Rubidium-87 (⁸⁷Rb)

The ⁸⁷Rb-⁸⁷Sr decay system is one of the important methods of radioactive dating and is suitable for dating ancient rocks (such as granite and meteorites). Its decay constant λ=1.42×10⁻¹¹ yr⁻¹. By measuring the ratio of ⁸⁷Sr/⁸⁶Sr and ⁸⁷Rb/⁸⁶Sr, combined with the isochron method, the geological age can be calculated, and the time span can reach billions of years. This technology plays a key role in studying the evolution of the earth's crust, the formation history of the moon and meteorites.

⁸⁷Rb is one of the core elements of cold atomic physics, and its D₂ line (780.24 nm, 5²S₁/₂→5²P₃/₂ transition) is a common transition in laser cooling and Bose-Einstein condensation (BEC) experiments. The ground state hyperfine structure (F=1,2) of ⁸⁷Rb can be used for precision measurements, such as atomic clocks (rubidium atomic clock frequency standard ~6.834682 GHz) and quantum simulation experiments. In addition, the Feshbach resonance characteristics of ⁸⁷Rb make it attract much attention in ultracold molecular preparation and quantum many-body research.

⁸⁷Rb can be generated by neutron activation of ⁸⁶Rb (n,γ), and its short-lived isotope ⁸²Rb (T₁/₂=1.27 min) is a myocardial perfusion imaging agent for positron emission tomography (PET) and is used for the diagnosis of coronary heart disease. Although ⁸⁷Rb itself is not directly used in medicine, its decay chain products (such as ⁸⁷Sr) have certain reference value in bone metabolism research.

⁸⁷Rb has weak radioactivity (specific activity ~3.2×10⁻⁴ Bq/g), and usually does not require special protection, but long-term exposure to high-concentration ⁸⁷Rb compounds (such as RbCl) still needs to be avoided from inhalation or ingestion. In the laboratory, ⁸⁷Rb is often stored in the form of chloride or carbonate and needs to be sealed to prevent moisture.