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Isotopes of Americium

List, data and properties of all known isotopes of Americium.

Content
Atomic properties
Decay properties
NMR active nuclides
Radiation protection
References
Americium isotopes

All atomic nuclei of the chemical element americium are summarized under americium isotopes; these consist of an atomic nucleus with 95 protons and, in the uncharged state, 95 electrons. The difference between each americium isotope is based on the number of neutrons in the nucleus.

Am-141 was the first americium isotope to be produced and characterized in 1944; to date, a total of 19 nuclides of this chemical element and a number of isomeric nuclei are known. All isotopes of americium are unstable and therefore radioactive; the most stable one (Am-243) has a half-life of 7370 years.

In nature, americium occurs at best in the smallest traces as a radioactive intermediate.

Besides applications in nuclear technology, for example as a neutron source, in nuclide batteries or for the production of other chemical elements, americium isotopes are hardly ever used. Americium-241 was used in smoke detectors (ionization smoke detectors).

 

Isotope Table: Americium

The two following tables list the most important data and properties of the Americium isotopes. Further information on the individual Americium isotopes is listed on separate pages and can be accessed via the link in column 1.

 

Atomic Properties

Isotope
Nuclide		ENAtomic Mass
[Nuclear Mass]
{Mass Excess}		Spin I
(h/2π)		Parent
123456
Americium-22322395Am128223 u
[222.9478921 u]
{0 MeV}
Americium-22922995Am134229.04525(9) u
[228.9931421 u]
{42.1501 MeV}		223Bk
Americium-23023095Am135230.04609(14) u
[229.9939821 u]
{42.93256 MeV}
Americium-23123195Am136
Americium-23223295Am137232.04653(32) u
[231.9944221 u]
{43.34242 MeV}
Americium-23323395Am138233.046470(129) u
[232.9943621 u]
{43.28653 MeV}		233Cm
Americium-23423495Am139234.04773(17) u
[233.9956221 u]
{44.46021 MeV}
Americium-23523595Am140235.04791(6) u
[234.9958021 u]
{44.62788 MeV}		5/2-
Americium-23623695Am141236.04943(12) u
[235.9973221 u]
{46.04375 MeV}		5-
Americium-23723795Am142237.050000(60) u
[236.9978921 u]
{46.5747 MeV}		5/2(-)241Bk
Americium-23823895Am143238.05198(5) u
[237.9998721 u]
{48.41906 MeV}		1+
Americium-238m238m95Am143238.05198(5) u
[237.9998721 u]
{48.41906 MeV}
Americium-23923995Am144239.0530228(21) u
[239.0009149 u]
{49.39042 MeV}		(5/2)-239Cm
243Bk
Americium-239m239m95Am144239.0530228(21) u
[239.0009149 u]
{49.39042 MeV}		(7/2+)
Americium-24024095Am145240.055298(15) u
[240.0031901 u]
{51.50976 MeV}		(3-)244Bk
Americium-240m240m95Am145240.055298(15) u
[240.0031901 u]
{51.50976 MeV}
Americium-24124195Am146241.0568273(12) u
[241.0047194 u]
{52.93429 MeV}		5/2-245Bk
241Cm
241Pu
Americium-241m241m95Am146241.0568273(12) u
[241.0047194 u]
{52.93429 MeV}
Americium-24224295Am147242.0595474(12) u
[242.0074395 u]
{55.46805 MeV}		1-
Americium-242m1242m195Am147242.0595474(12) u
[242.0074395 u]
{55.46805 MeV}		5-
Americium-242m2242m295Am147242.0595474(12) u
[242.0074395 u]
{55.46805 MeV}		(2+,3-)
Americium-24324395Am148243.0613799(15) u
[243.009272 u]
{57.17501 MeV}		5/2-247Bk
243Cm
243Pu
Americium-24424495Am149244.0642830(16) u
[244.0121751 u]
{59.87923 MeV}		(6-)
Americium-244m244m95Am149244.0642830(16) u
[244.0121751 u]
{59.87923 MeV}		1+
Americium-24524595Am150245.0664529(20) u
[245.014345 u]
{61.90048 MeV}		(5/2)+249Bk
245Pu
Americium-24624695Am151246.069774(19) u
[246.0176661 u]
{64.99406 MeV}		(7-)246Pu
Americium-246m1246m195Am151246.069774(19) u
[246.0176661 u]
{64.99406 MeV}		2(-)
Americium-246m2246m295Am151246.069774(19) u
[246.0176661 u]
{64.99406 MeV}
Americium-24724795Am152247.07209(11) u
[247.0199821 u]
{67.1514 MeV}		(5/2)
Americium-24824895Am153248.07575(21) u
[248.0236421 u]
{70.56067 MeV}
Americium-24924995Am154

