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 September 23, 2009

Emil Wolf Proposes Method to Determine the Phases of X-ray Beams Diffracted by Crystals

Prof. Emil WolfIn a recent Physical Review Letters  paper, Wilson Professor of Optical Physics and Theoretical Physics Emil Wolf introduces a technique that overcomes the long-standing difficulties relating to measuring phases of diffracted x-ray beams in structure determination of crystals. The current methods incorrectly assume that x-rays are monochromatic, and as Wolf points out in a recent physicsworld.com article, this type of beam is not found in nature and cannot be created in the lab. He proposes that physicists use spatially coherent x-rays that can be produced in the lab and that they measure beam correlation functions to obtain missing structural data.

Specifically, he recommends measuring the amplitude and phase of the degree of spectral coherence, a physical property of x-rays. Once we have information about how x-rays with each wavelength interfere with one other, he says, we can uncover the electron density of the crystal. From there, we can deduce the structure of the solid.

If proven experimentally, Wolf's technique may help scientists improve drugs and other chemical formulations. The new technique may have implications in physics, chemistry, biology, and medicine.

Among all of his many publications, Professor Wolf is perhaps most well known for his classic book Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, which he wrote with Nobel Laureate Max Born. This book was first published in 1959 and is now in its seventh edition, which was published by Cambridge University Press in 1999.

For more details, see the articles listed below.

» read physicsworld.com article

» read PhysOrg.com article

» download the paper (PDF)