Isotopes of americium#Americium-237

{{Anchor|Americium-224|Americium-225|Americium-226|Americium-227|Americium-228|Americium-231|Americium-248|Americium-249}}

{{Isotopes table

| symbol = Am

| refs = NUBASE2020

| notes = m, unc(), mass#, exen#, spin(), spin#, CD, EC, IT, SF

}}

|-id=Americium-223

| ²²³Am{{refn|group=n|The discovery of this isotope is uncertain due to disagreements between theoretical predictions and reported experimental data.{{cite journal |title=New short-lived isotope ²²³Np and the absence of the Z = 92 subshell closure near N = 126

|first=M. D. |last=Sun |display-authors=et al. |journal=Physics Letters B |volume=771 |date=2017 |pages=303–308 |doi=10.1016/j.physletb.2017.03.074 |url=https://www.researchgate.net/publication/317142406|doi-access=free |bibcode=2017PhLB..771..303S }}}}

| style="text-align:right" | 95

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

| 223.04584(32)#

| 10(9) ms

| α

| ²¹⁹Np

| 9/2–#

|-id=Americium-229

| ²²⁹Am

| style="text-align:right" | 95

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

| 229.04528(11)

| 1.8(15) s

| α

| ²²⁵Np

| 5/2–#

|-id=Americium-230

| rowspan=2 | ²³⁰Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 135

| rowspan=2 | 230.04603(15)#

| rowspan=2 | 40(9) s

| β⁺ (<70%)

| ²³⁰Pu

| rowspan=2 | 1–#

|-

| β⁺SF (>30%)

| (various)

|-id=Americium-232

| rowspan=3 | ²³²Am

| rowspan=3 style="text-align:right" | 95

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

| rowspan=3 | 232.04661(32)#

| rowspan=3 | 1.31(4) min

| β⁺ (97%)

| ²³²Pu

| rowspan=3 | 1–#

|-

| α (3%)

| ²²⁸Np

|-

| β⁺SF (0.069%)

| (various)

|-id=Americium-233

| rowspan=2 | ²³³Am

| rowspan=2 style="text-align:right" | 95

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

| rowspan=2 | 233.04647(12)#

| rowspan=2 | 3.2(8) min

| β⁺ (95.5%)

| ²³³Pu

| rowspan=2 | 5/2–#

|-

| α (4.5%)

| ²²⁹Np

|-id=Americium-234

| rowspan=3 | ²³⁴Am

| rowspan=3 style="text-align:right" | 95

| rowspan=3 style="text-align:right" | 139

| rowspan=3 | 234.04773(17)#

| rowspan=3 | 2.32(8) min

| β⁺ (99.95%)

| ²³⁴Pu

| rowspan=3 | 0–#

|-

| α (0.039%)

| ²³⁰Np

|-

| β⁺, SF (0.0066%)

| (various)

|-id=Americium-235

| rowspan=2 | ²³⁵Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 140

| rowspan=2 | 235.047906(57)

| rowspan=2 | 10.3(6) min

| β⁺ (99.60%)

| ²³⁵Pu

| rowspan=2 | 5/2−#

|-

| α (0.40%)

| ²³¹Np

|-id=Americium-236

| rowspan=2 | ²³⁶Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 141

| rowspan=2 | 236.04943(13)#

| rowspan=2 | 3.6(1) min

| β⁺

| ²³⁶Pu

| rowspan=2 | 5−

|-

| α (4×10⁻³%)

| ²³²Np

|-id=Americium-236m

| rowspan=2 style="text-indent:1em" | ^236mAm

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

| rowspan=2 | 2.9(2) min

| β⁺

| ²³⁶Pu

| rowspan=2 | (1−)

|-

| α ?

