component at *ca.* 776GHz. The filled gray histograms show the observed spectra, while the blue trace is our HFS fit. The red sticks represent the position of the HFS components assuming LTE intensities.[]{data-label="fig:nhd"}](nhd_1-0_15-05.pdf "fig:"){width="\hsize"} ![Spectra of the fine-components of the $N_{Ka,Kc} = 1_{1,1} \leftarrow 0_{0,0}$ transition observed towards IRAS 16293-2422. *Upper panel:* $J = \tfrac{3}{2} - \tfrac{1}{2}$ component at *ca.* 770GHz. *Lower panel:* $J = \tfrac{1}{2} - \tfrac{1}{2}$ component at *ca.* 776GHz. The filled gray histograms show the observed spectra, while the blue trace is our HFS fit. The red sticks represent the position of the HFS components assuming LTE intensities.[]{data-label="fig:nhd"}](nhd_1-0_05-05.pdf "fig:"){width="\hsize"}

![Spectra of the fine-structure components of the $N_{Ka,Kc} = 2_{1,2} \leftarrow 1_{0,1}$ $p$- transition observed towards IRAS 16293-2422. *Upper panel:* $J = \tfrac{5}{2} - \tfrac{3}{2}$ component at ca. 785GHz. *Lower panel:* $J = \tfrac{3}{2} - \tfrac{1}{2}$ component at ca. 787GHz. The filled grey histograms show the observed spectra, while the blue trace is our HFS fit. The red sticks represent the position of the HFS components assuming LTE intensities.[]{data-label="fig:nd2_21"}](nd2_2-1_25-15.pdf "fig:"){width="\hsize"} ![Spectra of the fine-structure components of the $N_{Ka,Kc} = 2_{1,2} \leftarrow 1_{0,1}$ $p$- transition observed towards IRAS 16293-2422. *Upper panel:* $J = \tfrac{5}{2} - \tfrac{3}{2}$ component at ca. 