1₁₁ − 1₀₁ spectra of pNH₂D observed with ALMA along two orthogonal strips across L1544. The data are from Caselli et al. (2022). (a): Integrated line intensity map. The positions where the spectra are extracted are indicated with numbered circles. The synthesised beam is shown in the bottom left. (b): Six spectra along the minor axis of the core (from the centre to the south-west). The number in the top left of each panel refers to the circled numbers on the map. The positions are separated by 2″. (c): Same as panel (b) but along the major axis of the core (from the centre to the north-west). The spectra predicted from the model described in Sect. 6 are shown in red. Unlike the integrated intensity map of panel (a), the observed spectra in panels (b) and (c) have been corrected for the primary beam response.