Lifetime measurement of the ${}^{229}$Th nuclear isomer

Abstract

The first excited isomeric state of ${}^{229}$Th possesses the lowest energy among all known excited nuclear states. The expected energy is accessible with today's laser technology and in principle allows for a direct optical laser excitation of the nucleus. The isomer decays via three channels to its ground-state (internal conversion, $\gamma$ decay and bound internal conversion), whose strengths depend on the charge state of ${}^{229m}$Th. We report on the measurement of the internal-conversion decay half-life of neutral ${}^{229m}$Th. A half-life of 7 $\pm$ 1 $\mu$s has been measured, which is in the range of theoretical predictions and, based on the theoretically expected lifetime of $\approx 10^4$ s of the photonic decay channel, gives further support for an internal conversion coefficient of $\approx 10^9$, thus constraining the strength of a radiative branch in the presence of IC.

8 pages, 4 Figures

References in corpus (5)

• Direct detection of the 229Th nuclear clock transition
• Enhanced effect of temporal variation of the fine structure constant in diatomic molecules
• Proposal for a Nuclear Gamma-Ray Laser of Optical Range
• Excitation of the isomeric ^{229m}Th nuclear state via an electronic bridge process in ^{229}Th^+
• Determination of the extraction efficiency for ${}^{233}$U source $\alpha$-recoil ions from the MLL buffer-gas stopping cell

Cited by in corpus (17)

• Measurement of the ${}^{229}$Th isomer energy with a magnetic micro-calorimeter
• A laser excitation scheme for ${}^{229\text{m}}$Th
• Excitation of ${}^{229m}$Th at Inelastic Scattering of Low Energy Electrons
• ${}^{229m}$Th isomer from a nuclear model perspective
• XUV frequency comb operation in an astigmatism-compensated enhancement cavity
• Tunable VUV Frequency Comb for ${}^{229m}$Th Nuclear Spectroscopy
• Excitation of the ${}^{229}$Th nucleus via a two-photon electronic transition
• Internal conversion from excited electronic states of ${}^{229}\mathrm{T}h$ ions
• Electronic level structure of ${\mathrm{Th}}^{+}$ in the range of the ${}^{229m}\mathrm{Th}$ isomer energy
• Estimation of radiative half-life of ${}^{229m}$Th by half-life measurement of other nuclear excited states in ${}^{229}$Th
• The concept of laser-based conversion electron Mössbauer spectroscopy for a precise energy determination of ${}^{229m}$Th
• Catching, trapping and in-situ-identification of thorium ions inside Coulomb crystals of ${}^{40}$Ca${}^{+}$ ions
• Internal conversion of the low energy ${}^{229m}$Th isomer in the Thorium anion
• Development of a recoil ion source providing slow Th ions including ${}^{229(m)}$Th in a broad charge state distribution
• A proposed solution for the lifetime puzzle of the 229mTh+ isomer
• Production and chemical separation of ${}^{229}$Pa toward observation of $\gamma$ rays of ${}^{229\mathrm{m}}$Th
• 'Phase Transition' in the 'Thorium-Isomer Story'