2-PHOTON 2-COLOR DIODE-LASER SPECTROSCOPY OF THE RB 5D(5 2) STATE/

We report on spectroscopic measurements of the Rb 5D(5/2) state perfor med using two-photon excitation with a resonant intermediate state. Wi th the two beams (5S(1/2) --> 5P(3/2) at 780 nm and 5P(3/2) --> 5D(5/2 ) at 776 nm) counterpropagating, the spectra are Doppler-free and the signals are very robust, even in a room temperature vapor. This is due to the near match of the transition wavelengths. The 5D(5/2) hyperfin e constants have been measured and compared to previous determinations . We have also performed the excitation in a sample of laser-cooled at oms and compare these results to those obtained at room temperature. T he fact that the 5P(3/2) --> 5D(5/2) transition is narrow, robust, dio de-laser accessible, and relatively immune to AC-Stark shifts, may mak e it a promising candidate for a frequency reference at 776 nm.