  We find an unambiguous relationship between disorder-driven features in the
temperature dependence of the resistance and the behavior, as functions of the
temperature, of the parameters necessary to describe some of the relaxation
processes in the photoinduced differential time-resolved reflectivity of three
samples of Nd$_{1.83}$Ce$_{0.17}$CuO$_{4\pm\delta}$. The latter, sharing the
same Ce content, have been fabricated and annealed ad-hoc in order to differ
only for the degree of disorder, mainly related to oxygen content and location,
and, consequently, for the temperature dependence of the resistance: two of
them present a minimum in the resistance and behave as a superconductor and as
a metal, respectively, the third behaves as an insulator. The systematic
coherence between the resistance and the relaxation parameters behaviors in
temperature for all three samples is absolutely remarkable and shows that
pump-probe measurements can be extremely sensitive to disorder as it drives the
emergence of new excitations and of the related relaxation channels as in this
paradigmatic case.
