Y-90

Rubidium-87 (Rb-87) is a naturally occurring radioactive isotope of rubidium with an extremely long half-life of about 49.7 billion years. It decays by beta-minus emission directly to stable strontium-87. The maximum beta energy is approximately 282 keV, and the decay does not produce characteristic gamma rays.

Rb-87 is best known for its use in rubidium-strontium (Rb-Sr) radiometric dating. By measuring the relative amounts of Rb-87 and its decay product Sr-87, scientists can determine the ages of ancient rocks and minerals and study geological processes over billions of years.

Rb-87 occurs naturally and makes up about 27.8% of natural rubidium. Because rubidium can substitute for potassium in minerals, Rb-87 is widespread in many rocks and minerals, particularly potassium-rich minerals such as biotite, muscovite, and potassium feldspar. Elevated concentrations can also occur in pegmatites.

Rb-87

Rubidium-87
Natural β radiation

Half-life: 49.7 billion years Main emission lines: -