A novel and sensitive technique for high resolution spectroscopy

The transit time of an atom at thermal velocity through a laser beam of ca. 1 mm diameter corresponds to many lifetimes of the excited state for typical allowed atomic transitions. Thus, a single atom may undergo many resonant scatterings, giving rise to a burst of photons. The direction of such bursts of photons corresponding to the passage of single atoms of Ba and Na through the beam of a cw dye laser is reported. The resulting improvement in sensitivity will make resonance fluorescence experiments feasible using atomic beams as weak as a few tens of atoms per second. The ultimate goal is to measure hyperfine structure and isotopic shifts of radioactive species which can be produced only in minute quantities. (Auth.)