Enhancement of the 81Kr and 85Kr count rates by optical pumping
Abstract
We report an increase of up to 60% on the count rates of the rare 81Kr and 85Kr isotopes in the Atom Trap Trace Analysis method by enhancing the production of metastable atoms in the discharge source. Additional atoms in the metastable 1s5 level (Paschen notation) are obtained via optically pumping the 1s4-2p6 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 1s4-2p6 transition in 81Kr and 85Kr, and verify the results with count rate measurements. The demonstrated count-rate increase enables a corresponding decrease in the required sample sizes for 81Kr and 85Kr dating, a significant improvement for applications such as dating of ocean water and deep ice cores.