Laser Doppler velocimetry of a fast beam with a temperature stabilized solid etalon

We report a precise velocity measurement of a fast atomic lithium beam using a calibrated solid etalon. This technique is important to our program of precision atomic lifetime measurements which includes the 2p states of neutral 7Li. For our lifetime measurements, we use a dye laser crossed with a fast lithium beam to selectively excite the 2 p 2 P 1 2 , 3 2 states from the 2 s 2 S 1 2 ground state, and photon-counting detectors record the decay in flight of the fluorescence. With the laser aligned antiparallel to the atomic beam direction, we use a calibrated solid etalon to measure the Doppler shift of the 2 s 2 S 1 2 → 2 p 2 P 3 2 resonance to be 1742.67(53) GHz. The resulting velocity converts our position scale to a time scale with a precision of 0.03%.