Counting ⁸¹Kr atoms for analysis of groundwater

This is the authors' abstract. We don't add key points for this paper.

A new analytical technique with sufficient sensitivity to determine 81 Kr concentrations in groundwater is described. The method utilizes single‐atom counting by laser resonance ionization spectroscopy (RIS) in combination with a small mass spectrometer to achieve the required selectivity and sensitivity. A first demonstration of the technique for groundwater analyses is presented in which about 1000 atoms of 81 Kr were counted after the processing of gas extracted from only a few liters of water. The potential of the new method for groundwater dating in the range 50,000 to 1,000,000 years is discussed.