Isotopes of actinium

Actinium (₈₉Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 34 known isotopes, from ²⁰³Ac to ²³⁶Ac, and 7 isomers. Three isotopes are found in nature, ²²⁵Ac, ²²⁷Ac and ²²⁸Ac, as intermediate decay products of, respectively, ²³⁷Np, ²³⁵U, and ²³²Th. ²²⁸Ac and ²²⁵Ac are extremely rare, so almost all natural actinium is ²²⁷Ac.

The most stable isotopes are ²²⁷Ac with a half-life of 21.772 years, ²²⁵Ac with a half-life of 10.0 days, and ²²⁶Ac with a half-life of 29.37 hours. All other isotopes have half-lives under 10 hours, and most under a minute. The shortest-lived known isotope is ²¹⁷Ac with a half-life of 69 ns.

Purified ²²⁷Ac comes into equilibrium with its decay products (²²⁷Th and ²²³Fr) after 185 days.

{{cite book

| year = 2005

| chapter = Chemical Elements

| title = Van Nostrand's Encyclopedia of Chemistry

| editor = G. D. Considine

| page = 332

| publisher = Wiley-Interscience

| isbn = 978-0-471-61525-5

}}

List of isotopes

{{Anchor|Actinium-206m|Actinium-215m1|Actinium-215m2|Actinium-216m1|Actinium-216m2|Actinium-218m1|Actinium-218m2|Actinium-228m|Actinium-234m1|Actinium-234m2|Actinium-237}}

{{Isotopes table

|symbol=Ac

|refs=

|notes=m, histname, unc(), mass#, exen#, spin(), spin#, daughter-nst, CD, EC, IT

}}

|-id=Actinium-203

| ²⁰³Ac{{cite journal |last1=Wang |first1=J. G. |last2=Gan |first2=Z. G. |last3=Zhang |first3=Z. Y. |last4=Huang |first4=M. H. |last5=Ma |first5=L. |last6=Zhang |first6=M. M. |last7=Yang |first7=H. B. |last8=Yang |first8=C. L. |last9=Qiang |first9=Y. H. |last10=Huang |first10=X. Y. |last11=Zhao |first11=Z. |last12=Xu |first12=S. Y. |last13=Li |first13=Z. C. |last14=Chen |first14=L. X. |last15=Sun |first15=L. C. |last16=Zhou |first16=H. |last17=Zhang |first17=X. |last18=Wu |first18=X. L. |last19=Tian |first19=Y. L. |last20=Wang |first20=Y. S. |last21=Wang |first21=J. Y. |last22=Huang |first22=W. X. |last23=Liu |first23=M. L. |last24=Lu |first24=Z. W. |last25=He |first25=Y. |last26=Ren |first26=Z. Z. |last27=Zhou |first27=S. G. |last28=Zhou |first28=X. H. |last29=Xu |first29=H. S. |last30=Utyonkov |first30=V. K. |last31=Voinov |first31=A. A. |last32=Tsyganov |first32=Yu. S. |last33=Polyakov |first33=A. N. |display-authors=3 |title=α-decay properties of new neutron-deficient isotope 203Ac |journal=Physics Letters B |date=1 March 2024 |volume=850 |pages=138503 |doi=10.1016/j.physletb.2024.138503 |issn=0370-2693|doi-access=free }}

| style="text-align:right" | 89

| style="text-align:right" | 114

| {{Val|56|269|26|u=μs}}

| α

| ¹⁹⁹Fr

| (1/2+)

