Erbium-155

Properties and data of the isotope ¹⁵⁵Er.

Content

General data

Name of the isotope:Erbium-155; Er-155Symbol:¹⁵⁵Er or 15568ErMass number A:155 (= number of nucleons)Atomic number Z:68 (= number of protons)Neutrons N:87Isotopic mass:154.933216(7) u (atomic weight of Erbium-155)Nuclide mass:154.8959159 u (calculated nuclear mass without electrons)Mass excess:-62.2089 MeVMass defect:1.352733868 u (per nucleus)Nuclear binding energy:1260.06348164 MeV (per nucleus)
8.12944182 MeV (average binding energy per nucleon)Separation energy:S_N = 7.675(8) MeV (first neutron)
S_P = 4.859(10) MeV (first proton)Half-life:5.3(3) minDecay constant λ:0.0021797081149684 s^-1Specific activity α:8.523707338887 × 10⁺¹⁸ Bq g^-1
230370468.61858 Ci g^-1Spin and parity:
(nuclear angular momentum)7/2-Magnetic dipole moment:μ(μ_N) = - 0.669(4)Quadrupole moment Q:- 0.27(2) barn (100 fm²)Nuclear g-factor:g_l = -0.19114285714286Year of discovery:1969

Radioactive Decay

Half-life T_½ = 5.3(3) min (minutes) respectively 3.18 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹⁵⁵Ho	99.978(7) %	3.830(18) MeV
α	¹⁵¹Dy	0.022(7) %	4.118(5) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁵Tm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 87) and isobaric (same nucleon number A = 155) with Erbium-155. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 87	Isobar A = 155
49	¹³⁶In
50	¹³⁷Sn
51	¹³⁸Sb
52	¹³⁹Te
53	¹⁴⁰I
54	¹⁴¹Xe
55	¹⁴²Cs
56	¹⁴³Ba
57	¹⁴⁴La	¹⁵⁵La
58	¹⁴⁵Ce	¹⁵⁵Ce
59	¹⁴⁶Pr	¹⁵⁵Pr
60	¹⁴⁷Nd	¹⁵⁵Nd
61	¹⁴⁸Pm	¹⁵⁵Pm
62	¹⁴⁹Sm	¹⁵⁵Sm
63	¹⁵⁰Eu	¹⁵⁵Eu
64	¹⁵¹Gd	¹⁵⁵Gd
65	¹⁵²Tb	¹⁵⁵Tb
66	¹⁵³Dy	¹⁵⁵Dy
67	¹⁵⁴Ho	¹⁵⁵Ho
68	¹⁵⁵Er	¹⁵⁵Er
69	¹⁵⁶Tm	¹⁵⁵Tm
70	¹⁵⁷Yb	¹⁵⁵Yb
71	¹⁵⁸Lu	¹⁵⁵Lu
72	¹⁵⁹Hf	¹⁵⁵Hf
73	¹⁶⁰Ta	¹⁵⁵Ta
74	¹⁶¹W
75	¹⁶²Re
76	¹⁶³Os
77	¹⁶⁴Ir