A new method for studying laser and electron interactions for a wide range of atomic targets - collision studies in an optical enhancement cavity

研究各种原子目标的激光和电子相互作用的新方法 - 光学增强腔中的碰撞研究

• 批准号: EP/G068690/1
• 负责人: Andrew Murray
• 金额: $ 69.38万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG068690%2F1
• 关键词: new; method; studying; laser; electron

One of the most fundamental processes to be understood in physics is how atoms are excited by collision with different particles such as electrons. This process occurs in many areas from the production of lighting, the development of lasers, ionospheric and atmospheric processes of importance to climate change, lightning discharges, astrophysical processes as in stars and planets, the spectroscopy of atoms and molecules and in all industries using electricity. It is essential to understand these processes at a fundamental level so new technologies can be developed, and so we can apply our knowledge to further understanding of climate change and the structure of the universe.The most detailed information on these processes is obtained by experimentally determining the 'shape' of an excited atom following inelastic scattering of an electron. We can do this by studying the light emitted from the atom as it relaxes back to the ground state. The result of these studies as a function of the electron scattering angle are then compared to predictions from sophisticated quantum theories. A new technique recently developed in Manchester allows us to measure the shape of the atom over ALL scattering angles - a task that has been impossible previously. These experiments use a specially designed magnetic field to steer electrons to and from the interaction region so all angles can be accessed. A laser beam prepares the atoms in an excited state prior to the collision, and so the electrons scatter with more energy than they had prior to the collision (super-elastic scattering). We then detect these higher energy electrons as a function of properties of the laser beam. The experiments therefore effectively reverse time - instead of starting with an electron and then looking for a photon from the excited atom, we start with a laser photon and then look for the emerging electron! By doing this, the experiments produce data thousands of times faster than using standard techniques (since the laser beam is always sent in the same direction). By adopting these methods, we can very precisely determine the shape of the atom for comparison to theory (now being developed in the USA and Australia).The apparatus in Manchester is now the most sophisticated super-elastic scattering spectrometer in the world, and has produced data never seen before. We wish to significantly extend these studies here, by incorporating an optical technique which allows us to excite many more targets than is currently possible (up to 25 new targets will be accessible compared to those which can be excited at present). To facilitate this, we will place high reflectivity mirrors around the interaction region to act as a 'storage' of light inside the spectrometer. This 'optical cavity' allows the laser power between the mirrors to be increased by up to 50 times compared to that directly from the laser. We will use this new technique to prepare atoms using UV laser radiation for the first time. Super-elastically scattered electrons will then be detected from the excited atoms, which will include zinc, silver and gold targets. These are of interest for new lighting technologies (which are currently considering using zinc as a replacement for the environmentally toxic mercury in fluorescent and UV lights), and for comparison to new quantum theories being developed to describe these complex atoms.As part of this programme we will also develop a new type of external doubling cavity that can excite two laser frequencies simultaneously from the one laser beam. This is necessary for excitation of atoms with hyperfine structure (including gold and silver), where the nuclear spin splits the energy level of the ground state. The new type of doubling cavity we will develop here will have application in a wide range of different areas of laser and atomic physics, as will the development and implementation of the optical cavity enhancement inside the spectrometer.

物理学中最基本的过程之一是原子如何通过与电子等不同粒子的碰撞而被激发。这一过程发生在许多领域，从照明的产生、激光的发展、对气候变化具有重要意义的电离层和大气层过程、闪电放电、恒星和行星中的天体物理过程、原子和分子的光谱学以及所有使用电力的工业。必须从根本上理解这些过程，以便开发新技术，因此，我们可以利用我们的知识来进一步了解气候变化和宇宙的结构。关于这些过程的最详细的信息是通过实验确定电子非弹性散射后激发原子的“形状”来获得的。我们可以通过研究原子发出的光来做到这一点因为它会松弛回到基态。这些研究的结果作为电子散射角的函数，然后从复杂的量子理论的预测进行比较。最近在曼彻斯特开发的一种新技术使我们能够在所有散射角度上测量原子的形状-这是以前不可能完成的任务。这些实验使用专门设计的磁场来引导电子进出相互作用区域，因此可以访问所有角度。激光束使原子在碰撞前处于激发态，因此电子以比碰撞前更多的能量散射（超弹性散射）。然后，我们检测到这些更高能量的电子作为激光束的属性的函数。因此，实验有效地逆转了时间-而不是从一个电子开始，然后从激发的原子中寻找光子，我们从一个激光光子开始，然后寻找出现的电子！通过这样做，实验产生的数据比使用标准技术快数千倍（因为激光束总是沿着同一方向发送）。通过采用这些方法，我们可以非常精确地确定原子的形状，并与理论进行比较（目前正在美国和澳大利亚开发）。曼彻斯特的设备现在是世界上最先进的超弹性散射光谱仪，并产生了前所未有的数据。我们希望在这里大大扩展这些研究，通过结合一种光学技术，使我们能够激发比目前可能的更多的目标（与目前可以激发的目标相比，将有多达25个新的目标）。为了促进这一点，我们将在相互作用区域周围放置高反射率的镜子，作为光谱仪内部光的“存储”。与直接来自激光器的功率相比，这种“光学腔”允许反射镜之间的激光功率增加高达50倍。我们将首次使用这种新技术来利用紫外激光辐射制备原子。超弹性散射的电子将从激发的原子中被检测到，这些原子包括锌、银和金靶。这对新的照明技术（目前正在考虑使用锌作为荧光灯和紫外线灯中对环境有毒的汞的替代品）以及与正在开发的描述这些复杂原子的新量子理论的比较都很有意义。作为该计划的一部分，我们还将开发一种新型的外部倍频腔，它可以从一束激光束中同时激发两种激光频率。这对于具有超精细结构的原子（包括金和银）的激发是必要的，其中核自旋分裂基态的能级。我们将在这里开发的新型倍频腔将在激光和原子物理的广泛不同领域中得到应用，光谱仪内部光学腔增强的开发和实施也将如此。

项目成果

Super-elastic electron scattering from the laser-excited 4 1 P 1 state of calcium at low incident energy

低入射能量下钙的激光激发 4 1 P 1 态的超弹性电子散射

• DOI: 10.1088/0953-4075/44/10/105203
• 发表时间: 2011
• 期刊: Atomic, Molecular and Optical Physics
• 作者: Knight-Percival A

Theoretical and experimental ( e , 2 e ) study of electron-impact ionization of laser-aligned Mg atoms

激光对准镁原子电子轰击电离的理论与实验 ( e , 2 e ) 研究

• DOI: 10.1103/physreva.90.062707
• 发表时间: 2014
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Amami S

Recent theoretical progress in treating electron impact ionization of molecules

处理分子电子碰撞电离的最新理论进展

• DOI: 10.1088/1742-6596/212/1/012004
• 发表时间: 2010
• 期刊: Conference Series
• 作者: Al-Hagan O

Evidence for unnatural-parity contributions to electron-impact ionization of laser-aligned atoms

激光排列原子电子轰击电离的非自然宇称贡献的证据

• DOI: 10.1103/physreva.92.032706
• 发表时间: 2015
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Armstrong G

Parametrization of electron-impact ionization cross sections from laser-excited and aligned atoms.

激光激发和排列原子的电子碰撞电离截面的参数化。

• DOI: 10.1103/physrevlett.112.023202
• 发表时间: 2014
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: Nixon KL