2012/11/04 by Lars von der Wense, L. v. d. Wense, P. G. Thirolf +2 · 26 citations
Physics and Astronomy · #Advanced Frequency and Time Standards #Atomic and Molecular Physics #Atomic physics #Cold Atom Physics and Bose-Einstein Condensates #Excitation #Excited state #Ground state #Physics #Quantum mechanics #Zeeman effect #nucl-ex
paper · pdf · doi:10.1088/1748-0221/8/03/p03005
published in Journal of Instrumentation 8(03), P03005 (Institute of Physics)
arxiv created 2012/11/04 · openalex publication_date 2013/03/08 · arxiv updated 2015/06/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
The isomeric first excited state of the isotope 229 Th exhibits the lowest nuclear excitation energy in the whole landscape of known atomic nuclei. For a long time this energy was reported in the literature as 3.5(5) eV, however, a new experiment corrected this energy to 7.6(5) eV, corresponding to a UV transition wavelength of 163(11) nm. The expected isomeric lifetime is τ = 3-5 hours, leading to an extremely sharp relative linewidth of Δ E / E ≈ 10 −20 , 5-6 orders of magnitude smaller than typical atomic relative linewidths. For an adequately chosen electronic state, the frequency of the nuclear ground-state transition will be independent from influences of external fields in the framework of the linear Zeeman and quadratic Stark effect, rendering 229 m Th a candidate for a reference of an optical clock with very high accuracy [1]. Moreover, in the literature speculations about a potentially enhanced sensitivity of the ground-state transition of 229 m Th for eventual time-dependent variations of fundamental constants (e.g. fine structure constant α) can be found [3,4]. We report on our experimental activities that aim at a direct identification of the UV fluorescence of the ground-state transition energy of 229 m Th. A further goal is to improve the accuracy of the ground-state transition energy as a prerequisite for a laser-based optical control of this nuclear excited state, allowing to build a bridge between atomic and nuclear physics and open new perspectives for metrological as well as fundamental studies.