| ²³²Np

|-id=Americium-237

| rowspan=2 | ²³⁷Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 142

| rowspan=2 | 237.049995(64)#

| rowspan=2 | 73.6(8) min

| β⁺ (99.975%)

| ²³⁷Pu

| rowspan=2 | 5/2−

|-

| α (.025%)

| ²³³Np

|-id=Americium-238

| rowspan=2 | ²³⁸Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 143

| rowspan=2 | 238.051983(63)

| rowspan=2 | 98(3) min

| β⁺

| ²³⁸Pu

| rowspan=2 | 1+

|-

| α (1.0×10⁻⁴%)

| ²³⁴Np

|-id=Americium-238m

| rowspan=2 style="text-indent:1em" | ^238mAm

| rowspan=2 colspan="3" style="text-indent:2em" | 2500(200)# keV

| rowspan=2 | 35(18) μs

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²³⁸Am

|-id=Americium-239

| rowspan=2 | ²³⁹Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 144

| rowspan=2 | 239.0530227(21)

| rowspan=2 | 11.9(1) h

| EC (99.99%)

| ²³⁹Pu

| rowspan=2 | 5/2−

|-

| α (0.01%)

| ²³⁵Np

|-id=Americium-239m

| rowspan=2 style="text-indent:1em" | ^239mAm

| rowspan=2 colspan="3" style="text-indent:2em" | 2500(200) keV

| rowspan=2 | 163(12) ns

| SF

| (various)

| rowspan=2 | (7/2+)

|-

| IT ?

| ²³⁹Am

|-id=Americium-240

| rowspan=2 | ²⁴⁰Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 145

| rowspan=2 | 240.055298(15)

| rowspan=2 | 50.8(3) h

| β⁺

| ²⁴⁰Pu

| rowspan=2 | (3−)

|-

| α (1.9×10⁻⁴%)

| ²³⁶Np

|-id=Americium-240m

| rowspan=2 style="text-indent:1em" | ^240mAm

| rowspan=2 colspan="3" style="text-indent:2em" | 3000(200) keV

| rowspan=2 | 940(40) μs

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²⁴⁰Am

|-

| rowspan=2 | ²⁴¹Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 146

| rowspan=2 | 241.0568273(12)

| rowspan=2 | 432.6(6) y

| α

| ²³⁷Np

| rowspan=2 | 5/2−

|-

| SF (3.6×10⁻¹⁰%)

| (various)

|-id=Americium-241m

| style="text-indent:1em" | ^241mAm

| colspan="3" style="text-indent:2em" | 2200(200) keV

| 1.2(3) μs

| SF

| (various)

|

|-id=Americium-242

| rowspan=2 | ²⁴²Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 147

| rowspan=2 | 242.0595474(12)

| rowspan=2 | 16.02(2) h

| β⁻ (82.7%)

| ²⁴²Cm

| rowspan=2 | 1−

|-

| EC (17.3%)

| ²⁴²Pu

|-id=Americium-242m1

| rowspan=3 style="text-indent:1em" | ^242m1Am

| rowspan=3 colspan="3" style="text-indent:2em" | 48.60(5) keV

| rowspan=3 | 141(2) y

| IT (99.54%)

| ²⁴²Am

| rowspan=3 | 5−

|-

| α (.46%)

| ²³⁸Np

|-

| SF ?

| (various)

|-id=Americium-242m2

| rowspan=2 style="text-indent:1em" | ^242m2Am

| rowspan=2 colspan="3" style="text-indent:2em" | 2200(80) keV

| rowspan=2 | 14.0(10) ms

| SF

| (various)

| rowspan=2 | (2+, 3−)

|-

| IT ?

| ²⁴²Am

|-

| rowspan=2 | ²⁴³Am

| rowspan=2 style="text-align:right" | 95

| rowspan=2 style="text-align:right" | 148

| rowspan=2 | 243.0613799(15)

| rowspan=2 | 7,350(9) y

| α

| ²³⁹Np

| rowspan=2 | 5/2−

|-

| SF (3.7×10⁻⁹%)

| (various)

|-id=Americium-243m

| rowspan=2 style="text-indent:1em" | ^243mAm

| rowspan=2 colspan="3" style="text-indent:2em" | 2300(200) keV

| rowspan=2 | 5.5(5) μs

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²⁴³Am

|-id=Americium-244

| ²⁴⁴Am

| style="text-align:right" | 95

| style="text-align:right" | 149

| 244.0642829(16)

