[en] The ASDEX Thomson scattering apparatus measures the scattered light of the laserbeam (λ=10640 A) in the near infrared to obtain density and temperature profiles. Furthermore this kind of apparatus can be used to analyse plasma radiation for determining radial Z_eff profiles, as has been demonstrated at ASDEX for the first time. This method provides correct results, if the measured plasma radiation consists almost completly of bremsstrahlung. But besides bremsstrahlung the plasma emits recombination and line radiation. As shown by theoretical deliberations, recombination radiation is negligible, but line radiation can't be excluded. Therefore a spectral resolved measurement was performed, which made it possible to choose those of the different spectral measuring ranges of the Thomson scattering apparatus which are influenced least by line radiation. Furthermore the obtained results enables to allow for the remaining line radiation in order to get a radial profile of bremsstrahlung. This profile and the data of the Thomson scattering apparatus is used to determine Z_eff. The statistical errors are less then 10% in the plasma centre. There is a good agreement between Z_eff-profiles obtained by bremsstrahlung and the results of the charge exchange recombination spectroscopy. (orig.)