The simple theory of the fullerite photodarkening dependence on the la
ser energy fluence is presented. The theory is based on the realistic
electron band structure of fullerites. It is shown that this theory is
sufficient for the qualitative description of the nonlinear optical p
roperties of fullerites in the energy region around HBARomega=2 eV. Th
e physical effects that appear at high excitation levels are discussed
. The multi-step ionization and wide-band luminescence are predicted.