Lanthanum-138

Properties and data of the isotope ¹³⁸La.

Content

General data

Name of the isotope:Lanthanum-138; La-138Symbol:¹³⁸La or 13857LaMass number A:138 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:81Isotopic mass:137.907118(3) u (atomic weight of Lanthanum-138)Nuclide mass:137.8758511 u (calculated nuclear mass without electrons)Mass excess:-86.51903 MeVMass defect:1.24076702 u (per nucleus)Nuclear binding energy:1155.76703453 MeV (per nucleus)
8.37512344 MeV (average binding energy per nucleon)Separation energy:S_N = 7.450(4) MeV (first neutron)
S_P = 6.087(3) MeV (first proton)Half-life:1.02(1) × 10¹¹ aDecay constant λ:2.133937175697 × 10^-19 s^-1Specific activity α:938.01972688384 Bq g^-1
2.535188451037 × 10^-8 Ci g^-1Spin and parity:
(nuclear angular momentum)5+Magnetic dipole moment:μ(μ_N) = +3.7084(2)Charge radius:4.8473(51) femtometer fmYear of discovery:1947

Radioactive Decay

Half-life T_½ = 1.02(1) × 10¹¹ a respectively 3.248208 × 10¹⁸ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β⁺	¹³⁸Ba	65.6(5) %	1.742(3) MeV
β^-	¹³⁸Ce	34.4(5) %	1.052(4) MeV

Occurrence

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

	Atomic Mass m_a	Quantity	Half-life	Spin
Lanthanum Isotopic mixture	138.90547 u	100 %
Isotope ¹³⁸La	137.907118(3) u	0.08881(71) %	1.02(1) × 10¹¹ a	5+
Isotope ¹³⁹La	138.90636(2) u	99.91119(71) %	stable	7/2+

NMR data

Nuclear magnetic properties of the NMR active Nuclide ¹³⁸La

Isotope:¹³⁸La-NMRQuantity:0.08881(71) %Spin:5+Nuclearmagnetic moment
μ/μ_N:+3.7084(2)Gyromagnetic ratio γ:3.5575 · 10⁷ rad T^-1 s^-1Nuclear g-factor:g_l = 0.74168Quadrupole moment Q:+ 0.45(2) barn (100 fm²)Resonance frequency:v₀ = 5.6615 at 1 TRelative Sensitivity:0.09404 (H₀ = const.)
5.3189 (v₀ = const.)
[related to ¹H = 1.000]

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
^138mLa	72.57(3) keV	116(5) ns	(3)+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 81) and isobaric (same nucleon number A = 138) with Lanthanum-138. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 81	Isobar A = 138
45	¹²⁶Rh
46	¹²⁷Pd
47	¹²⁸Ag
48	¹²⁹Cd
49	¹³⁰In
50	¹³¹Sn	¹³⁸Sn
51	¹³²Sb	¹³⁸Sb
52	¹³³Te	¹³⁸Te
53	¹³⁴I	¹³⁸I
54	¹³⁵Xe	¹³⁸Xe
55	¹³⁶Cs	¹³⁸Cs
56	¹³⁷Ba	¹³⁸Ba
57	¹³⁸La	¹³⁸La
58	¹³⁹Ce	¹³⁸Ce
59	¹⁴⁰Pr	¹³⁸Pr
60	¹⁴¹Nd	¹³⁸Nd
61	¹⁴²Pm	¹³⁸Pm
62	¹⁴³Sm	¹³⁸Sm
63	¹⁴⁴Eu	¹³⁸Eu
64	¹⁴⁵Gd	¹³⁸Gd
65	¹⁴⁶Tb	¹³⁸Tb
66	¹⁴⁷Dy	¹³⁸Dy
67	¹⁴⁸Ho
68	¹⁴⁹Er
69	¹⁵⁰Tm
70	¹⁵¹Yb
71	¹⁵²Lu
72	¹⁵³Hf