摘要:
本文首先在Dirac-Hartree-Fock近似下理论评估了Hg+离子5d106s 2S1/2→5d96s2 2D5/2钟跃迁的质量位移(mass shift,MS)和场位移(field shift,FS)在其同位素位移(isotope shift,IS)中的相对贡献,发现MS远小于FS而可以被忽略.在此基础上,通过系统地考虑该原子体系中主要的电子关联效应,计算了这条钟跃迁FS的精确值以及涉及到的上下两个能级的超精细结构常数,并得到了几种稳定汞同位素离子该跃迁的IS和超精细结构分裂.其中,计算的199Hg+和198Hg+离子之间的钟跃迁频率偏移与已有实验测量值相比误差为2%左右.最终,本文给出了汞离子7种常见同位素该谱线的绝对频率值,为实验上的谱线测量提供了有效的理论依据.%The Dirac-Hartree-Fock approximation is adopted to calculate the mass shift and the field shift for the 5d106s 2S1/2→5d96s2 2D5/2 clock transition in Hg+. It is found that the field shift is much larger than the mass shift so that the latter can be neglected in the isotope shift. In addition, we estimate that the isotope shifts of the levels related to the 5d106s 2S1/2→5d96s2 2D5/2 clock transition of Hg+ is on the order of about 104 GHz, while the hyperfine structure splitting is in a range of 1?10 GHz. However, the isotope shift of the 5d106s 2S1/2→5d96s2 2D5/2 clock transition is on the same order of magnitude as the hyperfine structure splitting. Therefore, the hyperfine structure splitting must be taken into account for predicting the frequency shifts of the clock transition between different isotopes. On the basis of these results, we perform a multi-configuration Dirac-Hartree-Fock calculation on the field shift of the 5d106s 2S1/2→5d96s2 2D5/2 clock transition in Hg+ and the hyperfine interaction constants of the upper and the lower levels involved. In order to give accurate theoretical results of these physical quantities, we systematically consider the main electron correlations in the atomic system by using the active space method. The restricted single and double (SrD) excitation method is used to capture the correlation between the 5d and the 6s valence electrons, and the correlation between the 3s, 3p, 3d, 4s, 4p, 4d, 5s, 5p, and 5d core and the valence electrons. The isotope shifts and hyperfine structure splitting for this transition of several stable mercury isotopes are given. In particular, the uncertainty of the calculated isotope shift between 199Hg+ and 198Hg+ is about 2%, compared with the experimental measurement available. Using these results, we predict the absolute frequency values of this transition for seven mercury isotopes, which provides theoretical reference data for experiments. Moreover, the calculated isotope shifts and hyperfine structures are also useful for studying the structure, property and nucleon interaction of mercury nucleus.