Maksim V. Okhapkin | Searcharxiv

arXiv2025

Continuous-wave laser source at the 148 nm nuclear transition of Th-229

A continuous-wave laser source at 148.4 nm based on second-harmonic generation in randomly quasi-phase matched strontium tetraborate, SrB4O7, is demonstrated. It provides (1.3-0.6+0.7) nW of VUV power in a single pass for an incident UV laser power of 325 mW. The laser system is developed for the resonant laser excitation of the 229Th nucleus to its low-energy isomeric state. For a frequency-stabilized laser system we expect to reach similar VUV power spectral densities as in previous pulsed laser excitation experiments of the nuclear transition in 229Th-doped crystals.

physics.optics↗

arXiv2019

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

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 $^{229}\mathrm{Th}^+$.

physics.atom-ph↗