Available online www.jocpr.com Journal of Chemical and Pharmaceutical Research, 2012, 4(5):2545-2563 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 2545 Studies on effective atomic numbers and electron densities of some chemical explosives in the energy range 1KeV – 100 GeV Shivraj G. Gounhalli, Anil Shantappa, S. M. Hanagodimath* Department of physics, Gulbarga University Gulbarga 585106, Karnataka, India ______________________________________________________________________________ ABSTRACT The effective atomic numbers and electron densities of few chemical explosives (CW), viz., Trinitrotoluene (TNT), Trinitrophenylmethylnitramine (Tetryl),Pentaerythritoltetranitrate (PETN), Ciklotrimetilentrinitramin (RDX), Picrylchloride (PC), Nitroglycerin (NG) and Octogene (OG) have been calculated for total and partial photon interactions by the direct method in the wide energy range of 1 KeV-100 GeV using WinXCOM. The values of these parameters have been found to change with energy and composition of the chemical explosives (CW).The variations of effective atomic number and electron density with energy are shown graphically for all photon interactions. The variation of photon mass attenuation coefficients with energy are shown graphically only for total photon interaction. The variation of effective atomic number Z eff and electron densities N el is due to the variations in the dominance of different interaction processes in that particular energy region. Keywords: Chemical explosives; Photon mass attenuation coefficients; Effective atomic numbers; Electron densities. ______________________________________________________________________________ INTRODUCTION In view of the extensive use of radiative sources in medicine, agriculture, industry, security screening etc., the study of photon-atom interactions (attenuation and energy absorption coefficients) and effective atomic numbers in different materials have gained importance in the recent years. The photon mass attenuation coefficient, effective atomic number and electron density are the basic quantities required in determining the penetration of X-rays and gamma photons in matter. The mass attenuation coefficient (μ/ρ) is a measure of probability of interaction that occurs between incident photons and matter per unit area. The knowledge of mass attenuation coefficients of X-rays and gamma photons in biological, chemical and other important materials is of significant practical interest for industrial, biological, agricultural, defence and medical applications [1]. Accurate values of photon mass attenuation coefficients are required to provide essential data in diverse fields such as nuclear diagnostics (computerized tomography), nuclear medicine, radiation protection, radiation dosimetry, gamma ray fluorescence studies, radiation physics, shielding, security screening and etc. The mass attenuation coefficients are widely used in the calculation of photon penetration and energy deposition in shielding, biological and other dosimetric materials. G. J. Hine [2] has pointed out that in composite materials, for photon interactions, a single number cannot represent the atomic number uniquely across the entire energy region, as in the case of pure elements. This number for composite materials is known as “effective atomic number” (Z eff ) and it varies with energy. The energy absorption in a given medium can be calculated if certain constants are known. These necessary constants are Z eff and electron density N el of the medium. As effective atomic numbers and electron densities are useful in many technological applications, several investigators [3-19] have made extensive studies of effective atomic numbers in variety of composite materials like alloys, polymers, compounds, and mixtures, thermoluminescent dosimetric compounds,