Enhancement Of The Kr-81 And Kr-85 Count Rates By Optical Pumping

We report an increase of up to 60% on the count rates of the rare Kr-81 and Kr-85 isotopes in the Atom Trap Trace Analysis method by enhancing the production of metastable atoms in the discharge source. Additional atoms in the metastable 1s(5) level (Paschen notation) are obtained via optically pumping the 1s(4)-2p(6) transition at 819 nm. By solving the master equation for the system, we identify this transition to be the most suitable one and can describe the measured increase in metastable population as a function of the 819-nm laser power. We calculate the previously unknown isotope shifts and hyperfine splittings of the 1s(4)-2p(6) transition in Kr-81 and Kr-85, and verify the results with count rate measurements. The demonstrated count-rate increase enables a corresponding decrease in the required sample sizes for Kr-81 and Kr-85 dating, a significant improvement for applications such as dating of ocean water and deep ice cores.