Radiation Physics and Chemistry 73 (2005) 189–195 K X-ray production by 12 C 4+ ion impact on selected elements O.G. de Lucio, J. Miranda à , L. Rodrı´guez-Ferna´ndez Instituto de Fı´sica, Universidad Nacional Auto´noma de Me´xico, Apartado Postal 20-364, 01000 Me´xico, DF, Mexico Received 5 July 2004; received in revised form 7 January 2005; accepted 27 January 2005 Abstract Measurements of K-shell X-ray production cross sections by 12 C 4+ ions with energies between 6 and 9 MeV are presented. The target elements were Ti, Mn, Fe, Cu, Ga, Ge, Pd, Ag, and In. The measured cross sections are evaluated through comparisons with the ECPSSR model, the ECPSSR-UA theory, the MECPSSR model and the adiabatic perturbation (also known as direct molecular orbital) theory, using a scaling based on the reduced velocity parameter x R K : Consideration is given to multiple ionization effects and electron capture contribution to K-shell ionization. It is shown that the models are not suitable for predicting accurately the X-ray production cross sections in the whole measured x R K range. r 2005 Elsevier Ltd. All rights reserved. Keywords: Ionization cross sections; X-rays; Heavy ion impact 1. Introduction The phenomenon of characteristic X-ray emission, namely ionization followed by radiative relaxation filling an inner shell vacancy, produced by the impact of ions on atoms, has been known for several decades (Wo¨lfli, 1976). In particular, the production of K X-rays by heavy ions (such as 12 C or 16 O) was studied by several authors (Gray et al., 1976; Wheeler et al., 1976; Knaf et al., 1977; Zelazny and Hornshoj, 1984; Paul and Muhr, 1986; Geretschla¨ger and Benka, 1986; Geretschla¨ger et al., 1990; Geretschla¨ger et al., 1992; Fazinic et al., 1996; Tong et al., 1996; Sun et al., 1996; Mitra et al., 1997; Kubala-Kukus et al., 1999; Ozafra´n et al., 2003). Nevertheless, the development of theoretical models that describe and predict the X-ray production cross sections by heavy ion impact has not seen a strong advancement in the past 10 years, at least (Montenegro and Sigaud, 1985; Benka et al., 1987). Existing theories are focused on K lines rather than to L or M lines, while the symmetry in the collisions is an important factor within the models. Also, an overall evaluation of the experimental and theoretical predictions has not been carried out to date. There is a growing interest in the use of heavy ions for analysis with particle induced X-ray emission (PIXE), as they show larger X-ray yields, thus improving PIXE sensitivity (Ozafra´n et al., 1993; Ozafra´n et al., 1995). These works have shown that a reliable knowledge of the ionization cross sections by heavy ion impact is necessary to obtain accurate results in quantitative analyses. The ECPSSR theory of Brandt and Lapicki (1981) isa very successful model in describing the ionization by light ions, such as protons (Lapicki, 2002). This theory is a modification of the Plane Wave Born Approximation (PWBA). It considers effects such as the ion energy loss after the collision (E), the Coulomb deflection in the ion trajectory (C), the modification of the atomic electron energy states through a perturbed stationary states model (PSS), and an adjustment in the mass of the ARTICLE IN PRESS www.elsevier.com/locate/radphyschem 0969-806X/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2005.01.004 à Corresponding author. Tel.: +525556225073; fax: +525556225009. E-mail address: miranda@fisica.unam.mx (J. Miranda).