Polarization transfer in hard x-ray Rayleigh scattering for non-coplanar geometry

We present an experimental study of the Rayleigh scattering of highly linearly polarized hard x rays. For this study, photons produced by a synchrotron source with an energy of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mn>175</a:mn> <a:mspace width="0.16em"/> <a:mi mathvariant="normal">k</a:mi> <a:mi mathvariant="normal">e</a:mi> <a:mi mathvariant="normal">V</a:mi> </a:mrow> </a:math> are scattered by a thin gold foil target. While the linear polarization in terms of degree of polarization and its orientation of the incident photon beam are well known, the outgoing scattered photons are analyzed by means of Compton polarimetry. For this, a polarimeter detector is positioned at different observation angles with respect to the incident photon beam. For the first time the polarization of elastically scattered photons outside of the polarization plane of the incident radiation is investigated, enabling novel access to a so-far untested component of the polarization transfer. The experimental findings are compared to predictions of two theoretical models. It is found that, when leaving the polarization plane of the incident photon beam, a strong deviation from the form factor approximation is evident, while calculations of the Rayleigh scattering in the <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mi>S</f:mi> </f:math> -matrix approach agree with the experimental results. Furthermore, this study is a foundation for future experiments dedicated to a polarization-resolved analysis of Delbrück scattering.