rubidium87

Rubidium-87 (87Rb) is one of the naturally occurring isotopes of rubidium. It accounts for about 27.8% of natural rubidium, with the remainder predominantly consisting of rubidium-85. 87Rb is a long-lived radioactive isotope with a half-life of about 4.88 × 10^10 years, decaying via beta emission to 87Sr. The nuclear spin is I = 3/2, and its ground-state hyperfine transition occurs at a frequency of 6.834 GHz, a property exploited in timekeeping.

As a light alkali metal, rubidium is soft and highly reactive, and 87Rb shares these chemical traits. It occurs in certain minerals such as lepidolite and pollucite and is extracted through standard ore-processing methods. In nature, rubidium is present in the Earth's crust at low concentrations, with 87Rb constituting roughly a quarter of the rubidium present.

In practical use, 87Rb has become important in science and technology. Rubidium atomic clocks rely on the 87Rb hyperfine transition to define time standards and are used in telecommunications, navigation, and various scientific instruments. The element is also widely employed in atomic physics research, especially in laser cooling and trapping experiments. 87Rb is a common choice for magneto-optical traps and was instrumental in achieving one of the first Bose-Einstein condensates in 1995, demonstrating its significance for ultracold atomic physics.

Historically, rubidium was named for its red spectral lines, discovered in 1861 by Bunsen and Kirchhoff. The isotope 87Rb’s long half-life and well-characterized transitions have cemented its role in both metrology and fundamental physics.