Boron-9

Properties and data of the isotope ⁹B.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Boron-9 is a radioisotope of the chemical element boron, which, in addition to the element-specific 5 protons, has 4 neutrons in the atomic nucleus, resulting in the mass number 9. The very short-lived, unstable and therefore radioactive nuclide, which can only be produced artificially, has no practical significance; The study of ⁹B is exclusively for academic purposes. The first evidence for the existence of the nuclide dates back to 1940 [1].

The half-life of the nuclide is in the range of a few zeptoseconds (zs). A certain role of ⁹B in stellar and Big Bang nucleosynthesis is discussed [3].

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

General data

Name of the isotope:Boron-9; B-9Symbol:⁹B or 95BMass number A:9 (= number of nucleons)Atomic number Z:5 (= number of protons)Neutrons N:4Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):0.8 (= neutron-proton ratio)Neutron excess (N-Z):-1Isotopic mass:9.0133296(10) u (atomic weight of Boron-9)Nuclide mass:9.0105867 u (calculated nuclear mass without electrons)Mass excess:12.41644 MeVMass defect:0.060455224 u (per nucleus)Nuclear binding energy:56.31367842 MeV (per nucleus)
6.25707538 MeV (average binding energy per nucleon)Separation energy:S_N = 18.5764(13) MeV (first neutron)Half-life:800(300) zsDecay constant λ:8.664339756999 × 10⁺¹⁷ s^-1Specific activity α:5.797541608333 × 10⁺⁴⁰ Bq g^-1
1.566903137387 × 10⁺³⁰ Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Isobaric spin: 1/2Mirror nucleus:Beryllium-9Year of discovery:1940

Radioactive Decay

The extremely unstable boron-9 atomic nucleus decays with the emission of a proton to beryllium-8, a also very unstable nuclide that splits almost immediately into two helium-4 nuclei (α particles). The corresponding net equation is:

⁹B → 2 ⁴He + ¹H.

Half-life T_½ = 800(300) zs respectively 8.0 × 10^-19 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
p	⁸Be	100 %

Parent Nuclides

Direct parent isotope is: ⁹C.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 4) and isobaric (same nucleon number A = 9) with Boron-9. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 4	Isobar A = 9
1	⁵H
2	⁶He	⁹He
3	⁷Li	⁹Li
4	⁸Be	⁹Be
5	⁹B	⁹B
6	¹⁰C	⁹C
7	¹¹N	⁹N
8	¹²O
9	¹³F

External data and identifiers

Adopted Levels, Gammas:NuDat 9B

Literature and References

[1] - R. O. Haxby, W. E. Shoupp, W. E. Stephens, W. H. Wells:
Thresholds for the Proton-Neutron Reactions of Lithium, Beryllium, Boron, and Carbon.
In: Physical Review, 58, 1035, (1940), DOI 10.1103/PhysRev.58.1035.

[2] - Tz Kokalova Wheldon, C. Wheldon:
Beautiful clusters - boron-9: simulations and decay.
In: Journal of Physics: Conference Series, 863, 012023, (2017), DOI 10.1088/1742-6596/863/1/012023.

[3] - Gordon McCann:
Measurement of near-threshold resonance properties in 9B for Big Bang Nucleosynthesis.
In: ads, (2021).