Observed spectra of TMC-1 around the 2_0,2–1_0,1 and 5_0,5–4_0,4 rotational transitions of ortho CH₂CCH. The spectrum at 37.5 GHz is taken with the Yebes 40 m telescope (black histogram in the bottom panel), and that at 93.6 GHz is taken with the IRAM 30 m telescope (black histogram in the top panel). Transition quantum numbers, frequencies, and derived line parameters are given in Table 1. The synthetic spectra (red lines) were computed for a column density of ortho CH₂CCH of 7.5 × 10¹³ cm⁻², a rotational temperature of 9.9 K, an emission size of 40″ in radius, and a linewidth of 0.72 km s⁻¹ for the 2_0,2–1_0,1 lines and of 0.57 km s⁻¹ for the 5_0,5–4_0,4 lines (see text).