Magnesium-31

Properties and data of the isotope ³¹Mg.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Magnesium-31 is a radioisotope of the chemical element magnesium, which has 19 neutrons in its atomic nucleus in addition to the element-specific 12 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 31. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ³¹Mg is exclusively for academic purposes.

The first observation and identification of the neutron-rich isotope was reported in 1977: According to this, ³¹Mg was produced in the spallation reaction of 800 MeV protons on a uranium target [1].

General data

Name of the isotope:Magnesium-31; Mg-31Symbol:³¹Mg or 3112MgMass number A:31 (= number of nucleons)Atomic number Z:12 (= number of protons)Neutrons N:19Isotopic mass:30.996648(3) u (atomic weight of Magnesium-31)Nuclide mass:30.9900651 u (calculated nuclear mass without electrons)Mass excess:-3.12237 MeVMass defect:0.261885788 u (per nucleus)Nuclear binding energy:243.94504021 MeV (per nucleus)
7.86919485 MeV (average binding energy per nucleon)Separation energy:S_N = 2.312(3) MeV (first neutron)
S_P = 18.886(6) MeV (first proton)Half-life:270(2) msDecay constant λ:2.9370643244065 s^-1Specific activity α:5.895805025423 × 10⁺²² Bq g^-1
1593460817682.1 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2+Magnetic dipole moment:μ(μ_N) = - 0.88340(15)Nuclear g-factor:g_l = -1.7668Year of discovery:1977

Radioactive Decay

Half-life T_½ = 270(2) ms respectively 2.36 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	³¹Al	93.8 %	11.829(4) MeV
β^-, n	³⁰Al	6.2(19) %	4.671(4) MeV

Parent Nuclides

Direct parent isotopes are: ³¹Na, ³²Na, ³³Na.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 19) and isobaric (same nucleon number A = 31) with Magnesium-31. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 19	Isobar A = 31
8	²⁷O
9	²⁸F	³¹F
10	²⁹Ne	³¹Ne
11	³⁰Na	³¹Na
12	³¹Mg	³¹Mg
13	³²Al	³¹Al
14	³³Si	³¹Si
15	³⁴P	³¹P
16	³⁵S	³¹S
17	³⁶Cl	³¹Cl
18	³⁷Ar	³¹Ar
19	³⁸K
20	³⁹Ca
21	⁴⁰Sc
22	⁴¹Ti
23	⁴²V
24	⁴³Cr
25	⁴⁴Mn
26	⁴⁵Fe
27	⁴⁶Co

External data and identifiers

Adopted Levels, Gammas:NuDat 31Mg

Literature and References

[1] - G. W. Butler, D. G. Perry, L. P. Remsberg et al.:
Observation of the New Nuclides ²⁷Ne, ³¹Mg, ³²Mg, ³⁴Al, and ³⁹P.
In: Physical Review Letters, 38, 1380, (1977), DOI 10.1103/PhysRevLett.38.1380.

[2] - H. Nishibata et al.:
Shape Coexistence ³¹Mg Revealed by β-γ and β-n-γ Spectroscopy with Spin-Polarized ³¹Na.
In: Exotic Nuclei, (2019), DOI 10.1142/9789811209451_0014.