Top: cumulative distribution function of computed integrated intensities for C₃N in the optically thin LTE regime with T_ex = 10 K, and normalized to the intensity of the brightest line. Only 10% of all the 1, 2 and 3 mm lines have intensities brighter than a fifth of the brightest line. The transitions are color coded by bands, black: 3mm, orange: 2 mm, blue: 1 mm. Bottom C₃N spectra resulting from the stacking of 38 individual lines at 3 mm. The stacked spectra are shown both for the PDR and dense core positions. The red curve is a gaussian fit to the stacked spectra, the green lines are ± 3σ levels.