|-id=Actinium-204

|²⁰⁴Ac{{cite journal |last1=Huang |first1=M. H. |last2=Gan |first2=Z. G. |last3=Zhang |first3=Z. Y. |last4=Ma |first4=L. |last5=Wang |first5=J. G. |last6=Zhang |first6=M. M. |last7=Yang |first7=H. B. |last8=Yang |first8=C. L. |last9=Huang |first9=X. Y. |last10=Zhao |first10=Z. |last11=Xu |first11=S. Y. |last12=Chen |first12=L. X. |last13=Wen |first13=X. J. |last14=Niu |first14=Y. F. |last15=Yuan |first15=C. X. |last16=Tian |first16=Y. L. |last17=Wang |first17=Y. S. |last18=Wang |first18=J. Y. |last19=Liu |first19=M. L. |last20=Qiang |first20=Y. H. |last21=Yang |first21=W. Q. |last22=Zhang |first22=H. B. |last23=Lu |first23=Z. W. |last24=Guo |first24=S. |last25=Huang |first25=W. X. |last26=He |first26=Y. |last27=Ren |first27=Z. Z. |last28=Zhou |first28=S. G. |last29=Zhou |first29=X. H. |last30=Xu |first30=H. S. |last31=Utyonkov |first31=V. K. |last32=Voinov |first32=A. A. |last33=Tsyganov |first33=Yu. S. |last34=Polyakov |first34=A. N. |display-authors=3 |title=α decay of the new isotope ²⁰⁴Ac |journal=Physics Letters B |date=10 November 2022 |volume=834 |pages=137484 |doi=10.1016/j.physletb.2022.137484 |bibcode=2022PhLB..83437484H |s2cid=252730841 |language=en |issn=0370-2693|doi-access=free }}

| style="text-align:right" | 89

| style="text-align:right" | 115

| {{Val|7.4|2.2|1.4|u=ms}}

| α

| ²⁰⁰Fr

|-id=Actinium-205

|²⁰⁵Ac{{Cite journal |last1 = Zhang |first1 = Z. Y. |last2 = Gan |first2 = Z. G. |last3=Ma |first3=L. |last4=Yu |first4=L. |last5=Yang |first5=H. B. |last6=Huang |first6=T. H. |last7=Li |first7=G. S. |last8=Tian |first8=Y. L. |last9=Wang |first9=Y. S. |last10=Xu |first10=X. X. |last11=Huang |first11=M. H. |last12=Luo |first12=C. |last13=Ren |first13=Z. Z. |last14=Zhou |first14=S.G. |last15=Zhou |first15=X. H. |last16=Xu |first16=H. S. |last17=Xiao |first17=G. Q. |display-authors=3 | title =α decay of the new neutron-deficient isotope ²⁰⁵Ac| journal = Physical Review C | volume = 89 | issue = 1 | pages = 014308 |date=January 2014 | url = http://journals.aps.org/prc/abstract/10.1103/PhysRevC.89.014308 | doi =10.1103/PhysRevC.89.014308|bibcode=2014PhRvC..89a4308Z }}

| style="text-align:right" | 89

| style="text-align:right" | 116

| {{val|7.7|2.7|1.6|u=ms}}

| α

| ²⁰¹Fr

| 9/2−?

|-id=Actinium-206

| ²⁰⁶Ac

| style="text-align:right" | 89

| style="text-align:right" | 117

| 206.01450(8)

| 25(7) ms

| α

| ²⁰²Fr

| (3+)

|-id=Actinium-206m1

| style="text-indent:1em" | ^206m1Ac

| colspan="3" style="text-indent:2em" | 80(50) keV

| 15(6) ms

| α

| ²⁰²Fr

|-id=Actinium-206m2

| style="text-indent:1em" | ^206m2Ac

| colspan="3" style="text-indent:2em" | 290(110)# keV

| 41(16) ms

| α

| ^202mFr

| (10−)

|-id=Actinium-207

| ²⁰⁷Ac

| style="text-align:right" | 89

| style="text-align:right" | 118

| 207.01195(6)

| 31(8) ms
[27(+11−6) ms]

| α

| ²⁰³Fr

| 9/2−#

|-id=Actinium-208

| rowspan=2|²⁰⁸Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 119

| rowspan=2|208.01155(6)

| rowspan=2|97(16) ms
[95(+24−16) ms]

| α (99%)

| ²⁰⁴Fr

| rowspan=2|(3+)

| rowspan=2|

| β⁺ (1%)

| ²⁰⁸Ra

|-id=Actinium-208m

| rowspan=3 style="text-indent:1em" | ^208mAc

| rowspan=3|

| rowspan=3 colspan="3" style="text-indent:2em" | 506(26) keV

| rowspan=3|28(7) ms
[25(+9−5) ms]

| α (89%)

| ²⁰⁴Fr

| rowspan=3|(10−)

| rowspan=3|

| IT (10%)

| ²⁰⁸Ac

| β⁺ (1%)

| ²⁰⁸Ra

|-id=Actinium-209

| rowspan=2|²⁰⁹Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 120

| rowspan=2|209.00949(5)

| rowspan=2|92(11) ms

| α (99%)

| ²⁰⁵Fr

| rowspan=2|(9/2−)

