Isotopes of boron

Isotopes of boron (5B)
Main isotopes Decay
Isotope abun­dance half-life (t1/2) mode pro­duct
8B synth 771.9 ms β+ 8Be
10B [18.9%, 20.4%] stable
11B [79.6%, 81.1%] stable
Standard atomic weight Ar°(B)
  • [10.806, 10.821]
  • 10.81±0.02 (abridged)

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 while those with mass above 11 mostly become carbon.

List of isotopes

Nuclide
 Z N Isotopic mass (Da)
 Discovery
year		 Half-life

[resonance width]		 Decay
mode
 Daughter
isotope
 Spin and
parity
 Natural abundance (mole fraction)
Normal proportion Range of variation
7
B		 5  2 7.029712(27) 1967 570(14) ys
[801(20) keV]		 p 6
Be		 (3/2−)
8
B		 5  3 8.0246073(11) 1950 771.9(9) ms β+ 8
Be		 2+
9
B		 5  4 9.0133296(10) 1940 800(300) zs p 8
Be		 3/2−
10
B		 5  5 10.012936862(16) 1920 Stable 3+ [0.189, 0.204]
11
B		 5  6 11.009305167(13) 1920 Stable 3/2− [0.796, 0.811]
12
B		 5  7 12.0143526(14) 1935 20.20(2) ms β− (99.40(2)%) 12
C		 1+
β−α (0.60(2)%) 8
Be
13
B		 5  8 13.0177800(11) 1956 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) 1966 12.36(29) ms β− (93.96(23)%) 14
C		 2−
β−n (6.04(23)%) 13
C
β−2n ? 12
C
15
B		 5 10 15.031087(23) 1966 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) 2000 > 4.6 zs n ? 15
B		 0−
17
B		 5 12 17.04693(22) 1973 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) 2010 < 26 ns n 17
B		 (2−)
19
B		 5 14 19.06417(56) 1984 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		 5 15 20.07451(59) 2018 > 912.4 ys n 19
B		 (1−, 2−)
21
B		 5 16 21.08415(60) 2018 > 760 ys 2n 19
B		 (3/2−)
This table header & footer:
  1. ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  2. ↑ Modes of decay:
    n:Neutron emission
    p:Proton emission
  3. ↑ Bold symbol as daughter – Daughter product is stable.
  4. ↑ ( ) spin value – Indicates spin with weak assignment arguments.
  5. ↑ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  6. ↑ Subsequently decays by double proton emission to 4
    He     for a net reaction of 7
    B     → 4
    He     + 3 1
    H
  7. ↑ Has 1 halo proton
  8. ↑ Intermediate product of a branch of proton–proton chain in stellar nucleosynthesis as part of the process converting hydrogen to helium
  9. ↑ Immediately decays into two α particles, for a net reaction of 8
    B     → 2 4
    He     + e+
  10. ↑ Immediately decays into two α particles, for a net reaction of 9
    B     → 2 4
    He     + 1
    H
  11. ↑ One of the few stable odd-odd nuclei
  12. ↑ Immediately decays into two α particles, for a net reaction of 12
    B     → 3 4
    He     +  e−
  13. 1 2 Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.
  14. ↑ Has 2 halo neutrons
  15. ↑ Has 4 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.

Although boron-8 beta decay neutrinos from the Sun make up only about 80 ppm of the total solar neutrino flux, they have a higher energy centered around 10 MeV, and are an important background to dark matter direct detection experiments. 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.

See also

Daughter products other than boron

References

  1. 1 2 3 4 5 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.
  2. ↑ "Standard Atomic Weights: Boron". 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.
  4. ↑ 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.
  5. ↑ FRIB Nuclear Data Group. "Discovery of Nuclides Project, Isotope Database". doi:10.11578/frib/2279152.
  6. 1 2 "Atomic Weight of Boron". CIAAW.
  7. 1 2 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.
  8. ↑ 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.
  9. ↑ 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.
  10. ↑ 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.