  Experimental and theoretical state-selective X-ray spectra resulting from
single-electron capture in charge exchange (CX) collisions of Ne^10+ with He,
Ne, and Ar are presented for a collision velocity of 933 km s^-1 (4.54 keV
nucleon^-1), comparable to the highest velocity components of the fast solar
wind. The experimental spectra were obtained by detecting scattered
projectiles, target recoil ions, and X-rays in coincidence; with simultaneous
determination of the recoil ion momenta. Use and interpretation of these
spectra are free from the complications of non-coincident total X-ray
measurements that do not differentiate between the primary reaction channels.
The spectra offer the opportunity to test critically the ability of CX theories
to describe such interactions at the quantum orbital angular momentum level of
the final projectile ion. To this end, new classical trajectory Monte Carlo
calculations are compared here with the measurements. The current work
demonstrates that modeling of cometary, heliospheric, planetary, and laboratory
X-ray emission based on approximate state-selective CX models may result in
erroneous conclusions and deductions of relevant parameters.