| rowspan=2|

| β⁺ (1%)

| ²⁰⁹Ra

|-id=Actinium-210

| rowspan=2|²¹⁰Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 121

| rowspan=2|210.00944(6)

| rowspan=2|350(40) ms

| α (96%)

| ²⁰⁶Fr

| rowspan=2|7+#

| rowspan=2|

| β⁺ (4%)

| ²¹⁰Ra

|-id=Actinium-211

| rowspan=2|²¹¹Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 122

| rowspan=2|211.00773(8)

| rowspan=2|213(25) ms

| α (99.8%)

| ²⁰⁷Fr

| rowspan=2|9/2−#

| rowspan=2|

| β⁺ (.2%)

| ²¹¹Ra

|-id=Actinium-212

| rowspan=2|²¹²Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 123

| rowspan=2|212.00781(7)

| rowspan=2|920(50) ms

| α (97%)

| ²⁰⁸Fr

| rowspan=2|6+#

| rowspan=2|

| β⁺ (3%)

| ²¹²Ra

|-id=Actinium-213

| rowspan=2|²¹³Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 124

| rowspan=2|213.00661(6)

| rowspan=2|731(17) ms

| α

| ²⁰⁹Fr

| rowspan=2|(9/2−)#

| rowspan=2|

| β⁺ (rare)

| ²¹³Ra

|-id=Actinium-214

| rowspan=2|²¹⁴Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 125

| rowspan=2|214.006902(24)

| rowspan=2|8.2(2) s

| α (89%)

| ²¹⁰Fr

| rowspan=2|(5+)#

| rowspan=2|

| β⁺ (11%)

| ²¹⁴Ra

|-id=Actinium-215

| rowspan=2|²¹⁵Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 126

| rowspan=2|215.006454(23)

| rowspan=2|0.17(1) s

| α (99.91%)

| ²¹¹Fr

| rowspan=2|9/2−

| rowspan=2|

| β⁺ (.09%)

| ²¹⁵Ra

|-id=Actinium-216

| ²¹⁶Ac

| style="text-align:right" | 89

| style="text-align:right" | 127

| 216.008720(29)

| 440(16) μs

| α

| ²¹²Fr

| (1−)

|-id=Actinium-216m1

| style="text-indent:1em" | ^216m1Ac

| colspan="3" style="text-indent:2em" | 38(5) keV

| 441(7) μs

| α

| ²¹²Fr

| (9−)

|-id=Actinium-216m2

| style="text-indent:1em" | ^216m2Ac

| colspan="3" style="text-indent:2em" | 422#(100#) keV

| ~300 ns

| IT

| ²¹⁶Ac

|-id=Actinium-217

| ²¹⁷Ac

| style="text-align:right" | 89

| style="text-align:right" | 128

| 217.009347(14)

| 69(4) ns

| α

| ²¹³Fr

| 9/2−

|-id=Actinium-217m

| style="text-indent:1em" | ^217mAc

| colspan="3" style="text-indent:2em" | 2012(20) keV

| 740(40) ns

| (29/2)+

|-id=Actinium-218

| ²¹⁸Ac

| style="text-align:right" | 89

| style="text-align:right" | 129

| 218.01164(5)

| 1.08(9) μs

| α

| ²¹⁴Fr

| (1−)#

|-id=Actinium-218m

| style="text-indent:1em" | ^218mAc

| colspan="3" style="text-indent:2em" | 607(86)# keV

| 103(11) ns

| IT

| ²¹⁸Ac

| (11+)

|-id=Actinium-219

| ²¹⁹Ac

| style="text-align:right" | 89

| style="text-align:right" | 130

| 219.01242(5)

| 11.8(15) μs

| α

| ²¹⁵Fr

| 9/2−

|-id=Actinium-220

| ²²⁰Ac

| style="text-align:right" | 89

| style="text-align:right" | 131

| 220.014763(16)

| 26.36(19) ms

| α

| ²¹⁶Fr

| (3−)

|-id=Actinium-221

| ²²¹Ac

| style="text-align:right" | 89

| style="text-align:right" | 132

| 221.01559(5)

| 52(2) ms

| α

| ²¹⁷Fr

| 9/2−#

|-id=Actinium-222

| rowspan=2|²²²Ac

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 133

| rowspan=2|222.017844(6)

| rowspan=2|5.0(5) s

| α (99(1)%)

