  We have implemented the gedanken experiment of an individual atom scattering
a wave packet of near-resonant light, and measured the associated Wigner
time-delay as a function of the frequency of the light. In our apparatus the
atom behaves as a two-level system and we have found delays as large as 42
nanoseconds at resonance, limited by the lifetime of the excited state. This
delay is an important parameter in the problem of collective near-resonant
scattering by an ensemble of interacting particles, which is encountered in
many areas of physics.
