Determination of the α-induced K-shell ionization cross sections from the measured intensity ratios of K x-rays to (2 + → 0 +) γ-rays in even deformed nuclei

Abstract

It is proposed to use intensities of the 2 + → 0 + γ-rays, following inelastic scattering to first 2 + excited states in even deformed nuclei, for normalization of cross sections of other nuclear and atomic processes induced by energetic ions. It is argued that the modern coupled channels calculations permit high accuracy in predicting the 2 + total excitation cross sections, σ(2 +), over a wide bombarding energy range, provided that the corresponding B(E2) values are known accurately from elsewhere. The technique is applied to determine the K shell ionization cross sections for 158,160Gd targets bombarded with α-particles in the 13–30 MeV range. The K X-ray to 2 2+ → 0 + γ-ray intensity ratios are measured accurately using high energy resolution Ge detectors. The σ(2 +) values are calculated using the coupled channels code ECIS. Dependence of the results on the optical potential and the Coulomb potential as well as on the shape parametrization is studied and found to be small provided that a proper scaling procedure of the deformation parameters is applied. The deduced K shell ionization cross sections agree favourably with those calculated using the plane wave Born approximation with relativistic, binding and Coulomb corrections, but disagree with extrapolations of the existing experimental data.