The radiative electron capture of a target electron into the projectile continuum has been studied for the collision system U 88+ + N 2 → U 88+ + [N + 2 ] * + e − + γ at 90 MeV/u. Using a magnetic electron spectrometer, the energy distribution of cusp electrons emitted under an angle of 0 • with respect to the projectile beam and with a velocity close to the projectile velocity has been measured in coincidence with the emitted photons under various observation angles. The experimental results provide a stringent test for the corresponding process in inverse kinematics, namely, the theory of electron-nucleus bremsstrahlung at the high-energy endpoint. For comparison this process is calculated using fully relativistic Dirac wave functions and using semirelativistic Sommerfeld-Maue wave functions.

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The following errors were introduced in the production process:• In the abstract it says that at θ=90°, a degree of polarization of +0.27%±0.12% was measured. This number should be +27%±12%.• On page 5 there are three occurrences of an amplitude A. All of them should be A P instead. AbstractWe report on the first elastic hard x-ray scattering experiment where the linear polarization characteristics of both the incident and the scattered radiation were observed. Rayleigh scattering was investigated in a relativistic regime by using a high-Z target material, namely gold, and a photon energy of 175keV. Although the incident synchrotron radiation was nearly 100% linearly polarized, at a scattering angle of 90 q =  we observed a strong depolarization for the scattered photons with a degree of linear polarization of 0.27% 0.12% +  only. This finding agrees with second-order quantum electrodynamics calculations of Rayleigh scattering, when taking into account a small polarization impurity of the incident photon beam which was determined to be close to 98%. The latter value was obtained independently from the elastic scattering by analyzing photons that were Compton-scattered in the target. Moreover, our results indicate that when relying on state-of-the-art theory, Rayleigh scattering could provide a very accurate method to diagnose polarization impurities in a broad region of hard x-ray energies.