Four fine structure energy level transitions in neutral scandium 3d²4s–3d4s4p. The observed spectra of GCIRS 22 are in the top panel. Bottom panel: Model spectra showing the sensitivity of the scandium lines to variations in carbon and nitrogen abundances. This shows that the scandium lines are not affected by blending of CN molecular line features. The sensitivity analysis was based on a model using an effective temperature of 3600 K and solar abundances. We have included a model using an effective temperature of 4500 K to illustrate the temperature sensitivity of the scandium lines, as the lines almost vanish at this temperature due to ionisation.