X-ray spectra following charge-exchange collisions between C${}^{6+}$ and He are presented for collision energies between 460 and 32 000 eV/u. Spectra were obtained at the Oak Ridge National Laboratory Multicharged Ion Research Facility using a microcalorimeter x-ray detector capable of fully resolving the C vi Lyman series lines through Ly-$\gamma$. These line ratios are sensitive to the initial electron $\ell$ distribution and test our understanding of the charge-exchange process. In addition, these line ratios are important for identifying charge exchange in astrophysical contexts involving the interaction of solar wind ions with neutrals. Our measurements are performed at collision velocities (300–2500 km/s) which overlap most of the solar wind range. Additional data of this type can be combined with computations to provide an extensive set of reliable line ratios and absolute cross sections for the interpretation of a variety of astrophysical situations.

• Received 12 July 2013

DOI:https://doi.org/10.1103/PhysRevA.88.052702