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Isotopes of silicon

Isotopes of silicon (14Si)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
28Si 92.2% stable
29Si 4.7% stable
30Si 3.1% stable
31Si trace 2.62 h β− 31P
32Si trace 153 y β− 32P
Standard atomic weight Ar°(Si)

Silicon (14Si) has 25 known isotopes, with mass numbers ranging from 22 to 46. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years (with decay energy 0.21 MeV), and it decays by beta emission to 32P (which has a 14.27-day half-life)[1] and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds.

A chart showing the relative abundances of the naturally occurring isotopes of silicon.

List of isotopes

Nuclide
[n 1] 		Z N Isotopic mass (Da)[4]
[n 2][n 3] 		Half-life[1]
[n 4] 		Decay
mode[1]
[n 5] 		Daughter
isotope
[n 6] 		Spin and
parity[1]
[n 7][n 4] 		Natural abundance (mole fraction)
Excitation energy Normal proportion[1] Range of variation
22Si 14 8 22.03611(54)# 28.7(11) ms β+, p (62%) 21Mg 0+
β+ (37%) 22Al
β+, 2p (0.7%) 20Na
23Si 14 9 23.02571(54)# 42.3(4) ms β+, p (88%) 22Mg 3/2+#
β+ (8%) 23Al
β+, 2p (3.6%) 21Na
24Si 14 10 24.011535(21) 143.2 (21) ms β+ (65.5%) 24Al 0+
β+, p (34.5%) 23Mg
25Si 14 11 25.004109(11) 220.6(10) ms β+ (65%) 25Al 5/2+
β+, p (35%) 24Mg
26Si 14 12 25.99233382(12) 2.2453(7) s β+ 26Al 0+
27Si 14 13 26.98670469(12) 4.117(14) s β+ 27Al 5/2+
28Si 14 14 27.97692653442(55) Stable 0+ 0.92223(19) 0.92205–0.92241
29Si 14 15 28.97649466434(60) Stable 1/2+ 0.04685(8) 0.04678–0.04692
30Si 14 16 29.973770137(23) Stable 0+ 0.03092(11) 0.03082–0.03102
31Si 14 17 30.975363196(46) 157.16(20) min β− 31P 3/2+
32Si 14 18 31.97415154(32) 157(7) y β− 32P 0+ trace cosmogenic
33Si 14 19 32.97797696(75) 6.18(18) s β− 33P 3/2+
34Si 14 20 33.97853805(86) 2.77(20) s β− 34P 0+
34mSi 4256.1(4) keV <210 ns IT 34Si (3−)
35Si 14 21 34.984550(38) 780(120) ms β− 35P 7/2−#
β−, n? 34P
36Si 14 22 35.986649(77) 503(2) ms β− (88%) 36P 0+
β−, n (12%) 35P
37Si 14 23 36.99295(12) 141.0(35) ms β− (83%) 37P (5/2−)
β−, n (17%) 36P
β−, 2n? 35P
38Si 14 24 37.99552(11) 63(8) ms β− (75%) 38P 0+
β−, n (25%) 37P
39Si 14 25 39.00249(15) 41.2(41) ms β− (67%) 39P (5/2−)
β−, n (33%) 38P
β−, 2n? 37P
40Si 14 26 40.00608(13) 31.2(26) ms β− (62%) 40P 0+
β−, n (38%) 39P
β−, 2n? 38P
41Si 14 27 41.01417(32)# 20.0(25) ms β−, n (>55%) 40P 7/2−#
β− (<45%) 41P
β−, 2n? 39P
42Si 14 28 42.01808(32)# 15.5(4 (stat), 16 (sys)) ms[5] β− (51%) 42P 0+
β−, n (48%) 41P
β−, 2n (1%) 40P
43Si 14 29 43.02612(43)# 13(4 (stat), 2 (sys)) ms[5] β−, n (52%) 42P 3/2−#
β− (27%) 43P
β−, 2n (21%) 41P
44Si 14 30 44.03147(54)# 4# ms [>360 ns] β−? 44P 0+
β−, n? 43P
β−, 2n? 42P
45Si[6] 14 31 45.03982(64)# 4# ms 3/2−#
46Si[6] 14 32
This table header & footer:
  1. ^ mSi – Excited nuclear isomer.
  2. ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. ^ Modes of decay:
    IT: Isomeric transition
    n: Neutron emission
    p: Proton emission
  6. ^ Bold symbol as daughter – Daughter product is stable.
  7. ^ ( ) spin value – Indicates spin with weak assignment arguments.

