Edge-enhanced soft X-ray phase-contrast microscopy exploiting the near K-edge optical properties of carbon

This paper proposes a method of microscopy we call "edge-enhanced soft X-ray phase-contrast microscopy". It employs a Hilbert-transform microscope setup and exploits the fact that for the same soft X-ray wavelength there is a marked difference in the refractive index for water and carbon. This method produces an edge-enhancement phase contrast image of the molecules that results from the difference in how the X-rays interact with water and the organic molecule of interest. Since this method can detect very small phase jumps, it enables one to observe molecules in vivo with high spatial resolution and high contrast. The results of simulating the technique using the absorption spectrum of tryptophan are presented and suggest that the proposed method will be useful for obtaining images of biological molecules in vivo.