Extended Data Fig. 2: Energy level diagram of argon relevant to the ATTA measurement.
From: Detection of atmospheric 42Ar at the 10−21 level by atom counting
The red arrow denotes the 811.8 nm transition used for laser cooling, trapping, and detection of metastable argon atoms. The orange arrow indicates the quench transition, which de‑excites metastable atoms to the ground state.
