Studies On Spectroscopy Of Barium Atom In Strong External Fields

The effect of strong external fields on the Rydberg atom is one of the most important issues in atomic physics. As an important subject it involves many fundamental conceptions and theoretical problems in atomic physics and quantum mechanics. In this thesis, we investigate on barium atom which has two valence electrons and a large core. Besides, ionization dynamics of hydrogen atom near a metal surface is studied theoretically. The main research contents and results are as follows:(1) The effect of electric field on the Rydberg atom:spectral properties and dynamics effect. We obtained π and σ polarized Stark spectra experimentally and theoretically. The coupling between states with different parities and core effect were analyzed by the aid of Stark map, and a level anti-crossing was observed. The resonance structures above classical ionization threshold was obtained. The Stark deceleration of Rydberg atom was realized experimentally and analyzed qualitatively with Stark map.(2) The effect of magnetic field on the Rydberg atom:spectral properties and decomposition of the polarized spectrum. We obtained σ+polarized diamagnetic spectra experimentally and theoretically, and analyzed the coupling between states with the same parity. By sweeping the quantum defect values of different states, we studied the effect of non-hydrogen states on the diamagnetic spectra and an anti-crossing was identified. We obtained π and "arbitrary" polarized diamagnetic spectra experimentally. By decomposing the complex spectrum into three basic polarized spectra, we reproduced the diamagnetic spectra satisfyingly.(3) The effect of combined fields on the Rydberg atom:the spectroscopy in the parallel and crossed fields. We obtained experimentally the evolution map of diamagnetic spectra on electric field and Stark spectra on magnetic field, and reproduced them theoretically. We observed splitting of diamagnetic spectra with electric field increasing and splitting of Stark structures with magnetic field increasing. Three types of states for barium atom in parallel fields were found. An anti-crossing between the states of types Ⅰ and Ⅱ was observed, which is induced by atomic core. The spectra of barium atom in corssed fields were obtained experimentally and a preliminary calculation was undertaken by the direct diagonalization of the Hamitonian matrix in three-dimensional spaces.(4) Hydrogen atom near a metal surface. We studied the ionization dynamics of hydrogen atom near a metal surface in spatial domain with semi-classical calculation. We obtained the interference patterns at different scaled energies. The results show that different types of trajectories contribute predominantly to different manifolds in a certain interference pattern. With the increase of scaled energy, the interference patterns evolve smoothly and new types of orbits come to appear, which is similar to the case of hydrogen atom in parallel fields. Metal surface can play the same role of magnetic field and induces chaos at small atom-surface distance.