Xenon-127m

Properties and data of the isotope ¹²⁷Xe.

Content

General data

Name of the isotope:Xenon-127m; Xe-127mSymbol:¹²⁷Xe or 12754XeMass number A:127 (= number of nucleons)Atomic number Z:54 (= number of protons)Neutrons N:73Isotopic mass:126.905184(4) u (atomic weight of Xenon-127m)
Excitation energy: 297.10(8) keVNuclide mass:126.8755626 u (calculated nuclear mass without electrons)Mass excess:-88.32054 MeVMass defect:1.149906596 u (per nucleus)Nuclear binding energy:1071.13109473 MeV (per nucleus)
8.43410311 MeV (average binding energy per nucleon)Half-life:69.2(9) sDecay constant λ:0.010016577753756 s^-1Specific activity α:4.787400172034 × 10⁺¹⁹ Bq g^-1
1293891938.3876 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Magnetic dipole moment:μ(μ_N) = -0.8844(10)Nuclear g-factor:g_l = -0.19653333333333

Radioactive Decay

Half-life T_½ = 69.2(9) s respectively 6.92 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹²⁷Xe	100 %	0.2971(8) MeV	0.1246(3) MeV [69(3) %] 0.1725(3) MeV [38(3) %]

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
¹²⁷Xe		36.346(3) d	1/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 73) and isobaric (same nucleon number A = 127) with Xenon-127m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 73	Isobar A = 127
41	¹¹⁴Nb
42	¹¹⁵Mo
43	¹¹⁶Tc
44	¹¹⁷Ru
45	¹¹⁸Rh	¹²⁷Rh
46	¹¹⁹Pd	¹²⁷Pd
47	¹²⁰Ag	¹²⁷Ag
48	¹²¹Cd	¹²⁷Cd
49	¹²²In	¹²⁷In
50	¹²³Sn	¹²⁷Sn
51	¹²⁴Sb	¹²⁷Sb
52	¹²⁵Te	¹²⁷Te
53	¹²⁶I	¹²⁷I
54	¹²⁷Xe	¹²⁷Xe
55	¹²⁸Cs	¹²⁷Cs
56	¹²⁹Ba	¹²⁷Ba
57	¹³⁰La	¹²⁷La
58	¹³¹Ce	¹²⁷Ce
59	¹³²Pr	¹²⁷Pr
60	¹³³Nd	¹²⁷Nd
61	¹³⁴Pm	¹²⁷Pm
62	¹³⁵Sm
63	¹³⁶Eu
64	¹³⁷Gd
65	¹³⁸Tb
66	¹³⁹Dy
67	¹⁴⁰Ho