PHOTON-BURST METHOD IN HIGH-RESOLUTION LASER SPECTROSCOPY

The sensitivity of high-resolution fluorescence spectroscopy has been enhanced by the detection of bursts of photons from single atoms crossing a laser beam. A tunable cw laser beam intersected a well-collimated atomic beam at right angles, and the fluorescent light was detected by an ellipsoidal collector and a photomultiplier. The passage of an atom through the beam was identified with a burst of detected photon pulses, which could be differentiated easily from the random background. For increasing burst multiplicity the spectra show improved background suppression and also significant peak narrowing. High-resolution spectra were obtained with as few as 10 atoms/sec crossing the laser beam. Statistical predictions for the case of transit-time limited signals are calculated and compared with results obtained for the Na 5890- and Ba 5535- transitions. © 1979 The American Physical Society.