Enhancement of the $^{81}\mathrm{Kr}$ and $^{85}\mathrm{Kr}$ count rates by optical pumping

TL;DR

This paper demonstrates a 60% increase in count rates of rare krypton isotopes using optical pumping to enhance metastable atom production, improving dating techniques for ocean water and ice cores.

Contribution

It introduces an optimized optical pumping method to significantly boost isotope detection rates in atom trap analysis, with calculated isotope shifts and hyperfine splittings.

Findings

Up to 60% increase in isotope count rates.

Identification of the optimal 819 nm transition for pumping.

Reduced sample size requirements for isotope dating.

Abstract

We report an increase of up to 60% on the count rates of the rare $^{81}\mathrm{Kr}$ and $^{85}\mathrm{Kr}$ 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 $^{81}\mathrm{Kr}$ and $^{85}\mathrm{Kr}$, and verify the results with count rate measurements. The demonstrated count-rate increase enables a corresponding decrease in the required sample sizes for $^{81}\mathrm{Kr}$ and $^{85}\mathrm{Kr}$ dating, a significant improvement for applications such as dating of ocean water and deep ice cores.