Boron-8

Properties and data of the isotope ⁸B.

Content

Boron-8 is a radioisotope of the chemical element boron, which, in addition to the element-specific 5 protons, has 3 neutrons in the atomic nucleus, resulting in the mass number 8. The very short-lived, unstable and therefore radioactive nuclide, which can only be produced artificially, has no practical significance; The study of ⁸B serves exclusively academic purposes.

The ⁸B nucleus is of great interest for astrophysics, for example, as it is the main source of solar neutrinos with energies above 2 MeV; The β⁺/EE decay α spectrum occurring for this nuclide has been studied in detail on numerous occasions [2].

General data

Name of the isotope:Boron-8; B-8Symbol:⁸B or 85BMass number A:8 (= number of nucleons)Atomic number Z:5 (= number of protons)Neutrons N:3Isotopic mass:8.0246073(11) u (atomic weight of Boron-8)Nuclide mass:8.0218644 u (calculated nuclear mass without electrons)Mass excess:22.92155 MeVMass defect:0.040512608 u (per nucleus)Nuclear binding energy:37.73725128 MeV (per nucleus)
4.71715641 MeV (average binding energy per nucleon)Separation energy:S_N = 12.826(25) MeV (first neutron)
S_P = 0.1364(10) MeV (first proton)Half-life:771.17(94) msDecay constant λ:0.89882539590485 s^-1Specific activity α:6.766066428284 × 10⁺²² Bq g^-1
1828666602239 Ci g^-1Spin and parity:
(nuclear angular momentum)2+Isobaric spin: 1Magnetic dipole moment:μ(μ_N) = 1.0355(3)Quadrupole moment Q:+0.0643(14) barn (100 fm²)Nuclear g-factor:g_l = 0.51775Mirror nucleus:Lithium-8Year of discovery:1950

Radioactive Decay

A newer and more precise value for the half-life was published in 2020 and adopted here [3]. The older value of T_1/2 = 0.770(3) s can be found in the relevant literature.

Half-life T_½ = 771.17(94) ms respectively 7.7117 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE β⁺	⁸Be	100 %	17.9798(10) MeV
β⁺, α	⁴He

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 3) and isobaric (same nucleon number A = 8) with Boron-8. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 3	Isobar A = 8
1	⁴H
2	⁵He	⁸He
3	⁶Li	⁸Li
4	⁷Be	⁸Be
5	⁸B	⁸B
6	⁹C	⁸C
7	¹⁰N
8	¹¹O

External data and identifiers

Adopted Levels, Gammas:NuDat 8B

Literature and References

[1] - G. A. Korolev, A. V. Dobrovolsky, A. G. Inglessi et al.:
Halo structure of ⁸B determined from intermediate energy proton elastic scattering in inverse kinematics.
In: Physics Letters B, 780, 200-204, (2018), DOI 10.1016/j.physletb.2018.03.013.

[2] - S. Viñals et al.:
The experiments to determine the electron capture and β-decay of ⁸B into the highly excited states of ⁸Be.
In: Journal of Physics: Conference Series, 1643, 012130, (2020), DOI 10.1088/1742-6596/1643/1/012130.

[3] - S. Viñals et al.:
The Most Accurate Determination of the ⁸B Half-life.
In: Acta Physica Polonica B, 51, 3, (2020), DOI 10.5506/APhysPolB.51.717.