§16§Inelastic scattering of X-rays with very high energyresolution has finally become possible thanks to a newgeneration of high-intensity X-ray sources.This development marks the end to the traditional beliefthat low energy excitations like lattice vibrations cannotbe resolved directly with X-rays: Inelastic scatteringexperiments allow to observe directly the small energyshifts of the photons. Studies of lattice vibrations, ofexcitations in molecular crystals, of collective excitationsin liquids and electronic excitations in crystalsdemonstrating the broad applicability and power of this newtechnology are discussed in this book.The progress in this field opens up fantastic new researchareas not only in physics but also in other disciplines suchas materials science,biology and chemistry. §04§Basic considerations.- X-ray sources.- The INELAX instrument.- Other approaches to inelastic X-ray scattering.- Applications of inelastic X-ray scattering.- The future of the technique.- Final remarks. §02§Finally, the energies of very small excitations of condensed matter (crystals, liquids) important not only in physics but particularly in biology, chemistry and materials sciences can also be measured by inelastic X-ray scattering. This new technology is expected to become a standard diagnostic method in these disciplines.
