Observed lines of C₆H₅CN in the 31-50 GHz frequency range towards TMC-1. 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 = 9 ± 0.5 K and N(C₆H₅CN) = (1.2 ± 0.1) × 10¹² cm⁻². The blue line shows the synthetic spectrum for a rotational temperature of 6 K and a column density of 1.5 × 10¹² 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. While the blue line produces a very good agreement with the observed intensities for K_a≤4, for higher values of K_a it underestimates the observed intensities by a factor of two.