The Experimental Research Of Ultracold NaCs Molecular Spectra By Phase Lock Detection Technique

Ultracold polar molecules have drawn considerable interests over the last decade,because of the unique properties.For example,the permanent electric dipole moment,anisotropic dipole-dipole interaction can be easily controlled by field,etc.In particular,molecule-fixed electric dipole moment makes external control over the motion and internal quantum state very convenient.So it has widely applications in precision,quantum simulation,quantum information,and controlled ultracold chemistry.Whenever light is used to prepare ultracold polar momecules in a controlled way or manipulate their internal state,precise knowledge of the molecular structure is required.We prepare ultracold polar molecule of NaCs by photoassociation,and detect the molecular photoassociation spectra with trap loss technology.The trap loss spectroscopy of the trapped ultracold atoms has often served as a high resolution PAS for the rovibrational or hyperfine structures of the excited molecules.However,Due to the low sensitivity and resolution,as well as a variety of noises in the laboratory and system,the SNR of our photoassociation spectrum is relatively low,which leads to limited understanding of the molecular structure.In order to obtain more accurate energy level information of NaCs molecules,the signal-to-noise ratio(SNR)of NaCs molecules is enhanced by using phase-locked amplification detection technique.The work of this paper is based on the collision properties between the ultracold sodium atoms and the ultracold cesium atoms in a dual-species magneto-optical trap.The ultracold polar NaCs molecules were successfully prepared by photoassociation.Finally,the photoassociation spectrum of NaCs molecules were detected and recorded by trap loss spectroscopy.We enhance the signal-to-noise ratio(SNR)of the photoassociation spectrum by phase locking detection.The main contents of this paper are as follows:1.First,we introduce the basic physical properties and hyperfine of the Na and Cs.At the same time,we introduce the optical system,vacuum system and double magneto-optical trap system for the experimental capture of sodium and cesium atoms.2.The energy level structure of ultracold polar molecule is analyzed theoretically,the experimental process of photoassociation to prepare ultracold polar NaCs molecule together with the detection mechanism of ultracold NaCs molecule spectrum is introduced in detail.3.We investigate the dependence of the SNR of the PA spectra on the integration time and sensitivity,which are set on the lock-in amplifier in the detection process.We also find that the scanning time of the PA laser has a great effect on the SNR of the PA spectra,and analyze the dependence characteristic of the SNR on the interaction time of the PA laser with both ultracold Na and Cs atoms.The SNR of NaCs molecular spectrum is increased by nearly 10 times.