Study of thorium in hypersonic gas jets: Ionization potentials of Th and Th$^+$
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866913965207977984 |
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| author | Claessens, A. Ivandikov, F. Brasseur, M. Dragoun, A. Düllmann, Ch. E. Ferrer, R. Kudryavtsev, Yu. Palmeri, P. Quinet, P. Raeder, S. Renisch, D. Bergh, P. Van den Van Duppen, P. |
| author_facet | Claessens, A. Ivandikov, F. Brasseur, M. Dragoun, A. Düllmann, Ch. E. Ferrer, R. Kudryavtsev, Yu. Palmeri, P. Quinet, P. Raeder, S. Renisch, D. Bergh, P. Van den Van Duppen, P. |
| contents | Laser ionization spectroscopy was performed on both neutral and singly ionized $^{232}$Th with the aim of identifying the nuclear-clock isomer in the singly charged ionic state of $^{229}$Th. A search for an efficient laser ionization scheme of $^{232}$Th$^+$ was conducted in an argon-filled gas cell. This revealed a congested spectrum due to collisional quenching effects and the presence of several auto-ionizing states, one of which has a laser ionization efficiency of at least $1.2 \%$. Using a threshold approach, the second ionization potential was determined to be $12.300(9)\,$eV. The subsequent study on atomic $^{232}$Th validated the threshold approach. Conducting spectroscopy in a hypersonic gas jet, suppressed the gas-collision-induced quenching, revealing a Rydberg series that converges to the first ionization potential, determined to be $6.306879(14)\,$eV. The gas jet also cools down the thorium, allowing for high-resolution laser spectroscopy with a resolution of $240(30)\,$MHz. Using the Multiconfigurational Dirac-Hartree-Fock (MCDHF) method, the ionization potentials were computed, showing a relative difference of 0.06\% and 0.19\% between theory and our experimental values for the ionization potentials of Th and Th$^+$ respectively. Further calculations using a pseudo-relativistic Hartree-Fock method reveal strong mixing in the used intermediate state at $26113.27\,$cm$^{-1}$ of Th. A dedicated fast-extraction gas cell with $^{233}$U recoil sources was used to study $^{229}$Th$^+$ but no photo-ionization signal could be observed. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_21946 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Study of thorium in hypersonic gas jets: Ionization potentials of Th and Th$^+$ Claessens, A. Ivandikov, F. Brasseur, M. Dragoun, A. Düllmann, Ch. E. Ferrer, R. Kudryavtsev, Yu. Palmeri, P. Quinet, P. Raeder, S. Renisch, D. Bergh, P. Van den Van Duppen, P. Atomic Physics Nuclear Experiment Laser ionization spectroscopy was performed on both neutral and singly ionized $^{232}$Th with the aim of identifying the nuclear-clock isomer in the singly charged ionic state of $^{229}$Th. A search for an efficient laser ionization scheme of $^{232}$Th$^+$ was conducted in an argon-filled gas cell. This revealed a congested spectrum due to collisional quenching effects and the presence of several auto-ionizing states, one of which has a laser ionization efficiency of at least $1.2 \%$. Using a threshold approach, the second ionization potential was determined to be $12.300(9)\,$eV. The subsequent study on atomic $^{232}$Th validated the threshold approach. Conducting spectroscopy in a hypersonic gas jet, suppressed the gas-collision-induced quenching, revealing a Rydberg series that converges to the first ionization potential, determined to be $6.306879(14)\,$eV. The gas jet also cools down the thorium, allowing for high-resolution laser spectroscopy with a resolution of $240(30)\,$MHz. Using the Multiconfigurational Dirac-Hartree-Fock (MCDHF) method, the ionization potentials were computed, showing a relative difference of 0.06\% and 0.19\% between theory and our experimental values for the ionization potentials of Th and Th$^+$ respectively. Further calculations using a pseudo-relativistic Hartree-Fock method reveal strong mixing in the used intermediate state at $26113.27\,$cm$^{-1}$ of Th. A dedicated fast-extraction gas cell with $^{233}$U recoil sources was used to study $^{229}$Th$^+$ but no photo-ionization signal could be observed. |
| title | Study of thorium in hypersonic gas jets: Ionization potentials of Th and Th$^+$ |
| topic | Atomic Physics Nuclear Experiment |
| url | https://arxiv.org/abs/2507.21946 |