Neutrons and x-rays probe properties of particles which are the basic components of matter and complement each other nicely. They form radiations with similar wavelength ranges in the nanometer range, however x-rays are sensitive to charged particles, in particular electrons in atoms, while neutrons interact with massive particles such as atom nuclei and possess a magnetic moment which makes them like a microscopic compass.

X-rays are said to be electronic while neutrons are magnetic!

A major difference between neutrons and x-rays arises from sources to produce them. Synchrotron x-ray sources are very bright and focussed: they produce narrow parallel beams of x-rays with high degree of monochromaticity. Neutron sources are big, unfocussed and lead to neutron beams which are at least 10-12 orders magnitude less bright than x-ray beams!

However, neutrons are unique and are needed for their applications in magnetism, in studies of liquids, polymers, soft matter and biology because neutrons easily locate hydrogen atoms.

The obvious strategy for scientists is to use both x-ray and neutrons. With x-rays, they observe static atomic arrangements and detect electronic properties. With neutrons, a very gentle probe, scientists observe motions of atoms, arrangement and dynamics of magnetic moments in materials, and determine bio-active centres in biological macromolecules or proteins.

More intense neutron beams are needed!

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