Laser Excitation of the 229-Th Nuclear Isomer

离子俘获和冷却的AMO技术以及高分辨率光谱学将被应用于核激发态的操纵。 虽然典型的核激发能在keV至MeV范围内，但也有几种例外情况，其中激发能要低得多。 钍-229同位素在紫外光谱中具有独特的激发态。由于该核内强相互作用和电弱相互作用的相互作用，核跃迁可能对基本常数的变化特别敏感。此外，它提供了一个光学时钟的前景基本上不敏感的外部电磁场扰动，包括黑体辐射。在初步工作中，钍232（232 Th 3+）的三重电荷离子已被限制和激光冷却的RF保罗陷阱。我们现在将捕获并激光冷却229 Th 3+。 同质异能态搜索将通过电子-核耦合（所谓的电子桥机制），通过超快激光谐波的多光子激发来辅助。 一旦发现跃迁，将进行异构体电子态的光谱分析。这应该确定在这个系统中的精细结构常数α的时间变化的搜索的增强因子，解决了正在进行的理论争议。 核态的激光激发和相干操纵将在原子物理和核物理之间建立一座新的桥梁，并有望产生新技术，特别是在精密计量领域。 此外，这项研究将为新一代从事原子、光学和核物理边界工作的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.