Option for simulation of nuclear metastable levels


I’m writing a code to simulate the decay of radioactive nuclides.
Some of them, for example the Co57 and the Np239, have metastable nuclear levels with a mean life in order of 100-200 ns.
When Geant simulate the decay of these nuclides does not take into account the presence of these mean lives and process the photons from that level “in coincidence” with the other particles emitted in the decay process.

Are there an option, like the length threshold for particles production, to tell Geant that must consider these levels as metastable and assign them a time based on their mean life?

Thank you for your help!

see examples/extended/radioactivedecay/rdecay01/src/PhysicsList.cc : line 65

Thank you very much! In the example i have found the solution!