On an attempt to optically excite the nuclear isomer in Th-229

Abstract

We aim to perform direct optical spectroscopy of the Th-229 nuclear isomer to measure its energy and lifetime, and to demonstrate optical coupling to the nucleus. To this end, we develop Th-doped CaF2 crystals, which are transparent at the anticipated isomer wavelength. Such crystals are illuminated by tunable VUV undulator radiation for direct excitation of the isomer. We scan a 5 sigma region around the assumed isomer energy of 7.8(5) eV and vary the excitation time in sequential scans between 30 and 600 seconds. Suffering from an unforeseen strong photoluminescence of the crystal, the experiment is sensitive only to radiative isomer lifetimes between 0.2 and 1.1 seconds. For this parameter range, and assuming radiative decay as the dominant de-excitation channel, we can exclude an isomer with energy between 7.5 and 10 eV at the 95% confidence level.

arXiv comment10 pages, 5 figures

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Cited by in corpus (17)

• Energy of the ${}^{229}$Th nuclear clock transition
• Measurement of the ${}^{229}$Th isomer energy with a magnetic micro-calorimeter
• X-ray pumping of the Th-229 nuclear clock isomer
• Nuclear excitation of the ${}^{229}$Th isomer via defect states in doped crystals
• The ${}^{229}$Th isomer: prospects for a nuclear optical clock
• Concepts for direct frequency-comb spectroscopy of ${}^{229\text{m}}$Th and an internal-conversion-based solid-state nuclear clock
• The theory of direct laser excitation of nuclear transitions
• Excitation of the ${}^{229}$Th nucleus via a two-photon electronic transition
• Recollision induced nuclear excitation of ${}^{229}$Th
• Driven electronic bridge processes via defect states in ${}^{229}$Th-doped crystals
• Excitation and probing of low-energy nuclear states at high-energy storage rings
• Collective effects in ${}^{229}$Th-doped crystals
• 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
• Towards an energy measurement of the internal conversion electron in the de-excitation of the Th-229 isomer
• Excitation of ${}^{229}$Th nuclei in laser plasma: the energy and half-life of the low-lying isomeric state
• Production and chemical separation of ${}^{229}$Pa toward observation of $\gamma$ rays of ${}^{229\mathrm{m}}$Th