  We have found a novel mechanism of spectral broadening and dephasing in
quantum dots (QDs) due to the coupling to longitudinal-optical (LO) phonons. In
theory, this mechanism comes into play only if the complete manifold of exciton
levels (including those in the wetting-layer continuum) is taken into account.
We demonstrate this nontrivial dephasing in different types of QDs, using the
exactly solvable quadratic coupling model, here generalized to an arbitrary
number of excitonic states.
