Series of l-C₃H⁺ lines detected in the Orion Bar PDR. Spectra of the J = 4 → 3, 5 → 4, 9 → 8, 10 → 9, 11 → 10, 12 → 11, and 13 → 12 rotational transitions of l-C₃H⁺ observed at 200 kHz spectral resolution, and 6 → 5 and 7 → 6 observed at 2 MHz (black histogram spectra). A LTE model is overlaid in red (see Sect. 5.2). The dashed lines indicate the LSR velocity (10.7 km s^-1) of the Orion Bar PDR.