Research On Several Problems Of Coherent Control And Ionization Of Rydberg Alkali Atoms

Following the development of generation and detection of electromagnetic wavetechnology, and the applications of nonionizing radiation in the fields of medical andmaterial-probing, the interaction between Rydeberg atoms and the electromagnetic wavewith the frequency from dozens of gigaherta to1THz has developed quickly. Theinteraction laws of electromagnetic waves and Rydberg atoms are the important physicalbasis of the research of micro and terahertz wave generation and detection, and which arealso the important research contents of realizing the coherent control and ionization ofquantum states.In this thesis, the main research contents are the basic theory of the interactionbetween electromagnetic wave and Rydberg alkai atoms. Base on the calculation ofRydberg atom energy level and wave function with high precision, using time-dependentmultilevel approach and the emluator compiled by myself, the interaction rules betweenRydberg alkali atoms and micro, terahertz wave are studied, the population transition andphoto ionization of Li, Na and Ru atoms is analyzed. The simulation results agree well withthe experiment. In the experimental aspect, the preparation of Rydberg states is completed,the resonance spectroscopy of Na atoms in zero and electrostatic field is measured by fieldionization course. The experimental result is consistent with the simulation result.In this thesis, the main research contents include:1. Uing B-splines combined with model potential, the energy levels and wave functionof Rydberg atoms in zero field is calculated, the energy values changes with the externalfield strength is analyzed in detail, and the the position and width of avoid crossing ofadjacent energy level is presented, which provides theoretical basis for preparing highRydberg states in the experiment.2. Complile the program of coherent control of Rydberg atoms in microwave field.Using the time dependent multilevel approach, the dynamic property of Rydberg atoms inchiped microwave filed is calculated. The population transition probability from n75ton70and from n79to n70quantum state of Li atom with more than90% efficiency is achieved by means of sequential single-photon or two-photon transitions. Allof the available orbital angular momentum l states for the same n are fully utilized, andthe interference pattern of the individual states is considered during the populationevolution. The simulation results show that: the coherent control of the population transfercan be accomplished by optimization of the chirping parameters and microwave fieldstrength. The simulation results agree well with the experiment results, and layingtheoretical foundation for analyzing the characteristics of Rydberg atoms in terahertz field.3. The program of the coherent control and ionization of Rydberg atoms by terahertzpulse is compiled based on the theory analysis of interaction rules beteen teranertz pulseand Rydberg atoms. The population redistribution of three energy level system of RydbergRu atoms is calculated after interacting with a train of terahertz pulses, and the coherentcontrol of many quantum states system by many trains of terahertz laser pulses is analyzedin detail, the population evolution of the individual l states for the same n is presented, theequivalence between oscillations period of the initial and final states and the Kepler periodof the selected states is discovered by controlling the time delay of the adjacent half cyclepulse. The calculation results show that: the coherent control and ionization of thepopulation can be accomplished by optimization of the terahertz pulse parameters.According to the theoretical study results, novel explanations have been given tounderstand the experimental results. The reaearch results are helpful for detecting terahertzpulse by using Rydberg atoms.4. Using time-of-flight mass spectrometer, high Rydberg states is prepared by excitingalkali metal atoms in vacuum using ultraviolet laser. The resonantce absorption spectrum ofNa atoms is obtained in the zero and electrostatic fields. The experimental results of sodiumabsorption spectrum with the principal quantum number from n34to n46agreewell with the theoretical results, the ionization threshold of this principal quanum numberrange correspond to the photon energy of THz domain. The experiment results agree wellwith the simulation results. Based on the present experimental platform, the experimentdevice of detecting terahertz pulse by Rydberg atom is designed.