Kx-ray emission from 20- to 36-MeV fluorine projectiles following electron capture to excited states

The projectile $K$ x-ray emission cross sections for fluorine ions were measured under single collision conditions for charge states ranging from +4 to +9 in a thin argon target. The dependence of these cross sections upon the energy and the initial charge state of the projectile was determined for fluorine ions with energies between 20 and 36 MeV. Over the entire energy range, the $K$ x-ray—production cross section for ${\mathrm{F}}^{+9\mathrm{}}$ ions was about 70% of the total electron-capture cross section determined in a separate experiment. The $K$ x-ray—production cross section for these fully stripped ions is attributed to electron capture to excited states of the projectile. Calculations of electron-capture cross sections within the Brinkman-Kramers approximation for these heavy-ion collisions are consistent with the observation of large cross sections for capture to excited states.