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中国物理学会期刊

AlH+离子5个-S态和10个态的光谱性质以及激光冷却的理论研究

CSTR: 32037.14.aps.67.20180926

Theoretical study of spectroscopic properties of 5 -S and 10 states and laser cooling for AlH+ cation

CSTR: 32037.14.aps.67.20180926
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  • 利用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法结合相关一致基组aug-cc-pV6Z计算了AlH+离子前两个离解极限对应的5个-S态和10个态的势能曲线.为了提高势能曲线的可靠性和精确性,计算中考虑了自旋轨道耦合效应、芯电子价电子相关和标量相对论修正以及将势能外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的4个-S态和8个态的光谱常数和振动能级,与已有的实验结果符合.计算了2(1/2)X21/2+和A23/2X21/2+跃迁的跃迁偶极距.利用计算的精确的势能曲线和跃迁偶极矩,获得了2(1/2)第一势阱(v'=0,1)X21/2+(v)和A23/2(v'=0,1)X21/2+(v)跃迁的高度对角化分布的Franck-Condon因子(f00和f11)和大的振动分支比;预测了2(1/2)第一势阱(v'=0,1)和A23/2(v'=0,1)态短的自发辐射寿命和窄的辐射宽度,这适合于AlH+离子的快速激光致冷.所需的3束激光冷却波长都在紫外区域.这些结果表明了激光冷却AlH+离子的可行性.此外,评估了自旋轨道耦合效应对光谱常数、振动能级和激光冷却AlH+离子的影响.

     

    In this paper, we calculate the potential energy curves of 5 -S and 10 , which arise from the first two dissociation limits of the AlH+ cation. The calculations are done using the complete active space self-consistent field method, which combines with the valence internally contracted multireference configuration interaction plus the Davidson modification (icMRCI+Q) approach with the aug-cc-pV6Z basis set. To improve the reliability and accuracy of the potential energy curves, the core-valence correlation and scalar relativistic correction, as well as the extrapolation of potential energy to the complete basis set limit are taken into account. The spin-orbit coupling is computed using the state interaction approach with the Breit-Pauli Hamiltonian. Employing the potential energy curves obtained in this study, we evaluate the spectroscopic parameters and vibrational levels for the bound and quasi-bound 4 -S and 8 states. The computed spectroscopic constants of X2+ and A2 states are all in agreement with the available experimental data. Moreover, the present theoretical energy separations between each higher channel (Al+(3P0) + H(2S1/2), Al+(3P1) + H(2S1/2), and Al+(3P2) + H(2S1/2) and the lowest one (Al+(1S0) + H(2S1/2)) are in excellent agreement with the experimental values. The transition dipole moments are calculated using the valence internally contracted multireference configuration interaction approach with the aug-cc-pV6Z basis set for the 2(1/2) X21/2+ and A23/2X21/2+. Based on the obtained potential energy curves and transition dipole moments, highly diagonally distributed Franck-Condon factors (f00 and f11) and large vibrational branching ratios are determined for the 2(1/2)1st well (v'=0, 1) X21/2+ (v) and A23/2(v'=0,1)X21/2+(v) transitions; short spontaneous radiative lifetime and narrow radiative width for the 2(1/2)1st well (v'=0, 1) and A23/2 (v'=0, 1) are also predicted in this study, which are suitable for the rapid laser cooling of the AlH+ cation. The three required laser cooling wavelengths are all in the ultraviolet region, that is, 1) for the X21/2+(v) 2(1/2)1st well (v') transition:the main repumping laser 00=358.74 nm, two repumping lasers 10=379.27 nm and 21=374.86 nm; 2) for the X21/2+ (v) A23/2 (v') transition:the main repumping laser 00=357.43 nm, two repumping lasers 10=377.80 nm and 21=373.26 nm. In addition, the recoil temperature for the X21/2+ (v=0) 2(1/2)1st well (v'=0) and X21/2+ (v=0) A23/2 (v'=0) transitions are obtained. The results imply the feasibility of laser cooling of AlH+ cation. In addition, the spin-orbit coupling effect on the spectroscopic parameter, vibrational level, and laser cooling of AlH+ cation are evaluated.

     

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