Experimental Research On Rotational Constant Of The Long-range Ultracold Cs₂

In recent years, ultracold molecules with their huge role in fundamental physics research have caused many scholars to play more and more attention. As the temperature of ultracold molecules is very low, which means that is possible to observe and study these cold molecules in a small energy range.Using spectroscopic technique has very important significance for the study of the internal structure of the molecule in the research of ultracold molecules. As the energy level structure of the molecule is more abundant than atomic, it has a wide range of application in quantum information, measurement of fundamental physical constants and research of multi-body problems. Simultaneously, because the difficulty of obtaining ultracold molecules by directs cooling method due to the complex of internal structure of the molecule, we usually need to adopt an indirect way to get ultracold molecules. This paper describes the preparation of ultracold cesium molecule by photoassociation technique, the obtainment of highly sensitive photoassociation spectroscopy using three-dimensional velocity selective modulation spectroscopy, a series of research in the vibration-rotation structure of long-range states cesium molecules, and precision measurement of the rotational constants. The main work can be summarized in the following three aspects:(1) Preparation of ultracold long-range states cesium molecules by photoassociationFirst, establish and improve the magneto-optical trap system, get a sample of ultracold cesium atoms by laser cooling and trapping techniques, obtain long-range ultracold excited states cesium molecules by Photoassociation methods. At the same time we also achieve the highly sensitive measurement of vibration-rotation spectroscopy of molecular excited states using three-dimensional velocity selective modulation spectroscopy.(2) Measurement of rotational constants of the ultracold cesium molecules 0u+ (6P1/2) stateGet the highly sensitive measurement of vibration-rotation spectroscopy in cesium molecules 0u+(6P1/2) state by three-dimensional velocity selective modulation spectroscopy. By optimizing fitting method of the rotational constants, proposing non-rigid model, experimentally obtain more accurate cesium molecules 0u+(6P1/2) state rotational constants. (3) Precision measurement of rotational constants of the pure long-range 0g (6P3/2) stateUsing two-color photoassociation spectroscopic techniques to build the precise frequency difference reference signal, we achieve the rotational constants precision measurement by overcoming the problems that the pure long-range 0g- (6P3/2) state rotational levels have small intervals, and the measurement accuracy of wavelength meter is very low.