Holmium-166

Properties and data of the isotope ¹⁶⁶Ho.

Content

Holmium-166 is a radioisotope of the chemical element Holmium, which, in addition to the element-specific 67 protons, has 99 neutrons in the atomic nucleus, resulting in the mass number 166.

General data

Name of the isotope:Holmium-166; Ho-166Symbol:¹⁶⁶Ho or 16667HoMass number A:166 (= number of nucleons)Atomic number Z:67 (= number of protons)Neutrons N:99Isotopic mass:165.9322901(11) u (atomic weight of Holmium-166)Nuclide mass:165.8955384 u (calculated nuclear mass without electrons)Mass excess:-63.07137 MeVMass defect:1.449813728 u (per nucleus)Nuclear binding energy:1350.49278875 MeV (per nucleus)
8.13549873 MeV (average binding energy per nucleon)Separation energy:S_N = 6.24364(2) MeV (first neutron)
S_P = 6.7477(8) MeV (first proton)Half-life:26.824(12) hDecay constant λ:7.177933324219 × 10^-6 s^-1Specific activity α:2.61978942798 × 10⁺¹⁶ Bq g^-1
708051.19675162 Ci g^-1Spin and parity:
(nuclear angular momentum)0-Year of discovery:1936

Radioactive Decay

Half-life T_½ = 26.824(12) h (hours) respectively 9.65664 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹⁶⁶Er	100 %	1.8547(9) MeV

Parent Nuclides

Direct parent isotope is: ¹⁶⁶Dy.

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
^166mHo	5.969(12) keV	1200(180) a	7-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 99) and isobaric (same nucleon number A = 166) with Holmium-166. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 99	Isobar A = 166
57	¹⁵⁶La
58	¹⁵⁷Ce
59	¹⁵⁸Pr
60	¹⁵⁹Nd
61	¹⁶⁰Pm
62	¹⁶¹Sm	¹⁶⁶Sm
63	¹⁶²Eu	¹⁶⁶Eu
64	¹⁶³Gd	¹⁶⁶Gd
65	¹⁶⁴Tb	¹⁶⁶Tb
66	¹⁶⁵Dy	¹⁶⁶Dy
67	¹⁶⁶Ho	¹⁶⁶Ho
68	¹⁶⁷Er	¹⁶⁶Er
69	¹⁶⁸Tm	¹⁶⁶Tm
70	¹⁶⁹Yb	¹⁶⁶Yb
71	¹⁷⁰Lu	¹⁶⁶Lu
72	¹⁷¹Hf	¹⁶⁶Hf
73	¹⁷²Ta	¹⁶⁶Ta
74	¹⁷³W	¹⁶⁶W
75	¹⁷⁴Re	¹⁶⁶Re
76	¹⁷⁵Os	¹⁶⁶Os
77	¹⁷⁶Ir	¹⁶⁶Ir
78	¹⁷⁷Pt	¹⁶⁶Pt
79	¹⁷⁸Au
80	¹⁷⁹Hg
81	¹⁸⁰Tl
82	¹⁸¹Pb

External data and identifiers

CAS:13967-65-2InChI Key:KJZYNXUDTRRSPN-OUBTZVSYSA-NSMILES:[166Ho]PubChem:ID 161007Adopted Levels, Gammas:NuDat 166Ho

Literature and References

[1] - Nienke J. M. Klaassen, Mark J. Arntz, Alexandra Gil Arranja et al.:
The various therapeutic applications of the medical isotope holmium-166: a narrative review.
In: EJNMMI Radiopharmacy and Chemistry, (2019), DOI 10.1186/s41181-019-0066-3.

[2] - Martina Stella et al.:
Holmium-166 Radioembolization: Current Status and Future Prospective.
In: CardioVascular and Interventional Radiology, (2022), DOI 10.1007/s00270-022-03187-y.