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Isotope of samarium
Samarium-147
(
147
Sm
or
Sm-147
) is an
isotope of samarium
, making up 15% of natural
samarium
. It is an extremely long-lived
radioisotope
, with a
half-life
of 1.06×10
11
years, although this can range from 1.05×10
11
[1]
to 1.17×10
11
[2]
years. It is mainly used in radiometric dating.
[3]
Uses
[
edit
]
Samarium-147 is used in
samarium?neodymium dating
. The method of
isochron dating
is used to find the date at which a rock (or group of rocks) are formed.
[4]
The Sm-Nd isochron plots the ratio of radiogenic
143
Nd to non-radiogenic
144
Nd against the ratio of the parent isotope
147
Sm to the non-radiogenic isotope
144
Nd.
144
Nd 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:
where:
- t
is the age of the sample,
- λ is the decay constant of
147
Sm,
- (
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
chondrites
, and then again the time of formation can be calculated (see
Samarium?neodymium dating#The CHUR model
).
[4]
[5]
See also
[
edit
]
References
[
edit
]
- ^
Wright, P. M.; Steinberg, E. P.; Glendenin, L. E. (1961-07-01).
"Half-Life of Samarium-147"
.
Physical Review
.
123
(1): 205?208.
Bibcode
:
1961PhRv..123..205W
.
doi
:
10.1103/PhysRev.123.205
.
- ^
Kinoshita, Norikazu; Yokoyama, Akihiko; Nakanishi, Takashi (2003).
"Half-Life of Samarium-147"
.
Journal of Nuclear and Radiochemical Sciences
.
4
(1): 5?7.
doi
:
10.14494/jnrs2000.4.5
.
S2CID
120606011
.
- ^
Currie, Lloyd A., ed. (1982-01-29).
Nuclear and Chemical Dating Techniques: Interpreting the Environmental Record
. ACS Symposium Series. Vol. 176. WASHINGTON, D. C.: AMERICAN CHEMICAL SOCIETY.
doi
:
10.1021/bk-1982-0176.ch001
.
ISBN
978-0-8412-0669-4
.
- ^
a
b
Depaolo, D. J.; Wasserburg, G. J. (1976).
"Nd isotopic variations and petrogenetic models"
(PDF)
.
Geophysical Research Letters
.
3
(5): 249.
Bibcode
:
1976GeoRL...3..249D
.
doi
:
10.1029/GL003i005p00249
.
- ^
McCulloch, M. T.; Wasserburg, G. J. (1978).
"Sm-Nd and Rb-Sr Chronology of Continental Crust Formation"
.
Science
.
200
(4345): 1003?11.
Bibcode
:
1978Sci...200.1003M
.
doi
:
10.1126/science.200.4345.1003
.
PMID
17740673
.
S2CID
40675318
.