Erbium-161

Properties and data of the isotope ¹⁶¹Er.

Content

General data

Name of the isotope:Erbium-161; Er-161Symbol:¹⁶¹Er or 16168ErMass number A:161 (= number of nucleons)Atomic number Z:68 (= number of protons)Neutrons N:93Isotopic mass:160.930003(9) u (atomic weight of Erbium-161)Nuclide mass:160.8927029 u (calculated nuclear mass without electrons)Mass excess:-65.20179 MeVMass defect:1.407936364 u (per nucleus)Nuclear binding energy:1311.48427545 MeV (per nucleus)
8.14586506 MeV (average binding energy per nucleon)Separation energy:S_N = 7.209(26) MeV (first neutron)
S_P = 6.108(17) MeV (first proton)Half-life:3.21(3) hDecay constant λ:5.998158364139 × 10^-5 s^-1Specific activity α:2.257609660565 × 10⁺¹⁷ Bq g^-1
6101647.7312592 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Magnetic dipole moment:μ(μ_N) = - 0.365(3)Quadrupole moment Q:+ 1.361(14) barn (100 fm²)Nuclear g-factor:g_l = -0.24333333333333Year of discovery:1954

Radioactive Decay

Half-life T_½ = 3.21(3) h (hours) respectively 1.1556 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹⁶¹Ho	100 %	1.996(9) MeV

Parent Nuclides

Direct parent isotope is: ¹⁶¹Tm.

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
^161mEr	396.44(4) keV	7.5(7) μs	11/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 93) and isobaric (same nucleon number A = 161) with Erbium-161. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 93	Isobar A = 161
54	¹⁴⁷Xe
55	¹⁴⁸Cs
56	¹⁴⁹Ba
57	¹⁵⁰La
58	¹⁵¹Ce
59	¹⁵²Pr
60	¹⁵³Nd	¹⁶¹Nd
61	¹⁵⁴Pm	¹⁶¹Pm
62	¹⁵⁵Sm	¹⁶¹Sm
63	¹⁵⁶Eu	¹⁶¹Eu
64	¹⁵⁷Gd	¹⁶¹Gd
65	¹⁵⁸Tb	¹⁶¹Tb
66	¹⁵⁹Dy	¹⁶¹Dy
67	¹⁶⁰Ho	¹⁶¹Ho
68	¹⁶¹Er	¹⁶¹Er
69	¹⁶²Tm	¹⁶¹Tm
70	¹⁶³Yb	¹⁶¹Yb
71	¹⁶⁴Lu	¹⁶¹Lu
72	¹⁶⁵Hf	¹⁶¹Hf
73	¹⁶⁶Ta	¹⁶¹Ta
74	¹⁶⁷W	¹⁶¹W
75	¹⁶⁸Re	¹⁶¹Re
76	¹⁶⁹Os	¹⁶¹Os
77	¹⁷⁰Ir
78	¹⁷¹Pt
79	¹⁷²Au
80	¹⁷³Hg