Lanthanum-127

Properties and data of the isotope ¹²⁷La.

Contents

General data

Name of the isotope:Lanthanum-127; La-127Symbol:¹²⁷La or 12757LaMass number A:127 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:70Isotopic mass:126.916375(28) u (atomic weight of Lanthanum-127)Nuclide mass:126.8851081 u (calculated nuclear mass without electrons)Mass excess:-77.89619 MeVMass defect:1.136195944 u (per nucleus)Nuclear binding energy:1058.35970466 MeV (per nucleus)
8.33354098 MeV (average binding energy per nucleon)Separation energy:S_N = 10.99(9) MeV (first neutron)
S_P = 2.515(29) MeV (first proton)Half-life:5.1(1) minDecay constant λ:0.002265186864575 s^-1Specific activity α:1.082640823218 × 10⁺¹⁹ Bq g^-1
292605627.89681 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2-)Year of discovery:1963

Radioactive Decay

Half-life T_½ = 5.1(1) min (minutes) respectively 3.06 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²⁷Ba	100 %	4.922(28) MeV

Parent Nuclides

Direct parent isotope is: ¹²⁷Ce.

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
^127mLa	14.2(4) keV	3.7(4) min	(3/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 70) and isobaric (same nucleon number A = 127) with Lanthanum-127. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 70	Isobar A = 127
39	¹⁰⁹Y
40	¹¹⁰Zr
41	¹¹¹Nb
42	¹¹²Mo
43	¹¹³Tc
44	¹¹⁴Ru
45	¹¹⁵Rh	¹²⁷Rh
46	¹¹⁶Pd	¹²⁷Pd
47	¹¹⁷Ag	¹²⁷Ag
48	¹¹⁸Cd	¹²⁷Cd
49	¹¹⁹In	¹²⁷In
50	¹²⁰Sn	¹²⁷Sn
51	¹²¹Sb	¹²⁷Sb
52	¹²²Te	¹²⁷Te
53	¹²³I	¹²⁷I
54	¹²⁴Xe	¹²⁷Xe
55	¹²⁵Cs	¹²⁷Cs
56	¹²⁶Ba	¹²⁷Ba
57	¹²⁷La	¹²⁷La
58	¹²⁸Ce	¹²⁷Ce
59	¹²⁹Pr	¹²⁷Pr
60	¹³⁰Nd	¹²⁷Nd
61	¹³¹Pm	¹²⁷Pm
62	¹³²Sm
63	¹³³Eu
64	¹³⁴Gd
65	¹³⁵Tb