| ²¹⁸Fr

| rowspan=2|1−

| rowspan=2|

| β⁺ (1(1)%){{r|g=n|r=This decay mode has been observed, but only an upper limit of branching ratio is experimentally known{{NUBASE2020|ref}}}}

| ²²²Ra

|-id=Actinium-222m

| rowspan=3 style="text-indent:1em" | ^222mAc

| rowspan=3|

| rowspan=3 colspan="3" style="text-indent:2em" | 78(21) keV

| rowspan=3|1.05(5) min

| α (98.6%)

| ²¹⁸Fr

| rowspan=3|5+#

| rowspan=3|

| β⁺ (1.4%)

| ²²²Ra

| IT?

| ²²²Ac

|-id=Actinium-223

| rowspan=3|²²³Ac

| rowspan=3|

| rowspan=3 style="text-align:right" | 89

| rowspan=3 style="text-align:right" | 134

| rowspan=3|223.019137(8)

| rowspan=3|2.10(5) min

| α (99%)

| ²¹⁹Fr

| rowspan=3|(5/2−)

| rowspan=3|

| EC (1%)

| ²²³Ra

| CD (3.2×10⁻⁹%)

| ²⁰⁹Bi
¹⁴C

|-id=Actinium-224

| rowspan=3|²²⁴Ac

| rowspan=3|

| rowspan=3 style="text-align:right" | 89

| rowspan=3 style="text-align:right" | 135

| rowspan=3|224.021723(4)

| rowspan=3|2.78(17) h

| β⁺ (90.9%)

| ²²⁴Ra

| rowspan=3|0−

| rowspan=3|

| α (9.1%)

| ²²⁰Fr

| β⁻ (1.6%)

| ²²⁴Th

| rowspan=2|²²⁵AcHas medical uses

| rowspan=2|

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 136

| rowspan=2|225.023230(5)

| rowspan=2|10.0(1) d

| α

| ²²¹Fr

| rowspan=2|(3/2−)

| rowspan=2|TraceIntermediate decay product of ²³⁷Np

| CD (6×10⁻¹⁰%)

| ²¹¹Bi
¹⁴C

| rowspan=3|²²⁶Ac

| rowspan=3|

| rowspan=3 style="text-align:right" | 89

| rowspan=3 style="text-align:right" | 137

| rowspan=3|226.026098(4)

| rowspan=3|29.37(12) h

| β⁻ (83%)

| ²²⁶Th

| rowspan=3|(1)(−#)

| rowspan=3|

| EC (17%)

| ²²⁶Ra

| α (.006%)

| ²²²Fr

| rowspan=2|²²⁷Ac

| rowspan=2|ActiniumSource of element's name

| rowspan=2 style="text-align:right" | 89

| rowspan=2 style="text-align:right" | 138

| rowspan=2|227.0277521(26)

| rowspan=2|21.772(3) y

| β⁻ (98.62%)

| ²²⁷Th

| rowspan=2|3/2−

| rowspan=2|TraceIntermediate decay product of ²³⁵U

| α (1.38%)

| ²²³Fr

|-id=Actinium-228

| ²²⁸Ac

| Mesothorium 2

| style="text-align:right" | 89

| style="text-align:right" | 139

| 228.0310211(27)

| 6.13(2) h

| β⁻

| ²²⁸Th

| 3+

| TraceIntermediate decay product of ²³²Th

|-id=Actinium-229

| ²²⁹Ac

| style="text-align:right" | 89

| style="text-align:right" | 140

| 229.03302(4)

| 62.7(5) min

| β⁻

| ²²⁹Th

| (3/2+)

|-id=Actinium-230

| ²³⁰Ac

| style="text-align:right" | 89

| style="text-align:right" | 141

| 230.03629(32)

| 122(3) s

| β⁻

| ²³⁰Th

| (1+)

|-id=Actinium-231

| ²³¹Ac

| style="text-align:right" | 89

| style="text-align:right" | 142

| 231.03856(11)

| 7.5(1) min

| β⁻

| ²³¹Th

| (1/2+)

|-id=Actinium-232

| ²³²Ac

| style="text-align:right" | 89

| style="text-align:right" | 143

| 232.04203(11)

| 119(5) s

| β⁻

| ²³²Th

| (1+)

