Lines of CH₃COCH₃ observed in TMC-1 shown from bottom to top in order of increasing frequency (see Table 1). The panels in green show the lines that are well detected, while those in red show lines that are not clearly detected due to a variety of reasons (see the text and caption in Table 1). The position of a negative frequency-switching artifact is indicated with a dashed vertical line and labeled as “fsw (-)”. The solid green and red lines correspond to the calculated spectra for Ν = 1.4 × 10¹¹ cm⁻², T_rot = 6.0 K, FWHM = 0.90 km s⁻¹, and θ_S = 80″.