Some of the cyclopentindene lines observed in TMC-1 with QUIJOTE. The black line represents the survey data, while the red line represents the synthetic spectrum calculated for a column density of 6 × 10¹² cm⁻². The green labels indicate the transitions for which only the 8 MHz frequency-switching data were used. The blanked channels correspond to negative features resulting in the folding of the frequency-switched spectra. Each box shows four collapsed transitions corresponding to each line, where α, β, γ, δ, and ϵ are K_a = 0, 1, K_a = 1, 2, K_a = 2, 3, K_a = 3, 4, and K_a = 4, 5, respectively (see Table B.1 for more details about transitions). The unidentified lines or other molecules already detected in the source appear in blue. The abscissa corresponds to the rest frequency assuming a local standard of rest velocity of 5.83 km s⁻¹. The ordinate is the antenna temperature in millikelvin.