|-id=Actinium-233

| ²³³Ac

| style="text-align:right" | 89

| style="text-align:right" | 144

| 233.04455(32)#

| 145(10) s

| β⁻

| ²³³Th

| (1/2+)

|-id=Actinium-234

| ²³⁴Ac

| style="text-align:right" | 89

| style="text-align:right" | 145

| 234.04842(43)#

| 44(7) s

| β⁻

| ²³⁴Th

|-id=Actinium-235

| ²³⁵Ac

| style="text-align:right" | 89

| style="text-align:right" | 146

| 235.05123(38)#

| 60(4) s

| β⁻

| ²³⁵Th

| 1/2+#

|-id=Actinium-236

| ²³⁶Ac{{cite journal|last=Chen|first=L.|display-authors=etal|date=2010|title=Discovery and investigation of heavy neutron-rich isotopes with time-resolved Schottky spectrometry in the element range from thallium to actinium |url=http://epubs.surrey.ac.uk/7511/2/10_esr-trans-pb_plb_chen_preprint.pdf|journal=Physics Letters B|volume=691|issue=5|pages=234–237|doi=10.1016/j.physletb.2010.05.078|bibcode=2010PhLB..691..234C }}

| style="text-align:right" | 89

| style="text-align:right" | 147

| 236.05530(54)#

| {{val|72|345|33|u=s}}

| β⁻

| ²³⁶Th

Actinides vs fission products

Notable isotopes

=Actinium-225=

Actinium-225 is a highly radioactive isotope with 136 neutrons. It is an alpha emitter and has a half-life of 9.919 days. As of 2024, it is being researched as a possible alpha source in targeted alpha therapy.{{cite journal |last1=A. Scheinberg |first1=David |last2=R. McDevitt |first2=Michael |title=Actinium-225 in Targeted Alpha-Particle Therapeutic Applications |journal=Current Radiopharmaceuticals |date=1 October 2011 |volume=4 |issue=4 |pages=306–320 |doi=10.2174/1874471011104040306|pmid=22202153 |pmc=5565267 }}{{cite journal |last1=Reissig |first1=Falco |last2=Bauer |first2=David |last3=Zarschler |first3=Kristof |last4=Novy |first4=Zbynek |last5=Bendova |first5=Katerina |last6=Ludik |first6=Marie-Charlotte |last7=Kopka |first7=Klaus |last8=Pietzsch |first8=Hans-Jürgen |last9=Petrik |first9=Milos |last10=Mamat |first10=Constantin |title=Towards Targeted Alpha Therapy with Actinium-225: Chelators for Mild Condition Radiolabeling and Targeting PSMA—A Proof of Concept Study |journal=Cancers |date=20 April 2021 |volume=13 |issue=8 |pages=1974 |doi=10.3390/cancers13081974|doi-access=free |pmid=33923965 |pmc=8073976 }}{{cite journal |last1=Bidkar |first1=Anil P. |last2=Zerefa |first2=Luann |last3=Yadav |first3=Surekha |last4=VanBrocklin |first4=Henry F. |last5=Flavell |first5=Robert R. |title=Actinium-225 targeted alpha particle therapy for prostate cancer |journal=Theranostics |date=2024 |volume=14 |issue=7 |pages=2969–2992 |doi=10.7150/thno.96403}} Actinium-225 undergoes a series of three alpha decays – via the short-lived francium-221 and astatine-217 – to ²¹³Bi, which itself is used as an alpha source.{{cite journal |last1=Ahenkorah |first1=Stephen |last2=Cassells |first2=Irwin |last3=Deroose |first3=Christophe M. |last4=Cardinaels |first4=Thomas |last5=Burgoyne |first5=Andrew R. |last6=Bormans |first6=Guy |last7=Ooms |first7=Maarten |last8=Cleeren |first8=Frederik |title=Bismuth-213 for Targeted Radionuclide Therapy: From Atom to Bedside |journal=Pharmaceutics |date=21 April 2021 |volume=13 |issue=5 |pages=599 |doi=10.3390/pharmaceutics13050599|doi-access=free |pmc=8143329 }} Another benefit is that the decay chain of ²²⁵Ac ends in the nuclide ²⁰⁹Bi,{{refn | group = note | Bismuth-209 decays into thallium-205 with a half-life exceeding 10¹⁹ years, but this half-life is so long that for practical purposes bismuth-209 can be considered stable.}} which has a considerably shorter biological half-life than lead.{{cite book |title=Handbook on the toxicology of metals. Volume 2: Specific metals |date=2015 |publisher=Elsevier, Aademic Press |location=Amsterdam Boston Heidelberg London |isbn=978-0-12-398293-3 |page=655 |edition=Fourth}}{{cite journal |last1=Wani |first1=Ab Latif |last2=Ara |first2=Anjum |last3=Usmani |first3=Jawed Ahmad |title=Lead toxicity: a review |journal=Interdisciplinary Toxicology |date=1 June 2015 |volume=8 |issue=2 |pages=55–64 |doi=10.1515/intox-2015-0009|pmc=4961898 }} However, a major factor limiting its usage is the difficulty in producing the short-lived isotope, as it is most commonly isolated from aging parent nuclides (such as ²³³U); it may also be produced in cyclotrons, linear accelerators, or fast breeder reactors.{{cite journal |last1=Dhiman |first1=Deeksha |last2=Vatsa |first2=Rakhee |last3=Sood |first3=Ashwani |title=Challenges and opportunities in developing Actinium-225 radiopharmaceuticals |journal=Nuclear Medicine Communications |date=September 2022 |volume=43 |issue=9 |pages=970–977 |doi=10.1097/MNM.0000000000001594|pmid=35950353 }}

