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Most of what we know about structure and dynamics of condensed matter systems on an atomic length- and timescale stems from X-ray and neutron scattering. The IFF Spring School 2012 comes timely to the centennial anniversary of the discovery of X-ray scattering from single crystals by Max von Laue, Walter Friedrich and Paul Knipping in 1912. Their breakthrough discovery proved the wave nature of X-rays as well as the microscopic structure of crystals as being composed of periodic arrangements of atoms. In 1914 the Noble prize was awarded to Max von Laue for this discovery. Most of our present-day knowledge on the atomic structure of crystalline and amorphous matter is based on the work following Max von Laue employing laboratory X-ray sources for X-ray crystallography. Since the middle of last century synchrotron radiation with its unique properties was employed for more challenging studies, e.g. in macromolecular crystallography. With the advent of research reactors nearly 40 years later, neutron scattering came into play with its alternate contrast mechanism, its sensitivity to atomic magnetism and collective excitations in solids. Again the Noble prize was awarded to the two pioneers of neutron diffraction and inelastic scattering, Clifford Shull and Bertram Brockhouse, in 1994....

Imagine you leave this lecture hall, some mean looking guys dressed entirely in black follow, kidnap and take you to the medieval castle of Nideggen in the close-by Eifel mountains. There you are being thrown into a pitch dark dungeon. You cannot see anything, but you hear some noises. Are there rats? Are there other prisoners? Are there dragons? Luckily you remember that you have some matches in your pocket. You light a match, you can see everything around you and everything becomes clear to you… What I have just described is essentially like a scattering experiment: figuratively it sheds light into darkness and helps us understand the world around us. Let’s analyse what you did in the dungeon: first when you light the match, you start a source of radiation. Here the radiation is light. This light then gets scattered (reflected, transmitted) from the surrounding objects. In a scientific scattering experiment, we will call this object a “sample”. Back to the dungeon: some of this radiation gets scattered into your eye. Your eye serves as very special radiation detector: with its lens, it is able to even make an image of the objects on the retina, which in the language of a physicist would be called an “area position sensitive pixel detector”. This image contains lots of information: the colour of the backscattered light tells you something about the absorption of certain components of the light and therefore gives information about the material the light is scattered from. The position of the signal on the retina gives you information about the spatial arrangement of the objects around you. And finally the time dependence of the signal tells you that the monster is actually crawling towards you, ready to attack. All this information has to be treated and interpreted. This is done by our brain, an extremely powerful computer to analyse this wealth of data....