Actinium-227

Actinium-227
Actinium-227
Name, symbol	Actinium-227, 227 Ac
Neutron	138
Nuclide properties
Atomic mass	227.0277521 (26) a. eat.
Mass defect	25,850.9 (24) eV
Specific bond energy (nucleon)	7,650.701 (11) keV
Half life	21,772 (3) years
Decay products	227 Th , 223 Fr
Parental isotopes	227 Ra ( β - ); 231 Pa ( α )
Spin and parity of the nucleus	3/2 -
β -	0.0448 (8) M eV
α	5.04219 (14) MeV

Actinium-227 ( eng. Actinium-227 ), the historical name actinium ( lat. Actinium , denoted by Ac ) is the radioactive nuclide of the chemical element actinium with atomic number 89 and mass number 227. It is the most long-lived natural isotope of actinium.

It belongs to the radioactive family of uranium-235 (the so-called actinium series ). It is found in all uranium ores, but its amounts are small due to the low content of the parent substance — ²³⁵ U. With radioactive equilibrium, 1 g of uranium accounts for 2⋅10 ⁻¹⁰ g of ²²⁷ Ac ^[3] .

Content

Education and Decay

Actinium-227 is directly formed as a result of α-decay of the ²³¹ Pa nuclide (half-life is 3.276 (11) ⋅10 ⁴ ^[2] years) and β ^- -decay of the nuclide ²²⁷ Ra (half-life is 42.2 (5) ^[2] min):

\mathrm {^{231}_{91}Pa} \rightarrow \mathrm {^{227}_{89}Ac} +\mathrm {^{4}_{2}He} ,

{\ displaystyle \ mathrm {^ {231} _ {91} Pa} \ rightarrow \ mathrm {^ {227} _ {89} Ac} + \ mathrm {^ {4} _ {2} He},}

\mathrm {^{227}_{88}Ra} \rightarrow \mathrm {^{227}_{89}Ac} +e^{-}+{\bar {\nu }}_{e}.

{\ displaystyle \ mathrm {^ {227} _ {88} Ra} \ rightarrow \ mathrm {^ {227} _ {89} Ac} + e ^ {-} + {\ bar {\ nu}} _ {e} .}

Actinium-227 is mainly (probability 98.62 (36) ^[2] %) undergoes β ^- -decay , resulting in the decay of the nuclide ²²⁷ Th , also known as radioinium (energy released 44.8 (8) ^[1] keV ) :

\mathrm {^{227}_{89}Ac} \rightarrow \mathrm {^{227}_{90}Th} +e^{-}+{\bar {\nu }}_{e}.

{\ displaystyle \ mathrm {^ {227} _ {89} Ac} \ rightarrow \ mathrm {^ {227} _ {90} Th} + e ^ {-} + {\ bar {\ nu}} _ {e} .}

With a probability of 1.38 (36) ^[2] % actinium-227 disintegrates with the emission of alpha particles and the formation of the nuclide France ²²³ Fr (energy released 5042.19 (14) ^[1] keV ):

\mathrm {^{227}_{89}Ac} \rightarrow \mathrm {^{223}_{87}Fr} +\mathrm {^{4}_{2}He} .

{\ displaystyle \ mathrm {^ {227} _ {89} Ac} \ rightarrow \ mathrm {^ {223} _ {87} Fr} + \ mathrm {^ {4} _ {2} He}.}

Getting

The extraction of actinium-227 from natural sources is extremely difficult due to the proximity of the chemical properties of actinium and lanthanum (as well as other rare-earth metals ), so milligram quantities of actinium-227 are artificially prepared by irradiating radium ²²⁶ Ra with neutrons ^[3] ^[4] :

\mathrm {^{226}_{88}Ra} (\mathrm {n} ,{\gamma })\mathrm {^{227}_{88}Ra} {\xrightarrow {{\beta }^{-}}}\mathrm {^{227}_{89}Ac} .

{\ displaystyle \ mathrm {^ {226} _ {88} Ra} (\ mathrm {n}, {\ gamma}) \ mathrm {^ {227} _ {88} Ra} {\ xrightarrow {{\ beta} ^ {-}}} \ mathrm {^ {227} _ {89} Ac}.}

Irradiated radium reprocessing schemes are based on the use of extraction and ion exchange methods ^[3] .

Application

A mixture of ²²⁷ Ac and ⁹ Be is used to make neutron sources (neutrons are formed when the ⁹ Be nuclei are irradiated with alpha particles emitted by actinium-227). Ac-Be sources were obtained with a neutron yield of 10 8–10 ⁹ neutrons / s , the average energy of the neutron spectrum is 4.6 MeV . Compared to Ra-Be sources of Ac-Be sources are more convenient to use, since they are characterized by a lower ratio of gamma radiation to the neutron flux ^[3] ^[4] .
Due to the high specific energy release (14.5 W / g) and the possibility of obtaining significant quantities of thermally stable compounds, ²²⁷ Ac can be used to create long-acting thermoelectric generators (including those suitable for space purposes) ^[3] .

Notes

↑ ¹ ² ³ ⁴ ⁵ ⁶ ⁷ Audi G. , Wapstra AH , Thibault C. The AME2003 atomic mass evaluation (II). Tables, graphs, and references (Eng.) // Nuclear Physics A. - 2003. - Vol. 729 - P. 337-676 . - DOI : 10.1016 / j.nuclphysa.2003.11.003 . - .
² ¹ ² ³ ⁴ ⁵ ⁶ Audi G. , Bersillon O. , Blachot J. , Wapstra AH The Nuclear Physics A. - 2003. - T. 729 . - p . 3-128 . - DOI : 10.1016 / j.nuclphysa.2003.11.001 . - .
↑ ¹ ² ³ ⁴ ⁵ Karalova Z. K., Myasoedov B. F. Aktiniy . - M .: Science, 1982. - 144 p. - (Analytical chemistry of elements). - 1 150 copies
↑ ¹ ² Chemical encyclopedia: 5 tons. / Ed.: Knunyants I.L. (ch. Red.). - M .: Soviet Encyclopedia, 1988. - T. 1. - p. 78. - 623 p. - 100 000 copies

[AME2003-1] ¹ ² ³ ⁴ ⁵ ⁶ ⁷ Audi G. , Wapstra AH , Thibault C. The AME2003 atomic mass evaluation (II). Tables, graphs, and references (Eng.) // Nuclear Physics A. - 2003. - Vol. 729 - P. 337-676 . - DOI : 10.1016 / j.nuclphysa.2003.11.003 . - .

[Nubase2003-2] ² ¹ ² ³ ⁴ ⁵ ⁶ Audi G. , Bersillon O. , Blachot J. , Wapstra AH The Nuclear Physics A. - 2003. - T. 729 . - p . 3-128 . - DOI : 10.1016 / j.nuclphysa.2003.11.001 . - .

[karalova-3] ¹ ² ³ ⁴ ⁵ Karalova Z. K., Myasoedov B. F. Aktiniy . - M .: Science, 1982. - 144 p. - (Analytical chemistry of elements). - 1 150 copies

[ХЭ-4] ¹ ² Chemical encyclopedia: 5 tons. / Ed.: Knunyants I.L. (ch. Red.). - M .: Soviet Encyclopedia, 1988. - T. 1. - p. 78. - 623 p. - 100 000 copies