Λ-doubling lines observed towards R Dor that were used in the population diagram shown in Fig. 1. The spectra are given in rest frequencies using the υ_LSR of R Dor of 8.5 km s⁻¹ (see text). The vertical dotted orange lines show the predicted line frequencies from the JPL catalogue. The aperture used was twice the size of the band 7 beam. Other lines can be seen in the displayed spectra, which we identified as follows: top panel, the J_Ka, Kc = 27_3, 25 − 26_4, 22 SO₂ line (rest frequency: 107.060 GHz); and middle panel, v, J_Ka, Kc = v₁, 7_4, 3 − 2v₂, 8_5, 4 H₂O line (tentative identification, rest frequency: 252.172 GHz).