 

Radioactive Decay Properties

IsotopeRadioactive DecayExtern
Half-lifeDecay ModeProbabilityEnergy
789101112
Am-2235(+12-4) msα → 219Npca. 100 %17.4 MeV
Am-2290.9(21-7) sα → 225Np
EC/β+ → 229Pu		91 %
9 %		8.14(5) MeV
4.75(10) MeV
Am-23031 sEC → 230Pu
SF div		ca. 100 %
?		6.00(13) MeV
AL
Am-231- ungelistet -AL
Am-23279(2) sEC → 232Pu
α → 228Np
EC/F div		ca. 97 %
ca. 3 %
0.069(10) %		4.98(30) MeV
7.32(30) MeV
AL
Am-2333.2(8) minα → 229Np
EC/β+ → 233Pu		4.5 %
95.5 %		7.059(53) MeV
3.233(126) MeV		AL
Am-2342.32(8) minα → 230Np
EC → 234Pu		?
ca. 100 %		6.80(15) MeV
4.11(16) MeV		AL
Am-23510.3(6) minα → 231Np
ε → 235Pu		0.40(5) %
99.60(5) %		6.576(13) MeV
2.44(6) MeV		AL
Am-2363.6(2) minα → 232Np
EC → 236Pu		? %
? %		6.26(5) MeV
3.41(11) MeV		AL
Am-23773.6(8) minα → 233Np
EC/β+ → 237Pu		0.025(3) %
99.975(3) %		6.196(30) MeV
1.478(59) MeV		AL
Am-23898(2) minα → 234Np
EC/β+ → 238Pu		0.0001 %
ca. 100 %		6.04(5) MeV
2.26(5) MeV		AL
Am-238m35 μsSF div≤ 100 %AL
Am-23911.9(1) hα → 235Np
EC → 239Pu		0.010(1) %
99.990(1) %		5.9224(14) MeV
0.801(23) MeV		AL
Am-239m163(12) nsSF div≤ 100 %AL
Am-24050.8(3) hα → 236Np
EC → 240Pu		Spuren
ca. 100 %		5.71(5) MeV
1.385(14) MeV		AL
Am-240m0.94(4) msSF div
Am-241432.6(6) aα → 237Np
SF div		ca. 100 %
Spuren		5.63782(12) MeV
AL
Am-241m1.2(3) μsSF div100 %AL
Am-24216.02(2) hβ- → 242Cm
EC → 242Pu		82.7(3) %
17.3(3) %		0.663(4) MeV
0.751(17) MeV		AL
Am-242m1141(2) aIso → 242Am
α → 238Np
SF div		99.55(2) %
0.45(2) %
Spuren

AL
Am-242m214.0(10) msIso ? → 242Am
SF div		? %
ca. 100 %
AL
Am-2437353(10) aα → 239Np
SF div		ca. 100 %
Spuren		5.4391(9) MeV
AL
Am-24410.1(1) hβ- → 244Cm100 %1.4273(10) MeVAL
Am-244m26 minβ- → 244Cm
EC/β+ → 244Pu		99.9639(13) %
0.0361(13) %
AL
Am-2452.05(1) hβ- → 245Cm100 %0.8959(15) MeVAL
Am-24639(3) minβ- → 246Cm100 %2.377(18) MeVAL
Am-246m125.0(2) minβ- → 246Cm
Iso → 246Am		ca. 100 %
0.02 %
AL
Am-246m273(10) µsSF div≤ 100 %AL
Am-24723.0(13) minβ- → 247Cm100 %1.62(10) MeVAL
Am-248AL
Am-249- ungelistet -AL

 

Notes (related to the columns):

1 - name of the nuclide, isotope.
2 - E: isotope symbol with mass number (superscript; number of nucleons) and Atomic number (subscript; number of protons).
3 - N: number of neutrons.
4 - relative atomic mass of the Americium isotope (isotopic mass including electrons) and the mass of the atomic nucleus in square brackets (nuclear mass, nuclide mass without electrons), each related to 12C = 12.00000 [2]. In addition, the mass excess is given in MeV.
5 - nuclear spin I, unit: h/2π.
6 - source nuclides: Possible, assumed or actual source nuclides (mother nuclides, parent nuclides). If applicable, the corresponding decay modes can be found in the data for the respective starting nuclide.

