in Table \[tab:obsres\]. In the first two rows, the results obtained for the fine-structure line of $o$- detected previously by @hily2010nitrogen are reported. Our fitted $N$ and $T_{\ensuremath{\mathrm{ex}}}$ values compare very well with those obtained from the CLASS `HFS` method employed in that study. Our weighted average of the column density is $(5.4\pm 0.4)\times 10^{13}$cm$^{-2}$, which is consistent within the uncertainty with the value $(4.4\pm 0.7)\times 10^{13}$cm$^{-2}$ obtained previously. The excitation temperatures determined for the two components are $1\sigma$ coincident ($8.44\pm 0.12$K the average), and are also close to the ones obtained by @hily2010nitrogen (8.5K for the $J = \tfrac{3}{2} - \tfrac{1}{2}$ and 9.5K for $J = \tfrac{1}{2} - \tfrac{1}{2}$).

In the same spectral survey, we detect for the first time two groups of hyperfine transitions belonging to the singly-deuterated form of amidogen radical, . Figure \[fig:nhd\] shows the two fine-structure components of the fundamental $N_{Ka,Kc} = 1_{1,1} \leftarrow 0_{0,0}$ transition of , both observed in absorption around 770 and 776GHz in the 2b HIFI band.

![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:* $J = \tfrac{1}{2} - \tfrac{1}{2}$ 