Lanthanum-155

Properties and data of the isotope ¹⁵⁵La.

Content

General data

Name of the isotope:Lanthanum-155; La-155Symbol:¹⁵⁵La or 15557LaMass number A:155 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:98Isotopic mass:154.95928(43) u (atomic weight of Lanthanum-155)Nuclide mass:154.9280131 u (calculated nuclear mass without electrons)Mass excess:-37.93044 MeVMass defect:1.335908592 u (per nucleus)Nuclear binding energy:1244.390838 MeV (per nucleus)
8.02832799 MeV (average binding energy per nucleon)Separation energy:S_N = 4.47(59) MeV (first neutron)
S_P = 12.40(64) MeV (first proton)Half-life:101(28) msDecay constant λ:6.8628433718806 s^-1Specific activity α:2.6837019146 × 10⁺²² Bq g^-1
725324841789.19 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Year of discovery:2016

Radioactive Decay

Half-life T_½ = 101(28) ms respectively 1.01 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁵⁵Ce	100 %	9.85(50) MeV
β^-, n	¹⁵⁴Ce	?	6.22(45) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 98) and isobaric (same nucleon number A = 155) with Lanthanum-155. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 98	Isobar A = 155
57	¹⁵⁵La	¹⁵⁵La
58	¹⁵⁶Ce	¹⁵⁵Ce
59	¹⁵⁷Pr	¹⁵⁵Pr
60	¹⁵⁸Nd	¹⁵⁵Nd
61	¹⁵⁹Pm	¹⁵⁵Pm
62	¹⁶⁰Sm	¹⁵⁵Sm
63	¹⁶¹Eu	¹⁵⁵Eu
64	¹⁶²Gd	¹⁵⁵Gd
65	¹⁶³Tb	¹⁵⁵Tb
66	¹⁶⁴Dy	¹⁵⁵Dy
67	¹⁶⁵Ho	¹⁵⁵Ho
68	¹⁶⁶Er	¹⁵⁵Er
69	¹⁶⁷Tm	¹⁵⁵Tm
70	¹⁶⁸Yb	¹⁵⁵Yb
71	¹⁶⁹Lu	¹⁵⁵Lu
72	¹⁷⁰Hf	¹⁵⁵Hf
73	¹⁷¹Ta	¹⁵⁵Ta
74	¹⁷²W
75	¹⁷³Re
76	¹⁷⁴Os
77	¹⁷⁵Ir
78	¹⁷⁶Pt
79	¹⁷⁷Au
80	¹⁷⁸Hg
81	¹⁷⁹Tl
82	¹⁸⁰Pb

External data and identifiers

Adopted Levels, Gammas:NuDat 155La

Literature and References

[1] - M. Thoennessen:
2017 Update of the discoveries of nuclides.
In: International Journal of Modern Physics E, (2018), DOI 10.1142/S0218301318300023.