Ba 128
2.43 d
no β+
γ (273)
Cs 128
3.64 m
γ 443, 527...

Chemical properties

Barium ions are usually in divalent state and can serve as surrogate for the lighter homologue calcium.

Nuclear properties

Ba-128 decays by electron capture with a half-life of 2.43(5) days to Cs-128. Cs-128 decays by β+ emission (68.8(13)%) and electron capture (31.2(13)%) with a half-life of 3.640(14) min to stable Xe-128.

Cs-128 emits a high energy positron spectrum with 1260(30) keV average energy and 2907 keV maximum energy (similar to e.g. Cu-62 or Br-76).

Ba-128 emits γ-rays mainly at 273 keV (14.5(7)%) and Cs-128 emits γ-rays mainly at 443 keV (26.8(13)%) and 527 keV (2.41(12)%).

The mean electron energy emitted per Ba-128 decay is 7 keV, the mean photon energy per decay is 66 keV. The mean electron energy emitted per Cs-128 decay is 869 keV, the mean photon energy per decay is 884 keV .


Ba-128 is produced by high energy proton induced spallation of lanthanum carbide or tantalum foil targets at CERN. An off-line mass separation is performed at the CERN MEDICIS facility (Switzerland). The mass-separated ions are implanted into a solid matrix, e.g. a NaCl layer on a noble metal backing. The implanted layer can be dissolved and used directly or can undergo a radiochemical purification step.


Activity will be shipped in form of ion-implanted solid samples or liquid solutions of BaCl2. Experiments with Ba-128/Cs-128 are best performed at the WP3 lab AGORA in Lausanne, Switzerland that has already experience with this radionuclide.

Examples of use

  • Use of Ba-128/Cs-128 for PET imaging has been reported .

Purity grades available


No carrier added (n.c.a.)

Production routeLaCx(p,spallation) or Ta(p, spallation)
DaughterDecays to Cs-128 (T1/2=3.6 min) that decays to stable Xe-128
Half-life2.43 d
ProcessingOff-line mass separation (solid) or with an additional 1-step column separation (liquid)
Primary Container
Product Graden.c.a.
Physical FormSolid or liquid
Chemical FormImplanted in solid layer or liquid
Radioactive Concentration (gamma spectrometry)For liquid solution > 50MBq/ml
Appearancemplanted metalic foil with backing or clear colourless solution
Radionuclide identification (gamma spectrometry)273 keV and 443 keV gamma lines present
Radionuclidic Purity (gamma spectrometry)>99.99%
Chemical purity (ICP-OES)n.a.
Molar activity (ICP-OES)n.a.
Apparent Molar Activity>99% theoretical activity
Microbiological qualityn.a.
Bacterial endotoxinn.a.
pH (pH strips)n.a.
Additional information
Activity available25MBq, few times per year (planning in advance)
Activity limit for UN2910 (excepted package) shipment20 MBq in dry state or 2 MBq in liquid form
Other informationImplanted in Al, Zn or NaCl layer on Au or other metal foils.


  • PET

Point of supply

  • Geneva, Switzerland

Involved production facilities

CERN, International

Involved biomedical facilities

To find out in which biomedical facilities you can use this radionuclide, contact the helpdesk.