arXiv 1404.65792014-04-25physics.atom-ph

Yb离子- Rb原子混合陷阱中的超冷辐射电荷转移

Ultracold, radiative charge transfer in hybrid Yb ion - Rb atom traps

B. M. McLaughlin, H. D. L. Lamb, I. C. Lane, J. F. McCann

备注：: 7 figures, 1 table accepted for publication in J. Phys. B: At. Mol. Opt. Phys. arXiv admin note: text overlap with arXiv:1107.1141
DOI：: 10.1088/0953-4075/47/14/145201

摘要：

超冷混合离子-原子阱提供了使用离子作为探针在气体中微观操纵量子相干性的可能性。然而，非弹性过程，特别是电荷转移可以是一个重要的过程中的离子损失，并已被实验测量的Yb $^{+}$离子浸没在Rb蒸汽。我们使用第一性原理量子化学代码，以获得势能曲线和偶极矩为最低的躺在这个复杂的能量状态。计算了总衰变过程的辐射衰变过程截面和速率系数。半经典朗之万近似与量子方法相比，我们发现它提供了一个很好的估计在较高的能量背景。结果表明，辐射衰减机制是重要的能量和温度范围内考虑。事实上，离子-原子碰撞的朗之万过程在冷离子-原子碰撞中占主导地位。对于自旋相关过程\cite{kohl13}，各向异性磁偶极-偶极相互作用和二阶自旋-轨道耦合可以起重要作用，诱导自旋和轨道运动之间的耦合。他们测量到自旋弛豫碰撞速率比电荷交换碰撞速率\cite{kohl13}高出大约5个数量级。关于测量的辐射电荷转移碰撞率，我们发现，我们的计算是非常好的协议与实验和以前的计算。尽管如此，我们没有发现广泛的共振功能，可能是一个强大的同位素效应。最后，我们发现，与以前的理论一致，在实验中观察到的同位素异常仍然是一个悬而未决的问题。

英文摘要：

Ultracold hybrid ion-atom traps offer the possibility of microscopic manipulation of quantum coherences in the gas using the ion as a probe. However, inelastic processes, particularly charge transfer can be a significant process of ion loss and has been measured experimentally for the Yb$^{+}$ ion immersed in a Rb vapour. We use first-principles quantum chemistry codes to obtain the potential energy curves and dipole moments for the lowest-lying energy states of this complex. Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes. Comparing the semi-classical Langevin approximation with the quantum approach, we find it provides a very good estimate of the background at higher energies. The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered. In fact, the Langevin process of ion-atom collisions dominates cold ion-atom collisions. For spin dependent processes \cite{kohl13} the anisotropic magnetic dipole-dipole interaction and the second-order spin-orbit coupling can play important roles, inducing couplingbetween the spin and the orbital motion. They measured the spin-relaxing collision rate to be approximately 5 orders of magnitude higher than the charge-exchange collision rate \cite{kohl13}. Regarding the measured radiative charge transfer collision rate, we find that our calculation is in very good agreement with experiment and with previous calculations. Nonetheless, we find no broad resonances features that might underly a strong isotope effect. In conclusion, we find, in agreement with previous theory that the isotope anomaly observed in experiment remains an open question.

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