Measurement of the unresolved ⁹Be⁺ ²P_3/2 hyperfine splittings using quantum-interference-enhanced state-selective repump spectroscopy, and progress toward ^7,9,10Be⁺ splitting isotope shift measurements using single trapped ions

Hyperfine splittings of the ²P_3/2 manifold in ⁹Be⁺ were measured directly using a single laser-cooled ion stored in a radiofrequency Paul trap. As the hyperfine structure is unresolved beneath the natural linewidth of the transition, manipulation of the initial state, polarization, and final-state populations was used to preferentially detect scattering events through specific intermediate excited states. While quantum interference effects typically complicate the modeling of unresolved measurement lineshapes, in this work quantum interference helped to suppress extraneous scattering components. The hyperfine splittings between the |²P_3/2, F=3> state and the |²P_3/2, F=2> and |²P_3/2, F=1> states were measured to be ν₃₂ = 0.801(56) MHz and ν₃₁ = 5.050(83) MHz, respectively. Following recent absolute frequency measurements of the D-lines and fine structure splitting in ⁹Be⁺, progress toward trapping and laser spectroscopy on rare isotopes ^7,10Be⁺ is presented. In addition, we present a demonstration of direct ablation loading of ⁹Be⁺ from small BeCl₂ deposits.