Professor Andrew Richard Lang
1975 Fellow of the Royal Society
1997 Gave the BCA Lonsdale lecture
1997 Hughes Medal of the Royal Society
2002 Honorary member of BCA
2005 Senior Research Fellow and Emeritus Professor of Physics,
University of Bristol
Distinguished for his pioneering studies in X-ray diffraction physics,
especially for his developments of the techniques of X-ray topography. These
image imperfections in crystals: such as dislocations, stacking faults,
growth-sector boundaries and ferromagnetic domains. For half a century,
Lang's methods have been widely used in the assessment of crystals for the
electronics and other industries. He has studied many types of X-ray
diffraction phenomena, including X-ray moiré fringes, the first direct
observation of a refractive index for X rays greater than unity, and
Borrmann-Lehmann fringes. Perhaps his most important discovery in this
category was
that of Pendellösung fringes (with Norio Kato in 1959) in wedge-shaped
perfect crystals, which are due to intensity variations of the internal
wave-field. The fringe spacing led to the determination of absolute
structure amplitudes.
Lang has also made important discoveries using other techniques, especially electron microscropy and cathodoluminescence, separately and in combination with X-ray topography; and he has studied a wide range of crystalline materials: including metals, semiconductors, quartz and diamond. His work exhibits sustained innovativeness, craftmanship in experimentation, and perceptiveness and thoroughness in the analysis of experiments.
Moreton Moore
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