Number 198 (Story #1), October 12, 1994 by Phillip F. Schewe and Ben Stein THE 1994 PHYSICS NOBEL PRIZE goes to Bertram N. Brockhouse of McMaster University in Ontario, Canada and to Clifford G. Shull of MIT for their pioneering work in neutron scattering experiments during the 1940s and 1950s. Quantum mechanics holds that at the atomic level matter has both particle and wavelike properties. Slow-moving neutrons, considered as waves, are particularly valuable as a means of studying the structure and energy properties of crystals. Partly this is because the equivalent wavelength of the neutrons can be adjusted to match the spacing between the atoms in the crystal, or because the energies of the neutrons can be selected to match those of the characteristic vibrations of the crystal. Shull is being recognized for his work on experiments in which neutron waves fall on the crystal and scatter elastically (they lose no energy) in a process called diffraction. By detecting the scattered neutrons, the positions of the atoms in the lattice can be deduced. The neutrons can also scatter inelastically; that is, the neutrons lose energy by creating modes of vibration (phonons) in the crystal. In this case an analysis of the energies of the scattered neutrons provides information about the energy states of the crystal. Brockhouse won his half of the award for spectroscopic work of this type. Neutron diffraction has an important advantage over x-ray diffraction in that neutrons interact with (and therefore probe) the crystal's magnetic structure, while x rays cannot. To this day, the use of neutrons at many labs around the world (where, for example, neutrons can be produced at fission reactors) is an important way of studying diverse materials, such as biological samples and high-temperature superconductors. Contact Brockhouse at 416-648-6329; Shull at 617-862-8627. Magazine references: Scientific American, June 1979 (an article on cold neutrons) and Physics Today, January 1985 (a special issue on neutrons.)