Antimony-129m2

Properties and data of the isotope ¹²⁹Sb.

Content

General data

Name of the isotope:Antimony-129m2; Sb-129m2Symbol:¹²⁹Sb or 12951SbMass number A:129 (= number of nucleons)Atomic number Z:51 (= number of protons)Neutrons N:78Isotopic mass:128.909147(23) u (atomic weight of Antimony-129m2)
Excitation energy: 1861.06(5) keVNuclide mass:128.8811711 u (calculated nuclear mass without electrons)Mass excess:-84.62902 MeVMass defect:1.16579308 u (per nucleus)Nuclear binding energy:1085.92925926 MeV (per nucleus)
8.41805627 MeV (average binding energy per nucleon)Half-life:2.2(2) μsDecay constant λ:315066.90025452 s^-1Specific activity α:1.482325979403 × 10⁺²⁷ Bq g^-1
4.0062864308 × 10⁺¹⁶ Ci g^-1Spin and parity:
(nuclear angular momentum)(15/2-)

Radioactive Decay

Half-life T_½ = 2.2(2) μs respectively 2.2 × 10^-6 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹²⁹Sb

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
¹²⁹Sb		4.366(26) h	7/2+
^129m1Sb	1851.31(6) keV	17.7(1) min	(19/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 78) and isobaric (same nucleon number A = 129) with Antimony-129m2. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 78	Isobar A = 129
43	¹²¹Tc
44	¹²²Ru
45	¹²³Rh
46	¹²⁴Pd	¹²⁹Pd
47	¹²⁵Ag	¹²⁹Ag
48	¹²⁶Cd	¹²⁹Cd
49	¹²⁷In	¹²⁹In
50	¹²⁸Sn	¹²⁹Sn
51	¹²⁹Sb	¹²⁹Sb
52	¹³⁰Te	¹²⁹Te
53	¹³¹I	¹²⁹I
54	¹³²Xe	¹²⁹Xe
55	¹³³Cs	¹²⁹Cs
56	¹³⁴Ba	¹²⁹Ba
57	¹³⁵La	¹²⁹La
58	¹³⁶Ce	¹²⁹Ce
59	¹³⁷Pr	¹²⁹Pr
60	¹³⁸Nd	¹²⁹Nd
61	¹³⁹Pm	¹²⁹Pm
62	¹⁴⁰Sm	¹²⁹Sm
63	¹⁴¹Eu
64	¹⁴²Gd
65	¹⁴³Tb
66	¹⁴⁴Dy
67	¹⁴⁵Ho
68	¹⁴⁶Er
69	¹⁴⁷Tm
70	¹⁴⁸Yb
71	¹⁴⁹Lu