Application of asymmetry depending empirical formulas for (p,na) reaction cross-sections at 24.8 and 28.5 MeV incident energies E. Tel a,Ã , E.G. Aydin a , A. Aydin b , A. Kaplan c a Faculty of Arts and Sciences, Gazi University, 06500 Ankara, Turkey b Faculty of Arts and Sciences, Kirikkale University, 71450 Kirikkale, Turkey c Faculty of Arts and Sciences, Su ¨leyman Demirel University, 32260 Isparta, Turkey article info Article history: Received 15 March 2008 Received in revised form 28 October 2008 Accepted 2 November 2008 Keywords: Cross-section (p,na) reaction Empirical formulas Asymmetry term abstract In this study, we have investigated the asymmetry term effect for the (p,na) reaction cross-sections and we have obtained new coefficients for the (p,na) reactions at 24.8 and 28.5 MeV energies. We have suggested empirical formulas including the new coefficients found by fitting two parameters for proton induced reactions. The coefficients were determined by least-squares fitting method. The obtained cross-section formulas with new coefficients have been discussed and compared with the available experimental data. & 2008 Elsevier Ltd. All rights reserved. 1. Introduction The cross-section evaluation for materials irradiated by protons attends special importance to use of systematic of proton induced reaction cross-section. So, to satisfy growing needs in nuclear data at intermediate proton energies, the new proton activation data file (PADF) has been prepared (Broeders and Konobeyev, 2007; Koning et al., 2004; Broeders et al., 2006a). The intermediate-energetic proton induced reactions can be used to produce radionuclide and these radionuclides can be used in medicine and industry (Aydin et al., 2007, 2008). And also the high-energetic proton induced reactions are required for advanced nuclear systems, such as spallation reactions for production of neutrons in spallation neutron source (Korovin et al., 2001; Koning et al., 1998). Nowadays, the experimental cross-sections are available in EXFOR data file (EXFOR/CSISRS, 2007) and in the evaluated data files (such as ENDF/B-VII, JENDL-HE and JEEF-3.1). These data files contain the information for a few tens of stable nuclides (Korovin et al., 2001; Koning et al., 1998). But, still is not enough for a complete and detailed study of activation and transmutation materials irradiated with intermediate-energetic protons (Handbook for Calculations of Nuclear Reaction Data, 1998; Forrest and Kopecky, 2005; Broeders et al., 2007). In this study, we have suggested empirical formulas including the new coefficients found by fitting two parameters for proton induced reactions at 24.8 and 28.5MeV energies. We have obtained new coefficients for the (p,na) reactions and we have compared with the available experimental data. 2. Empirical and semi-empirical systematics for the nucleon-induced reactions The evaluated nuclear cross-section data are required for understanding the binding energy systematic, nuclear structure, the properties of the excited nucleus states in different energy ranges and refined nuclear models (Handbook for Calculations of Nuclear Reaction Data, 1998; Forrest and Kopecky, 2005). And also these data are necessary to develop more nuclear reaction models in order to explain nuclear reaction mechanisms. The nuclear reaction mechanisms are frequently needed to provide the estimate of the particle-induced reaction cross-sections, espe- cially if the experimental data are not obtained or on which they are hopeless to measure the cross-sections; due to the experi- mental difficulty (Broeders et al., 2006a, 2007; Broeders and Konobeyev, 2007; Koning et al., 2004). The nuclear reaction systematics is widely used for the reaction cross-section evaluation supplementing result of mea- surements and calculations by theoretical models (Griffin, 1966; Blann and Vonach, 1983). A large number of empirical and semi- empirical cross-sections formulas with different parameters have been proposed by several authors in the literature (Ait-Tahar, 1987; Konobeyev and Korovin, 1995; Belgaid and Asghar, 1998; ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes 0969-8043/$ - see front matter & 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.apradiso.2008.11.001 Ã Corresponding author. Tel.: +90 312 2021250; fax: +90 312 212 22 79. E-mail address: eyuptel@gazi.edu.tr (E. Tel). Applied Radiation and Isotopes 67 (2009) 272–276