Theoretical Study On Properties Of Atom In The External Fields

In this thesis, in terms of a kind of alkali-metal atomic model potential, the behaviors of the alkali-metal atom lain in the static electric field or microwave field are investigated firstly using B-spline function as basis function. The stationary Schrodinger equation of potassium atom which is put in a static electric field is solved numerically by diagonalization method. The anticrossings of Stark energy levels for Rydberg potassium atom are studied. The calculated positions and widths of the anticrossings are in good agreement with the experimental data. And the anticrossings which are caused mainly by the core interaction or by the spin-orbit coupling interaction are discussed respectively. Meanwhile, based on the above methods and making use of two-level approach, time-dependent Schrodinger equation of potassium atom set in a static electric field together with a microwave field is solved by close-coupling method. The microwave multiphoton transitions between the Stark states of Rydberg potassium atom are investigated. The calculated multiphoton resonance spectrum are in accord with the experimental and other theoretical results. The Rabi oscillations which exist in the processes of multiphoton transitions are also analysed and discussed. In addition, time-dependent Schrodinger equation of three dimensions real hydrogen atom in the external fields is solved through split-operator method. The influences of the static electric field on high-order harmonic generation (HHG) of hydrogen atom in the intense laser field are studied. Comparing with the condition without the static electric field, intensity of odd-order harmonic generation decreases, even-order harmonic generation appears and the HHG spectrum exhibits a double-plateau structure in the case of hydrogen atom in the static electric field. Using wavelet transform, the emissions of HHG in different time are investigated. By means of analysis of the semiclassic theory, the mechanism of HHG for hydrogen atom in the presence of the static electric field and intense laser field are explained and some valuable conclusions are obtained.