Polonium-209...

Credit: Irvine/NIST

Scientists at the National Institute of Standards and Technology (NIST) have determined* that polonium-209, the longest-lived isotope of this radioactive heavy element, has a half-life about 25 percent longer than the previously determined value, which had been in use for decades.

The new NIST measurements could affect geophysical studies such as the dating of sediment samples from ocean and lake floors. They often employ Po-209 as a tracer. Because sediment cores are used for determining human impact on the environment over the past century, the new measurement could impact these studies as well as other environmental measurements and biological assays.

NIST: Polonium's Most Stable Isotope Gets Revised Half-Life Measurement, Chad Boutin

*R. Collé, R.P. Fitzgerald and L. Laureano-Perez. The half-life of 209Po: revisited. Journal of Physics G: Nuclear and Particle Physics 41 (2014) 105103, doi:10.1088/0954-3899/41/10/105103