I am writing this as I embark on a journey from Copenhagen to Chicago for a 24-hour experiment. Luckily, I am going to be in the city longer than I will be flying, but only just. Traveling over 4,000 miles may seem like a long way to go for an experiment, and it is. I perform small-angle scattering experiments for a living though, and sometimes this is just what needs to be done. My previous post on Softbites was all about the fundamentals of X-ray and neutron scattering, but I didn’t give an indication of what an experiment is actually like. This post focuses on the practicalities. What are the experimental facilities like? What do you have to do to access them?
We are surrounded by phenomena caused by the scattering of light. When enjoying a sunny day at the seaside, like in the photo at the top, why is the sky blue? Blue light scatters more than red light. Why is milk opaque? Protein and fat particles scatter light. If you are reading this with blue eyes, your eye color is due to light scattering. Scientists use the same general scattering principle to study the structure of soft materials using the scattering of well-defined radiation. Scattering measurements reveal structures between an ångström and hundreds of nanometers, an important region for studying soft matter. Just as the color of the sky results from light scattered by air molecules, the scattering of X-rays and neutrons tells us about the size and shape of compounds in soft materials along with their interactions, and I will focus on these two types of radiation.