Creation of X-Ray Transparency of Matter by Stimulated Elastic Forward Scattering

TL;DR

This paper demonstrates how high-intensity coherent x-ray pulses induce stimulated elastic forward scattering, fundamentally altering the traditional Beer-Lambert law and affecting x-ray absorption and dichroism in matter.

Contribution

It provides an analytical modification to the Beer-Lambert law accounting for stimulated scattering effects at high x-ray intensities.

Findings

Absorption and dichroic contrasts diminish with increasing x-ray intensity.

Stimulated elastic forward scattering lowers the stimulation threshold significantly.

The modified law applies to resonant core-to-valence electronic transitions.

Abstract

X-ray absorption by matter has long been described by the famous Beer-Lambert law. Here we show how this fundamental law needs to be modified for high-intensity coherent x-ray pulses, now available at x-ray free electron lasers, due to the onset of stimulated elastic forward scattering. We present an analytical expression for the modified polarization-dependent Beer-Lambert law for the case of resonant core-to-valence electronic transitions and incident transform limited x-ray pulses. Upon transmission through a solid, the absorption and dichroic contrasts are found to vanish with increasing x-ray intensity, with the stimulation threshold lowered by orders of magnitude through a super-radiative coherent effect. Our results have broad implications for the study of matter with x-ray lasers.