Hyperfine Strcuture Of Ultracold NaCs Heteronuclear Molecules

Spectroscopic studies of diatomic molecules,specifically bi-alkali atoms,have provided a great deal of information about many interesting and fundamental ideas surrounding molecular quantum mechanics.Information gathered from the study of these molecules can be useful for many different areas of research.Currently a great deal of work is being done with diatomic alkali molecules in attempts to devise efficient processes of producing ultracold ground state molecules.Photoassociation are brought to produce the heteronuclear molecule in the rovibrational state.The field of ultracold molecules is the result of successes in atomic laser cooling and trapping.An atomic sample at ultracold temperatures is the reservoir from which ultracold molecules are formed via either photoassociation(PA)or magnetoassociation(MA).PA,however,is a process where a colliding pair of ground state atoms absorbs a photon to form an excited state molecule which then decays to the ground state.An advantage of PA includes the creation of some very deeply bound molecules with a large permanent electric dipole moment,however,the majority of the population is dispersed over a range of energies.MA is a process where a magnetic field is used to shift a ground state molecular energy into resonance with a colliding pair of atoms.This approach creates molecules in a narrow range of energies,and the experiment requires fine control of the magnetic fields which can be as large as 1000G.In this paper,we mainly introduce the preparation of NaCs heteronuclear molecules with different dissociation limits by photoassociation.We observed hyperfine structures of different electronic states and analyzed these structures in detail.It provides a good basis for the subsequent preparation of NaCs heteronuclear molecules in the ground state of ro-vibration levels using magnetic association and stimulated Raman adiabatic psssage(STIRAP).The main work of this thesis summarized as follows:1.We realized the preparation of sodium and cesium in a dark magneto optical trap.Based on this,we achieved the preparation of ultracold NaCs heteronuclear molecules.We observed the effects of different laser intensities on the preparation of heteronuclear molecules.Based on the saturation's theory and combination of our experimental data;we obtained the relationship between the laser intensity and preparation of heteronuclear molecules.The results of fitting allowed us to find a suitable laser intensity.2.For the A1?+ state at the dissociation limit 3S1/2+6P1/2,12 resonance lines are detected using trap-loss spectroscopy based on highly sensitive modulation technique.The highest observed rovibrational level exhibits clear hyperfine structure,which is detected for the first time.This hyperfine structure is simulated within a simplified model containing four coupled levels belonging to different initially unperturbed Hund's case "a" electronic states.The simulation illustrates that the level possesses mixed electronic nature with dominant character from A1?+ and b3II states.3.We observed the hyperfine structure in three ro-vibrational levels of the b3?2 state of NaCs near the dissociation limit 3S1/2+6P3/2.The hyperfine structure is mostly caused by the interactions of the nuclear spins with the electronic spins and with the electronic orbits.The simulation of the hyperfine structure showed that the greater part of the observed structure belongs to almost isolated levels of the b3? state,but there are other parts of mixed character where the contribution from the 1?symmetry dominates.