Single- and double-electron-capture collision of C^q+ (q=3,4) with CO at keV energies

Absolute total single- and double-electron-capture cross sections for C^q+ (q=3,4) with CO have been measured at ∼0.5 keV∕amu using a reflection-time-of-flight mass spectrometer with a laser ablation ion source. The single- and double-electron-capture cross sections for C³⁺ with CO at 423±48 eV∕amu are found to be (0.96±0.12)×10⁻¹⁵ cm² and (0.99±0.13)×10⁻¹⁵ cm², respectively. The single- and double-electron-capture cross sections for C⁴⁺ with CO at 565±65 eV∕amu are measured to be (3.16±0.42)×10⁻¹⁵ cm² and (1.05±0.21)×10⁻¹⁵ cm², respectively. This suggests that double capture should not be ignored in modeling the emission from cascading processes in comet atmosphere.