Absolute Extreme Ultraviolet emission cross-sections have been measured for collisions between C 5 + and H 2 O in the range of 0.113 to 3.75 keV/amu (170–979 km/s). These results are used to derive velocity-dependent triplet-to-singlet ratios and emission cross-sections of the Cv K-series following single-electron capture. Comparison with existing measurements of integral charge-changing cross-sections indicates that auto-ionizing multi-electron capture is a significant reactions channel. This reaction may indirectly populate the n = 2 states and thus add strength to the K α emission of Cv ions thereby co-determining the hardness ratio of K-series emission of Cv.