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 Li-7, For our lifetime measurements, we use a dye laser crossed with a fast lithium beam to selectively excite the 2p P-2(1/2,3/2) states from the 2s S-2(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 2s S-2(1/2) --> 2p P-2(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%. (C) 1997 Elsevier Science B.V.