Silicon-28

Silicon-28, the most abundant isotope of silicon, is of particular interest in the construction of quantum computers when highly enriched, as the presence of 29Si in a sample of silicon contributes to quantum decoherence.[7] Extremely pure (>99.9998%) samples of 28Si can be produced through selective ionization and deposition of 28Si from silane gas.[8] Due to the extremely high purity that can be obtained in this manner, the Avogadro project sought to develop a new definition of the kilogram by making a 93.75 mm (3.691 in) sphere of the isotope and determining the exact number of atoms in the sample.[9][10]

Silicon-28 is produced in stars during the alpha process and the oxygen-burning process, and drives the silicon-burning process in massive stars shortly before they go supernova.[11][12]

Silicon-29

Silicon-29 is of note as the only stable silicon isotope with a nuclear spin (I = 1/2).[13] As such, it can be employed in nuclear magnetic resonance and hyperfine transition studies, for example to study the properties of the so-called A-center defect in pure silicon.[14]

Silicon-34

Silicon-34 is a radioactive isotope with a half-life of 2.8 seconds.[1] In addition to the usual N = 20 closed shell, the nucleus also shows a strong Z = 14 shell closure, making it behave like a doubly magic spherical nucleus, except that it is also located two protons above an island of inversion.[15] Silicon-34 has an unusual "bubble" structure where the proton distribution is less dense at the center than near the surface, as the 2s1/2 proton orbital is almost unoccupied in the ground state, unlike in 36S where it is almost full.[16][17] Silicon-34 is one of the known cluster decay emission particles; it is produced in the decay of 242Cm with a branching ratio of approximately 1×10−16.[18]

References

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  2. ^ "Standard Atomic Weights: Silicon". CIAAW. 2009.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
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  5. ^ a b Crawford, H. L.; Tripathi, V.; Allmond, J. M.; et al. (2022). "Crossing N = 28 toward the neutron drip line: first measurement of half-lives at FRIB". Physical Review Letters. 129 (212501): 212501. Bibcode:2022PhRvL.129u2501C. doi:10.1103/PhysRevLett.129.212501. PMID 36461950. S2CID 253600995.
  6. ^ a b Yoshimoto, Masahiro; Suzuki, Hiroshi; Fukuda, Naoki; Takeda, Hiroyuki; Shimizu, Yohei; Yanagisawa, Yoshiyuki; Sato, Hiromi; Kusaka, Kensuke; Ohtake, Masao; Yoshida, Koichi; Michimasa, Shin’ichiro (2024). "Discovery of Neutron-Rich Silicon Isotopes 45,46Si". Progress of Theoretical and Experimental Physics. 2024 (10). Oxford University Press (OUP). doi:10.1093/ptep/ptae155. ISSN 2050-3911.
  7. ^ "Beyond Six Nines: Ultra-enriched Silicon Paves the Road to Quantum Computing". NIST. 2014-08-11.
  8. ^ Dwyer, K J; Pomeroy, J M; Simons, D S; Steffens, K L; Lau, J W (2014-08-30). "Enriching 28 Si beyond 99.9998 % for semiconductor quantum computing". Journal of Physics D: Applied Physics. 47 (34): 345105. doi:10.1088/0022-3727/47/34/345105. ISSN 0022-3727.
  9. ^ Powell, Devin (1 July 2008). "Roundest Objects in the World Created". New Scientist. Retrieved 16 June 2015.
  10. ^ Keats, Jonathon. "The Search for a More Perfect Kilogram". Wired. Vol. 19, no. 10. Retrieved 16 December 2023.
  11. ^ Woosley, S.; Janka, T. (2006). "The physics of core collapse supernovae". Nature Physics. 1 (3): 147–154. arXiv:astro-ph/0601261. Bibcode:2005NatPh...1..147W. CiteSeerX 10.1.1.336.2176. doi:10.1038/nphys172. S2CID 118974639.
  12. ^ Narlikar, Jayant V. (1995). From Black Clouds to Black Holes. World Scientific. p. 94. ISBN 978-9810220334.
  13. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  14. ^ Watkins, G. D.; Corbett, J. W. (1961-02-15). "Defects in Irradiated Silicon. I. Electron Spin Resonance of the Si- A Center". Physical Review. 121 (4): 1001–1014. Bibcode:1961PhRv..121.1001W. doi:10.1103/PhysRev.121.1001. ISSN 0031-899X.
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  16. ^ "Physicists find atomic nucleus with a 'bubble' in the middle". 24 October 2016. Retrieved 26 December 2023.
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