Zirconium-91m
Properties and data of the isotope 91mZr.
Zirconium-91m is an excited nuclear state of the nuclide 91Zr, characterized by a defined excitation energy of 3167.3 keV. Its spin and parity quantum numbers differ from those of the ground state (gs). Simultaneously, this metastable nuclear isomer possesses an independent, experimentally measurable lifetime: decay occurs via an isomeric transition to Zr-91 in the ground state with a half-life of approximately 4.35 microseconds.
See also: List of individual Zirconium isotopes (and general data sources).
General data
Name of the isotope:Zirconium-91m; Zr-91mSymbol:91mZr or 91m40ZrMass number A:91 (= number of nucleons)Atomic number Z:40 (= number of protons)Neutrons N:51Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.275 (= neutron-proton ratio)Neutron excess (N-Z):11Excitation energy:3167.3(4) keVIsotopic mass:90.90564021(10) u (atomic weight of Zirconium-91m)Nuclide mass:90.883698 u (calculated nuclear mass without electrons)Mass excess:-87.89558 MeVMass defect:0.849271786 u (per nucleus)Nuclear binding energy:791.09157303 MeV (per nucleus)
8.69331399 MeV (average binding energy per nucleon)Half-life:4.35(14) μsDecay constant λ:159344.17943907 s-1Specific activity α:1.06621454865 × 10+27 Bq g-1
2.881660942321 × 10+16 Ci g-1Spin and parity:
(nuclear angular momentum)(21/2+)Magnetic dipole moment:μ(μN) = +9.82(8)Quadrupole moment Q:-0.86(5) barn (100 fm2)Nuclear g-factor:gl = 0.9352380952381Year of discovery:1985
Radioactive Decay
Half-life T½ = 4.35(14) μs respectively 4.35 × 10-6 seconds s.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| Iso | 91Zr | 100 % | | |
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 |
|---|
| 91Zr | | stable | 5/2+ |
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 51) and isobaric (same nucleon number A = 91) with Zirconium-91m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 51 | Isobar A = 91 |
|---|
| 28 | 79Ni | |
| 29 | 80Cu | |
| 30 | 81Zn | |
| 31 | 82Ga | |
| 32 | 83Ge | |
| 33 | 84As | 91As |
| 34 | 85Se | 91Se |
| 35 | 86Br | 91Br |
| 36 | 87Kr | 91Kr |
| 37 | 88Rb | 91Rb |
| 38 | 89Sr | 91Sr |
| 39 | 90Y | 91Y |
| 40 | 91Zr | 91Zr |
| 41 | 92Nb | 91Nb |
| 42 | 93Mo | 91Mo |
| 43 | 94Tc | 91Tc |
| 44 | 95Ru | 91Ru |
| 45 | 96Rh | 91Rh |
| 46 | 97Pd | 91Pd |
| 47 | 98Ag | |
| 48 | 99Cd | |
| 49 | 100In | |
| 50 | 101Sn | |
Last update: 2026-01-26
Perma link: https://www.chemlin.org/isotope/zirconium-91m
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