Research Of Effect From The External Magnetic Field On The Shift Of Resonant Frequency In Photoassociation Of Ultracold Cs Atoms

At the end of last century,with the realization of the alkali neutral atoms of Bose Einstein condensation(BEC)and Fermi gas quantum degenerate(DFG),ultracold atomic physics have become the focus in the frontier of physics.Ultracold atomic samples play an important role in various physics problems(including precision measurement,quantum information processing and simulation,etc.).It is expected that the same will be achieved in ultracold molecular systems,because of the difference between ultracold molecules and traditional molecules in essence,the complex structure of energy levels,the easy regulation of dipole-dipole interaction and the rich degree of freedom,the ultracold molecules present a promising prospect.With the recent development of photoassociation theory,ultracold alkali metal molecules have been obtained experimentally one after another,which has well verified the photoassociation theory.Most importantly,in 2008,professor Jun Ye's team from the United States Joint Institute for Laboratory Astrophysics achieved the ro-vibrational ground state of 40K87Rb molecules through stimulated Raman adiabatic transfer,providing a new scheme for the study of the ground state molecules.Although the motivations of scientists to produce,capture and manipulate ultracold molecules are varied and interdisciplinary,their approach to making molecules is essentially the same,the method of photoassociation(PA)and Feshbach resonance is generally adopted.In this paper,the method of preparing ultracold cesium molecules is photoassociation(PA).Under this background,the linear rule of PA laser intensity and spectral resonance position frequency shift is studied.At the same time,combining with the single channel square potential well model,the effect of photoassociation resonance frequency shift of ultracold cesium atoms in the external field is studied quantitatively.The main work contents are as follows:Firstly,The 133Cs atom was captured in a magneto-optical trap(MOT)Cesium atoms were then prepared to the superfine level 62S1/2,F=3 state by increasing the gradient magnetic field,decreasing the power of the repump laser,increasinghe detuning of the trapping laser,and optical molasses.Through degenerated three dimensional Raman sideband cooling by the Raman laser,the cesium atom remains at a much lower temperature at 6 2S1/2|F=3,mF=3;v=0).Sencondly,a magnetically levitated optical crossed dipole trap is made up of two red detuning high-power laser beams,gradient magnetic field and bias magnetic field.Cesium atoms are loaded in the center of crossed dipole trap to obtain high-quality ultracold 133Cs atoms.Where the laser power is 7 W,the bias magnetic field is 75 G,and the gradient magnetic field is 31.13 G/cm.At this point,the cesium cloud becomes denser?2.5×105,and the temperature gets even lower?3.5 ?K.Then,the 852 nm laser output by a Ti:sapphire laser device is selected and injected into the center of the optical well.By using the method of photoassociation(PA),the cesium atoms is formed into a cesium molecule in the levelvD-v=190 of Ou+ state under the dissociation limit of 6S1/2+6P1/2.Thirdly,spectrum resonance frequency shift and intensity of the laser keep a linear relationship by changing the photoassociation laser intensity.Under different external magnetic field,repeating the experiment process,the frequency shift rate depends on the external magnetic field,it is quantitatively theoretical analyzed by introducing the external magnetic field control the depth of adjustable single channel square potential well model.The experimental results are in good agreement with the quantitative analysis.In the internal area of the model,the external magnetic field affect the atomic behavior,further affect atomic photoassociation.