Precision Vibrational Spectroscopy of Single Molecular Hydrogen Ions in a Penning trap

该项目的主题是“基本常数的计量学”和“寻找超越标准模型的物理学”。它建议开发高精度的分子氢离子（MHI）光谱作为这些主题的探针。标准模型的相对论量子场论在微观层面上非常成功地描述了我们的世界。电荷-宇称-时间不变性（CPTI）深入到这些理论的假设中。几十年来，CPTI一直是实验测试的主题，测试的精度稳步提高。但必须继续进一步提高精度。事实上，违反CPTI提供了一条可能的途径来解释在宇宙学尺度上观察到的惊人的物质-反物质不平衡。目前，欧洲核子研究中心的反物质工厂正在进行CPTI测试的高级研究项目。它们涉及电子和质子的质量和电荷，以及质子和它们的反粒子的核性质。它们是由潘宁陷阱光谱和H-棒光谱进行的，并且肯定会在未来几年内得到改进。现在，一个全新的选择正在出现：CPTI测试包括比较分子氢离子H_2^+和反H_2 ^+的振动频率。这些频率是感兴趣的，因为它们对质子/反质子，电子/正电子的质量具有一阶灵敏度，对核电荷半径具有（小）灵敏度。可以通过激光光谱学和光学频率计量学精确地确定频率。MHI可以相对容易地在离子阱中被捕获和冷却，从而允许高分辨率光谱。理论分析表明，在1 E-17范围内的分数不确定度应该是可行的，远低于潘宁阱质谱将永远实现。此外，振动频率还取决于两个原子核之间的库仑相互作用，因此H_2^+与反H_2 ^+的比较也可以实现对p-p-bar相互作用的精确CPTI检验，这是目前的实验所不能提供的。能够一次储存带电反物质粒子数月的既定陷阱类型是潘宁陷阱。因此，在本项目中，我们的目标是首次证明MHI在低温潘宁阱中的振动光谱是可能的，并旨在达到第一个里程碑，即H_2^+和HD^+的1 E-12分数不确定度。MHI的振动跃迁频率的知识可以用来确定核与电子的质量比，并设置上限的假设两个核之间的附加力，由暗物质粒子介导。要做到这一点，实验频率必须面对从头算预测。在这个项目中，我们将首次直接获得m_e/m_p的光谱值，其不确定度可与最好的直接质量测量相媲美。

This project addresses the topics ``metrology of fundamental constants" and the ``search for beyond-Standard-Model Physics". It proposes to develop high-precision spectroscopy of molecular hydrogen ions (MHI) as a probe for these topics. Our world is very successfully described at the microscopic level by the relativistic quantum field theories of the Standard Model. Charge-parity-time invariance (CPTI) is deeply implemented into the assumptions of such theories. CPTI has been the subject of experimental tests for many decades, and the precision of the tests has steadily improved. But it is imperative to continue improving the precision further. In fact, a violation of CPTI provides one possible path to explain the striking matter-antimatter imbalance that is observed on cosmological scales. Currently, advanced research programs on CPTI tests are being conducted at CERN’s antimatter factory. They address the mass and charge of electron and proton as well as and nuclear properties of the proton, and of their antiparticles. They are performed by Penning trap spectroscopy and by H-bar spectroscopy and will certainly improve over the years to come. Now, a completely new option is emerging: A CPTI test consisting in comparing the vibrational frequencies of the molecular hydrogen ions H_2^+ and anti-H_2^+. These frequencies are of interest because they have a first-order sensitivity to the masses of the proton/antiproton, electron/positron and a (small) sensitivity to the nuclear charge radius. The frequencies can be determined accurately by laser spectroscopy and optical frequency metrology. MHI can relatively easily be trapped and cooled in an ion trap, permitting high-resolution spectroscopy. Theoretical analyses indicate that fractional uncertainties in the 1E-17 range should be feasible, much lower than Penning trap mass spectroscopy will ever achieve. Moreover, vibrational frequencies also depend on the Coulomb interaction between the two nuclei, therefore a H_2^+ to anti-H_2^+ comparison would also implement a precision CPTI test of the p – p-bar interaction, which no current experiment can provide. The established trap type capable of storing charged anti-matter particles for months at a time is the Penning trap. Therefore, in this project we aim to demonstrate, for the first time, that vibrational spectroscopy of MHI in a cryogenic Penning trap is possible, and aim to reach a first milestone, 1E-12 fractional uncertainty, for both H_2^+ and HD^+. Knowledge of vibrational transition frequencies of the MHI can serve to determine the ratios of nuclear-to-electron mass, and to set upper bounds to a hypothetical additional force between the two nuclei, mediated by a dark-matter particle. To do so, the experimental frequencies must be confronted with ab initio predictions. In this project, we will for the first time obtain directly a spectroscopic value of m_e/m_p with an uncertainty competitive with the best direct mass measurements.