  An experimental test of the electron energy scale linearities of SNO+ and
EJ-301 scintillators was carried out using a Compton spectrometer with
electrons in the energy range 0.09-3 MeV. The linearity of the apparatus was
explicitly demonstrated. It was found that the response of both types of
scintillators with respect to electrons becomes non-linear below ~0.4 MeV. An
explanation is given in terms of Cherenkov light absorption and re-emission by
the scintillators.
