PRECISION LIFETIME MEASUREMENTS ON NAI 3P-P-2(1 2) AND 3P-P-2(3/2) BYBEAM-GAS-LASER SPECTROSCOPY/

The lifetimes of the fine-structure levels 3p P-2(1/2) and 3p P-2(3/2) in neutral sodium were determined at improved precision (+/-0.13%, 1 sigma) by means of the beam gas-laser spectroscopy method. The resulti ng lifetimes of 16.299(21) and 16.254(22) ns, respectively, are in exc ellent agreement with the results of the most refined theoretical calc ulations. The long-standing discrepancy between ab initio line strengt h calculations and the measurements of Gaupp et al. [Phys. Rev. A 26, 3351 (1982)] for the NaI 3s-3p transition appears to be resolved now. In addition, the hyperfine constants of the 3p P-2(3/2) level were det ermined.