Silicon-42

Properties and data of the isotope ⁴²Si.

Contents

Silicon-42 is a radioisotope of the chemical element silicon, which has 28 neutrons in its atomic nucleus in addition to the element-specific 14 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 42. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ⁴²Si is exclusively for academic purposes.

A report on the discovery of the radioactive nuclide appeared in 1990 [1]: According to this, silicon-42 was first observed and identified in the fragmentation reaction of calcium-48 ions of an energy of 44 MeV/u on a nickel-64 template.

See also: List of individual Silicon isotopes (and general data sources).

General data

Name of the isotope:Silicon-42; Si-42Symbol:⁴²Si or 4214SiMass number A:42 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:28Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):2 (= neutron-proton ratio)Neutron excess (N-Z):14Isotopic mass:42.01808(32) u (atomic weight of Silicon-42)Nuclide mass:42.0104 u (calculated nuclear mass without electrons)Mass excess:16.84141 MeVMass defect:0.334088096 u (per nucleus)Nuclear binding energy:311.2010569 MeV (per nucleus)
7.40954897 MeV (average binding energy per nucleon)Separation energy:S_N = 4.432(424) MeV (first neutron)
S_P = 25.04(50) MeV (first proton)Half-life:12.5(35) msDecay constant λ:55.451774444796 s^-1Specific activity α:7.950914205714 × 10⁺²³ Bq g^-1
21488957312741 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1990

Radioactive Decay

Half-life T_½ = 12.5(35) ms respectively 1.25 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy
β^-	⁴²P	100 %	15.75(32) MeV
β^-, n ?
β^-, 2n ?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 28) and isobaric (same nucleon number A = 42) with Silicon-42. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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

External data and identifiers

Adopted Levels, Gammas:NuDat 42Si

Literature and References

[1] - M. Lewitowicz, R. Anne, A. G. Artukh et al.:
First observation of the neutron-rich nuclei ⁴²Si, ^{45, 46}P, ⁴⁸S, and ⁵¹Cl from the interaction of 44 MeV/u ⁴⁸Ca + ⁶⁴Ni.
In: Zeitschrift für Physik A, 335, (1990), DOI 10.1007/BF01289359.

[2] - J. Fridmann, I. Wiedenhöver, A. Gade et al.:
Magic Nucleus ⁴²Si.
In: Nature, 435, 922 – 924, (2005), DOI 10.1038/nature03619.

[3] - A. Gade, B. A. Brown, J. A. Tostevin et al.:
Is the Structure of ⁴²Si Understood?.
In: Physical Review Letters, 122, 222501, (2019), DOI 10.1103/PhysRevLett.122.222501.