Samarium-147 (¹⁴⁷Sm or Sm-147) is an isotope of samarium, making up 15% of natural

samarium Samarium is a chemical element; it has symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of s ...

. It is an extremely long-lived

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

, with a

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of years, although measurements have ranged from to years. It is mainly used in radiometric dating.

Uses

Samarium-147 is used in

samarium–neodymium dating Samarium–neodymium dating is a radiometric dating method useful for determining the ages of rocks and meteorites, based on the alpha decay of the long-lived samarium isotope () to the stable radiogenic neodymium isotope (). Neodymium isotope ra ...

. The method of

isochron dating Isochron dating is a common technique of radiometric dating and is applied to date certain events, such as crystallization, metamorphism, shock events, and differentiation of precursor melts, in the history of rocks. Isochron dating can be furth ...

is used to find the date at which a rock (or group of rocks) are formed. The Sm-Nd isochron plots the ratio of radiogenic ¹⁴³Nd to non-radiogenic ¹⁴⁴Nd against the ratio of the parent isotope ¹⁴⁷Sm to the non-radiogenic isotope ¹⁴⁴Nd. ¹⁴⁴Nd is used to normalize the radiogenic isotope in the isochron because it is a slightly radioactive and relatively abundant neodymium isotope. The Sm-Nd isochron is defined by the following equation: :

\left(\frac\right)_ = \left(\frac\right)_ + \left(\frac\right) \cdot (e^-1),

where: : ''t'' is the age of the sample, : λ is the decay constant of ¹⁴⁷Sm, : (''e''^λ''t''−1) is the slope of the isochron which defines the age of the system. Alternatively, one can assume that the material formed from mantle material which was following the same path of evolution of these ratios as

chondrite A chondrite is a stony (non-metallic) meteorite that has not been modified by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar Syste ...

s, and then again the time of formation can be calculated (see Samarium–neodymium dating#The CHUR model).

References

{{Isotope sequence , element=samarium , lighter= samarium-146 , heavier= samarium-148 , before=

gadolinium Gadolinium is a chemical element; it has Symbol (chemistry), symbol Gd and atomic number 64. It is a silvery-white metal when oxidation is removed. Gadolinium is a malleable and ductile rare-earth element. It reacts with atmospheric oxygen or moi ...

-151 ( α)

promethium Promethium is a chemical element; it has Symbol (chemistry), symbol Pm and atomic number 61. All of its isotopes are Radioactive decay, radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in the Earth's crust a ...

-147 ( β⁻) , after= neodymium-143 (α) Samarium-147 Radionuclides used in radiometric dating

Uses

See also

References