7 - isotope notation in short form.
8 - decay: half-live of the Americium isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
9 - decay mode: type of decay into the respective daughter nuclides with n = neutron emission; p = proton emission; α = alpha decay; β- = beta minus decay with electron emission; EC = electron capture; β+ = positron emission; ε = β+ and/or EC; Iso = isomeric transition; CD = cluster decay; SF = spontaneous decay.
10 - decay probability in percent (%).
11 - decay energy; Particle energy related to decay type.
12 - other information and notes: AL = Adopted Levels (link to external data [1]).

Miscellaneous:

()- Numbers in brackets: uncertainty to represent the spread of the reported value.
~ - Theoretical values or systematic trends.
  - unlisted-: Nuclides that have already been mentioned in the literature but for some reason can no longer be found in the current nuclide tables because their discovery e.g. has not confirmed.

 

NMR active Americium nuclides

Nuclide
quantity 1)
spin		Nuclear
magnetic
moment
μ/μN		Gyromagnetic ratio
{Quadrupole moment}		Resonant
frequency
v0 bei 1 T		Relative
sensitivity
H0 = const.
v0 = const. 3)
241Am

5/2-		+ 1,58(1)1,04
{+4,34(5)}
243Am
100 %
5/2-		+ 1,50(1)1,54
{+4,32(6)}		4,60,01446
1,2532

1) Quantity Percentage of natural occurrence.

2) Gyromagnetic ratio: 107 rad T-1 s-1
    Quadrupole moment: Q [barn] = [100 fm2]

3) Related to 1H = 1,000.

 

Radiation Protection

According to the Radiation Protection Ordinance (StrlSchV 2018, Germany), the following values (columns 1 to 7) apply to the handling of Americium radionuclides:

NuclideLimit ValueHASS limitSCDaughter NuclidesHalf-life
Am-237+106 Bq100 Bq/g73.0 min
Am-238106 Bq10 Bq/g1.6 h
Am-239106 Bq100 Bq/g11.9 h
Am-240106 Bq10 Bq/g50.8 h
Am-241104 Bq0,1 Bq/g0,06 TBq0,1 Bq cm-2432.8 a
Am-242106 Bq1000 Bq/g100 Bq cm-216.0 h
Am-242m+104 Bq0,1 Bq/g0,3 TBq0,1 Bq cm-2Np-238, Am-242141.0 a
Am-243+103 Bq0,1 Bq/g0,2 TBq0,1 Bq cm-2Np-2397400 a
Am-244106 Bq10 Bq/g0,09 TBq10.1 h
Am-244m107 Bq10000 Bq/g26.0 min
Am-245106 Bq1000 Bq/g2.1 h
Am-246105 Bq10 Bq/g39.0 min
Am-246m106 Bq10 Bq/g25.0 min

(HASS = High-Activity Sealed Radioactive Sources; SC = surface contamination)

 

Literature Sources and References

Properties of the Americium nucleides

[1] - NuDat: National Nuclear Data Center, Brookhaven National Laboratory, based on ENSDF and the Nuclear Wallet Cards.

[2] - G. Audi et. al.: The NUBASE evaluation of nuclear and decay properties. Nuclear Physics, (2003), DOI 10.1016/j.nuclphysa.2003.11.001.

[3] - Live Chart of Nuclides. Nuclear structure and decay data.

Americium: NMR properties - 241Am-NMR, 243Am-NMR

[4] - N. J. Stone: Table of nuclear magnetic dipole and electric quadrupole moments. Atomic Data and Nuclear Data Tables, (2005), DOI 10.1016/j.adt.2005.04.001.

[5] - Pekka Pyykkö: Year-2008 nuclear quadrupole moments. Molecular Physics, (2008), DOI 10.1080/00268970802018367.

[6] - Pekka Pyykkö: Year-2017 nuclear quadrupole moments. Molecular Physics, (2018), DOI 10.1080/00268976.2018.1426131.

[7] - N. J. Stone: Table of recommended nuclear magnetic dipole moments. IAEA, (2019).

More sources:

[8] - Isotopic abundances, atomic weights and isotopic masses: see respective keyword.

 

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