=Actinium-226=

Actinium-226 is an isotope of actinium with a half-life of 29.37 hours. It mainly (83%) undergos beta decay, sometimes (17%) undergo electron capture, and rarely (0.006%) undergo alpha decay.{{NUBASE2020|ref}} There are researches on ²²⁶Ac to use it in SPECT.{{cite journal | last=Koniar | first=Helena | last2=Rodríguez-Rodríguez | first2=Cristina | last3=Radchenko | first3=Valery | last4=Yang | first4=Hua | last5=Kunz | first5=Peter | last6=Rahmim | first6=Arman | last7=Uribe | first7=Carlos | last8=Schaffer | first8=Paul | title=SPECT imaging of ²²⁶Ac as a theranostic isotope for ²²⁵Ac radiopharmaceutical development | journal=Physics in Medicine and Biology | volume=67 | issue=18 | date=2022-09-12 | issn=1361-6560 | pmid=35985341 | doi=10.1088/1361-6560/ac8b5f}}{{cite journal | last=Koniar | first=Helena | last2=Wharton | first2=Luke | last3=Ingham | first3=Aidan | last4=Rodríguez-Rodríguez | first4=Cristina | last5=Kunz | first5=Peter | last6=Radchenko | first6=Valery | last7=Yang | first7=Hua | last8=Rahmim | first8=Arman | last9=Uribe | first9=Carlos | last10=Schaffer | first10=Paul | title=In vivoquantitative SPECT imaging of actinium-226: feasibility and proof-of-concept | journal=Physics in Medicine and Biology | volume=69 | issue=15 | date=2024-07-16 | issn=1361-6560 | pmid=38925140 | doi=10.1088/1361-6560/ad5c37| doi-access=free }}

=Actinium-227=

Actinium-227 is the most stable isotope of actinium, with a half-life of 21.772 years. It mainly (98.62%) undergos beta decay, but sometimes (1.38%) it will undergo alpha decay instead.{{NUBASE2020|ref}} ²²⁷Ac is a member of the actinium series. It is found only in traces in uranium ores – one tonne of uranium in ore contains about 0.2 milligrams of ²²⁷Ac.{{cite journal |doi=10.1021/ja01158a033 |last1=Hagemann |date=1950 |first1=French |pages=768–771 |volume=72 |journal=Journal of the American Chemical Society |title=The Isolation of Actinium |issue=2}}{{Greenwood&Earnshaw2nd|page=946}} ²²⁷Ac is prepared, in milligram amounts, by the neutron irradiation of {{chem2|^{226}Ra|link=Radium-226}} in a nuclear reactor.{{cite book |author=Emeleus, H. J. |title=Advances in inorganic chemistry and radiochemistry |url=https://books.google.com/books?id=K5_LSQqeZ_IC&pg=PA16 |date= 1987 |publisher=Academic Press |isbn=978-0-12-023631-2 |pages=16–}}

:^{226}_{88}Ra + ^{1}_{0}n -> ^{227}_{88}Ra ->[\beta^-][42.2 \ \ce{min}] ^{227}_{89}Ac

