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Isotopes of Americium

List, data and properties of all known isotopes of Americium as well as radioactive decay products and intermediate products.

 

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

 

Atomic Properties

Isotope
Nuclide
ZANNameAtomic Mass
[Nuclear Mass]
{Mass Excess}
Spin I
(h/2π)
μParent
123456789
223Am95223128Americium-223223 u
[222.9478921 u]
{0 MeV}
229Am95229134Americium-229229.04525(9) u
[228.9931421 u]
{42.1501 MeV}
223Bk
230Am95230135Americium-230230.04609(14) u
[229.9939821 u]
{42.93256 MeV}
231Am95231136Americium-231
232Am95232137Americium-232232.04653(32) u
[231.9944221 u]
{43.34242 MeV}
233Am95233138Americium-233233.04644(11) u
[232.9943321 u]
{43.25858 MeV}
234Am95234139Americium-234234.04773(17) u
[233.9956221 u]
{44.46021 MeV}
235Am95235140Americium-235235.04791(6) u
[234.9958021 u]
{44.62788 MeV}
5/2-
236Am95236141Americium-236236.04943(12) u
[235.9973221 u]
{46.04375 MeV}
5-
237Am95237142Americium-237237.04999(6) u
[236.9978821 u]
{46.56539 MeV}
5/2(-)
238Am95238143Americium-238238.05198(5) u
[237.9998721 u]
{48.41906 MeV}
1+
238mAm95238143Americium-238m238.05198(5) u
[237.9998721 u]
{48.41906 MeV}
239Am95239144Americium-239239.0530228(21) u
[239.0009149 u]
{49.39042 MeV}
(5/2)-239Cm
243Bk
239mAm95239144Americium-239m239.0530228(21) u
[239.0009149 u]
{49.39042 MeV}
(7/2+)+2.59(18)
240Am95240145Americium-240240.055298(15) u
[240.0031901 u]
{51.50976 MeV}
(3-)244Bk
240mAm95240145Americium-240m240.055298(15) u
[240.0031901 u]
{51.50976 MeV}
241Am95241146Americium-241241.0568273(12) u
[241.0047194 u]
{52.93429 MeV}
5/2-+ 1.58(1)245Bk
241Cm
241Pu
241mAm95241146Americium-241m241.0568273(12) u
[241.0047194 u]
{52.93429 MeV}
242Am95242147Americium-242242.0595474(12) u
[242.0074395 u]
{55.46805 MeV}
1-+ 0.3879(15)
242m1Am95242147Americium-242m1242.0595474(12) u
[242.0074395 u]
{55.46805 MeV}
5-+ 0.97(5)
242m2Am95242147Americium-242m2242.0595474(12) u
[242.0074395 u]
{55.46805 MeV}
(2+,3-)- 1.14
243Am95243148Americium-243243.0613799(15) u
[243.009272 u]
{57.17501 MeV}
5/2-+ 1.50(1)247Bk
243Cm
243Pu
244Am95244149Americium-244244.0642830(16) u
[244.0121751 u]
{59.87923 MeV}
(6-)
244mAm95244149Americium-244m244.0642830(16) u
[244.0121751 u]
{59.87923 MeV}
1+
245Am95245150Americium-245245.0664529(20) u
[245.014345 u]
{61.90048 MeV}
(5/2)+249Bk
245Pu
246Am95246151Americium-246246.069774(19) u
[246.0176661 u]
{64.99406 MeV}
(7-)246Pu
246m1Am95246151Americium-246m1246.069774(19) u
[246.0176661 u]
{64.99406 MeV}
2(-)
246m2Am95246151Americium-246m2246.069774(19) u
[246.0176661 u]
{64.99406 MeV}
247Am95247152Americium-247247.07209(11) u
[247.0199821 u]
{67.1514 MeV}
(5/2)
248Am95248153Americium-248248.07575(21) u
[248.0236421 u]
{70.56067 MeV}
249Am95249154Americium-249

 

Radioactive Decay Properties

IsotopeRadioactive DecayAEExtern
Half-lifeDecay ModeProbabilityEnergy
1101112131415
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
> 3 %
? %
7.06(5) MeV
3.21(11) 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) %
6.20(3) MeV
1.48(6) 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 %2500 keVAL
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 %2500 keVAL
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 div3000 keV
Am-241432.6(6) aα → 237Np
SF div
ca. 100 %
Spuren
5.63782(12) MeV
AL
Am-241m1.2(3) μsSF div100 %2200(100) keVAL
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


48.60(5) keVAL
Am-242m214.0(10) msIso ? → 242Am
SF div
? %
ca. 100 %

2200(80) keVAL
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) %

86.5(16) keVAL
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 %2000 keVAL
Am-24723.0(13) minβ-247Cm100 %1.62(10) MeVAL
Am-248AL
Am-249- ungelistet -AL

 

Notes (related to the columns):

1 - nuclide, isotope symbol.
2 - Z = number of protons (atomic number).
3 - Mass number A.
4 - N = number of neutrons.
5 - Identification of the Americium isotope.
6 - 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.
7 - Nuclear spin I, unit: h/2π.
8 - Nuclear magnetic moment μmag.
9 - 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.
10 - Decay: Half-live of the Americium isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
11 - Decay: 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.
12 - Decay percentage in percent (%).
13 - Decay energy; Particle energy related to decay type.
14 - AE = Excitation energy for metastable nuclei.
15 - 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
107 rad T-1 s-1
Quadrupole
moment
Q fm-2
Resonant
frequency
v0 bei 1 T
Relative
sensitivity
H0 = const.
v0 = const. 2)
241Am

5/2-
+ 1,58(1)1,04420,0(1300)
243Am
100 %
5/2-
+ 1,50(1)1,54420,0(1300)4,60,01446
1,2532

1) Quantity Percentage of natural occurrence.

2) 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.

 


Category: Isotopes

Last update: 05.07.2020



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