Theoretical Study Of Vibronic And Rotational Spectrum Of Diatomic Molecule Suitable For Laser Cooling

Experimental preparation and research of cold molecules is one of the frontier in the field of atomic, molecular and optical physics in recent years, and it is endowed with a strong interdisciplinary character and connections to physics, chemistry, quantum information, condensed matter physics and astrophysics. Beside of the translation, molecule has the rotation and vibration of freedom, the energy level structure of molecule is much more complicated than the atom, thus people needs to face much more difficulties to realize the laser cooling and MOT of molecules. In experiment we should choose the quasi-closed energy level system for laser cooling.In theory, firstly, this paper discuss about how to choose the molecule candidate for the laser cooling, then analyze vibronic structure and rotational hyperfine structure of some molecular X and A states, explore the possibility for laser cooling experiments. The Franck Condon Factors and hyperfine energy level structure of diatomic molecules are the main focus. Secondly, we analyze and calculate the Franck-Condon Factors by the method of the Morse potential approximation and the RKR inversion calculation, and then compare these two methods. Lastly, we analyze the hyperfine energy level splitting of the common alkaline earth fluorides; meanwhile calculate the hyperfine energy level structure of diatomic molecules.In experiment, we summarize many different kinds of preparation methods for radical molecules of alkaline earth metal fluoride and also emphasize the frequency-stabilized laser system and cryogenic vacuum system for laser cooling, these works pay the way for the laser cooling experiment of molecules.