5577.339 Å oxygen line and subtraction of C₂ lines from the spectra of comet R1 Lovejoy. The black spectrum corresponds to the data not corrected for C₂, the green spectrum shows the data after decontamination by the C₂ lines. The red dotted line represents the C₂ synthetic spectrum. The positions of the C₂ lines at 5577.331 Å, 5577.401 Å and 5577.541 Å are indicated with small vertical tick marks. The bright line that appears at ~5576.7 Å is the telluric oxygen line Doppler-shifted by the geocentric velocity (all the wavelengths were shifted so that the cometary emission lines were in a common rest frame). This is the last spectrum obtained on 24 December; it corresponds to a geocentric velocity of 33.41 km s^-1.