Molecular frequency metrology: ultra-high precision spectroscopy of the rotational transition of HD+

分子氢离子的精密光谱学提供了一种通过替代光谱手段来确定原子物理学的几个基本常数的方法。直到最近，这些分子离子的光谱受到多普勒展宽的限制，这也限制了可实现的精度。在申请人的小组中，最近开发了一种新的旋转光谱技术，其实现了Lamb-Dicke区域。光谱分辨率比多普勒展宽低40倍。这一突破为精密光谱学开辟了重要的新前景。在本项目中，该技术将在分辨率（因子10）和准确度（因子100）方面得到进一步发展。将对几个实验扩展进行测试和表征，作为结果，该项目将确定分子HD+中的一个旋转频率和两个超精细分裂，相对于旋转频率的分数不确定度为2×10^-11。同时，合作伙伴将进一步发展自旋相关能量贡献的从头算理论。通过比较实验结果和理论结果，我们打算在分数不确定度为3×10^-11（比目前精确30倍）的情况下检验从头算量子理论，并将其结果用于确定电子质量与约化质子-氘核质量之比me/mp + me/md。目标不确定度为3×10^-11，这将允许独立地确认在潘宁阱中获得的最精确值。如果发现一致，则两个值一起可以导致CODATA基本常数编译的改进值。

Precision spectroscopy of molecular hydrogen ions provides an approach for determining several fundamental constants of atomic physics by alternative spectroscopic means. Until recently, the spectroscopy of these molecular ions was limited by Doppler broadening, which also limited the achievable precision. In the group of the applicant a new rotational spectroscopy technique was recently developed, which achieves the Lamb-Dicke regime. The spectral resolution was a factor 40 below the Doppler broadening. With this breakthrough important new perspectives open up in precision spectroscopy. In this project, the technique shall be developed further both in terms of resolution (by a factor 10) and in terms of accuracy (by a factor 100). Several experimental extensions shall be tested and characterized.As outcome, the project shall determine one rotational frequency and two hyperfine splittings in the molecule HD+, with fractional uncertainty 2×10^-11 relative to the rotational frequency. In parallel, the cooperation partners will develop the ab initio theory of the spin-dependent energy contributions further. By comparing the experimental and theoretical results we intend to test the ab initio quantum theory with a fractional uncertainty of 3×10^-11, 30 times more accurately than so far.The results will also be used to determine the ratio of electron mass to reduced proton-deuteron-mass, me/mp + me/md. The goal uncertainty, 3×10^-11, will allow to independently confirm the most precise value, obtained in Penning traps. If agreement is found, both values together can lead to an improved value for the CODATA fundamental constants compilation.