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The ability to image matter on the microscopic scale is of fundamental importance to many areas of research and development including pharmacology, materials science and nanotechnology. Owing to its generality, x-ray scattering is one of the most powerful tools available for structural studies. The major limitation however is the necessity of producing suitable crystalline structures – this technique relies upon many x-ray photons being scattered from a large number of molecules with identical orientations. As it is neither possible nor desirable to crystallise every molecule of interest, this has provided a huge drawback for most biotechnologies. Although improvements in both sources and detectors have had a strong impact in this area, driving down the required sample size, the need for macroscopic crystalline samples remains a fundamental bottleneck. Fortunately recent technological developments in the generation and sub-micron focusing of soft x-rays (SXRs) have provided a route for bypassing the need for a regular, crystalline structure. For the purposes of this chapter, SXRs are defined as electromagnetic radiation with wavelengths from 1 – 50 nm, which correspond to photon energies of 1.2 keV – 25 eV respectively. As their wavelengths are on a comparable scale to objects such as proteins, cells and quantum dots, SXRs are ideally suited for imaging these targets with a high spatial resolution. Furthermore water is transparent and carbon opaque to SXRs whose wavelengths lie between 2 – 4 nm, the so-called water window. This offers clear potential for the imaging of biological molecules within their native, aqueous environment, something that would be impossible using traditional x-ray crystallography experiments. Unsurprisingly there has been great interest in the production and application of SXRs across a wide range of scientific endeavours including, but not limited to, resolving electron motion (Drescher et al |
