Germanium-68

Properties and data of the isotope ⁶⁸Ge.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Germanium-68 is a radioisotope of the chemical element germanium, which has 36 neutrons in its atomic nucleus in addition to the element-specific 32 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 68.

The isotope, which is only synthetically accessible, can be produced by irradiating stable zinc-66 with α particles (helium-4 atomic nuclei) in an accelerator; this nuclear reaction emits 2 neutrons:

⁶⁶Zn(α,2n)⁶⁸Ge.

Germanium-68 in turn decays to gallium-68, a positron-emitting nuclide that is used in nuclear medicine. Corresponding radionuclide generators are called ⁶⁸Ge/⁶⁸Ga generators.

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

General data

Name of the isotope:Germanium-68; Ge-68Symbol:⁶⁸Ge or 6832GeMass number A:68 (= number of nucleons)Atomic number Z:32 (= number of protons)Neutrons N:36Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.125 (= neutron-proton ratio)Neutron excess (N-Z):4Isotopic mass:67.9280953(20) u (atomic weight of Germanium-68)Nuclide mass:67.9105413 u (calculated nuclear mass without electrons)Mass excess:-66.9788 MeVMass defect:0.63424270000002 u (per nucleus)Nuclear binding energy:590.79326959 MeV (per nucleus)
8.68813632 MeV (average binding energy per nucleon)Separation energy:S_N = 12.376(5) MeV (first neutron)
S_P = 7.3886(22) MeV (first proton)Half-life:271.05(8) dDecay constant λ:2.959799598611 × 10^-8 s^-1Specific activity α:2.623999646318 × 10⁺¹⁴ Bq g^-1
7091.8909359962 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Mirror nucleus:Krypton-68Year of discovery:1948

Radioactive Decay

Half-life T_½ = 271.05(8) d respectively 2.3418720 × 10⁷ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC	⁶⁸Ga	100 %	0.1073(24) MeV

Formation and radioactive decay scheme of Germanium-68

Parent Nuclides

Direct parent isotopes are: ⁶⁸As, ⁶⁹Se.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 36) and isobaric (same nucleon number A = 68) with Germanium-68. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 36	Isobar A = 68
18	⁵⁴Ar
19	⁵⁵K
20	⁵⁶Ca
21	⁵⁷Sc
22	⁵⁸Ti
23	⁵⁹V	⁶⁸V
24	⁶⁰Cr	⁶⁸Cr
25	⁶¹Mn	⁶⁸Mn
26	⁶²Fe	⁶⁸Fe
27	⁶³Co	⁶⁸Co
28	⁶⁴Ni	⁶⁸Ni
29	⁶⁵Cu	⁶⁸Cu
30	⁶⁶Zn	⁶⁸Zn
31	⁶⁷Ga	⁶⁸Ga
32	⁶⁸Ge	⁶⁸Ge
33	⁶⁹As	⁶⁸As
34	⁷⁰Se	⁶⁸Se
35	⁷¹Br	⁶⁸Br
36	⁷²Kr	⁶⁸Kr
37	⁷³Rb
38	⁷⁴Sr

Data changes (history)

The half-life of the isotope was re-determined according to a publication from 2018 and adopted here [1]. Previous value: 270.95(13) days.

External data and identifiers

CAS:15756-77-1InChI Key:GNPVGFCGXDBREM-FTXFMUIASA-NSMILES:[68Ge]PubChem:ID 6337084Adopted Levels, Gammas:NuDat 68Ge

Literature and References

[1] - Denis E. Bergeron, Jeffrey T. Cessna, Brian E. Zimmerman:
Two determinations of the Ge-68 half-life.
In: Applied Radiation and Isotopes, 134, (2018), DOI 10.1016/j.apradiso.2017.10.038.