High-Resolution Two-Photon Spectroscopy with Picosecond Light Pulses

Abstract
We have demonstrated the feasibility of Doppler-free two-photon spectroscopy with a train of picosecond standing-wave light pulses from a synchronously pumped mode-locked cw dye laser. The actively controlled mode spectrum provides a means for accurate measurements of large frequency intervals. From a multipulse spectrum of the sodium 3s4d transition we have determined a new value of the 4d fine-structure splitting, 1028±0.4 MHz.