LET has therefore no meaning when applied to photons. However, many authors speak of "gamma LET" anyway, where they are actually referring to the LET of the secondary electrons, i.e., mainly Compton electrons, produced by the gamma radiation. The secondary electrons will ionize far more atoms than the primary photon. This gamma LET has little relation to the attenuation rate of the beam, but it may have some correlation to the microscopic defects produced in the absorber. It must be noted that even a monoenergetic gamma beam will produce a spectrum of electrons, and each secondary electron will have a variable LET as it slows down, as discussed above. The "gamma LET" is therefore an average.