Selected transitions of HCCCH₂CCH in TMC-1. The abscissa corresponds to the rest frequency of the lines. Frequencies and intensities for all observed lines are given in Table 1. The ordinate is the antenna temperature, corrected for atmospheric and telescope losses, in millikelvins. The quantum numbers of each transition are indicated in the corresponding panel. The red line shows the computed synthetic spectra for this species for T_rot = 9.5 ± 0.5 K and a column density of (5.0 ± 0.5)×10¹² cm⁻² (see the main text). Blanked channels correspond to negative features produced when folding the frequency-switched data. Green labels indicate the transitions for which only one of the frequency-switching data points has been used (FS10 corresponds to a throw of 10 MHz). The three panels at the bottom show the average of all K_a = 0, 1, and 2 transitions. The noise level is below 0.1 mK for these stacked spectra. CH₂CDCN is reported in the 6₁₆ − 5₀₅ transition panel. A detailed analysis of the isotopologues of CH₂CHCN will be presented elsewhere (Cernicharo et al., in prep.).