  Exciton energy structure and population dynamics in a wide CdTe/CdZnTe
quantum well are studied by spectrally-resolved pump-probe spectroscopy.
Multiple excitonic resonances in reflectance spectra are observed and
identified by solving numerically three-dimensional Schr\"odinger equation. The
pump-probe reflectivity signal is shown to be dominated by the photoinduced
nonradiative broadening of the excitonic resonances, while pump-induced exciton
energy shift and reduction of the oscillator strength appear to be negligible.
This broadening is induced by the reservoir of dark excitons with large
in-plane wave vector, which are coupled to the the bright excitons states. The
dynamics of the pump-induced nonradiative broadening observed experimentally is
characterised by three components: signal build up on the scale of tens of
picoseconds (i) and bi-exponential decay on the scale of one nanosecond (ii)
and ten nanosecons (iii). Possible mechanisms of the reservoir population and
depletion responsible for this behaviour are discussed.
