Carbon-8

Properties and data of the isotope ⁸C.

Contents

Carbon-8 is a radioisotope of the chemical element carbon, which, in addition to the element-specific 6 protons, has 2 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; Studying ⁸C is for academic purposes only.

The discovery of the proton-rich isotope was reported in 1974: The production of carbon-8 was achieved in a cyclolotron by irradiating natural carbon-12 with a beam of α-particles (helium-4 nuclei) accelerated to 156 MeV:

¹²C(α,⁸He)⁸C.

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

General data

Name of the isotope:Carbon-8; C-8Symbol:⁸C or 86CMass number A:8 (= number of nucleons)Atomic number Z:6 (= number of protons)Neutrons N:2Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):0.33333333333333 (= neutron-proton ratio)Neutron excess (N-Z):-4Isotopic mass:8.037643(20) u (atomic weight of Carbon-8)Nuclide mass:8.0343515 u (calculated nuclear mass without electrons)Mass excess:35.06423 MeVMass defect:0.026637024000001 u (per nucleus)Nuclear binding energy:24.81222803 MeV (per nucleus)
3.1015285 MeV (average binding energy per nucleon)Half-life:3.5(1.4) zsDecay constant λ:1.980420515885 × 10⁺²⁰ s^-1Specific activity α:1.490796413571 × 10⁺⁴³ Bq g^-1
4.029179496138 × 10⁺³² Ci g^-1Spin and parity:
(nuclear angular momentum)0+Isobaric spin: 2Charge radius:3.751 femtometer fmMatter radius:3.324 femtometer fmMirror nucleus:Helium-8Year of discovery:1974

Radioactive Decay

Half-life T_½ = 3.5(1.4) zs respectively 3.5 × 10^-21 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
2p	⁶Be	100 %	12.143(18) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 2) and isobaric (same nucleon number A = 8) with Carbon-8. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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

External data and identifiers

Adopted Levels, Gammas:NuDat 8C

Literature and References

[1] - R. G. H. Robertson, S. Martin, W. R. Falk, D. Ingham, A. Djaloeis:
Highly Proton-Rich T_z = -2 Nuclides: ⁸C and ²⁰Mg.
In: Physical Review Letters, 32, 1207, (1974), DOI 10.1103/PhysRevLett.32.1207.