Results of 216 GHz observations towards NGC 4418. (a) The velocity-integrated line-emission maps of 2_2, 0 − 2_1, 1. Black contours: −100 km s⁻¹ to 100 km s⁻¹ (3, 9, and 27σ, where σ_core = 6.7 × 10⁻² Jy beam⁻¹ km s⁻¹); blue: −120 km s⁻¹ to −100 km s⁻¹; red: 100 km s⁻¹ to 200 km s⁻¹ (3, 4, and 6σ, where σ_red = 4.2 × 10⁻² Jy beam⁻¹ km s⁻¹ and σ_blue = 1.9 × 10⁻² Jy beam⁻¹ km s⁻¹, respectively). The lines and symbol conventions are the same as in Fig. 5. (b) The continuum emission at 216 GHz shown in greyscale and by contours (3, 9, 27, and 81σ, where σ_cont = 6.4 × 10⁻⁴ Jy beam⁻¹). (c) Spectrum in the unit of the flux density within the emitting region (over 3σ in moment-0 image) against the line-velocity offset at the systemic velocity. The black histogram shows the observation result. The red dotted line indicates the 1σ rms level. The black dashed line shows a narrow line component, the dotted line shows a broad line component, the dash-dotted line represents other species (possibly 13CN line), and the solid line shows the three components combined. (d) Spectrum in units of the mean brightness at the peak intensity pixel against the line velocity.