Velocity spectrometer for particles in the 10-meV to 10-keV range

We have measured the velocity spectrum of a Na beam emerging from a charge exchange source from the thermal up to the 2-keV region. The spectrometer is based on the Doppler-shifted resonance absorption of photons, produced by a tunable single-mode cw dye laser. A sensitivity of less than 100 atoms/cm3 at velocity resolutions of about 70 m/sec in the thermal region and 0.5% at higher energies is achieved. The performance of the spectrometer is discussed. 361