Determination of the hyperfine structure of HN/C-13/ and HNC

The hyperfine structure of HN(C-13) and new frequencies for both HN(C-13) and HNC are determined from resolved spectra in two dark clouds. A quadrupole coupling constant of 0.28 + or - 0.03 MHz has been derived from the data. The new value differs from an earlier published value. Previous confusion is due to alteration of line shapes for these two dark clouds by absorption in low-excitation foreground material.