|${\mathrm{C}}_{3}$| experimental spectrum due to Martin-Drumel et al. (2023) with the transmittance compared to the transmittance computed (see the text) for their experimental conditions using our |$^{12}{\mathrm{C}}_{3}$| line list and plotted in the lower panel. The irregular spikes in both spectra correspond to local accidental coincidences of line positions. These responses are very sensitive to the accuracy of calculations as well as experimental resolutions and are very difficult to reproduce, which explains their appearance at different places.