Laser Excitation of the 229-Th Nuclear Isomer

离子捕获和冷却的AMO技术以及高分辨率光谱将被应用于核激发态的操纵。虽然典型的核激发能在keV到mev的范围内，但也有几种例外情况下的激发能要低得多。独特的是，钍-229同位素在紫外光光谱中具有激发态。由于原子核内部强相互作用和弱相互作用的相互作用，原子核的转变很可能对基本常数的变化特别敏感。此外，它还提供了一种对外部电磁场扰动(包括黑体辐射)的敏感度大大降低的光学钟。在前期工作中，Th-232(232Th~(3+))的三电荷离子在RF-Paul陷阱中被限制和激光冷却。我们现在将捕获并激光冷却229Th3+。通过超快激光的倍频多光子激发，电子-核耦合(所谓的电子-桥机制)将帮助寻找同质态。一旦发现了转变，将对异构体的电子态进行光学光谱分析。这将确定在这个系统中寻找精细结构常数α随时间变化的增强因子，解决了一个正在进行的理论争论。这项研究将在几个物理和技术领域产生广泛的影响。激光激发和对核态的相干操纵将在原子物理和核物理之间建立一座新的桥梁，并有望开发新技术，特别是在精密计量领域。此外，这项研究将为从事原子、光学和核物理领域工作的新一代科学家提供培训和专业知识。

AMO technologies of ion trapping and cooling and high resolution spectroscopy will be applied to the manipulation of a nuclear excited state. While typical nuclear excitation energies are in the keV to MeV range, there are several exceptional cases where the excitation energies are much lower. The Thorium-229 isotope, uniquely, has an excited state in the UV optical spectrum. The nuclear transition is likely to be exceptionally sensitive to variation of fundamental constants, due to the interplay of the strong and electroweak interactions inside this nucleus. Additionally, it offers a prospect of an optical clock substantially less sensitive to external electromagnetic field perturbations, including black-body radiation. In preliminary work triply-charged ions of Thorium 232 (232Th3+) have been confined and laser cooled in an rf Paul trap. We will now trap and laser cool 229Th3+. The isomer state search will be assisted by the electron-nuclear coupling (the so-called electron-bridge mechanism), via multi-photon excitation with harmonics of an ultra-fast laser. Once the transition has been found, optical spectroscopy of the electronic states of the isomer will be performed. This should determine the enhancement factor for the search of time variation of fine structure constant alpha in this system, resolving an ongoing theoretical controversy.This research will have broad impact across several areas of physics and technology. Laser excitation and coherent manipulation of nuclear states would establish a new bridge between atomic and nuclear physics, with the promise for new technologies, particularly in the area of precision metrology. In addition, this research will provide training and expertise for a new generation of scientists working on the boundaries of atomic, optical and nuclear physics.