Charge exchange spectroscopy is carried out in collisions of He-like ${\mathrm{C}}^{4+}$, ${\mathrm{N}}^{5+}$, and ${\mathrm{O}}^{6+}$ ions with He at a collision energy of approximately 5 keV/u, and emissions from ${\mathrm{He}}^{+}$ are observed in the extreme ultraviolet and visible spectral regions. We report emission cross sections for transfer excitation (TE) of ${\mathrm{He}}^{+}$ in these collision systems and discuss the angular momentum distribution among the population of excited ${\mathrm{He}}^{+}$ states. The optical sensitivity is calibrated by comparing the theoretically calculated emission intensities with the measured spectra. The pattern of observed and unobserved transitions indicates that TE preferentially populates high angular momentum states in ${\mathrm{He}}^{+}$. Furthermore, analysis based on the potential curve-crossing model suggests that single-electron capture plays a more significant role in TE than double-electron capture.

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• Atomic & molecular collisions
• Electronic excitation & ionization
• Optical spectroscopy