Diffraction Imaging of the General Particle

At most synchrotrons today, something like 10 percent of the photons generated are employed in experiments in which a crystal is illuminated and its far-field coherently scattered x-ray diffraction pattern is measured. From the measurements crystallographers have for years prepared the atomic-, or near-atomic-, resolution 3-dimensional images of matter which have made possible much of 20th century science. X-ray crystallography is thriving today, but it could do much more if it were not required to work with crystals. Crystals call for very large numbers of exact copies of the structure of interest, and for many of the most interesting structures numerous exact copies cannot or do not exist. Amorphous materials, imperfect crystals, and biological cells are examples of this kind. In other cases exact copies may exist, but may be hard to persuade to form crystals. Many biological macromolecules fall in this category.