Electronic level structure of ${\mathrm{Th}}^{+}$ in the range of the ${}^{229m}\mathrm{Th}$ isomer energy

Abstract

Using resonant two-step laser excitation of trapped ${}^{232}{\mathrm{Th}}^{+}$ ions, we observe 166 previously unknown energy levels of even parity within the energy range from 7.8 to 9.8 eV and angular momenta from $J=1/2$ to $7/2$. We also classify the high-lying levels observed in our earlier experiments by the total angular momentum and perform ab-initio calculations to compare their results with the observed level density. The observed levels can be relevant for the excitation or decay of the ${}^{229m}\mathrm{Th}$ isomeric nuclear state which lies in this energy range. The high density of electronic levels promises a strongly enhanced electronic bridge excitation of the isomer in ${}^{229}{\mathrm{Th}}^{+}$.

arXiv comment10 pages, 4 figures, 4 tables; 2 figures updated, 1 reference added, section 5 updated

References in corpus (12)

• A new list of thorium and argon spectral lines in the visible
• Lifetime measurement of the ${}^{229}$Th nuclear isomer
• Excitation of the isomeric ^{229m}Th nuclear state via an electronic bridge process in ^{229}Th^+
• Nuclear clocks based on resonant excitation of gamma-transitions
• Effect of atomic electrons on 7.6 eV nuclear transition in ${}^{229}$Th${}^{3+}$
• The Spectrum of Thorium from 250 nm to 5500 nm: Ritz Wavelengths and Optimized Energy Levels
• Energy levels of Th+ between 7.3 and 8.3 eV
• Two-photon laser excitation of trapped 232Th+ ions via the 402 nm resonance line
• Exponential increase of energy level density in atoms: Th and Th II
• Impact of the ionization of the atomic shell on the lifetime of the 229mTh isomer
• Impact of the ionization of the atomic shell on the lifetime of the ${}^{229m}$Th isomer
• Observation of an unexpected negative isotope shift in 229Th+ and its theoretical explanation

Cited by in corpus (5)

• Electronic bridge excitation in highly charged Th-229 ions
• The ${}^{229}$Th isomer: prospects for a nuclear optical clock
• Ground-state $g$ factor of highly charged ${}^{229}$Th ions: an access to the M1 transition probability between the isomeric and ground nuclear states
• Prediction of Nuclear Clock Transitions Frequency Difference between ${}^{229}$Th${}^{3+}$ and ${}^{229}$Th${}^{4+}$ via \textit{ab-initio} Self-Consistent Field Theory
• Lifetime of the singly charged ${}^{229}$Th nuclear isomer