Lanthanum-149

Properties and data of the isotope ¹⁴⁹La.

Contents

General data

Name of the isotope:Lanthanum-149; La-149Symbol:¹⁴⁹La or 14957LaMass number A:149 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:92Isotopic mass:148.93535(21) u (atomic weight of Lanthanum-149)Nuclide mass:148.9040831 u (calculated nuclear mass without electrons)Mass excess:-60.22109 MeVMass defect:1.307849096 u (per nucleus)Nuclear binding energy:1218.25358583 MeV (per nucleus)
8.17619856 MeV (average binding energy per nucleon)Separation energy:S_N = 5.58(20) MeV (first neutron)
S_P = 9.92(21) MeV (first proton)Half-life:1.05(3) sDecay constant λ:0.66014017196185 s^-1Specific activity α:2.686119664092 × 10⁺²¹ Bq g^-1
72597828759.262 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2-)Year of discovery:1979

Radioactive Decay

Half-life T_½ = 1.05(3) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁴⁹Ce	98.6 %	6.45(20) MeV
β^-, n	¹⁴⁸Ce	1.43(28) %	2.11(20) MeV

Parent Nuclides

Direct parent isotope is: ¹⁴⁹Ba.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 92) and isobaric (same nucleon number A = 149) with Lanthanum-149. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 92	Isobar A = 149
53	¹⁴⁵I
54	¹⁴⁶Xe
55	¹⁴⁷Cs	¹⁴⁹Cs
56	¹⁴⁸Ba	¹⁴⁹Ba
57	¹⁴⁹La	¹⁴⁹La
58	¹⁵⁰Ce	¹⁴⁹Ce
59	¹⁵¹Pr	¹⁴⁹Pr
60	¹⁵²Nd	¹⁴⁹Nd
61	¹⁵³Pm	¹⁴⁹Pm
62	¹⁵⁴Sm	¹⁴⁹Sm
63	¹⁵⁵Eu	¹⁴⁹Eu
64	¹⁵⁶Gd	¹⁴⁹Gd
65	¹⁵⁷Tb	¹⁴⁹Tb
66	¹⁵⁸Dy	¹⁴⁹Dy
67	¹⁵⁹Ho	¹⁴⁹Ho
68	¹⁶⁰Er	¹⁴⁹Er
69	¹⁶¹Tm	¹⁴⁹Tm
70	¹⁶²Yb	¹⁴⁹Yb
71	¹⁶³Lu	¹⁴⁹Lu
72	¹⁶⁴Hf
73	¹⁶⁵Ta
74	¹⁶⁶W
75	¹⁶⁷Re
76	¹⁶⁸Os
77	¹⁶⁹Ir
78	¹⁷⁰Pt
79	¹⁷¹Au
80	¹⁷²Hg