Measurements of Polarization Dependencies in Parametric Down-Conversion of X-rays into Ultraviolet Radiation

TL;DR

This study measures how polarization affects x-ray to ultraviolet parametric down-conversion, revealing discrepancies with classical models and supporting a quantum mechanical approach, which could advance atomic-scale charge distribution analysis.

Contribution

It provides the first experimental measurements of polarization dependencies in x-ray to UV parametric down-conversion, aligning with quantum theory and enabling new methods to study Wannier functions.

Findings

Discrepancies with classical nonlinearity models.

Qualitative agreement with quantum mechanical theory.

Potential for atomic-scale charge distribution reconstruction.

Abstract

We present measurements of the polarization dependencies of the x-ray signal photons generated by the effect of parametric down-conversion of x rays into ultraviolet radiation. The results exhibit pronounced discrepancies with the classical model for the nonlinearity but qualitatively agree with a newly developed quantum mechanical theory for the nonlinear interaction. Our work shows that the reconstruction of the atomic scale charge distribution of valence electrons in crystals by using nonlinear interaction between x rays and longer wavelength radiation, as was suggested in previous works, requires the knowledge of polarization of the generated x-ray signal beam. The results presented in this work indicate a new methodology for the study of properties of the Wannier functions in crystals.