  The impact of particle production during inflation on the primordial
curvature perturbation spectrum is investigated both analytically and
numerically. We obtain an oscillatory behavior on small scales, while on large
scales the spectrum is unaffected. The amplitude of the oscillations is
proportional to the number of coupled fields, their mass, and the square of the
coupling constant. The oscillations are due a discontinuity in the second time
derivative of the inflaton, arising from a temporary violation of the slow-roll
conditions. A similar effect on the power spectrum should be produced also in
other inflationary models where the slow-roll conditions are temporarily
violated.
