krypton-81
Quick Summary
Krypton-81 (81Kr) is a radioactive isotope of the noble gas krypton. Krypton itself is a rare, colorless, and odorless gas found in Earth's atmosphere. Natural krypton is a mixture of six stable isotopes, but krypton also has 25 radioactive isotopes, many of which are produced by nuclear reactions.1
Krypton-81 has a long half-life of approximately 229,000 years. Due to this long half-life, it cannot be detected by counting its radioactive decay. Instead, advanced techniques like resonance-ionization mass spectrometry (RIMS) are used to detect and count individual krypton-81 atoms. This capability allows scientists to use 81Kr for dating purposes, such as determining the age of polar ice and groundwater, providing insights into past climates and hydrological histories.12
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