Population Trapping And Excitation Of The Rydberg Atom In The Frequency-modulated Fields

In this thesis, a time-dependent multilevel approach(TDMA) for solving thetime-dependent Schr?dinger equation for alkali atoms in static electronic fieldand an arbitrary time-dependent external field is presented. In this method,firstly, a kind of potential model wave functions of the alkali atom in zero fieldis chosen as a basis set to expand the wave function of the atom in static electronicfield. Secondly, the time-dependent wave function of the atom in static electronicfield and time dependent external field is expanded by the wave functions of theatom in static electronic field. The state-to-state transition probability canbe obtained by solving a set of one order differential equations of the expansioncoefficients.We have, for the first time, calculated the transition probability between twoRydberg Stark states of potassium atom in a static electronic field plus a microwavefield and a radio-frequency(rf) field. The calculation results show that thepopulations between the two states are Rabi oscillation in the absence of the rffield, square-wave oscillations in the presence of the slow rf field, and stairsteps oscillations in the presence of the intermediate rf field. We have alsocalculated rf multiphoton resonances in the presence of the high rf field , andthe phase shift of the population oscillation when the rf amplitude is suddenlychanged. The numerical results are in excellent agreement with those of theexperiment. Novel explanations have been given to understand the structures bothon the crest and in the trough of the square-wave oscillation. And two newapproaches of realizing population trapping have been predicted. The results arelikely to applying to the manipulation of the quantum state of single atom andto setting a single photon source of quantum cryptography.