Abstract
THEORY and experimental work on the quantum reflexion and quantum scattering of X-rays are dealt with by Sir C. V. Raman in two papers (Proc. Boy. Soc, A, 179, 289 ; 1942). The quantum or modified scattering is due to the excitation of the elastic solid or low-frequency vibrations of the crystal lattice by the X-ray photon. It has a very low specific intensity proportional to N (the number of lattice cells) and is distributed over a wide range of solid angles. The quantum or modified reflexion is due to the excitation of the infra-red or characteristic high-frequency vibrations of the crystal lattice by the X-ray photons. Its intensity, like that of the classical or unmodified reflexions, is of the order N2, though usually smaller in absolute value than the intensity of the classical reflexions. The frequency changes which play a fundamental part in the theory of both phenomena appear as necessary consequences of both the classical and quantum theoretical points of view, but the law of intensity variation with temperature is quite different in the classical and quantum formulations. Experimental studies at low temperatures are specially important for the differences between the two theories. The influence of the modified X-ray reflexions on the intensity of the classical reflexions and their variation with temperature are discussed and shown to be of even greater importance then the effect on the same of the X-ray scattering by the elastic solid vibrations. In the second paper experimental results on diamond are reported agreeing with the theory.
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X-Ray Reflexion and Scattering with Frequency Change. Nature 149, 468 (1942). https://doi.org/10.1038/149468a0
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DOI: https://doi.org/10.1038/149468a0