The HFS A and B constants are from the published values of Dembczyński et al. (1979) for the a   ⁶D_J levels, Handrich et al. (1969) for the levels, Blackwell-Whitehead et al. (2005b) for the a   ⁴D_J levels and Brodzinski et al. (1987) for the levels. Where the B constant is quoted as 0.0000 (–) the B constant was fixed at zero in the cited reference. The uncertainty in parentheses is taken from the aforementioned references.

The wavenumber and wavelength positions for the HFS transitions have been determined from energy levels reported in the NIST atomic Spectra Database (Ralchenko et al. 2009). The relative uncertainty in the wavenumber and wavelength of the HFS transitions is determined from the uncertainty in the HFS constants for the upper and lower fine structure levels, dσ_max = 0.001   cm^-1 and dλ_max = 0.002 Å. However, the wavenumber and wavelength in the table are given to four decimal places to adequately identify the hyperfine component lines.

The log (gf) for the HFS component lines is determined from the hyperfine splitting constants and log (gf) for the complete fine structure transition profile.