Extended Data Fig. 3: Determination of the resonance frequency \(({{\boldsymbol{\nu }}}_{{\bf{m}},{\bf{HF}}}^{690})\) of the |5f 2F5/2, Fm = 1⟩ → |6d 2D5/2, Fm = 2⟩ transition.
From: Laser spectroscopy of triply charged 229Th isomer for a nuclear clock
a, The spectra of the |5f 2F5/2, Fm = 1⟩ → |6d 2D3/2, Fm = 2⟩ transition (1,088 nm) were measured with several 690-nm laser frequencies around the resonance frequency of the |5f 2F5/2, Fm = 1⟩ → |6d 2D5/2, Fm = 2⟩ transition. From bottom to top, the 690-nm laser frequency was increased by 100 MHz at each step. The spectra were vertically shifted by 1.5 × 105 s−1 at each step for clarity. b, The spectral area was determined by fitting (black line) and plotted as a function of the 690-nm laser frequency. The resonance frequency \({\nu }_{{\rm{m}},{\rm{HF}}}^{690}\) was determined to be the one that gives the largest spectral area. The error bars represent the standard deviation of the mean.