Precision spectroscopy of Rydberg Positronium

里德伯正电子的精密光谱

• 批准号: 2083394
• 金额: --
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2083394
• 关键词: Precision; spectroscopy; Rydberg; Positronium

Hydrogen is the testing ground for quantum physics and has been the subject of intense experimentation, providing very stringent tests of QED theory. Spectroscopy of this fundamental system is so advanced that it is now limited by our incomplete knowledge of the structure of the proton, which is not governed by QED and cannot be calculated with sufficient accuracy. In order to try and improve measurements of the proton structure some remarkable experiments were conducted using muonic hydrogen: this is a system in which the electron in a hydrogen atom is replaced with a muon. Although muons are intrinsically unstable and decay in a few microseconds, they can act as excellent probes of the charge radius of the proton because they are over 200 times more massive than electrons. These experiments [see R. Pohl, et al. "The size of the proton", Nature, 466 213 (2010)] have been very successful, providing a highly accurate measurement of the proton size. However, this improved precision has revealed a discrepancy with previous hydrogen spectroscopy and electron-proton scattering measurements that has not yet been explained, and is known as the "proton radius puzzle". This project aims to address the problem from a different perspective: instead of replacing the hydrogenic electron with a heavy muon, and thereby increasing the effect of the proton size, we will completely eliminate the effect by replacing the proton with a positron. This positron-electron bound state is known as positronium and, even though it is intrinsically unstable and prone to self-annihilation, it can be studied via microwave and optical spectroscopy. In order to do this with sufficient precision we will need to use lasers to put the Ps atoms into highly-excited Rydberg states which prevents self-annihilation, significantly extending their lifetimes. Moreover, the motion of excited Rydberg states can be controlled via external electric fields owing to their large dipole moments, making it possible to generate a slow, long-lived, and focused Ps atom beam. With a beam of atoms that live for a long time we can directly measure how they fall in the gravitational field of the earth. This will help answer the question: does antimatter fall differently to matter? If the answer is not "no" there will be profound implications for our existing physical theories. Similarly, if the proton radius puzzle does not have a simple explanation it too may be a sign of exciting new physics. Whatever the answers to these questions are, this project will address them using cutting edge methods covering several areas of atomic and positronium physics, and will also require the development of many new techniques along the way.

氢是量子物理学的测试场，一直是强烈实验的主题，提供了非常严格的QED理论测试。该基本系统的光谱学是如此先进，以至于我们现在不完全了解质子的结构，该质子不受QED的控制，无法以足够的准确性来计算。为了尝试改善质子结构的测量值，使用Muonic氢进行了一些显着的实验：这是一个系统，其中氢原子中的电子被穆恩代替。尽管Muons本质上是不稳定的，并且在几微秒内腐烂，但它们可以充当质子电荷半径的出色探针，因为它们的质量是电子的200倍以上。这些实验[参见R. Pohl等。 “质子的大小”，自然，466 213（2010）]非常成功，提供了对质子大小的高度准确测量。然而，这种提高的精确度揭示了尚未解释的先前氢光谱和电子普罗氏骨散射测量的差异，被称为“质子半径拼图”。该项目的目的是从不同的角度解决该问题：我们将通过用正电子来代替质子来完全消除质子大小的效果，从而增加质子大小的效果，从而增加氢气电子的效果。这种正电子 - 电子结合状态被称为正电子，即使它本质上不稳定且容易自我宣布，也可以通过微波和光学光谱进行研究。为了以足够的准确性做到这一点，我们将需要使用激光将PS原子放入高度激发的Rydberg州，从而防止自我宣布，从而大大延长了其一生。此外，激发的Rydberg状态的运动可以通过外部电场来控制其大偶极矩，从而可以产生缓慢，寿命和焦点的PS原子束。有了长时间生存的原子光束，我们可以直接测量它们如何落入地球的重力场。这将有助于回答一个问题：反物质对重要的是不同吗？如果答案不是“否”，那么我们现有的物理理论将产生深远的影响。同样，如果质子半径难题没有简单的解释，则可能是令人兴奋的新物理学的迹象。无论这些问题的答案是什么，该项目都将使用涵盖原子和正电子物理的几个领域的尖端方法来解决它们，并且还需要一路发展许多新技术。