Magnesium-40

Properties and data of the isotope ⁴⁰Mg.

Contents

Magnesium-40 is a radioisotope of the chemical element magnesium, which has 28 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 40. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ⁴⁰Mg is exclusively for academic purposes.

The first observation of the extremely neutron-rich nuclide during irradiation of a natural tungsten template with calcium-48 ions (141 MeV/nucleon) was reported in 2007 [1].

General data

Name of the isotope:Magnesium-40; Mg-40Symbol:⁴⁰Mg or 4012MgMass number A:40 (= number of nucleons)Atomic number Z:12 (= number of protons)Neutrons N:28Isotopic mass:40.053190(540) u (atomic weight of Magnesium-40)Nuclide mass:40.0466071 u (calculated nuclear mass without electrons)Mass excess:49.54617 MeVMass defect:0.283328032 u (per nucleus)Nuclear binding energy:263.91836184 MeV (per nucleus)
6.59795905 MeV (average binding energy per nucleon)Separation energy:S_N = 1.297(716) MeV (first neutron)
S_P = 2.7716(896) MeV (first proton)Half-life:> 170 nsDecay constant λ:4077336.356235 s^-1Specific activity α:6.138573467647 × 10⁺²⁸ Bq g^-1
1.659073910174 × 10⁺¹⁸ Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:2007

Radioactive Decay

Half-life T_½ = > 170 ns respectively 1.70 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy
β^- ?	⁴⁰Al	100 %	20.730(580) MeV
β^-, n	³⁹Al	?	19.989(583) MeV
β^-, 2n	³⁸Al	?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 28) and isobaric (same nucleon number A = 40) with Magnesium-40. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 28	Isobar A = 40
11	³⁹Na
12	⁴⁰Mg	⁴⁰Mg
13	⁴¹Al	⁴⁰Al
14	⁴²Si	⁴⁰Si
15	⁴³P	⁴⁰P
16	⁴⁴S	⁴⁰S
17	⁴⁵Cl	⁴⁰Cl
18	⁴⁶Ar	⁴⁰Ar
19	⁴⁷K	⁴⁰K
20	⁴⁸Ca	⁴⁰Ca
21	⁴⁹Sc	⁴⁰Sc
22	⁵⁰Ti	⁴⁰Ti
23	⁵¹V	⁴⁰V
24	⁵²Cr
25	⁵³Mn
26	⁵⁴Fe
27	⁵⁵Co
28	⁵⁶Ni
29	⁵⁷Cu
30	⁵⁸Zn
31	⁵⁹Ga
32	⁶⁰Ge

External data and identifiers

Adopted Levels, Gammas:NuDat 40Mg

Literature and References

[1] - T. Baumann, A. M. Amthor, D. Bazin et al.:
Discovery of ⁴⁰Mg and ⁴²Al suggests neutron drip-line slant towards heavier isotopes.
In: Nature, 449, (2007), DOI 10.1038/nature06213.

[2] - H. L. Crawford et al.:
First Spectroscopy of the Near Drip-line Nucleus ⁴⁰Mg.
In: Physical Review Letters, 122, 052501, (2019), DOI 10.1103/PhysRevLett.122.052501.