Optical Trapping And Microwave Manipulation Of ⁸⁵RbCs Molecules In Lowest Vibrational Ground State

The preparation and manipulation of ultracold molecules have attracted intensive attentions in the past few years.Based on the strong dipole-dipole interactions,ultracold polar ground-state molecules are especially attractive.These samples possess permanent electric dipole moments ranging from a half to several Debye,which could interact strongly with external fields and each other with long-range dipole-dipole force.These novel characteristics might facilitate some interesting applications in precision measurement,realization of quantum control of cold chemical reactions,inspiring quantum computation and quantum simulation et al..Based on the ultracold mixed atomic sample,the molecules could be prepared by photoassociation?PA?or magneticassociation?MA?,which are the main methods for the creation of ultracold ground polar molecule.In particular,the PA technology is easy in operation and could produce ground state molecules continuously.Thus,based on the PA,the ultracold ground state ⁸⁵RbCs molecules have been prepared directly,a series of systematic study for the molecules have been finished,such as the detection,capture and manipulation.The lowest vibrational ground state ⁸⁵RbCs molecules were prepared by direct short-range PA initially.The detection of the ground state molecules have been realized by sensitive photoionization and high resolution depletion spectroscopy.The optical trapping of ultracold ⁸⁵RbCs molecules in the lowest vibrational ground state molecules with long life and high density also have obtained.Finally,by coupling molecular rotational levels via microwave field,the manipulation of ⁸⁵RbCs molecules in the lowest vibrational ground state has been achieved.The main work of this thesis is listed as follows:Firstly,the high sensitive detection of ⁸⁵RbCs moledules in the lowest vibrational ground state is realized by one-and two-color resonance-enhanced two-photon ionization detection.With these two procedureds,the related energy levels have been determined.Meanwhile,the comparation of these two procedures,the one-color procedure is simple and convenient.By using the model of multiphoton ionization procegress,the ionization rate constant also has been achieved.Secondly,based on the work in the first part,the continuous-wave depletion spectroscopy technology is also introduced.The rotational energy can be detected and the resolution in detection is improved from GHz to MHz.Then,the structure of ⁸⁵RbCs molecules in the lowest vibrational ground state has been maeasured.Further more,the two-photon-cascade decay in the molecular preparation process is confirmed.Through the calibration of the ion number,the production rate of molecules in the lowest ground state also has been determined.Thirdly,the high power fiber laser?1070nm?is introduced to build the far-off resonance trap.The lowest vibrational ground-state ⁸⁵RbCs molecules have been trapped and the dynamics of molecules in loading and holding process of trapping are resaerched.By observing the inelastic collision process between the ultracold ⁸⁵Rb?Cs?atom and the lowest vibrational ground state ⁸⁵RbCs molecules,the inelastic collision rate can be decueced by a phenomenological rate equation.By reducing the influence of the inelastic collisions between the atoms and molecules,the lifetime of the lowest vibrational ground state ⁸⁵RbCs molecules is increased to 100 ms from ms.The redistribution of the ground state also has been tested.Fourthly,based on the continuous-wave depletion spectroscopy with microwave transfer technology,the rovibrational ground ⁸⁵RbCs molecules between different rotational levels have been manipulated.The high resolution molecular microwave spectra have been measured.Compared the results between the MW and depletion spectroscopy,the precision of the rotational constant obtained by MW spectroscopy of the rovibrational ground state is increased from MHz to 10 kHz.The coherent Rabi oscillations of adjacent rotational energy levels are observed,which is also the evidence that the coherent manipulation of the ⁸⁵RbCs molecules in the lowest vibrational ground state.