Observed transitions of CH₃C₅N in TMC-1. The right component corresponds to K = 0 transitions and the left component to K = 1 transitions. The abscissa corresponds to the rest frequency of the lines. Frequencies and intensities for the observed lines are given in Table A.1. The ordinate is the antenna temperature, corrected for atmospheric and telescope losses, in milli Kelvin. The quantum numbers of each transition are indicated in the corresponding panel. The red line shows the computed synthetic spectrum for this species for T_rot = 9 K and a column density of 9.5 × 10¹⁰ cm⁻². The green lines show the computed synthetic spectrum adopting T_rot = 4 K and N=7.4 × 10¹¹ cm⁻²(Snyder et al. 2006). Blanked channels correspond to negative features produced when folding the frequency-switched data.