| 10.01(3) h

| β⁻

| ²⁴⁴Cm

| (6−)

|-id=Americium-244m1

| rowspan=2 style="text-indent:1em" | ^244m1Am

| rowspan=2 colspan="3" style="text-indent:2em" | 89.3(16) keV

| rowspan=2 | 26.13(43) min

| β⁻ (99.96%)

| ²⁴⁴Cm

| rowspan=2 | 1+

|-

| EC (0.0364%)

| ²⁴⁴Pu

|-id=Americium-244m2

| rowspan=2 style="text-indent:1em" | ^244m2Am

| rowspan=2 colspan="3" style="text-indent:2em" | 2000(200)# keV

| rowspan=2 | 900(150) μs

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²⁴⁴Am

|-id=Americium-244m3

| rowspan=2 style="text-indent:1em" | ^244m3Am

| rowspan=2 colspan="3" style="text-indent:2em" | 2200(200)# keV

| rowspan=2 | ~6.5 μs

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²⁴⁴Am

|-id=Americium-245

| ²⁴⁵Am

| style="text-align:right" | 95

| style="text-align:right" | 150

| 245.0664528(20)

| 2.05(1) h

| β⁻

| ²⁴⁵Cm

| 5/2+

|-id=Americium-245m

| rowspan=2 style="text-indent:1em" | ^245mAm

| rowspan=2 colspan="3" style="text-indent:2em" | 2400(400)# keV

| rowspan=2 | 640(60) ns

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²⁴⁵Am

|-id=Americium-246

| ²⁴⁶Am

| style="text-align:right" | 95

| style="text-align:right" | 151

| 246.069774(19)#

| 39(3) min

| β⁻

| ²⁴⁶Cm

| (7−)

|-id=Americium-246m1

| rowspan=2 style="text-indent:1em" | ^246m1Am

| rowspan=2 colspan="3" style="text-indent:2em" | 30(10)# keV

| rowspan=2 | 25.0(2) min

| β⁻

| ²⁴⁶Cm

| rowspan=2 | 2(−)

|-

| IT ?

| ²⁴⁶Am

|-id=Americium-246m2

| rowspan=2 style="text-indent:1em" | ^246m2Am

| rowspan=2 colspan="3" style="text-indent:2em" | 2000(800)# keV

| rowspan=2 | 73(10) μs

| SF

| (various)

| rowspan=2 |

|-

| IT ?

| ²⁴⁶Am

|-id=Americium-247

| ²⁴⁷Am

| style="text-align:right" | 95

| style="text-align:right" | 152

| 247.07209(11)#

| 23.0(13) min

| β⁻

| ²⁴⁷Cm

| 5/2#

{{Isotopes table/footer}}

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File:Americium button hd.jpgs.]]

{{main|Americium-241}}

Americium-241 is the most common isotope of americium in nuclear waste.[http://www.ead.anl.gov/pub/doc/Americium.pdf "Americium"] {{webarchive|url=https://web.archive.org/web/20120730003822/http://www.ead.anl.gov/pub/doc/americium.pdf |date=2012-07-30 }}. Argonne National Laboratory, EVS. Retrieved 25 December 2009. It is the isotope used in an americium smoke detector based on an ionization chamber. It is a potential fuel for long-lifetime radioisotope thermoelectric generators.

Possible parent nuclides: beta from Plutonium-241, electron capture from {{sup|241}}Cm, alpha from {{sup|245}}Bk.

{{sup|241}}Am alpha decays, with a by-product of gamma rays. Its presence in plutonium is determined by the original concentration of {{sup|241}}Pu and the sample age. Due to the low penetration of alpha radiation, {{sup|241}}Am only poses a health risk when ingested or inhaled. Older samples of plutonium containing plutonium-241 contain a buildup of {{sup|241}}Am. A chemical removal of americium from reworked plutonium (e.g. during reworking of plutonium pits) may be required.

