Frequency metrology of the HD+ molecular ion: THz and vibrational spectroscopy at the 10-10 accuracy level

HD ~+分子是最简单的分子之一，只有一个电子，它的振动跃迁频率的精确测量将最终使（i）测试精确计算分子能级的理论方法，（ii）建立一个新的测量分子中QED效应的系统/测试QED理论。（iii）以一种新的方式确定电子与质子的质量之比，其精确度可能高于其他方法;（iv）测量诸如四极矩的核特性，（v）检验核质量比的时间无关性。振动光谱，并以2.3ppb的相对精度测量跃迁频率。我们的实验结果与理论预测一致，并使α4阶QED贡献的测量精度达到10%左右，在本方案中，我们打算引入几个主要的实验改进，以达到接近2/10（0.2ppb）的精度，这是一个十倍的改进。在这个精度水平上，实验结果将挑战改进的理论公式和计算的QED和超精细效应。我们的测量可能会导致一个替代的电子-质子质量比的测定，与目前建立的approaches. Apart的准确性相似，除了在计量学中的应用，在拟议的项目中开发的新方法是广泛的兴趣，因为它们将适用于各种各样的其他分子离子。

The HD+ molecule is of fundamental importance because it is one of the simplest molecules, containing just a single electron. Precise measurement of its vibrational transition frequencies will ultimately allow (i) to test theoretical methods of precision calculation of molecular levels; (ii) establish a new System allowing to measure QED effects / test QED theory in molecules; (iii) to determine the ratio of electron-to-proton mass in a novel way and with potentially higher precision than with alternative methods; (iv) to measure nuclear properties such as quadrupole moments, (v) to test the time-independence of nuclear mass ratios.We have recently performed ro-vibrational spectroscopy and measured the transition frequency with a relative accuracy of 2.3 parts per billion (ppb). Our experimental result is in agreement with theoretical predicitions that were obtained shortly before and allowed the determination of QED contributions of order α4 to about 10% accuracy.In this proposal, we intend to introduce several major experimental improvements in order to reach an accuracy close to the level of 2 parts in 1010 (0.2 ppb), a tenfold improvement. At this level of accuracy, the experimental results will challenge an improved theoretical formulation and calculation of the QED and hyperfine effects. Our measurements could lead to an alternative determination of the electron-to-proton mass ratio, with an accuracy similar to that of currently established approaches.Apart from this application in metrology, the new methods to be developed in the proposed project are of wide interest since they will be applicable to a large variety of other molecular ions.