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arXiv · 1305.0765

Energy levels of Th+ between 7.3 and 8.3 eV

O. A. Herrera-Sancho·N. Nemitz·M. V. Okhapkin·E. Peik
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Abstract

Using resonant two-step laser excitation of trapped 232Th+ ions, we observe 43 previously unknown energy levels within the energy range from 7.3 to 8.3 eV. The high density of states promises a strongly enhanced electronic bridge excitation of the 229mTh nuclear state that is expected in this energy range. From the observation of resonantly enhanced three-photon ionization of Th+, the second ionization potential of thorium can be inferred to lie within the range between 11.9 and 12.3 eV. Pulsed laser radiation in a wide wavelength range from 237 to 289 nm is found to provide efficient photodissociation of molecular ions that are formed in reactions of Th+ with impurities in the buffer gas, leading to a significantly increased storage time for Th+ in the ion trap.

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O. A. Herrera-Sancho, N. Nemitz, M. V. Okhapkin, E. Peik. 2013-05-03. Energy levels of Th+ between 7.3 and 8.3 eV. https://doi.org/10.1103/physreva.88.012512

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