Energy distribution of scattered x-radiation

Abstract

An attempt has been made in this paper to study the intensity distribution of X- radiation scattered from various substances. Employing heterogeneous primary radiations extending over a wide range of wavelengths and making proper corrections, the ratio Iφ/I₉₀ (where means the intensity of the scattered radiation in a direction making an angle φ with the primary beam) has been determined experimentally for angles 0 = 20°, 30°, 40°, 60° and 150°. The information obtained, as far as these experiments go, may be summarised briefly as follows.

In the backward direction, φ=150° (a) the experimental ratio Iφ/I₉₀, though approximating to the value (1+ cos²φ) for long waves, is invariably less than that given by this simple law. (b) For a particular wavelength, the deficiency of the experimental ratio Iφ/I₉₀ below (1 + cos²φ) is independent of the nature of the scattering material (within experimental error). (c) The deficiency of the experimental ratio Iφ/I₉₀ below (1 + cos²φ) increases as the wavelength decreases.

In the forward direction (a) The ratio Iφ/I₉₀, though approximating to the value (1 + cos²φ) for short waves, is invariably greater than that given by this simple law. (b) For a particular wavelength, the excess of the experimental ratio Iφ/I₉₀ over. (1 + cos²φ) , depends largely on the nature of the scattering material, increasing with an increase in the atomic number (or an average atomic number, as the case may be) of the scattering material. (c) For a particular scatterer, the excess of the experimental ratio Iφ/I₉₀ over (1 + cos²φ) decreases as the wavelength. decreases. (d) For a particular wavelength and a particular scatterer, the excess of the experimental ratio Iφ/I₉₀ over (1 + cos²φ) decreases as the angle φ increases.

In the backward direction, the intensity of scattering from different substances agrees very closely with that given by the quantum theory of Dirac, whereas in the forward direction, the observed scattering is complicated by interference effects and may be explained on the classical theory.