Photoassociation of cold Ca atoms
Photoassociation of cold Ca atoms
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DOI：
10.1109/iqec.2000.907787
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发表时间：
2000-09
期刊：
影响因子：
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通讯作者：
G. Zinner;T. Binnewies;Fritz Riehle;Eberhard Tiemann
中科院分区：
文献类型：
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作者：
G. Zinner;T. Binnewies;Fritz Riehle;Eberhard Tiemann
利用激光冷却原子的光缔合光谱被证明是确定原子的激发态寿命和基态散射长度等性质的有力工具。碱土中最丰富的同位素呈现非简并的基态，没有超精细分裂，这有望在很大程度上简化它们的光缔合光谱。光缔合实验观测的困难弥补了理论描述中的这一优势。到目前为止，激光冷却碱土的系综比大多数光缔合实验中使用的碱土的系综要冷和密度小。Ca的光缔合是通过激发原子对到与原子对4s/sup 2//sup 1/S/sub0/+4s4p/sup 1/P/sub1/相对应的B/sup 1//spl sigma//subn//sup+/激发态实现的。二聚体受共振偶极相互作用的束缚。由于这种R/sup-3/-势的加速，在较小的核距离处衰变的原子通常有足够的动能离开磁光陷阱。通过测量红移到/sup 1/S/sub0/-/sup 1/P/sub1/跃迁的光缔合激光的频率依赖的陷阱损耗，我们解析了分子的振动和转动结构。根据观测到的振动能级位置，修正了部分未分辨的转动结构和基态原子的热能分布，得到了4s4p/sup 1/p/sub1/能级4s4p/sup 1/p/sub1/的原子辐射衰减率/splγ/=2.180(11)/spl midpoint/10/sup 8/S/sup-1/，与以前的测量结果相比，不确定度降低了近一个数量级。
Photoassociative spectroscopy using laser cooled atoms proved to be a powerful tool for the determination of atomic properties such as excited state lifetimes and ground state scattering lengths. The most abundant isotopes of alkaline earths show a non-degenerate ground state with no hyperfine splitting, which is expected to simplify their photoassociation spectra to a great extent. This advantage in the theoretical description is paid for by difficulties in the experimental observation of photoassociation. The ensembles of laser cooled alkaline earths are less cold and less dense than those of e.g. alkalines which were used in most of the photoassociation experiments until now. Photoassociation of Ca is achieved by exciting atomic pairs to the B/sup 1//spl Sigma//sub n//sup +/ excited state of Ca corresponding to an atomic pair 4s/sup 2/ /sup 1/S/sub 0/+4s4p /sup 1/P/sub 1/ at large nuclear distances R. The dimer is bound by the resonant dipole interaction. Due to acceleration in this R/sup -3/-potential, atoms decaying at a smaller nuclear distance usually have sufficient kinetic energy to leave the magneto-optical trap. By measuring the trap loss dependent on the frequency of a photoassociation laser red-detuned to the /sup 1/S/sub 0/-/sup 1/P/sub 1/ transition we resolved the vibrational and rotational structure of the molecule. From the positions of the observed vibrational levels, corrected for the partially unresolved rotational structure and the thermal energy distribution of the ground state atoms, the atomic radiation decay rate /spl gamma/=2.180(11)/spl middot/10/sup 8/ s/sup -1/ of level 4s4p /sup 1/P/sub 1/ is derived with an uncertainty reduced by nearly one order of magnitude compared to previous measurements.