File:Sasahara.svg

Americium-242m has a mass of 242.0595492 g/mol. It is one of the rare cases, like isotopes of silver, isotopes of holmium, isotopes of tantalum#Tantalum-180m, isotopes of rhenium, isotopes of iridium, isotopes of bismuth, isotopes of polonium and others, where a higher-energy nuclear isomer is more stable than the ground state, americium-242.[http://www.matpack.de/Info/Nuclear/Nuclids/A/Am242.html 95-Am-242] {{webarchive|url=https://web.archive.org/web/20110719060944/http://www.matpack.de/Info/Nuclear/Nuclids/A/Am242.html |date=2011-07-19 }}

{{sup|242m}}Am is fissile with a low critical mass, comparable to that of plutonium-239.{{cite web |title=Critical Mass Calculations for {{sup|241}}Am, {{sup|242m}}Am and {{sup|243}}Am |url=http://typhoon.jaea.go.jp/icnc2003/Proceeding/paper/6.5_022.pdf |archive-url=https://web.archive.org/web/20110722105207/http://typhoon.jaea.go.jp/icnc2003/Proceeding/paper/6.5_022.pdf |url-status=dead |archive-date=July 22, 2011 |access-date=February 3, 2011 }} It has a very high fission cross section, and is quickly destroyed if it is produced in a nuclear reactor. It has been investigated whether this isotope could be used for a novel type of nuclear rocket.{{cite press release |url=https://www.sciencedaily.com/releases/2001/01/010103073253.htm |title=Extremely Efficient Nuclear Fuel Could Take Man To Mars In Just Two Weeks |date=December 28, 2000 |publisher=Ben-Gurion University Of The Negev}}{{cite journal|last1=Ronen|first1=Yigal|last2=Shwageraus|first2=E.|title=Ultra-thin 241mAm fuel elements in nuclear reactors|journal=Nuclear Instruments and Methods in Physics Research A|date=2000|volume=455|issue=2|pages=442–451|doi=10.1016/s0168-9002(00)00506-4|bibcode=2000NIMPA.455..442R}}

File:Am243.png

Americium-243 has a mass of 243.06138 g/mol and a half-life of 7,370 years, the longest lasting of all americium isotopes. It is formed in the nuclear fuel cycle by neutron capture on plutonium-242 followed by beta decay.[http://www.ornl.gov/sci/isotopes/r_am243.html "Americium-243"] {{webarchive|url=https://web.archive.org/web/20110225120159/http://www.ornl.gov/sci/isotopes/r_am243.html |date=2011-02-25 }}. Oak Ridge National Laboratory. Retrieved 25 December 2009. Production increases exponentially with increasing burnup as a total of 5 neutron captures on uranium-238 are required. If MOX-fuel is used, particularly MOX-fuel high in {{chem|241|Pu}} and {{chem|242|Pu}}, more americium overall and more {{chem|243|Am}} will be produced.

It decays by either emitting an alpha particle (with a decay energy of 5.27 MeV) to become {{sup|239}}Np, which then quickly decays to plutonium-239, or rarely, by spontaneous fission.[http://education.jlab.org/itselemental/iso095.html "Isotopes of the Element Americium"]. Jefferson Lab Science Education. Retrieved 25 December 2009.

As for the other americium isotopes, and more generally for all alpha emitters, {{sup|243}}Am is carcinogenic in case of internal contamination after being inhaled or ingested. {{sup|243}}Am also presents a risk of external irradiation associated with the gamma ray emitted by its short-lived decay product neptunium-239. The external irradiation risk for the other two americium isotopes ({{sup|241}}Am and {{sup|242m}}Am) is less than 10% of that for americium-243.

{{Reflist|30em}}

• Isotope masses from:
• {{NNDC}}
• Half-life, spin, and isomer data selected from the following sources.
• {{NNDC}}
• IAEA - Nuclear Data Section. [https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html Live Chart of Nuclides.] Vienna International Centre.
• {{CRC85|chapter=11}}

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Category:Americium

Americium