Plutonium-244

Properties and data of the isotope ²⁴⁴Pu.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Plutonium-244 is a radioisotope of the chemical element plutonium, which has 150 neutrons in its atomic nucleus in addition to the element-specific 94 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 244.

Pu-244 was discovered – according to a 1954 article [1] – by irradiating plutonium-243-containing material samples with neutrons according to the

²⁴³Pu(n,γ)²⁴⁴Pu.

The authors also suggested that it could have been formed by electron capture of americium-244.

See also: List of individual Plutonium isotopes (and general data sources).

General data

Name of the isotope:Plutonium-244; Pu-244Symbol:²⁴⁴Pu or 24494PuMass number A:244 (= number of nucleons)Atomic number Z:94 (= number of protons)Neutrons N:150Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.5957446808511 (= neutron-proton ratio)Neutron excess (N-Z):56Isotopic mass:244.0642044(25) u (atomic weight of Plutonium-244)Nuclide mass:244.0126449 u (calculated nuclear mass without electrons)Mass excess:59.80601 MeVMass defect:1.971086008 u (per nucleus)Nuclear binding energy:1836.05478994 MeV (per nucleus)
7.52481471 MeV (average binding energy per nucleon)Separation energy:S_N = 6.0199(29) MeV (first neutron)
S_P = 7.289(32) MeV (first proton)Half-life:8.13(3) × 10⁷ aDecay constant λ:2.701719294746 × 10^-16 s^-1Specific activity α:666808.77692501 Bq g^-1
1.802185883581 × 10^-5 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.8948(382) femtometer fmYear of discovery:1954

Radioactive Decay

Half-life T_½ = 8.13(3) × 10⁷ a respectively 2.565578081734330 × 10¹⁵ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁴⁰U	99.877(6) %	4.6656(10) MeV
SZ	div	0.123(6) %

Parent Nuclides

Direct parent isotopes are: ²⁴⁴Np, ²⁴⁸Cm.

Occurrence

Comparison of the natural Plutonium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Plutonium Isotopic mixture	244.064205302 u	100 %
Isotope ²⁴⁴Pu	244.0642044(25) u	100 %	8.13(3) × 10⁷ a	0+

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
^244mPu	1211.2(8) keV	1.75(12) s	8-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 150) and isobaric (same nucleon number A = 244) with Plutonium-244. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 150	Isobar A = 244
92	²⁴²U
93	²⁴³Np	²⁴⁴Np
94	²⁴⁴Pu	²⁴⁴Pu
95	²⁴⁵Am	²⁴⁴Am
96	²⁴⁶Cm	²⁴⁴Cm
97	²⁴⁷Bk	²⁴⁴Bk
98	²⁴⁸Cf	²⁴⁴Cf
99	²⁴⁹Es	²⁴⁴Es
100	²⁵⁰Fm	²⁴⁴Fm
101	²⁵¹Md	²⁴⁴Md
102	²⁵²No
103	²⁵³Lr
104	²⁵⁴Rf
105	²⁵⁵Db

External data and identifiers

Adopted Levels, Gammas:NuDat 244Pu

Literature and References

[1] - M. H. Studier, P. R. Fields, P. H. Sellers et al.:
Plutonium-244 from Pile-Irradiated Plutonium.
In: Physical Review, 93, 1433, (1954), DOI 10.1103/PhysRev.93.1433.

[2] - Christopher R. Armstrong et al.:
Anthropogenic plutonium-244 in the environment: Insights into plutonium’s longest-lived isotope.
In: Scientific Reports, 6, 21512, (2016), DOI 10.1038/srep21512.

[3] - Richard M. Essex et al.:
A highly-enriched ²⁴⁴Pu reference material for nuclear safeguards and nuclear forensics measurements.
In: Journal of Radioanalytical and Nuclear Chemistry, 324, (2020), DOI 10.1007/s10967-020-07075-y.

[4] - Maria Lugaro et al.:
Origin of Plutonium-244 in the Early Solar System.
In: Universe, 8(7), 343, (2022), DOI 10.3390/universe8070343.

[5] - Malcolm J. Joyce et al.:
Using ²⁴⁴Pu/²³⁹Pu to pinpoint ²⁴⁰Pu/²³⁹Pu signatures of locally derived reactor material in the terrestrial environment.
In: International Journal of Modern Physics E, 34, 9, (2025), DOI 10.1142/S0218301325450053.