Beryllium-7

Properties and data of the isotope ⁷Be.

Contents

The very short-lived beryllium isotope with a mass of 7, with a half-life of approximately 53 days, only occurs on Earth in very small traces, namely as an atmospheric spallation product of oxygen and nitrogen due to the action of cosmic radiation.

The atomic nucleus of the nuclide with the formula ⁷Be consists of the 4 protons, which are element-specific for beryllium, and 3 neutrons.

The radioisotope was discovered by bombarding a template of Lithium fluoride (LiF) with deuterons (hydrogen-2) accelerated to 1 MeV; a corresponding report was published in 1938:

⁶Li(d,n)⁷Be.

There are no practical technical applications for the Be isotope.

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

General data

Name of the isotope:Beryllium-7; Be-7Symbol:⁷Be or 74BeMass number A:7 (= number of nucleons)Atomic number Z:4 (= number of protons)Neutrons N:3Isotopic mass:7.01692871(8) u (atomic weight of Beryllium-7)Nuclide mass:7.0147344 u (calculated nuclear mass without electrons)Mass excess:15.76899 MeVMass defect:0.040366166 u (per nucleus)Nuclear binding energy:37.60084143 MeV (per nucleus)
5.37154878 MeV (average binding energy per nucleon)Separation energy:S_N = 10.677(5) MeV (first neutron)
S_P = 5.60685(7) MeV (first proton)Half-life:53.22(6) dDecay constant λ:1.507428938751 × 10^-7 s^-1Specific activity α:1.296849915072 × 10⁺¹⁶ Bq g^-1
350499.97704662 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Isobaric spin: 1/2Magnetic dipole moment:μ(μ_N) = -1.399280(4)Nuclear g-factor:g_l = -0.93285333333333Charge radius:2.646(16) femtometer fmMirror nucleus:Lithium-7Year of discovery:1938

Radioactive Decay

74Be + e^- → 73Li + γ | half-life = 53,22 days.

The gamma radiation (gamma quantum γ per decay) has an energy of 477.6035(20) keV; Intensity 10.44(4)%, dose 0.04989(19) MeV/Bq-s.

Half-life T_½ = 53.22(6) d respectively 4.598208 × 10⁶ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC	⁷Li	100 %	0.86189(7) MeV	477.6035(20) keV 10.44(4) %

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 3) and isobaric (same nucleon number A = 7) with Beryllium-7. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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

External data and identifiers

CAS:3966-02-4InChI Key:ATBAMAFKBVZNFJ-YPZZEJLDSA-NSMILES:[7Be]PubChem:ID 6335489Adopted Levels, Gammas:NuDat 7Be

Literature and References

[1] - R. B. Roberts, N. P. Heydenburg, G. L. Locher:
Radioactivity of Be⁷.
In: Physical Review, 53, 1016, (1938), DOI 10.1103/PhysRev.53.1016.

[2] - T. Ohtsuki, H. Yuki, M. Muto, J. Kasagi, K. Ohno:
Enhanced Electron-Capture Decay Rate of ⁷Be Encapsulated in C₆₀ Cages.
In: Physical Review Letters, 93, 112501, (2004), DOI 10.1103/PhysRevLett.93.112501.

[3] - M. Yoshimori:
Production and behavior of beryllium 7 radionuclide in the upper atmosphere.
In: Advances in Space Research, (2005), DOI 10.1016/j.asr.2005.04.093.

[4] - L. Damone et al.:
⁷Be (n,p)⁷Li Reaction and the Cosmological Lithium Problem: Measurement of the Cross Section in a Wide Energy Range at n_TOF at CERN.
In: Physical Review Letters, (2018), DOI 10.1103/PhysRevLett.121.042701.