Bandhead wavelengths of ¹²C¹⁶O states and bands studied in this work. We also include the previously used numerical index notation (34–43) (Letzelter et al. 1987; Eidelsberg & Rostas 1990, etc.). Atomic line calibrators are indicated with |: for primary lines at high accuracy (1 fm or better) and with |: for secondary lines at medium accuracy (0.1 pm) (for the latter, mostly Xe I and a few Ar I and Kr I, see the NIST atomic line tables for identification), and the 1/e undulator bandwidth are shown as well.