Towards a direct transition energy measurement of the lowest nuclear excitation in 229Th

Abstract

The isomeric first excited state of the isotope 229Th 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 $\tau =$ 3-5 hours, leading to an extremely sharp relative linewidth of Delta 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 229mTh a candidate for a reference of an optical clock with very high accuracy. Moreover, in the literature speculations about a potentially enhanced sensitivity of the ground-state transition of ${}^{229m}$Th for eventual time-dependent variations of fundamental constants (e.g. fine structure constant alpha) can be found. We report on our experimental activities that aim at a direct identification of the UV fluorescence of the ground-state transition energy of 229mTh. 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.

References in corpus (13)

• A Single-Ion Nuclear Clock for Metrology at the 19th Decimal Place
• Enhanced effect of temporal variation of the fine structure constant in diatomic molecules
• Proposal for a Nuclear Gamma-Ray Laser of Optical Range
• Performance of a 229 Thorium solid-state nuclear clock
• A proposed experimental method to determine $\alpha$-sensitivity of splitting between ground and 7.6 eV isomeric states in Th-229
• Excitation of the isomeric ^{229m}Th nuclear state via an electronic bridge process in ^{229}Th^+
• Electronic bridge process in 229Th^+
• Enhanced effect of quark mass variation in 229Th and limits from Oklo data
• On Th229 and time-dependent fundamental constants
• Resonance ionization spectroscopy of thorium isotopes - towards a laser spectroscopic identification of the low-lying 7.6 eV isomer of Th-229
• Coulomb energy contribution to the excitation energy in ${}^{229}$Th and enhanced effect of $\alpha$ variation
• Prospects for a Nuclear Optical Frequency Standard based on Thorium-229
• Enhanced effect of temporal variation of the fine structure constant and strong interaction in 229Th

Cited by in corpus (14)

• Searching for dilaton dark matter with atomic clocks
• Direct detection of the 229Th nuclear clock transition
• Lifetime measurement of the ${}^{229}$Th nuclear isomer
• Nuclear clocks based on resonant excitation of gamma-transitions
• The ${}^{229}$Th isomer: prospects for a nuclear optical clock
• Radioluminescence and photoluminescence of Th:CaF${}_2$ crystals
• Coherence-enhanced optical determination of the ${}^{229}$Th isomeric transition
• Determination of the extraction efficiency for ${}^{233}$U source $\alpha$-recoil ions from the MLL buffer-gas stopping cell
• Towards a 229Th-based nuclear clock
• Measuring the Th-229 nuclear isomer transition with U-233 doped crystals
• Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter
• Feasibility Study of Internal Conversion Electron Spectroscopy of ${}^{229m}$Th
• The extraction of 229Th3+ from a buffer-gas stopping cell
• A VUV detection system for the direct photonic identification of the first excited isomeric state of ${}^{229}$Th