K-shell x-ray of Al produced by collisions of ions with near Bohr velocities

Abstract

X-ray emissionproduced by highly charged ions with the energy range near the Bohr velocity involves complicated atomic process. However, duo to the limitation of experimental conditions, the relevant researches are nearly absent. It is unclear whether the existing theory is applicable in such an energy range. This needs further exploring. In the present work, K X-ray spectra of Al excited by H⁺, He²⁺ and highly charged heavy ions I²²⁺ and Xe²⁰⁺ are investigated by using an Si drift X-ray detector in the energy range near the Bohr velocity. The X-ray production cross sections are extracted from the X-ray counts and compared with the theoretical simulations from PWBA, ECPSSR and modified BEA model. It is indicated that the cross section increases with the augment of projectile energy. With the same incident energy per nucleon, the cross section induced by highly charged heavy ions is a factor of about 10⁴ larger than that by light ions . With the impact of H⁺ and He²⁺ ions, the K-shell electrons are mainly knocked off through the direct Coulomb ionization, and the X-ray emission cross section can be well predicted by ECPSSR theory. For the bombardment of highly charged heavy ions I²²⁺ and Xe²⁰⁺, except for the Coulomb ionization, the orbital electrons can also be excited by electron capture. The BEA simulation after being modified by both Coulomb repulsion and effective charge can well predict the x-ray production cross section.