The Optimation Of Dark MOT To Product Ultracold RbCs Molecules And Spectroscopic Measurement Of(2)0~+ State

The features of ultracold polar molecules that are different from cold atoms and nonpolar molecule are the permanent electric dipole moment,anisotropic dipole-dipole interaction can be easily controlled by field,etc.,so it has been widely used in aspects of ultracold chemistry,quantum computing and test the basic symmetry.Many experimental groups obtain ultracold molecules via photoassociation,mainly because of the low technical requirements for initial atomic temperature,large number and density of molecules,and the simple experiment.Photoassociation technology is helpful to study nuclear interactions between the long-range excited states molecules and understand the transition from a bound state to a free state,and it plays an important role for the preparation of the ground state molecules.In this paper,based on the dark magneto optical trap,we prepare the ultracold polar RbCs molecules by PA,and detect excited state ultracold RbCs molecules by different ways.The number of ultracold RbCs polar molecules is increased significantly after the optimization of optical system.We also studied?2?0⁺ state photoassociation spectrum.The main works of this paper are as follow:?a?Preparation and detection of atoms and moleculesFirst,we introduce the basic physical properties and hyperfine structures of the Rb and Cs atoms.Second,we introduce the theoretical knowledge of trapping atoms and producing molecules,and give the experimental schematic diagram and the related parameters of obtaining atoms and molecules.At last,we provide two detection methods,and choose ion spectrum to detect ultracold RbCs molecules in ground state and excited states.?b?Space-adjustable dark magneto-optical trapWe use double mixed beams of repumping beams and depumping beams in near-counter propagation to control the space position of two atoms.By changing repumpping power ratio of the two mixed beams,the overlap of two atomic clouds can be easily adjusted from zero to complete overlap.We also measure the collision loss ratio of atoms.Comparing with the number of RbCs molecules with single-mixed beam,we find the number with the double-mixed beams is improved by 70%.?c?Spectroscopic measurement of ultracold?2?0⁺ state RbCs moleculesWe use ion spectroscopy to observe ultracold excited state RbCs molecules,and research a series of high resolution photoassociation spectrum and related features of molecules in?2?0⁺ state,such as related vibrational quantum number,rotational constants and C₆ coefficient.