A POLYNOMIAL CURVE FOR IONIZATION CROSS-SECTIONS OF THE ATOMIC K-SHELL INDUCED BY PROTONS AND HEAVIER IONS

By the use of suitable variables in the axes, researchers have intende d to construct a ''universal'' curve for the ionization cross section of any atomic element at any particle energy, to be in agreement with the models Plane-Wave Born Approximation (PWBA) and Binary Encounter A pproximation (BEA). A fifth-order polynomial was used as the function to describe the universal curve. This is a semi-empirical function (us ing the same variables involved in PWBA and BEA) which fitted very wel l to the experimental data available when it was proposed. In this wor k the fifth-order polynomial has been used to fit the new experimental data on K-shell ionization cross section for protons. A good fit was found for a wide range of values. Results of the fits are compared wit h earlier curves. Experimental data with deuterons, alpha particles an d heavier ions have been included in the fitting. To determine the cro ss sections of particles other than protons, a scaling law derived fro m the PWBA and BEA models was used. The sources of the deviations of t hese data with respect to the proton data are discussed. The usefulnes s of this fitting curve and its range of application in quantitative f luorescence analysis is also discussed. (C) 1998 Elsevier Science B.V.