HIGH-RESOLUTION SPECTROSCOPY AND FREQUENCY-MEASUREMENT OF THE MIDINFRARED 5D2D3 2-5D2D5/2 TRANSITION OF A SINGLE LASER-COOLED BARIUM ION/

The narrow 12.5 mum, 5d2D3/2-5d2D5/2 fine-structure transition in a la ser-cooled, single Ba+ atom has been probed with a tunable sideband fr om a frequency-stable (NH3)-N-15 laser operating on the sP(8, 6) trans ition. Single-ion Doppler-free resonances with negligible time dilatio n shift are observed without any detected motional sidebands for each Zeeman component. Linewidths of 11 kHz are observed for the components , which are currently limited by the probe laser frequency excursions. A measurement of the D-D transition center frequency relative to the sP(8, 6) saturated absorption dip has been performed. A preliminary me asurement of the sP (8, 6) line center frequency gives the line center for the Ba-138+ isotope transition as 24 012 048.5 +/- 0.2 MHz.