激光冷却YbH分子的理论研究

Theoretical Study on Laser Cooling of YbH Molecule

采用MRCI+Q方法,计算了YbH分子两个最低电子态A^(2)Π和Χ^(2)Σ的势能曲线,得到了相应的光谱常数,与实验结果符合较好。基于振动波函数和计算的A^(2)Π-X^(2)Σ^(+)跃迁偶极矩,理论上得到了YbH分子的Franck-Condon(FC)因子以及相关能级的辐射寿命。结果显示A^(2)Π-X^(2)Σ^(+)跃迁具有较高的对角化FC因子(f_(00)=0.945)和较短的辐射寿命(τ=22.2 ns),表明YbH分子是一个适合激光冷却的分子,给出了三束激光冷却YbH分子的光循环方案,其中主泵浦光波长为619.7 nm,辅泵浦光波长分别为670.4 nm和664.8 nm,计算结果将为实验上冷却YbH分子提供参考。

The potential energy curves for electronic states A^(2)Π and Χ^(2)Σ of YbH molecule are investigated by MRCI+Q method.Based on the potential energy curves,the spectroscopic parameters are determined.The results of calculation agree with experimental and theoretical values satisfactorily.Meanwhile,the transition dipole moments,Franck-Condon factors and radiative lifetime of YbH molecule are investigated.The results indicate that the A^(2)Π-X^(2)Σ^(+)transition has a high diagonalized Franck-Condon factor(f_(00)=0.945)and a shorter radiation lifetime(τ=22.2 ns),indicating that YbH molecule is a suitable molecule for laser cooling.A three-laser-driven scheme for laser cooling of YbH molecules is presented.The calculated wavelengths of pump and repump laser are λ_(00)(619.7 nm),λ_(01)(670.4 nm)and λ_(12)(664.8 nm)respectively.The calculation results will provide useful reference for laser cooling of YbH molecules in experiments.