* Corresponding author. Fax: 02086342601; e-mail: rumenia @rusys.eg.net. Nuclear Instruments and Methods in Physics Research A 416 (1998) 64 — 69 Measurement of coherent plus incoherent differential scattering cross section of 59.54 keV -rays from anthracene and POPOP M.A. Abdel-Rahman*, N. Kamel Department of Physics, Faculty of Science, El-Minia University, El-Minia, Egypt Received 25 February 1998; received in revised form 5 May 1998; accepted 5 May 1998 Abstract Absolute values of coherent plus incoherent differential scattering cross sections of 59.54 keV -rays of Am from Anthracene (C  H  ) and POPOP (C  H  N  O  ), both used as detector materials, were experimentally determined for 10 scattering angles between 30° and 120°. The corresponding theoretical differential cross sections were calculated by means of form factors and incoherent scattering functions. A comparison between the experimentally determined results and the theoretically calculated values shows a good agreement, when the theoretical calculation of the atomic form factors and incoherent scattering functions were based on the summation of the individual form factors and incoherent scattering functions of their constituent elements in the molecule according to the number of atoms in the molecule.  1998 Elsevier Science B.V. All rights reserved. 1. Introduction Coherent and incoherent scatterings of low-en- ergy photons from atoms are important processes of the interaction of -rays with matter. These scat- tering cross sections acquired additional import- ance from their potential use in bio-medical prob- lems [1] and in many other areas of science and technology [2—9]. The coherent scattering is, in general, due to contributions from Rayleigh scat- tering, nuclear Thomson scattering and Delbruck scattering. In the region of -ray energy with which this work is concerned, of these elastic scattering processes, only Rayleigh scattering makes any sig- nificant contribution to the total scattering cross section. Also, coherent and incoherent scatterings of photons by bound electrons are of interest and have been studied by several workers [10—12]. Ex- perimental differential scattering cross section data for compounds are scarce. Since it is important to know the differential scattering cross sections of detector materials in order to obtain response functions, Ozmutlu [13] measured the differential scattering cross section (coherent plus incoherent) for NaI(Tl) crystal. With this in view, the coherent pluse incoherent scattering cross section of 59.54 keV -ray from organic detector materials (Anthracene and POPOP) have been measured at 10 scattering angles in the angular range of 30—120°. 0168-9002/98/$19.00  1998 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 9 8 ) 0 0 6 5 2 - 4