Research On The Electronic State Structure Of YbH And YbF Molecule

The realization of cooling and trapping for atoms and molecules by laser is a hot research topic in the field of physics today.Cold atoms and molecules have important application in a series of fields,such as atomic clock,quantum information and quantum computing,and precise spectroscopy.In this paper,based on the molecular experiment of laser cooling,we studied the electronic state properties of YbH and YbF molecules,and explored the feasibility of these molecules as candidates of laser cooling.The main results are as follows:?1?With the multi-reference configuration interaction?MRCI?method,the potential energy curves of the ground electronic states?²?⁺and the two lower excited states?²?and B²?⁺for YbH and YbF molecules,and the transition dipole moments between the electronic states?²?⁺,?²?,and B²?⁺are calculated.Using the discrete position representation method,the Schr?dinger equations of the corresponding electronic states are solved,and the vibrational energy levels and vibrational wave functions of these electronic states are obtained.The spectroscopic constants fitted by the vibrational energy levels are in good agreement with the experimental results.?2?Based on the vibrational wave functions and TDMS,the Franck-Condon factors,Einstein spontaneous emission coefficients and the radiation lifetimes for the excited states of these two molecular systems are calculated.The results show that the Franck-Condon factors of the above-mentioned vibrational levels between the electronic states of YbH and YbF molecules are diagonally dominant,and the radiation lifetimes of the excited states are very short,all of which are in the ns order.They are suitable candidates for laser cooling.?3?Based on the calculated vibrational levels,Franck-Condon factors and Einstein spontaneous emission coefficients,the laser cooling schemes for YbH and YbF molecules are given.For YbH molecule,the quasi-closed optical cycle consisting of?²??v?=0?-?²?⁺?v=0?transitions is driven by three laser beams.The wavelength of the main pump light is 619.7 nm,and the other two auxiliary pumps are 670.4 nm and 664.8 nm.For YbF molecule,there are two possible schemes,which driven by?²?⁺-?²?⁺and?²?-?²?⁺cycle respectively.The number of laser driving the?²?⁺-?²?⁺transition of YbF molecule are two beams(?₀₀=485.7nm,?₁₀=498.4nm).The number of laser driving the?²?-?²?⁺transition of YbF molecule are three beams(?₀₀=547.6nm,?₁₀=563.8nm,?₂₁=562.8nm).All wavelengths for pump laser light are in the visible range.