176Lu

176Lu is a naturally occurring radioisotope of lutetium (Lu), with mass number 176 and atomic number 71. In nature, lutetium consists primarily of 175Lu (about 97.4%) and 176Lu (about 2.6%).

176Lu decays by beta minus emission to 176Hf, a stable isotope of hafnium. It has a very long half-life, commonly given as about 37.8 billion years (3.78 × 10^10 yr). The decay constant is roughly 1.84 × 10^-11 yr^-1. Because of its long half-life, 176Lu remains present in natural lutetium and acts as a long-lived chronometer in radiometric dating.

Lu-Hf dating uses the decay of 176Lu to 176Hf to date geological and planetary differentiation events. By measuring the ratio of 176Hf to stable hafnium isotopes and the 176Lu/177Hf ratio, scientists can infer ages of rocks, meteorites, and planetary crust formation.

176Lu is produced naturally and can be produced in reactors or accelerators through neutron capture by 175Lu. In geologic samples, the radiogenic ingrowth of 176Hf is used alongside other isotope systems. The radioisotope is handled with standard radiological precautions; its long half-life means low activity per unit mass, but ingestion or inhalation poses radiation exposure risks.