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中国物理学会期刊

激光冷却SH阴离子的理论研究

CSTR: 32037.14.aps.68.20182039

Theoretical study of laser-cooled SH anion

CSTR: 32037.14.aps.68.20182039
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  • 本文采用多组态相互作用及Davidson修正方法和全电子基组计算了SH阴离子的\rmX^1\Sigma ^ + , \rma^3\Pi \rmA^1\Pi 态的势能曲线、电偶极矩和跃迁偶极矩. 计算的光谱常数与实验值及已有的理论值符合得很好. 在计算中考虑了自旋-轨道耦合效应. 计算得到\rma^3\Pi _1(\nu ' = 0) \leftrightarrow \rmX^1\Sigma _0^ + ^ + (\nu '' = 0)\rmA^1\Pi _1(\nu ' = 0) \leftrightarrow \rmX^1\Sigma _0^ + ^ + (\nu '' = 0)跃迁具有高对角分布的弗兰克-康登因子, 分别为0.9990和0.9999; 计算得到\rma^3\Pi _1\rmA^1\Pi _1态的自发辐射寿命分别为1.472和0.188 ms. \rmA^1\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + 跃迁存在中间态\rma^3\Pi _0^ + \rma^3\Pi _1, 但中间态对激光冷却SH阴离子的影响可以忽略. 分别利用\rma^3\Pi _1(\nu ' = 0) \leftrightarrow \rmX^1\Sigma _0^ + ^ + (\nu '' = 0)\rmA^1\Pi _1(\nu ' = 0) \leftrightarrow \rmX^1\Sigma _0^ + ^ + (\nu '' = 0)跃迁构建了准闭合的能级系统, 冷却所需的激光波长分别为492.27和478.57 nm. 最后预测了激光冷却SH阴离子能达到的多普勒温度和反冲温度. 这些结果为进一步实验提供了理论参数.

     

    The potential energy curves, dipole moments, and transition dipole moments for the \rmX^1\Sigma ^ + , \rma^3\Pi , and \rmA^1\Pi electronic state of sulfur hydride anion (SH) are calculated by using the multi-reference configuration interaction method plus Davidson corrections (MRCI+Q) with all-electron basis set. The scalar relativistic corrections and core-valence correlations are also considered. In the CASSCF calculations, H(1s) and S(3s3p4s) shells are chosen as active space, and the rest orbitals S(1s2s2p) as closed-shell. In the MRCI+Q calculations, the S(1s2s2p) shells are used for the core-valence correlation. Spectroscopic parameters, Einstein spontaneous emission coefficient, Franck-Condon factors, and spontaneous radiative lifetimes are obtained by using Le Roy’s LEVEL8.0 program. The calculated spectroscopic parameters are in good agreement with available experimental data and theoretical values. Spin-orbit coupling (SOC) effects are evaluated with Breit-Pauli operators at the MRCI+Q level. Transition dipole moments (TDMs) for the \rmA^1\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + , \rma^3\Pi _0^ + \leftrightarrow \rmX^1\Sigma _0^ + ^ + , \rma^3\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + , \rmA^1\Pi _1 \leftrightarrow \rma^3\Pi _0^ + and \rmA^1\Pi _1 \leftrightarrow \rma^3\Pi _1 transitions are also calculated. The strength for the \rmA^1\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + is the strongest in these five transitions, the value of TDM at Re is –1.3636 D. We find that the value of TDM for the \rma^3\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + transition at Re is 0.5269 D. Therefore, this transition must be taken into account to build the scheme of laser-cooled SH anion. Highly diagonally distributed Franck-Condon factor f00 for the \rma^3\Pi _1(\nu ' = 0) \leftrightarrow \rmX^1\Sigma _0^ + ^ + (\nu '' = 0) transition is 0.9990 and the value for the \rmA^1\Pi _1(\nu ' = 0) \leftrightarrow \rmX^1\Sigma _0^ + ^ + (\nu '' = 0) transition is 0.9999. Spontaneous radiative lifetimes of \tau \left( \rma^3\Pi _1 \right)= 1.472 \;\textμ\rms and \tau \left( \rmA^1\Pi _1 \right)=0.188 \;\textμ\rms are obtained, which can ensure that laser cools SH anion rapidly. To drive the \rma^3\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + and \rmA^1\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + transitions, just one laser wavelength is required. The wavelengths are 492.27 nm and 478.57 nm for two transitions, respectively. Notably, the influences of the intervening states \rma^3\Pi _1 and \rma^3\Pi _0^\rm + on the \rmA^1\Pi _1 \leftrightarrow X^1\Sigma _0^ + ^ + transition are small enough to implement a laser cooling project. A spin-forbidden transition and a three-electronic-level transition optical scheme of laser-cooled SH anion are constructed, respectively. In addition, the Doppler temperatures and recoil temperatures for the \rma^3\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + and \rmA^1\Pi _1 \leftrightarrow \rmX^1\Sigma _0^ + ^ + transitions of laser-cooled SH anion are also obtained, respectively.

     

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