Polarization studies of elastically scattered hard X-rays

Elastic scattering of photons by atoms describes the scattering process in which the energy of the incident and the scattered photon are equal. In the range of hard X-rays up to a photon energy of several 100 keV, this process is dominated by the so-called Rayleigh scattering, the scattering by the bound electrons of the atomic target. This scattering process can be described in the framework of quantum electrodynamic calculations, showing a strong influence on the polarization properties of the scattered radiation [1]. Thus, the determination of the polarization transfer in Rayleigh scattering can serve to verify the underlying theory.

In previous measurements, the elastic scattering of highly linearly polarized hard X-ray radiation has already been investigated for the case that the scattering plane spanned between incident and scattered radiation coincides with the polarization plane of the incident radiation [2]. Here it could be shown that the scattered radiation is still polarized in the scattering plane, but shows a depolarization strongly dependent on the scattering angle.

In our current measurement, we have left the polarization plane of the incident radiation. Here, in addition to a depolarization of the scattered beam, a tilting of the polarization vector with respect to the scattering plane is to be expected [3].

For this purpose, Rayleigh scattering of the highly linearly polarized hard X-rays (175 keV) from a thin gold foil (≈ 1 μm) was investigated during a beam time at the PETRA III synchrotron facilityExternal link in Hamburg. The investigation of the polarization properties of the scattered radiation was performed using a segmented semiconductor detector serving as a Compton polarimeter.