Electron capture by and electron excitation of two-electron fluorine ions incident on helium

It is demonstrated that the total F K x-ray production cross section for F⁷⁺ + He collisions comes predominantly from three types of processes. These processes are $1s$-electron excitation of the 1s²¹S ground state of F⁷⁺, $2s$ electron excitation of the 1s2s³S metastable state of F⁷⁺, and nl electron capture by the 1s2s³S metastable state of F⁷⁺. All three of these processes have one thing in common, namely, they result in F K x rays. By using a high-resolution x-ray spectrometer, the cross sections for the three processes are measured separately as a function of projectile energy in the range of 6 to 40 MeV. The assignment of the three different processes of $1s$ electron excitation, $2s$ electron excitation, and nl electron capture is corroborated by comparing the measured energy dependences of the various K x-ray transitions with theory and other experimental measurements with F⁸⁺ and F⁹⁺ beams.