Measurement of the isotope shift in the 350 nm and 413 nm transitions of atomic barium

We measured the isotope shift of neutral barium atoms in the 6s² ¹S₀ → 5d6p ¹P₁ transition at 350 nm and the 6s² ¹S₀ → 5d6p ³D₁ transition at 413 nm. Although the 413 nm transition is commonly used for photoionization to load barium ions in Paul traps, the 350 nm transition may be more efficient due to its transition rate being an order of magnitude larger. Additionally, we determine the hyperfine constants of the ¹P₁ and ³D₁ states. We generate the 350 nm light from a 1050 nm source using two cascaded PPLN waveguides: the first stage performs second-harmonic generation at 525 nm, followed by sum-frequency generation. This 350 nm laser is also compatible with the repump laser required for cooling lutetium ions, which will be used in a future experiment.