Total L-shell X-ray production cross sections by 400±700 keV proton impact for elements with 34 R Z R 53 J. Miranda a, *, R. Ledesma b , O.G. de Lucio a a Instituto de Fi  sica, Universidad Nacional Auto Ânoma de Me Âxico, Apartado Postal 20-364, 01000 Me Âxico, DF, Mexico b Comisio Ân Nacional de Seguridad y Salvaguardias, Dr. Barraga Ân 40, 06720 Me Âxico, DF, Mexico Accepted 28 February 2000 Abstract Total L-shell X-ray production cross sections induced by protons with energies between 400 and 700 keV were measured for elements with atomic number Z between 34 and 53. The ECPSSR theory describes appropriately the results. This model modi®es the plane wave born approximation by considering projectile energy loss (E), Coulomb de¯ection of the incoming ion (C), polarization and change in electron binding energies through a perturbed stationary states method (PSS) and relativistic values of target electron mass (R). A comparison is given with previously published data for proton energies below 1 MeV and 26 R Z R 53, based on a scaling obtained from a reduced velocity parameter x R L : The results show that the scaling for these atomic numbers and energy ranges is adequate and a semi-empirical expression to calculate those cross sections is proposed. 7 2001 Elsevier Science Ltd. All rights reserved. Keywords: X-ray production cross sections; Ion±atom collision; PIXE 1. Introduction The interaction of ions with atoms results in the emission of characteristic X-rays from the target atom. Of particular interest is the case when the incoming ion is a proton, since this approach provides the basis for a very powerful analytical technique, proton induced X-ray emission (PIXE) (Johansson and Camp- bell, 1988). The applications of this include materials science, geology, biology, and archaeology. Although the X-ray emission takes place regardless of the ion mass, the best analytical results are obtained with pro- ton beams having energies between 2 and 3 MeV. Nevertheless, there are a number of laboratories throughout the world which can only produce proton beams with energies below 1 MeV. It has been explained (Rickards et al., 1990; Miranda, 1996) that the use of these energies has certain advantages, es- pecially when analyzing light elements (such as Si, S, Cl, K, and Ca), because the bremsstrahlung back- ground in the spectra is much lower within this proton energy range. Moreover, when certain medium-mass el- ements are present in the sample (e.g., Se, Zr, Cd), interference of the L X-rays from these elements occurs with the K X-rays emitted by the light elements, and sometimes the same happens with the M lines of the heaviest elements (like Au or Pb). Thus, it is necessary to know accurately the dependence of the X-ray pro- Applied Radiation and Isotopes 54 (2001) 455±459 0969-8043/01/$ - see front matter 7 2001 Elsevier Science Ltd. All rights reserved. PII: S0969-8043(00)00267-0 www.elsevier.com/locate/apradiso * Corresponding author. Tel.: +52-5-622-5073; fax: +52-5- 622-5009. E-mail address: miranda@fenix.i®sicacu.unam.mx (J. Mir- anda).