²²⁷Ac is highly radioactive and was therefore studied for use as an active element of radioisotope thermoelectric generators, for example in spacecraft. The oxide of ²²⁷Ac pressed with beryllium is also an efficient neutron source with the activity exceeding that of the standard americium-beryllium and radium-beryllium pairs.Russell, Alan M. and Lee, Kok Loong (2005) [https://books.google.com/books?id=fIu58uZTE-gC&pg=PA470 Structure-property relations in nonferrous metals]. Wiley. {{ISBN|0-471-64952-X}}, pp. 470–471 In all those applications, ²²⁷Ac (a beta source) is merely a progenitor which generates alpha-emitting isotopes upon its decay. Beryllium captures alpha particles and emits neutrons owing to its large cross-section for the (α,n) nuclear reaction:

: ^{9}_{4}Be + ^{4}_{2}He -> ^{12}_{6}C + ^{1}_{0}n + \gamma

The ²²⁷AcBe neutron sources can be applied in a neutron probe – a standard device for measuring the quantity of water present in soil, as well as moisture/density for quality control in highway construction.Majumdar, D. K. (2004) [https://books.google.com/books?id=hf1j9v4v3OEC&pg=PA108 Irrigation Water Management: Principles and Practice]. {{ISBN|81-203-1729-7}} p. 108Chandrasekharan, H. and Gupta, Navindu (2006) [https://books.google.com/books?id=45IDh4Lt8xsC&pg=PA203 Fundamentals of Nuclear Science – Application in Agriculture]. {{ISBN|81-7211-200-9}} pp. 202 ff Such probes are also used in well logging applications, in neutron radiography, tomography and other radiochemical investigations.{{cite journal |title = Neutron Spectrum of an Actinium–Beryllium Source |first1 = W. R. |last1 = Dixon |journal = Can. J. Phys. |volume = 35 |issue = 6 |pages = 699–702 |date = 1957 |doi = 10.1139/p57-075 |last2 = Bielesch |first2 = Alice |last3 = Geiger |first3 = K. W.|bibcode = 1957CaJPh..35..699D }}

The medium half-life of ²²⁷Ac makes it a very convenient radioactive isotope in modeling the slow vertical mixing of oceanic waters. The associated processes cannot be studied with the required accuracy by direct measurements of current velocities (of the order 50 meters per year). However, evaluation of the concentration depth-profiles for different isotopes allows estimating the mixing rates. The physics behind this method is as follows: oceanic waters contain homogeneously dispersed ²³⁵U. Its decay product, ²³¹Pa, gradually precipitates to the bottom, so that its concentration first increases with depth and then stays nearly constant. ²³¹Pa decays to ²²⁷Ac; however, the concentration of the latter isotope does not follow the ²³¹Pa depth profile, but instead increases toward the sea bottom. This occurs because of the mixing processes which raise some additional ²²⁷Ac from the sea bottom. Thus analysis of both ²³¹Pa and ²²⁷Ac depth profiles allows researchers to model the mixing behavior.{{cite journal |last1=Nozaki |first1=Yoshiyuki |title=Excess ²²⁷Ac in deep ocean water |journal=Nature |volume=310 |pages=486–488 |date=1984 |doi=10.1038/310486a0 | issue=5977 | bibcode = 1984Natur.310..486N|s2cid=4344946 }}{{cite journal |last1=Geibert |first1=W. |last2=Rutgers Van Der Loeff |first2=M. M. |last3=Hanfland |first3=C. |last4=Dauelsberg |first4=H.-J. |title=Actinium-227 as a deep-sea tracer: sources, distribution and applications |journal=Earth and Planetary Science Letters |volume=198 |issue=1–2 |pages=147–165 |date=2002 |doi=10.1016/S0012-821X(02)00512-5 |bibcode=2002E&PSL.198..147G|url=https://doi.pangaea.de/10.1594/PANGAEA.90616 }}

Notes

References

Isotope masses from:
{{NUBASE 2003}}
Half-life, spin, and isomer data selected from the following sources.
{{NUBASE 2003}}
{{NNDC}}
{{CRC85|chapter=11}}

Category:Actinium

Actinium

Isotopes of actinium

List of isotopes

Actinides vs fission products

Notable isotopes

=Actinium-225=

=Actinium-226=

=Actinium-227=

See also

Notes

References