Soft X-ray Line Emission Spectra from Highly-Charged Solar Wind Ions on Cometary Gases: N$^{5,6+}$ on CO

Laboratory measurements to benchmark space observations of x rays from comets approaching the sun were made using the highly- charged ion-beam facility at JPL and the UConn 1 m grazing- incidence CCD spectrometer. Beam-gas spectra are obtained from ions found in the solar wind on CO and other cometary gases. We compare our latest measurements of line emission in the range 2- 70 nm (~17-600 eV) for N$^{5,6+}$, near the fast solar wind velocity (~700 km/s), with previous measurements involving the isoelectronic ions O$^{6,7+}$. The highest n states excited on the projectiles by single electron charge transfer agree approximately with the Coulomb over-the-barrier model (e.g. for N$^{6+}$ on CO, primary excitation is mainly to n=4 and some to n=5 levels). The final l-dependences are also under study.