Er 169
9.39 d
β- 0.3...
γ (110...)

Chemical properties

Er-169 is a radiolanthanide, usually in trivalent state. The ionic radius of Er3+ is 89 pm, i.e. just 3% larger than Lu3+, which explains that chelators suitable for Lu-177 can be directly employed for Er-169 too, in particular DOTA.

Nuclear properties

Er-169 decays by beta-minus emission with a half-life of 9.392(18) days to stable Tm-169. In addition to beta-minus emission it shows emission of low energy conversion and Auger electrons , thus emitting in total about 1.45 electrons (with energies above 6 keV) per decay. However, gamma ray and X-ray emission is very weak.

The mean electron energy emitted per decay is 103 keV, the mean photon energy per decay is <1 keV .


Er-169 is produced by thermal neutron irradiation of enriched Er-168 oxide targets in the high flux reactors of the PRISMAP production facilities: RHF at ILL or BR2 at SCK CEN.


Off-line mass separation is performed at the PRISMAP production facility MEDICIS (CERN, Geneva, Switzerland). Activity will be shipped from there to the users in form of ErCl3 solution or in solid form, implanted into an Al, Zn or NaCl layer.

Purity grades available


No carrier added (n.c.a.)

Available in n.c.a form (but not in theoretical specific activity)
Half-life9.39 d
DaughterStable Tm-169
Branching Ratio/Decay100% β-
ProductionEr-168(n,𝛾) Er-169
PurificationOff-line mass separation + 2-step column separation
Chemical FormIn 0.05 M HCl
Specific Activityn.a.
Radionuclidic Purity>99%
Radiochemical Purityn.a.
Chemical Purityn.a.
IdentificationPresence of 109.8 keV gamma line
AppearanceClear solution
Activity available100 MBq
AvailabilityFew times per year (planning in advance), depends on reactor and MEDICIS schedule
Gradepreclinical, n.c.a.
Other informationResearch grade implanted in Al, Zn or NaCl layer on Au foil also possible


  • β-therapy

Point of supply

  • Geneva, Switzerland

Involved production facilities

ILL, France
CERN, International
SCK CEN, Belgium