High precision spectroscopy on the 2s2p ¹P₁ - 2s3s ¹S₀ transition in neutral beryllium-9

We present progress on measuring the absolute transition frequency of the 2s2p ¹P₁ - 2s3s ¹S₀ transition in neutral beryllium-9 near 825 nm. We preform saturated absorption spectroscopy using a home-built hollow cathode lamp that has a hollow cylinder of beryllium as the cathode. The DC discharge is sustained with argon gas and the laser frequency is measured using a frequency comb.