Transient resonance Rayleigh scattering from electronic states in disordered systems: Excitons in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple-quantum-well structures

Resonance Rayleigh scattering from electronic states in materials with static disorder is investigated both theoretically and experimentally. By using classical scattering theory we prove that this process, if excited by short optical pulses, decays with finite time constant determined by the coherence time or, equivalently, the homogeneous linewidth of the state. Experiments with picosecond time resolution at the (n=1, e-hh) exciton in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As multiple-quantum-well structures confirm this prediction. Exploiting the selection rules, from transient scattering the coherence time and energy-relaxation time are determined and measured as functions of exciton energy across the inhomogeneously broadened exciton band.