The measurement of Doppler-shifted radiation using a cesium resonance fluorescence monochromator (RFM) is described. The RFM is based on two-step excitation (62S1/2→62P03/2 →62D5/2) followed by wavelength-shifted fluorescence and detection of resonance photons with sub-Doppler spectral resolution (200 MHz). We demonstrate the resolution of velocity differences by comparing excitation profiles of a reference beam and Doppler-shifted scatter. A rotating disc of variable speed was used to generate the Doppler-shifted photons. Velocity changes on the order of 25 m/s were resolved, and the upper velocity limit (1500 m/s) is limited only by the extent of the frequency scan of the first excitation laser.
- Cesium spectroscopy
- Doppler velocimetry
- Resonance fluorescence monochromator