Study On The Collision Dynamics Of BeH(X~2∑~+) Molecule With Ar Atom In Cold And Ultracold Temperatures

In recent decades, cooling and trapping of molecule is a very active research topic in Physics Research. Cold and ultracold molecular has a very important application prospects such as collision of cold molecules, high-precision spectroscopic measurements, quantum computation, and condensed matter physics in physics and chemistry and other disciplines. Sympathetic cooling is one of the most primising techniques for producing ultracold molecules from cold molecules. And many research showed that, it was impossible to use the ultracold rare gas atoms as coolant for sympathetic cooling. We have completed a comprehensive study of the Ar-Be H complex. We perform calculations of the interaction potential energy surface and we have detailedly studied on the dynamics for Be H in collision with Ar. And the major conclusions are summarized as follows:(1) We have generated the interaction potential energy for the Ar–Be H in the 299 configurations of the value based on supermolecular ab initio calculations incorporating CCSD(T) method, the aug-cc-p VQZ basis set and quadruple zeta basis set. And then we use the model of potential function and least square fitting method to get the Ar-Be H potential energy surface. The PES is weakly anisotropic and has a shallow minimum withenergy of-114.62cm- 1 locates at R=6.98a0 and θ=81.0°.(2) Based on the ab initio PES and the Fitting method, we have used quantum mechanical scattering calculations to investigate the elastic and inelastic cross sections from low-field-seeking states with N=0、 m j =1/2 of Be H(2X+S) in external magnetic fields at low and ultralow energies. We found that the Zeeman relaxation cross section dependent on the magnetic field is stronger than the elastic cross section; because of the centrifugal barrier in the exit channels, the inelastic cross sections are suppressed both at low energy and low field; And the same time, we know that the ratio of elastic-to-inelastic cross sections are high enough(>>100), over a wide enough range of collision energy, magnetic field and scaling factor F of PES. It suggests sympathetic colling of Be H with Ar atoms is a good prospect.