Europium-139

Properties and data of the isotope ¹³⁹Eu.

Contents

General data

Name of the isotope:Europium-139; Eu-139Symbol:¹³⁹Eu or 13963EuMass number A:139 (= number of nucleons)Atomic number Z:63 (= number of protons)Neutrons N:76Isotopic mass:138.929792(14) u (atomic weight of Europium-139)Nuclide mass:138.8952342 u (calculated nuclear mass without electrons)Mass excess:-65.39833 MeVMass defect:1.221718632 u (per nucleus)Nuclear binding energy:1138.0235754 MeV (per nucleus)
8.18721997 MeV (average binding energy per nucleon)Separation energy:S_N = 11.72(3) MeV (first neutron)
S_P = 1.189(18) MeV (first proton)Half-life:17.9(6) sDecay constant λ:0.038723306176533 s^-1Specific activity α:1.689834814185 × 10⁺²⁰ Bq g^-1
4567121119.4192 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2)-Magnetic dipole moment:μ(μ_N) = 6.1(8)Nuclear g-factor:g_l = 1.1090909090909Charge radius:4.9760(92) femtometer fmYear of discovery:1975

Radioactive Decay

Half-life T_½ = 17.9(6) s respectively 1.79 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹³⁹Sm	100 %	6.982(17) MeV

Parent Nuclides

Direct parent isotope is: ¹³⁹Gd.

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
^139mEu	148.3(3) keV	10(2) μs	(7/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 76) and isobaric (same nucleon number A = 139) with Europium-139. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 76	Isobar A = 139
42	¹¹⁸Mo
43	¹¹⁹Tc
44	¹²⁰Ru
45	¹²¹Rh
46	¹²²Pd
47	¹²³Ag
48	¹²⁴Cd
49	¹²⁵In
50	¹²⁶Sn	¹³⁹Sn
51	¹²⁷Sb	¹³⁹Sb
52	¹²⁸Te	¹³⁹Te
53	¹²⁹I	¹³⁹I
54	¹³⁰Xe	¹³⁹Xe
55	¹³¹Cs	¹³⁹Cs
56	¹³²Ba	¹³⁹Ba
57	¹³³La	¹³⁹La
58	¹³⁴Ce	¹³⁹Ce
59	¹³⁵Pr	¹³⁹Pr
60	¹³⁶Nd	¹³⁹Nd
61	¹³⁷Pm	¹³⁹Pm
62	¹³⁸Sm	¹³⁹Sm
63	¹³⁹Eu	¹³⁹Eu
64	¹⁴⁰Gd	¹³⁹Gd
65	¹⁴¹Tb	¹³⁹Tb
66	¹⁴²Dy	¹³⁹Dy
67	¹⁴³Ho
68	¹⁴⁴Er
69	¹⁴⁵Tm