Spectral data around the C₄ 3789 Å band (left) and the C₅ 5109 Å band, possibly from the system (right). Their lab spectra are shown at the bottom as reference (red). The sightlines are selected by their measured N(C₃) and the S/N of the wavelength region, which is indicated by the dashed blue lines. We cannot find the target transition in either individual sightlines nor their stacked spectrum. Upper limits on N(C₄) and N(C₅) can be estimated from their most prominent feature, and are around 10¹³ cm⁻² and 10¹² cm⁻², respectively.