SUB-DOPPLER SPECTROSCOPY OF Y-89

Sub-Doppler resolution of atomic transitions is obtained by spatially resolved laser induced fluorescence in a diverging atomic beam created by laser ablation. Resonances are spatially separated by relativistic effects experienced between the probing radiation and the moving part icles thus proving that it is a high-quality atomic beam. Fast neutral atomic beams of Y-89 having centroid energies up to 12 eV are interro gated with tuned, single-frequency laser light. Narrow, spatially sepa rated points of light move along the probe axis and are imaged by dete cting only the zero-velocity components of the fluorescence. According ly, the (YD3/2)-D-2 --> (YD3/20)-D-2 transition centered near 16 146 c m(-1) is resolved into its hyperfine components with line widths on th e order of 55 MHz and with an equivalent resolution of +/- 5 MHz (+/- 0.0002 cm(-1)). The upper level hyperfine interaction constant derived from level splitting is + 89 +/- 5 MHz. An equivalent collimation rat io of 9 mrad is estimated for the expanding pulsed atomic beam. We pro pose that laser ablation of selected targets provides a unique source of neutral or ionic ground-state atoms and molecules for spectroscopic studies. Details of these experiments are discussed and analyzed. (C) 1996 American Institute of Physics.