Evidence of the double β decay of zirconium-96 measured in 1.8×109 year-old zircons

Molybdenum extracted from geologically old zircons shows evidence for enhanced levels of ⁹⁶Mo, resulting from the double β decay of ⁹⁶Zr. Evidence of nuclear fission in ⁹⁵Mo, ⁹⁷Mo, ⁹⁸Mo, and ¹⁰⁰Mo extracted from the old zircons accompanies the double β decay of ⁹⁶Zr, and is comparable in magnitude to the excess ⁹⁶Mo. Zircons are excellent minerals for an experiment of this nature, since zircon U-Pb geochronology demonstrates that zircons have remained as closed isotopic systems over eons of time. The experimental data indicate that the half-life of ⁹⁶Zr double β decay is (9.4+/-3.2)×10¹⁸ yr and is in good agreement with the theoretically predicted half-life for the ⁹⁶Zr decay to ⁹⁶Mo occurring as a two neutrino decay.