Inelastic electron-exciton scattering in bulk germanium

We investigate the destructive inelastic as well as the elastic scattering of a hot electron-hole plasma with an incoherent exciton population in bulk Ge by means of optical pump-terahertz probe spectroscopy. An incoherent exciton population evolves from a first optical pulse while a delayed second optical pulse creates the electronhole plasma. The interaction of the plasma with the exciton population is monitored via the intraexcitonic transitions by a probing terahertz pulse. Analyzing the density-dependent decay of the intraexcitonic transitions after the arrival of the second optical pulse yields an inelastic scattering rate of 2.0 x 10(-4)cm(3)s(-1). An analysis of the corresponding linewidth of the 1s - 2p transition yields a total scattering rate of 3.7 x 10(-4)cm(3)s(-1). This allows us to experimentally distinguish between elastic and inelastic scattering and we obtain an elastic scattering rate of 1.7 x 10(-4)cm(3)s(-1).