Fig. 3.

Simulated spectra of deposited energy in plastic scintillators for gamma quanta from $e^{+}{e}^{-}\to 2\mathit{\gamma }$ annihilation and for de-excitation gamma quanta originating from isotopes indicated in the legend. The spectra were simulated including the energy resolution of the J-PET detector [20] and were normalized to the same number of events