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Isotopes of boron

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Isotopes of boron (5B)
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
8B synth 771.9 ms β+ 8Be
10B 19.6% stable
11B 80.3% stable
Standard atomic weight Ar°(B)

Boron (5B) naturally occurs as isotopes 10
B
 and 11
B
, the latter of which makes up about 80% of natural boron. There are 13 radioisotopes that have been discovered, with mass numbers from 7 to 21, all with short half-lives, the longest being that of 8
B
, with a half-life of only 771.9(9) ms and 12
B
 with a half-life of 20.20(2) ms. All other isotopes have half-lives shorter than 17.35 ms. Those isotopes with mass below 10 decay into helium (via short-lived isotopes of beryllium for 7
B
 and 9
B
) while those with mass above 11 mostly become carbon.

A chart showing the abundances of the naturally occurring isotopes of boron.

List of isotopes

Nuclide
[n 1] 		Z N Isotopic mass (Da)[3]
[n 2][n 3] 		Half-life[4]

[resonance width] 		Decay
mode[4]
[n 4] 		Daughter
isotope
[n 5] 		Spin and
parity[4]
[n 6][n 7] 		Natural abundance (mole fraction)
Excitation energy Normal proportion[4] Range of variation
6
B
?[n 8] 		5  1 6.050800(2150) p-unstable 2p? 4
Li
? 		2−#
7
B
 		5  2 7.029712(27) 570(14) ys
[801(20) keV] 		p 6
Be
[n 9] 		(3/2−)
8
B
[n 10][n 11] 		5  3 8.0246073(11) 771.9(9) ms β+α 4
He
 		2+
8m
B
 		10624(8) keV 0+
9
B
 		5  4 9.0133296(10) 800(300) zs p 8
Be
[n 12] 		3/2−
10
B
[n 13] 		5  5 10.012936862(16) Stable 3+ [0.189, 0.204][5]
11
B
 		5  6 11.009305167(13) Stable 3/2− [0.796, 0.811][5]
11m
B
 		12560(9) keV 1/2+, (3/2+)
12
B
 		5  7 12.0143526(14) 20.20(2) ms β− (99.40(2)%) 12
C
 		1+
β−α (0.60(2)%) 8
Be
[n 14]
13
B
 		5  8 13.0177800(11) 17.16(18) ms β− (99.734(36)%) 13
C
 		3/2−
β−n (0.266(36)%) 12
C
14
B
 		5  9 14.025404(23) 12.36(29) ms β− (93.96(23)%) 14
C
 		2−
β−n (6.04(23)%) 13
C
β−2n ?[n 15] 12
C
 ?
14m
B
 		17065(29) keV 4.15(1.90) zs IT ?[n 15] 0+
15
B
 		5 10 15.031087(23) 10.18(35) ms β−n (98.7(1.0)%) 14
C
 		3/2−
β− (< 1.3%) 15
C
β−2n (< 1.5%) 13
C
16
B
 		5 11 16.039841(26) > 4.6 zs n ?[n 15] 15
B
 ? 		0−
17
B
[n 16] 		5 12 17.04693(22) 5.08(5) ms β−n (63(1)%) 16
C
 		(3/2−)
β− (21.1(2.4)%) 17
C
β−2n (12(2)%) 15
C
β−3n (3.5(7)%) 14
C
β−4n (0.4(3)%) 13
C
18
B
 		5 13 18.05560(22) < 26 ns n 17
B
 		(2−)
19
B
[n 16] 		5 14 19.06417(56) 2.92(13) ms β−n (71(9)%) 18
C
 		(3/2−)
β−2n (17(5)%) 17
C
β−3n (< 9.1%) 16
C
β− (> 2.9%) 19
C
20
B
[6] 		5 15 20.07451(59) > 912.4 ys n 19
B
 		(1−, 2−)
21
B
[6] 		5 16 21.08415(60) > 760 ys 2n 19
B
 		(3/2−)
This table header & footer:
  1. ^ mB – 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. ^ Modes of decay:
    n: Neutron emission
    p: Proton emission
  5. ^ Bold symbol as daughter – Daughter product is stable.
  6. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  7. ^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  8. ^ This isotope has not yet been observed; given data is inferred or estimated from periodic trends.
  9. ^ Subsequently decays by double proton emission to 4
    He
     for a net reaction of 7
    B
     → 4
    He
     + 3 1
    H
  10. ^ Has 1 halo proton
  11. ^ Intermediate product of a branch of proton-proton chain in stellar nucleosynthesis as part of the process converting hydrogen to helium
  12. ^ Immediately decays into two α particles, for a net reaction of 9
    B
     → 2 4
    He
     + 1
    H
  13. ^ One of the few stable odd-odd nuclei
  14. ^ Immediately decays into two α particles, for a net reaction of 12
    B
     → 3 4
    He
     +  e−
  15. ^ a b c Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.
  16. ^ a b Has 2 halo neutrons

Boron-8

Boron-8 is an isotope of boron that undergoes β+ decay to beryllium-8 with a half-life of 771.9(9) ms. It is the strongest candidate for a halo nucleus with a loosely-bound proton, in contrast to neutron halo nuclei such as lithium-11.[7]

Although neutrinos from boron-8 beta decays within the Sun make up only about 80 ppm of the total solar neutrino flux, they have a higher energy centered around 10 MeV,[8] and are an important background to dark matter direct detection experiments.[9] They are the first component of the neutrino floor that dark matter direct detection experiments are expected to eventually encounter.

Applications

Boron-10

Boron-10 is used in boron neutron capture therapy as an experimental treatment of some brain cancers.

References

  1. ^ "Standard Atomic Weights: Boron". CIAAW. 2009.
  2. ^ 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.
  3. ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  4. ^ a b c d Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  5. ^ a b "Atomic Weight of Boron". CIAAW.
  6. ^ a b Leblond, S.; et al. (2018). "First observation of 20B and 21B". Physical Review Letters. 121 (26): 262502–1–262502–6. arXiv:1901.00455. doi:10.1103/PhysRevLett.121.262502. PMID 30636115. S2CID 58602601.
  7. ^ Maaß, Bernhard; Müller, Peter; Nörtershäuser, Wilfried; Clark, Jason; Gorges, Christian; Kaufmann, Simon; König, Kristian; Krämer, Jörg; Levand, Anthony; Orford, Rodney; Sánchez, Rodolfo; Savard, Guy; Sommer, Felix (November 2017). "Towards laser spectroscopy of the proton-halo candidate boron-8". Hyperfine Interactions. 238 (1): 25. Bibcode:2017HyInt.238...25M. doi:10.1007/s10751-017-1399-5. S2CID 254551036.
  8. ^ Bellerive, A. (2004). "Review of solar neutrino experiments". International Journal of Modern Physics A. 19 (8): 1167–1179. arXiv:hep-ex/0312045. Bibcode:2004IJMPA..19.1167B. doi:10.1142/S0217751X04019093. S2CID 16980300.
  9. ^ Cerdeno, David G.; Fairbairn, Malcolm; Jubb, Thomas; Machado, Pedro; Vincent, Aaron C.; Boehm, Celine (2016). "Physics from solar neutrinos in dark matter direct detection experiments". JHEP. 2016 (5): 118. arXiv:1604.01025. Bibcode:2016JHEP...05..118C. doi:10.1007/JHEP05(2016)118. S2CID 55112052.


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