Subset of the observed lines of o-C₆H₄ in the 31−50 GHz frequency range towards TMC-1 (see Table A.1 for the complete list of detected benzyne lines). 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 corrected for atmospheric and telescope losses, in mK. The red line shows the synthetic spectrum obtained from a fit to the observed line profiles, which provides T_r = 7 ± 1 K and N(o-C₆H₄) = (5.0 ± 1.0) × 10¹¹ cm⁻². The rotational quantum numbers are indicated in each panel. Blanked channels correspond to negative features produced in the folding of the frequency switching data. Cyan numbers indicate the multiplicative factor applied to the best model, when needed, to match the observations.