84Sr

84Sr is a stable isotope of the element strontium (Sr). It has mass number 84 and atomic number 38, with a natural atomic mass around 83.9 u. In natural strontium, 84Sr accounts for about 0.56% of atoms.

Nuclear properties of 84Sr include that it is an even-even nucleus with zero nuclear spin in its ground state (I = 0) and it does not undergo radioactive decay. As a stable isotope, it remains unchanged over geological timescales.

The four stable isotopes of strontium are 84Sr, 86Sr, 87Sr, and 88Sr. Their terrestrial abundances are approximately 0.56%, 9.86%, 7.0%, and 82.58%, respectively. This isotopic composition is used in geochemistry and cosmochemistry to study planetary processes and the provenance of materials.

Natural occurrence and formation: 84Sr is produced in stars through neutron capture processes, primarily the slow neutron capture (s-process). On Earth it occurs together with other stable Sr isotopes in minerals such as celestite (SrSO4) and strontianite (SrCO3), contributing to the overall strontium isotope composition of rocks and minerals.

Applications: 84Sr serves as a tracer and reference in isotope ratio measurements. In isotope dilution mass spectrometry, a spike enriched in 84Sr is used to quantify strontium and to determine accurate 87Sr/86Sr ratios. The 87Sr/86Sr ratio, produced through decay of 87Rb, is widely used for age-dating and provenance studies, while 84Sr helps calibrate instruments and correct for mass fractionation and instrumental biases.