Measured absolute SEC (a) and DEC (b) cross sections for C⁴⁺+He collisions. (a) SEC experimental data: present work (black squares); Crandall et al. (1976; purple circles); and Dijkkamp et al. (1985; blue triangles). Theoretical predictions: Gao et al. (2017; solid red line); and Kimura et al. (1984; dashed blue line). (b) DEC experimental data: present work (black squares); and Crandall et al. (1976; blue circles). Theoretical predictions: Gao et al. (2017; solid red line).