La139

La-139, or 139La, is the only stable isotope of the chemical element lanthanum (atomic number 57). In nature, nearly all lanthanum is found as 139La, making it the dominant isotope in natural samples. A second isotope, 138La, exists only at trace levels and is radioactive, with a very long half-life on cosmological timescales, so it is present only as a minor component of naturally occurring lanthanum.

Nuclear properties of 139La include a nuclear spin of 7/2 and a quadrupolar nature, which influences how the nucleus behaves in magnetic fields and in solid-state environments. This combination makes 139La useful in certain spectroscopic techniques, particularly nuclear magnetic resonance (NMR) studies of materials.

Occurrence and production: Lanthanum is a rare earth element mined from minerals such as monazite and bastnäsite. Because 139La constitutes the bulk of natural lanthanum, it dominates the isotopic composition encountered in most applications and analyses.

Applications and significance: The high natural abundance and favorable nuclear properties of 139La make it a common probe in solid-state NMR and materials science, where 139La signals help elucidate local coordination, structure, and dynamics in lanthanum-containing compounds. It is also used as a tracer in some geochemical and environmental studies.

See also: Isotopes of lanthanum, Lanthanum (element).