberg atoms which refer to the atoms in highly excited states posses some unusual properties compared to the normal atoms, such as small energy interval, large dipole moment, and strong interactions, etc. The techniques of laser cooling and trapping and high resolution spectroscopy gave people opportunities to unravel the veil of this field. When the Rydberg atoms were cooled down to the scalar of severalμK, they moved far less than the distance between atoms when observed in 1μs. The ulracold Rydberg atoms were also called the frozen Rydberg atoms as their kinetic energies are far less than the interaction energies. The dynamic evolution of the Rydberg atoms depends on the interactions between them and the external field. The excitation blockade caused by the interactions between ultrocold Rydberg atoms could be used to construct the quantum logic gate which leads to realize quantum storage. So the Rydberg atoms soon became the research frontier of the field of atom and molecular physics.The Rydberg atoms are very sensitive to the external field due to their small bonding energies and small energy intervals, and the polarizability of the Rydberg atoms are proportional with the 7th order of quantum number n. Then we can manipulate the interactions between the Rydberg atoms via tuning the energy levels of the atoms which can be realized by adjusting the external electric field. The Stark effect refers to the splitting of the atoms spectrum lines when the atoms are in the electric field which change the energy structure of the atoms. In this thesis the ultracold atoms were first acquired, then the ultracold Rydberg atoms were acquired by means of double-photon excitation. When investigating the Stark effect of the ultracold Rydberg atoms, the Stark spectroscopes were plotted with the method of pulsed field ionization, and the polarizabilities of atoms in nD states were calculated. The experimental results agreed well with the theoretical predictions. The paper consists of four parts:First of all, a brief introduction of properties of Rydberg atoms is given. And the theoretical descriptions of the interactions of Rydberg atoms especially the Van der Waals interaction and dipole-dipole interaction were made afterwards. The concept and development of Stark Effect are presented. The application prospect and research development of Rydberg atoms are given at last.The second part mainly deals with the experimental equipment, including the introduction of the process of laser cooling and trapping, the Magneto-Optical Trapping system (MOT) which is used to produce the ultracold Rydberg atoms, the detection of Rydberg atoms, and the laser source we employed. The whole equipment setup of the experiment is given at last.The third part includes the theoretical interpretation. It starts with that the Stark structure of Hydrogen atom is calculated both analytically and numerically, and then the Stark structure of Cesium atom is plotted according to the results of numerically calculation.The last part presents the processes and the results of the experiment. The atoms were excited by the dye laser and semiconductor laser, respectively. Then the Stark structure of the Cesium atom was plotted due to the excitation by the dye laser. The detailed investigation of nD (n=39～50) states was conducted as the atoms were excited to the Rydberg states by semiconductor laser. The scalar polarizabilityα0 and tensor polarizability a2 of nD states were calculated according to the experiment data which agree with the theoretical results very well.